Silver square nanospirals mimic optical properties of U-shaped metamaterials.

We present a study of the optical properties of three-armed square nanospirals made of silver and realized as nanostructured thin films with Glancing Angle Deposition. Calculation of current flows in the nanospirals show excited resonant modes resembling those observed in U-shaped resonators. Four principal resonances were determined: near 200 THz and 480 THz for one polarization and 250 THz and 650 THz for the polarization orthogonal to the first one. In particular, a mode with anti-parallel current flow in opposite arms, associated with the observed resonance near 650 THz, indicates the existence of a magnetic-like resonance in the square nanospiral arrays. The robustness of the resonances against variations in the structural parameters of the nanospirals was investigated. This study revealed that the main parameter driving the position of the resonances was the overall dimension of the nanospiral, directly related to the length of their arms. Optical properties of a sample were measured by generalized spectroscopic ellipsometry at near-normal incidence, and evidence conversion between polarization states even for light polarized in the plane containing one of the arms in agreement with the numerical study. The measurements compared favorably to the results of the numerical simulations taking into account the disorder in the sample.

Making an omnidirectional reflector.

The effect of having a finite number of layers on the design of omnidirectional reflectors was investigated. It was shown that the structure should be finished with a low-index layer having a thickness larger than a quarter-wave to increase reflectivity, whereas layers below may remain of quarter-wave optical thickness at normal incidence angle. This general trend has been used for designing and realizing two a-Si-SiO(2) (amorphous silicon and silicon dioxide) omnidirectional reflectors in the near-infrared range on a silicon and a silica substrate, respectively. Owing to the decrease of absorption of recrystallized silicon as compared with a-Si in the visible range, the transmissivity of the structure realized on silica substrate was dramatically increased in the visible range upon annealing, whereas the high reflectivity and the omnidirectional effect were maintained in the near-infrared range.

Infrared ellipsometry investigation of SiO(x)N(y) thin films on silicon.

The dielectric function ˜ε (˜ε = ε(1) + iε(2)) of silicon oxynitride films deposited on silicon wafers by dual ion-beam sputtering is determined by infrared ellipsometry between 580 and 5000 cm(-1). The phase-separation model is unable to reproduce the experimental data. The dependence of ˜ε on stoichiometry is analyzed with the microscopic Si-centered tetrahedron model. The random-bonding model with five SiO(4-j)N(j) (j = 0-4) tetrahedra gives a good description of the spectra, provided the dielectric function of the mixed tetrahedra is carefully chosen.

Determination of refractive-index profiles by a combination of visible and infrared ellipsometry measurements.

Model inhomogeneous silicon oxynitride films were produced by ion-beam sputtering and characterized by ellipsometry in the visible and infrared ranges. These films exhibit strong intentional gradients of the refractive index that cannot be considered linear. A discrete description of the index profile with a few layers or a continuous description with a polynomial are examined; regressions by the use of measurements in the visible only or in the total spectral range (visible and infrared) are performed. Acquisition of data in an extended range is found to be a guarantee of the reliability of the calculated index profiles.

Synthesis of optical multilayer systems using genetic algorithms.

Stochastic algorithms are a promising method for the synthesis of optical multilayer systems. Amethod based on the use of genetic algorithms is described and applied to the design of three very different optical filters. Solutions found by genetic algorithms are refined, and results are compared with those of previous publications.

[Central venous catheters: a temporary access, sometimes temporarily prolonged or even permanent]. / Les cathéters veineux centraux: un abord temporaire, parfois temporairement prolongé voire permanent.

Out of the 427 patients regularly attended to at the Centre d'Hémodialyse du Languedoc Méditerranéen, 144 have required at one stage the use of internal jugular vein for hemodialysis. Subclavian or femoral cathethers have been resorted to temporarily pending the re-establishment of a pre-existing vascular access. Jugular catheters have been reserved for lasting utilizations thanks to Carnaud's technique using two catheters. Gradually the use of such catheters has become imperative to offer vascular access for the treatment of hemodialysis or to create truly "permanent" accesses. This second solution only concerns a limited number of patients either for their private convenience, or when the establishment of an internal access would require a heavy and uncertain operation.

