Verification of thermal analysis codes for modeling solid rocket nozzles

One of the objectives of the Solid Propulsion Integrity Program (SPIP) at Marshall Space Flight Center (MSFC) is development of thermal analysis codes capable of accurately predicting the temperature field, pore pressure field and the surface recession experienced by decomposing polymers which are used as thermal barriers in solid rocket nozzles. The objective of this study is to provide means for verifications of thermal analysis codes developed for modeling of flow and heat transfer in solid rocket nozzles. In order to meet the stated objective, a test facility was designed and constructed for measurement of the transient temperature field in a sample composite subjected to a constant heat flux boundary condition. The heating was provided via a steel thin-foil with a thickness of 0.025 mm. The designed electrical circuit can provide a heating rate of 1800 W. The heater was sandwiched between two identical samples, and thus ensure equal power distribution between them. The samples were fitted with Type K thermocouples, and the exact location of the thermocouples were determined via X-rays. The experiments were modeled via a one-dimensional code (UT1D) as a conduction and phase change heat transfer process. Since the pyrolysis gas flow was in the direction normal to the heat flow, the numerical model could not account for the convection cooling effect of the pyrolysis gas flow. Therefore, the predicted values in the decomposition zone are considered to be an upper estimate of the temperature. From the analysis of the experimental and the numerical results the following are concluded: (1) The virgin and char specific heat data for FM 5055 as reported by SoRI can not be used to obtain any reasonable agreement between the measured temperatures and the predictions. However, use of virgin and char specific heat data given in Acurex report produced good agreement for most of the measured temperatures. (2) Constant heat flux heating process can produce a much higher heating rate than the radiative heating process. The results show that heating rates of 125 C/s (225 F/s) can be achieved. (3) The electrical resistance of the FM 5055 samples were about 150 Omega in the virgin state, and decreased to about 35 Omega when charred. A reliable scheme must be developed to electrically insulate the composite from the heater foil in order to prevent any current leakage into the sample which can result in volumetric heating of the char zone of the composite

Serum CA15-3 measurement in breast cancer patients before and after mastectomy

Background: Much research is being carried out to find a tumor marker for early diagnosis of breast cancer when the lesion is still small. CA15-3, a glycoprotein, is one candidate with probable use as tumor marker in breast cancer. Objective: We conducted this study to analyze the relationship between serum levels of CA15-3 and several variables including age, clinical stage, and the number of lymph nodes involved in breast cancer patients. Methods: One hundred and thirty-six females including 39 normal controls, 54 patients with benign lesions, and 43 with malignant lesions entered this study. A second and third sample was obtained from patients who were diagnosed as having breast cancer, one week and one month postmastectomy, respectively. CA15-3 was measured by ELISA. Results: The number of patients in the malignant group (6 out of 43) with elevated CA15-3 levels was higher than that in the normal controls (3 out of 39) and patients with benign lesions (1 out of 54). Forty percent of patients in stages II and III had a higher frequency of abnormal CA15-3 values, whereas 13 of those in stage I disease did so. One week after mastectomy, the mean ± SD serum CA15-3 was 18.3 ± 14.6 U/mL. However, a month later, the mean ± SD was 21.7±19.7 U/mL, which was approximately the same as the preoperative values (mean ± SD: 22.1 ± 25.6 U/mL). There was an abnormal elevation in CA15-3 values when �4 lymph nodes were involved. The correlation between the elevated CA15-3 values and the number of involved lymph nodes was significant (P < 0.001). Analysis of the CA15-3 values showed a sensitivity of 14.0 and a specificity of 92.3. The positive and negative predictive values were 66.7 and 49.3, respectively. The relative efficiency was 1.8. Conclusion: In this study, CA15-3 was found to have no value in the screening for early diagnosis of breast cancer. We observed a strong correlation between elevated CA15-3 levels and the progression of breast cancer

