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Biomedical subjects

J Y Lai

Publications and source records attributed to J Y Lai.

At least 19 recordsLinked to original sources

Oxygen diffusion in active layer of aerobic granule with step change in surrounding oxygen levels.

High biomass density and large size limit the transfer of dissolved oxygen (DO) in aerobic granules. In the literature, the oxygen diffusivity is often employed as an input parameter for modeling transport processes in aerobic granules. The interior of an aerobic granule was observed to be highly heterogeneous. In this work, the distributions of extracellular polymeric substances (EPS) and cells in the interior of phenol-fed and acetate-fed granules were built up using a five-fold staining scheme, combined with the use of a confocal laser scanning microscope (CLSM). The steady-state and transient DO with step changes in surrounding DO levels at various depths were measured in the granules using microelectrodes. Cells were probed in a surface layer of thickness 125-375 microm. A marked fall in DO was also noted over this surface layer. No aerobic oxidation could occur beneath the active layer, indicating the oxygen transfer limit. Fitting the steady-state and transient DO data over the active surface layer yielded apparent diffusivities of oxygen were (9.5+/-3.5)x10(-10)m(2)s(-1) for the phenol-fed granule and (3.5+/-1.0)x10(-10)m(2)s(-1) for the phenol-fed granule. These values were lower than those adopted in models in the literature.

Acetates↗

Nanoparticles in wastewater from a science-based industrial park - coagulation using polyaluminum chloride.

The Hsinchu Science-based Industrial Park (HSIP) is the hi-tech manufacturing hub of Taiwan. Wastewater from the HSIP contains numerous nano-sized silicate particles whose size distributions peak at 2 and 90 nm. A 3-5 mg l(-1) as Al dose of polyaluminum chloride (PACl) was used in the field to coagulate these particles, but the removal efficiency was low. Laboratory scale tests indicated that although PACl coagulation removed 52% of the turbidity and 48% of the chemical oxygen demand (COD) from water, its effect on nano-particle removal was minimal. About 58% of the soluble COD was associated with colloidal Si particles. A light scattering test and transmission electron microscopy (TEM) demonstrated that the nano-particles agglomerated in approximately linear aggregates of sizes 100-300 nm. Prolonged contact between residual PACl and the nano-particles generated large aggregates with sizes of up to 10 microm and a fractal dimension of 2.24-2.63. The results presented herein should be of interest in the processing of "high-tech" wastewater that contains nanosized silica particles.

Aluminum Hydroxide↗

Membrane biofouling by extracellular polymeric substances or soluble microbial products from membrane bioreactor sludge.

This study extracted the soluble microbial products and loosely bound and tightly bound extracellular polymeric substances (EPS) from suspended sludge from a membrane bioreactor, original and aerobically/anaerobically digested, and compared their fouling potentials on a microfiltration membrane. The resistance of cake layer accounts for 95-98% of the total filtration resistances when filtering the whole sludges, with anaerobically digested sludge presenting the highest resistance among the three tested sludges. The tightly bound EPS has the highest potential to foul the membrane; however, the loosely bound EPS contribute most of the filtration resistances of the whole sludges. The foulants corresponding to the irreversible fouling have chemical fingerprints similar to those from loosely bound EPS, which have a greater predilection to proteins and humic substances than to polysaccharides.

Aerobiosis↗

Fluorecent staining for study of extracellular polymeric substances in membrane biofouling layers.

Membrane biofouling by microbial products adversely impacts the feasibility of adopting membrane bioreactors (MBRs) for treating wastewater. The fouling layer structure determines the pressure drop across the fouling layer. Three-dimensional distributions of nucleic acids, proteins, alpha-D-GLUCOPYRANOSE POLYSACCHARIDES, AND B-D-glucopyranose polysaccharides in the fouling layer formed on a mixed cellulose ester membrane were generated utilizing a quadruple staining protocol combined with confocal laser scanning microscopy (CLSM). For the first time, this study constructed a three-dimensional volumetric grids model representing the fouling layer structure on the basis of a series of CLSM images. Quantitative structural information about the fouling layer was extracted from the CLSM images.

Bacteria↗

Non-traumatic colon perforation in children: a 10-year review.

