Biomedical subjects

C P Chu

Publications and source records attributed to C P Chu.

At least 37 records · Page 2Linked to original sources

PubMed2001

Thermal pyrolysis characteristics of polymer flocculated waste activated sludge.

Polyelectrolyte conditioning is a common practice in wastewater management. This paper experimentally elucidated the thermal pyrolysis characteristics of waste activated sludge at a temperature range of 300-900 K (27-627 degrees C) using thermogravimetric analysis (TGA) in inert atmosphere, with especial attention on the effect of polyelectrolyte flocculation (using cationic polyacrylamide). On the pyrolysis rate vs temperature plot two maxima were noted. At the heating rate of 8 degrees C/min, polyelectrolyte does not influence the pyrolysis process. As higher heating rates (14 and 20 degrees C/min), on the other hand, flocculation to charge neutralization point would enhance the rate of thermal pyrolysis. A simple two parallel-reaction kinetic model is applied to interpret the experimental data. Possible roles of flocculant on sludge pyrolysis are discussed on the basis of change in sludge structures and the hindrance of surface reactions of sludge particles.

Electrolytes↗

PubMed2001

Observations on changes in ultrasonically treated waste-activated sludge.

This work experimentally elucidates the effects of ultrasonic treatment on the physical, chemical, and biological characteristics of a waste-activated sludge. A critical ultrasonic power level exists above which, accompanied with the release of divalent cations from the sludge body, the floc structure effectively disintegrated, microbial level acceptably disinfected, and particulate organic compounds sufficiently transformed into soluble state. Both ultrasonic vibration and bulk temperature rise contribute to the treatment efficiency. Possible mechanisms of ultrasonic treatment are discussed.

Biodegradation, Environmental↗

PubMed2001

Experimental analysis of centrifugal dewatering process of polyelectrolyte flocculated waste activated sludge.

The study experimentally investigated the centrifugal separation of moisture from activated sludge subject to cationic polyelectrolyte flocculation. An arm-suspended centrifuge was employed which allowed in-situ detection on all positions of interfaces of centrifuged sludge as functions of time. Experimental results revealed that, sludge flocculation would yield a significant sedimentation effect at the first phase of centrifugation. Therefore, not as suggested in conventional centrifugal-filtration models, the most significant moisture-removal stages included filtrate to flow through a wet cake. Moreover, an optimal rotational speed exists at which the moisture-removal rate reaches a maximum value. New theories/correlations are required to describe centrifugation dewatering of polyelectrolyte flocculated sludge.

Centrifugation↗

PubMed2001

High-speed sludge freezing.

The investigation examined the feasibility of applying a "high-speed freezing technique, using liquid nitrogen freezing, to condition activated sludges and alum sludges. Experimental results indicate that the freezing speed is much faster than that adopted in most previous works on sludge freezing. Although the filterability and settleability of the alum sludge is improved by 3-min liquid nitrogen freezing, no similar improvement is observed for activated sludge. Moreover, curing affects neither sludge after liquid nitrogen freezing, but affects the slow-freezing activated sludge.

Alum Compounds↗

PubMed2001

Effects of jiawey siwu on rat activity.

Jiawey siwu (JS) is a modified formula of siwu with the addition of Ginseng Radix and Eucommiae Cortex. We studied the CNS effect of JS on pentobarbital-induced hypnosis in ICR mice after acute oral administration. We also investigated the motor activity and exercise performance effects of JS in SD rats after subchronic (12 days) and chronic (8 weeks) oral administration with an activity cage and rotarod, respectively. The duration of pentobarbital-induced hypnosis was significantly decreased in mice after acute oral administration of 0.21, 1.05 or 4.2 g/kg JS. The time of ambulatory activity and time on the rotarod significantly increased in rats after subchronic and chronic oral administration of 1.05 g/kg JS, respectively. These results indicate that JS potentially increased the excitability of the CNS in mice, as well as increasing motor activity and physical endurance in rats.

