Fate of nitrogen species in nitrate reduction by nanoscale zero valent iron and characterization of the reaction kinetics

This study investigates the fate of nitrogen species during nitrate reduction by nanoscale zero valent iron (NZVI) as well as the related kinetics. The NZVI used for the experiments was prepared by chemical reduction without a stabilizing agent. The pseudo first order kinetic constant of nitrate reduction at 30 degrees C with an NZVI/nitrate ratio of 1.25:1, which were the reference conditions of this study, was 4.08 h(-1) (R(2)=0.955). A nitrogen mass balance was established by quantitative analysis of aqueous-phase and gas-phase nitrogen species. The results confirm that the nitrate was converted to ammonium ion, that ammonia stripping subsequently occurred under a strong alkaline condition, and that the total amount of aqueous nitrogen was consequently reduced. The nitrate reduction rate also increased with a lower pH and a higher temperature when microscale ZVI was used. However, in contrast to the reaction by microscale ZVI, the nitrate reduction rate by NZVI was higher for an unbuffered condition, possibly due to the abundance of surface atoms and the smaller size.

Conversion of single-crystalline C60 nanodisks and nanorods into graphitic nanostructures via hydrogen thermal annealing

We have developed a process to convert C(60) nanostructures into graphitic nanostructures. Disk-shaped and wire-shaped C(60) nanostructures synthesized by the liquid-liquid interfacial precipitation method, the vapor-solid process, and solvent evaporation were successfully converted into graphitic structures by thermal annealing in hydrogen at 900 degrees C. Scanning electron and tunneling electron microscopic studies confirmed that the converted nanostructures were composed of multi-graphitic structures such as multi-walled carbon nanotubes, carbon nanofibers, and carbon onions. Fourier transform Raman spectroscopy and conductance measurements were carried out to further confirm the successful formation of graphitic layers. In the Raman spectra, the nanostructures converted from C(60) disks showed signature D, G, and G(') bands of graphitic structures, while the A(g) mode (1469 cm(-1)) of the original C(60) molecule disappeared. C(60) nanowire devices fabricated for the conductance measurements of the converted structures showed dramatically decreased resistance (R approximately 100 kOmega) compared to the pristine C(60) wire (R>100 MOmega). Further manipulation of the reaction environment, including the gas and the annealing temperature, may reveal a new way to attain diverse graphitic nanostructures economically.

Interaction of nitric oxide and renin angiotensin system in pulmonary arterial circulation of RHR

We investigated the interaction between nitric oxide and the renin angiotensin system in regulating isolated pulmonary arterial tension and pulmonary arterial pressure (PAP) in renal hypertensive rats (RHR) made by complete ligation of left renal artery. Losartan induced a depressor response that was smaller in RHR than in normotensive rats (NR) (3.3 and 7.0 mmHg, respectively, at 3.0 mg/kg, p<0.05), and the response was significantly reduced by N(G)-nitro-L-arginine methyl ester (L-NAME). Angiotensin II elevated the PAP (7.6 and 10.8 mmHg at 0.1 mug/kg; 20.3 and 23.6 mmHg at 1.0 mug/kg, respectively) and contracted the isolated pulmonary artery (pD(2): 8.79 and 8.71, respectively) from both NR and RHR with similar magnitude, and these effects were significantly enhanced by L-NAME in NR, but not in HRR. Acetylcholine lowered the PAP slightly less effectively in RHR than in NR (3.8 and 6.0 mmHg at 10 mug/kg, respectively) and relaxed the pulmonary artery precontracted with norepinephrine in both rats with similar magnitude (E(max): 60.8 and 63.6%, respectively), and the effect being completely abolished after pretreatment with L-NAME or removal of endothelial cells. These results suggest that nitric oxide interacts with renin angiotensin system to control the pulmonary vascular tension and pulmonary arterial circulation of RHR.