Colon perforation is an abdominal surgical emergency in the pediatric population, but is seldom reported when occurring from non-traumatic causes in children beyond the neonate. The goal of this study was to identify the clinical characteristics, management, and outcomes of non-traumatic colon perforation in children. Medical records for the 10-year period from September 1994 to September 2004 were reviewed for children beyond the neonate with non-traumatic colon perforation. Data gathered included age, gender, symptoms, duration of symptoms, physical findings, and length of postoperative hospital stay. Diagnostic information included laboratory data, radiographic imaging, and operative findings. Forty-four patients with non-traumatic colon perforation were recruited into this study. The mean age was 2.22 +/- 1.87 years; 91.4% of cases were younger than 5 years old. The most common presenting symptom was fever (97.7%); the most common sign was abdominal distention (93.1%). The mean duration of symptoms prior to admission was 6.19 days. Pneumoperitoneum was presented in 86.3% of patients by plain abdominal radiograph. Ascending and transverse colon were the most common perforation sites. Non-typhoid salmonella was the leading pathogen isolated, causing 20.4% of episodes. One case died due to Clostridium speticum infection. Non-traumatic colon perforation most commonly affects children younger than 5 years of age. It may be secondary to infection, especially non-typhoid salmonella. Plain abdominal radiograph can be an adjuvant tool for the high index of suspicion for colon perforation in children with abdominal distention and history of fever or diarrhea for more than 5 days.

Abdomen, Acute↗

Co-conditioning and dewatering of alum sludge and waste activated sludge.

Co-conditioning and dewatering behaviors of alum sludge and waste activated sludge were investigated. Two different sludges were mixed at various ratios (2:1; 1:1; 1:2; 1:4) for study. Capillary suction time (CST) and specific resistance to filtration (SRF) were utilized to assess sludge dewaterability. Relatively speaking, waste activated sludge, though of higher solid content, was more difficult to be dewatered than alum sludge. It was found that sludge dewaterability and settlability became better with increasing fraction of alum sludge in the mixed sludge. Dosage required of the cationic polyelectrolyte (KP-201C) for dewatering was reduced as well. It is proposed that alum sludge acts as skeleton builder in the mixed sludge, and renders the mixed sludge more incompressible which is beneficial for sludge dewatering. Implications of the results of the study to the sludge management plan for Taipei City that generates both alum sludge and waste activated sludge at significant amount are also discussed. The current sludge treatment and disposal plan in Metropolitan Taipei could be made more cost-effective.

Alum Compounds↗

A CFD study of the deep bed filtration mechanism for submicron/nano-particle suspension.

The mechanism of the deep bed filtration for submicron and nano particles suspension was conducted by means of a force analysis on the suspended particles flow path through order-packed granular filter beds. The flow fields through the filter beds were calculated by using the commercial available CFD software--Fluent. Various types of granular packing structures, such as the simple cubic packing, body-centered packing and face-centered packing structures were chosen for analysis. The motion of suspended particle of 2.967, 0.816, 0.460 and 0.050 microm in diameter, respectively, were tracked by considering the following forces including a net gravitational force, hydraulic drag force, lift force, Brownian force, van der Waals force and a double layer force. The effects of the granular bed packing structure, the porosity of these beds and the suspended particle diameter on the capture efficiency of a granular filter bed were examined. The force analysis depicts that the inertial effect and van der Waals force increased the capture probability of particles on the granular filter bed while the lift force and the Brownian force decreased the particle deposition. Simulated results show that among the chosen packing structures, the face-center packed granular bed gives the greatest pressure drop and capture efficiency of particles due to the lower packing porosity. The simple cubic packed filter bed showed the lowest pressure drop and capture efficiency of particles due to the greatest packing porosity among the chosen packing structures. It is mainly due to the simple cubic packing structure in which there exists the free vertical downward flowing path and thus exhibits a higher packing porosity. The comparisons of the simulated capture efficiency with experimental results depicted that the body-centre packed granular bed showed the best approximation of capture efficiency compared to that of the randomly packed granular bed.

Computer Simulation↗

Transport properties of ionic drugs in the ammonio methacrylate copolymer membranes.

