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C H Mielke

Publications and source records attributed to C H Mielke.

At least 19 recordsLinked to original sources
PubMed2004

Null orbital frustration at the pseudogap boundary in a layered cuprate superconductor.

We assess the relative importance of orbital frustration at the pseudogap closing field H(pg). Using interlayer tunneling transport in pulsed magnetic fields nearly up to 60 T, we track the field-temperature (H-T) phase diagram for fields parallel ( parallel ab) and normal ( parallel c) to the layered structure of Bi(2)Sr(2)CaCu(2)O(8+y). In contrast to large orientational anisotropy of the superconducting state related to the orbital motion of Cooper pairs, we find anisotropy of H(pg) temperature independent and small, due solely to the g factor. The obtained Zeeman relation with the pseudogap temperature T small star, filled, g( parallel c)micro(B)H( parallel c)(pg)=g( parallel ab)micro(B)H( parallel ab)(pg) approximately k(B)T small star, filled, is fully consistent with the correlations only in the spin channel.

Journal Article↗
PubMed2001

Thermal activation between Landau levels in the organic superconductor beta(")-(BEDT-TTF)2SF5CH2CF2SO3.

We show that Shubnikov-de Haas oscillations in the interlayer resistivity of the organic superconductor beta(")-(BEDT-TTF)2SF5CH2CF2SO3 become very pronounced in magnetic fields approximately 60 T. The conductivity minima exhibit thermally activated behavior that can be explained simply by the presence of a Landau gap, with the quasi-one-dimensional Fermi surface sheets contributing negligibly to the conductivity. This observation, together with complete suppression of chemical potential oscillations, is consistent with an incommensurate nesting instability of the quasi-one-dimensional sheets.

Journal Article↗
PubMed2001

Field-induced dynamic diamagnetism in a charge-density-wave system.

ac susceptibility measurements of the charge-density-wave (CDW) compound alpha-(BEDT-TTF)(2)-KHg(SCN)(4) at magnetic fields, mu0H >23 T, above its Pauli paramagnetic limit, reveal unambiguously that the magnetic hysteresis observed previously within this CDW phase is diamagnetic and can only be explained by induced currents. It is argued that the ensemble of experimental techniques amounts to a strong case for dissipationless conductivity within this phase.

Journal Article↗
PubMed2001

Coronary artery calcium, coronary artery disease, and diabetes.

Diabetes is a known risk factor for cardiovascular disease, which is the leading cause of death in the US. Most sufferers are unaware that they have coronary artery disease, and death is often quite sudden. Electron beam computed tomography (EBCT) is a non-invasive procedure that detects coronary artery disease (CAD) by measuring the amount of coronary artery calcium (CAC). We employ this procedure to study the effect of diabetes on CAC. EBCT was employed to measure the amount of coronary artery calcium in a population of 3389 patients referred to the Spokane Coronary Artery Center. This was a cross-sectional study. The average and median CAC values were computed for two groups of patients, namely those with diabetes and those without. Patients were also divided by gender and five age groups (0-39, 40-49, 50-59, 60-69, and >69 years). The mean and median CAC values were much larger for those with diabetes compared to those without for all age groups and in both sexes. Both men and women with diabetes have a greater plaque burden, when compared to a population with coronary artery disease with no history of diabetes. This plaque burden is greater in males than in females. CAC may play a useful role in following the progression of CAD in patients with diabetes, as well as evaluating the influence of risk factor intervention and diabetic control.

Adolescent↗
PubMed2001

Risk factors and coronary artery disease for asymptomatic women using electron beam computed tomography.

BACKGROUND: Cardiovascular disease (CVD) is the leading cause of death for men and women in the United States. In 1995, 58,200,000 people were estimated to have the disease, claiming 960,592 lives, while 481,287 people died of coronary artery disease (CAD). Most people are unaware they have CAD, and death is often quite sudden. With more women surviving to old age, the absolute number of women dying from CVD exceeds that of men. METHODS: The study is cross-sectional. Electron beam computed tomography (EBCT) was employed to measure the amount of coronary artery calcium (CAC), a marker for CAD, in a population of patients referred to the Spokane Coronary Artery Center. A questionnaire was administered at the time of the patient's visit, when exposure to traditional risk factors was assessed. The effect of traditional risk factors on CAC was then determined. RESULTS: The effect of past smoking on CAC was evident, the effect of total cholesterol on CAC was moderate, while a history of hypertension appears to have an effect on the disease for older women. CONCLUSIONS: EBCT measurements of CAC can detect the effect of traditional risk factors on CAD and can be used to manage the disease in women.

