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J Lafuente

Publications and source records attributed to J Lafuente.

At least 19 recordsLinked to original sources
PubMed2006

Role of the C2 articular branches in occipital headache: an anatomical study.

One of the most important structures involved in the pathogenesis of occipital headache is the lateral atlanto-axial joint. Previous studies demonstrated that injection of this joint with local anesthetic can alleviate occipital headache, while injection of contrast medium exacerbates it. The aim of our study is to improve the understanding of the nerve supply to the lateral atlanto-axial joint by the C2 nerve elements, in order to determine the optimal target for an anesthetic block of this area. Ten C2 spinal nerves and roots were dissected in five embalmed cadavers with the aid of a 40X microscope and the lateral atlanto-axial joint was shown to be extensively supplied by articular branches of C2 nerve elements (dorsal ganglion, spinal nerve, and ventral ramus). Following our observations on their distribution, we propose a target for local anesthetic injection of the C2 articular branches that is based on reliable landmarks and is easily identifiable at fluoroscopy. We suggest that local anesthetic injection at this target point could be of benefit in the relief of occipital pain due to cervical trauma or degenerative disease involving the lateral atlanto-axial joint.

Anesthetics, Local↗
PubMed2006

Improving the start-up of an EBPR system using OUR to control the aerobic phase length: a simulation study.

The enhanced biological phosphorus removal (EBPR) process is based on enriching the sludge with polyphosphate accumulating organisms (PAO) which are scarce in conventional non-EBPR wastewater treatment plant sludge. Hence, the start-up of EBPR systems (i.e. enriching the sludge with PAO) can be very slow and complex. A simulation study of a possible improvement of the start-up of an EBPR system in a sequencing batch reactor is presented in this work. The improvement is based on reducing the length of the aerobic phase so that it coincides with the depletion of orthophosphate from the medium. This improvement, though verified by simulation to be very successful, requires a good on-line orthophosphate sensor. To avoid this technical limitation, a link between oxygen uptake rate (OUR) measurements and orthophosphate presence is proposed. This link allows the control of the aerobic phase length with OUR as a measured variable and, consequently, a considerable improvement with respect to the conventional fixed aerobic phase length operation. An improvement of 95% in the ratio of PAO to heterotrophs and an increase of 30% in the final amount of PAO in sludge is achieved with this control strategy. The kinetic mod for simulations was a modification of the Activated Sludge Model 2d.

Aerobiosis↗
PubMed2006

Observation and mathematical description of the acceleration phenomenon in batch respirograms associated with ammonium oxidation.

Two-step nitrification models are generally calibrated using short-term respirometric batch experiments. Important discrepancies appear between model predictions and experimental observations just after the pulse addition since a fast transient in the OUR profile is experimentally observed. Acceleration of the OUR appears ongoing between the substrate addition and attainment of the maximum OUR value. Among the several phenomena that could contribute to this observation, the most probable cause is the limitation of reducing equivalents required for maximal ammonia monooxygenase activity at the time of substrate addition. Ignoring acceleration would result in large parameter estimation errors from respirometric batch experiments. This work proposes a simple methodology to successfully describe (not to explain) the acceleration phenomenon estimating only two parameters. This methodology consists of introducing a Gaussian-like expression in the model.

Ammonia↗
PubMed2005

The Bryan cervical disc prosthesis as an alternative to arthrodesis in the treatment of cervical spondylosis: 46 consecutive cases.

We present data relating to the Bryan disc arthroplasty for the treatment of cervical spondylosis in 46 patients. Patients with either radiculopathy or myelopathy had a cervical discectomy followed by implantation of a cervical disc prosthesis. Patients were reviewed at six weeks, six months and one year and assessment included three outcome measures, a visual analogue scale (VAS), the short form 36 (SF-36) and the neck disability index (NDI). The results were categorised according to a modification of Odom's criteria. Radiological evaluation, by an independent radiologist, sought evidence of movement, stability and subsidence of the prosthesis.A highly significant difference was found for all three outcome measurements, comparing the pre-operative with the post-operative values: VAS (Z = 6.42, p < 0.0001), SF-36 (mental component) (Z = -5.02, p < 0.0001), SF-36 (physical component) (Z = -5.00, p < 0.0001) and NDI (Z = 7.03, p < 0.0001). The Bryan cervical disc prosthesis seems reliable and safe in the treatment of patients with cervical spondylosis.

