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E Hernández

Publications and source records attributed to E Hernández.

At least 19 recordsLinked to original sources
PubMed2006

Tonic and phasic differential GABAergic inhibition of synaptic actions of joint afferents in the cat.

The aim of this study was to examine the functional organization of the spinal neuronal networks activated by myelinated afferent fibers in the posterior articular nerve (PAN) of the anesthetized cat. Particular attention was given to the tonic and phasic GABAa inhibitory modulation of these networks. Changes in the synaptic effectiveness of the joint afferents were inferred from changes in the intraspinal focal potentials produced by electrical stimulation of the PAN. We found that conditioning stimulation of cutaneous nerves (sural, superficial peroneus and saphenous) and of the nucleus raphe magnus often inhibited, in a differential manner, the early and late components of the intraspinal focal potentials produced by stimulation of low and high threshold myelinated PAN afferents, respectively. The degree of the inhibition depended on the strength of both the conditioning and test stimuli and on the segmental level of recording. Conditioning stimulation of group I muscle afferents was less effective, but marked depression of the early and late focal potentials was produced by stimuli exceeding 5 xT. The i.v. injection of 1-2.5 mg/kg of picrotoxin, a GABAa blocker, had relatively minor effects on the early components of the PAN focal potentials, but was able to induce a significant increase of the late components. It also reduced the inhibitory effects of cutaneous and joint nerve conditioning on PAN focal responses. Conditioning autogenetic stimulation with high-frequency trains depressed the PAN focal potentials. The late components of the PAN responses remained depressed several minutes after discontinuing the conditioning train, even after picrotoxin administration. The present observations indicate that the neuronal networks activated by the low threshold PAN afferents show a relatively small post-activation depression and appear to be subjected to a minor tonic inhibitory GABAa control. In contrast, the pathways activated by stimulation of high threshold myelinated afferents have a strong post-activation depression and are subjected to a significant tonic GABAergic modulation. These contrasting features, together with the phasic differential GABAergic inhibition of the responses produced by stimulation of the different populations of joint afferents, may contribute to the preservation of the original information on joint position transmitted by large diameter joint afferents, in contrast with the tonic presynaptic inhibition exerted on the fine myelinated joint afferents, which may be involved in the adjustment of compensatory reactions to inflammation.

Animals↗
PubMed2006

Pancreas preservation with the University of Wisconsin versus Celsior solutions.

INTRODUCTION: The use of Celsior solution for organ preservation has not been thoroughly studied in pancreas transplantation. The aim of this study was to compare University of Wisconsin and Celsior solutions for preservation of pancreas grafts. PATIENTS AND METHODS: From March 1995 to December 2005, 72 patients with type 1 diabetes underwent pancreas transplantation. There were 42 men and 30 women, with a mean age at transplantation of 38.1 +/- 7.5 years (range: 27 to 55 years), and a mean duration of diabetes of 22.5 +/- 6.6 years. Recipients were classified into two groups according to the preservation solution: (A) Celsior (n = 28, 38.9%) and (B) Wisconsin (n = 44, 61.1%). RESULTS: The donor and recipient characteristics were similar in both groups. There were five cases of venous thrombosis in the Wisconsin group and two in the Celsior group (P = NS). The venous drainage technique in the former group was portocaval in 19 patients and portoiliac in 25; in the Celsior group, portocaval in 23 patients and portoiliac in five (P = .001). Enteric drainage was used in 19 patients from the Celsior group and 17 patients from the Wisconsin group (P = .01). Actuarial 2-year graft survival was 74.6% in the Wisconsin group and 77.4% in the Celsior group (P = NS). CONCLUSIONS: No differences were observed in venous thrombosis between the two groups. The lower rate of venous thrombosis with the portocaval technique was related to the type of venous drainage rather than the type of preservation solution. Celsior solution may be considered as good as Wisconsin solution for pancreas transplantation.

Adenosine↗
PubMed2006

[Choledocal cyst: analysis of 29 cases and review or the literature].

