Prospective analysis of KRAS wild-type patients with metastatic colorectal cancer using cetuximab plus FOLFIRI or FOLFOX4 treatment regimens

Cetuximab, a monoclonal antibody targeting epidermal growth factor receptor, has proven to be efficient in the treatment of metastatic colorectal cancer. We made a prospective study of the efficacy and toxicities of cetuximab-combination first-line (FOLFOX4) versus second/third-line (FOLFIRI) chemotherapy in 98 KRAS wild-type patients who had metastatic colorectal cancer. Wild-type KRAS had been identified by direct sequencing. Associations between clinical response/progression-free survival/overall survival/toxicities and cetuximab-combination chemotherapy timing were evaluated. The overall response rate was significantly higher for first-line treatment than for second/third-line treatment (relative risk = 1.707, 95% confidence interval = 1.121-2.598). Both progression-free survival and overall survival indicated significantly longer survival of first-line treatment than second/third-line treatment patients. This study is a validation of a molecular analysis of KRAS wild-type status for the prediction of response to cetuximab-combination chemotherapy for metastatic colorectal cancer patients; its predictive role was less prominent in the second/third-line than in the first-line treatment patients.

GaN epitaxial layers prepared on nano-patterned Si(001) substrate

We report the growth of GaN epitaxial layer on Si(001) substrate with nano-patterns prepared by dry etching facility used in integrated circuit (IC) industry. It was found that the GaN epitaxial layer prepared on nano-patterned Si(001) substrate exhibits both cubic and hexagonal phases. It was also found that threading dislocation observed from GaN prepared on nano-patterned Si(001) substrate was significantly smaller than that prepared on conventional unpatterned Si(111) substrate. Furthermore, it was found that we can reduce the tensile stress in GaN epitaxial layer by about 78% using the nano-patterned Si(001) substrate.

Electronic Health Record Goes Personal World-wide

Objective Increasing patient demand for convenient access to their own healthcare data has led to more personal use of the Electronic Health Record (EHR). With “consumer empowerment” being an important issue of EHR, we are seeing a more “patient-centric” approach of EHR from countries around the world. Researchers have reported on issues in EHR sharing including concerns on privacy and security, consumer empowerment, competition among providers, and content standards. This study attempts to analyze prior research and to synthesize comprehensive, empirically-based conceptual models of EHR for personal use.

Methods We use “B2C(2B)” to represent this new behavior of EHR sharing and exchange, with “consumer” in the center stage.

ResultsBased on different information sharing mechanisms, we summarized the “B2C(2B)” behavior into three models, namely, the Inexpensive data media model, the Internet patient portal model and the Personal portable device model. Models each have their own strengths and weaknesses in their ways to share patient data and to address privacy and security concerns.

Conclusion Personal use of EHR under the B2C(2B) model does look promising based on our study. We started to observe a trend that governments around the world are embarking on related projects. With multiple stake-holders involved, we are only beginning to understand the complexity of such undertakings.

Enhanced enzymatic hydrolysis of sugarcane bagasse by N-methylmorpholine-N-oxide pretreatment

The cellulose dissolution solvent used in Lyocell process for cellulose fiber preparation, N-methylmorpholine-N-oxide (NMMO) monohydrate, was demonstrated to be an effective agent for sugarcane bagasse pretreatment. Bagasse of 20wt% was readily dissolved in NMMO monohydrate at 130 degrees C within 1h. After dissolution, bagasse could be regenerated by rapid precipitation with water as a porous and amorphous mixture of its original components. The regenerated bagasse exhibited a significant enhancement on enzymatic hydrolysis kinetic. Not only the reducing sugars releasing rate but also hydrolysis yield was enhanced at least twofold as compared with that of untreated bagasse. The cellulose fraction of regenerated bagasse was nearly hydrolyzed to glucose after 72h hydrolysis with Cellulase AP3. The recycled NMMO demonstrated the same performance as the fresh one on bagasse pretreatment for hydrolysis enhancement. The regenerated bagasse was directly used in simultaneous saccharification and fermentation (SSF) for ethanol production by Zymomonas mobilis. No negative effect on ethanol fermentation was observed and ethanol yield approximately 0.15 g ethanol/g baggasse was achieved.