Adult↗
PubMed2004

Improving the biological nitrogen removal process in pharmaceutical wastewater treatment plants: a case study.

The Biological Nitrogen Removal (BNR) process of some pharmaceutical wastewater treatment plants has important operational problems. This study shows that, in order to solve these problems, the design of industrial BNR processes should start by analysing three key parameters: the characteristics of the wastewater load, the determination of the maximum TKN removal rate and the detection of toxic or inhibitory compounds in the wastewater. A case study of this analysis in pharmaceutical wastewater is presented here. In this case, the conventional TKN analytical method does not make an accurate characterisation of the wastewater load because it measures a concentration of 100 mg TKN l(-1) whereas the real concentration, determined with a modified TKN analytical method, is 150-500 mg TKN l(-1). Also, the TKN removal of the treatment system is insufficient in some periods because it falls below legal requirements. This problem might be a consequence of the wrong characterisation of wastewater during the design process. The maximum TKN removal at 27 degrees C (24 mg N g VSS(-1) d(-1) or 197 mg N l(-1) d(-1)) was evaluated in a pilot-scale plant. This value is six times greater than the average NLR applied in the full-scale plant. Finally, some of the components of the wastewater, such as p-phenylenediamine, might have inhibitory or toxic effects on the biological process. P-phenylenediamine causes a large decrease in the nitrification rate. This effect was determined by respirometry. This methodology shows that the effect is mainly inhibitory with a contact time of 30 min and if the contact time is longer, 14 hours, a toxic effect is observed.

Bioreactors↗
PubMed2004

Response of an EBPR population developed in an SBR with propionate to different carbon sources.

The effect of different carbon sources (propionate, acetate, butyrate and glucose) on an enhanced biological phosphorus removal biomass developed with propionate as the sole carbon source was studied. Firstly, a group of different cycle studies was carried out using each substrate independently and then, another cycle study was performed with a mixture of substrates. Propionate was found to be the substrate with the highest substrate uptake rate in both sets of experiments. It was also the volatile fatty acid (VFA) which required less reducing power and less P-release to be uptaken. Four different polyhydroxyalkanoate (PHA) monomers produced during the anaerobic phase were detected, and PHB, PHV and PH2MV were quantified. Significant differences in PHA composition were obtained depending on the carbon source. The carbon recovery ratio for the anaerobic phase was also evaluated. The lowest value observed among the different cycle studies was obtained for butyrate, while the highest value was obtained for acetate.

Acetates↗
PubMed2003

Biological nitrogen removal of high-strength ammonium industrial wastewater with two-sludge system.

The biological nitrogen removal (BNR) process is the most common method for removing low quantities of ammonium from wastewater, but this is not the usual treatment for high-strength ammonium wastewater. The capacity to biologically remove the nitrogen content of a real industrial wastewater with a concentration of 5000 g N-NH(4)(+) L(-1) is demonstrated in this work. The experimental system used is based on a two-sludge system, with a nitrifying activated sludge and a denitrifying activated sludge. This system treated real industrial wastewater for 450 days, and during this period, it showed the capacity for oxidizing all the ammonium at average nitrification rates between 0.11 and 0.18 g N-NH(4)(+)g VSS(-1)d(-1). Two key process parameters were evaluated: the maximum nitrification rate (MNR) and the maximum denitrification rate (MDR). MNR was determined in continuous operation at three different temperatures: 15 degrees C, 20 degrees C and 25 degrees C, obtaining values of 0.10, 0.21 and 0.37 g N-NH(4)(+) g VSS(-1)d(-1), respectively. Complete denitrification was achieved using two different industrial carbon sources, one containing mainly ethanol and the other one methanol. The MDR reached with ethanol (0.64 g N-NO(x)(-) g VSS(-1)d(-1)) was about 6 times higher than the MDR reached with methanol (0.11g N-NO(x)(-)g VSS(-1)d(-1)).

Bioreactors↗
PubMed2003

MRI study of the natural history and risk factors for pseudomeningocoele formation following postfossa surgery in children.

