An evaluation of masking nuisance odors from a source by chemical and sensory analyses.

There are many products in the market advertised as masking agents used to overpower strong nuisance odors, such as in or around water resource recovery facilities, solid waste processing facilities, landfills, composting sites, and so forth. Very little is known about the chemical component of these masking agents because they are protected by trade secrets. This is a problem for the parties involved, as the process of choosing the most adequate agent for the particular odor source falls into guesswork. This paper demonstrates that it is possible to determine how effective the masking product would be before spending time and resources in trials. It proposes to show this by comparing the Weber-Fechner curves of the odor-causing compounds known to be emitted at the facility with the curves from the potential masking agents prepared in the laboratory using an olfactometer. Several sensorial examples show that when the Weber-Fechner curves of the odorants and those of candidate masking agents are compared, it is possible to define the effectiveness of the masking agent tested. This is a novel use of the Weber-Fechner curves. The results show there is direct correlation between what is observed by a panel with real life odor samples subjected to incremental dilution and the Weber-Fechner odor intensity-odor concentration curve interaction between the odorants involved. Future work characterizing additional potential masking compounds by Weber-Fechner accompanied by odor profiling with dynamic olfactometry should shed light on the definitive effectiveness of this method in predicting masking effects and discovering useful masking compounds. PRACTITIONER POINTS: Weber-Fechner curves provide relationships between odorant concentration and odor intensity. Dynamic olfactometry, in which real-life air samples are sensorially analyzed by the odor profile method after subsequent dilutions, shows that odor masking occurs. Analyzing the Weber-Fechner curves of the odorants present in the dynamic olfactometry test show the existing odorant interactions. It is possible to predict the extent of the masking of potential compounds by comparing Weber-Fechner curves of masking agents against odorants causing nuisance. This methodology could help avoid spending resources in masking field trials that may result in further exacerbating the affected public.

Evaluación de la función ventricular en la hipertensión pulmonar por resonancia magnética cardíaca / Evaluation of ventricular function in pulmonary hypertension by cardiac magnetic resonance

Resumen Objetivo: Evaluar la función del ventrículo derecho (VD) e izquierdo (VI) en la hipertensión pulmonar (HP) mediante resonancia magnética cardíaca (RMC). Material y métodos: En pacientes con (grupo HP; n = 9) y sin (grupo control; n = 9) HP se evaluó volumen telediastólico (VTD) y telesistólico (VTS) y fracción de eyección (FE) de ventrículo derecho (VD) e izquierdo (VI), área de aurícula derecha (AD) e izquierda y diámetro de arteria pulmonar (AP). Resultados: En HP, el VD presentó mayor VTD y VTS y menor FE (HP 52 ± 5% vs. control 64 ± 2%; p < 0,05). Solo en HP se observó movimiento anormal del tabique interventricular y realce tardío en los puntos de inserción del VD en VI. En HP aumentó el área de AD y el diámetro de AP. En VD, solo en HP, la FE se correlacionó negativamente con VTD (Pearson r: –0,8290; p < 0,01) y VTS (Pearson r: –0,7869; p < 0,05). Conclusiones: La evaluación de pacientes con HP mediante RMC demuestra alteraciones fisiológicas y anatómicas de las cavidades derechas con disminución de la FE del VD que también afecta la interrelación VD/VI. Se recalca la importancia de una evaluación temprana y secuencial del VD con RMC para valorar la mejor estrategia terapéutica para cada caso en particular.

Abstract Objective: To evaluate the function of the right ventricle (RV) and left ventricle (LV) in pulmonary hypertension (PH) through cardiac magnetic resonance imaging (CMR). Material and method: In patients with (PH group; n = 9) and without PH (control group; n = 9), end-diastolic volume (EDV) and end-systolic volume (ESV) and ejection fraction (EF) of right (RV) and left (LV) ventricle, area of the right (RA) and left (LA) atrium and diameter of the pulmonary artery (PA) were evaluated. Results: In PH, the RV increased EDV and ESV and decreased EF (PH: 52 ± 5% vs. control: 64 ± 2%; p < 0.05). Abnormal movement of the interventricular septum and late enhancement in the insertion points of the RV in the LV were only observed in HP. HP increased the area of RA and the diameter of PA. In LV, only in HP, EF was negatively correlated with EDV (Pearson r: –0.8290; p < 0.01) and ESV (Pearson r: –0.7869; p < 0.05). Conclusions: CMR evaluation of patients with PH demonstrates physiological and anatomical alterations of the right cavities with decreased EF in RV that also affects the RV/LV interrelationship. The importance of an early and sequential evaluation of the RV with CMR is emphasized to assess the best therapeutic strategy for each particular case.

