Electricity production from municipal solid waste using microbial fuel cells.

The organic content of municipal solid waste has long been an attractive source of renewable energy, mainly as a solid fuel in waste-to-energy plants. This study focuses on the potential to use microbial fuel cells to convert municipal solid waste organics into energy using various operational conditions. The results showed that two-chamber microbial fuel cells with carbon felt and carbon felt allocation had a higher maximal power density (20.12 and 30.47 mW m(-2) for 1.5 and 4 L, respectively) than those of other electrode plate allocations. Most two-chamber microbial fuel cells (1.5 and 4 L) had a higher maximal power density than single-chamber ones with corresponding electrode plate allocations. Municipal solid waste with alkali hydrolysis pre-treatment and K3Fe(CN)6 as an electron acceptor improved the maximal power density to 1817.88 mW m(-2) (~0.49% coulomb efficiency, from 0.05-0.49%). The maximal power density from experiments using individual 1.5 and 4 L two-chamber microbial fuel cells, and serial and parallel connections of 1.5 and 4 L two-chamber microbial fuel cells, was found to be in the order of individual 4 L (30.47 mW m(-2)) > serial connection of 1.5 and 4 L (27.75) > individual 1.5 L (20.12) > parallel connection of 1.5 and 4 L (17.04) two-chamber microbial fuel cells . The power density using municipal solid waste microbial fuel cells was compared with information in the literature and discussed.

Effects of spiked metals on the MSW anaerobic digestion.

This study aimed to investigate the effects of eight metals on the anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) in bioreactors. Anaerobic bioreactors containing 200 mL MSW mixed completely with 200 m L sludge seeding. Ca and K (0, 1000, 2000 and 6,000 mg L(-1)) and Cr, Ni, Zn, Co, Mo and W (0, 5, 50 and 100 mg L(-1)) of various dose were added to anaerobic bioreactors to examine their anaerobic digestion performance. Results showed that except K and Zn, Ca (~728 to ~1,461 mg L(-1)), Cr (~0.0022 to ~0.0212 mg L(-1)), Ni (~0.801 to ~5.362 mg L(-1)), Co (~0.148 to ~0.580 mg L(-1)), Mo (~0.044 to ~52.94 mg L(-1)) and W (~0.658 to ~40.39 mg L(-1)) had the potential to enhance the biogas production. On the other hand, except Mo and W, inhibitory concentrations IC(50) of Ca, K, Cr, Ni, Zn and Co were found to be ~3252, ~2097, ~0.124, ~7.239, ~0.482, ~8.625 mg L(-1), respectively. Eight spiked metals showed that they were adsorbed by MSW to a different extent resulting in different liquid metals levels and potential stimulation and inhibition on MSW anaerobic digestion. These results were discussed and compared to results from literature.

Solubility of heavy metals added to MSW.

This paper aims to investigate the six heavy metal levels (Cd, Cr, Cu, Pb, Ni and Zn) in municipal solid waste (MSW) at different pHs. It intends to provide the baseline information of metals solubility in MSW co-disposed or co-digested with MSW incinerator ashes in landfill or anaerobic bioreactors or heavy metals contaminated in anaerobic digesters. One milliliter (equal to 1mg) of each metal was added to the 100ml MSW and the batch reactor test was carried out. The results showed that higher HNO3 and NaOH were consumed at extreme pH of 1 and 13 compared to those from pH 2 to 11 due to the comparably higher buffer capacity. Pb was found to have the least soluble level, highest metal adsorption (%) and highest partitioning Kd (lg(-1)) between pH 3 and 12. In contrast, Ni showed the highest soluble level, lowest metal adsorption (%) and lowest Kd (lg(-1)) between pH 4 and 12. Except Ni and Cr, other four metals seemed to show the amphibious properties as comparative higher solubility was found in the acidic and basic conditions.

Biostabilization assessment of MSW co-disposed with MSWI fly ash in anaerobic bioreactors.