Blunt traumatic aortic injury: Initial experience with endovascular repair

ObjectivesEndovascular treatment of traumatic aortic injury (TAI) is an alternative to open repair (OR) in patients with blunt trauma. We report our initial experience after integration of endovascular repair using thoracic devices.MethodsA retrospective review of a prospectively collected institutional trauma registry was performed. Between September 2005 and November 2008, 71 patients with TAI presented to our institution. Based on imaging, TAIs were classified into grade 1-4 in severity. These included: grade 1, intimal tear; grade 2, intramural hematoma; grade 3, aortic pseudoaneurysm; and grade 4, free rupture. Initial management included resuscitation, blood pressure control, and treatment of associated injuries. After stabilization, all patients were considered for thoracic endovascular aortic repair (TEVAR) using a thoracic device. If contraindicated, candidates underwent OR. Outcome measures were mortality, stroke, paraplegia, intensive care unit (ICU), and hospital stay.ResultsThe mean age was 39.8 years, with 50 males. The mean injury severity score (ISS) was 42.6. Nineteen (27%) patients with a mean ISS of 60 died shortly after arrival prior to any vascular intervention. Ten (14%) patients with grade 1 injuries were managed medically. The remaining 42 (59%) patients with grade 2 and 3 injuries underwent repair. Median interval between admission and repair was 4.3 days (range, 0-109 days). Fifteen (21%) patients with a mean ISS of 34.4 underwent OR with no mortality, stroke, or paraplegia. Twenty-seven (38%) patients with a mean ISS of 36.7 underwent TEVAR with no mortality or paraplegia. One TEVAR patient suffered a perioperative stroke. Twenty-two patients had a TAG (W.L. Gore & Associates, Flagstaff, Ariz) device. Four patients had a Talent Thoracic (Medtronic Vascular, Santa Rosa, Calif), and 1 patient had an Excluder (W.L. Gore) device. The left subclavian artery was covered in 13 (48%) patients. Patients who underwent TEVAR were older than those who had OR (47.8 vs 31.1 years, P < .006). The aortic diameter proximal to the injury was larger in the TEVAR group (24.4 vs 19.6 mm, P < .0001). There was no difference in the mean ICU or hospital length of stay between the two groups. Mortality correlated with the ISS score (P < .0001). Median follow-up time was 19.4 months (range, 0-27). Only 56% of the TEVAR patients were fully compliant with their surveillance imaging protocol.ConclusionIn this initial experience, the results of TEVAR did not differ from OR. Long-term follow-up is required to determine the effectiveness of this treatment strategy. Adherence to follow-up imaging protocols is challenging in this patient population. Next generation devices will make TEVAR applicable to a wider range of patients

Intravenous Paracetamol Versus Patient-Controlled Analgesia With Morphine for the Pain Management Following Diagnostic Knee Arthroscopy in Trauma Patients: A Randomized Clinical Trial

Background: Most patients undergoing outpatient surgeries have the unpleasant experience of high level pain after surgery. Compared with open surgeries, arthroscopic procedures are less painful; however, inadequate pain management could be associated with significant concerns. Opioids alone or in combination with local anesthetics are frequently used for diminishing postoperative pain using intravenous or epidural infusion pumps. Despite morphine various disadvantages, it is commonly used for controlling pain after surgery. Objectives: The aim of this study was to compare intravenous paracetamol and patient-controlled analgesia (PCA) with morphine for the pain management following diagnostic knee arthroscopy in trauma patients. Patients and Methods: Sixty trauma patients who were scheduled to undergo knee arthroscopy were randomly divided into two groups. Patients immediately received intravenous infusion of 1 g paracetamol within 15 minutes after surgery and every 6 hours to 24 hours in the paracetamol group. The patient-controlled analgesia group received morphine through PCA infusion pump at 2 mL/h base rate and 1mL bolus every 15 minutes. Pain level, nausea and vomiting, and sedation were measured and recorded during entering the recovery, 15 and 30 minutes after entering the recovery, 2, 6, and 24 hours after starting morphine pump infusion in the morphine and paracetamol in the paracetamol groups. Results: There was no significant difference regarding the pain level at different times after entering the recovery between the two groups. No one from the paracetamol group developed drug complications. However, 22.3% in the PCA morphine suffered from postoperative nausea; there was a statistically significant difference regarding the sedation level, nausea, and vomiting at various times between the two groups. Conclusions: Intravenous administration of paracetamol immediately after knee arthroscopy improved postoperative pain, decreased analgesic administration, maintained stable hemodynamic parameters, had no complications related to opiates, no nausea and vomiting, and increased patient satisfaction and comfort in comparison to PCA with morphine

