Analog modulation by the flexoelectric effect in liquid crystals.

We have solved the long-standing problems of stability and hysteresis, and we are able to obtain the homogeneous uniform lying helix structure in polymer-free cholesteric liquid crystals. This is instrumental for the present work to demonstrate the analog modulation at high speed and high precision. The device is configured for the transverse field switching wherein the substrate surface is flat. In addition to the response time of 10 ms at room temperature, we have obtained the R-squared and the adjusted R-squared as a measure of true sine wave for the sinusoidal responding transmissions from 1 Hz to 100 kHz that are all greater than 0.9993. In a Michelson interferometer, the phase shift at wavelength 633 nm after two passes has been measured to be equal to about $\pi /{9}$π/9 at 4.6 V/µm for the chiral-doped nematic mixtures E7.

Immunosuppressive therapy in acute myocarditis: an 18 year systematic review.

BACKGROUND: Immunosuppressive therapy is reportedly ineffective in adults with acute myocarditis. AIMS: To systematically review the impact of immunosuppressive therapy on the outcome of acute myocarditis in children. METHODS: A literature search for articles published from 1984 to 2003 was conducted with the following keywords: myocarditis, dilated cardiomyopathy, and immunosuppression. The relevant studies were systematically reviewed and comparison of treatment effect was made by calculating the odds ratio (OR) and confidence interval (CI) using the exact method based on the exact discrete reference distribution. RESULTS: Of the 1470 articles found, only nine studies were eligible. The odds for improvement with immunosuppression was between 4.33 (95% CI 0.52 to 52.23) and 2.7 (95% CI 0.59 to 14.21). Addition of a second immunosuppressive agent to prednisolone only proved effective in one randomised controlled trial (OR 0.09, 95% CI 0.01 to 0.52). Heterogeneity of these studies precluded pooled odds ratio. CONCLUSION: Current data suggest that immunosuppressive therapy does not significantly improve outcomes in children with acute myocarditis and there is insufficient evidence for its routine use. However, statistical power to detect a significant difference in the treatment effect may be limited because of the small number of subjects. This, together with problems of diagnosis, varying treatment practices, and a relative lack of evidence based guidelines would support efforts for a large multicentre, randomised controlled trial to better define the role of immunosuppression in acute myocarditis.

Stimulation of chloride secretion by baicalein in isolated rat distal colon.

The effect of baicalein on mucosal ion transport in the rat distal colon was investigated in Ussing chambers. Mucosal addition of baicalein (1-100 microM) elicited a concentration-dependent short-circuit current (I(sc)) response. The increase in I(sc) was mainly due to Cl(-) secretion. The presence of mucosal indomethacin (10 microM) significantly reduced both the basal and subsequent baicalein-evoked I(sc) responses. The baicalein-induced I(sc) were inhibited by mucosal application of diphenylamine-2-carboxylic acid (100 microM) and glibenclamide (500 microM) and basolateral application of chromanol 293B (30 microM), a blocker of K(v)LQT1 channels and Ba(2+) ions (5 mM). Treatment of the colonic mucosa with baicalein elicited a threefold increase in cAMP production. Pretreating the colonic mucosa with carbachol (100 microM, serosal) but not thapsigargin (1 microM, both sides) abolished the baicalein-induced I(sc). Addition of baicalein subsequent to forskolin induced a further increase in I(sc). These results indicate that the baicalein evoked Cl(-) secretion across rat colonic mucosa, possibly via a cAMP-dependent pathway. However, the action of baicalein cannot be solely explained by its cAMP-elevating effect. Baicalein may stimulate Cl(-) secretion via a cAMP-independent pathway or have a direct effect on cystic fibrosis transmembrane conductance regulator.

Analysis of P wave and P dispersion in children with secundum atrial septal defect.