UNLABELLED: The aim of the present study has been to systematize the clinical presentation of the entity named choledochal cyst, in relation with its probable etiopathology and the intraoperative findings as well as its evolution after surgery, based on the revision of the literature and of our experience in 29 cases. MATERIAL AND METHODS: 29 cases of cystic dilatation of the biliar duct extra and/or intrahepatic are analyzed. In 4 cases the diagnosis was prenatal and two were excluded of the study after it has been confirmed they suffered biliary atresia type I. In the left 27 cases, 19 variables are analyzed retrospectively, like age, sex, weight, symptoms, ultrasonographic images, etc. Subsequently, intra-operative cholangiographic findings were correlated with the clinic presentation and the evolution of the patients after surgery. RESULTS: Of the 27 cases analyzed 16 (59,25%) were cystic dilatations from which 14 had a neonatal or early clinic presentation (before 2 years), however the fusiform dilatations were presented later on. From the analyzed symptoms, in relation with the age only the pain and the jaundice showed significant differences, being the pain most frequent in later presentation ande the jaundice in the early form. The two cases of type 3 of Todani or choledochocele were of later presentation. An anomaly in the bilionpacreatric junction was detected in 15 patients; the majority had a later presentation, associated to pancreatitis in 4 cases. Primary cyst excision and biliary Roux-en-Y reconstruction was the treatment of election in the majority of cases. In 3 cases we used the appendix to replace the choledocus, but all three cases were reconverted two years later because of permanent elevation of ALT and GGT. CONCLUSIONS: In favour of the literature and of our experience nowadays it would be possible to systematize this malformation and make a division in two groups, depending on the cholangiographic findings and clinical presentation: 1. Cystic dilatations with a clinical neonatal presentation or beneath 2 years. 2. Fusiform dilatations with a later clinical predominance and associated frequently to pancreatitis and anomalous pancreatobiliary junction. Choledochocele is an entity that must be considered not only for its etiology but for its clinical presentation and treatment. Primary cyst excision and biliary Roux-en-Y reconstruction is the treatment of election. Regular long-term review of these patients is mandatory in the surveillance of sub-clinic cholangitis and the risk of possible long-term malignance of this entity.

Choledochal Cyst↗
PubMed2005

The impact of the summer 2003 heat wave in Iberia: how should we measure it?

We present a new approach to improve the reliability of quantifying the impact of a heat wave on mortality rates. We show, for the recent European summer 2003 heat wave, that the use of absolute maximum temperature values, or number of days above a given threshold, can be misleading. Here, we have assessed the impact of the heat wave on Iberian mortality by applying a four step procedure: (1) calculating, for each observatory, the local maximum temperature (T (max)) distributions, (2) calculating the corresponding 95th percentile values (T (threshold)), (3) locally defining extremely hot days (EHD) as those days on which the local threshold of the 95th percentile of the series is exceeded, and (4) calculating the total degrees-days (DD) of exceedance, by calculating the difference T (max)-T (threshold) and summing these values for all days above T (threshold). We show that the relationship between summer mortality rates and the DD index is non-linear and can be described by a logarithmic function, with a correlation coefficient of 0.78, which explains 60.6% of the mortality variance (F value of 24.64, significant at P<0.0001). Using maximum temperatures, no significant relationship is found with mortality, whereas the EHD frequency shows a significant association with mortality, albeit weaker than that obtained with DD.

Hot Temperature↗
PubMed2005

Energy eigenvalue surfaces close to a degeneracy of unbound states: crossings and anticrossings of energies and widths.

The rich phenomenology of crossings and anticrossings of energies and widths, as well as the sudden change in shape of the S(E)-matrix pole trajectories, observed in an isolated doublet of resonances when one control parameter is varied, is fully explained in terms of sections of the energy eigenvalue surfaces in parameter space close to a degeneracy point.

Journal Article↗
PubMed2005

Safety assessment of the conversion from mycophenolate mofetil to enteric-coated mycophenolate sodium in stable renal transplant recipients.

