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W L Johnson

Publications and source records attributed to W L Johnson.

At least 19 recordsLinked to original sources
PubMed2005

A universal criterion for plastic yielding of metallic glasses with a (T/Tg) 2/3 temperature dependence.

Room temperature (TR) elastic constants and compressive yield strengths of approximately 30 metallic glasses reveal an average shear limit gammaC=0.0267+/-0.0020, where tauY=gamma CG is the maximum resolved shear stress at yielding, and G the shear modulus. The gammaC values for individual glasses are correlated with t=TR/Tg , and gamma C for a single glass follows the same correlation (vs t=T/Tg). A cooperative shear model, inspired by Frenkel's analysis of the shear strength of solids, is proposed. Using a scaling analysis leads to a universal law tauCT/G=gammaC0-gammaC1(t)2/3 for the flow stress at finite T where gammaC0=(0.036+/-0.002) and gammaC1=(0.016+/-0.002).

Journal Article↗
PubMed2001

Procedural outcomes and long-term survival among patients undergoing percutaneous coronary intervention of a chronic total occlusion in native coronary arteries: a 20-year experience.

OBJECTIVES: The study compared procedural outcomes and long-term survival for patients undergoing percutaneous coronary intervention (PCI) of a chronic total coronary artery occlusion (CTO) with a matched non-CTO cohort to determine whether successful PCI of a CTO is associated with improved survival. BACKGROUND: Percutaneous coronary intervention of a CTO is a common occurrence, and the long-term survival for patients with successful PCI of a CTO has not been clearly defined. METHODS: Between June 1980 and December 1999, a total of 2,007 consecutive patients underwent PCI for a CTO. Utilizing propensity scoring methods, a matched non-CTO cohort of 2,007 patients was identified and compared to the CTO group. The cohorts were stratified into successful and failed procedures. RESULTS: The in-hospital major adverse cardiac event (MACE) rate was 3.8% in the CTO cohort. Technical success has improved over the last 10 years (overall 74.4%, slope 1.0%/yr, p = 0.02, R2 = 49.9%) as did procedural success (overall 69.9%, slope 1.2%/yr, p = 0.02, R2 = 51.5%) without a concomitant increase in in-hospital MACE rates (slope 0.1%/yr, p = 0.7). There was a distinct 10-year survival advantage for successful CTO treatment compared with failed CTO treatment (73.5% vs. 65.1%, p = 0.001). The CTO versus non-CTO 10-year survival was the same (71.2% vs. 71.4%, p = 0.9). Diabetics in the CTO cohort had a lower 10-year survival compared with nondiabetics (58.3% vs. 74.3%, p < 0.0001). CONCLUSIONS: These data represent follow-up of the largest reported series of patients undergoing PCI for a CTO. The 10-year survival rates for matched non-CTO and the CTO cohorts were similar. Success rates have continued to improve without an accompanying increase in MACE rates. A successfully revascularized CTO confers a significant 10-year survival advantage compared with failed revascularization.

Angioplasty, Balloon, Coronary↗
PubMed1996

Results of direct percutaneous transluminal coronary angioplasty in octogenarians.

Direct percutaneous transluminal coronary angioplasty (PTCA) has emerged as effective reperfusion therapy for acute myocardial infarction; however, few data exist on its use in octogenarians. Thrombolytic therapy in this age group has reduced early mortality from approximately 30% to 20%, but is associated with an increased risk of stroke and major hemorrhage. We analyzed the acute and long-term results of direct PTCA performed on patients aged > or = 80 years at our institution between 1980 and 1993. The study group consisted of 55 patients (mean patient age 83.3 +/- 2.3 years). Infarcts were anterior in 27 patients (49%). Cardiogenic shock was present in 6 patients (11%). The mean time to reperfusion was 4.3 +/- 2.8 hours. Direct PTCA was successful in 53 patients (96%). There were no emergent bypass operations. In-hospital death occurred in 9 patients (16%), including 4 of 6 (67%) presenting in cardiogenic shock and 5 of 49 (10%) who were hemodynamically stable on presentation. Repeat PTCA for recurrent ischemia was performed in 6 patients (11%). There were no strokes during hospitalization. Bleeding complications requiring blood transfusion were present in 4 patients (7%). Thirty-day mortality was 16% and 1-year actuarial survival was 67%. Direct PTCA in patients aged > or = 80 years can be performed safely with a high procedural success rate. The clinical outcome with PTCA in this high risk subset of patients compares favorably with that reported previously for both thrombolytic and medical therapy.

Actuarial Analysis↗
PubMed1996

Global linkages in animal agriculture: new opportunities for United States agricultural universities.