Enzymatic Hydrolysis of Heated Whey: Iron-Binding Ability of Peptides and Antigenic Protein Fractions

This study evaluated the influence of various enzymes on the hydrolysis of whey protein concentrate (WPC) to reduce its antigenic fractions and to quantify the peptides having iron-binding ability in its hydrolysates. Heated (for 10 min at 100 degrees C) WPC (2% protein solution) was incubated with 2% each of Alcalase, Flavourzyme, papain, and trypsin for 30, 60, 90, 120, 150, 180, and 240 min at 50 degrees C. The highest hydrolysis of WPC was observed after 240 min of incubation with Alcalase (12.4%), followed by Flavourzyme (12.0%), trypsin (10.4%), and papain (8.53%). The nonprotein nitrogen contents of WPC hydrolysate followed the hydrolytic pattern of whey. The major antigenic fractions (beta-lactoglobulin) in WPC were degraded within 60 min of its incubation with Alcalase, Flavourzyme, or papain. Chromatograms of enzymatic hydrolysates of heated WPC also indicated complete degradation of beta-lactoglobulin, alpha-lactalbumin, and BSA. The highest iron solubility was noticed in hydrolysates derived with Alcalase (95%), followed by those produced with trypsin (90%), papain (87%), and Flavourzyme (81%). Eluted fraction 1 (F-1) and fraction 2 (F-2) were the respective peaks for the 0.25 and 0.5 M NaCl chromatographic step gradient for analysis of hydrolysates. Iron-binding ability was noticeably higher in F-1 than in F-2 of all hydrolysates of WPC. The highest iron contents in F-1 were observed in WPC hydrolysates derived with Alcalase (0.2 mg/kg), followed by hydrolysates derived with Flavourzyme (0.14 mg/kg), trypsin (0.14 mg/kg), and papain (0.08 mg/kg). Iron concentrations in the F-2 fraction of all enzymatic hydrolysates of WPC were low and ranged from 0.03 to 0.05 mg/kg. Fraction 1 may describe a new class of iron chelates based on the reaction of FeSO4 x 7 H2O with a mixture of peptides obtained by the enzymatic hydrolysis of WPC. The chromatogram of Alcalase F-1 indicated numerous small peaks of shorter wavelengths, which probably indicated a variety of new peptides with greater ability to bind with iron. Alcalase F-1 had higher Ala (18.38%), Lys (17.97%), and Phe (16.58%) concentrations, whereas the presence of Pro, Gly, and Tyr was not detected. Alcalase was more effective than other enzymes at producing a hydrolysate for the separation of iron-binding peptides derived from WPC.

Taste and odour issues in South Korea's drinking water industry

This paper reviews taste and odour (T&O) issues of South Korea's water industry. For this purpose, an overview of the water supply systems and drinking water standards is presented and some results from citizen surveys for customer satisfaction are included. A case study is presented in which the water intake was shifted from inside a main reservoir to a downstream location due to T&O problems. It is true that the South Korean water industry has long relied on the tolerance of consumers for periodic T&O events. Recently the South Korean water industry has become aware that the T&O problems are at the centre of consumers' concerns and has taken several positive approaches. These include monitoring T&O events using sensory and instrumental methods, installation of a baffled-channel PAC contactor and application of advanced water treatment processes.

Effect of condensate of food waste (CFW) on nutrient removal and behaviours of intercellular materials in a vertical submerged membrane bioreactor (VSMBR)

The main objective of this study was to investigate the effect of condensate of food waste (CFW) on nutrient removal in a pilot-scale vertical submerged membrane bioreactor (VSMBR) treating municipal wastewater having total-chemical oxygen demand to total-nitrogen ratio (T-COD/T-N) of 5.5. In this reactor, the average removal efficiencies of T-COD, T-N, and T-P (total-phosphorus) were 96%, 74%, and 78%, respectively at 8-h hydraulic retention time (HRT), 60-day sludge retention time (SRT), and internal recycle rate of 400%. As the CFW was supplemented with 0.86% of the influent flow rate, the T-N and T-P removal efficiencies increased to 81% and 91%, respectively. Accordingly, in batch tests, it was concluded that the supply of CFW improved enhanced biological phosphorus removal (EBPR) activity of microorganisms resulting in improvement of nutrient removal efficiency. Under this condition, several kinds of poly-hydroxyalkanoates (PHAs) were detected inside the cells.