A new method for evaluating nuisance of odorants by chemical and sensory analyses and the assessing of masked odors by olfactometry.

The odor threshold concentration and the odor nuisance concentration of the nine persistent odorants at two wastewater treatment facilities were determined by Weber- Fechner curves for each odorant using dynamic olfactometry combined with the odor profile method. The odor threshold concentration results, representing each odorant's concentration at odor intensity of one (I = 1), were within range in the literature. The nuisance concentrations were determined by interpolation along the curves intersecting with the arbitrary odor intensity of three (I = 3). There is no reference that exists in the literature about determining odor nuisance concentrations for a complete set of odorants from any facility. The nuisance concentration results presented here are novel to odor control because they can provide information defining the nuisance odorant's isopleths in modeling and in designing effective odor control systems that avoid public nuisance. Dynamic olfactometry combined with the odor profile method was also used with actual foul air samples from different sources. When analyzed from raw to increased dilution, it was observed that the fecal and sulfur odors initially prominent (with no musty odors detected) gradually changed with increased dilution. Musty odors began to gradually appear while the fecal and sulfur odors became undetectable. We named this observation the "peeling of an onion effect". It is speculated that this occurs because the musty odors in the concentrated foul air sample are masked by the fecal and the sulfur odors.

Evaluation of bioscrubber and biofilter technologies treating wastewater foul air by a new approach of using odor character, odor intensity, and chemical analyses.

The treatment of raw foul air that could escape to the atmosphere from the head space of the incoming wastewater into a Southern California Water Resource Recovery Facility was evaluated by using a 1/20th scale pilot unit consisting of five different biological media technologies, operating side by side, under different operating conditions. The removal of six different odor characters from eight chemical odorants present in the foul air were assessed. These were rotten egg (Hydrogen Sulfide), rotten vegetables (Methyl Mercaptan), canned corn (Dimethyl Sulfide), rotten garlic (Dimethyl Disulfide), earthy/musty (2-Methyl Isoborneol and 2-Isopropyl 3-Methyl Pyrazine) and fecal (Skatole and Indole). This is the first time a study evaluates specific odors by simultaneously employing sensory analyses using the Odor Profile Method, which defines the different odor characters and intensities, together with chemical analyses of the compounds causing these odors, known as odorants. The paper discusses the efficiencies in removing odor characters as well as odorants by two different bioscrubbers (reticulated polyurethane cube foam and polypropylene mesh with layered polyester foam) and three different biofilters (engineered media, seashells, and lava rock). The results show that the two bioscrubbers, even with greater empty bed gas retention times, did not provide significant improvement in odor intensity and odorant removal. However, the biofilters showed that larger empty bed gas retention times provided significant improvements in diminishing the odor intensities and better odorant removal. The biofilter with lava rock media at 45 s empty bed gas retention time provided the best treatment among the technologies tested, achieving the following odorant reductions: 99.8% for hydrogen sulfide, 98.4% for methyl mercaptan, 57.0% for dimethyl sulfide, and 52.7 for dimethyl disulfide. This biofilter also achieved the following odor intensity reductions: 47% for rotten vegetable odors, 50% for earthy/musty odors, and 100% for fecal odors. The odor panel detected odors by the Odor Profile Method that were below the detection limit of the corresponding chemical analytical method for specific chemical compounds causing these odors. Differences were observed between the performances of bioscrubbers and biofilters, based on odorant removal compared to those based on sensorial analyses, indicating that both analyses are required to understand more fully the odor dynamics. Furthermore, a total odor removal of 99.2% was observed by the dilution to threshold olfactometer method even though nearly half of the rotten vegetable and earthy/musty odors remained based upon the Odor Profile Method. This shows the olfactometer method did not correctly define the degree of odor nuisance in the foul air in this study. Bioscrubbers have in general a better economic return when used at low EBGRTs and as preliminary (first stage) treatment systems. Biofilters are more effective when used at high EBGRTs and can be used as stand-alone or polishing systems.

