Guided Elastic Interface Waves for Ceramic Joint Evaluation

Because of their excellent thermal and wear properties, structural ceramics are finding increasing use in applications that have traditionally been reserved for metals. Since many ceramics remain stable at temperatures well in excess of the melting points of virtually all of the common structural metals, one such application is in high-temperature engines, where the relatively low weight of ceramics provides an additional advantage over such competitors as refractory metals. Unfortunately, with the relatively low fracture toughness and poor machinability of ceramics, practical designs, at least for the near future, will probably consist of ceramic liners attached to metal substrates, thereby combining the wear and thermal properties of ceramics with the strength of metals.</p

Solid-Solid Bonding Characterization by Ultrasonic Reflectivity

The most common approach to model a weakened bond at a solid-solid interface has been to allow for a partial slip of the displacement at the interface. This concept is transformed into a specific set of boundary conditions which are then solved to obtain the plane-wave reflection and transmission coefficients or to determine the dispersion relation of the associated interface wave, if they exist. A key question in this approach is whether one allows for a partial slip in both displacement components or just the tangential. Initially, Murty [1–2] considered only the tangential slip to model the slip interface with the following boundary conditions: Normal stress is continuous; Shear stress is continuous; Normal displacement is continuous; and Shear stress is proportional to a tangential displacement slip

The effect of high dose antibiotic impregnated cement on rate of surgical site infection after hip hemiarthroplasty for fractured neck of femur : a protocol for a double-blind quasi randomised controlled trial

Background: Mortality following hip hemiarthroplasty is in the range of 10-40% in the first year, with much attributed to post-operative complications. One such complication is surgical site infection (SSI), which at the start of this trial affected 4.68% of patients in the UK having this operation. Compared to SSI rates of elective hip surgery, at less than 1%, this figure is elevated. The aim of this quasi randomised controlled trial (RCT) is to determine if high dose antibiotic impregnated cement can reduce the SSI in patients at 12-months after hemiarthroplasty for intracapsular fractured neck of femur. Methods: 848 patients with an intracapsular fractured neck of femur requiring a hip hemiarthroplasty are been recruited into this two-centre double-blind quasi RCT. Participants were recruited before surgery and quasi randomised to standard care or intervention group. Participants, statistician and outcome assessors were blind to treatment allocation throughout the study. The intervention consisted of high dose antibiotic impregnated cement consisting of 1 gram Clindamycin and 1 gram of Gentamicin. The primary outcome is Health Protection Agency (HPA) defined deep surgical site infection at 12 months. Secondary outcomes include HPA defined superficial surgical site infection at 30 days, 30 and 90-day mortality, length of hospital stay, critical care stay, and complications. Discussion: Large randomised controlled trials assessing the effectiveness of a surgical intervention are uncommon, particularly in the speciality of orthopaedics. The results from this trial will inform evidence-based recommendations for antibiotic impregnated cement in the management of patients with a fractured neck of femur undergoing a hip hemiarthroplasty. If high dose antibiotic impregnated cement is found to be an effective intervention, implementation into clinical practice could improve long-term outcomes for patients undergoing hip hemiarthroplasty

Duplication cyst of pyloroduodenal canal: a rare cause of neonatal gastric outlet obstruction: a case report

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Evaluation of Various Interface Layer Models for Ultrasonic Inspection of Weak Bonds

Adhesively joined structures are increasingly used in industry. Effective nondestructive test techniques are therefore necessary for quality control and in service inspection of bonding conditions. Commonly encountered bonding problems can be classified into three types: debonding, cohesive weakness and adhesive weakness. The former two types can be detected by such traditional ultrasonic techniques as pulse echo, through transmission, C-scan, resonance etc. The last type is the most difficult due to physically ‘perfect ’ contact between adhesive and adherent. Several ultrasonic techniques using longitudinal, shear, plate and interface waves etc. have been considered for finding the most sensitive wave type and corresponding experimental parameters [1–8]. High sensitivity was obtained in several cases. To understand the characteristics of wave reflection and refraction on the bond line for evaluating the bonding quality, various boundary conditions and different physical models have been created [9–18]:</p

Fracture toughness correlation with microstructure and other mechanical properties in near-eutectoid steel

The variation of yield strength and fracture toughness was investigated for four different heat treatments attempted on specimens of a near-eutectoid steel. The aim of this study was to optimize the microstructure for simultaneous improvements in strength and toughness. Further, the fracture toughness deduced through empirical relations from tensile and charpy impact tests was compared with those measured directly according to ASTM Designation: E 399. Among the four different heat treatments attempted in this study, the plane strain condition was valid in the fracture toughness tests for (i) normalized and (ii) hardened and tempered (500 degrees C for 1 h) treatments only. The latter of the two heat treatments resulted in simultaneous improvement of strength and plane strain fracture toughness. The finely-dispersed carbides seem to arrest the crack propagation and also increase the strength, The pearlitic microstructure of the former leads to easy crack propagation along cementite platelets and/or cementite/ferrite interfaces. The nature of variation of empirically determined toughness values from tensile tests for different heat treatments is similar to that measured directly through fracture toughness tests, although the two sets of values do not match quantitatively. On the other hand, the toughness data deduced from charpy impact test is in close agreement with that evaluated directly from fracture toughness tests

