Switchable self-assembly of Prussian blue analogs nano-tiles triggered by salt stimulus.

Prussian blue analogs (PBAs) are materials well known for their bulk physical and (electro)-chemical properties, with an outstanding selectivity for caesium in ion exchange processes. Crystalline nano-tiles, made of copper based PBA, are produced and dispersed in water by tuning their electrostatic interactions. The shape and size of the nano-crystals are determined by combining scattering, microscopic and spectral techniques. We show here that Cu-PBA nano-tiles form planar superstructures by an edge to edge self-assembly process controlled by specific cation effect and ionic strength. Sedimentation and (re-)dispersion of the nano-tiles are found to be fully reversible. This switchable anisotropic self-assembly triggered by salt stimulus makes PBA nanocrystals potentially interesting for applications.

Revealing organic carbon-nitrate linear relationship from UV spectra of freshwaters in agricultural environment.

A strong non linear relationship between nitrate and organic matter (assessed by dissolved organic carbon, DOC) has been recently demonstrated by Taylor and Townsend (2010), namely for freshwaters. In this context, our study explores this relation from the behavior of sets of normalized UV spectra (same area under each spectrum) of different water samples showing a hidden isosbestic point (HIP) around 225 nm. This HIP is linked to the existence of a simple relation between nitrate and DOC, the proportions of which vary according to the sampling location and environmental factors. In a second step, a simple linear model is proposed for nitrate-DOC relationship (α⋅NO3+ß⋅DOC=1) and a validation is proposed for more than 150 samples of different Brittany rivers and lakes. For samples of the largest watershed, a complementary exploitation from data acquired during the different campaigns confirmed the seasonal evolution between spring (high nitrate/low DOC) and autumn (high DOC/low nitrate). Further investigation on other freshwater samples is needed in order to improve the limits of this linear model.

Estimation of external contact loads using an inverse dynamics and optimization approach: general method and application to sit-to-stand maneuvers.

This paper presents a general method to estimate unmeasured external contact loads (ECLs) acting on a system whose kinematics and inertial properties are known. This method is dedicated to underdetermined problems, e.g. when the system has two or more unmeasured external contact wrenches. It is based on inverse dynamics and a quadratic optimization, and is therefore relatively simple, computationally cost effective and robust. Net joint loads (NJLs) are included as variables of the problem, and thus could be estimated in the same procedure as the ECL and be used within the cost function. The proposed method is tested on human sit-to-stand maneuvers performed holding a handle with one hand, i.e. asymmetrical movements with multiples external contacts. Three sets of measured and unmeasured contact load components and three cost functions are considered and simulated results are compared to experimental data. For the population and movement studied, better results are obtained for a least-square sharing between actuated degrees-of-freedom of the relative motor torques (motor torques normalized by the maximal torque production capacity). Moreover, the number of unknown ECL components does not significantly influence the results. In particular, measuring only the vertical force under the seat lead to a relatively correct estimation of the ECL and NJT: not only the values of R% were small (about 10% for the feet ECL and 20% for the NJT), but the influence of an experimental parameters (the Seat Height) was also correctly predicted.

Small-angle neutron scattering study of solubilization of tributyl phosphate in aqueous solutions of L64 Pluronic triblock copolymers.

We have studied the solubilization behavior of tributylphosphate (TBP) in aqueous solutions of L64-Pluronics, using light and small angle neutron scattering (SANS). Varying the temperature and the oil content, the system presents a nontrivial phase behavior. In particular, at 308 K, a first solubilization followed by an emulsification failure and a resolubilization is found. We have measured the microstructure by SANS and characterized the microemulsion droplet core size, corona thickness, polydispersity, and interactions. It is shown that at low oil content, the system is made of small swollen micelles. After the phase separation, the resolubilization is carried by larger oil droplets decorated by copolymer. From specific surface measurements at large angles, a surprising change in surfactant conformation is found to accompany this morphological evolution which is also supported by previous results obtained from ¹H NMR experiments. In independent measurements, our structural modeling is confirmed using contrast-variation SANS.

Micellar solubilization of tributylphosphate in aqueous solutions of Pluronic block copolymers. Part I. Effect of the copolymer structure and temperature on the phase behavior.