Municipal solid waste incinerator (MSWI) fly ash has been examined for possible use as landfill interim cover. For this aim, three anaerobic bioreactors, 1.2m high and 0.2m in diameter, were used to assess the co-digestion or co-disposal performance of MSW and MSWI fly ash. Two bioreactors contained ratios of 10 and 20 g fly ash per liter of MSW (or 0.2 and 0.4 g g(-1) VS, that is, 0.2 and 0.4 g fly ash per gram volatile solids (VS) of MSW). The remaining bioreactor was used as control, without fly ash addition. The results showed that gas production rate was enhanced by the appropriate addition of MSWI fly ash, with a rate of approximately 6.5l day(-1)kg(-1)VS at peak production in the ash-added bioreactors, compared to approximately 4l day(-1)kg(-1)VS in control. Conductivity, alkali metals and VS in leachate were higher in the fly ash-added bioreactors compared to control. The results show that MSW decomposition was maintained throughout at near-neutral pH and might be improved by release of alkali and trace metals from fly ash. Heavy metals exerted no inhibitory effect on MSW digestion in all three bioreactors. These phenomena indicate that proper amounts of MSWI fly ash, co-disposed or co-digested with MSW, could facilitate bacterial activity, digestion efficiency and gas production rates.

Experimentally created atrioventricular node reentrant tachycardia in the dog: evidence of a brake system for nodal reentry in the anterior interatrial septum.

OBJECTIVES: The purpose of the study was to investigate the hypothesis that nodal approaches of both anterior and posterior atrial input sites of the atrioventricular (AV) node contribute to part of the circuit of AV node reentrant tachycardia. Thus, tachycardia might be elicited by a premature atrial impulse that arrived at the AV node through one input site while blocked at another. BACKGROUND: Atrioventricular node reentrant tachycardia is the most common supraventricular tachycardia in humans, yet the exact pathway of the reentrant circuit is unknown. METHODS: In eight dogs, an operation that blocked atrial impulses from the anterior input site to the AV node was performed through a right thoracotomy with the inflow occlusion method. The right atrial free wall and the anterior atrial septum between the sinoatrial node and the AV node were completely divided, whereas the tissues within the triangle of Koch remained intact. Thus, atrial impulses were blocked from the anterior input site in the right atrium and the atrial septum and were conducted only through the left atrial free wall to the posterior atrial septum into the AV node. RESULTS: In a baseline electrophysiologic study before operation, dual AV conduction pathways were demonstrated in seven of eight dogs, but none of the seven had inducible AV node reentrant tachycardia. A repeat study 1 week postoperatively revealed that 1) both PR and AH intervals were prolonged during sinus rhythm (p < 0.01); 2) anterograde and retrograde conduction of the AV node showed no significant changes; and 3) AV node reentrant tachycardia was induced in four dogs (50%), of which three had sustained tachycardia. CONCLUSIONS: These results are compatible with the hypothesis that both nodal approaches of atrial input sites of the AV node contribute to part of the circuit of AV node reentrant tachycardia. They also confirm Moe's hypothesis of the existence of a brake system that prevents sustained AV node reentry. Our data suggest that the brake system is located in the anterior atrial septum.

Molecular variant M235T of the angiotensinogen gene is associated with essential hypertension in Taiwanese.

OBJECTIVE: To examine the association of the molecular variants of the angiotensinogen (AGT) gene with essential hypertension in Taiwanese. METHODS: We conducted a case-control study concerning 151 subjects, 102 hypertensives and 49 normotensives. We created a rapid mini-sequencing method based on dye-terminator cycle sequencing to simultaneously detect the M235T and T174M variants of the AGT gene for each subject. RESULTS: The genotype and allele distribution of the M235T variant differed significantly in hypertensives and normotensives (chi 2 = 11.106, P = 0.004 and chi 2 = 6.453, P = 0.011, respectively), whereas those of the T174M variant did not differ (chi 2 = 0.004, P = 0.998 and chi 2 = 0.032, P = 0.858, respectively). The odds ratio for hypertension was 3.64 (95% confidence interval 1.56-8.49) for subjects with the C/C genotype of the M235T variant compared with other genotypes of 2.87 (95% confidence interval 1.76-4.68) for those carrying allele C versus those carrying allele T. CONCLUSION: The molecular variant M235T, but not T174M, of the AGT gene is associated significantly with essential hypertension in this Taiwanese population. The genotype C/C or allele C is a risk factor for hypertension. The underlying mechanism of this association needs to be elucidated further.