Animals↗

PubMed2001

Tracheal intubation using suspension laryngoscopy in an infant with Goldenhar's syndrome.

We present a case of a ten-month-old boy with Goldenhar's syndrome and significant retrognathia in whom a tracheostomy was performed to relieve upper airway obstruction. Tracheal intubation was facilitated by direct suspension laryngoscopy using a slotted rigid laryngoscope. We propose this technique as an alternative method for tracheal intubation in infants and young children with a difficult airway. The management of the difficult airway in children with Goldenhar's syndrome is discussed.

Goldenhar Syndrome↗

PubMed1999

Lone atrial fibrillation in elderly persons: a marker for cardiovascular risk.

BACKGROUND: The risk of stroke in persons aged 60 years and younger with lone atrial fibrillation (LAF) is no greater than in the general population. The effect of older age on the risk of stroke in persons with LAF is less well established. PARTICIPANTS AND METHODS: The risk of stroke in persons with LAF and without substantial comorbidities was examined in a population-based study at a single institution in Olmsted County, Minnesota, and compared with that in an age- and sex-matched population. The mean age was 74 years (range, 61-97 years). The median duration of follow-up was 9.6 years until death or last follow-up. RESULTS: Of 55 patients, 26 had 31 cardiovascular events during follow-up, occurring a median of 5.1 years after diagnosis (range, 0.7-18 years). Of 11 cerebrovascular events, 6 were transient ischemic attacks and 5 were strokes. The event rates (percentage per person-year) were 0.9% for stroke, 1.1% for transient cerebral ischemia, and 2.6% for myocardial infarction, for a total cardiovascular event rate of 5.0% per person-year. The corresponding rates for the age- and sex-matched control group were 0.2%, 0%, and 1.1%, for a total of 1.3% per person-year. The incidence of total cardiovascular events was significantly greater (P< .01) in those with LAF, although there was no difference in survival. CONCLUSION: Lone atrial fibrillation occurring after age 60 years is a risk marker for a substantial increase in cardiovascular events that warrants consideration for antithrombotic therapy.

Aged↗

PubMed1998

Dolichoectasia of the intracranial arteries in patients with first ischemic stroke: a population-based study.

OBJECTIVE: The objective of this study was to estimate the frequency of intracranial arterial dolichoectasia among patients with first ischemic stroke and to compare clinical characteristics, survival, and recurrence in those with and without the abnormality. BACKGROUND: Dolichoectasia may cause cerebral infarction by thrombosis, embolism, stenosis, or occlusion of deep penetrating arteries. METHODS: The chi-square, Fisher's exact, and logrank tests were used to compare clinical characteristics, survival, and recurrence for patients with and without dolichoectasia among the 387 residents of Rochester, MN, who had brain CT or MRI for first cerebral infarction from 1985 through 1989. RESULTS: Twelve patients (3.1%) had dolichoectasia. Patients with dolichoectasia were more likely to have had stroke fitting a clinical and radiographic pattern of lacunar infarction than those without (42% and 17% respectively; p=0.04). Dolichoectasia was detected in the vertebrobasilar system in eight patients (66.7%), in the carotid system in two patients (16.7%), and in both circulatory systems in two patients (16.7%). There were no significant differences in the following characteristics among those with and without dolichoectasia: age, sex, hypertension, diabetes, smoking, and preceding transient ischemic attack. Patients with dolichoectasia had better survival (relative risk [RR] for death, 0.26; p=0.04) after first cerebral infarction but higher rates of stroke recurrence (RR, 2.4; p=0.02). CONCLUSIONS: Dolichoectasia is detected in 38 of patients with first cerebral infarction and is associated with better survival but higher rates of stroke recurrence.

Aged↗

PubMed1997

Patent foramen ovale in patients with cerebral infarction. A transesophageal echocardiographic study.

