Biomedical subjects

D J Lee

Publications and source records attributed to D J Lee.

At least 55 records · Page 3Linked to original sources

PubMed2004

Production of hydrogen and methane from wastewater sludge using anaerobic fermentation.

The hydrogen and methane were produced from wastewater sludge using a Clostridium strain. The original sludge and the pre-treated (acidified, sterilized, freeze/thawed, and sonicated) sludges were tested. Some pre-treatment could enhance hydrogen yield, and the other tests could enhance methane yield. Hydrogen yield followed freeze/thawed>acidified>sterilized>original sludge>sonicated; while methane yield followed sonicated>freeze/thawed>sterilized>acidified>original sludge. The production and consumption of acetate correlated closely with the trends in both yields.

Acetic Acid↗

PubMed2004

Acute and chronic disability among U.S. farmers and pesticide applicators: the National Health Interview Survey (NHIS).

The National Health Interview Survey (NHIS) is a multipurpose household survey of the U.S. civilian non-institutionalized population conducted annually since 1957. From 1986 to 1994, over 450,000 U.S. workers, age 18 years and older, participated in a probability sampling of the entire non-institutionalized U.S. population; variables collected included a range of measures of acute and chronic disability. The objective of the present study was to assess predictors of health status, and acute and chronic disability for farmers and pesticide applicators (pesticide-exposed workers) compared to all other U.S. workers using the 1986-1994 NHIS. After adjustment for sample weights and design effects using SUDAAN, several measures of acute and chronic disability and health status were modeled with multiple logistic regression. Farmers (n = 9576) were significantly older compared to all other U.S. workers (n = 453,219) and pesticide applicators (n = 180). Farmers and pesticide applicators had a higher proportion of males, whites, and Hispanics and were less educated. After adjusting for age, gender, race-ethnicity, and education, compared to all other workers, farmers were significantly less likely to report acute and chronic disability and health conditions, while pesticide applicators were more likely to report chronic disability, health conditions, and poor health. Given the cross-sectional nature of the data and the significant job demands of farming, both leading to a relative healthy worker effect, the present results indicate that at any point in time, farmers report less acute and chronic disability, compared to other U.S. workers, whereas pesticide applicators report similar or poorer health.

Acute Disease↗

PubMed2003

Porosity and interior structure of flocculated activated sludge floc.

This work estimated the porosities of activated sludge flocs, cationic polyelectrolyte flocculated, based on free-settling tests, buoyant weight measurements, and confocal laser scanning microscope (CLSM) tests. The extent of advective flow was estimated based on bubble-tracking test. The former two measurements suggested a close-to-unity porosity, that is, an extremely void floc interior. Meanwhile, the latter two tests recommended a dense floc interior with a porosity less than 64%. A discrepancy exists between the porosities estimated by various tests. A floc model was proposed based on the understanding that a vast amount of bound water in the floc was regarded as void in buoyant weight measurement, but was impermeable for advective flow. The distribution rather than the mean value of the porosity controls the advective flow. There existed no simple correlation between the porosities measured by different tests.

Journal Article↗

PubMed2003

Hydrodynamic drag force exerted on activated sludge floc at intermediate Reynolds number.

We hung the activated sludge flocs on an elastic nylon stick and then subjected it to a uniform water flow and measured its displacement. The hydrodynamic drag force exerted on the floc was subsequently estimated, both for cationic flocculated flocs and for flocculated and then frozen/thawed flocs. A confocal laser scanning microscope (CLSM) was employed to probe the interior structure of flocs. Polyelectrolyte flocculation leads to a compact global structure, and hence high drag force exerted on the floc by water. The corresponding C(D)Omega value at Re=12-27 for flocs ranges from 1.58 to 3.61. Fast freezing would little affect the hydrodynamic drag force. Slow freezing, in contrast, considerably consolidated the floc structure and hence presented impermeable sphere-like behavior of the slowly frozen/thawed flocs.

Journal Article↗

PubMed2003

Producing hydrogen from wastewater sludge by Clostridium bifermentans.

Excess wastewater sludge collected from the recycling stream of an activated sludge process is biomass that contains large quantities of polysaccharides and proteins. However, relevant literature indicates that the bio-conversion of wastewater sludge to hydrogen is limited and therefore not economically feasible. This work examined the anaerobic digestion of wastewater sludge using a clostridium strain isolated from the sludge as inoculum. A much higher hydrogen yield than presented in the literature was obtained. Also, the effects of five pre-treatments-ultrasonication, acidification, sterilization, freezing/thawing and adding methanogenic inhibitor-on the production of hydrogen were examined. Freezing and thawing and sterilization increased the specific hydrogen yield by 1.5-2.5 times to that of untreated sludge, while adding an inhibitor and ultrasonication reduced the hydrogen yield.