Effect of intracoronary verapamil on infarct size in the ischemic, reperfused canine heart: critical importance of the timing of treatment.

In an effort to determine whether the beneficial effect of calcium blocking drugs occurs only during ischemia or during reperfusion as well, anesthetized dogs were subjected to 3 hours of occlusion of the left anterior descending coronary artery followed by 3 hours of reperfusion. In protocol A, intracoronary verapamil (0.01 mg/kg/min) was begun 90 minutes after coronary occlusion and continued for 1 hour into the reperfusion phase (n = 6) while a control group received an infusion of saline solution (n = 6). In vivo area at risk determined by dye injection was 29 +/- 3% of the left ventricle (+/- standard error of the mean) in the control group and 30 +/- 3% in the verapamil group (difference not significant [NS]), whereas the area of necrosis determined by triphenyltetrazolium staining and expressed as a percent of area at risk was smaller in the verapamil group (29 +/- 8%) than in the control group (57 +/- 8%, p less than 0.05). In protocol B, verapamil infusion into the left anterior descending coronary was begun 5 minutes before blood reperfusion and continued throughout the 3-hour reperfusion phase. Area at risk was similar in both groups (control, 25 +/- 1%, n = 8; verapamil, 28 +/- 2%, n = 8, NS); area of necrosis expressed as a percentage of area at risk was 49 +/- 6% in the control group and 45 +/- 10% in the verapamil group (NS). Therefore, calcium blockade of ischemic myocytes delays death and enhances salvage produced by reperfusion. However, calcium blockade begun after prolonged coronary occlusion does not enhance reperfusion-induced myocardial salvage.

Percutaneous balloon pericardiotomy for patients with recurrent pericardial effusion: using a novel double-balloon technique with one long and one short balloon.

Percutaneous balloon pericardiotomy is effective and less invasive for the treatment of recurrent pericardial effusion. This study suggests that the double-balloon method with 1 longer and 1 shorter balloon is the procedure of choice for percutaneous balloon pericardiotomy.

Atrial compartment surgery for chronic atrial fibrillation associated with congenital heart defects.

In three adult patients, two with atrial septal defect and one with Ebstein's anomaly, chronic atrial fibrillation was documented for 13, 21, and 3 years, respectively. Atrial compartment surgery was performed for ablation of the atrial fibrillation concomitant with repair of the cardiac defects. The operation was performed with traditional cardiopulmonary bypass and crystalloid cardioplegia myocardial protection. A U-shaped incision was made in the right atrium: a longitudinal incision 1 cm lateral and parallel to the sulcus terminalis, extending along the borders of the atrial septum to 3 cm (upper margin) and 1 cm (lower margin) distant to the tricuspid anulus. Cryolesions of the atrial isthmus between the upper incision margin and the tricuspid valve anulus were created at -60 degrees C for 180 seconds at a time. After the operation, all three patients had restored and maintained normal sinus rhythm during follow-up periods of 32, 16, and 3 months. Doppler echocardiography detected the recovery of atrial contractility in all three patients. Atrial compartment surgery is a simple and effective method for elimination of chronic atrial fibrillation associated with congenital heart defects.

Lack of association of the angiotensin converting enzyme polymorphism with essential hypertension in a Chinese population.

To examine the association between insertion/deletion (I/D) polymorphism of the angiotensin converting enzyme (ACE) gene and essential hypertension in a Chinese population, a case-control study was conducted using 157 hypertensive and 115 normotensive subjects. The I/D polymorphism of the ACE gene was identified by polymerase chain reaction. Plasma ACE activity was determined using spectrophotometry. The difference of allele frequencies between normotensives and hypertensives was statistically significant (chi 2 = 4.467, P = .035), while the genotype distribution was not different between normotensive and hypertensive subjects (chi 2 = 3.954, P = .138). Plasma ACE activity was highest in the DD genotype, followed by the ID genotype, and the lowest in the II genotype (P = .0001 in normotensives and P = .163 in hypertensives, respectively). Thus, we conclude that the ACE gene polymorphism is not associated with essential hypertension in this Chinese population, but plasma ACE activity is genetically determined in the normotensive Chinese.