Development of an innovative vertical submerged membrane bioreactor (VSMBR) for simultaneous removal of organic matter and nutrients

A novel vertical submerged membrane bioreactor (VSMBR) composed of anoxic and oxic zones in one reactor was developed in an attempt to reduce the problems concerning effective removal of pollutants from synthetic wastewater including glucose as a sole carbon source as well as membrane fouling. The optimal volume ratio of anoxic zone/oxic zone was found as 0.6. The desirable internal recycle rate and hydraulic retention time (HRT) for effective nutrient removal were 400% and 8h, respectively. Under these conditions, the average removal efficiencies of total nitrogen (T-N) and total phosphorus (T-P) were 75% and 71%, respectively, at the total chemical oxygen demand (T-COD)/T-N ratio of 10. In addition, the VSMBR showed high specific removal rates of nitrogen and phosphorus while the biomass growth yield from the reactor was about 20% of the conventional activated sludge process.

Simultaneous treatment of sewage sludge and food waste by the unified high-rate anaerobic digestion system

This study aimed to evaluate the performance of the unified high-rate anaerobic digestion (UHAD) system treating co-substrate of sewage sludge and food waste. A 24-hr operating sequence consisted of four steps including fill, react, settle, and draw. The effects of co-substrate and organic loading rate (OLR) on the performance were investigated to verify the system applicability. In each OLR, the UHAD system showed higher CH4 recovery (> 70%), CH4 yield (0.3 L CH4/g VSadded) and CH4 production rate (0.6 L CH4/L/d) than the control system. In the specific methanogenic activity (SMA) tests on thermophilic biomass of the UHAD system, the average SMA of acetate (102 mL CH4/gVSS/d) was much higher than those of butyrate (85 mL CH4/g SS/d) and propionate (42 mL CH4/gVSS/d). It was demonstrated that the UHAD system for co-digestion resulted in higher methane yield and methane production rate due to sequencing batch operation, thermophilic digestion, and co-digestion. The enhanced performance could be attributed to longer retention time of active biomass, faster hydrolysis, higher CH4 conversion rate, and balanced nutrient conditions of co-substrate in the UHAD system. Consequently, this optimized unification could be a viable option for the simultaneous treatment of two types of OFMSW with high stability.

Effects of influent COD/N ratio and internal recycle ratio on nitrogen removal efficiency in the KNR process

In this study, with the KNR process that has many advantages, the nitrogen removal efficiency of KNR was experimentally investigated at various COD/N ratios of influent conditions. The optimal operating condition of internal recycle ratio was evaluated. The TN removal efficiencies were 59.1, 72.5 and 75.9% at the COD/N ratios of 3, 5 and 7, respectively. These high removal efficiencies resulted from high denitrification rate in UMBR with high microorganism concentration. Furthermore, specific endogenous denitrification at MLVSS of 10.3 g/L that is similar to MLVSS in UMBR was over two times higher than that at MLVSS of 2.06 g/L. This result suggests that endogenous denitrification rate in UMBR is so high that the requirement of an external carbon source can be saved. As the internal recycle ratio increased from 100 to 400%, the TN removal efficiency also improved from 69.5 to 82.9%, and the optimal internal recycle ratio was 300%.

Modeling of extracellular polymeric substances and soluble microbial products production in a submerged membrane bioreactor at various SRTs

Extracelluar polymeric substances (EPSs) and soluble microbial products (SMPs) produced by microbial cultures involved in membrane biofouling have been widely investigated. A mathematical model of EPS and SMP formation and degradation was established based on the activated sludge model no. 1 (ASM1) and was applied to the membrane bioreactor sludge with different sludge retention times (SRTs). The unified theory that the distinct products from the EPS and SMP overlapped each other was integrated into the ASM1. Two components, five processes and eight parameters were newly added to set up the model. To increase the accuracy of model simulation, microbial kinetic parameters were determined by respirometry method and applied to the model instead of microbial kinetic constant offered in ASM1. From the respirometry result, both of heterotroph and autotroph showed different yield value, growth rate and decay rate from activated sludge. There was no significant effect of SRT on SMP production and the experimental results showed good agreement with the predicted values by the model simulation. With the developed unified EPS and SMP model, EPS and SMP production could be simulated so well that it can be applied for the membrane biofouling control.