Corrective factors applied to reduced sulfur compounds in wastewater foul air.

To determine accurately odorant concentrations at its worst-case condition for planning and odor treatment design purposes, corrective factors need to be factored into the foul air monitoring results of water resource recovery facilities. These corrective factors will adjust each odorant concentration for usual seasonal and daily odor variations. Typically, corrective factors are taken from hydrogen sulfide continuous readings and applied to all identified sulfur odorants. This paper demonstrates that it is incorrect to assume all reduced sulfur compounds mimic the daily fluctuations observed in hydrogen sulfide. Reduced sulfur odorant results from the foul air tested at two different water resource recovery facility process areas over a portion of the daily cycle have been found to behave independently from hydrogen sulfide. Tests have shown that the corrective factors for each reduced sulfur odorant vary notably from facility to facility and enormously from process area to process area. This discovery is important for the improvement of the science of odor control because accurately determining worst-case odor concentrations affects the modeling (the magnitude of odor nuisance) and the level of treatment (choosing a technology or combination of technologies) needed for odor abatement. PRACTITIONER POINTS: When conducting foul air assessments, corrective factors are recommended to adjust the results for daily and seasonal variations. H2 S continuous monitors are readily available and of widespread use, therefore they are certainly useful to determine corrective factors. H2 S continuous monitors, however useful for H2 S, do not necessarily apply to the rest of the reduced sulfur compounds. Intermittent sampling and analysis for reduced sulfur compounds at each facility process location over a daily cycle should be conducted. Results will show the independence of each reduced sulfur compound and the importance of this testing to obtain corrective factors applicable to the facility being assessed.

A comparison of two types of preperitoneal mesh prostheses in stoma surgery: application to an animal model.

INTRODUCTION: The aim of this study is to compare the integration of two types of prostheses (high and low density, written as HD and LD, respectively) implanted around the stoma to reinforce the abdominal wall to prevent parastomal eventration. The surgical technique used for preperitoneal placement of the prostheses is also described. MATERIALS AND METHODS: We performed terminal sigmoid colostomies on 16 porcine animals. In 8 of the animals, HD prostheses were placed around the stoma in preperitoneal position, while in the other 8, we implanted wide-pore LD prostheses using the same surgical technique. The following macroscopic variables were then measured: adhesion, extrusion, stenosis, and retraction. A morphological study was also carried out to evaluate the foreign body reaction and the formation of neovascularization and collagen. All animals were killed 3 months after surgery. RESULTS: Differences were observed with regard to retraction (47 ± 17.8 % for HD vs. 55 ± 19.4 % for LD) and extrusion (50 % for HD vs. 0 % for LD). These differences did not reach statistical significance. There was a great amount of scarring for both types of prostheses, with stomal stenosis being observed in all cases. The number and consistency of intra-abdominal adhesions was low and similar for both types of prostheses. Neither eventration nor necrosis was observed for either type. With regard to the tissue response, we observed both fibrosis and calcification phenomena in the peristomal areas of the LD prostheses. In the HD group, there was both a lower scarring response and a higher foreign body response, with the areas of the prostheses remaining intact. CONCLUSIONS: Both types of prostheses are appropriate for preperitoneal placement in the experimental model used, leading to few intra-abdominal adhesions. Still, due to their integration characteristics, LD prostheses are more appropriate for implanting around the colon since they do not seem to lead to extrusions. When using prostheses, however, it is also essential to consider the important phenomenon of retraction, which is more common with LD mesh.

Prevalence of atrial thrombi in patients with atrial fibrillation/flutter and subtherapeutic anticoagulation prior to cardioversion.