Passive immunization with an antibody to the beta-subunit of ovine luteinizing hormone as a method of early abortion--a feasibility study in monkeys (Macaca radiata)

Antiserum to the beta-subunit of ovine luteinizing hormone (oLH-beta) raised in monkeys (Macaca radiata) has been tested by a variety of criteria both in vivo and in vitro to establish its ability to neutralize oLH, hLH, and human chorionic gonadotropin (hCG). Passive administration of this antiserum caused inhibition of ovulation and termination of pregnancy in recipient monkeys as indicated by premature vaginal bleeding and a significant reduction in serum progesterone and estrogen levels. The results suggest that antiserum raised in monkeys against oLH-beta can neutralize monkey LH as well as monkey CG

Warm pool thermodynamics from the Arabian Sea Monsoon Experiment (ARMEX)

Before the onset of the south Asian summer monsoon, sea surface temperature (SST) of the north Indian Ocean warms to 30–32°C. Climatological mean mixed layer depth in spring (March–May) is 10–20 m, and net surface heat flux (Q net ) is 80–100 W m−2 into the ocean. Previous work suggests that observed spring SST warming is small mainly because of (1) penetrative flux of solar radiation through the base of the mixed layer (Q pen ) and (2) advective cooling by upper ocean currents. We estimate the role of these two processes in SST evolution from a two-week Arabian Sea Monsoon Experiment process experiment in April–May 2005 in the southeastern Arabian Sea. The upper ocean is stratified by salinity and temperature, and mixed layer depth is shallow (6 to 12 m). Current speed at 2 m depth is high even under light winds. Currents within the mixed layer are quite distinct from those at 25 m. On subseasonal scales, SST warming is followed by rapid cooling, although the ocean gains heat at the surface: Q net is about 105 W m−2 in the warming phase and 25 W m−2 in the cooling phase; penetrative loss Q pen is 80 W m−2 and 70 W m−2. In the warming phase, SST rises mainly because of heat absorbed within the mixed layer, i.e., Q net minus Q pen ; Q pen reduces the rate of SST warming by a factor of 3. In the second phase, SST cools rapidly because (1) Q pen is larger than Q net and (2) advective cooling is ∼85 W m−2. A calculation using time-averaged heat fluxes and mixed layer depth suggests that diurnal variability of fluxes and upper ocean stratification tends to warm SST on subseasonal timescale. Buoy and satellite data suggest that a typical premonsoon intraseasonal cooling event occurs under clear skies when the ocean is gaining heat through the surface. In this respect, premonsoon SST cooling in the north Indian Ocean is different from that due to the Madden-Julian oscillation or monsoon intraseasonal oscillation

Efficient Algorithms for Incremental Updates of Frequent Sequences

Surface acoustic waves propagating at the interface between two solids are very important for Non Destructive Evaluation of layered media [1]. Dispersion features and transmission losses of such waves strongly depend upon the elastic constants of the solids as well as the mechanical boundary conditions at the interface between the solids. One particular kind of interface waves is the Stoneley wave, which can exist at the interface between certain specifically combined elastic half-spaces in rigid contact [2]. The acoustic field of this wave, travelling with no loss along the interface, decays away from the interface in each medium (Fig. 1a). Murty studied interface waves in another extreme case, i.e. slip contact [3]. For such type of contact, only the normal stress and displacement components are continuous but shear stresses are cancelled at the interface. In the slip contact case, Murty’s study revealed also that the conditions of existence of the Stoneley-like wave are much less rigorous. When material combinations and/or boundary conditions are not satisfied to support the Stoneley-like wave, interface waves may become lossy [3] and radiate acoustic energy through mode conversion into bulk waves (Fig. 1b), like the case of the leaky Rayleigh wave propagating at a solid-liquid interface. Besides, if the presence of a coupling layer between the two half-spaces is taken into account as in most practical conditions, the features of interface waves depends also on the viscoelastic parameters and thickness of the coupling layer[4,5]. Up till now, most of the investigations involving interface waves are indirect ones using ultrasonic reflection and transmission measurements [6], and some others are related to dispersion measurements using interdigital or wedge transducers [4,5]. Few experiments were reported illustrating the field distribution of interface waves. Claus and Palmer observed the Stoneley wave [7] using an optical interferometer. The wave displacements were only detected by the probe beam focused at the Nickel-Pyrex interface