Anaerobiosis↗

PubMed2003

Outcome of salvage total laryngectomy following organ preservation therapy: the Radiation Therapy Oncology Group trial 91-11.

OBJECTIVE: To evaluate the incidence of morbidity, mortality, and disease control for patients requiring salvage total laryngectomy (TL) following organ preservation therapy. DESIGN: Patients entered into a 3-arm randomized prospective multi-institutional trial for laryngeal preservation who required TL following initial treatment. SETTING: The Radiation Therapy Oncology Group 91-11 trial for laryngeal preservation. PATIENTS: From 1992 to 2000, 517 evaluable patients were randomized to receive chemotherapy followed by radiation therapy (arm 1), concomitant chemotherapy and radiation therapy (arm 2), or radiation therapy alone (arm 3). RESULTS: Overall, TL was required in 129 patients. The incidence was 28%, 16%, and 31% in arms 1, 2, and 3, respectively (P =.002). Of these, 7 patients (5%) required TL for aspiration or necrosis. Following TL, the incidence of major and minor complications ranged from 52% to 59% and did not differ significantly among the 3 arms. Pharyngocutaneous fistula was lowest in arm 3 (15%) and highest in arm 2 (30%) (P>.05). There was 1 perioperative death. Local-regional control following salvage TL was 74% for arms 1 and 2 and 90% for arm 3. At 24 months, the overall survival was 69% (arm 1), 71% (arm 2), and 76% (arm 3) (P>.73). CONCLUSIONS: Laryngectomy following organ preservation treatment is associated with acceptable morbidity. Perioperative mortality is low but up to one third of patients will develop a pharyngocutaneous fistula. Local-regional control is excellent for this group of patients. Survival following salvage TL was not influenced by the initial organ preservation treatment.

Carcinoma, Squamous Cell↗

PubMed2003

Gravitational sedimentation of flocculated waste activated sludge.

The sedimentation characteristics of flocculated wastewater sludge have not been satisfactorily explored using the non-destructive techniques, partially owing to the rather low solid content (ca. 1-2%) commonly noted in the biological sediments. This paper investigated, for the first time, the spatial-temporal gravitational settling characteristics of original and polyelectrolyte flocculated waste activated sludge using Computerized Axial Tomography Scanner. The waste activated sludge possessed a distinct settling characteristic from the kaolin slurries. The waste activated sludges settled more slowly and reached a lower solid fraction in the final sediment than the latter. Flocculation markedly enhanced the settleability of both sludges. Although the maximum achievable solid contents for the kaolin slurries were reduced, flocculation had little effects on the activated sludge. The purely plastic rheological model by Buscall and White (J Chem Soc Faraday Trans 1(83) (1987) 873) interpreted the consolidating sediment data, while the purely elastic model by Tiller and Leu (J. Chin. Inst. Chem. Eng. 11 (1980) 61) described the final equilibrated sediment. Flocculation produced lower yield stress during transient settling, thereby resulting in the more easily consolidated sludge than the original sample. Meanwhile, the flocculated activated sludge was stiffer in the final sediment than in the original sample. The data reported herein are valuable to the theories development for clarifier design and operation.

Flocculation↗

PubMed2003

Using filtrate of waste biosolids to effectively produce bio-hydrogen by anaerobic fermentation.

Waste biosolids collected from sewage works is a biomass containing a vast amount of polysaccharides and proteins, and thus is considered a potential substrate for producing hydrogen using anaerobic fermentation. This work demonstrated, contrary to the common assumption, that the solids phase in waste activated biosolids presents extra nutrients for anaerobes; it in fact prohibits effective bio-hydrogen production. Using filtrate after removal of solids from biosolids produces more hydrogen than using the whole biosolids, with the former reaching a level an order of magnitude higher than the literature results.

Bacteria, Anaerobic↗

PubMed2003

Anaerobic digestion of polyelectrolyte flocculated waste activated sludge.