Electronic health record goes personal world-wide

OBJECTIVE

Increasing patient demand for convenient access to their own healthcare data has led to more personal use of the Electronic Health Record (EHR). With "consumer empowerment" being an important issue of EHR, we are seeing a more "patient-centric" approach of EHR from countries around the world. Researchers have reported on issues in EHR sharing including concerns on privacy and security, consumer empowerment, competition among providers, and content standards. This study attempts to analyze prior research and to synthesize comprehensive, empirically-based conceptual models of EHR for personal use.

METHODS

We use "B2C(2B) " to represent this new behavior of EHR sharing and exchange, with "consumer" in the center stage.

RESULTS

Based on different information sharing mechanisms, we summarized the "B2C(2B) " behavior into three models, namely, the Inexpensive data media model, the Internet patient portal model and the Personal portable device model. Models each have their own strengths and weaknesses in their ways to share patient data and to address privacy and security concerns.

CONCLUSION

Personal use of EHR under the B2C(2B) model does look promising based on our study. We started to observe a trend that governments around the world are embarking on related projects. With multiple stake-holders involved, we are only beginning to understand the complexity of such undertakings.

A new fluoroscopy-free navigation device for distal interlocking screw placement

During the treatment of tibia fracture with interlocking nails, the most uncomfortable procedure is for an orthopaedic surgeon to find the location for the distal locking screws. In this study, a fluoroscopy-free non-contact navigation device was developed for the placement of distal locking screws in the tibia intramedullary nailing. This device utilizes a 3D digitization arm integrated with spatial coordinate registration module, graphical user interface module and sound-guided navigation module. The 3D digitization arm, a five-DOF passive robotic arm, was used to register the spatial coordinates of proximal and distal landmarks just before placement of the nail. The registered coordinates were then incorporated with the coordinates of the proximal landmarks after nail placement to calculate the coordinate transformation matrix. The transformed spatial coordinates of the distal screw holes were then computed in real time for interlocking nail navigation. A sound-guided navigation module was designed in which a sound with different tones and intermittence frequencies was produced, as the probe of the digitization arm navigates toward the location of distal screw holes. No intra-operative fluoroscopy was required. In vitro assessment was performed successfully with a donor bone, and a clinical case of a young male with tibia fracture was also carried out in the operating theatre. Operation time, distal screw insertion, total radiation time and accuracy of the distal interlocking screw placement were measured. The surgery was conducted under sterile conditions without complication, and the clinical course was smooth with prompt bone healing.

Effect of hormone replacement therapy on uterine fibroids in postmenopausal women—a 3-year study

OBJECTIVE

The aim of this prospective 3-year clinical study was to examine the effect of hormone replacement therapy (HRT) on uterine fibroid growth among postmenopausal women.

METHODS

Thirty-seven postmenopausal women with uterine solitary fibroids were recruited randomly for HRT in a 3-year program. All participants received 0.625 mg conjugated equine estrogen (CEE) and 5 mg medroxyprogesterone (MPA) daily. Fibroid volume was measured by transvaginal ultrasonography at baseline and then at 12-month intervals for 3 times. Clinically, significant fibroid growth was defined as an increase in volume of more than 25% compared with baseline. Also, 35 postmenopausal women with uterine fibroid were studied as control who did not receive HRT during the study period.

RESULTS

Fibroid volume had increased significantly after 1 year both in HRT users and non-users. These increases continued to the second year significantly in HRT users but not in non-users. However, the volumes declined significantly at the third year to similar levels as those measured at baseline in control. In HRT users, fibroid volume though significantly increased at the third year (vs. baseline) but declined insignificantly in comparison with the second year. Clinically, at end of the third year study, one of 34 and three of 34 women increased fibroid volume over 25% compared with baseline in HRT non-users and users, respectively.

CONCLUSIONS

HRT does increase uterine fibroid volume statistically. However, its effect appears in the first 2 years of use. The increased fibroid volume begins to decline at the third year both in HRT users and non-users. Clinically, the increased effect of HRT on uterine fibroid of postmenopausal women should be not over-emphasized at least for 3 years of usage.

A defoaming agent should be used with pronase premedication to improve visibility in upper gastrointestinal endoscopy

BACKGROUND AND STUDY AIMS

The study tested whether pronase can improve endoscopic visibility and alter the accuracy of the CLO test for H. pylori detection.

