Use of weibull statistics to quantify property variability in TiAl alloys

Tensile experiments have been performed on specimens of four different investment-cast TiAl-based alloys with variations in casting conditions. The average ductilities obtained in these experiments vary between approximately 0.8 to 2.0 pct plastic strain to failure in tension. By using the three-parameter form of the Weibull relation, with the 0.2 pct offset yield strength as the minimum failure strength, the resulting variability in the data can be quantified and is found to be similar for those alloys with similar microstructural scale (grain size). Large variations in lamellar volume fraction, segregation, and phase distribution have a minor influence on property variability, compared to changes in the scale of the grain structure caused by either variations in cooling rate during casting or the addition of grain refiners.     

The Effect of Heat Treatment on the Mechanical Behavior of Commercially Pure Titanium and Zirconium Under Quasi-static and Dynamic Loading

The mechanical properties (stress–strain behavior) of three hexagonal metals, two grades of commercially pure titanium (CP-Ti) and zirconium (CP-Zr), are systematically characterized before and after heat treatment. Those materials are investigated under quasi-static (< 1 s⁻¹) and dynamic (> 2000 s⁻¹) tension, compression, dominant, and pure shear to draw general conclusions as to the effect of the same heat treatment and, specifically, dynamic shear failure propensity in those hexagonal materials. The results do not reveal any consistent influence of the texture on the overall quasi-static and dynamic mechanical (stress–strain) response of the investigated materials. However, when the propensity to dynamic shear failure is specifically considered, it appears that texture variations of the CP-Ti grades have more influence than purely microstructural changes resulting from the heat treatment for both materials. When no other changes than grain growth are induced, such as in the case of CP-Zr, it appears that grain growth does not significantly affect the dynamic shear failure toughness of this material. It therefore seems like no general conclusions can be drawn as to the effect of heat treatment and associated texture changes of these three hexagonal metals on their mechanical and failure properties. Thus, despite their common crystallographic features, those materials must be considered individually rather than as belonging to the general family of hexagonal metals.

     

On the scatter in creep rupture times

We report here the results of three series of replicated creep rupture experiments carried out on copper bicrystals. The intent of this study is to investigate the scatter in creep rupture times in order to determine whether creep rupture may be viewed as an essentially deterministic phenomenon or if it contains intrinsic probabilistic features. The use of bicrystals is advantageous in such an investigation, because they are much less sensitive to the effects of loading eccentricity than poly crystalline specimens. The results indicate that where failure is due to a mixed cavitation/ductile rupture mode, the scatter in the failure times may be accounted for entirely by the effects of random variations in the experimental conditions. However when the failure mode is essentially intergranular creep cavitation, the scatter in the failure times is substantially greater than can be explained by the effects of experimental variability. This leads to the conclusion that under these conditions, the creep rupture phenomenon contains intrinsic probabilistic features. Formerly with Lehigh University, Bethlehem, PA Formerly with Lehigh University     

Anti-Thermal-Fatigue Property of 8407 Steel With Surface Aluminization and Oxidation Treatment

Thermal fatigue failure is one of the main failure forms of 8407 steel. Aiming at improving the anti-thermal-fatigue property of 8407 steel, the method of aluminization and subsequent oxidation is employed to form a complex oxide on the die surface. Thermal fatigue test was performed with the cycle heating method to compare thermal fatigue behaviors of 8407 steel samples with and without aluminization and oxidation treatment. In the test, thermal fatigue crack morphology formed on the surface was observed by scanning electron microscope (SEM) and then variations of initiating rate and propagating rate of main crack of thermal fatigue with cycles were investigated. Moreover, the thermal fatigue property was judged according to thermal fatigue main crack length and its reciprocal. Finally, the anti-thermal-fatigue mechanism of oxide film was clarified. The results show that the surface aluminization and oxidation treatment can improve both the initiating resistance and propagating resistance of thermal fatigue crack, which will improve the anti-thermal-fatigue property of 8407 steel.     

Nephrotoxicity of ritonavir

A RECOGNIZED COMPLICATION: Ritonavir is an antiprotease used in the treatment of HIV-positive patients. Among the known side effects, nephrotoxicity can be severe. We have observed acute renal failure in 8 patients. CIRCUMSTANCES: Renal failure occurs early after introducing ritonavir (3-21 days). It is often severe with major creatinine elevation. One patient was dialyzed for 16 days. In these patients, saquinavir was usually associated with ritonavir. RITONAVIR ALONE: We retrospectively analyzed creatinine levels in 87 patients treated with ritonavir without saquinavir. Twelve of these 87 patients (13.7%) developed renal failure. Creatinine clearance (Cockcroft) was reduced 116 to 71 ml/min in 12 patients. Finally, it was demonstrated in 6 patients that ritonavir can reduce creatinine clearance by 25% after only 3 days of treatment. VIGILANCE: Ritonavir has a known nephrotoxic potential. Acute renal failure may be severe and can occur with ritonavir alone or in combination with saquinavir. The pathogenic mechanism has not been demonstrated from renal biopsies or experimental studies. Renal function should be followed in these patients and risk factors controlled.     