AIMS: Thromboembolism may complicate electrical cardioversion (ECV) of atrial fibrillation/flutter (AF). The use of 3 weeks of warfarin before ECV results in a substantial reduction of thromboembolic complications. Nevertheless, in patients scheduled for ECV subtherapeutic INR levels are common. We sought to assess the prevalence and the predictors of atrial thrombi in patients affected with sustained AF in whom subtherapeutic INR values were detected in the 3 weeks preceding scheduled ECV. METHODS AND RESULTS: Forty-one patients with persistent AF and > or =3 weeks warfarin anticoagulation who exhibited subtherapeutic INR values in the last 3 weeks underwent a transoesophageal echocardiogram (TOE) before a scheduled ECV. A left atrial appendage (LAA) thrombus was diagnosed on TOE in four patients (9.8%). Patients with thrombus had lower INR values (1.45+/-0.09 vs 1.72+/-0.20; p=0.0068), lower LAA emptying velocities (13.75+/-4.5 vs 25.86+/-12.4 cm/s; p=0.0313) and higher prevalence of atrial smoke (100 vs 37.8%,p=0.03). CONCLUSIONS: Subtherapeutic levels of anticoagulation before elective ECV of AF may expose patients to post-ECV thromboembolic sequelae, especially in patients with lowest INR values. Current recommendations of a full course of therapeutic anticoagulation before ECV of persistent AF should be firmly observed.

Reproducibility of asystole during head-up tilt testing in patients with neurally mediated syncope.

Tilt induced prolonged asystole has been considered to identify a distinct subgroup of patients with neurally mediated syncope and management including permanent pacemaker implantation has been suggested. To evaluate the reproducibility of asystolic response during head-up tilt testing (HUT), 33 patients with neurally mediated syncope and asystolic response (> or = 3 seconds) during HUT prospectively underwent two consecutive tests 13 +/- 15 days apart. On repeat tilt testing asystole was reproduced in 12 patients (36%), while 8 patients still had a positive HUT, but without asystole. Remarkably, 13 patients (40%) had a negative repeat HUT. Among 12 patients with asystole on both HUTs there was no significant difference in duration of asystole (14 371 +/- 11 430 ms vs 13 707 +/- 10 470 ms, P = ns) and time to syncope (36 +/- 20 min vs 37 +/- 20 min, P = ns) during initial and repeat HUTs. In conclusion, asystole during tilt testing does not seem to be a reproducible response.

Thromboembolic risk in atrial flutter. The FLASIEC (FLutter Atriale Società Italiana di Ecografia Cardiovascolare) multicentre study.

AIMS: Patients with atrial flutter are believed to be at lower risk of thromboembolism than patients with atrial fibrillation. However, the incidence of atrial thrombi and the need for anticoagulation in patients with atrial flutter is not well established. METHODS AND RESULTS: A prospective observational multicentre study was undertaken to assess the frequency of atrial thrombi and spontaneous echocontrast and the prevalence for aortic complex atherosclerotic lesions in a cohort of unselected patients with atrial flutter. We evaluated 134 patients (102 male, aged 70+/-9 years); exclusion criteria were history of atrial fibrillation, rheumatic mitral valve disease and mitral mechanical prosthesis. The median of atrial flutter duration was 33 days. Twelve patients had been taking warfarin for more than 7 days. One hundred and twenty-four patients (94%) underwent a transoesophageal echocardiogram, which revealed left atrial appendage thrombi in two patients (1.6%) and right atrial thrombi in one patient (1%). At least moderate left atrial echocontrast was found in 16/124 patients (13%). Complex atherosclerotic aortic plaques were detected in 10 patients (8%). Atrial flutter conversion was attempted in 93/134 patients (69%). At the 1-month follow-up, two patients experienced a thromboembolic event following restoration of sinus rhythm. CONCLUSIONS: Atrial thrombi and echocontrast, and complex aortic atherosclerotic plaques are relatively uncommon in patients with atrial flutter. Post-cardioversion embolism was observed in two patients in our study population.

Isolated noncompaction of the ventricular myocardium. A study in an adult male and literature review.

Noncompaction of the ventricular myocardium is a rare congenital disorder characterized by the presence of numerous prominent trabeculations and deep intertrabecular recesses which communicate with the left ventricular cavity. The disease uniformly affects the left ventricle, sometimes also affecting the right ventricle. Noncompaction of the ventricular myocardium is believed to be a disorder of endomyocardial embryogenesis. Familial occurrence has been observed. It may be accompanied by depressed ventricular function, cardiac arrhythmia and systemic embolism. Although noncompaction of the ventricular myocardium is a congenital myocardial disorder, the onset of symptoms is frequently delayed until adulthood. We describe a case of noncompaction of the ventricular myocardium in a 33-year-old male with the typical echocardiographic and cardiac magnetic resonance imaging features of this disease.

Early cardioversion of atrial fibrillation and atrial flutter guided by transoesophageal echocardiography: a single centre 8.5-year experience.