Single cell protein production of Euglena gracilis and carbon dioxide fixation in an innovative photo-bioreactor

The biological fixation using microalgae has been known as an effective and economical carbon dioxide reduction technology. Carbon dioxide (CO2) fixation by microalgae has been shown to be effective and economical. Among various algae, a species Euglena gracilis was selected as it has advantages such as high protein content and high digestibility for animal feed. A kinetic model was studied in order to determine the relationship between specific growth rate and light intensity. The half-saturation constant for light intensity in the Monod model was 178.7 micromol photons/m2/s. The most favorable initial pH, temperature, and CO2 concentration were found to be 3.5, 27 degrees C, and 5-10% (vol/vol), respectively. Light intensity and hydraulic retention time were tested for effects on cell yield in a laboratory-scale photo-bioreactor of 100l working volume followed by semi-continuous and continuous culture. Subsequently, an innovative pilot-scale photo-bioreactor that used sunlight and flue gas was developed to increase production of this bioresource. The proposed pilot-scale reactor showed improved cell yield compared with the laboratory-scale reactor.

Pilot-scale two-stage process: a combination of acidogenic hydrogenesis and methanogenesis

This study was performed to optimize both acidogenic hydrogenesis and methanogenesis, and then to develop a pilot-scale two-stage process producing not only CH4 but also H2. Firstly, acidogenic hydrogenesis of food waste was examined in pilot-scale leaching-bed reactors using dilution rate (D) as a tool to improve the environmental conditions. The maximum efficiency of 71.4% was obtained by adjusting D from 4.5 to 2.5 d(-1) depending on the state of degradation. Secondly, the wastewater from acidogenic hydrogenesis was converted to CH4 in a pilot-scale UASB reactor. The COD removal efficiency exceeded 95% up to the loading rates of 13.1 g COD/Ld, which corresponded to HRT of 0.25 d (6 h). Lastly, a pilot-scale two-stage process was devised based on a combination of acidogenic hydrogenesis and methanogenesis. Over 120 days, the pilot-scale process resulted in large VS reduction of 70.9% at the high loading rate of 12.5 kg VS/m3/d in a short SRT of 8 days.

Effect of internal recycle rate on the high-strength nitrogen wastewater treatment in the combined UBF/MBR system

An anaerobic/aerobic system combining an anaerobic upflow-sludge bed filter (UBF) and an aerobic membrane bioreactor (MBR) was operated to enhance organic and nitrogen removal efficiency. The internal recycle rate, which is one of the most important operation factors that affects overall removal efficiency, was varied from 100% to 300% of the influent flow. Under these conditions, the overall removal efficiencies of organic and nitrogen and characteristics of membrane fouling in the combined system treating the synthetic wastewater including high concentration of organics and nutrients were studied. As a result, nitrogen removal efficiency was increased to 67% when the internal recycle rate was 300% of influent flow rate. As the internal recycle ratio increased from 100% to 200%, protein content decreased by 17% and carbohydrate content increased by 12%. However, there was no remarkable difference in total extracellular polymeric substances (EPS) content. At the high recycle rate of 300%, the surface charge of sludge was decreased while hydrophobicity (specific ultraviolet absorbance, SUVA) was increased. The differences in SUVA and surface charge were 11% and 1%, respectively. It is concluded that SUVA and EPS composition were important parameters affecting membrane fouling in the combined system.

