Unfavorable Modes Research Articles

On Eccentric Tube Nosing

Joining two tubes of different diameters has important concerns in many industries and engineering applications. An eccentric reducer is often used in such applications. Therefore, a simple and easy technique for manufacturing an eccentric reducer is of much importance. The simplest technique for producing the eccentric reducers is the tube nosing through eccentric conical dies. In this paper the finite element simulation is used to investigate the eccentric nosing of circular tubes through an eccentric conical die. Simulation is performed to investigate the plastic deformations of the deformed tube and all the possible modes of failure during the eccentric nosing process. Identification of unfavorable modes of failure in the tube nosing process lead to design modification guidelines, design of preform, and the die shape, for the eccentric nosing process. The results obtained confirmed that the modified design of the tube blank not only improves the quality of the nosed-tube product but also reduces nosing load and improves the limiting nosing ratio. Comparison with the experimental results shows that the nosing load and the modes of failure are successfully predicted by the finite element simulation. Also, a preform design for the tube blank that can produce an eccentric reducer with collar end that did not need a trimming process is introduced.

Labour management: An appraisal of the role of false labour and latent phase on the delivery mode

SummaryAchieving normal vaginal delivery requires an orderly transition from early labour to an established active labour. We analysed retrospectively the outcome of labour and the delivery mode based on the diagnosis of labour from the first examination of 3,130 parturients. A total of 1,847 (59.1%) delivered mothers had the first vaginal examination performed by the senior house officer (SHO). The majority (74.4%) of the mothers presented in established labour (cervical dilatation ≥4 cm), 25.6% in early labour, while 11.3% in latent phase. Patients who presented in established labour had a statistically significant higher spontaneous vertex delivery (SVD) rate (Pearson χ2 = 29.74, p = 0.000). A total of 62 parturients (17.5%) who presented in the latent phase and 204 (29.1%) in early labour had an unfavourable delivery mode; 46 had a caesarean section. There was a significant correlation between delivery mode and prolonged latent phase (Pearson correlation coefficient R = −0.066, p = 0.000). Linear regression analysis showed that the total number of VEs was the most significant predictor of the delivery mode of SVD (Regression ß-coefficient = 0.278, t = 10.37, p = 0.000). Early admissions in labour and a prolonged (abnormal) latent phase are significant predictors of difficult mode of delivery (poor labour outcome). We suggest that the first vaginal examination should be undertaken by the most experienced medical personal present at admission.

Vibrational spectroscopy study of the lattice defects in CaZrO 3 ceramics

CaZrO 3 materials were prepared by a solid state reaction. The samples were pre-calcined and sintered at 1673 K for 6 h. They were then analysed using Fourier Transform-Infrared spectroscopy. Microwave dielectric function ( ε= ε′+i ε″) were determined by Kramers–Kronig analysis. The reflectance spectra were then adjusted using the classical dispersion equations taking into account the LO/TO (longitudinal/transverse optic) mode splitting. The most unfavourable mode in terms of dissipation was found to be the first one ( ω T=106.9 cm −1). A simple adjustment of this mode transverse optic damping constant was then carried out to fit the reflectance spectra of slightly non-stoichiometric CaZrO 3 materials. This procedure was conclusive except for excessive Zr non-stoichiometry (extrapolated to >2.78%).

Enhancement of the Performance of Prestressed Concrete Girders Using Strand Anchorage

The main objective of this study is to assess the effect of strand anchorage on the behavior of prestressed concrete girders. Three AASHTO Type II girders with varying end anchorage details were tested. The results from these tests were compared with the results from previous experimental investigations. The test results were also used to verify the tied arch method, aimed at developing a rational prediction tool for determining the effect of anchorage on shear performance. The results from this investigation show that strand anchorage has a beneficial effect on the flexural, shear and ductility behavior of the girders. However, it was concluded that some transverse reinforcement is required to enable the modified system to perform in a consistently ductile manner and to avoid unfavorable failure modes in the end zones. Although the tied arch model gives good correlation with the test results, it should not be used as a design tool.