The immunosuppressant mycophenolate mofetil (MMF; CellCept) has greatly improved transplant recipients' clinical outcomes, but its efficacy may be limited by dose adjustments due to adverse events (AEs). An enteric-coated formulation of mycophenolate sodium (EC-MPS; myfortic), designed to improve gastrointestinal tolerability is now available. This Latin-American, prospective, multicenter, open-label, 6-month trial assessed the safety and tolerability of converting renal transplant recipients from MMF to EC-MPS. In total, 237 renal transplant recipients (stable > or = 3 months' posttransplant) receiving MMF (< or =1000 mg b.i.d.) were enrolled. Adults (n = 218) were converted to EC-MPS 720 mg b.i.d. (equimolar to MMF 1000 mg b.i.d.) even if they were initially receiving <1000 mg MMF b.i.d. (ie, 47 adults received a higher than equimolar dose of EC-MPS). Children (n = 19) were converted to EC-MPS 450 or 432 mg/m2 b.i.d. Patients also received cyclosporine microemulsion (Neoral) and corticosteroids. There were three acute rejections and no graft failures. The incidence of AEs was 59.9% (in those receiving a higher than equimolar EC-MPS dose it was 57.4%). In all, 22% of patients had gastrointestinal AEs, 37% had infections, and 4.8% had hematological AEs. Only 24 patients (10%) had an AE-related dose reduction. Seven of these patients had received higher than equimolar doses of EC-MPS. Patients can be safely converted from different doses of MMF to a standard dose of EC-MPS. The requirement for EC-MPS dose reduction to manage AEs was relatively low. Use of EC-MPS is a valid alternative for renal transplant recipients receiving maintenance MMF treatment.

Adolescent↗
PubMed2005

Rapamycin at six years can exhibit normal renal function without proteinuria or neoplasia after renal transplantation. A single-center experience.

Currently, long-term experience with Rapamune (RAPA) after renal transplantation is scarce. We present our experience with RAPA in patients who were included in clinical trials. Between 1996 and 1999, 27 renal transplant patients received RAPA alone or in combination with cyclosporine (CyA). We study 15 of them (9 males, 6 females; mean age 36 years) who are currently functioning with a mean follow-up of 6 years (range, 5.2-8 years). The presence of delayed graft function was 40% and acute rejection 26.6%, all of them controlled with steroids. Notably, no patients experienced an acute rejection episode after the first year. Among 15 patients, 12 received steroids, RAPA and CyA; and 3 received steroids, RAPA, azathioprine (AZA) or mycophenolate mofetil (MMF) for immunosuppression. At the end of follow-up, the situation was the opposite: 12 patients received steroids (2.5-5 mg/d) and RAPA associated with or without AZA/MMF, and 3 were maintained with steroids, RAPA and CyA. Renal function was excellent in the entire group: mean SCr 1.1 mg/dL (range, 0.7-1.8) with mean RAPA blood levels (HPLC) of 11 ng/dL (range 8-16). Hyperlipidemia was universal with all patients (100%) receiving statins maintaining acceptable levels of cholesterol (mean 209 +/- 28 mg/dL) and tryglycerides (mean 154 +/- 76 mg/dL). Arterial hypertension present in 12 of 15 (80%) patients was controlled with a mean of 1.5 drugs. Notably, no patient presented with proteinuria, neoplasia, posttransplant diabetes, or cardiovascular events. In conclusion, these single-center results suggest that Rapamune may be useful in the long-run after renal transplantation. The presence of normal renal function and the absence of proteinuria and neoplasia in these renal transplant patients may have important clinical implications.

Adrenal Cortex Hormones↗
PubMed2005

Ten years of treatment with tacrolimus is related to an excellent renal function, allowing monotherapy in a large proportion of cases: unicentric results of the tacrolimus versus cyclosporine A European Multicentric Study in kidney transplant patients.