Age- and gender-dependent association of the angiotensin-converting enzyme gene with essential hypertension in a Chinese population.

A case-control study was carried out on 272 Chinese subjects over 40 years of age, including 157 hypertensives and 115 normotensives, to examine the association between angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and blood pressure (BP) status. The I/D polymorphism of the ACE gene was identified by polymerase chain reaction. As a whole group, the difference of allele frequencies between normotensives and hypertensives was statistically significant (chi 2 = 4.46, P = 0.03; D/I odds = 1.46), while there was no difference in the genotype distribution (chi 2 = 3.95, P = 0.13). In a subgroup with elderly hypertension (age > 65), the frequencies of D-allele and DD genotype significantly increased (chi 2 = 4.43, P = 0.03 and chi 2 = 4.03, P = 0.08, respectively; D/I odds = 2.28). The association and relative risk increased further in the male gender (chi 2 = 6.65, P = 0.01 and chi 2 = 7.51, P = 0.02 respectively; D/I odds = 4.57 and DD/II odds = 12.00 respectively). The D-allele increased with age in the hypertensives, while the I-allele increased with age in normotensives. Thus, we conclude that the deletion polymorphism of the ACE gene is significantly associated with male elderly hypertension, at least in this Chinese population. This observation, if proved in a larger population, may have some implications for the prevention and treatment strategy for elderly hypertension.

Anatomic substrate of the slow atrio-ventricular nodal pathway in an experimental atrio-ventricular nodal reentrant tachycardia.

We investigated the anatomic substrate of the slow pathway of the atrio-ventricular (AV) node in a dog with AV nodal reentrant tachycardia. Sustained AV nodal reentrant tachycardia was repeatedly induced in a mongrel dog after putting cryolesions on the anterior atrial septum for 1 month. A posterior perinodal dissection was performed for ablation of the slow pathway and cure of the tachycardia. After the operation, AV nodal reentrant tachycardia and discontinuity of the AV conduction were no longer demonstrated. A histologic examination of the AV junction revealed that the dissection injured mainly in two areas: (1) the superficial atrial fibers of the subendocardium over the compact AV node; and (2) the inferior portion of the posterior atrial inputs near the tricuspid annulus. The compact AV node and its transitional cells remained intact. In conclusion, our results suggested that (1) the anatomic circuit of AV nodal reentrant tachycardia does involve some extranodal atrial tissues; and (2) the superficial right atrial fibers over the AV node and/or the inferior portion of the posterior atrial inputs, contribute to part of the slow AV nodal pathway.

Anatomic substrate of the experimentally-created atrioventricular node re-entrant tachycardia in the dog.

Despite major success in the treatment of atrioventricular (AV) node reentrant tachycardia using either catheter ablation or surgery, the morphologic basis underlying AV node reentry is not yet clear. A canine model of AV node reentrant tachycardia was used to examine the histologic features of the reentry circuit. AV node reentrant tachycardia was created in 4 of 8 dogs by a right atrial division which divided the right atrial free wall and the atrial septum into upper and lower portions on a plane between the mid-right atrial free wall and the fossa ovalis. The AV junctional area of all dogs were serially sectioned on a plane that was perpendicular to the AV annulus and the septum. The slices were stained with Masson's trichrome technique. The connections between atrial fibers and the compact AV node and the common AV bundle were examined, and comparison of the histologic features between dogs with and without AV nodal re-entry was made. The histologic examinations showed that, in all dogs, the operation scar was remote from the AV junctional area leaving the Koch's triangle intact. The compact node received its atrial inputs mainly from the anterosuperior and posterior aspects of the Koch's triangle. However, both atrial inputs gave off superficial (subendocardial) fibers that by-passed the compact node to terminate at the base of tricuspid valve. These superficial fibers might function as the proximal link between the dual AV nodal inputs by means of lateral connections. There was no bypass connection between atrial fibers and the common AV bundle. The histologic features of the AV junctional area was not different between dogs with and without AV nodal reentry. In conclusion, AV nodal reentry involves the anterior and posterior atrio-nodal inputs which function as dual AV nodal pathways, and the superficial bypass fibers form the proximal linkage between the two inputs. These structures, together with the compact node, complete the reentry circuit.