BACKGROUND: P maximum and P dispersion are evaluated as predictors of paroxysmal atrial fibrillation in adults. In this study, these variables are being investigated in children with secundum ASD in comparison with that of normal controls and in relation to size of ASD and the presence or absence of atrial dilation. METHODS: Ninety-four children with isolated secundum ASD (33 boys, 60 girls; mean +/- SD age at diagnosis 2.9 +/- 4.1 years) and 65 age-matched controls (mean +/- SD age 4.2 +/- 4.2 years) were evaluated. Resting 12-lead ECG was used to measure P waves from which P maximum and P dispersion (difference between maximum and minimum P-wave duration) were derived. ASD children were arbitrarily subgrouped according to ASD sizes (small: 1-3 mm, moderate: 4-7 mm, large: > or = 8 mm). The presence of right atrial dilation was noted from echocardiography. RESULTS: Children with ASD had significantly longer mean P dispersion compared to controls (P dispersion: 30.2 +/- 11.1 vs 26.4 +/- 6.6 ms, P = 0.008). Mean P maximum and P dispersion were significantly prolonged with increasing ASD size (P < 0.001). Children with right atrial dilation had significantly longer P maximum (102.3 +/- 15.2 vs 82.8 +/- 13.4 ms, P < 0.001) and larger P dispersion (36.1 +/- 12.5 vs 27.6 +/- 9.4 ms, P = 0.003) compared to those without right atrial dilation. CONCLUSION: Prolonged atrial conduction time and inhomogeneity of atrial conduction may possibly be present in children with moderate to large sized ASD and in those with atrial dilation.

An unusual encounter of a "cobra" in the heart: rare appearance of an Amplatzer Septal Occluder.

This article presents the unusual appearance of a "cobra" due to "acute bending" of the proximal part and partial opening of the distal part of the left atrial disk of an Amplatzer Septal Occluder during the process of transcatheter closure of a secundum atrial septal defect in a 6-year-old boy. The possible reasons and method to overcome this technical problem, which resulted in successful occlusion of the atrial septal defect, are discussed.

Heart rate variability of children with mitral valve prolapse.

Studies have indicated that adult patients with mitral valve prolapse (MVP) may have autonomic dysfunction. The purpose of this study was to evaluate heart rate variability (HRV) in children with MVP. Sixty-seven children with MVP (ages 6 to 18 years; 30 boys and 37 girls) were consecutively studied and subdivided into those with or without symptoms. Thirty-seven normal age-matched children (17 boys and 20 girls) were studied as controls. The patients were further divided into 4 age subgroups. HRV was measured using a 24-hour Holter electrocardiogram (ECG) system (Laser SXP Holter Analysis System, Marquette Electronics, Milwaukee, WI). The ECGs were analyzed in both time domain and frequency domain (spectral analysis). Symptomatic and asymptomatic children with MVP were combined for analysis because they were not significantly different in terms of their HRV. All time-domain indices, with the exception of SDANN (SD of the mean of RR intervals in all 5-minute segments of the 24-hour ECG), were significantly lower in children with MVP than in controls. Children with MVP showed significantly lower spectral power of the high frequency (HF) and low frequency (LF) components when compared with controls. The ratio of LF to HF (LF/HF) was significantly higher in children with MVP. Similar differences were observed in the 4 age subgroups. Sex differences in HRV were observed when girls had lower HRV compared with boys. Lower time-domain and frequency-domain indices of HRV in children with MVP are suggestive of decreased parasympathetic activity and a shift in sympathovagal balance. Various factors including differences in heart rate may contribute to sex differences in HRV.

Influence of surgery on aortic valve prolapse and aortic regurgitation in doubly committed subarterial ventricular septal defect.

Doubly committed subarterial ventricular septal defects should be closed surgically once aortic valve deformity is present before the onset of aortic regurgitation.

Bidirectional cavopulmonary anastomosis.