PATIENTS AND METHODS

A total of 160 patients were randomly assigned to receive one of five premedications for endoscopy: group A: dimethylpolysiloxane (DMPS) alone; group B: DMPS plus water (up to 100 ml); group C: pronase only, with 100 ml water; group D: pronase and sodium bicarbonate plus water up to 100 ml; group E: pronase, sodium bicarbonate, and DMPS, plus water up to 100 ml. Endoscopists, who were unaware of the premedication method administered, assessed visibility scores (range 1 - 4) for the antrum, lower gastric body, upper gastric body, and fundus. The higher the score, the less clear the visibility. The sum of scores from the four locations was defined as the total visibility score. A CLO test was also done during the endoscopy. One week after their endoscopy, patients in groups C, D, and E were scheduled for a (13)C-urea breath test (UBT).

RESULTS

Group E patients had a significantly lower total visibility score than those in the other four groups ( P < 0.05). Groups C and D had higher total visibility scores than the other three groups ( P < 0.05). The scores did not significantly differ between groups A and B. Based on the UBT results, the sensitivity and specificity of the CLO test were 92.6 % and 96.2 %, respectively.

CONCLUSIONS

Premedication as in group E provided the clearest endoscopic visibility. Without the application of DMPS, pronase alone cannot improve endoscopic visibility. Pronase does not influence H. pylori identification using the CLO test.

Reduction in primary nonfunction of syngeneic islet transplants with nordihydroguaiaretic acid, a lipoxygenase inhibitor

To study the effectiveness of a lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA), in the reduction of primary nonfunction, an insufficient number of syngeneic islets were transplanted underneath the renal capsule with NDGA administered daily for 4 weeks. After transplantation of the 150 islets, the decrement of blood glucose levels was significantly faster in the mice that had received NDGA than in the mice that had received no drug at all or dimethyl sulfoxide (DMSO) (p < 0.005, p < 0.05). The mean duration of temporary posttransplant hyperglycemia was 22.3 +/- 3.2 (n = 10), 35.9 +/- 2.3 (n = 14), and 33.7 +/- 4.1 (n = 6) days for the respective groups. The diabetic mice that received 300 islets had their blood glucose levels decrease faster than those that received 150 islets (19.7 +/- 1.6 vs. 35.9 +/- 2.3 days, n = 14. p < 0.0001). There was no significant difference in the blood glucose reducing effect between the mice that received 150 islets with NDGA and the mice that received 300 islets [22.3 +/- 3.2 (n = 10) vs. 19.7 +/- 1.6 (n = 14) days, p > 0.05]. The insulin content of the graft from the mice treated with 150 islets and NDGA (3.02 +/- 0.24 microg, n = 4) was higher than that from the mice that received 150 islets but no treatment (1.10 +/- 0.26 microg, n = 15, p < 0.005) or that had been treated with DMSO (1.21 +/- 0.30 microg, n = 4, p <0.05). The insulin content of the pancreas remnant had no significant differences among the three groups. The net glucose-stimulated insulin secretion was 0.82 +/- 0.14 vs. 0.20 +/- 0.10 microIU/islet x 60 min (n = 8, p < 0.005) and 0.59 +/- 0.08 vs. 0.04 +/- 0.02 microIU/islet x 60 min (n = 8, p < 0.0001) for islets cultured without NDGA vs. with NDGA at 1 and 2 weeks, respectively. However, the insulin content of the cultured islets was similar between the two groups for up to 2 weeks of incubation (at 1 week: 0.71 +/- 0.01 vs. 0.67 +/- 0.04 ng/islet, n = 8, p > 0.05; at 2 weeks: 0.71 +/- 0.02 vs. 0.80 +/- 0.07 ng/islet, n = 8, p > 0.05). Serum leukotriene B4 (LTB4) concentrations before and between the fifth and seventh days after transplantation were determined. For diabetic mice that received 150 islets, serum LTB4 levels were 25,835 +/- 3,335 and 27,631 +/- 3,136 pg/ml (n = 4, p > 0.05). For diabetic mice that received 150 islets and NDGA, the corresponding figures were 22,401 +/- 2,706 pg/ml and 27,530 +/- 2,190 pg/ml (n = 8, p > 0.05). The graft histology revealed viable islet cells and networks of close vascular structures around the islets and did not reveal microscopic differences among the samples of all four groups. In conclusion, our data revealed that daily administration of NDGA for 4 weeks enhanced isoislet engraftment and preserved three times more mass of the islet beta cells in the isografts. This result indicates that NDGA reduces primary nonfunction of islet syngeneic grafts in diabetic mice.