First principles model of internal transport barriers in negative central shear discharges

At and around minima or maxima of the safety factor q, overlapping, and therefore toroidicity induced coupling of drift eigenmodes centred on neighbouring rational surfaces rl,m defined by q(rl,m) = m/l and rl,m±1 defined by q(rl,m±1) = (m±1)/l, is generally negligible; l and m (m±1) are the toroidal and (main) poloidal mode numbers, respectively. Under these conditions, a careful analysis shows that the growth rate of the ion temperature gradient (ITG) mode is proportional to the absolute value of the magnetic shear parameter; its radial width and frequency (in the E × B rotating frame) are larger in the axisymmetric torus than in the plasma slab or cylinder, especially at small values of kθ ai (kθ is the poloidal mode number and ai the characteristic ion Larmor radius). These results provide a straightforward theoretical interpretation of the origin of internal ion transport barriers (ITBs) in discharges with negative central shear if the ITG instability is indeed the main channel for ion energy transport. In agreement with recent experiments, the mechanism does not degrade for Te∼Ti, an important result for extrapolation to reactors. Once initiated, an ITB will locally increase the curvature of the ion temperature profile and, consequently, the gradients of the radial electric field and E × B rotation profiles (until neoclassical (or sub-neoclassical) transport comes into play). The damping associated with velocity shear yields an upper bound on the unstable mode number range, whereas Landau damping is expected to introduce a lower bound. In cases where toroidal effects are subdominant, the ratio of the damping rate associated with velocity shear to the growth rate associated with magnetic shear leads naturally to the Hamaguchi-Horton parameter (divided by the factor ηi-2/3 which characterizes the departure from the instability threshold (ηi is the ratio of the density and temperature length scales)) when introducing the most unfavourable mode number. Toroidal effects are always dominant for sufficiently weak magnetic shear or sufficiently large values of |LN|/R (where LN is the density gradient length), and therefore before steepening of the profiles has occurred near the zero magnetic shear layer; the counterpart of the Hamaguchi-Horton characteristic parameter appropriate to that case is also obtained, considering again the most unfavourable mode number.

Tert-Butylcyanoketene-substituted styrene cycloadditions. A kinetic study

Rate constants for the cycloaddition of tert-butylcyanoketene (TBCK)1 with various substituted styrenes at different temperatures have been determined by 1H NMR spectroscopy. The addition reaction afforded contra-thermodynamic adducts 3 stereoselectively; a way has been found to convert adducts 3 into thermodynamic cyclobutanones 4. The activation parameters of cycloadditions along with the Hammett reaction constant ρ and the solvent effect on cycloreversion of 3 indicate a concerted asynchronous mechanism involving a transition state with some degree of charge separation. An approximate difference in the energy of activation between the favourable and unfavourable mode of TBCK–p-methoxystyrene addition has been determined to be 10.6 kJ mol–1.

Peel Strength of Composite Layered Joints

Abstract 1. Master curves of R/A/R (rubber/adhesive/rubber) type adhesion tests were generated by laterally shifting the rate curves of peel response with empirically determined shift factors. The universal form of the WLF Equation (3) did not shift the data into continuous master curves, due to the individual contributions of each deforming layer. 2. For the weakly-bonded A/EPM system, rate curves were shifted into good agreement using the universal form of the WLF relation and the Tg of EPM. However, in the case of EPM/A, shift factors calculated by the WLF Equation (3) did not create a smooth master curve. Lateral shifting produced a master curve of EPM/A peel response and resulted in experimentally determined shift factors which fell between the shift factors of the EPM and the adhesive. Apparently, the EPM substrate of low Tg completely dominated the viscoelastic response of the A/EPM joint and even exerted some influence over the debonding process for the EPM/A joint, where the detaching layer was comprised only of adhesive. 3. In the case of strongly bonded chloroprene systems, CR/A/CR data were shifted laterally, but the CR/A and A/CR data shifted well with log aT values calculated from the WLF equation. Adhesive and CR Tg's were within ten degrees, and the rubber layer therefore appeared to contribute little to the overall viscoelastic response of CR/A/CR and CR/A. 4. Detachment of EPM systems was entirely interfacial, except in regions of rate where the adhesive was forced to fail in an unfavorable mode (the low-rate EPM/A experiment and the high-rate A/EPM experiment). A distinct transition of interfacial failure was observed near the glass-transition temperature of the adhesive. As the adhesive failure site changed from substrate to backing, even at the same rate and temperature, a three-fold drop in adhesive fracture energy occurred. 5. CR systems debonded through cohesive rupture of the adhesive layer at low rates. Clean interfacial failure occurred at intermediate to high peel rates. A failure site transition occurred in the same rate and temperature region as the weakly-bonded transition. This failure site change was again associated with a three-fold drop in adhesive-fracture energy. However, the actual peel force difference resulting from this transition in CR/A/CR was on the order of 1000 N/m, while the weakly bonded EPM/A/EPM system experienced a drop of approximately 100 N/m. This disparity in the two transitions suggests that the driving mechanism for the substrate-to-backing failure change is not caused simply by added adhesive bending forces in the low-rate failure mode. 6. Relative contributions of each deforming material to the total peel response for an R/A/R system cannot be determined by examining the shift factor dependence upon temperature. However, R/A and A/R models of the R/A/R detachment modes illustrate the contributions of each layer: as the adhesive debonds from the substrate, both adhesive and rubber contribute to the viscoelastic response of peel, except in the case where both layers exhibit similar Tg's; during adhesive failure from the backing, only the rubber backing contributes to the peel response.

