Prior Beta Research Articles

Statins and Response to Carvedilol Given to Patients with Chronic Heart Failure

Aim: to evaluate response to carvedilol given to heart failure patients on chronic treatment with statins. Patients and Methods: 80 males, mean age 55 years (SD = 8.19), with symptomatic heart failure, EF<40%, NYHA class II and III, without prior beta blocker therapy but receiving ACEI and diuretics. Group I – 50 patients on statins (atorvastatin 18.5 = 12.4 mg/daily); group II – 50 patients without statin therapy. Analysis at baseline and at 3 months: NYHA functional class, HRs, echocardiographic parameters ((LVEF, LVDs, LVDd, E/A), exercise capacity using cardiopulmonary exercise testing techniques CPX (t max, METS, VO2peak), heart rate variability by 24h ECG monitoring and plasma levels of BNP, CRP, IL-6 and TNF-alpha.

Failure analysis of titanium alloy (Ti6Al4V) fastener used in aerospace application

Titanium alloy fasteners are being used in space programme. These fasteners are coated with MoS 2, which serves the purpose of solid lubricant. During the trial assembly of flight spin motor to the bracket mounted on subsystem, one of the two fasteners failed such that the head of the bolt had sheared off the shank. Metallographic analysis carried out on the failed fasteners revealed variations in the microstructures all along the shank axis. Microstructure consisted of equiaxed primary alpha in transformed beta matrix within lower portion of the shank, while it was elongated primary alpha with little bulging all along prior beta grain boundaries as well as acicular alpha at some other location towards the head side, features, typical of, as if worked above beta transus temperatures. This paper highlights the details of investigations carried out on the failed fasteners.

Significance of initial blood pressure and comorbidity for the efficacy of a fixed combination of an angiotensin receptor blocker and hydrochlorothiazide in clinical practice

Two-thirds of all patients with arterial hypertension need drug combinations to achieve blood pressure (BP) goals. Fixed combinations have high efficacy and result in high patient compliance. 300 mg irbesartan plus 25 mg hydrochlorothiazide (HCTZ) has been investigated only in clinical trials but not in daily practice. A multicenter, noninterventional, noncontrolled observational study with 8123 patients seen by 1604 physicians in daily practice. BP reduction (office measurements), co-morbid disease and tolerability were documented over a 6-month observational period. At mean baseline BP of 161 +/- 15/94 +/- 10 mmHg, administering of fixed combination resulted in a substantial BP reduction averaging 28 +/- 15/14 +/- 10 mmHg (P < 0.001). Decrease of systolic BP ran parallel with increasing systolic baseline BP (Spearman's Rho -0.731; P < 0.0001; diastolic BP vs diastolic baseline BP Rho 0.740; P < 0.0001), independent from patient characteristics (age, obesity, diabetes or nephropathy) but enhanced with short history of hypertension (P < 0.0001 vs long history), prior beta blockers (P = 0.001 vs prior angiotensin receptor blockers [ARBs]), prior calcium channel blockers (P = 0.046 vs prior ARBs) and no prior medication (P = 0.012 vs prior ARBs). High compliance (>98%) and low incidence of adverse events (0.66%) were documented. The fixed combination of 300 mg irbesartan with 25 mg HCTZ was efficacious and tolerable in an unselected patient population in primary care.

The origins of microtexture in duplex Ti alloys

A previously developed methodology was used to transform electron backscatter diffraction (EBSD) data for the primary and secondary alpha phases of Ti–6Al–2Sn–4Zr–6Mo (Ti-6246) to the prior beta phase. The results established that the observed microtexture in duplex alloys is a direct result of the prior beta grain orientations, and variant selection. In addition, for a homogeneous duplex microstructure, all of the secondary alpha phase and the majority of the primary alpha grains retain crystallographic coherency, according to the Burgers relationship, with the surrounding beta phase matrix, which comprise prior beta grains. This investigation establishes that this technique to recover the prior beta grain orientations is applicable to duplex α/β titanium microstructures. The crystallographic coherency of the primary and secondary alpha phase with the prior beta grain coupled with variant selection then leads to the localized microtexture observed in a wide variety of Ti alloys.