The Fontan operation has been used to palliate patients with a functional single ventricle. In many such patients the operative risk for a Fontan procedure is high. The bidirectional cavopulmonary anastomosis (BCPA) is a useful intermediate palliative procedure before Fontan correction. It may reduce the deleterious sequelae of chronic hypoxaemia and long-term ventricular overload, thus yielding a more suitable Fontan candidate. We reviewed our experience of 9 patients with univentricular hearts who were at the time of the BCPA not considered suitable candidates for conventional Fontan operation. Two patients had double inlet right ventricle (DIRV) with pulmonary stenosis (PS) and ventricular septal defect (VSD), 2 had univentricular heart, 4 had tricuspid atresia (TA) and hypoplastic right ventricle (RV), 1 patient had atrioventricular septal defect (AVSD) with double outlet right ventricle (DORV) with hypoplastic RV. Two of the 9 patients had bilateral superior vena cavae. All except one had undergone prior palliative operations. The mean age at BCPA was 4.7 years (range 1.5 years to 6 years) and the mean weight at surgery was 15 kg (range 7 to 22 kg). There were no operative deaths. The mean hospitalization stay was 8.5 days (range 5 to 13 days) with a mean follow up of 14 months. Median oxygen saturation improved from 78.7 +/- 6.3% to 85.9 +/- 3.9%. The BCPA is a useful palliative procedure to stage Fontan type reconstruction in selected patients with univentricular hearts.

Outcome of surgical closure of doubly committed subarterial ventricular septal defect.

BACKGROUND: From 1986 to March 1997, 128 patients diagnosed to have doubly committed subarterial ventricular septal defects (VSD) were reviewed. Patients with aortic regurgitation (AR), and aortic valve (AV) deformity or a large left-to-right shunt across the VSD were offered operation. Forty-five patients (27 men, 18 women) agreed to surgical closure of their VSDs. METHODS: Thirty-eight patients had VSD closure alone, and 7 had an additional AV repair. Other associated defects corrected at operation were closure of atrial septal defects, closure of other ventricular septal defects, ligation of patent ductus arteriosus, and repair of ruptured sinus Valsalva aneurysm. RESULTS: There was no mortality nor major morbidity associated with operation. In the 26 patients with AR and AV deformity preoperatively, valve repair was performed in 6 patients. The condition of AR improved in 4, and remained unchanged in 22 patients. In the 10 patients with a deformity of the AV and no AR preoperatively, the condition remained unchanged in 5 patients, from whom 1 had valve operation, but progressed in 5 patients postoperatively at a mean follow-up of 6.4 years. In 9 patients with no deformity of the AV and no AR preoperatively, there was no postoperative AR and no progress of valve deformity. CONCLUSIONS: Excellent results were obtained with VSD closure and AV repair. Surgical closure of VSD, if performed before the onset of AV deformity, may prevent progressive AR. If AV repair is performed after the onset of AV deformity, progressive AR may not always be prevented.

Value of abdominal sonography in the assessment of children with abdominal pain.

PURPOSE: We retrospectively evaluated the usefulness of sonography in the diagnostic assessment of children with abdominal pain. METHODS: From July 1988 to October 1996, 676 children who had abdominal pain and were referred for sonography underwent abdominal and pelvic sonographic examination. Of these, 644 children had recurrent abdominal pain (RAP) and 32 children had acute or subacute abdominal pain (ASAP). The mean ages and relative risks of underlying abnormalities were calculated for children with RAP and ASAP. RESULTS: Abdominal abnormalities were sonographically detected in 10 children with RAP (2%), a significantly lower incidence than in children with ASAP (56%, p < 0.0001), with a relative risk of 0.028 (95% CI, 0.014-0.055). In the RAP group, an underlying abnormality was more likely (p < 0.001) to be sonographically detected in children who had atypical clinical features (5 of 46%; 11%) than in those with typical clinical features (5 of 598; 1%), with a relative risk of 12.94 (95% CI, 3.90-43.30). Children with RAP were found to have hydronephrosis (3), urinary cystitis (2), duplex kidney (1), hypoplastic low-lying kidney (1), choledochal cyst (1), ovarian teratoma (1), and gross gaseous distention with fecal masses (1). Children with ASAP had urinary cystitis (4), intussusception (2), appendicitis (2), appendiceal abscess (1), perforated gut with ascites (1), gut duplication (1), thickened gut wall with fluid from severe gastroenteritis (1), gross gaseous distention with fecal masses (1), hepatosplenomegaly (1), cholecystitis (1), gross hydronephrosis (1), Wilms' tumor (1), and abdominal neuroblastoma (1). CONCLUSIONS: Abdominal sonography is useful in children with ASAP. Although an underlying abnormality was rarely found in children with RAP, children who have RAP with atypical clinical features should have sonographic screening. If no abnormalities are found, the normal sonograms may be reassuring to parents.