Heart failure in utero: diagnosis and therapy

Over the past 15 years considerable advances in ultrasonography have made increasingly detailed evaluation of the human foetal heart feasible. Accordingly, the presence of cardiac failure can now be diagnosed in human foetuses during the last two thirds of pregnancy by foetal echocardiography. The underlying causes of foetal cardiac failure can be identified and prenatal treatment, if considered appropriate, can be monitored by ultrasonographic methods. Two-dimensional and M-mode echocardiography, as well as Doppler ultrasound, are equally important with respect to evaluation of foetal cardiac failure. Foetal echocardiography has contributed remarkably to broadening our understanding of the conditions and natural course of cardiac failure during prenatal life. In turn, this has led to an increasing readiness to consider new forms of prenatal treatment for foetal cardiac failure.     

Variations of cardiac cycle length in patients with coronary heart disease before and after aortic coronary bypass surgery

It is well known that variations in cardiac cycle length or heart rates may be used for noninvasive evaluation of autonomic cardiovascular control. The investigation uses an original procedure. The data for analysis of cardiac cycle length variations (CCLV) are those obtained regularly at follow-up intervals, random 24-hour Holter 2-lead ECG recordings for 5 sec, and simultaneously calculated continuous sequence of mean heart rate. With the procedure, the correlations of CCLV with the parameters reflecting the early postoperative status of patients with CHD, including acute myocardial infarction, acute heart failure, rhythm and conduction disturbances, as well as age, operative stress, concurrent diseases. The findings are of both diagnostic and predictive value at subsequent stages of CHD treatment.     

Pattern of cardiac failure in Northern Savanna Nigeria

A prospective study of 315 cases of cardiac failure admitted to the General Hospital at Katsina, in the northern savanna region of Nigeria, is presented and the pattern emerged is compared with that of the southern forest region of the country. Although the diseases causing cardiac failure were similar in these two areas, their incidence and pattern showed wide variations. Cardiomyopathies were the commonest cause (47%) of cardiac failure in the northern savanna, congestive cardiomyopathy being the predominant type (31%). Endomyocardial fibrosis (EMF) commonly encountered in the south, was absent in the north; Peripartum Cardiac Failure (PPCF), rarely reported from the south, formed the commonest cause of cardiac failure among the females in the north. Rheumatic heart diseases (RHD) showed a uniform distribution throughout the country. Anaemia caused a higher percentage (13%) of cardiac failure in the north. Hypertension caused relatively fewer (12%) cardiac failures. The variations in the pattern of cardiac failure in these two areas of Nigeria are probably partly attributable to geographic geo-climatic, socio-economic, ethnic and cultural differences.     

Kinin-mediated coronary nitric oxide production contributes to the therapeutic action of angiotensin-converting enzyme and neutral endopeptidase inhibitors and amlodipine in the treatment in heart failure

Increasing evidence suggests that angiotensin-converting enzyme (ACE) inhibitors can increase vascular nitric oxide (NO) production. Recent studies have found that combined inhibition of ACE and neutral endopeptidase (NEP) may have a greater beneficial effect in the treatment of heart failure than inhibition of ACE alone. Amlodipine, a calcium channel antagonist, has also been reported to have a favorable effect in the treatment of patients with cardiac dysfunction. The purpose of this study was to determine whether and the extent to which all of these agents used in the treatment of heart failure stimulate vascular NO production. Heart failure was induced by rapid ventricular pacing in conscious dogs. Coronary microvessels were isolated from normal and failing dog hearts. Nitrite, the stable metabolite of NO, was measured by the Griess reaction. ACE and NEP inhibitors and amlodipine significantly increased nitrite production from coronary microvessels in both normal and failing dog hearts. However, nitrite release was reduced after heart failure. For instance, the highest concentration of enalaprilat, thiorphan, and amlodipine increased nitrite release from 85 +/- 4 to 156 +/- 9, 82 +/- 7 to 139 +/- 8, and 74 +/- 4 to 134 +/-10 pmol/mg (all *p <.01 versus control), respectively, in normal dog hearts. Nitrite release in response to the highest concentration of these two inhibitors and amlodipine was reduced by 41% and 31% and 32% (all #p <.01 versus normal), respectively, in microvessels after heart failure. The increase in nitrite induced by either ACE or NEP inhibitors or amlodipine was entirely abolished by Nw-nitro-L-arginine methyl ester, HOE 140 (a B2-kinin receptor antagonist), and dichloroisocoumarin (a serine protease inhibitor) in both groups. Our results indicate that: 1) there is an impaired endothelial NO production after pacing-induced heart failure; 2) both ACE and NEP are largely responsible for the metabolism of kinins and modulate canine coronary NO production in normal and failing heart; and 3) amlodipine releases NO even after heart failure and this may be partly responsible for the favorable effect of amlodipine in the treatment of heart failure. Thus, the restoration of reduced coronary vascular NO production may contribute to the beneficial effects of these agents in the treatment of heart failure.     