Influence of donor age on mouse islet characteristics and transplantation

Old donor age has been considered as a risk factor and relative contraindication for transplantation. This study was designed to investigate the influence of donor age on islet characteristics and transplantation. Islets isolated from 8 (I-A)-, 32 (I-B)-, or 64 (I-C)-week-old C57BL16 mice were studied for number, size, insulin content, and secretion. After syngeneically transplanting 300 islets under the kidney capsule of streptozotocin-diabetic mice (R-A. R-B, and R-C, respectively), we measured recipients' metabolic parameters as well as the beta-cell mass and insulin content of the graft. Eight-week-old donors had better glucose tolerance than 32- and 64-week-old donors. However, 64-week-old donors had more pancreatic insulin content than 8- and 32-week-old donors. I-B and I-C were greater in number, larger in size, and higher in insulin content than I-A. But perifusion study showed I-C secreted less insulin, albeit with a similar stimulation index compared with that of I-A and I-B. After transplantation, the fall of blood glucose in R-C was faster than that in R-A and R-B. At 12 weeks, the recipients' blood glucose, body weight, HbA1c, and the beta-cell mass and insulin content of the graft were comparable in all groups. However, R-C had better glucose tolerance than R-A. During follow-up, R-A and R-B maintained lifelong normoglycemia and their glucose tolerance did not deteriorate. These data indicate that islets isolated from donors with different ages have different characteristics and effects on transplantation. The islets isolated from aged donors are functioning well and can be a potential source for transplantation; however, because we transplanted a large islet mass from the aged donors, the role of the islet dose needs to be further clarified.

Lactate dehydrogenase genes of caiman and Chinese soft-shelled turtle, with emphasis on the molecular phylogenetics and evolution of reptiles

L-Lactate dehydrogenase (LDH) cDNAs encoding for LDH-A(4) (muscle) and LDH-B(4) (heart) isozymes from caiman (Caiman crocodilus apaporiensis) belonging to the order Crocodilia and Chinese soft-shelled turtle (Pelodiscus sinensis) belonging to the order Chelonia were sequenced. The phylogenetic relationships of the newly determined cDNA and their deduced protein sequences, as well as the previously published sequences of vertebrate LDH isozymes, were analyzed by various phylogenetic tree construction methods. These results indicated that Chelonia is indeed more closely related to Crocodilia. The divergent times between caiman and alligator, turtle and soft-shelled turtle, and Chelonia and Crocodilia were estimated to be approximately 36, 100 and 177 million years, respectively.

Two distinctive cell binding patterns by vacuolating toxin fused with glutathione S-transferase: one high-affinity m1-specific binding and the other lower-affinity binding for variant m forms

The Helicobacter pylori VacA causes large intracellular vacuoles in epithelial cells such as HeLa or RK13 cells. Two major VacA forms, m1 and m2, divergent in an approximately 300 amino acid segment within the cell binding domain P58, display distinct cell-type specificity. Sequence analysis of four vacA alleles showed that a m1-like allele (61) and two m2 alleles (62 and v226) mainly differed in the midregion and that v225, a m1m2 chimera, was a natural double crossover from v226 and another allele. Each of these alleles was expressed as a soluble GST-VacA fusion that did not form a large oligomer. The recombinant VacA portion nevertheless assembled into higher ordered structures and possessed biological binding activity similar to that of the native VacA. A direct comparison of fusion-cell binding activity showed that m1 > m1m2 > m2 in HeLa cells, whereas there were more similar activities in RK13 cells. Vacuolating analyses of three forms revealed a positive correlation between cell binding activity and vacuolating activity. Moreover, the m1-type N-terminal half portion of the midregion was crucial for HeLa cell cytotoxicity. Kinetic, Scatchard, and inhibition analyses suggested the presence of at least two receptors: a m1-type specific high-affinity receptor (K(d) = approximately 5 nM) and a common VacA receptor interacting similarly with m1, m1m2, and m2 via a lower affinity (K(d) = 45-67 nM). Expression of mainly the m1-type receptor on HeLa cells whereas both receptors on RK13 cells may account for distinct cell binding activity and therefore for cell-type specificity.

Modeling of organic pollutant destruction in a stirred-tank reactor by ozonation

Destruction of organic contaminants in water by ozonation is a gas-liquid process which involves ozone mass transfer and fast irreversible chemical reactions. Ozonation reactor design and process optimizing require the modeling of the gas-liquid interactions within the reactor. In this paper a theoretical model combining the fluid dynamic and reaction kinetic parameters is proposed for predicting the destruction rates of organic pollutants in a semi-batch stirred-tank reactor by ozonation. A simple expression for the enhancement factor as our previous work has been applied to evaluate the chemical mass transfer coefficient in ozone absorption, 2,4-dichlorophenol (2,4-DCP) and 2,6-DCP or their mixture are chosen as the model compounds for simulating, and the predicted DCP concentrations are compared with some measured data.