Today's rapidly changing world offers new opportunities for Departments of Animal Science that wish to expand their international activity. Seeking a relevant role in the definition of sustainable agriculture, internationalizing courses and curricula for all students, supporting private sector enterprises at home and abroad (export promotion), maintaining collaboration with former students, and providing better information to our farmers and citizens about world conditions: these are some of the challenges now facing us. A survey of heads of departments of animal science at universities in the United States revealed that of 64 respondents, almost all report significant international activities. However, only 20% are satisfied with their present activity level, and 80% intend to seek an expanded international role. The expected benefits from international activity most often mentioned were a broadened faculty experience and a better capacity to prepare students for the 21st century. Anticipated problems are related to faculty and departmental recognition, faculty career trajectories, and continuity of work assignments. On balance, respondents overwhelmingly believe that expected benefits outweigh possible problems. Eighty percent of respondents reported a generally supportive attitude from their administration, but 75% indicated that the department itself needs to provide leadership in the search for new international linkages.

Agriculture↗
PubMed1994

Directional atherectomy of left main stenoses.

Balloon angioplasty (PTCA) of left main (LM) stenoses is limited by frequent clinical restenosis. Directional coronary atherectomy (DCA) may be an effective alternative to PTCA due to its ability to achieve a greater postprocedural luminal diameter when treating bulky, eccentric plaques and aorto-ostial lesions. We analyzed the acute and long-term results following 24 DCA procedures in 22 patients with "protected" LM lesions. Acute success (residual stenosis < or = 40%, no major ischemic complications) was 88% overall, 100% in 13 planned procedures, and 73% in 11 adjunctive DCA procedures that followed suboptimal PTCA. Mean LM stenosis was reduced from 86% to 13% (P < 0.01). There were no procedural complications directly attributed to DCA. At a mean of 24 +/- 3 months, the clinical restenosis rate was 16%, survival was 100%, and event-free survival (freedom from death, MI, or repeat lesion-related interventions) was 89%. We conclude that DCA in protected LM lesions (1) can achieved excellent angiographic results with low procedural complication rates, (2) may succeed where PTCA yields suboptimal results, and (3) may provide late clinical outcomes superior to those of balloon angioplasty.

Angioplasty, Balloon, Coronary↗
PubMed1994

Initial and long-term outcome of 83 patients after balloon angioplasty of totally occluded bypass grafts.

OBJECTIVES: This study was designed to evaluate the safety and short- and long-term results of coronary angioplasty of totally occluded bypass grafts in patients with clinical conditions other than acute myocardial infarction. BACKGROUND: Total occlusion of bypass grafts after coronary artery surgery often causes recurrent ischemia. The safety and results of percutaneous transluminal coronary angioplasty in occluded bypass grafts are controversial. METHODS: All patients with dilation of a totally occluded bypass graft attempted between 1981 and 1991 were retrospectively identified from a data base. Patients treated in the setting of an acute myocardial infarction were excluded. Eighty-three patients met these criteria and constitute the study group. Hospital records, office charts and procedural reports were reviewed in all patients to supplement details available in the data base. RESULTS: The time from bypass surgery to attempted coronary angioplasty ranged from 1 to 226 months (mean time 88 months). The mean (+/- SD) duration of graft occlusion was 31 +/- 46 days (range 1 to 180). In 27 attempts the bypass graft was the only site dilated, and in 56 attempts (68%) one to six other sites (n = 101) were dilated. Angiographic success (< or = 40% residual lumen stenosis) was achieved in 61 grafts (73%) and 98 of the additional sites (97%) (p < 0.001). Major complications included one procedural death and two Q wave infarctions. Follow-up for a mean of 32 months demonstrated a 1- and 3-year actuarial survival rate of 94% and 80%, respectively. At 3 years, only 34% of patients were free of repeat angioplasty or surgery. CONCLUSIONS: Angioplasty of totally occluded bypass grafts can be successful in the majority of selected patients, although major complications can occur. Strategies for sustained patency are needed to improve the long-term results.

Aged↗
PubMed1993

Failed direct coronary angioplasty for acute myocardial infarction: in-hospital outcome and predictors of death.