Simultaneous removal of organic and strong nitrogen from sewage in a pilot-scale BNR process supplemented with food waste

As the sewerage system is incomplete, sewage in Korea lacks easily biodegradable organics for nutrient removal. In this country, about 11,400 tons of food waste of high organic materials is produced daily. Therefore, the potential of food waste as an external carbon source was examined in a pilot-scale BNR (biological nutrient removal) process for a half year. It was found that as the supply of the external carbon increased, the average removal efficiencies of T-N (total nitrogen) and T-P (total phosphorus) increased from 53% and 55% to 97% and 93%, respectively. VFAs (volatile fatty acids) concentration of the external carbon source strongly affected denitrification efficiency and EBPR (enhanced biological phosphorus removal) activity. Biological phosphorus removal was increased to 93% when T-N removal efficiency increased from 78% to 97%. In this study, several kinds of PHAs (poly-hydroxyalkanoates) in cells were observed. The observed PHAs was composed of 37% 3HB (poly-3-hydroxybutyrate), 47% 3HV (poly-3-hydroxyvalerate), 9% 3HH (poly-3-hydroxyhexanoate), 5% 3HO (poly-3-hydroxyoctanoate), and 2% 3HD (poly-3-hydroxydecanoate).

Anaerobic co-digestion of sewage sludge and food waste using temperature-phased anaerobic digestion process

This study was performed to overcome the low efficiency of anaerobic digestion of sewage sludge and food waste by combining temperature-phased digestion, sequencing batch operation, and co-digestion technology. It was demonstrated that the temperature-phased anaerobic sequencing batch reactor (TPASBR) system for the co-digestion of sewage sludge and food waste resulted in enhanced volatile solids (VS) reduction and methane production rate. At the organic loading rate (OLR) of 2.7 g VS/l/d, the TPASBR system showed the higher VS reduction (61.3%), CH4 yield (0.28 l/g VS(added)) and CH4 production rate (0.41 l CH4/l/d) than those (0.29 l CH4/l/d) of the mesophilic two-stage ASBR (MTSASBR). In the specific methanogenic activity (SMA) tests on thermophilic biomass of the TPASBR system, the average SMA of acetate (93 ml CH4/gVSS/d) was much higher than those of propionate (46 ml CH4/g VSS/d) and butyrate (76 ml CH4/g VSS/d). Also, higher specific hydrolytic activity (SHA, 217 mg COD/g VSS/d) of the biomass supported fast hydrolysis under thermophilic conditions. The track study revealed that the most active period of the 24 h cycle was between 6 and 12 h. The enhanced performance of the TPASBR system could be attributed to longer solids retention time, fast hydrolysis, higher CH4 conversion rate, and balanced nutrient condition of co-substrate. It was verified that this combination could be a promising and practical alternative for the simultaneous recycling of two types of organic fraction of municipal solid waste (OFMSW) with high stability.

Characteristics of granular sludge in a single upflow sludge blanket reactor treating high levels of nitrate and simple organic compounds

Simultaneous denitrification and methanogenesis were accomplished in a single upflow sludge blanket (USB) reactor. More than 99% and 95% of nitrate and chemical oxygen demand (COD) removal rates were obtained at a loading of 600 mg NO3-N/L x d and 3,300 mg COD/L x d, respectively. The specific denitrification rate (SDR) increased as COD/NO3-N ratios decreased. Maximum SDR with acetate could reach 1.05 g NO3-N/gVSS x d. Significant sludge flotation was observed at the top of the reactor due to the change of microbial composition and the formation of hollow granules. Granules became fluffy and buoyant due to the growth of denitrifiers. Microscopic examination showed that granules exhibited layered structure and they were mainly composed of Methanosarcina sp., Pseudomonas sp., and rod-shaped bacteria.

Expression of HMGI(Y) associated with malignant phenotype of human gastric tissue

AIMS

We evaluated the association between HMGI(Y) expression and the detection of malignant cells by simple reverse transcriptase-polymerase chain reaction (RT-PCR) and correlated the level of HMGI(Y) expression and the clinicopathological data in gastric cancer.