Simultaneous transcatheter valvuloplasty and Amplatzer septal occlusion for pulmonary valvar stenosis and secundum atrial septal defect.

Transcatheter balloon valvuloplasty had been established as the treatment of choice in patients with pulmonary valvar stenosis. Non surgical closure of secundum atrial defects by various occlusive devices is currently being evaluated. We report the first successful simultaneous transvenous Mansfield balloon dilation and Amplatzer septal occlusion in a 7-year-old girl with moderately severe pulmonary valvar stenosis and secundum atrial defect in April 1997. Satisfactory reduction of pressure gradient across pulmonary valve and complete obliteration of left to right atrial shunt were achieved.

Transcatheter occlusion of atrial septal defects: an initial experience with the Amplatzer septal occluder.

OBJECTIVE: To discuss the initial experience with the use of a new double disc occluding device, the Amplatzer septal occluder in transcatheter occlusion of secundum atrial septal defects (ASD). METHODS: Transvenous sizing of secundum ASD was performed in five children under general anaesthesia using transoesophageal echocardiographic and fluoroscopic guidance. An Amplatzer septal occluder equal to or minimally larger than the stretched diameter of the ASD was used for transcatheter occlusion of the defect in three suitable patients. Pulmonary balloon valvuloplasty with a 18 mm x 3 cm Mansfield balloon catheter was carried out in one patient with associated pulmonary valvar stenosis in the same procedure setting. RESULTS: Stretched diameters of the defects in the three patients ranged from 14 to 17 mm. Devices of sizes 14, 17 and 17 were deployed through 7F and 8F sheaths, respectively. The upper and lower rims of interatrial septum were more than 8 mm in all patients. All patients had successful occlusion with complete obliteration of the atrial left to right shunting. Simultaneous pulmonary balloon valvuloplasty for the valvar stenosis reduced pressure gradient from 53 mmHg to 22 mmHg across the valve prior to septal occlusion in one patient. No intraprocedural or short-term complication was encountered. CONCLUSIONS: The design of the Amplatzer septal occluder permits ease in loading, delivery, deployment and stable seating of the device. This initial experience shows that Amplatzer device occlusion is feasible, relatively safe and effective and appears to be a viable alternative to surgical closure of secundum atrial septal defects in properly selected patients.

Determinants of patient choice of medical provider: a case study in rural China.

This study examines the factors that influence patient choice of medical provider in the three-tier health care system in rural China: village health posts, township health centres, and county (and higher level) hospitals. The model is estimated using a multinomial logit approach applied to a sample of 1877 cases of outpatient treatment from a household survey in Shunyi county of Beijing in 1993. This represents the first effort to identify and quantify the impact of individual factors on patient choice of provider in China. The results show that relative to self-pay patients, Government and Labour Health Insurance beneficiaries are more likely to use county hospitals, while patients covered by the rural Cooperative Medical System (CMS) are more likely to use village-level facilities. In addition, high-income patients are more likely to visit county hospitals than low-income patients. The results also reveal that disease patterns have a significant impact on patient choice of provider, implying that the ongoing process of health transition will lead people to use the higher quality services offered at the county hospitals. We discuss the implications of the results for organizing health care finance and delivery in rural China to achieve efficiency and equity.