This work examined how adding one of three polyelectrolyte flocculants (T3052: cationic, T2000: non-ionic, and T1052: anionic) affected the anaerobic digestion of wastewater sludge. Methane production, floc characteristics (morphology and zeta-potential) and process parameters (soluble chemical oxygen demands (SCODs) and reductive potentials) were monitored along the digestion tests. The digestion rates of T2000- and T1052-conditioned sludge resembled that for original sludge. The T3052-flocculated sludge generated methane at a higher rate during the first 6 days of digestion than did the original one. In the following stage, the digestion rate of sludge flocculated with T3052 at dosage exceeding 15 g/kg dried solids declined. For example, at 40 days of digestion the methane production amounts for original, 15 g/kg DS flocculated, and 40 g/kg flocculated sludge were of 136, 105, and 85 g/kg DS, respectively. The role of flocculants could change in different stages of digestion. The dosed polymers had no apparent toxicity to the inoculum used. The changes in SCOD, adenosintriphosphate concentrations, oxidative and reductive potential, and zeta-potentials did not correlate with the noted hindered digestion for T3052-conditioned sludge. Microphotographic observation revealed that the flocs of T3052-conditioned sludge were not only of a large size, but also were resistant to structural deterioration during digestion. Therefore, mass transfer resistance was proposed to account for the hindered digestion efficiency observed for T3052-conditioned sludge.

Anaerobiosis↗

PubMed2003

Hydrogen production from wastewater sludge using a Clostridium strain.

Limited data in literature revealed a relatively low hydrogen yield from wastewater sludge, ca. 0.16 mg/g-dried solids, using anaerobic fermentation. We demonstrated in this work a much higher hydrogen yield, around 1.1 mg-H2/g-dried solids using a clostridium strain isolated from the sludge sample. The formed hydrogen would be consumed after passing the peak value at around 30-36 h of fermentation. We examined the effects of employing five different pre-treatments on substrate sludge, but noted no appreciable enhancement in hydrogen yield as commonly expected for methane production. Since a vast amount of organic matters had been released to water after hydrogen fermentation, we externally dosed methanogenic bacteria to the fermented liquor to produce methane. The fermented liquor could produce more methane than the non-fermented sample, indicating that the dosed methanogenic bacteria readily utilized the organic matters derived from the fermentation test.

Bioelectric Energy Sources↗

PubMed2003

Effects of dietary electrolyte balance on the chemistry of blood and urine in lactating sows and sow litter performance.

One hundred fifty-three sows (average parity of 2.2) were used to determine the effects of dietary electrolyte balance (calculated as mEq/kg of diet for Na + K - Cl) on sows and their litters during lactation. The sows were fed corn-soybean meal-based diets (1.0% lysine, 1.0% valine, 0.95% Ca, and 0.80% P; as-fed basis) starting on d 109 of gestation and throughout the 21-d lactation experiment. Dietary electrolyte balance (dEB) was 0, 100, 200, 350, and 500 mEq/kg (as-fed basis), well above and below the dEB of 185 mEq/kg found in a simple corn-soybean meal-based lactation diet. To achieve the desired dEB, diets had the following: 1) 1.8% HCl (6 N) and 1.06% CaCl2, 2) 1.0% CaCl2, 3) 0.04% NaHCO3, 4) 1.29% NaHCO3, and 5) 2.54% NaHCO3 (as-fed basis). Increasing dEB increased blood pH (linear and quadratic effects, P < 0.001), partial pressure of carbon dioxide (linear effect, P < 0.001), HCO3- concentration (linear and quadratic effects, P < 0.001), and blood base excess (linear and quadratic effects, P < 0.001). However, increased dEB resulted in lower blood concentrations of K (linear and quadratic effects, P < 0.04), Cl (linear and quadratic effects, P < 0.001), and ionized Ca (linear and quadratic effects, P < 0.001). Changing dEB did not affect ADFI; water usage, litter weight gain; sow weight change; sow backfat change; percentages of CP, lactose, and fat in the milk; percentage of sows returning to estrus; days to estrus; and number of pigs born alive in the subsequent litter (P = 0.06). However, piglet survivability to d 10 and overall was greatest with the lower dEB treatments (linear effect, P < 0.05). The pH (linear and quadratic effects, P < 0.001) and colony forming units of total bacteria (linear effect, P < 0.03) in the urine increased as dEB of the diet was increased. In conclusion, dEB had pronounced effects on the physiological status of sows and decreasing dEB below that in a simple corn-soybean meal-based diet decreased bacterial counts in the urine and increased piglet survivability. However, milk composition, sow and litter weights at weaning, and subsequent rebreeding performance of the sows were not affected by dEB.

Animal Feed↗

PubMed2003

Coagulation of humic-kaolin-PACI aggregates.

Water treatment residual flocs are fractal-like aggregates made of many initial aggregates. We investigated in this study the coagulation dynamics for the humic-mineral-polyaluminium chloride (PACI) aggregates using small-angle light scattering techniques and the free-settling test. In contrast to reports in the literature, the presence of humic acid did not lead to a loose floc. Not only the time evolution of the coagulation dynamics, but also the final floc characteristics are only mildly affected by the humic acid. However, the strength of the formed floc does decline with humic acid, which leads to a turbid supernatant with high level of organics.