Solubilization of tributylphosphate (TBP), a polar oil, in various micellar solutions of Pluronic has been investigated by turbidimetry emphasizing the effect of temperature and the role of the PPO and PEO blocks on the phase behavior of the three components systems (Pluronic-TBP-water). [Temperature-composition] diagrams allow monophasic and diphasic domains to be delimited. Two temperatures are shown to have a determining effect on the phase behavior (TBP solubilization); the well known cloud point temperature (CPT, here defined for the three components system) and the solubilization minimum temperature (SMT) which is defined as the lowest temperature allowing solubilization of TBP in the system. Both temperature depend on the copolymer structure and, interestingly, are directly related to the TBP concentration in the medium. Monophasic microemulsions are observed when the temperature ranges between the SMT and the CPT. When TCPT the system separates in two phase due to the co-precipitation of TBP and Pluronic. Moreover an unexpected evolution of the CPT with the TBP content clearly indicates the occurrence of a structural change of the microemulsions which allows higher quantities of TBP to be solubilized. But the structural change does not allow alone higher quantities of TBP to be solubilized. A well compromise between the SMT and the CPT must be also observed so as to obtain a large extent of monophasic domain after the restructuration. The best compromise is obtained with Pluronics with intermediate hydrophobic character. Reversely, hydrophobic and hydrophilic Pluronics exhibit a very small extent of monophasic domain after the restructuration which does not allow benefit by the structural change.

Micellar solubilization of tributylphosphate in aqueous solutions of Pluronic block copolymers. Part II. Structural characterization inferred by 1H NMR.

The solubilization of tributylphosphate (TBP), a polar oil, in various micellar solutions of Pluronic has been investigated by (1)H NMR spectroscopy. Partial phase diagrams of the three components systems (Pluronic-TBP-water) have shown two characteristic temperatures, called CPT and SMT, which control the phase behavior (see Part I); Both temperature depend on the copolymer structure and, interestingly, are directly related to the TBP concentration in the medium. Monophasic microemulsions are observed only when the temperature ranges between the SMT and the CPT. Moreover, the evolution of the CPT with the TBP content clearly indicated the occurrence of a structural change of the microemulsions which allows higher quantities of TBP to be solubilized. In this second part, (1)H NMR studies of TPB/micellar systems have essentially focused on elucidating the nature of the interactions between TBP and micelle, or on the location of the solubilized species, mainly from the dependence of chemical shifts or linewidths on TBP concentration. Especially, the NMR spectra of the microemulsions before and after the structural change have been compared with those obtained for pure solution of Pluronic in D(2)O at different temperatures and in CDCl(3). The analysis of the (1)H NMR chemical shifts suggests a structural transformation of the TBP-Pluronic micelles in the sense of an hydrophobic TBP-PPO core becoming more and more dense as the TBP concentration increases. Especially, (1)H NMR data evidence an evolution of the hydration state of the hydrophobic core following addition of TBP in the micellar solutions. During the addition of TBP, the microemulsion structure turns from spherical swelled micelles to nanodroplets of pure TBP stabilized by the Pluronic (pure nanophase of TBP stabilized by the copolymer). It is shown that the structural change strongly depends on the temperatures (CPT and SMT, see Part I) and on the copolymer structure.

Tuberculosis I: a conceptual frame for the immunopathology of the disease.

An analysis of the cellular and humoral immune responses after bacille Calmette-Guerin (BCG) vaccination and during tuberculosis treatment favors the hypothesis of an immune defence developed in four overlapping successive stages. The initial immune response is innate. The following two intermingle innate and specific responses against low molecular weight oligopeptidic and nonpeptidic antigens, as muramyldipeptide and trehalose dimycolate, and large molecular weight nonpeptidic antigens such as lipoarabinomannan. The ultimate specific response is directed against protein antigens as Antigen 60. BCG and primary tuberculosis (TB) infections induce cellular and humoral immune responses essentially against oligopeptidic and small and large molecular weight nonpeptidic antigens. Immune responses against non-peptidic substances contribute to the immunoprotection of the infected person who develops a primary infection. Some infected people allow the expression of the immunosuppressive activity of the pathogen. This results in the synthesis of interleukin-10 (IL-10), which suppresses the formation of interferon-gamma (INF-gamma) and IL-2, and of IL-6, which suppresses T-cell responses. These patients have a skewed immune response against non-peptidic antigens and present with symptoms. They will not recover unless responses directed against proteinic antigens occur, which restore INF-gamma and IL-2 production. The formation of immumoglobulin-G (IgG)-type antibodies and of a cellular immunity against mycobacterial peptidic antigens is essential for a good protection against a post-primary infection.