[What is to be done in the absence of a superficial venous network compatible with the creation of an arteriovenous shunt?]. / Que faire en l'absence de réseau veineux superficiel compatible avec la création d'une FAV?

When the utilization of a simple arteriovenous fistula is out of the question, or no longer practicable, several alternative solutions have been advocated. Our own experience of surgery rests on 3000 vascular operations on dialysis patients since 1968. The solutions we have come to favour are saphenous vein homografts or heterografts with PTFE. The respective results seem to us equivalent so that either option can be held justified.

Estimate of the degree of inhomogeneity of the refractive index of dielectric films from spectroscopic ellipsometry.

Dielectric thin films often present microstructures that give rise to a variation of the refractive index with the distance from the substrate. We propose a method of analysis of ellipsometric data for homogeneous and slightly inhomogeneous films that are deposited on transparent substrates. Assuming a linear refractive-index gradient, we are able to determine not only the average index and the thickness but also the degree of inhomogeneity of the films by spectroscopic ellipsometry at variable angles of incidence. We apply this method to titanium dioxide films deposited on glass, which present different degrees of inhomogeneity depending on the preparation conditions.

Recombinant human erythropoietin: 18 months' experience in hemodialysis patients.

It has been shown that the regular administration of erythropoietin (EPO) permits the correction of anemia in end-stage renal failure patients. We analyzed the effect of chronic administration of EPO in 13 stable, regularly dialyzed end-stage renal failure patients over an 18-month period. The effects of EPO were evaluated according to standard criteria including clinical status, blood pressure control, hematology and biochemistry data, protein nutritional status, and dialysis efficiency. Following a 2-week control period, EPO was administered intravenously (IV) after the dialysis session according to a two-phase protocol. The first period (correction phase) consisted of a stepwise EPO dose increment, starting at 3 x 24 IU/kg/wk and doubling the dose every 14 days according to hemoglobin response in order to achieve a target hemoglobin level of approximately 11.0 g/dL (110 g/L). In the second period (maintenance phase) EPO dose was optimized to maintain the hemoglobin level between 100 and 110 g/L (10.0 and 11.0 g/dL), by adjusting either the unit dose or the frequency of injection. Anemia was corrected in all patients within 11 weeks, with EPO dose increasing from 72 to 360 IU/kg/wk. The stabilization of hemoglobin was achieved with an average EPO dose of 275 IU/kg/wk (50 to 476 IU/kg/wk). Concomitantly, a subjective and clinical improvement was noted in all patients. The dialysis efficacy remained in an acceptable range throughout the study, falling significantly (approximately 10%) through the first 3 months of treatment to stabilize at an effective urea clearance of approximately 120 L/wk. The dietary protein intake calculated from urea kinetic modeling ranged between 1.1 and 1.2 g/kg/d.(ABSTRACT TRUNCATED AT 250 WORDS)

[Recombinant human erythropoietin: 18 months of continuous use in substitution hemodialysis]. / Erythropoïétine humaine recombinante: 18 mois d'utilisation continue en hémodialyse de suppléance.

It has been shown that the regular administration of EPO permits the correction of anemia in end stage renal failure patients. We analyzed the effect of chronic administration of EPO in 13 stable, regularly-dialysed end stage renal failure patients over an 18 month period. The effects of EPO were evaluated according to standard criteria including clinical status, blood pressure control, hematology and biochemistry data, protein nutritional status and dialysis efficiency. Following a 2 week control period, EPO was administered intravenously after the dialysis session according to a 2 phase protocol. The first period (correction phase) consisted of a stepwise EPO dose increment, starting at 24 IU/kg x 3 times and doubling the dose every 14 days according to hemoglobin response in order to achieve a target hemoglobin level of 11 g/dl. In the second period (maintenance phase) EPO dose was optimized to maintain the hemoglobin level between 10 and 11 g/dl, by adjusting either the dose or the frequency of injection. Anemia was corrected in all patients within 10 weeks with EPO dose increasing from 72 to 360 IU/kg/week. The stabilisation of hemoglobin was achieved with an average EPO dose of 275 IU/kg/week (50 to 476 IU/kg/week). Concomitantly, a subjective and clinical improvement was noted in all patients. The dialysis efficacy, although remaining in an acceptable range, fell significantly by 10% over the first 3 months of treatment, remaining stable afterwards, yielding an effective urea clearance near to 120 1/week. The dietary protein intake calculated from urea kinetic modelling ranged between 1.1 and 1.2 g/kg/day.(ABSTRACT TRUNCATED AT 250 WORDS)