Effect of initial microstructure on plastic flow behaviour during isothermal forging of Ti–10V–2Fe–3Al

The plastic flow behaviour and microstructural development during isothermal forging was determined for near beta alloy Ti–10V–2Fe–3Al. Two different initial microstructures were employed: (i) a beta forged billet with a large prior beta grain size with Widmanstätten alpha platelets; and (ii) an alpha–beta forged billet with prior globular primary alpha. The beta forged condition exhibited a peak stress followed by intense flow softening, which is attributed to the break up of the Widmanstätten alpha platelets. Evidence suggests that peak hardening at low strains is due to dislocation pile-ups at alpha platelet/subgrain beta interfaces and subsequent flow softening is attributed to the transmission of beta phase through the alpha platelets. A strain rate ‘jump’ test investigation provided sufficient evidence to suggest that there is a transition from dislocation dominant deformation mechanisms at high strains rates to diffusional dominant deformation at low strain rates in Ti–10V–2Fe–3Al during forging.

Bayesian Analysis in the L 1-Norm of the Mixing Proportion Using Discriminant Analysis

We consider the mixing proportion π in a mixture of two independent distributions, and establish the expression of its posterior density, in closed form and in terms of L 1-norms of various related functions, using a prior beta and the optimal classification rule for the two populations provided by Discriminant analysis. A numerical example fully illustrates the concepts presented.

Cavitation during hot-torsion testing of Ti-6Al-4V

Hot-torsion testing was used to establish the cavitation behavior of a typical alpha/beta titanium alloy, Ti-6Al-4V, with a colony microstructure, during simple-shear deformation. For this purpose, sections of deformed specimens were examined by optical metallography, and by scanning and orientation-imaging microscopy (OIM). It was found that cavity nucleation occurred along prior beta boundaries as well as at triple points; in particular, most cavities nucleated along boundaries perpendicular to the axial direction of the specimen. Extensive growth was observed for cavities surrounded by both hard and soft orientations, with the soft colonies accommodating more of the imposed strain. At high degrees of deformation, dynamic globularization of the colony microstructure adjacent to the cavities was also observed. In addition, the metallographic observations revealed that the cavities did not grow in an equiaxed mode, but in an elliptical manner. A tensor describing the cavity-growth rate along the axial, radial, and hoop specimen directions was determined using measurements of individual cavity sizes. The cavity-growth behavior in torsion was compared to previous observations from hot-tension tests. This comparison indicated that the rate of cavity growth in shear was approximately one-tenth that in uniaxial tension. This finding is in broad agreement with models predicting the variation of the cavity-growth rate as a function of the ratio of the mean stress to the hydrostatic stress.

Failure analysis of a Ti–6Al–4V gas bottle

Ti–6Al–4V alloy has proven its suitability as a major structural material for upper stages of launch vehicles owing to excellent specific strength coupled with excellent fabrication characteristics. High pressure gas bottles being fabricated using this alloy are in use for storing gaseous helium for the pressurization of liquid propellant in the satellite launch vehicles. One such bottle with Ti–6Al–4V liner, fabricated by electron beam welding of two forged and machined hemispheres (designated as male and female domes) and wound with Kevlar fibre around it, failed prematurely during the auto-frettage cycle of pressure testing. Detailed metallurgical analyses were carried out on this cracked liner. Microstructure of the male dome consisted of colonies of alpha phase and coarse laths of alpha phase along the prior beta grain boundaries whereas that of the female dome contained equiaxed grains of primary alpha in the matrix of transformed beta. Microstructure of the electron beam (EB) weldment region showed martensitic structure. The difference in microstructures between the two domes is attributed to higher forging temperature for male dome, which caused male dome to yield at a smaller strain. Cracks initiated at the location where there was a change in the wall thickness of the dome and propagated along the alpha phase present on the prior beta grain boundaries and also along the alpha lath boundaries. This paper highlights the investigations carried out on this cracked liner and remedial measures suggested to avoid future recurrence.