Physician response to Medicare fee reductions: changes in the volume of coronary artery bypass graft (CABG) surgeries in the Medicare and private sectors.

The demand inducement hypothesis predicts that physicians will respond to reductions in their income by increasing the volume of their services when the income effect is strong and negative. I test for such inducement in the market for coronary artery bypass grafting (CABG), using a longitudinal panel of physicians in New York and Washington states. The results show that physicians whose incomes were reduced the most by Medicare fee cuts performed higher volumes of CABGs, and they did so in both the Medicare and private markets.

Signal-averaged electrocardiography in healthy children: relationship with age, sex, and anthropometry.

Signal-averaged electrocardiograms (SAECGs) have been found to be influenced by sex and anthropometry in adults. The purpose of this study was to evaluate this relationship in children. Total filtered QRS duration (TQRS), duration of high-frequency, low-amplitude signals in the terminal portion of the QRS complex that were less than 40 microV (HFLA) root-mean-square voltage in the last 40 ms of the filtered QRS (RMS40) were determined by high-resolution electrocardiographic (ECG) recording (MAC 15 ECG System, Marquette Electronics, Milwaukee, WI). These parameters were correlated with age, sex, body weight, height, relative weight, body mass index, and body surface area. As HFLA and RMS40 were not normally distributed, they were logarithmically transformed for regression analysis. The best subset multiple regression procedure was used to evaluate the variables that would optimally influence SAECG measurements and to obtain regression equations for the prediction of each SAECG parameter. Although univariate analysis shows that almost all the body characteristics and age are significantly correlated with SAECGs, multiple regression analysis reveals that TQRS is significantly influenced by height (P < .0001), relative weight (P = .012), and body mass index (P = .041); HFLA is influenced by weight (P = .001), height (P = .004), and body mass index (P = .001); and RMS40 is influenced by height (P < .0001) and relative weight (P = .001). Sex is noted to significantly influence both TQRS and RMS40 (P < .0001, P = .002, respectively), while HFLA is found to be significantly related to age (P = .001). In summary, SAECGs in Chinese children are shown to be influenced by height, weight, and relative weight or body mass index, but not body surface area, while age and sex also significantly contribute to the variation of some SAECG parameters.

Purification and characterization of ferredoxin-sulfite reductase from turnip (Brassica rapa) leaves and comparison of properties with ferredoxin-sulfite reductase from turnip roots.

Ferredoxin-sulfite reductase (Fd-SiR) [hydrogen-sulfide: ferredoxin oxidoreductase, EC 1.8.7.1] from turnip leaves (SiR-L) has been purified to homogeneity and its enzymatic properties compared with that from turnip roots (SiR-R). Each enzyme had a molecular mass of 64.5 +/- 0.5 kDa by SDS-PAGE and an isoelectric point of 5.15 +/- 0.05. Although each had a pH optimum around 7.8 with the same effects of inhibitors, SiR-L had higher heat stability at 60 degrees C than SiR-R. Moreover, SiR-R had a lower K(m) and a higher specificity constant (kcat/K(m)) for turnip leaf ferredoxin than SiR-L. The N-terminal amino acid sequence of SiR-L was different from that of SiR-R. The results of amino acid analysis and peptide mapping suggested that SiR-L and SiR-R have different primary structures.

Efficient polarization converter for projection displays.

In the waveguiding limit, a twisted nematic liquid crystal cell behaves as an achromatic polarization rotator. We propose and demonstrate the application of such a polarization rotator to convert unpolarized light into linearly polarized light with almost 100% efficiency. This polarization converter has a 2:1 aspect ratio, which is close to the 16:9 ratio for modern televisions. It can be used therefore in a projection display with polarization-dependent light valves such as a liquid crystal light valve. Both transmittive and reflective light valves can be used. The temperature dependence of the achromatic polarization rotator is also studied.