Using sound dental principles to salvage the compromised implant case

Implant failure can usually be determined by biologic and biomechanical factors that were not addressed during treatment planing and case design. In order to salvage the failing implant-supported prosthesis, these factors must be identified and corrected. Long-term success can only be achieved when prosthetic design, osseous and soft tissue architecture, and implant biomechanics are diagnosed and corrected.     

A new perspective on the relationship between communication impairment and disempowerment following head injury in information exchanges

Transcranial doppler sonography is a diagnostic tool that allows the noninvasive study of intracranial circulation. In patients with aneurysmal subarachnoid hemorrhage, cerebral vasospasm is promptly diagnosed, even before clinical related symptoms. Feeding arteries of an arteriovenous cerebral malformation can be detected and their variations can be correlated to the treatment (neurosurgical and/or neuroradiological). When raised intracranial pressure (namely in head trauma), transcranial doppler sonography depicts vasospasm and/or typical variations of the waveforms, suggesting intracranial circulatory arrest.     

Persistent and hyperplastic primary vitreous syndrome. Clinical and therapeutic aspects

PURPOSE: Persistent hyperplastic primary vitreous (PHPV) is a rare developmental malformation of the eye. This anomaly is usually unilateral and unassociated with other disease. PHPV may have clinical variations: an anterior and/or a posterior one. Diagnosis and treatment are exposed in our paper. METHODS: We study 38 eyes in 34 patients. All patients had an anterior form of PHPV. Nine of them associated a posterior form. Eighteen eyes underwent surgery, the mean postoperative follow-up is 4.7 years. Treatment is discussed, depending on the initial form of PHPV. We report the evolution of the surgical eyes and the untreated eyes. RESULTS: Slit lamp examination and echographic findings (A-scan and B-scan) support the diagnosis. In some cases computed tomography or RMN can be useful. If the cataract is mild in the anterior form of PHPV, treatment of amblyopia and frequent clinical examination can be sufficient. If the cataract is dense, a lensectomy must to be performed. The surgical technique can be difficult. For the eyes with posterior PHPV, the surgical treatment is to be avoided, because of high risk of retinal detachment. CONCLUSION: PHPV may have clinical variations, mostly with cataract as major sign. In purely anterior presentation, in absence of marked microphthalmos, lensectomy can be useful.     

A method of estimating the numbers of human and mouse immunoglobulin V-genes

Mutations in immunoglobulin V-genes can be due to gene multiplication, allelic variations, mutations induced by antigens or somatic mutations, etc., and various combinations of these. Since the number of different mouse lambda light V-gene nucleotide sequences is relatively small, a pairwise comparison between these sequences can provide a rough idea as to the contributions of the above mechanisms to the number of nucleotide differences between sequences. A plot of occurrences against the number of differences suggests that differences between one to five can be attributed to somatic mutations. Six to 12 differences can be allelic. Thirteen to 17 may be due to allelic variations together with somatic mutations. Differences > 17 appear to be derived from gene multiplication. Although these numbers are most likely somewhat different in humans, they can nevertheless provide a rough guide to sort out the effect of gene multiplication. Estimations of human heavy, kappa and lambda light chain immunoglobulin V-genes are in reasonably good agreement with recent experimental studies. For mouse kappa light and heavy chains, our estimations can provide some insight to future analyses by direct sequencing of these gene segments.     