OBJECTIVES: To determine the frequency of patent foramen ovale (PFO) among various subtypes of cerebral infarction. To determine whether any historical or clinical characteristics predict the presence or absence of PFO in these patients. DESIGN: Comorbidity and infarct subtype study. SETTING: Referral-based study. PATIENTS: One hundred sixteen patients with cerebral infarction consecutively referred for transesophageal echocardiography during a 6-month period. MAIN OUTCOME MEASURES: Infarct subtype classification was made using a clinical and radiographic diagnostic rubric similar to that used by the Stroke Data Bank of the National Institute of Neurological Diseases and Stroke. The frequency of various risk factors and clinical characteristics in patients with and in those without PFO and the frequency of PFO in patients with various infarct subtypes were compared (chi 2 or Fisher exact tests). RESULTS: Patent foramen ovale was detected in 37 patients (32%). Mean age was similar in those with (60 years) and those without (64 years) PFO. Patent foramen ovale was more frequent among men (39%) than women (20%, P = .03). Patients with PFO had a lower frequency of atrial fibrillation, diabetes mellitus, hypertension, and peripheral vascular disease compared with those without PFO. There was no difference in frequency of the following characteristics in patients with PFO compared with those without PFO: pulmonary embolus, chronic obstructive pulmonary disease, pulmonary hypertension, peripheral embolism, prior cerebral infarction, nosocomial cerebral infarction, Valsalva maneuver at the same time of cerebral infarction, recent surgery, or hemorrhagic transformation of cerebral infarction. Patent foramen ovale was found in 22 (40%) of 55 patients with infarcts of uncertain cause and in 15 (25%) of 61 with infarcts of known cause (cardioembolic, 21%; large vessel atherostenosis, 25%; lacune, 40%) (P = .08). When the analysis was restricted to patients who underwent Valsalva maneuver, PFO with right to left or bidirectional shunt was found in 19 (50%) of 38 patients with infarcts of uncertain cause and in 6 (20%) of 30 with infarcts of known cause (P = .01). CONCLUSION: Although PFO was overrepresented in patients with infarcts of uncertain in our and other studies, it has a high frequency among patients with cerebral infarction of all types. The relation between PFO and stroke requires further study.

Aged↗

PubMed1996

Dementia after ischemic stroke: a population-based study in Rochester, Minnesota (1960-1984)

We used the medical records linkage system for the population of Rochester, Minnesota, to identify persons in the community who had their first cerebral infarct without previous dementia. In this cohort (n = 971), the incidence of dementia in the first year was nine times greater than expected, but if we did not observe dementia in the first year, the risk of dementia in the cohort each year thereafter was about twice the risk in the population. After the first year, a 50% increase was observed in Alzheimer's disease in the cohort compared with that in the community. Although the incidence of dementia increased with increasing age, the standardized morbidity ratios decreased with increasing age. Age, sex (male), and second stroke were significant independent predictors of dementia in a multivariate Cox proportional hazards model. There was no effect of location or clinical severity of infarct on the rate of occurrence of dementia.

Aged↗

PubMed1995

The poor prognosis of ruptured intracranial aneurysms of the posterior circulation.

The first 48 hours after aneurysmal subarachnoid hemorrhage are critical in determining final outcome. However, most patients who die during this initial period are not included in hospital-based studies. We investigated the occurrence of subarachnoid hemorrhage in a population-based study to evaluate possible predictors of poor outcome. All patients diagnosed with aneurysmal subarachnoid hemorrhage between 1955 and 1984 were selected for analysis of mortality in the first 30 days using the medical record-linkage system employed for epidemiological studies in Rochester, Minnesota. One hundred and thirty-six patients were identified. The mean age of these 99 women and 37 men was 55 years. Rates for survival to 48 hours were 32% for the 19 patients with posterior circulation aneurysms, 77% for the 87 patients with anterior circulation aneurysms, and 70% for the 30 patients with a presumed aneurysm (p < 0.0001). Rates for survival to 30 days were 11%, 57%, and 53%, respectively, in these three patient groups (p < 0.0001). Clinical grade on admission to the hospital, the main variable predictive of death within 48 hours, was significantly worse in patients with posterior circulation aneurysms than in others (p < 0.0001). The prognosis of ruptured posterior circulation aneurysms is poor. The high early mortality explains why posterior circulation aneurysms are uncommon in most clinical series of patients with subarachnoid hemorrhage. The management of incidentally discovered intact posterior circulation aneurysms may be influenced by these findings.