Adult↗
PubMed2000

The use of time step simulations and difference equations (TSSADEQ) in modeling heparin pharmacokinetics.

A model in which the clearance of heparin requires the binding of heparin to a finite and regenerated pool of binding was constructed using time step simulations and difference equations (TSSADEQ). A simulation of a heparin i.v. bolus demonstrated a dose-dependent, triphasic pharmacokinetic curve with (1) an initial log-linear phase representing first-order association of heparin with binding sites, (2) an intermediate plateau phase representing constant regeneration of heparin binding sites, and (3) a terminal log-linear phase occurring when the quantity of regenerated sites exceeded the remaining heparin. Sensitivity analysis based on the literature produced estimates of the k at 1.39 to 2.77 h-1, the pool of binding sites of 50 units/kg, and the regeneration rate of 15 to 20 unit/kg/h--virtually identical to the empirically derived guidelines for the bolus size and infusion rate for unfractionated heparin. A pilot study of bolus dosing of unfractionated heparin in normal volunteers confirmed the model.

Adult↗
PubMed1999

Direct measurement of unfractionated heparin using a biochemical assay.

A number of investigations have noted that functional biological assays for heparin are not always reliable and may not reflect the actual biochemical level of heparin in patients receiving anticoagulant therapy. This creates the possibility that patients receiving anticoagulant treatment may have an excess or deficiency of circulating levels of heparin. To address this problem, we have developed a direct biochemical measurement of heparin. The heparin assay uses fluorophore-assisted carbohydrate electrophoresis (FACE) to directly measure the predominate disaccharide of unfractionated heparin. In this study, unfractionated heparin was measured in vitro throughout a wide range of heparin concentrations in plasma. Seven in vivo pharmacokinetic studies in five normal subjects given 3,000 USP units of unfractionated heparin intravenously showed a three-phase elimination process with higher peak plasma levels and shorter elimination times than predicted from previous studies. At these doses, heparin is largely eliminated intact through urinary excretion. Body weight has a significant effect on heparin kinetics. When we compared the direct biochemical assay with two biological clotting assays, we found the latter can overestimate biochemical heparin concentrations. The FACE assay, due to its sensitivity, is also able to measure circulating levels of endogenous heparin in plasma and urine. Direct heparin measurement using the FACE technique is practical and useful for studies of the correlation of biochemical and biological activities.

Animals↗
PubMed1996

Inter-rater reliability of electron beam computed tomography to detect coronary artery calcification.

The electron beam computed tomography (EBCT) provides a safe, rapid, and noninvasive means to detect the presence and quantitate the deposition of calcium in the coronary arteries. To examine the inter-rater reliability of a coronary calcification screen using the EBCT, films from 50 subjects were scored by two technicians. The number, volume, and calcification scores were determined for each artery as well as a total score of coronary calcification. When scan results were interpreted qualitatively (all scores > 10 classified as positive) there was complete agreement between raters in identifying the 22 cases with a positive total scan, and only one instance of discrepancy in identifying positive results for specific arteries. When scores for the 32 cases with non-zero calcium scores were analyzed quantitatively, inter-rater correlation coefficients of 0.98 or higher were observed for the total scan scores and for scores in three of four arteries. In only four cases did the total scan scores from the two raters differ by more than 10%. Therefore, evidence suggests that EBCT films can be reliably scored, enhancing their potential usefulness in the early detection of coronary atherosclerosis.

Adult↗
PubMed1996

Comparison of 10, 20, and 40 level electron beam computed tomography studies for coronary calcium.

There are increasing data to support the use of the electron beam computed tomography (EBCT) scanner for early detection of coronary artery disease (CAD). A negative scan essentially rules out significant disease. How many EBCT 3 mm contiguous slices are needed to cover the coronary circulation? To answer this question, 104 consecutive patients referred for EBCT scan for evaluation of coronary artery calcium (CAC) were asked to participate. The sensitivity and negative predictive value (NPV) of calcium scores for the first 10 slices and first 20 slices, the second 20 slices, and the total scan were recorded. Scores greater than one were regarded as positive. The number of levels required to cover the entire heart was also recorded. Fifty-nine patients (56.7%) had a positive calcium score for the total scan. Of these, 53 were positive for the first 10 slices (sensitivity = 89.8%, NPV 88.2%), and 57 were positive for the first 20 slices (sensitivity = 96.6%, NPV 95.7%). The median number of levels required to cover the entire heart was 34, and 97.2% of cases were covered in 40 or fewer levels. The use of 20 slices for purposes of detecting CAC is a reasonable choice for the C-100 scanners, because this would be accomplished in a breath hold. When the first slice starts at the base of the right pulmonary artery, all patients with CAC were identified. The C-150 scanner with the ability to scan on each heartbeat would increase sensitivity and NPV by acquiring 30 to 40 slices in a single breath hold.