Stapedius tendon reconstruction during stapedotomy: technique and results.

During surgery for otosclerosis, it is common for the surgeon to cut the stapedius tendon. Even without reconstruction of the tendon, the results of this kind of surgery are particularly satisfactory. The stapedial reflex is more important for improving intelligibility of speech in the presence of background noise than for protection against hazardous levels of noise. An intact stapedial reflex improves ones ability to follow speech in the presence of background noise. This report will present a technique to reconstruct the stapedius tendon, along with the results obtained when adding this procedure to stapedotomy surgery.

Argon laser and Gherini-Causse Endo-Otoprobe in otologic surgery.

The authors describe the various surgical indications and techniques of the argon laser and Gherini-Causse Endo-Otoprobe in otologic surgery, from otosclerosis to chronic otitis. The advantages are numerous, permitting the surgeon to vaporize or coagulate tissue with optimal effect, avoiding excessive mobilization of the ossicular chain and diminishing the risk of damage to the facial nerve and inner ear structures.

[Turner's syndrome and isoforms of LH and FSH. Value of polyclonal enzymatic techniques]. / Syndrome de Turner et isoformes de LH et FSH. Intérêt des techniques enzymatiques polyclonales.

BACKGROUND: The glycoproteic hormones, LH and FSH, circulate under heterogenous molecular forms, the isoforms. The more acidic isoforms of FSH are found in hypogonadic patients and a displacement towards the basic forms is observed during substitutive treatment. CASE REPORT: A 13 year-old girl with Turner syndrome was examined for pubertal delay. Ultrasonography failed to see both ovaries and endocrine investigations showed a type P1 response (LH-RH test using immunological method). Control of hormonal levels by a polyclonal immunoenzymatic method confirmed primary hypogonadism. CONCLUSIONS: Radioimmunological methods using monoclonal antibodies can underevaluate FSH and LH levels under circumstances in which the distribution of isoforms may vary. Discrepancy must lead to the measure of gonadotrophins using polyclonal immunoenzymatic methods.

Mycobacterial infections: are the observed enigmas and paradoxes explained by immunosuppression and immunodeficiency?

The enigmas and paradoxes observed in tuberculous patients, in Bacille Calmette-Guérin-vaccinated people and in Bacille Calmette-Guérin-treated cancer patients have been examined, in an attempt to explain them through the mechanisms of immunodeficiency and immunosuppression. A dual effect is postulated: an immunosuppression induced by the infecting mycobacteria that adds to a pre-existing or emerging state of immunodeficiency of the infected individual. The immunological cellular and humoral anergies observed at the beginning of a tuberculous therapy are usually lifted after the first two weeks of treatment. This restoration of immune responsiveness may be attributed to the destruction or to the growth inhibition of immunosuppressive mycobacteria. The observation that drugs cytocidal in vitro do not always sterilize the patients under treatment whereas bacteriostatic drugs do, may find an explanation in the dual immunosuppression induced by cytocidal drugs and mycobacteria. The fact that Bacille Calmette-Guérin applied as an immunotherapy to residual cancer has either a favorable or an unfavorable action may be due to the immunosuppressive activity attached to some Bacille Calmette-Guérin strains and to some cancers. The variable protective activity of Bacille Calmette-Guérin vaccines may be due to the immunological status of the vaccinated people and the compositional differences between strains. The protective activity of subunit vaccines in experimental models can be attributed to the elimination of immunosuppressive factors present in whole killed mycobacteria.

Poor vibration of inner ear fluids as a cause of low tone tinnitus.

Tinnitus due to otosclerosis may be caused by poor vibration of the inner ear fluids. The goal of this article is to suggest some explanations, to enhance future research work carried out by other authors on this important issue, and to show what are the results of surgery to relieve tinnitus in the author's experience. Only complete resolution of the tinnitus 1 year after surgery was taken into account in the assessment of the results.

Ossiculoplasty with composite prostheses. Overview and analysis.