OBJECTIVES: The purpose of this study was to compare the mechanisms, predictors and outcome of patients with failed direct coronary angioplasty of the infarct-related artery with those in patients with successful direct angioplasty. BACKGROUND: Direct coronary angioplasty of the infarct-related artery, without antecedent thrombolytic therapy, is an effective treatment for patients with acute myocardial infarction. Concern has been expressed over high mortality rates in patients with failed direct infarct angioplasty. METHODS: All patients treated by angioplasty were prospectively entered into a computer data base. The characteristics and outcome of all patients with failed direct angioplasty were reviewed and compared with those of patients with successful direct angioplasty. RESULTS: Direct angioplasty was successful in 705 (94%) of 750 patients and unsuccessful in 45 (6%). Patients in the failure group were more likely to be in cardiogenic shock (22% vs. 7%, p < 0.003), to have had a previous myocardial infarction (44% vs. 28%, p < 0.03) and to have three-vessel coronary artery disease (44% vs. 23%, p < 0.003). Age, gender, ejection fraction, previous bypass surgery and diabetes mellitus were similar in both groups. Only the presence of multivessel coronary artery disease (p < 0.004) and cardiogenic shock (p < 0.025) were independent predictors of failed direct angioplasty. In-hospital death (31% vs. 4.8%, p < 0.001) and the need for emergency coronary artery bypass surgery (27% vs. 0.5%, p < 0.0001) were more frequent in patients with unsuccessful than in patients with successful direct angioplasty. Patients with failed direct angioplasty and in-hospital death usually had multiple high risk characteristics, including cardiogenic shock (50%), previous myocardial infarction (43%) and multivessel coronary artery disease (93%). CONCLUSIONS: Direct coronary angioplasty is an effective method for establishing reperfusion in acute myocardial infarction. Procedural failure is infrequent, usually occurring in patients with high risk baseline characteristics.

Adult↗
PubMed1992

Myocardial salvage with direct coronary angioplasty for acute infarction.

To assess the changes in myocardial function following direct coronary angioplasty, we evaluated 323 consecutive patients undergoing coronary angioplasty without antecedent thrombolytic therapy for acute myocardial infarction. Left ventricular function was evaluated using contrast ventriculography immediately preangioplasty and at the time of predismissal follow-up angiography (a mean of 7 days after infarction). The global ejection fraction increased from 52.6% to 58.9% (p less than 0.0005). Multivariate correlates of improved global left ventricular function included baseline ejection fraction less than or equal to 45%, and a patent infarct vessel at the time of predischarge follow-up angiography. Systolic function in the infarct zone improved by a mean of 30%. Logistic regression analysis identified sustained infarct vessel patency and anterior myocardial infarction as multivariate correlates of improved regional function in the infarct zone. In patients presenting with baseline ejection fractions less than or equal to 40%, the mean ejection fraction increased from 28% to 42%. Long-term survival was compromised in patients with global ejection fractions of less than or equal to 40% at the time of dismissal. Thus significant improvement in left ventricular function can be expected in the majority of patients undergoing direct infarct angioplasty. The myocardial salvage appears to be most significant in patients suffering large infarctions, and in those with sustained infarct vessel patency.

Aged↗
PubMed1992

Effects of compensatory growth on some body component weights and on carcass and noncarcass composition of growing lambs.

A trial was conducted in 1983 and repeated in 1984 to measure effects of restricted feed intake and realimentation on weights of organs and on carcass and noncarcass composition. A total of one hundred six weaned lambs from two breeds (Timahdit and D'man) and a breed cross (Ile de France x D'man) were used in both years. Lambs were allotted to one of six feed intake regimens: HH (ad libitum access to feed from 21 to 30 kg); HM (ad libitum access to feed from 21 to 26 kg then 70% ad libitum to 30 kg); MH (70% ad libitum from 21 to 26 kg then ad libitum to 30 kg); MM (70% ad libitum from 21 to 30 kg); LH (restricted to lose weight from 21 to 17 kg then ad libitum to 30 kg); and LM (restricted to lose weight from 21 to 17 kg then 70% ad libitum to 30 kg). Weights of visceral organs and mesenteric and kidney fat showed dramatic responses to alteration of feed allowances. After recovery from 20% live weight loss, weight of liver equaled or exceeded that of both the ad libitum and 70% refed lambs. Mesenteric and kidney fat did not. Refeeding was accompanied by an increase in water (P less than .05) and a decrease in fat (P less than .01) of both carcass and noncarcass components. These results indicate that weight loss of lambs incurred during feed shortage was largely in internal organ weights, and that these lambs can recover these losses during realimentation and undergo compensatory growth with better feed efficiency and lean carcasses.

Adipose Tissue↗
PubMed1992

Effects of undernutrition and refeeding on weights of body parts and chemical components of growing Moroccan lambs.