The natural history of HIV disease in haemophilia

Fulminant hepatic failure is a serious complication of acetaminophen overdose. The cascade of complications starts with an alert patient that can quickly result in hepatic coma and even death. The nurse completes a poisoning history, provides an antidote, and assesses the extent of hepatic failure from an overdose. This article uses a case study to describe the problems and nursing care for the patient with hepatic failure from acetaminophen overdose. Advanced assessment skills by the critical care nurse enable prompt recognition of postoverdose complications for early intervention and treatment. Acute care nurse practitioners, utilizing the same techniques, can develop protocols for emergency or intensive care units where these patients may be admitted and subsequently cared for.     

Management of the intraaortic balloon pump patient. Pharmacologic considerations

This article reviews the common pharmacologic agents used in conjunction with the IABP for treatment of LV failure. The complex interaction between the IABP and pharmacologic agents must be carefully monitored to optimize outcome in this critically ill patient group. It is important that ICU nurses be aware of the treatment goals and their rationale, as well as monitored parameters which detect, trend and predict the direction of hemodynamic change. By using these early indicators of hemodynamics, early information can be given to the physician and intervention can be implemented on a timely basis. Early and appropriate intervention can improve outcome in many patients and may ultimately reduce costs.     

Twenty-four-hour blood pressure profile and blood pressure responses to head-up tilt tests in Parkinson's disease and multiple system atrophy

OBJECTIVE: To investigate the 24 h blood pressure profile in patients with Parkinson's disease with intact autonomic function or with autonomic failure and patients with multiple system atrophy (MSA), and to assess whether these patients exhibit posture-related variations in blood pressure. PATIENTS AND METHODS: We studied 24 patients with Parkinson's disease (11 with autonomic failure) and 13 patients with MSA (all with autonomic failure). Autonomic failure was determined by autonomic tests. An oscillometric recorder was used for ambulatory blood pressure monitoring. Tilt-table tests were performed with a head-up tilt position of 60 degrees. RESULTS: An alteration in the normal 24 h blood pressure profile was observed in 82% of Parkinson's disease patients with autonomic failure and in 85% of those with multiple system atrophy, but not in the patients with intact autonomic function. Head-up tilt tests revealed a significantly higher supine blood pressure in Parkinson's disease patients with autonomic failure and in those with MSA than in Parkinson's disease patients with intact autonomic function. Tilting resulted in a marked fall in blood pressure in patients with MSA; in Parkinson's disease patients with autonomic failure, the fall was comparatively slighter. CONCLUSIONS: We conclude that autonomic failure contributes to the alterations in the day-night blood pressure profile that may possibly be ascribed to postural dysregulation of blood pressure. We hypothesize that nocturnal hypertension is a risk factor in the development of additional cerebrovascular disease in patients with Parkinson's disease or MSA who are affected by autonomic failure.     

Quasi-literary elements in psychotherapy.

Describes a quasi-literary aptitude with words, life-stories, and treatment sequences as a major component in the work and formation of the psychotherapist. Spelling out and systematizing therapists' often intuitive mastery of these skills is a necessary step toward better training. This quasi-literary adjunct of psychotherapeutic work is illustrated from the work of many contributors. It is argued that therapists can be trained in these skills as in the elements of a craft. Trainees in psychotherapy can be taught how to recognize the appropriate contexts for developing a climactic ending, a climactic beginning, or a theme with variations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Isolated diastolic heart failure--what is it?

Epidemiological evidence suggests that 20 to 40% of all patients with heart failure have normal systolic function. Isolated diastolic dysfunction may be the principle pathophysiological mechanism in these patients. The diagnosis of isolated diastolic heart failure is problematic and not merely based on demonstrating normal systolic function. The prognosis in isolated diastolic heart failure is more favourable than in systolic heart failure. At the present time, there is no licensed treatment for isolated diastolic heart failure and treatment is largely empirical.     

Kennedy/Kassebaum: what physicians should know about this new law

Pretreatment of milk with either sodium or calcium polystyrene sulfonate resins is useful in limiting potassium dietary intake in children with renal failure. We therefore studied the in vitro effects of Kayexalate and Calcium Sorbisterit on potassium, sodium and calcium concentrations in 3 standard formulas and in human milk. It is concluded that wide variations in the final potassium, sodium and calcium concentrations can be observed according to the resin but also to the formula.     

Neonatal hemochromatosis]

Huge sacrococcygeal teratomas in the newborn can cause significant morbidity and even death due to cardiac failure, hemorrhage, or both. Surgical removal is the treatment of choice, but can indicate these events. Ligation of the median sacral artery, which always supplies the tumor, prior to its removal has been advocated, but in the past this procedure required a formal laparotomy. Nowadays, it can be easily accomplished laparoscopically, as this case report demonstrates.