PURPOSE: Ammonio methacrylate copolymer is a pharmaceutical excipient widely used as a coating material for encapsulation of pellet and tablet dosage forms. Because of the charged ammonio function groups within the polymer, ionic drugs may interact with the coating film while transporting through it. The kinetic swelling and drug permeation properties of the ammonio methacrylate copolymer membranes were studied to delineate the effect of ionic interaction between the ionic drugs and the membranes. METHODS: The pH and ionic strength of the solutions and the charged properties of drugs were varied to study the effects on the transport properties through the membranes. Ambroxol was chosen as a model cationic drug and aspirin as a model anionic drug. RESULTS: The degree of membrane swelling in the drug-free solution decreases as the ionic strength increases but it is irrelevant to the pH. With the presence of ionic drugs, the degree of membrane swelling is affected by the drug species as well as the pH of the solutions in addition to the effect of ionic strength. The degree of swelling for a membrane in a solution containing aspirin is higher at a lower pH and ambroxol is lower at a lower pH. Aspirin experiences a three-stage permeation and ambroxol a two-stage one. The ion-exchange reaction between the anionic carboxylic groups in aspirin and the cationic ammonio groups in the membranes results in a slow permeation stage during the transient state. The pseudo steady-state permeability for each drug follows the trend as the degree of membrane swelling in the drug media at various pH and ionic strengths. However, it is much higher for aspirin than ambroxol although the degree of membrane swelling is higher in an ambroxol solution than that in an aspirin solution. The permeability of ambroxol through the membrane is largely reduced because of the Donnan exclusion effect. CONCLUSIONS: The interaction between ionic drugs with the cationic groups in the membranes affects the ionic strength of the solutions and results in a pH-dependent degree of swelling. The ionic interaction also determines the drug permeation rates as well as the transient permeation behaviors.

Algorithms↗

Biliary tract disease and acute non-A-E hepatitis in Hong Kong: prospective study.

OBJECTIVE: To investigate the role of biliary tract disease in patients with acute non-A-E hepatitis. DESIGN: Prospective study. SETTING: Infectious diseases unit, government hospital, Hong Kong. PATIENTS: Sixty-one consecutive patients, admitted with the diagnosis of acute hepatitis and negative hepatitis serology for hepatitis A, B, C, D, and E virus. MAIN OUTCOME MEASURES: Abdominal ultrasound and endoscopic retrograde cholangiopancreatography findings; clinical outcome. RESULTS: Ultrasonographic abnormalities indicating biliary tract disease were found in 30% (18/61) of patients. Endoscopic retrograde cholangiopancreatography performed in 78% (14/18) of patients with abnormal ultrasound finding(s) confirmed the presence of biliary tract disease. Age, sex, serum alanine aminotransferase level, and serum albumin level were independent predictors of biliary tract disease in the patients studied. CONCLUSION: Biliary tract diseases were found in 20% of patients with acute non-A-E hepatitis. Serum amylase and abdominal ultrasonography should be performed for all patients presenting with acute non-A-E hepatitis. Endoscopic retrograde cholangiopancreatography is indicated for those with apparent gallstones or abnormal biliary tract findings.

Acute Disease↗

Extracellular polymers of ozonized waste activated sludge.

Effect of ozonation on characteristics of waste activated sludge was investigated in the current study. Concentrations of cell-bound extracellular polymers (washed ECPs) did not change much upon ozonation, whereas the sum of cell-bound and soluble extracellular polymers (unwashed ECPs) increased with increasing ozone dose. Washed ECPs in original sludge as divided by molecular weight distribution was 39% < 1,000 Da (low MW), 30% from 1,000 to 10,000 Da (medium MW), and 31% > 10,000 Da (high MW). It was observed that the low-MW fraction decreased, and the high-MW fraction increased in ozonized sludge. The unwashed ECPs were characterized as 44% in low MW, 30% in medium MW, and 26% in high MW. Both low-MW and medium-MW fractions of unwashed ECPs decreased while high-MW fraction increased in ozonized sludge. The dewaterability of ozonized sludge, assessed by capillary suction time (CST) and specific resistance to filtration (SRF), deteriorated with ozone dose. The optimal dose of cationic polyelectrolyte increased with increasing ozone dose. The production rate and the accumulated amount of methane gas of ozonized sludge were also higher.