Tacrolimus (Tac) is the most frequently used base inmunosuppressant for transplantation in Spain and the United States. However, long-term data on its use in renal transplant patients are lacking. The aim of this study was to analyze the 10-year outcome of patients from our institution treated with Tac or cyclosporine (CsA) who were included in the European Multicenter Study of kidney transplantation (1993 to 1994). This trial compared the efficacy and safety of steroids + Tac + azathioprine versus steroids + CsA + azathioprine at 1 year, showing a significantly lower acute rejection rate in Tac patients, with no differences in graft or patient survival. In our long-term analysis, we included patients with a functioning graft after the first year: 15 patients on Tac and 11 on CsA. In the "intent-to-treat" (ITT) analysis, patient survival was 14/15 (93%) versus 9/11 (82%) and death noncensored graft survival was 10/15 (67%) versus 8/11 (73%) in Tac and CsA, respectively. Analyzing patients "into treatment" (TT), death/noncensored graft survival was 11/16 (69%) versus 6/9 (67%), respectively. Serum creatinine tended to be lower in Tac group (ITT 1.26 +/- 0.42 vs 1.63 +/- 1.16 mg/dL, P = NS; TT 1.23 +/- 0.4 vs 1.86 +/- 1.28 mg/dL, P = NS). However, in the TT analysis, Tac patients exhibited a significantly better creatinine clearance (89.3 +/- 40 vs 46.8 +/- 21 mL/min, P = .037) and lower systolic blood pressure (125 +/- 5 vs 140 +/- 12 mm Hg, P = .007) at 10 years. No other significant differences were observed in blood pressure, lipid profile, or glucose metabolism. Outstandingly, Tac monotherapy was the most frequently used regimen after 10 years: ITT 6/9 (67%) versus 1/8 (12.5%), P = .05, TT 7/10 (70%) versus 0/6 (0%), P = .011. Patients under Tac monotherapy exhibited an excellent graft function (serum creatinine 1.08 +/- 0.14 mg/dL) and negative proteinuria, with Tac trough levels of 7.9 +/- 1.3 ng/mL. In summary, our results suggest that Tac-based immunosuppression provides an excellent kidney function 10 years after transplantation and allows monotherapy in a high percentage of kidney transplant patients.

Adult↗
PubMed2005

Paediatric trauma in Spain: a report from the HUGM Trauma Registry.

OBJECTIVES: To analyse the characteristics of the infant population suffering trauma in our setting. To evaluate the importance of the different aetiological mechanisms. To study the pre- and intra-hospital management of these children. To describe the relative significance of the different lesions. To establish the magnitude of paediatric trauma as a social problem in terms of morbidity and mortality. MATERIAL AND METHODS: From January 1995 to April 2002, a total of 2633 children admitted to our Centre (Hospital Universitario Gregorio Maranon) after suffering some type of injury were included in our Trauma Register. 108 variables have been analysed, including the identification of the patient, type, site and mechanism of the accident, pre-hospital care, transport, complete evaluation on admission, indices of injury severity, diagnostic tests, lesions, treatments performed and morbidity and mortality. RESULTS: The accidents were more frequent in boys than in girls (68.5 % versus 31.5 %). The predominant age group was the 12 - 15 year old group (36.8 %). There was a higher frequency of accidents in the street (37.2 %) than at home (19.4 %) or at school (13.8 %). The most frequent mechanism was a fall (35.6 %), followed by road traffic accidents (23.7 %). On admission, 14.7 % of the children had a Paediatric Trauma Score (P.T.S.) < or = 8 (n = 388). 3.8 % were considered severe multiple trauma patients, presenting an Injury Severity Score (I.S.S.) > or = 15 (n = 101). 4.2 % of the children required intensive care. The most frequent lesions were those of the locomotor system (58.1 %) and head injuries (34.9 %). Some type of surgical or orthopaedic procedure was performed under general anaesthesia in 1522 patients (57.8 %). The mean length of stay was 4.4 days (range 1 - 214 days). Sequelae of some form were detected in 36.4 % of the patients over 3 years of age. The total mortality was 0.5 % (n = 13), being 12.8 % in the group of patients with an I.S.S. > or = 15. CONCLUSIONS: Analysis of the data in our Registry has helped us to define the characteristics of the paediatric trauma population in our setting, to monitor the management of trauma in the different care levels and to develop prevention programmes. It has also enabled us to compare the results with those of other centres in terms of morbidity and mortality with the aim of identifying and correcting any possible deficiencies in the care system.

Accidents↗
PubMed2005

[Use of oral anticholinergic therapy in children under 1 years of age with high risk bladder].