Surgical approaches to the posterior fossa may be complicated by pseudomeningocoele formation. We report on its natural history and risk factors for its formation, as seen on serial MRI postoperatively in children with posterior fossa tumours. In a retrospective study of 84 children undergoing surgery for posterior fossa tumours, 13 (16%) developed clinically apparent pseudomeningocoeles. On postoperative MRI, pseudomeningocoeles were apparent in 34 (41%) patients at 1-5 days, but in only four patients at 10-15 months postsurgery. There was a progressive decrease in the mean depth of pseudomeningocoele measured from the MRI scans postoperatively. Patients with pseudomeningocoeles were more likely to have a postoperative CSF leak from the wound (39 v. 13%), lumbar punctures or lumbar drains (54 v. 25%), wound re-closures (23 v. 1%) and prolonged hospital stay (19.9 v. 14.5 days). On multivariate analysis, patients with pseudomeningocoeles were also more likely to have undergone a suboccipital craniectomy than those without pseudomeningocoeles (69 v. 38%). Postoperative pseudomeningocoele formation following posterior fossa surgery is more apparent radiologically than clinically, but there is clinical and radiological evidence that pseudomeningocoeles gradually resolve over the postoperative period. The risk of pseudomeningocoele formation is increased by performing a suboccipital craniectomy and there is an association with increased CSF leaks, needing re-closure of the wounds.

Adolescent↗
PubMed2003

Ruptured intracranial aneurysms: the outcome of surgical treatment in experienced hands in the period prior to the advent of endovascular coiling.

OBJECTIVES: To evaluate the results of treatment of patients with a ruptured intracranial aneurysm treated by a single experienced vascular neurosurgeon in the period prior to the introduction of endovascular coiling. METHODS: Over a mean (SD) period of 9 (2) years, between January 1990 and June 1999, 245 consecutive patients with ruptured intracranial aneurysms were treated. Patients' details were obtained from a database that had been constructed prospectively. The patients consisted of all those patients treated by the senior author (Mr Maurice-Williams) over this period-that is, every third day on call at his unit. During this period, all patients under the age of 75 years with a diagnosis of subarachnoid haemorrhage were admitted to the neurosurgical unit as soon as was practicable regardless of clinical grade. RESULTS: Of 245 patients, 190 (77.6%) underwent treatment by open surgery using standard microsurgical techniques. At 1 year, the mortality of the operated patients was 2.6%, while 89.5% of the patients had a Glasgow Outcome Score (GOS) of 4 and 5. The overall management outcome (all patients treated, including operated and non-operated cases) at 1 year was: 17.1 % dead while 74.3% had GOS 4 and 5. Of the 190 patients who underwent surgery, 38 (20%) required additional operations, totalling 72 operations in all. Of these, 32 were for hydrocephalus and 17 for the evacuation of intracranial haematomas/collections. Complications of surgery occurred in 56 patients (29.5%). CONCLUSION: Open surgery, despite good eventual results, is associated with a significant rate of re-operations and complications that would probably be largely avoided with endovascular treatment. Nevertheless, although endovascular coiling has these immediate advantages over surgery it is still not certain that the long term results will be superior to surgery which leads to permanent obliteration of the aneurysm. There may still be a need for open surgery in the future.

Adolescent↗
PubMed2003

[Fiberoptic bronchoscopy, 3-D reconstruction of the airway and virtual bronchoscopy in patients with airway malformations. Preliminary report].

UNLABELLED: Bronchoscopy is the diagnostic gold standard in patients with airway malformations. Helical CT scan has produced studies such as virtual bronchoscopy or 3-D reconstruction of the airway. The purpose of this study is to analyze the correlation between fiberoptic bronchoscopy, virtual bronchoscopy and 3-D reconstruction of the airway in patients with airway malformations. METHODS: From January 2001 to March 2002 we evaluated the airway of 17 patients with airway malformations by means of a diagnostic protocol consisting on fiberoptic bronchoscopy, and Helical CT scan with 3-D reconstruction of the airway and virtual bronchoscopy. The radiologist had no access to bronchoscopic information. Age at study, associated cardiovascular anomalies, indications, localization, degree of diagnostic concordance, etiology and influence in treatment were analyzed. RESULTS: 20 studies were done to 17 patients whose mean age was 1.64 +/- 0.48 years (7 days-7 years). Twelve patients had associated anomalies of the aorta, pulmonary arteries or supraortic vessels. Excellent concordance was obtained in 13 cases (65%), good in 6 (30%) and poor in one (5%). 3-D reconstruction of the airway and adjacent vascular structures provided additional information in 14 cases (70%): in 3 exact length of the tracheal lesion and in 11 defined the cause of the compression. In all the cases, absolute concordance in localization was obtained. CT scan information modified treatment in 6 patients (35%). In 7 patients with associated vascular anomalies, no further image studies were done, confirming the anatomy concordance during surgery. CONCLUSIONS: 3-D reconstruction of the airway and virtual bronchoscopy are excellent diagnostic tools in patients with airway malformations, and contribute to define the etiology, length and diameter of the lesion. Excellent diagnostic correlation was obtained between analogic and virtual bronchoscopies, although further multicentric studies should be conducted.