Aeration of a mucosa-lined tympanic cavity is essential for a functioning middle ear. Extrusions of even the best-designed prostheses occur from abnormal middle ear conditions such as atelectasis, middle ear fibrosis, recurrent cholesteatoma, tympanic membrane perforation, and otitis media. Various polymers have been developed in an attempt to maximize prosthetic biocompatibility and ease of use while minimizing the chance of extrusion. One such polymer is a composite of hydroxyapatite and Silastic, known as Flex H/A. This material has been incorporated into two ossicular prostheses, the Universal Plus and the Causse Flex H/A prostheses. Certainly, refinements will continue to be made in the chemical makeup of the bioceramics in order to achieve optimal biocompatibility. In addition to biocompatibility, cost containment issues have influenced the development of ossicular prostheses. A universal prosthesis eliminates the need to stock multiple designs, thereby reducing the cost to institutions. One of the greatest challenges in the future will be to define the appropriate prosthetic design for optimal sound transmission. Consideration of prosthesis weight, head size, and footplate attachment are future research questions that need to be addressed in a scientific biologic model.

Impedance transfer: acoustic impedance of the annular ligament and stapedial tendon reconstruction in otosclerosis surgery.

The resistance rebuilt around the lower tip of the piston must be the same as that created by the annular ligament of the stapes footplate. Otherwise, the threshold at which an acoustic or barotrauma is able to damage the membranes and hair cells of the inner ear will be lowered. The elasticity reestablished around the lower tip of the piston plays a part in the quality and quantity of hearing for the low frequencies up to 3 kHz. To protect the ear against acoustic traumas, an attempt to rebuild the stapedial reflex is proposed.

Sodium fluoride therapy.

As a medical treatment for otospongiosis-otosclerosis, sodium fluoride influences the underlying bony changes in the labyrinth so as to arrest or prevent the onset of hearing loss. Sodium fluoride is an enzyme inhibitor and reduces osteoclastic bone resorption and, if the dosage is more than 60 mg a day, may rebuild pseudohaversian bone.

Surgical treatment of stapes fixation by fiberoptic argon laser stapedotomy with reconstruction of the annular ligament.

The goal of surgical treatment of stapes fixation is to restore the impedance transfer of the ossicular chain and the acoustic impedance of the annular ligament of the stapes footplate to achieve normal physiologic vibration of the inner ear fluids. Advances in instrumentation, particularly the introduction of fiberoptic laser handpieces and microdrills, have enabled surgeons to approach this goal in a more precise and delicate fashion. In this article, the authors review their surgical techniques, the biophysics involved, the physics of fiberoptic handpieces for the delivery of argon laser energy, and their results.

Fiberoptic argon laser stapedotomy: is it safe?

The history of otosclerosis surgery has been marked by major advances in both surgical technique and instrumentation. Fenestration, stapes mobilization, total stapedectomy, and stapedotomy were important advances in technique. Loupes, binocular microscopy, speculum holders, and microdrills similarly advanced instrumentation. What about fiberoptic argon laser handpieces for use in laser stapedotomy? Do they represent a significant advance in instrumentation, or are they merely another gimmick? Are fiberoptic argon laser handpieces safe? Experimentally, the thermal effects of argon laser, delivered via fiberoptic handpieces to a cadaver stapes and model vestibule, were studied. No significant temperature elevations within a model vestibule were observed during stapedotomy. There were significant temperature elevations within the laser plume at the level of the facial nerve. These findings are consistent with our experience in over 2200 primary and revision stapedotomies. To date, there have been no cases of significant hearing loss or permanent facial paralysis related to the use of these fiberoptic handpieces. We believe fiberoptic argon laser handpieces are as safe as conventional microsurgical instruments in stapes surgery.

Survival and evolution of vein grafts in otosclerosis surgery: structural and ultrastructural evidence.

The annular ligament of the stapes footplate measures 0.2 mm2 and contains elastic fibers that restrict perilymphatic movement to a molecular level. This resistance of the annular ligament prevents excessive movement of labyrinthine fluids that are potentially hazardous to the membranous and cellular structures of the inner ear. However, if the resistance of the annular ligament is overcome, then inner ear damage can occur. The vein graft, as used in our technique for otosclerosis surgery, occupies a space of 0.2 mm2 between the edge of the stapedotomy hole and the piston and has nearly the same compliance and resistance as the annular ligament of the stapes footplate. The vein graft becomes integrated with the middle-ear mucosa. It develops a rich and active blood supply and the smooth muscle cells and elastic fibers remain, although the latter show some modification of ultrastructural pattern. The graft becomes overlaid by the middle-ear epithelium. Even samples of vein graft that have been present for many years retain surviving elastic fibers, including those that have become fibrotic. In time, the number of elastic fibers increases as a result of the activity of fibroblasts, which build a poorly colored collagen.