THE AIM: To assess the effectiveness and safety of the treatment with oral anticholinergic agents (Oxybutin clorure) in patients under 1 year old, and who aree carriers of high risk bladder secondary to neurological illness as well as no neurological one. MATERIAL AND METHODS: Since 1989, we have indicated treatment with anticholinergic agents to 16 patients: 9 patients had neurogenic bladder secondary to: myelomeningocele (n=7) and sacrocoxigeal teratoma (n=2). Others 7 patients had non neurogenic bladder secondary to: posterior urethral valvulas (n=1), valvula-like syndrome (n=4), post-surgery of neonatal giant bladder diverticulum (n=1) and Prune-Belly syndrome (n=1). The urodinamic study was performed during the first six months of life, being "high risk bladder" defined according to the parameters of compliance vesical and pressure of leak at point (PER). Five of the patients showed neonatal cronic renal failure (CRF), who were treated by cutaneus temporary derivation. All patients at treatment with anticholinergic agents at a 0.2 mg/kg/day dose was established; other early adjunctive treatment prior to the closure of the urinary derivation in children with CRF(n=5); or as a part of the conservative treatment (n=3), alone or associate to intermittent bladder catheterization (IBC) (n=8). During the treatment with anticholinergic agents, the cardiac frequency was controlled by EKG registration in 6 patients, being the rest of the children clinicaly controled (skin colour, mouth dryness, cardiac frequency and intestinal function). RESULTS: In all the cases, the minimum duration of the treatment was one year, until the functional stabilization of the urinary tract. It is to underline the absence of secondary complications which would have caused the suspension or the reduction of the treatment at long term. Conventional studies of urologicals image and urodinamic studies, showed the stabilization of the urinary tract and also the preservation of kidney function and not only was demonstrated in those patients with oral anticholinergic agent as their unique treatment, but also in those patients who had previously been derivated. The previous vesical stabilization allowed the optimum result of subsequent corrective surgeries in five patients (ureteroneocystostomy and vesiscotomy clousure. In cases with previous derivation, the treatment with oral anticholinergic agents made easier vesicostomic clousure in the forth quarter of the first year old wih the maintenance of the vesical stability. CONCLUSIONS: The use of oral anticholinergic agents at a dose of 0.2 mg/kg/day, has resulted to be safe as well as effective in the treatment of high risk bladder in infancy those with less than one year of life. In those patients with serious dysplasia by reflux, it contributes to the preservation of kidney function, it makes easier the early desderivation and it also stabilizes in a functional way the bladder as a previous step to subsequent reconstructive surgeries.

Child↗
PubMed2005

[Evidence-based medicine in Spanish pediatric surgery reports].

INTRODUCTION: Pediatric surgical literature is characterized by a high prevalence of observational studies and a paucity of randomized controlled trial, comparing mainly medical therapies. AIMS: To asses scientific evidence level produced by spanish pediatric surgeons. MATERIAL AND METHODS: Articles reported in Cirugía Pediátrica, surgical reports in Anales Españoles de Pediatría, and reports from spanish authors published in the Journal of Pediatric Surgery, Pediatric Surgery International and European Journal of Pediatric Surgery, from 1997 to 2002. Internal validity was assessed through the critial guides from Sackett, and evidence level was classified through the Oxford Centre for Evidence Based Medicine classification. RESULTS: 94.5% on therapy reports, 61.5% on diagnosis, 83.3% on prognosis and 52.2% on risk factors or etiology, were classified as level 4 (descriptive studies). Only four randomized controlled trials were found, all of them comparing medical therapies (analgesia, antibiotics and surgical stress control). CONCLUSIONS: Our results are similar to those offered by previous reviews, showing up a low level of scientific evidence in most articles. Diffusion of guides on reporting descriptive studies may improve the evidence level of our reports.

Child↗
PubMed2005

Anaphylaxis caused by cauliflower.