METHODS AND RESULTS

We analysed HMGI(Y) expression in 62 gastric cancer tissues and 28 normal gastric tissues by RT-PCR and immunohistochemical study. HMGI(Y) expression evidenced by RT-PCR was observed in 42 (67.7%) of 62 gastric cancer samples, whereas eight (28.6%) of 28 normal gastric tissues were positive (P = 0.001). In immunohistochemical staining for HMGI(Y), 48 (77.4%) of 62 gastric cancers were positive for HMGI(Y), whereas four (6.5%) of 62 normal gastric mucosae around the tumour were weakly positive, particularly in cells of some hyperplastic glands (P < 0.001). There was no significant correlation between the levels of HMGI(Y) expression and stage, tumour size, histological grade, invasion depth, or lymph node metastasis.

CONCLUSIONS

Our results suggest that HMGI(Y) expression could be associated with malignant phenotype in human gastric tissue, and that HMGI(Y) may contribute to gastric tumorigenesis.

Nutrient removal using anaerobically fermented leachate of food waste in the BNR process

Nutrients removal efficiencies highly depend on the presence of biodegradable organic carbon in the biological nutrient removal (BNR) process but most domestic wastewater in Korea has shown a low C/N ratio and has a small amount of biodegradable COD (chemical oxygen demand). On the other hand, about 11,577 tons of food waste that contains a lot of organic material has been produced in Korea per day. The feasibility and applicability of anaerobically fermented leachate of food waste (AFLFW) as an external carbon source was examined in the laboratory-scale BNR process at different operation conditions with synthetic wastewater and domestic sewage. As the addition of AFLFW increased, the average removal efficiencies of SCOD, T-N, T-P changed from 96%, 60%, and 2% to 90%, 77%, and 67%, respectively. From anoxic nitrate utilization tests, it was observed that once the readily biodegradable COD (especially VFAs) was depleted, the denitrification rate reduced from 8.2 mg NO3-N/g VSS/hr to 0.7 mg NO3-N/g VSS/hr. From the molecular size distribution test, it was concluded that about 60% of soluble COD in effluent, which was considered to originate from AFLFW, had a large molecular size (> 30 kDa) that was not used by microorganisms.

Association of maspin expression with the high histological grade and lymphocyte-rich stroma in early-stage breast cancer

AIMS

Maspin is a recently described member of the serpin family or protease inhibitors that is known to be a tumour suppressor gene product. Loss of maspin expression has been found in most breast cancer cases and is correlated with cell motility and tumour invasiveness. However, its precise role in human breast cancer remains to be discovered. We aimed to evaluate the role of maspin in early-stage breast cancer.

METHODS AND RESULTS

We analysed the expression of maspin in 192 stage I and II primary breast cancers by immunohistochemistry. Of these cases, 34.4% showed maspin expression. Maspin expression was more frequently found in invasive ductal carcinoma (36.4%) than in invasive lobular carcinoma (7.1%). High maspin expression was demonstrated in breast cancers showing high histological grade or lymphocyte-rich stroma (P < 0.05). Maspin expression was not associated with overall and disease-free survival rate of breast cancer.

CONCLUSIONS

The results indicate that different biological mechanisms may be responsible for maspin expression in histologically distinct types of breast cancer. Our survey suggests that maspin expression in breast cancer might have a compensatory role rather than prognostic one.

Electrically enhanced ethanol fermentation by Clostridium thermocellum and Saccharomyces cerevisiae

Ethanol production by Clostridium thermocellum ATCC 35609 and Saccharomyces cerevisiae ATCC 26603 was improved in an electrochemical bioreactor system. It was increased by 61% with Cl. thermocellum and 12% with S. cerevisiae in the presence of -1.5 V of electric potential. These increases were attributed to high production rates due to regeneration and availability of increased reduced equivalents in the presence of electric potential. The electric current caused considerable shift in the metabolite concentrations on a molar basis in Cl. thermocellum fermentation but less in S. cerevisiae fermentation. Increasing electric potential in Cl. thermocellum fermentation resulted in less acetate and more lactate production. Acetate production was also reduced with increased electric potential in S. cerevisiae fermentation. The high electric potential of -5 V adversely affected the Cl. thermocellum fermentation, but not the S. cerevisiae fermentation even at a high electric potential of -10 V.