Congenital mitral stenosis: challenge of percutaneous transvenous mitral commissurotomy.

A 26-year-old woman with congenital mitral stenosis and embolic stroke was referred to our hospital. The echocardiogram showed a hypoplastic posterior mitral valve leaflet with short, unbalanced chordal attachments to the posteromedial papillary muscle. The mitral valve area was 0.9 cm2 by the pressure half-time method. There was no left atrial thrombus and spontaneous echo contrast. Percutaneous transvenous mitral commissurotomy was performed since the suggestion of surgical management was refused by her family members. A rupture at the chordae tendinae of the hypoplastic posterior papillary muscle developed during the procedure and needed mitral replacement. We advise that percutaneous transvenous mitral commissurotomy be avoided in adult patients with congenital mitral stenosis having an asymmetric and hypoplastic mitral valve.

Reappraisals of atrioventricular node reentrant tachycardia: lessons learned from surgical treatment.

The exact site of reentrant circuit involved in the atrioventricular node reentrant tachycardia was questioned. Seven patients (6 females and 1 male), aged 21 to 64 years (mean = 40 +/- 17 years), with refractory nodal reentry, underwent surgical treatment. The associated cardiac diseases included rheumatic valvar disease in two and an atrial septal defect. Electrophysiologic studies before surgery showed dual nodal pathways in 4 patients. Right atrial endocardial mapping was performed and the earliest retrograde atrial activation during tachycardia was mapped to the apex of the triangle of Koch in 6 patients and near the orifice of coronary sinus in one. Perinodal dissection was performed according to the location of earliest retrograde atrial activity. Care was taken to preserve as much of the atrioventricular node and its arterial supply as was possible. Immediately after surgery, conduction in an antegrade direction recovered and the tachycardia could no longer be reproduced. There was no surgical mortality or morbidity. At 10 to 26 months of follow-up, all patients remain free of tachycardia without antiarrhythmic drugs. Four patients underwent repeated electrophysiologic studies at 2 weeks to 6 months after surgery. Dual nodal pathways were no longer demonstrated. It is concluded that the perinodal atrial tissue plays a part in the atrioventricular nodal reentry, and that surgical dissection is a simple and effective treatment for patients with refractory atrioventricular node reentrant tachycardia.

Circadian variations of atrial natriuretic peptide in normal people and its relationship to arterial blood pressure, plasma renin activity and aldosterone level.

To investigate the circadian variations of plasma atrial natriuretic peptide (ANP) and its relationship to arterial blood pressure, plasma renin activity and aldosterone level, we determined 24-h blood pressure in 14 healthy volunteers. Plasma ANP concentration, renin activity and aldosterone levels were measured every 3 h by radioimmunoassay. We found no significant circadian variation of plasma ANP level (pg/ml) (daytime level, 62 +/- 24 vs. nighttime level, 57 +/- 19, P = 0.146) and plasma renin level (ng/ml/h) (1.32 +/- 0.78 vs. 1.15 +/- 0.57, P = 0.148), but there was diurnal change of blood pressure (mmHg) (systolic, 122 +/- 7 vs. 116 +/- 11, P < 0.001; diastolic, 80 +/- 11 vs. 72 +/- 11, P = 0.025) and plasma aldosterone level (pg/ml) (86 +/- 42 vs. 62 +/- 37, P < 0.001). The blood pressure and aldosterone levels reached maxima (11:00 h and 08:00 h, respectively) before that of ANP (17:00 h) and then decreased together until the nadir at 02:00 h. This might indicate that elevation of arterial blood pressure and plasma aldosterone level stimulate release of ANP under normal physiological conditions.

[Barium intoxication: a case report].

Barium intoxication, a rare cause of hypokalemia, can sometimes result in respiratory paralysis and ventricular tachyarrhythmia. Herein, we report one such case. A 29-year-old man swallowed barium-contaminated fried flour-coated sweet potatoes. Then, abdominal discomfort, vomiting, diarrhea, progressive muscular weakness, apnea and ventricular tachycardia developed and laboratory data revealed profound hypokalemia. He regained his health after mechanical ventilation, anti-arrhythmic agent and aggressive potassium chloride supplement. Analysis of blood, urine and contaminated flour showed the presence of barium carbonate. Barium intoxication is a medical emergency which requires rapid therapy to prevent mortality.