BACKGROUND: Cauliflower is a vegetable belonging to the family Cruciferae, genus Brassica, var. Botrytis. METHODS: We report the case of a 70 year-old man who suffered an acute episode consisting of oropharyngeal itching, facial and hand swelling, dyspnea and severe bronchospasm within a few minutes after eating vegetable paella containing cauliflower, green beans, red and green pepper. Due to the severity of the reaction he needed treatment in the emergency room. RESULTS: Skin prick tests with common aeroallergens were positive to Cupressus, Platanus and grass pollen. A strong skin prick test response was obtained with cauliflower and peach lipid transfer protein. Skin prick test with rice, green beans and pepper were negative. Specific IgE determinations were positive to cabbage and cauliflower, and negative to mustard. CONCLUSIONS: The clinical history and the results of the allergologic work-up point out to this patient having experienced an IgE-mediated anaphylactic reaction to cauliflower. To the best of our knowledge, this is the first case report of anaphylaxis due to cauliflower.

Aged↗
PubMed2005

[Spinal cord and vertebral column injuries in children].

AIMS: Analysis of main factors of spinal cord and vertebral column injuries in our environment. METHODS: We reviewed the data collected from the patients (n = 2640) admitted to our hospital because of trauma and included in our Registry from January 1995 to April 2002. Among this group, 86 patients (3.3%) had spinal cord and vertebral column injuries and were included in the study. RESULTS: Group gender distribution was 45 males and 41 females. In our group, 71 patients suffered vertebral fractures, 3 of them with spinal cord injuries (4.2%), 13 patients with vertebral subluxation, 11 of them between C1-C2, and 2 patients with spinal cord injury without radiographic abnormality. Only 71 patients, 4.9% of the total of the patients who were admitted with any type of fracture (n=1457), suffered vertebral fractures. These patients suffered 130 vertebral fractures, 35 of them (49.3%) suffered multiple fractures. Thoracic vertebrae were the most frequently affected (n=82, 63%). The most frequent localization was T4 toT8 (n=50, 38.5% and T11 to L2 (n=41, 31.5%). Age ranged between 12 and 15 years (n=35, 49.3%), with only 5 patients under 6 years. 90.9% of the patients with lumbar fractures were older than 8 years and 76.9% of the patients with cervical fractures were over 8 years. Motor vehicle accident was the most common cause in our series (n=20, 23.3%). 81% of these patients did not use safety belt. Ten children with cervical injuries were seen by medical staff at the prehospital stage, and only 4 of them arrived to Hospital with cervical collar. There were thirty five patients with thoracic or lumbar injuries but only 27 of them were transferred to our Institution by ambulance. Surgery was required in 2 patients, both of them with unstable fractures. Mean hospital stay was 17,1 days (range 2-37 days). CONCLUSIONS: Group gender distribution is similar between males and females and the incidence in our series is higher than other series of the literature. Thoracic injuries are the most frequent. It is necessary to improve prehospital management of these patients and to increase the use of safety belt. Spine injury incidence increased with age.

Adolescent↗
PubMed2004

Study of the antibody response against Mycobacterium tuberculosis antigens in Warao Amerindian children in Venezuela.

This study was aimed at investigating alternate methods for serodiagnosis of tuberculosis (TB), which are needed because bacteriologic diagnosis of childhood TB is difficult. A selection of 80 serum and saliva samples were tested from Warao indigenous children under 15 years of age; 34 high TB suspects (28 positive and 6 negative for the tuberculin skin test, TST) and 46 healthy contact children (32 positive and 14 negative for the TST). Several enzyme-linked immunosorbent assay (ELISA) serological tests were developed to test for Mycobacterium tuberculosis-specific antibodies, including serum IgA, IgG, IgE, and secretory IgA (sIgA) in saliva against 3 specific antigens (PPD, HSP60, 38 kDa). Of these, 2 antigens, PPD and 38 kDa, showed significantly higher reactivity. The sensitivity and specificity of these tests for diagnosis remained limited, between 26.5% and 38.2%, and 77.4% and 97%, respectively. Of all the samples studied and combinations realized between all isotypes and antigens combined with 3 isotypes (anti-PPD IgG, IgE, and anti-38kDa sIgA) managed to detect the largest number of patients, showing an improved sensitivity level of 64.7%, although specificity levels dropped to 81.8%. These results were compared with the Omega diagnostics commercial kit results. The commercial kits showed significantly lower reactivity (sensitivity of 20% and 13.33% to Myco G and Complex Plus, respectively) and a specificity of 100%. This study shows that in indigenous populations of Venezuela, where invasive procedures cannot be used to select samples but evaluation with a chest X-ray for radiological studies is available, the combination of 3 specific isotypes may be a useful tool to increase diagnostic accuracy with pulmonary TB in this population, when used together with clinical and epidemiological criteria.