Novel anaerobic process for the recovery of methane and compost from food waste

Multi-step sequential batch two-phase anaerobic composting (MUSTAC) process was used to recover methane and composted material from food waste. The MUSTAC process consists of five leaching beds for hydrolysis, acidification and post-treatment, and an upflow anaerobic sludge blanket (UASB) reactor for methane recovery. This process involves the combined methods of sequential batch operation and two-phase anaerobic digestion for simple operation and high efficiency. Rumen microorganisms are inoculated due to their enhanced cellulolytic activity. Each leaching bed is operated in a sequential batch mode. Five leaching beds are operated in a multi-step mode with a two-day interval between degradation stages. Acidified products in the leachate from the leaching beds are converted to methane in the UASB reactor. The MUSTAC process demonstrated that it was capable of removing 84.9% of volatile solids (VS) and converting 85.6% of biochemical methane potential (BMP) into methane at 10.9 kg VS/m3 x d in 10 days. Methane gas production rate was 2.31 m3/m3 x d. The output from the post-treatment of residues in the same leaching bed without troublesome moving met the Korean regulation on compost, indicating that it could be used for soil amendment.

Denitrification of high NO3(-)-N containing wastewater using elemental sulfur; nitrogen loading rate and N2O production

The effects of both concentration and loading rates of nitrate on denitrification efficiency and N2O production during the autotrophic denitrification with elemental sulfur were evaluated. Experiments were conducted with three continuously fed sulfur packed bed reactors (SPBRs) with different influent nitrate concentrations. The loading rate at which nitrate removal efficiency was greater than 95% decreased from 2.46 to 1.64 kg NO3(-)-N m(-3) day(-1) as the influent NO3(-)-N concentration increased from 175 to 700 mg 1(-1). The nitrate removal rate per unit volume of sulfur layer can be expressed as alpha (ALR)n, where ALR is the applied loading rate. The range of alpha and n values were 0.72-0.83 and 0.91-0.94, respectively. The maximum nitrate removal rate was estimated as 3.9 to 4.5 kg NO3(-)-N m(-3) day(-1) depending on the influent NO3(-)-N concentration. The loading rate for complete denitrification without N2O production was 1.37 kg NO3(-)-N m(-3) day(-1) at the influent NO3(-)-N concentration of 175 mg 1(-1). N2O production became significant when the influent nitrate concentration increased while the loading rate remained the same. The batch test indicated that the amount of N2O production per unit mass of nitrogen was greater with nitrite than with nitrate showing that N2O production was directly related to the concentration of nitrite and nitrate.

Effects of transdermal nicotine on attention and memory in healthy elderly non-smokers

RATIONALE

Nicotine has been found to improve cognitive functions in patients with Alzheimer's disease, but little is known about its effects in the healthy non-smoking elderly.

OBJECTIVES

This study aimed to investigate the effects of nicotine on cognitive function in healthy non-smoking or nicotine-naïve elderly subjects.

METHODS

A transdermal patch containing either 5 mg nicotine or placebo was applied on the back of 63 healthy nicotine-naïve or non-smoking elderly Koreans. Cognitive functions were evaluated with the Short Blessed Test, Rey-Kim Memory Test, and digit span test of the Korean-WAIS, both before and 5.5 h after nicotine administration. The plasma level of nicotine after testing was measured using gas chromatography.

RESULTS

The subjects' memory functions in trial 5 of the Rey-Kim Memory Tests improved significantly. Furthermore, the effect on memory slope was significantly correlated with the higher plasma level of nicotine. However, the other tests did not reveal any correlation to a significant degree.

CONCLUSIONS

These results suggest that nicotine of lower plasma level can improve short-term verbal memory functions in non-smoking or nicotine-naïve healthy elderly people and that some effects are dependent on nicotine plasma levels.