P530 The effects of prior beta blocker therapy on creatine kinase rise after percutaneous coronary intervations

P530 The effects of prior beta blocker therapy on creatine kinase rise after percutaneous coronary intervations

The salutary effect of prior beta blocker therapy on clinical outcomes following primary angioplasty for acute myocardial infarction: a pooled analysis from the Primary Angioplasty in Myocardial Infarction (PAMI:1), PAMI:2, and stent:PAMI trials

The salutary effect of prior beta blocker therapy on clinical outcomes following primary angioplasty for acute myocardial infarction: a pooled analysis from the Primary Angioplasty in Myocardial Infarction (PAMI:1), PAMI:2, and stent:PAMI trials

Microstructure and creep deformation of a near beta titanium alloy ‘β-CEZ’

Abstract The relationship between titanium alloy processing, structure and properties received great attention in recent years. The aim of this paper is to determine the influence of the microstructure of a titanium alloy on its creep properties at intermediate temperature. A pronounced influence of the microstructure, quantified by image analysis, on the steady-state creep rate was found. Structures exhibiting large values of length, width, surface and/or perimeter of the primary intragranular alpha phase ( α p ) and thus low values for the total interfacial area between the α p and β matrix, show low creep strength at 400°C. In addition, the influence of various parameters such as the texture of the alpha phase, the size and the morphology of the α phase (at prior beta grain boundaries and secondary alpha phase) and the prior beta grain size were investigated. The effects of temperature and stress level on the creep response of the alloy were investigated in the temperature range of 400 to 470°C. The stress dependence of the steady-state creep rate indicates that an increase in temperature introduces a gradual decrease in the stress exponent n and a change of creep mechanism at 400 to 450°C, depending on the stress level. The apparent activation energy of creep was determined for different stress levels. Transmission electron microscopy observations of deformed dislocation structures developed during creep are used to interpret creep properties, and deformation mechanisms are proposed for the primary and secondary intragranular alpha phases.

浮遊溶解‐減圧吸引鋳造した各種チタン合金鋳造材の機械的性質

Properties of precision castings of Ti alloys were investigated in order to evaluate a newly developed casting process. This process is constituted of combination of levitation melting and counter-gravity low-pressure casting, named "LEVICAST". Cast specimens of commercial pure titanium (CP-Ti), Ti-6Al-4V and Ti-6Al-7Nb were prepared by LEVICAST process, and their mechanical properties and surface contamination were examined as compared with rolled and annealed bar. Sound surfaces of castings were obtained through LEVICAST process. Hard alpha case caused by oxygen contamination at surface of the cast specimens were very thin. Increases of carbon and nitrogen from melting atmosphere were negligible. Tensile properties of CP-Ti and Ti-6Al-4V in as-cast condition satisfied the specification of ASTM B367 C-2 and C-5 for ordinary cast use. HIP treatment improved ductility of the casts at the sacrifice of strength. Strength and ductility of HIP'ed Ti-6Al-7Nb casts were slightly lower than those of HIP'ed Ti-6Al-4V casts. Mechanical properties of the HIP'ed casts of both alloys satisfied the specification of ASTM F1108 of Ti-6Al-4V casts for surgical and implant use. Mechanical properties of the cast alloys were almost same as those of rolled and beta-annealed specimen which had coarse microstructures similar to cast one. This demonstrates that mechanical properties of the these alloys are essentially determined by microstructures such as prior beta grain size and lamellar spacing of alpha phases independent of production processes. It was confirmed that LEVICAST was a suitable precision casting process for Ti alloy casts which were free from contamination.

Ultrasonic backscattering in duplex microstructures: Theory and application to titanium alloys

A theory is presented for the ultrasonic backscattering in duplex microstructures. Assuming single scattering described by the Born approximation, we consider a microstructure consisting of macrograins containing colonies with crystallographically related orientations. General results are presented for the backscattering coefficient, assuming that all variants occur with equal probability. These are then applied to the particular case of titanium alloys, in which the macrograins are taken to be prior beta grains and the colonies are assumed to be alpha phase produced by a martensitic transformation. Numerical results illustrate the effects of ultrasonic frequency, colony size and ellipticity, and macrograin size and ellipticity on the backscattering.

Myocardial functional preservation during ischemia: influence of beta blocking agents.