Liver abscess in patients with cirrhosis of the liver: a 12-year experience

PURPOSE

Liver abscess is rare in patients with cirrhosis of the liver. The aim of this retrospective study was to investigate the incidence, clinical presentation, causal pathogens, and outcome of liver abscess in cirrhotic patients.

METHODS

We collected 21 liver abscess specimens (from 14 male patients and 7 female patients; Child A: B: C, 4: 7: 10) from 22,731 admissions of 6450 cirrhotic patients, from 1986 through 1998.

RESULTS

The common clinical symptoms and signs included fever, chills, and abdominal tenderness. The major predisposing factors were biliary tract disease (52%) and diabetes mellitus (48%). The diagnosis rate with abdominal ultrasonography was 79%. Gram-negative aerobes were the predominant pathogens (Klebsiella pneumoniae, 66.7%; Escherichia coli, 23.8%), and occurred in 80% and 69% of blood and pus cultures, respectively, while 38% of cases showed polymicrobial pathogens. The location of the abscess was predominantly in the right lobe (71.4%), and 47.6% of patients had multiple abscesses. Six patients died (all with Child C cirrhosis). The overall mortality rate was 28.6% (6/21).

CONCLUSIONS

The incidence of liver abscess in the cirrhotic patients was low, at 0.09% (21/22,731 admissions). The clinical presentations and pathogens were not different from those in noncirrhotic patients, except that in our cirrhotic patients, there was no significant difference in mortality between those with monomicrobial and those with polymicrobial abscess: nor was there a significant difference in mortality between those with single and those with multiple abscesses. The Child C patients were the high-risk group.

Attenuation of insulin resistance by chronic beta2-adrenergic agonist treatment possible muscle specific contributions

A possible mechanism by which chronic clenbuterol treatment causes multiple physiological changes in skeletal muscle that leads to reduced insulin resistance in the obese Zucker rat (falfa) was investigated. Animals were gavaged with clenbuterol (CB) (0.8 mg x kg(-1) day(-1)), terbutaline (TB) (1.0 mg x kg(-1)day(-1)), or control (CT) vehicle for six weeks. Oral glucose tolerance and insulin responses were markedly improved in CB rats and impaired in TB rats. CB treatment caused a 24-34% gain in muscle mass in all muscle fiber types, and increases in 3-O-methyglucose transport (2-fold) and GLUT4 concentration (57%) in fast twitch glycolytic (FG) muscle. Oxidative capacity was reduced in both FG (47%) and fast twitch oxidative (FO) muscle (30%), but not in slow twitch oxidative (SO) muscle. Null model analysis for receptor occlusion demonstrated that most functional beta-adrenoceptors were lost in FO (82%) and FG (89%) fibers, but not in SO fibers. We propose that hypertrophy is the result of continuous direct activation of beta-adrenoceptors while loss in oxidative capacity may be the result of receptor down regulation. Improvements in insulin resistance may have been due, in part, to both increases in lean body mass and specific adaptations in FG muscle.

Diagnosis of Helicobacter pylori infection by stool antigen test in southern Taiwan

Helicobacter pylori (H. pylori) has been found to be associated with various gastrointestinal diseases. Confirmation of H. pylori infection includes invasive and non-invasive methods. There has been increasing interest in noninvasive tests recently. However, the geographical differences among H. pylori strains have been emphasized recently and the H. pylori strain in Taiwan showed a high cagA positive result and different vacA subtype when compared with those of Western countries. The aim of this study is to access and compare the reliability and the diagnostic accuracy of the stool H. pylori antigen tests by spectrophotometry and by the visual method, especially in Southern Taiwan. Thirty-two patients (18 men and 14 women; age range: 23-91 y/o, mean: 50.5 y/o) who underwent gastroendoscopy at Kaohsiung Medical University Hospital were enrolled in this study. H. pylori infection status was confirmed by culture or two positive test results on CLO test, histology and 13C-urea breath test (13C-UBT). The exclusion criteria included previous gastrointestinal tract surgery, use of antibiotics, proton pump inhibitor or compounds containing bismuth within 1 month of the study. Among them, 14 patients were with duodenal ulcer (DU), 4 with gastric ulcer (GU), 12 with non-ulcer dyspepsia, and 2 with GU and DU. Those patients had their stool collected for ELISA tests of H. pylori stool antigen (HpSA). The HpSA tests were positive in 16 of 18 patients diagnosed as H. pylori positive, and negative in 13 of 14 patients as H. pylori negative. The sensitivity and specificity were 88.9% and 92.9% respectively. The positive and negative predictive values were 94.1% and 86.7% respectively. The concordance of HpSA accessed by spectrophotometry and visual method is 100%, which makes this test even easier and cheaper. We concluded that stool HpSA test is a noninvasive, accurate, reliable, rapid and easy way to diagnose H. pylori infection in Southern Taiwan, either by spectrophotometry or by visual assessment.