Electrolytes↗

Sequence and molecular analysis of the rpoA cluster genes from Xanthomonas campestris pv. campestris.

The Xanthomonas campestris rpsM (S13)-rpsK (S11)-rpsD (S4)-rpoA (alpha)-rplQ (L17) cluster, encoding RNA polymerase alpha-subunit and four ribosomal proteins, reside in a 3164-bp DNA region. The N-terminal sequence of the authentic alpha-protein determined chemically matches that predicted from the nucleotide sequence. rplQ is monocistronic, instead of being co-transcribed with the other genes as in Escherichia coli. Antiserum against the His-tagged alpha-protein cross-reacted with the E. coli alpha-protein.

Amino Acid Sequence↗

Plesiomonas shigelloides infection in Hong Kong: retrospective study of 167 laboratory-confirmed cases.

OBJECTIVE: To study the epidemiological, clinical, and microbiological features of Plesiomonas shigelloides infection in Hong Kong. DESIGN: Retrospective study. SETTING: Infectious Disease Unit of a district hospital, Hong Kong. PATIENTS: Patients with laboratory-confirmed cases of Plesiomonas shigelloides infection between 1 January 1995 and 31 December 1998. MAIN OUTCOME MEASURES: Epidemiological and clinical data, antibiotic sensitivity, and clinical outcome. RESULTS: There was an increasing trend in the number of isolates of Plesiomonas shigelloides obtained and the prevalence of the bacterium. A total of 197 isolates were obtained from 188 patients, and most isolates (172; 87.3%) were obtained during the summer. Clinical and epidemiological data were available for 167 patients (85 males, 82 females). Patient age ranged from 1 month to 95 years; the mean and median ages of the patients older than 15 years were 51.0 and 40.5 years, respectively (n=132). Only 35 (21.0%) of the 167 patients had a history of travel outside Hong Kong, whereas 21 (12.6%) had a history of consuming seafood or uncooked food; 39 (23.4%) had underlying medical conditions. Most patients (165; 98.8%) had symptoms of Plesiomonas shigelloides infection. Nine (5.4%) patients had had chronic diarrhoea for more than 2 weeks; watery and bloody diarrhoea was discharged by 122 (73.1%) and 42 (25.1%) of the patients, respectively. All 197 Plesiomonas shigelloides isolates were sensitive to ofloxacin, or levofloxacin and ceftriaxone. Resistance or partial resistance was recorded for ampicillin (72%), tetracycline (67%), co-trimoxazole (12%), and chloramphenicol (5%). The majority of patients (142/167; 85.0%) had self-limiting cases of infection, but 25 patients were given antibiotics for more severe symptoms at the time of presentation; there were two deaths. CONCLUSIONS: The occurrence of Plesiomonas shigelloides infection in Hong Kong is increasing, although most cases of are self-limiting.

Adolescent↗

Helicobacter treatment with quadruple therapy in primary health care for patients with a history of ulcer disease.

BACKGROUND: Few patients with a history of peptic ulcer are treated by their GP for H. pylori infection, even though theoretical evidence supports such an approach. OBJECTIVES: We aimed to determine the validity of this recommendation and to test the feasibility of quadruple therapy in primary health care. METHODS: In this prospective, non-randomized intervention study, 51 unselected patients with a history of proven ulcer disease received a 7-day quadruple therapy (lansoprazole, colloidal bismuth subcitrate, tetracycline and metronidazole) from their GP. Main outcome measures were: (i) endoscopically confirmed cure of the infection; (ii) results of serology at entry and at 6 months follow-up; (iii) quality of life at entry, at 6 weeks and at 6 months follow-up; (iv) gastric symptoms at entry, at 6 weeks and at 6 months follow-up; and (v) medication at entry and at 6 months follow-up. RESULTS: Quadruple therapy was well tolerated and there were no drop-outs with this regimen. Intention to treat cure rate was 48/51 (94%, 95% CI 87-100%), per protocol cure rate was 48/49 (98%, 95% CI 94-100%). 45/50 (90%) had positive serology at entry. IgG antibody titres decreased > 40% in 95.2% of patients. Quality of life improved significantly after treatment, gastric symptoms decreased and medication use decreased. CONCLUSIONS: GPs should be encouraged to identify patients with a history of ulcer disease and chronic use of acid suppressants and offer them treatment for H. pylori infection. This approach will cure the infection in almost all patients, it will improve the quality of life and decrease costs. Quadruple therapy does not lose efficacy when employed in primary care. Pre-treatment serological testing is potentially useful for narrowing down the treatment group to those with actual infection, and serology is promising as an easy and cheap follow-up instrument in primary health care.