Erythropoietin-induced changes in protein nutrition: quantitative assessment by urea kinetic modeling analysis.

To evaluate objectively the effects of recombinant human erythropoietin (rHuEPO) administration on nutritional status in stable dialyzed patients, we used urea kinetic modeling (UKM) analysis and dietary protein intake evaluation by dietary assessment. Fifteen patients (9 females, 6 males; mean age 46.9 +/- 15.6 years) dialyzed for 9.4 +/- 6.3 years were studied longitudinally for 18 months, consisting of a control period (6 months) and an rHuEPO treatment period (12 months). Treatment modalities based on 3 weekly sessions were hemodialysis in 12 patients (6 cuprophane, 3 cellulose acetate and 3 highly permeable membranes), hemodiafiltration in 2 patients and postdilutional hemofiltration in 1 patient. Bicarbonate buffered dialysate was used in 9 patients and acetate in 6 patients. Urea kinetic modeling using a single-pool model was performed monthly over 1-3 cycles. rHuEPO was administered intravenously at the end of dialysis according to a two-phase protocol: (1) correction of anemia by stepwise increment of rHuEPO dose, and (2) maintenance dose to keep hemoglobin at 10-11 g/dl. rHuEPO administration corrected anemia in all patients, improving their general clinical condition. Dialysis efficacy was significantly reduced (15%) after the 3rd month of rHuEPO therapy. Clearnces were restored by increasing dialysis time and/or improving dialyzer performances, and adequacy of dialysis was maintained in all patients. During the 12 months of rHuEPO therapy, the protein catabolic rate remained stable at 1.2 g/kg/24 h in spite of an increase in appetite. At the same time, dry body weight increased significantly after 9 months, and the ratio dietary protein intake/protein catabolic rate a gross estimation of nitrogen balance, increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Double-blind, placebo-controlled study of nicergoline in the treatment of pruritus in patients receiving maintenance hemodialysis.

Pruritus is a common symptom among patients undergoing long-term hemodialysis. The effect of nicergoline, an ergoline, on pruritus was studied in products released during dialysis. In a first experiment series, 20 age-matched normal individuals, 25 patients receiving hemodialysis without pruritus, and 15 patients receiving hemodialysis with pruritus had intradermal tests with 500 micrograms of papaverine. All patients with pruritus had a small papaverine skin test response, and mean values were significantly (p less than 0.0001, Mann-Whitney U test) smaller in patients with pruritus. All patients with pruritus entered in a crossover, double-blind trial with nicergoline. In a first period of six dialyses, they received either nicergoline (daily oral dose, 30 mg, and intravenous dose during dialyses, 5 mg) or placebo. In the second period of six dialyses, patients received the crossover treatment. Nicergoline was effective in 13/15 patients, eight of these patients having a complete remission of pruritus. When nicergoline was stopped, patients relapsed within 24 to 48 hours. All patients who improved during the trial were then treated with a daily dose of 30 mg of nicergoline for 6 months. Seven patients had a complete remission, five had moderate symptoms, and one patient relapsed. This study demonstrated that some hemodialyzed patients with pruritus of unknown etiology had improvement with nicergoline.

Allergy in long-term hemodialysis. II. Allergic and atopic patterns of a population of patients undergoing long-term hemodialysis.