To determine whether prior acute Beta blockade protects the heart against the deleterious effects of normothermic low flow global ischemia on myocardial function, aortic pressure, developed pressure, dP/dtmax and end diastolic pressure were monitored in isolated perfused rabbit hearts prior to, during and following 30 and 60 min ischemia, during which either Krebs-Henseleit (control) or Beta blocking agents. Bevantolol (cardioselective) or Propranolol (non-selective) were perfused through the heart. Control hearts made ischemic for 30 min and then reperfused had significantly elevated end diastolic (p < .01) and aortic pressures (p < .01) and reduced developed pressure relative to baseline (p < .05). Hearts treated with Bevantolol or Propranolol (3 x 10(-5) m/l) 5 min prior to and during 30 min ischemia recovered preischemic developed pressure and dP/dtmax (p > 0.05), while end diastolic pressure was elevated (p < .01, p < .05 respectively). Aortic pressure was unchanged relative to baseline (p > .05). Comparison of indices from hearts under Beta blockade with controls showed that following 30 min ischemia and recovery, the Bevantolol treated group had reduced aortic pressure (p < .01) and end diastolic pressure (p < .05) and increased percent developed pressure and percent dP/dtmax (p < .001) relative to control. In the propranolol treated group, end diastolic pressure was reduced and percent developed pressure (p < .01) and percent dP/dtmax (p < .001) were increased relative to unblocked hearts. Following 60 min ischemia and 30 min reperfusion, reduction in all functional indices occurred, however dP/dtmax was unchanged from baseline in the Propranolol and Bevantolol treated groups. Comparison between groups showed that the Bevantolol treated group had significantly better dP/dtmax and developed pressure (p < .05), whereas the Propranolol group shows no significant difference from baseline (p > .05) (K-H). We conclude that following short periods of ischemia, Beta blockade protects the heart from deleterious function effects of ischemia but that the protective effect is diminished in Bevantolol relative to Propranolol treatments following prolonged ischemia. The data indicates that the beneficial effects of Beta blockade in reducing ischemic induced damage occurs early during conditions of ischemia such as would be present in the setting of acute myocardial infarction.

The search for information — A patient perspective on multiple opinions

This paper describes the first dynamic formulation of the optimal strategy, from a patient perspective, for the search for additional information in the form of multiple opinions. The Mehrez and Gafni framework for choosing an optimal treatment from a patient perspective is employed to study the optimal search strategy for a representative individual who is an expected utility maximizer. Two different processes for gathering information regarding the probability of treatment success ( P) are studied: In the first, physicians provide information in a yes or no (treatment) type of recommendation; in the second, physicians provide probabilistic information about the likelihood of success in the treatment. For the first system the optimal strategy is derived using an algorithm of an order O( n) ( n is the number of opinions to be purchased from expert doctors) for a prior beta probability density function of P and a Bernoulli process of information gathering. EVSI (expected value of sample information) measures are incorporated into the Bayesian analysis to study this case and to obtain an upper bound on n ∗ (the optimal number of opinions to be purchased). The approach developed here is different than the well known one provided by Raiffa and Schlaifer in 1961 and it enables us to present additional results regarding the optimal search strategy and how to identify it. For example, if (i) the process of information gathering is generated by a Bernoulli process, (ii) the natural conjurate prior distribution is beta, and (iii) the utility functions are linear functions of the probability of treatment success, then for each n, there exists at most one value of x (the number of experts recommending treatment) for which a search should continue. At this value the incremental increase of the individual's lifetime expected utility stemming from the decision to seek additional expert's opinion is positive. This observation might explain a reality where the likelihood of seeking a large number of opinions is very low. Furthermore, sufficient conditions for not initiating the information search process and on the range of n ∗ are provided. In addition an analysis of the second process is provided and properties of the optimal strategy are studied. It is shown that the formulations of the two processes are equivalent and that they can be further analyzed through the two action space project selection problem studied by Mehrez and Stulman and others. A numerical comparison and a sensitivity analysis between the two processes for gathering information is presented. It is illustrated that for similar cost figures, the probability estimation procedure provides more information than the yes-no type recommendation to the patient.

INFLUENCE OF CREEP‐FATIGUE INTERACTION ON HIGH TEMPERATURE FATIGUE CRACK GROWTH BEHAVIOR of Ti‐1100

Abstract— A series of crack growth experiments has been preformed on the near alpha titanium alloy, Ti‐1100, to determine the mechanism of the creep‐fatigue interaction. Based on pure creep crack growth results, the increase in the creep‐fatigue crack growth rate is not amenable to separate contributions of creep crack growth and fatigue crack growth.A mechanism has been proposed to account for the increase in creep‐fatigue crack growth rate that is based on the planar slip of titanium alloys which results in the formation of dislocation pileups at the prior beta grain boundaries and leads to intergranular fracture. This mechanism has been validated through crack growth experiments preformed on a Ti‐1100 that has been microstructurally modified through the precipitation of internal slip barriers. These show that the intergranular fracture and increase in crack growth rate are absent.