Bronchi↗
PubMed2003

An off-line respirometric procedure to determine inhibition and toxicity of biodegradable compounds in biomass from an industrial WWTP.

Determining whether a certain compound is toxic (or inhibitor) or not to a biomass of a WWTP is crucial in order to avoid WWTP malfunction. Respirometric techniques have been commonly used to assess the toxicity of a certain compound by evaluating the oxygen uptake rate (OUR) profile obtained when a pulse of substrate is added to endogenous biomass and comparing it with the OUR profile obtained when the pulse is a mixture of substrate and the possible toxic or inhibitor (PTI). However, when using this method with biodegradable compounds some difficulties arise because the PTI consumption implies oxygen consumption as well. In this study, a modified procedure for toxicity assessment using respirometry is developed which overcomes the difficulties caused by the toxic biodegradability. This procedure is based on the comparison of different respirograms obtained with pulses of control substrate before and after adding the PTI and with a pulse of PTI and control substrate together. Moreover, some examples are shown with p-phenylenediamine and phenol as an example of toxic and inhibitor for nitrifying biomass.

Biodegradation, Environmental↗
PubMed2002

Improving the nitrogen removal efficiency of an A2/O based WWTP by using an on-line knowledge based expert system.

The results obtained using an expert system to control an activated sludge process involving nutrient removal are reported. The study was conducted at a pilot plant using an Anaerobic/Anoxic/Oxic (A2/O) scheme for which a distributed control system was specially developed. The system allows various expert operational approaches to be developed with a view to minimize nitrogen levels in the outlet while using the minimum amount of energy. The proposed distributed control system is supervised by a Knowledge Based Expert System (KBES) constructed with G2 (a tool for expert system development) and permits the on-line implementation of every operating strategy of the experimental system. A set of experiments involving variable loads and flow-rates was carried out. It revealed that the amount of removed nitrogen could be increased by 11% compared to the usual operating conditions. This increase resulted in a decrease in the amount of total nitrogen and ammonium nitrogen in the outlet by 49% and 64%, respectively. These improvements were achieved with little energy cost because the performance of the treatment plant was optimised using operating rules implemented in real time.

Artificial Intelligence↗
PubMed2002

End-stage cardiac failure in a morbidly obese patient treated by biliopancreatic diversion and cardiac transplantation.

A 57-year-old 132-kg female (BMI 48.6) with end-stage cardiac failure is presented. Because of a progressive cardiomyopathy, the patient required a heart transplant. However, before receiving the transplant, major weight loss was deemed to be mandatory. Supervised dieting had manifestly failed, and thus a highly effective weight-reducing operation, biliopancreatic diversion, was performed. This resulted in a weight loss of 50.4 kg in 9 months. She then underwent successful cardiac transplantation, and progressed well for several months. She then developed severe psychiatric depression, withheld her medications and developed a lethal acute rejection phenomenon.

Biliopancreatic Diversion↗
PubMed2002

In-line fast OUR (oxygen uptake rate) measurements for monitoring and control of WWTP.

This paper shows how using in-reactor on-line monitoring of OUR in the aerobic reactors of an A2/O (anaerobic, anoxic, oxic) nutrient removal system, the implemented control system is able to improve the nitrogen removal of the plant. The control system adapts the operation to different load conditions, without the need for additional information provided by other analysers. In particular, these OUR measurements and on-line information available in the distributed control system (temperature, biomass concentration and flows) are used for the estimation of the COD load in the influent, and automatically applied in the adaptation of the operational mode of the nutrient removal process. The estimation is realised using Artificial Neural Networks models trained with available data from the system. The operational changes consist in the modification of the total aerated volume in the pilot plant as a function of the load estimation. With the implemented control system based on COD load estimation, an increase in nitrogen removal of 10% was obtained with respect to a system working with fixed aeration volume, and using a suitable amount of energy in each case.