A case of pulmonary endometriosis--a rare case report and a successful treatment experience

Endometriosis is a common disease found in reproductive age women, but pulmonary endometriosis is rare. We present a 21-year-old female with catamenial chest pain, chest tightness, severe cough, and hemoptysis. Though we could not find any definite intrapulmonary endometriotic lesion by computed tomography and bronchoscope, she was diagnosed to have pulmonary endometriosis due to the typical clinical symptoms. After 6 months of GnRH agonist application, the symptoms were completely relieved. She has been followed up and has been symptoms free for at least 6 months after administration of GnRH agonist.

Evaluation of an office-based urine test for detecting Helicobacter pylori: a Prospective Pilot Study

BACKGROUND/AIMS

To ascertain the reliability of a newly developed office-based urine test, the RAPIRUN test, used for detection of H. pylori infection.

METHODOLOGY

Urine specimens from 142 consecutive patients undergoing gastroendoscopy (77 men, 65 women; mean 52.0 years) were tested with RAPIRUN at the same time. The total reaction time for the urine test is 20 min. None of the patients had received any H. pylori eradicating treatment. The H. pylori status was evaluated based on 5 different tests: culture, histology, biopsy urease test, 13C-urea breath test, and the RAPIRUN test. A commercial office-based kit using an immunochromatographic technique was used to examine urine samples for H. pylori antibody. H. pylori status was defined as positive when the culture was positive or if 2 of the other 3 tests (histology, biopsy urease test, and 13C-urea breath test were positive.

RESULTS

Of 93 patients with H. pylori infection, 88 were tested as positive by RAPIRUN (sensitivity 94.6%). Of 48 patients without infection, 43 were found to be negative by RAPIRUN (specificity 89.6%). One case with an invalid urine test was excluded.

CONCLUSIONS

This urine test is a rapid, inexpensive, reliable and easy-to-use tool for the diagnosis of H. pylori infection in untreated patients. It can be used for mass screening of patients' H. pylori status, particularly in children, postgastrectomy patients, uncooperative patients, and patients undergoing bismuth or proton pump inhibitor treatment.

Endotracheal tube fires during carbon dioxide laser surgery on the larynx--a case report

Endotracheal tube (ETT) fire is a catastrophic disaster that may occur during laser surgery of the upper airway. Several means are available for protection of polyvinyl chloride (PVC) tube from fire, but they are not perfect in prevention of fires caused by laser beam. The PVC tube is hazardous for carbon dioxide (CO2) laser surgery if it is not well wrapped with metallized foil tape. We report a case that a PVC ETT wrapped with aluminum foil ignited during CO2 laser surgery of the larynx. In this report, we emphasize the shaft of the PVC tube must be completely wrapped with aluminum foil to prevent exposure of any surface if it is used in CO2 laser surgery of the upper aero digestive tract.

Performance and simulation of ozone absorption and reactions in a stirred-tank reactor

This research investigates the mass transport of gaseous ozone accompanied by decomposition and ozonation reactions in the liquid phase. Absorption experiments were carried out under semibatch mode by continued injection of gaseous ozone into an agitated vessel containing an aqueous solution of 2,4- or 2,6-dichlorophenol at 25 degrees C. Under the influence of a fast reaction between the dissolved ozone and dichlorophenol, the mass transfer rate of ozone is enhanced greatly resulting in rapid destruction of the dichlorophenol. Simulations of the experimental results suggest that the complete mixing model can be applied to describe the fluid flow patterns in both the gas and liquid phases. The results of this study indicate that dichlorophenols can be removed effectively from aqueous solutions of pH near neutrality and that there is little additional advantage in carrying out the treatment process in alkaline solutions.