Lower use of carotid artery imaging at minority-serving hospitals

Objective: We determined whether site of care explains a previously identified racial disparity in carotid artery imaging. Methods: In this retrospective cohort study, data were obtained from a chart review of veterans hospitalized with ischemic stroke at 127 Veterans Administration hospitals in 2007. Extensive exclusion criteria were applied to obtain a sample who should have received carotid artery imaging. Minority-serving hospitals were defined as the top 10% of hospitals ranked by the proportion of stroke patients who were black. Population level multivariate logistic regression models with adjustment for correlation of patients in hospitals were used to calculate predictive probabilities of carotid artery imaging by race and minority-service hospital status. Bootstrapping was used to obtain 95% confidence intervals (CIs). Results: The sample consisted of 1,534 white patients and 628 black patients. Nearly 40% of all black patients were admitted to 1 of 13 minority-serving hospitals. No racial disparity in receipt of carotid artery imaging was detected within nonminority serving hospitals. However, the predicted probability of receiving carotid artery imaging for white patients at nonminority-serving hospitals (89.7%, 95% CI [87.3%, 92.1%]) was significantly higher than both white patients (78.0% [68.3%, 87.8%] and black patients (70.5% [59.3%, 81.6%]) at minority-serving hospitals. Conclusions: Underuse of carotid artery imaging occurred most often among patients hospitalized at minority-serving hospitals. Further work is required to explore why site of care is a mechanism for racial disparities in this clinically important diagnostic test

Does Inclusion of Stroke Severity in a 30-day Mortality Model Change Standardized Mortality Rates at VA Hospitals?

Background—The Centers for Medicare and Medicaid Services is considering developing a 30-day ischemic stroke hospital-level mortality model using administrative data. We examined whether inclusion of the National Institutes of Health Stroke Scale (NIHSS), a measure of stroke severity not included in administrative data, would alter 30-day mortality rates in the Veterans Health Administration. Methods and Results—A total of 2562 veterans admitted with ischemic stroke to 64 Veterans Health Administration Hospitals in the fiscal year 2007 were included. First, we examined the distribution of unadjusted mortality rates across the Veterans Health Administration. Second, we estimated 30-day all-cause, risk standardized mortality rates (RSMRs) for each hospital by adjusting for age, sex, and comorbid conditions using hierarchical models with and without the inclusion of the NIHSS. Finally, we examined whether adjustment for the NIHSS significantly changed RSMRs for each hospital compared with other hospitals. The median unadjusted mortality rate was 3.6%. The RSMR interquartile range without the NIHSS ranged from 5.1% to 5.6%. Adjustment with the NIHSS did not change the RSMR interquartile range (5.1%–5.6%). Among veterans ≥65 years, the RSMR interquartile range without the NIHSS ranged from 9.2% to 10.3%. With adjustment for the NIHSS, the RSMR interquartile range changed from 9.4% to 10.0%. The plot of 30-day RSMRs estimated with and without the inclusion of the NIHSS in the model demonstrated overlapping 95% confidence intervals across all hospitals, with no hospital significantly below or above the mean-unadjusted 30-day mortality rate. The 30-day mortality measure did not discriminate well among hospitals. Conclusions—The impact of the NIHSS on RSMRs was limited. The small number of stroke admissions and the narrow range of 30-day stroke mortality rates at the facility level in the Veterans Health Administration cast doubt on the value of using 30-day RSMRs as a means of identifying outlier hospitals based on their stroke care quality

Correlation of inpatient and outpatient measures of stroke care quality within veterans health administration hospitals

Background and Purpose—Quality of care delivered in the inpatient and ambulatory settings may be correlated within an integrated health system such as the Veterans Health Administration. We examined the correlation between stroke care quality at hospital discharge and within 6 months postdischarge. Methods—We conducted a cross-sectional hospital-level correlation analyses of chart-abstracted data for 3467 veterans discharged alive after an acute ischemic stroke from 108 Veterans Health Administration medical centers and 2380 veterans with postdischarge follow-up within 6 months in fiscal year 2007. Four risk-standardized processes of care represented discharge care quality: prescription of antithrombotic and antilipidmic therapy, anticoagulation for atrial fibrillation, and tobacco cessation counseling along with a composite measure of defect-free care. Five risk-standardized intermediate outcomes represented postdischarge care quality: achievement of blood pressure, low-density lipoprotein, international normalized ratio, and glycosylated hemoglobin target levels, and delivery of appropriate treatment for poststroke depression along with a composite measure of achieved outcomes. Results—Median risk-standardized composite rate of defect-free care at discharge was 79%. Median risk-standardized postdischarge rates of achieving goal were 56% for blood pressure, 36% for low-density lipoprotein, 41% for international normalized ratio, 40% for glycosylated hemoglobin, and 39% for depression management and the median risk-standardized composite 6-month outcome rate was 44%. The hospital composite rate of defect-free care at discharge was correlated with meeting the low-density lipoprotein goal (r=0.31; P=0.007) and depression management (r=0.27; P=0.03) goal but was not correlated with blood pressure, international normalized ratio, glycosylated hemoglobin goals, nor with the composite measure of achieved postdischarge outcomes (probability values >0.13). Conclusions—Hospital discharge care quality was not consistently correlated with ambulatory care quality