Forty-four intact, male lambs (20 Timahdit and 24 D'man) were used to assess the effects of 22% (from approximately 25 to approximately 20 kg) and 31% (from approximately 25 to approximately 17 kg) live weight loss and the subsequent refeeding to initial BW on changes in body components. Body composition was determined using a serial slaughter technique at 17, 20, and 25 kg live weight during normal growth, weight loss, and refeeding phases. Reduction in live weight from 25 to 20 kg was associated with greater loss of visceral organs (30%) and internal fat (75%) than carcass loss (19%). Further body weight loss (from 20 to 17 kg) involved carcasses to a greater extent than internal organs. The composition of BW loss consisted of 53% water, 28% fat, and 15% protein. Refeeding was associated with a rapid increase in organ weights and less fat regeneration. Although total internal organs recovered only 90% of their original weight, liver and kidneys regained all their weight. At the same slaughter weight, carcass and noncarcass components of refed lambs were leaner because of lower fat content in these components.

Adipose Tissue↗
PubMed1992

Orthopedic experience in a MASH unit in postwar Iraq.

The orthopedic experience of a U.S. Army MASH unit deployed in southern Iraq is discussed. Seventy major casualties were surgically treated in a short time span. A high percentage of extremity trauma was observed (69%). Many patients had multiple extremity involvement. The emergency wartime surgical treatment of four specific types of trauma is explored. A new algorithm is presented for the rapid evaluation of penetrating joint injuries. We summarize the current concepts of war surgery as they apply to orthopedic injuries, and add specific observations from this experience.

Hospitals, Military↗
PubMed1991

Safety and efficacy of percutaneous transluminal coronary angioplasty in patients with left ventricular dysfunction.

The risks and long-term outcome after 845 elective percutaneous transluminal coronary angioplasties (PTCA) in patients with left ventricular (LV) dysfunction (ejection fraction less than or equal to 40%) were examined. Procedural results were compared with 8,117 consecutive procedures in patients with ejection fractions greater than 40%. The patients with LV dysfunction were older (63 vs 60 years, p less than 0.01), had a greater incidence of prior myocardial infarction (84 vs 45%, p less than 0.001), prior bypass surgery (39 vs 21%, p less than 0.001), 3-vessel disease (62 vs 33%, p less than 0.001), and class IV angina (48 vs 41%, p less than 0.01) than the control group. Angiographic success was lower (93 vs 95%, p less than 0.01), and overall procedural mortality was increased ( 4 vs 1%, p less than 0.001) in the study group. Emergency surgery rates were identical (2%). No significant difference was found in rates of nonfatal Q-wave myocardial infarction (2 vs 1%). At mean follow-up of 33.5 months, 15% of the patients with LV dysfunction required late bypass surgery, 27% underwent repeat PTCA, and 59% were angina free. Actuarial survival at 1 and 4 years was 87 and 69%, respectively. Cox regression analysis identified 3-vessel disease, age greater than or equal to 70 years, class IV angina and incomplete revascularization as correlates of long-term mortality. These data suggest that PTCA may be an effective treatment for coronary artery disease in patients with LV dysfunction.

Adolescent↗
PubMed1991

Results of multivessel percutaneous transluminal coronary angioplasty in persons aged 65 years and older.

Between 1981 and 1990, 1,373 patients, aged greater than or equal to 65 years (mean 71.2 +/- 4.9), underwent 1,640 multivessel percutaneous transluminal coronary angioplasty (PTCA) procedures. Of these, 224 patients (13.6%) had a left ventricular ejection fraction less than or equal to 40%, 412 (25.1%) had prior coronary artery bypass grafting (CABG) and 48 (2.9%) had left main artery dilatation. Of the 1,640 PTCA procedures, 697 were in patients with 2-vessel disease and 943 were in patients with 3-vessel disease. A mean 3.5 lesions were dilated per patient, with an overall angiographic success rate of 96%. Complete revascularization was achieved in 857 (52%). A total of 52 patients (3.2%) had a major in-hospital complication: 27 patients (1.6%) died, 24 (1.4%) had a Q-wave myocardial infarction, and 14 (0.8%) underwent emergent CABG. Stepwise logistic regression analysis identified ejection fraction less than or equal to 40% (p less than or equal to 0.001), 3-vessel disease (p less than or equal to 0.01), female gender (p less than or equal to 0.02), and PTCA between 1981 and 1985 (p less than or equal to 0.05) as independent predictors of mortality. Of the 1,373 patients, 1,023 have been followed for greater than or equal to 1 year (mean follow-up 32.5 +/- 21.3 months). There were 156 (15.2%) late deaths, 81 (7.9%) recurrent myocardial infarctions, and 162 (15.8%) coronary artery bypass operations. Actuarial survival, computed from the time of hospital discharge, was 92% at 1 year, 86% at 3 years and 78% at 5 years. Repeat PTCA was required in 371 patients (36.3%).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