Biomass↗
PubMed2002

A hybrid supervisory system to support WWTP operation: implementation and validation.

Integrated operation of Wastewater Treatment Plants is still far from being solved. A reasonable proposal should link advanced and robust control algorithms to some knowledge-based techniques, allocating the detailed engineering to numerical computations, while delegating the logical analysis and reasoning to supervisory intelligent systems. This paper describes the development and implementation of a knowledge-based Hybrid Supervisory System to support the operation of a real Wastewater Treatment Plant. The system integrates different reasoning modules, overcoming the limitations in the use of each single technique, while providing an agent based architecture with additional modularity and independence. It is structured into three separated levels: data gathering, diagnosis, and decision support. The different tasks of the system are performed in a seven-step cycle: data gathering and update, diagnosis, supervision, prediction, communication, actuation, and evaluation phase. In spite of certain reservations of the scientific community about the use of these techniques, the system is successfully performing real-time support to the operation of the Granollers facility since September 1999. Results of the first four-month validation period are shown and discussed. An example of the system behavior is also shown in the paper. The conclusions indicate the key steps which are necessary to transfer the system to another facility.

Algorithms↗
PubMed2001

Continuous enantioselective esterification of trans-2-phenyl-1-cyclohexanol using a new Candida rugosa lipase in a packed bed bioreactor.

Enantioselective resolution of trans-2-phenyl-1-cyclohexanol (TPCH) by a Candida rugosa lipase, obtained by fermentation in the laboratory, and immobilised on EP100 polypropylene powder has been carried out using isooctane as solvent and propionic acid as esterifying agent. The study have included the utilisation of this biocatalyst in a batch process and the optimisation of the esterification conditions by means of a Box-Hunter-based experimental design. The main variables controlling the process, concentration of acid and alcohol, have been numerically optimised using initial esterification rate as objective function. The optimal concentrations for the batch process were 50 mM for the alcohol and 71 mM for the acid. This esterification reaction kinetics corresponded to a reversible Michaelis-Menten kinetic law for the optimal conditions, which has permitted to select a plug-flow packed bed bioreactor as the most appropriate configuration to minimise the residence time and to avoid shear stress effect on the biocatalyst. The behaviour of the continuous packed bed bioreactor at two different residence times (302 and 582 min) was in accordance with predictions from batch experiments, with slightly deviations (less than 10%). Continuous experiments maintained high values of enantioselectivity (enantiomeric factor was practically 1) and conversion near equilibrium value (35%) when long-time operation was carried out. Besides, long-time stability of biocatalyst has permitted to scale-up the production of enantioenriched (1R,2S)-TPCH propionate to yield gram quantities.

Bioreactors↗
PubMed2000

Highly enantioselective esterification of racemic ibuprofen in a packed bed reactor using immobilised Rhizomucor miehei lipase.

A systematic study of the enantioselective resolution of ibuprofen by commercial Rhizomucor miehei lipase (Lipozyme(R) IM20) has been carried out using isooctane as solvent and butanol as esterificating agent. The main variables controlling the process (temperature, ibuprofen concentration, ratio butanol:ibuprofen) have been studied using an orthogonal full factorial experimental design, in which the selected objective function was enantioselectivity. This strategy has resulted in a polynomial function that describes the process. By optimizing this function, optimal conditions for carrying out the esterification of racemic ibuprofen have been determined. Under these conditions, enantiomeric excess and total conversion values were 93.8% and 49.9%, respectively, and the enantioselectivity was 113 after 112 h of reaction. These conditions have been considered in the design of a continuous reactor to scale up the process. The esterification of ibuprofen was properly described by pseudo first-order kinetics. Thus, a packed bed reactor operating as a plug-flow reactor (PFR) is the most appropriate in terms of minimizing the residence time compared with a continuous stirred tank reactor (CSTR) to achieve the same final conversion. This reactor shows a similar behavior in terms of enantioselectivity, enantiomeric excess, and conversion when compared with batch reactors. A residence-time distribution (RTD) shows that the flow model is essentially a plug flow with a slight nonsymmetrical axial dispersion (Peclet number = 43), which was also corroborated by the model of CSTR in series. The stability of the system (up to 100 h) and the possibility of reutilization of the enzyme (up to four times) lead to consider this reactor as a suitable configuration for scale up of the process.

Journal Article↗