Adolescent↗

PubMed1994

The contribution of non-insulin-dependent diabetes to lower-extremity amputation in the community.

BACKGROUND: Despite the significant public health burden of lower-extremity amputations in diabetes mellitus, few data are available on the epidemiology of lower-extremity amputations in diabetes mellitus in the community setting. METHODS: A retrospective incidence cohort study based in Rochester, Minn, was conducted. RESULTS: Among the 2015 diabetic individuals free of lower-extremity amputation at the diagnosis of diabetes mellitus, 57 individuals underwent 79 lower-extremity amputations (incidence, 375 per 100,000 person-years; 95% confidence interval, 297 to 467). Among the 1826 patients with non-insulin-dependent diabetes mellitus, 52 underwent 73 lower-extremity amputations, and the subsequent incidence of lower-extremity amputation among these residents was 388 per 100,000 person-years (95% confidence interval, 304 to 487). Of the 137 insulin-dependent diabetic patients, four subsequently underwent five lower-extremity amputations (incidence, 283 per 100,000 person-years; 95% confidence interval, 92 to 659). Twenty-five years after the diagnosis of diabetes mellitus, the cumulative risk of one lower-extremity amputation was 11.2% in insulin-dependent diabetes mellitus and 11.0% in non-insulin-dependent diabetes mellitus. When compared with lower-extremity amputation rates for Rochester residents without diabetes, patients with non-insulin-dependent diabetes mellitus were nearly 400 times more likely to undergo an initial transphalangeal amputation (rate ratio, 378.8) and had almost a 12-fold increased risk of a below-knee amputation (rate ratio, 11.8). In this community, more than 60% of lower-extremity amputations were attributable to non-insulin-dependent diabetes mellitus. CONCLUSIONS: These population-based data document the magnitude of the elevated risk of lower-extremity amputation among diabetic individuals. Efforts should be made to identify more precisely risk factors for amputation in diabetes and to intervene in the processes leading to amputation.

Amputation, Surgical↗

PubMed1992

Modular design of the Enterococcus hirae muramidase-2 and Streptococcus faecalis autolysin.

The mature forms of the extracellular muramidase-2 of Enterococcus hirae and Streptococcus faecalis autolysin have very similar primary structures. Each consists of an active-site-containing N-terminal domain fused to a multiple-repeat C-terminal domain. Polypeptide segments occurring at equivalent places in these two bacterial wall lytic enzymes have homologues in two phage lysozymes and in three functionally unrelated proteins, illustrating the principle that protein molecules frequently are constructed from modules that are linked in a single polypeptide chain.

Amino Acid Sequence↗

PubMed1992

Cloning and sequence analysis of the muramidase-2 gene from Enterococcus hirae.

Extracellular muramidase-2 of Enterococcus hirae ATCC 9790 was purified to homogeneity by substrate binding, guanidine-HCl extraction, and reversed-phase chromatography. A monoclonal antibody, 2F8, which specifically recognizes muramidase-2, was used to screen a genomic library of E. hirae ATCC 9790 DNA in bacteriophage lambda gt11. A positive phage clone containing a 4.5-kb DNA insert was isolated and analyzed. The EcoRI-digested 4.5-kb fragment was cut into 2.3-, 1.0-, and 1.5-kb pieces by using restriction enzymes KpnI, Sau3AI, and PstI, and each fragment was subcloned into plasmid pJDC9 or pUC19. The nucleotide sequence of each subclone was determined. The sequence data indicated an open reading frame encoding a polypeptide of 666 amino acid residues, with a calculated molecular mass of 70,678 Da. The first 24 N-terminal amino acids of purified extracellular muramidase-2 were in very good agreement with the deduced amino acid sequence after a 49-amino-acid putative signal sequence. Analysis of the deduced amino acid sequence showed the presence at the C-terminal region of the protein of six highly homologous repeat units separated by nonhomologous intervening sequences that are highly enriched in serine and threonine. The overall sequence showed a high degree of homology with a recently cloned Streptococcus faecalis autolysin.