Aluminum Hydroxide↗

PubMed2003

Manufacturing artificial aggregates from industrial sludge and marine clay with addition of sodium salt.

The potential of converting industrial sludge and dredged marine clay into building and construction materials as an alternative to disposal was investigated in this study. The industrial sludge was mixed with marine clay at various compositions and was shaped into round pellets to be used as concrete aggregates. The pellets were then dried and transferred into a high temperature kiln where they were heated at 1,135 degrees C. The artificial aggregates were more porous then the normal granite aggregate. The occurrence of this condition was suspected to be attributed to two factors, viz. the firing temperature and the amount of sodium in the aggregates. To validate this hypothesis, the aggregates with and without added sodium chloride were fired at temperatures of 1,100 and 1, 200 degrees C. Results showed a reduction in the densities of the aggregates with the addition of sodium chloride and the increase in firing temperature.

Aluminum Silicates↗

PubMed2003

Adsorption of heavy metals from water using banana and orange peels.

Liquid-phase adsorption removal of Cu2+, Co2+, Ni2+, Zn2+, and Pb2+ in the concentration range of 5-25 mg/L using low-cost banana and orange peel wastes was examined at 30 degrees C. Under comparable conditions, the amount of adsorption decreased in the order Pb2+ > Ni2+ > Zn2+ > Cu2+ > Co2+ for both adsorbents. The adsorption isotherms could be better described by the Freundlich equation. The amount of adsorption increased with increasing pH and reached a plateau at pH > 7, which was confirmed by the variations of zeta potentials. The application potential of such cellulose-based wastes for metal removal (up to 7.97 mg Pb2+ per gram of banana peel at pH 5.5) at trace levels appeared to be promising.

Adsorption↗

PubMed2003

Observations of blanket characteristics in full-scale floc blanket clarifiers.

We monitored the changes in concentrations, zeta potentials, sizes and capillary suction times of the solids flocs in the clarified water from eight floc blanket clarifiers of PingTsan Water Works of Taiwan Water Supply Company with low (< 10 NTU) and high (> 100 NTU) turbidity raw water. For the former, one-stage coagulation-sedimentation treatment was adopted which yielded a rather unstable blanket. Complete washout was noticeable when the PACl dosage was insufficient. On the treatment of high-turbidity raw water, on the other hand, the Works adopted the combined treatment process, that is, the raw water was first coagulated and settled in a pre-sedimentation tank, afterwards, its effluent was coagulated again and clarified in the clarifiers. The resulting flocs could form a networked blanket that was relatively stable to the shock load in raw water turbidity.

Bioreactors↗

PubMed2002

Multilevel structure of sludge flocs.

In this work, the structure of two kaolin sludges and a waste activated sludge are investigated using both light-scattering and free-settling methods. Fractal dimensions estimated by the light-scattering and free-settling techniques (D(S) and D(F) respectively) differ significantly and support the hypothesis that naturally occurring aggregates possess a multilevel structure. A two-level floc structural model comprised of (i) a primary floc (of fractal dimension D(S)) consisting of primary particles and (ii) a secondary floc (of fractal dimension D(F)) consisting of the microflocs is proposed to interpret the experimental findings. The structural changes of sludge flocs before and after cationic flocculation are interpreted using the proposed two-level model.

Journal Article↗

PubMed2002

Advective flow and floc permeability.

This work monitored advection flow through a floc by bubble tracking. Close examination of the motion of a swarm of hydrogen bubbles that passed over a free-falling floc allowed the extent of advection flow to be estimated at 53% for the original activated sludge floc, and 12% for the flocculated floc. The interior permeability of the sludge flocs was estimated from this information. The fluid force exerted on the falling floc was also considered.

Journal Article↗

PubMed2002

Finite element analysis of slow drug release through deformed coating film: effects of morphology and average thickness of coating film.

This paper, a continuation of our previous work, is a presentation of the effect of the morphology and the average thickness of the deformed coating films on the slow diffusional release characteristics analyzed numerically under the constraints of the constant volume of the drug matrices and the coating films, if the films have the same average thickness. Increasing the average thickness of the coating films slows down the fractional release and the average release rate of the drug and smoothen the initial burst of the drug, as well as increase the initial lag time. The effect due to deformation of the coating films on these diffusional release characteristics are found to be less significant with the increasing average thickness of the coating films. Interestingly initial lag times are found to be the same for the coated particles having the same smallest thickness but different average thickness of coating films. The effect due to the change in the average thickness of the coating films on the characteristics of the slow controlled-release is discussed to shed light on the design of a better controlled-release device.

Algorithms↗