T-lymphocyte recognition of sperm-whale myoglobin. Recognition of synthetic peptides carrying antigenic site 5 by myoglobin-primed T-cells.

Previous studies from this laboratory have resulted in the determination of the antigenic structure of sperm-whale myoglobin (Mb). In the present work, we have investigated the fine specificity requirements for T-cell recognition of one of the Mb antigenic sites (antigenic site 5). The antigenic site (peptide 145-153) and seven progressively longer peptides, increasing in length stepwise by two residues at a time, up to 22 residues in length (peptide 132-153), were synthesized. In addition, four truncated peptides were synthesized with intentional deletions at Tyr-151 and Ala-144. The T-cell recognition of these purified synthetic peptides was examined here in detail in three strains of mice (BALB/cByJ, B10.D2/n and SJL/J). Mb-primed mice afforded T-cells which proliferated to smaller peptides (two or four residues longer than the site; i.e. peptides 145-153 and 143-153) and more so to the longer peptides 135-153 and 132-153 and to Mb. No response was obtained to the truncated peptides, thus underscoring the fine specificity T-cells. No response was obtained also to intermediate-sized peptides. The latter result, due to an unfavourable mode of folding, suggested a conformational dependency in T-lymphocyte recognition.

Dissection of the molecular parameters for T-cell recognition of a myoglobin antigenic site.

Previous studies from this laboratory have resulted in the determination of the antigenic structure of sperm-whale myoglobin (Mb). In the present work, we have investigated the fine specificity requirements for T-cell recognition of one of the Mb antigenic sites (antigenic site 5). The antigenic site (peptide 145-153) and seven progressively longer peptides, increasing in length stepwise by two residues at a time up to 22 residues in length (peptide 132-153), were synthesized. In addition, four truncated peptides were synthesized with intentional deletions at Tyr-151 and Ala-144. The T-cell recognition of these purified synthetic peptides was examined here in detail in three strains of mice (BALB/cByJ, B10.D2/n and SJL/J). Mb-primed mice afforded T-cells which proliferated to smaller peptides (two or four residues longer than the site; i.e. peptides 145-153 and 143-153) and more so to the longer peptides 135-153 and 132-153 and to Mb. No response was obtained to the truncated peptides, thus underscoring the fine specificity of T-cells. No response was obtained also to intermediate-sized peptides. The latter result, due to an unfavorable mode of folding, suggested a conformational dependency in T-lymphocyte recognition and was confirmed by additional studies employing peptide priming. Thus priming with either the 11- or 22-residue peptides afforded T-cells which proliferated to both of these two peptides, but not to intermediate-sized peptides. More importantly, peptide-primed cells did not proliferate on challenge in vitro with Mb. This indicated that the in vivo recognition (priming) was to the unfolded peptide and these cells will not therefore recognize native Mb in vitro. Tolerization of neonatal mice with native Mb, which was total for the native protein at the T-cell level, had no effect on in vivo recognition (priming) and in vitro proliferation due to the unfolded peptide. Conversely, tolerization by any unfolded peptide had little or no effect on in vivo recognition of, and proliferation to, native Mb. It was concluded that T-cell recognition of native proteins (or at least of Mb) is dependent on protein conformation. A peptide may not cause proliferation of native protein-primed T-cells even though it contains an antigenic site. Finally, macrophage presentation of protein antigens is not related to processing via fragmentation of antigen by macrophage.

Oxidation of N-methyl substituted hypoxanthines, xanthines, purine-6,8-diones and the corresponding 6-thioxo derivatives by bovine milk xanthine oxidase

1. 1. The oxidation of six series of purines (hypoxanthines, xanthines, purine-6,8-diones and the corresponding 6-thioxo derivatives) by a highly purified bovine milk xanthine oxidase (EC 1.2.3.2) has been studied, using a variety of N-methyl derivatives. 2. 2. N-Methyl substituents can either enhance or reduce enzymic rates. Enhancement is ascribed to blockade of groups which mediate unfavorable modes of binding of substrate to enzyme. Introduction of N-methyl groups can also inhibit enzymic oxidation, either by occluding essential binding groups or by preventing spontaneous or enzyme-induced tautomerisation processes, which create suitable binding sites in the substrates. 3. 3. In all purines which are rapidly attacked by xanthine oxidase, proper attachment to the active center is mediated by the groupings (3)NH, (9)N or (3)N, (9)NH. 4. 4. Reduced rates usually express lowered substrate affinity, which finds its expression in weak competitive inhibition of xanthine oxidation.