Amino Acid Sequence↗

PubMed1991

Reduction mammaplasty: cosmetic or reconstructive procedure?

Ninety-two of 220 plastic surgeons submitted information from 600 women (the last 15 to 20 reduction mammaplasties by each surgeon) regarding height, weight, and amount of breast tissue removed. In a second survey to estimate percentages of women who sought reduction mammaplasties for purely cosmetic reasons, for mixed reasons, and for purely medical reasons, 132 of the same 220 surgeons responded. All women whose removed breast weight was less than the 5th percentile sought the procedure for purely cosmetic reasons, and all women whose breast weight was greater than the 22nd percentile sought the procedure for medical reasons. Those women whose removed breast tissue weight was between the 5th and the 22nd percentiles had mixed reasons for requesting the procedure.

Body Surface Area↗

PubMed1990

Regulation of pyrimidine biosynthesis in Pseudomonas cepacia.

Pyrimidine biosynthesis was investigated in Pseudomonas cepacia ATCC 17759. The presence of the de novo pyrimidine biosynthetic pathway enzyme activities was confirmed in this strain. Following transposon mutagenesis of the wild-type cells, a mutant strain deficient for orotidine 5'-monophosphate decarboxylase activity (pyrF) was isolated. Uracil, cytosine or uridine supported the growth of this mutant. Uracil addition to minimal medium cultures of the wild-type strain diminished the levels of the de novo pyrimidine biosynthetic enzyme activities, while pyrimidine limitation of the mutant cells increased those de novo enzyme activities measured. It was concluded that regulation of pyrimidine biosynthesis at the level of enzyme synthesis in P. cepacia was present. Aspartate transcarbamoylase activity was found to be regulated in the wild-type cells. Its activity was shown to be controlled in vitro by inorganic pyrophosphate, adenosine 5'-triphosphate and uridine 5'-phosphate.

Aspartate Carbamoyltransferase↗

PubMed1990

Pyrimidine ribonucleoside catabolism in Pseudomonas fluorescens biotype A.

The pyrimidine ribonucleosides uridine or cytidine were shown to serve as a source of nitrogen or carbon for the growth of Pseudomonas fluorescens strain A126. After incubation of either pyrimidine ribonucleoside with extracts of this strain, the resultant catabolic products were detected by thin-layer chromatography. It was found that pyrimidine ribonucleoside catabolism in this pseudomonad involved the enzymes nucleoside hydrolase and cytosine deaminase. The specific activities of both these enzymes could be influenced by the nitrogen or carbon source present in the medium.

Carbon↗

PubMed1990

Pyrimidine biosynthetic pathway of Pseudomonas fluorescens.

Pyrimidine biosynthesis in Pseudomonas fluorescens strain A126 was investigated. In this study, de novo pyrimidine biosynthetic pathway mutant strains were isolated using both conventional mutagenesis and transposon mutagenesis. The resulting mutant strains were deficient for either aspartate transcarbamoylase, dihydroorotase or orotate phosphoribosyltransferase activity. Uracil, uridine or cytosine could support the growth of every mutant strain selected. In addition, the aspartate transcarbamoylase mutant strains could utilize orotic acid to sustain their growth while the orotidine-5'-monophosphate decarboxylase mutant strains grew slowly upon uridine 5'-monophosphate. The wild-type strain and the mutant strains were used to study possible regulation of de novo pyrimidine biosynthesis in P. fluorescens. Dihydroorotase specific activity more than doubled after the wild-type cells were grown in orotic acid relative to unsupplemented minimal-medium-grown cells. Starving the mutant strains of pyrimidines also influenced the levels of several de novo pyrimidine biosynthetic pathway enzyme activities.

Aspartate Carbamoyltransferase↗