Influence of age on ambulatory blood pressure in treated hypertensive patients with normal casual pressure.

To investigate the influence of age on ambulatory blood pressure monitoring (ABPM) in hypertensive patients whose controlled casual blood pressure was normal, we studied the ABPM in 225 patients, including 122 men and 103 women, aged from 45-74 years. They were classified into three groups: Group A included 93 patients aged 45 to 54 years; Group B included 99 patients, aged 55-64 years; and Group C included 33 patients, aged 65 years and over. The various ABPM data were analyzed and compared among the three groups. The following results were found. The blood pressure (BP) averages for the whole day were normal in all three groups. There was no difference in the systolic BP average among the three groups, but the diastolic BP average declined as age increased. The variability in the systolic BP measurements increased with age. The variability in diastolic BP did not seem to change as conspicuously with age, except for the group C patients who showed a larger variability at nighttime than the other two groups. There were 123 patients (54.7%) with evidence of diurnal change in BP, and the incidence of diurnal change in BP decreased with age. The frequency of abnormally high systolic BP was similar among the three groups, but the frequency of an abnormally high diastolic BP decreased significantly with age. As for the maximal BP levels recorded in the ABPM, group C patients had a higher maximal systolic BP than the other two groups. Therefore, age has a great influence on ABPM in controlled hypertensive patients with normal casual BP.

Implications of an early reversal pattern of body surface potential maps in coronary artery disease.

During early ventricular depolarization, the normal body surface potential map (BSPM) has a maximal potential that is greater than the absolute value of the minimal potential; this reverses in late depolarization, so that the absolute value of the minimal potential is greater. Nevertheless, an abnormal "early reversal" BSPM pattern has been observed in some patients with cardiovascular disease. To investigate the implications of this abnormal pattern, BSPMs were studied in 100 patients with angiographically proven coronary artery disease (CAD). There were 57 patients (57%; group A) with an abnormal early reversal pattern and 43 (43%; group B) without this early reversal pattern. A significant (> 70% narrowing) CAD lesion was observed in a significantly higher proportion of group A (97%) than group B (77%) patients, although the number of involved coronary arteries was not significantly different between the two groups. The maximal extent of the abnormal negative potential was significantly greater in group A (21.2 +/- 9.6 cm2) than in group B (12.2 +/- 7.5 cm2). The abnormal negative potential lasted significantly longer in group A (22.1 +/- 12.1 msec) than in group B (14.4 +/- 9.2 msec). Similarly, the minimal potential lasted significantly longer in group A (20.1 +/- 11.3 msec) than in group B (11.8 +/- 7.1 msec). These findings suggest that the abnormal early reversal BSPM pattern is a valuable indicator of extensive myocardial lesions and the severity of CAD.

Ambulatory blood pressure monitoring for evaluation of long-acting beta-blockers in Taiwan.

This study attempted to evaluate the efficacy of several "long-acting" antihypertensive agents. One-hundred consecutive hypertensive subjects with normal casual blood pressure after once-daily antihypertensive monotherapy treatment were studied. They were divided into three groups: group A, metoprolol (100 mg, daily); group B, atenolol (100 mg, daily); and group C, nadolol (80 mg, daily). Ambulatory blood pressure monitoring (ABPM) was used to evaluate the efficacy of the antihypertensive agents. The overall average ambulatory blood pressures were within the normal limits for all three groups. However, there were some abnormally high blood pressure (BP) readings shown on ABPM. Patients with an abnormally high systolic blood pressure (SBP) average > 140 mmHg accounted for 16.7% of group A, 19.4% of group B and 20% of group C. Those with an abnormally high diastolic blood pressure (DBP) average > 90 mmHg accounted for 16.7%, 19.4% and 10%, respectively, of the corresponding groups. There were no significant differences in the frequency of abnormally high SBP and DBP among the three groups. These "long-acting" antihypertensive drugs did not effectively control BP throughout the entire day. The duration of antihypertensive effect is not necessarily reflected by the blood half-life of the drug. ABPM is an effective way to ascertain the efficacy of "long-acting" hypertensive agents.