AIMS: To analyse the safety and impact on maintenance of sinus rhythm of transoesophageal echocardiographically guided early cardioversion associated with short-term anticoagulation in a large series of patients with atrial fibrillation and atrial flutter. METHODS AND RESULTS: Patients who were candidates for cardioversion were eligible for inclusion if they had atrial fibrillation or atrial flutter lasting longer than 2 days or of unknown duration. Patients received short-term anticoagulation with warfarin or heparin and underwent transthoracic echocardiography followed by transoesophageal echocardiography. Early cardioversion was performed if no thrombus was seen on the transoesophageal study. Warfarin was maintained for 1 month after cardioversion. In patients with atrial thrombi, cardioversion was deferred and prolonged anticoagulation was prescribed. The study population included 183 patients. One hundred and sixty nine patients without atrial thrombi underwent early cardioversion. Fourteen patients with atrial thrombi (7.6%) underwent a second transoesophageal echocardiogram after a median of 4 weeks of oral warfarin, and cardioversion was performed if clot regression was documented. No patient in our study population had a clinical thromboembolic event at 1 month follow-up (95% C.I. 0-0.016). The immediate success rate of cardioversion was better among patients with atrial fibrillation < 4 weeks duration compared with patients with atrial fibrillation of longer or of unknown duration: 96.6% vs 85%, respectively (P = 0.014). At 1 month follow-up, the percentage of arrhythmia relapses in patients with initially successful cardioversion was similar in the two groups (29% vs 26%, P = ns); thus the initial better outcome in patients with recent-onset arrhythmia was not lost. CONCLUSION: Transoesophageal echocardiography-guided early cardioversion in concert with short-term anticoagulation is safe. This approach permits abbreviation of the overall duration of atrial fibrillation and has a better impact on the maintenance of sinus rhythm for patients in whom the duration of atrial fibrillation is < 4 weeks.

Atrial thrombosis in cardiac amyloidosis: diagnostic contribution of transesophageal echocardiography.

Few cases of atrial thrombosis detected by transesophageal echocardiography (TEE) in cardiac amyloidosis have been reported recently. We present the cases of 3 consecutive patients affected by AL-type cardiac amyloidosis, symptomatic for heart failure and in sinus rhythm. All patients had a cardiac restrictive pattern at Doppler examination. TEE showed left atrial thrombus in 2 patients and biatrial thrombi in 1 patient; conventional transthoracic echocardiography detected only 1 left atrial thrombus. Our experience confirms the association between cardiac amyloidosis and atrial thrombosis, even in sinus rhythm. TEE should be considered to assess thromboembolic risk in all cases of cardiac amyloidosis with severe diastolic dysfunction.

Atrial thrombi resolution after prolonged anticoagulation in patients with atrial fibrillation.

BACKGROUND: Cardioversion of atrial fibrillation in nonanticoagulated patients may be associated with clinical thromboembolism. Prolonged anticoagulation with warfarin before cardioversion of atrial fibrillation produces a marked reduction of cardioversion-related thromboembolism. The benefit of anticoagulant therapy is generally believed to be due to atrial thrombi organization. PATIENTS AND METHODS: Transesophageal echocardiography (TEE) is highly accurate for diagnosis of atrial thrombi and gives the possibility to serially evaluate the effects of anticoagulant therapy. One hundred twenty-three patients with atrial fibrillation lasting longer than 2 days underwent TEE before cardioversion. An atrial thrombus was identified in 11 patients (9%), and was always confined to the left atrial appendage. TEE was repeated after a median of 4 weeks of oral warfarin. Atrial thrombus had completely resolved in 9 of 11 patients (81.8%; 95% CI, 48.2 to 97.7%); in two patients, clot was still present. No patient had clinical thromboembolism between the two TEE studies. CONCLUSIONS: In the population of our study, a prolonged course of warfarin therapy was associated with resolution of atrial thrombi in the majority of patients. According to these data, the mechanism of thromboembolism reduction with 4 weeks of anticoagulation before cardioversion in patients with atrial fibrillation seems to be related mainly to thrombus lysis rather than organization. Due to the possibility of thrombus persistence even after prolonged anticoagulation, follow-up with TEE before cardioversion is necessary to document thrombus resolution.