2-Pyridinylmethylsulfinylbenzimidazoles↗

Neonatal necrotizing fasciitis: a report of three cases and review of the literature.

OBJECTIVE: Necrotizing fasciitis (NF) is a predominantly adult disorder, with bacterial infection of the soft tissue. In children, it is relatively rare and has a fulminant course with a high mortality rate. In the neonate, most cases of NF are attributable to secondary infection of omphalitis, balanitis, mammitis, postoperative complications, and fetal monitoring. The objective of this communication is to report 3 cases of neonatal NF and provide a literature review of this disorder. RESULTS: This review yielded 66 cases of neonatal NF. Only 3 cases were premature. There was no sex predilection and the condition rarely recurred. Several underlying conditions were identified that might have contributed to the development of neonatal NF. These included omphalitis in 47, mammitis in 5, balanitis in 4, fetal scalp monitoring in 2, necrotizing enterocolitis, immunodeficiency, bullous impetigo, and maternal mastitis in 1 patient each. The most common site of the initial involvement was the abdominal wall (n = 53), followed by the thorax (n = 7), back (n = 2), scalp (n = 2), and extremity (n = 2). The initial skin presentation ranged from minimal rash to erythema, edema, induration or cellulitis. The lesions subsequently spread rapidly. The overlying skin might later develop a violaceous discoloration, peau d'orange appearance, bullae, or necrosis. Crepitus was uncommon. Fever and tachycardia were frequent but not uniformly present. The leukocyte count of the peripheral blood was usually elevated with a shift to the left. Thrombocytopenia was noted in half of the cases. Hypocalcemia was rarely reported. Of the 53 wound cultures available for bacteriologic evaluation, 39 were polymicrobial, 13 were monomicrobial, and 1 was sterile. Blood culture was positive in only 20 cases (50%). Treatment modalities included the use of antibiotics, supportive care, surgical debridement, and drainage of the affected fascial planes. Two of the 6 cases who received hyperbaric oxygen therapy died. The overall mortality rate was 59% (39/66). In 12 cases, skin grafting was required because of poor granulation formation or large postoperative skin defects among the survivors. CONCLUSION: Neonatal NF is an uncommon but often fatal bacterial infection of the skin, subcutaneous fat, superficial fascia, and deep fascia. It is characterized by marked tissue edema, rapid spread of inflammation, and signs of systemic toxicity. The wound cultures are predominantly polymicrobial and the location of initial involvement depends on the underlying etiologic factor. High index of suspicion, prompt aggressive surgery, appropriate antibiotics, and supportive care are the mainstays of management in the newborn infant with NF.

Anti-Bacterial Agents↗

Application of asymmetric TPX membranes to transdermal delivery of nitroglycerin.

In this study, asymmetric poly(4-methyl-1-pentene) (TPX) membranes, fabricated by the dry/wet inversion method, were applied to transdermal delivery of nitroglycerin (NTG), a drug for treating angina pectoris. The flux of NTG through the TPX membrane was measured in vitro by a Franz cell. The results indicate that the NTG flux through asymmetric TPX membranes is strongly dependent on the membrane structure, which can be varied by adding nonsolvents in the casting solution. By adding different kinds of nonsolvents and adjusting the added amounts, membranes with different NTG release rates can be fabricated. It was also found that, with suitable drug formula, the NTG dissolution rate of a prototype TPX patch is comparable to that of a commercial patch, Transderm-Nitro. In addition, the data of NTG flux through a composite of TPX membrane and pig skin are also presented.

Animals↗