Adult↗
PubMed1995

Reliability of electron beam computed tomography to detect coronary artery calcification.

Electron beam computed tomography (CT) provides a safe, rapid, and noninvasive means to detect the presence and quantitate the deposition of calcium in the coronary arteries. To examine the reproducibility of a coronary calcification screen using electron beam CT, 50 subjects underwent two studies, averaging 12 minutes between studies. The number, volume, and calcification scores were determined for each artery as well as a total score of coronary calcification. Thirty-four of the 50 subjects had evidence of coronary calcification. The reliability score for total coronary artery calcification was 0.99. The reliability score for the total number of lesions and total volume was at or above 0.98. There were 8 cases in which a negative calcium score on retest was positive or where a positive calcium score on retest was negative. In both instances, the amount of calcium detected was very small. Therefore, evidence suggests that electron beam CT is reliable in the detection of coronary artery calcification and may be a useful tool for the early detection of coronary atherosclerosis before flow impairment.

Calcinosis↗
PubMed1995

The right ventricle in mitral regurgitation: evaluation by electron beam tomography.

Mitral valve regurgitation affects heart ventricle volumes, which can be accurately measured by electron beam tomography (EBT). Most studies have focused on the left ventricle, but findings have failed to resolve some crucial clinical issues. We reviewed EBT studies of 35 patients with moderate mitral valve regurgitation but no ischemia, aortic valve regurgitation, or left ventricular failure to investigate the relationship between right ventricle volumes and ejection fraction and extent of mitral regurgitation. EBT in cine mode was performed during exercise and at rest in 839 patients from 1990-1994. Sixty-one of these showed evidence of significant mitral regurgitation, 35 of whom met the criteria for inclusion in this study. Left and right end-diastolic and end-systolic volumes were computed from the scans, and ventricular stroke volumes, ejection fractions, regurgitant stroke volume, and regurgitant fraction were computed from these values. Correlation coefficients between ventricular values and regurgitant fraction were computed. Regurgitant fraction was significantly and negatively associated with the ejection fraction in the right ventricle (r = -0.55, p < 0.001) but not in the left. Ten of the 35 patients studied had right ventricular ejection fractions of less than 45%. In addition, there was evidence for a subgroup of cases with moderate amounts of regurgitation and dilation of the right ventricle. It is concluded that reduced right ventricular ejection fraction is a common finding in patients with mitral regurgitation without left ventricular failure. It is most commonly observed in cases with large regurgitant fraction and/or with a large right ventricular end-diastolic volume/left ventricular end-diastolic volume ratio. Identification of mitral regurgitation patients with reduced right ventricular ejection fraction may have clinical significance, indicating a sub-group of patients with more severe disease prior to the development of left ventricular dysfunction.

Aged↗
PubMed1993

Pectus carinatum successfully treated with bracing. A case report.

We report the case of a 14 year old girl who desired treatment for a cosmetically objectionable pectus carinatum deformity. She was initially managed with a corrective underarm body cast for six weeks followed by full-time bracing for seven months. Subsequently, she was braced only at night for another eight months. Seven years after the onset of treatment she had an excellent result without recurrence of deformity. In a well-motivated, skeletally immature individual bracing can be an effective treatment for cosmetically displeasing pectus carinatum.

Adolescent↗
PubMed1989

Surgical treatment of adolescent idiopathic scoliosis. A comparative analysis.

Three hundred and fifty-two patients had a one-stage posterior spinal arthrodesis between 1960 and 1984 using one of four types of instrumentation: a Harrington distraction rod, Harrington distraction and compression rods, Harrington distraction and compression rods with a device for transverse traction, and a Harrington distraction rod with sublaminar wires. All of the patients were female (age-range, eleven to nineteen years), and all had idiopathic scoliosis with a single right or double thoracic curve. The minimum length of follow-up was two years. No significant difference was found among the four groups relative to the amount of correction that was obtained at operation or maintained two years after operation. An average of 13.5 per cent of correction was lost during follow-up in the patients who were treated with postoperative immobilization, and an average of 27 per cent was lost in the patients who were treated with sublaminar wires without immobilization. The use of a straight Harrington rod reduced normal thoracic kyphosis, the addition of a compression rod corrected hyperkyphosis, and the use of a rod with sublaminar wires corrected thoracic hypokyphosis or thoracic lordosis.

Adolescent↗