Maintenance hemodialysis is widely used throughout the world, and anaphylactic reactions appear to be increasing in number and severity. However, the exact incidence of sensitization and the role of atopy in these reactions are not yet fully understood. All of the 111 patients routinely dialyzed in a center were tested. All patients had a complete investigation of atopy, RAST to chemicals released during the procedure of dialysis (ethylene oxide (Eto), formaldehyde, phthalic anhydride, and toluene diisocyanate), skin tests with the effluent, and the titration of blood eosinophils. The incidence of atopy was found to be lower (13.5%) than in the normal population of the area. Skin tests with either histamine or allergens are significantly (p less than 0.001) smaller than those of nondialyzed subjects, and this method does not appear to be ideal in this population of patients. Eto sensitivity ranked first (5.5%), followed by phthalic anhydride sensitivity (3.6%); 5/6 patients who had a sensitivity to Eto and/or phthalic anhydride presented symptoms during dialysis, but they never were life threatening. Formaldehyde RAST was only found in one patient who had a life-threatening reaction. Finally, three patients presenting pruritus had positive skin prick tests with the effluent of the dialyzer. All patients having a first use syndrome and 80/81 symptom-free patients did not have serum-specific IgE against the released chemicals, 5/17 patients who had a pruritus during dialysis had either positive RAST to released chemicals or skin tests to the effluent, 5/8 patients who suffered from anaphylaxis had positive RAST to released chemicals, but only those who had a positive RAST presented a severe reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Allergy in chronic haemodialysis. 1. Double-blind intravenous challenge with formaldehyde.

Patients undergoing chronic haemodialysis are often exposed to formaldehyde formaldehyde (F) has been reported to cause IgE-mediated anaphylactic shock. Many other patients reported pruritus or anaphylaxis-like symptoms when dialysed with F-sterilized dialysers. Ten patients presenting such symptoms were compared with five control subjects. Intravenous double-blind challenges were performed on six consecutive occasions, with capillary flow dialysers sterilized with or without F. Dialysis was performed by an investigator who was not aware of the sterilization procedure. Among the ten F-sensitive patients, five had symptoms with F-sterilized dialysers and no symptoms with new dialysers, sterilized by ethylene oxide and free of F. Symptoms included pruritus and hypotension. These five patients were subsequently dialysed with new dialysers, not sterilized with F, and symptoms subsided. The five other patients had inconclusive challenges. The five control subjects had no symptoms during challenges. Skin-prick tests with F showed that only one of the five patients who had symptoms with F-dialysers had a strongly positive prick test. RAST to F was titrated with HSA-discs but it was negative in all patients and control subjects. Formaldehyde was shown to cause symptoms in some patients under chronic haemodialysis but an IgE-mediated mechanism was not demonstrated.

Anaphylactic shock caused by formaldehyde in a patient undergoing long-term hemodialysis.

Formaldehyde (F) elicits contact dermatitis and asthma in subjects who are exposed to this chemical when it is applied on the skin or inhaled. An immediate-type hypersensitivity reaction was never confirmed in these reactions. F is widely used in hemodialysis to sterilize adhesives, surgical devices, or reconditioned dialyzers. A 20-year-old woman who was subjected to hemodialysis for the past 4 years had a contact dermatitis to F. When hemodialysis was performed with a new dialyzer not sterilized with F, there were no symptoms. She had minor symptoms of anaphylaxis characterized by rhinitis, wheezing, and headache on the first use of a reconditioned dialyzer. Two days later, she was dialyzed with the same reconditioned dialyzer and developed within minutes a severe anaphylactic shock requiring resuscitation. The patient had no personal or family history of atopy. Prick tests and RAST to common food and inhlant allergens were negative. Prick tests performed with 0.1% and 1% F were positive in the patient, whereas they were negative in control subjects. RAST to F was performed with discs specially prepared and coated with human serum albumin. RAST was strongly positive. RAST to ethylene oxide was negative. A patch test with F was performed and induced an anaphylactic shock 26 hours after the skin application of F. The patient did not present any anaphylactic symptoms with the use of nonreconditioned dialyzers. An immediate-type allergy to F mediated by IgE may be envisaged in this patient.