Dwell-sensitive fatigue under biaxial loads in the near-alpha titanium alloy IMI685

Low-temperature dwell sensitivity is an industrially relevant problem in the near-alpha titanium alloys. It is well documented that components in these materials can display life reductions of over an order of magnitude when the fatigue cycle contains a dwell period at peak stress. Despite much work, the mechanisms responsible for the phenomenon are not understood in full, although a poorly aligned alpha microstructure in thick sections, plastic strain accumulation, hydrogen level and stress biaxiality have all been invoked. The research programme has addressed the problem by focusing on IMI685 as a typical representative of this class of material. To probe the mechanisms involved, tension and torsion loading modes were employed and hydrogen concentration was varied in the range 20–60 ppm. Quasi-cleavage facet formation is an essential element of the failure process and a model for its occurrence on basal planes approximately perpendicular to the principal tensile stress direction in both tension and torsion specimens is introduced. On the basis of this model, the life decrement in large components can be related to variations in prior beta grain size. Hydrogen content is shown to have an effect on deformation response but not a significant influence on the failure process.

Value of the beta prior information

Information gain or loss is studied here by considering changes in the reciprocal of the expected posterior variance. For two beta distributions, the ratio of the expected values of their posterior variances provides a convenient criterion which is consistent with several results of the bayesian set-up and also permits the determination of the least informative prior beta distribution. Relations with results obtained by other authors are also discussed.

Noise and resolution of Bayesian reconstruction for multiple image configurations

Images reconstructed by Bayesian and maximum-likelihood (ML) using a Gibbs prior with prior beta were compared with images produced by filtered backprojection (FBP) from sinogram data simulated with different counts and image configurations. Bayesian images were generated by the OSL algorithm accelerated by an overrelaxation parameter. For relatively low beta , Bayesian images can yield an overall improvement to the images compared to ML reconstruction. However, for larger beta , Bayesian images degrade from the standpoint of noise and quantitation. Compared to FBP, the ML images were superior in a mean-square error sense in regions of low activity level and for small structures. At a comparable noise level to FBP, Bayesian reconstruction can be used to effectively recover higher resolution images. The overall performance is dependent on the image structure and the weight of the Bayesian prior.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

β1‐ and β2‐adrenoceptor‐mediated relaxation in human internal mammary artery and saphenous vein: unchanged β‐ and α‐adrenoceptor responsiveness after chronic β1‐adrenoceptor blockade

1. We have recently reported that patients taking beta 1-adrenoceptor-selective antagonists exhibit marked sensitization of beta 2-adrenoceptor responses but unaltered beta 1-adrenoceptor responses in the heart, both in vitro and in vivo. We therefore investigated beta 1- and beta 2-adrenoceptor-mediated relaxant responses in rings of human internal mammary artery and saphenous vein without endothelium, taken from beta 1-blocked and non-beta-blocked patients undergoing coronary artery bypass graft surgery, for comparison. We also examined alpha 1-adrenoceptor-mediated contraction in these vessels, to determine whether beta 1-blockade had any cross-regulatory effect. 2. Following alpha-blockade with 10 microM phenoxybenzamine, both noradrenaline adrenaline produced concentration-dependent relaxations in both blood vessels, their effects being mediated predominantly through beta 2-adrenoceptors; a lesser beta 1-adrenoceptor component to relaxation was also found in internal mammary artery and a minor beta 1-adrenoceptor component was present in saphenous vein. No differences were found in beta 1- or in beta 2-adrenoceptor-mediated vasorelaxation between beta 1-blocked and non-beta-blocked patients. 3. Methoxamine produced concentration-dependent contractions in both blood vessels, and the potency and efficacy were not significantly different between vessels from beta 1-blocked and from non-beta-blocked patients. 4. These findings indicate that, in these tissues, which possess a relatively minor beta 1-adrenoceptor component in contrast to myocardial tissue, chronic beta 1-blocker treatment does not alter either beta 1- or beta 2-adrenoceptor responses. Likewise, in such tissues, alpha 1-adrenoceptor responses are unaffected by prior beta 1-blockade.