Adolescent↗
PubMed2004

Electronic, thermal and mechanical properties of carbon nanotubes.

A review of the electronic, thermal and mechanical properties of nanotubes is presented, with particular reference to properties that differ from those of the bulk counterparts and to potential applications that might result from the special structure and properties of nanotubes. Both experimental and theoretical aspects of these topics are reviewed.

Biocompatible Materials↗
PubMed2004

Use of sorption and extraction tests to predict the dynamics of the interaction of trace elements in agricultural soils contaminated by a mine tailing accident.

Over 2000 ha of agricultural soils were contaminated by a pyritic sludge and acidic waste waters coming from a spill from a mining exploitation. The affected soils were acidic with sandy-loam texture (SL), loamy with neutral pH (L), and calcareous, saline, with clay texture (Cs). The Cs soils were contaminated only with acidic waste waters. Sorption and extraction tests were applied to examine the medium-term dynamics of the interaction of trace elements (As, Cd, Cu, Pb and Zn) in the soils. The solid-soil solution distribution coefficient (KD) was determined in soil samples taken 3 months (initial stage, 3M samples) and then nearly 2 years (final stage, 21M samples) after the accident. Distribution coefficient values ranged from the lowest values in the SL samples (from 0.2 l kg(-1) for Cd and Zn to 25 l kg(-1) for As) to higher values in the L and Cs soils. Lead and As had the highest KD in all soils (over 10(5) l kg(-1) in the L soils). No clear dynamics pattern could be derived from these data because of the low heavy metal concentrations in the soil solution. As a complementary approach, four single extractions (0.01 and 1 mol l(-1) CaCl2; 0.05 mol l(-1) EDTA; 0.43 mol l(-1) CH3COOH) were applied to soil and sludge samples. Samples derived from submitting field 3M samples to drying-wetting (DW) cycles were included to define a complete laboratory approach to predict field dynamics. Results from extraction tests indicated that changes of the trace element interaction over time depended on the soil pH and on the source of contamination. For those soils affected only by the acidic waste waters, where an increase in fixation occurred, natural processes such as diffusion controlled dynamics. For those soils contaminated by a mixed source, the dynamics of the interaction was the resultant process of the combination of the natural attenuation and the oxidation of the pyritic sludge. This latter process led to an increase in the remobilization for those elements associated with soluble secondary minerals (Cd and Zn) and to an increase in the fixation for those elements coprecipitating with insoluble secondary minerals (Pb and As). Drying-wetting cycles were useful to predict the dynamics in the field at month-year scale. The CH3COOH was recommended as the best test among those studied here to derive conclusions about dynamics pattern because it provided significant desorption yields in most scenarios. Acidic soils with sludge contamination represented the scenarios with the highest risk, while calcareous soils better attenuated contamination. In a longer time scale, the depletion of calcareous components needs to be controlled.

Journal Article↗
PubMed2004

Two-wave mixing by means of dynamic Bragg gratings recorded by saturation of absorption in erbium-doped fibers.

We present experimental results of two-wave mixing in single-mode Er-doped optical fibers for which dynamic Bragg reflectance gratings are formed as a result of saturation of fiber-optic absorption (i.e., by means of the effect of spatial hole burning). The gratings are probed by the same recording waves at lambda approximately = 1549 nm and are detected as periodic changes of the intensity of light reflected from a Sagnac interferometer (with a piece of the doped fiber included) observed when periodic phase modulation is induced in one of the waves. Both rectangular and sinusoidal modulation were used, which permitted evaluation of the grating recording time (tau(g) approximately = 3 ms for OFS-Fitel EDF-HG980 fiber) and the grating amplitude, which proved to be approximately 6-7 times lower than expected from measurements of saturation of fiber-optic absorption by one wave only.

Journal Article↗