Severe left ventricular dynamic outflow tract gradient secondary to localized septal hypertrophy and concomitant acute ischaemic parietal dyssynergy.

Localized basal septal hypertrophy (LSH) is usually an incidental echocardiographic finding and, as opposed to asymmetric hypertrophic cardiomyopathy (AHC), is of no clinical significance. We report a case of a patient with LSH who developed a severe left ventricular outflow gradient during acute myocardial ischaemia, apical akinesis and compensatory hyperkinesis of basal parietal segments.

Irritable bowel syndrome. Still far from a positive diagnosis.

The diagnosis of irritable bowel syndrome requires the exclusion of any associated organic disease: a positive diagnosis would avoid expensive and potentially dangerous diagnostic procedures. A scoring system has been proposed for positive diagnosis where more than 44 points excluded organic digestive disease. The aim of this study was to determine the usefulness of this scoring system in a different setting. Patients (1257) consecutively referred to our medical division were admitted to the study and 270 of these, complaining of abdominal symptoms, were scored on the Kruis system method. The positive predictive value (53.8% for men and 81.5% for women) and the sensitivity (46.7% and 59.5%) did not appear to be adequate. The negative predictive value (91.6% and 87.3%) and the specificity (93.5 and 95.4%) gave higher results, but two cases of neoplasia and nine cases of other organic digestive diseases were not identified or suggested. We believe that this scoring system may be useful only as a first step in a diagnostic flow chart.

Silent cerebral ischemia in patients with chronic atrial fibrillation--a case-control study.

The cerebral CT-scan results of 72 patients with chronic atrial fibrillation (AF) were compared to those of an age- and sex-matched control group, affected by muscle-tensive headache. None of the patients in the study had any neurologic symptoms. All were normal on neurologic examination. Mean age was 68 years in both groups. Patients with atrial fibrillation had a higher prevalence of hypertension, diabetes and hyperlipidemia, although the differences were not significant. Thirty-two patients (44.4%) with AF showed hypodense lesions on cerebral CT-scan, suggestive of small infarcts, whereas this finding was present only in eight control subjects (11.1%) (p less than 0.05). These results confirm in part the observations reported in literature and suggest a more thorough examination of the problem regarding the prophylaxis of thrombo-embolic risk in patients affected by chronic AF.

The influence of cimetidine and ranitidine on the plasma lipid pattern.

The influence of H2-receptor antagonist drugs on the plasma lipid pattern has been studied prospectively in 51 patients treated with cimetidine (26 patients) or ranitidine (25 patients) for gastroenterological diseases. Total and HDL cholesterol and total triglycerides have been measured. Ranitidine did not influence the investigated parameters, while cimetidine produced a significant increase in the HDL cholesterol serum concentration (P = 0.008).

Monitoring and maintenance of treated water quality in the San Juan Lagoons supporting aquaculture; final report of phases I-II

Los objetivos generales del proyecto fueron: determinar la eficiencia de un sistema experimental que utiliza efluentes tratados para la acuacultura controlando las condiciones ambientales de las lagunas para mejorar el crecimiento de los peces; demostrar la viabilidad económica; y evaluar los riesgos a la salud ocasionados por el consumo de los pescados y camarones. Los objetivos principales de la participación del CEPIS fueron: realizar los análisis y evaluar la calidad de los efluentes en relación a los criterios establecidos para la acuacultura; determinar los niveles de pre-tratamiento necesarios para mantener la calidad requerida en las lagunas; monitorear y mantener una adecuada calidad del agua en el pretratamiento y en las lagunas; colaborar en el entrenamiento de investigadores y diseminar información sobre acuacultura con efluentes tratados sin diluir. Presenta los materiales y métodos; resultados; dimensiones; conclusiones. El segundo volumen contiene tablas con los resultados obtenidos

Guía para el manejo de lagunas de estabilización

Muestra generalidades sobre la importancia del tratamiento de aguas residuales, historia y tipos de lagunas de estabilización. Trata sobre su manejo en lo referente a trabajos de supervisión, hidráulicos, de rutina (observaciones de campo y análisis en el sitio) y muestreos. Analiza los trabajos de procesamiento de datos sobre flujos diarios, DBOs y cargas orgánicas semanales, períodos de retención y dispersión, balance mensual de agua. Presenta consideraciones sobre llenado inicial de lagunas, control de olores y limpieza de fondo