Failure analysis of an ammonia refrigerant condenser tube

A detailed failure analysis was conducted on an ammonia refrigerant condenser tube component that failed catastrophically during its initial hours of operation. Evidence collected clearly demonstrated that the weld between a pipe and a dished end contained a sharp unfused region at its root (lack of penetration). Component failure had started from this weld defect. The hydrogen absorbed during welding facilitated crack initiation from this weld defect during storage of the component after welding. Poor weld toughness at the low operating temperature facilitated crack growth during startup, culminating in catastrophic failure as soon as the crack exceeded critical length.     

Albumin microbubble persistence during myocardial contrast echocardiography is associated with microvascular endothelial glycocalyx damage

BACKGROUND: We hypothesized that the persistence of albumin microbubbles within the myocardium during crystalloid cardioplegia (CP) infusion and ischemia-reperfusion (I-R) occurs because of endothelial injury. METHODS AND RESULTS: The myocardial transit rate of albumin microbubbles was measured in 18 dogs perfused with different CP solutions and in 12 dogs undergoing I-R. Electron microscopy with cationized ferritin labeling of the glycocalyx was performed in 9 additional dogs after CP perfusion and in 3 additional dogs undergoing I-R. Microbubble transit was markedly prolonged during crystalloid CP perfusion. The addition of whole blood to the CP solution accelerated the transit rate in a dose-dependent fashion (P<0.05), which was greater with venous than with arterial blood (P<0.05). The addition of plasma or red blood cells to CP solutions was less effective in improving transit rate than addition of whole blood (P<0.05). Microbubble transit rate was independent of the temperature, K+ content, pH, PO2, osmolality, viscosity, and flow rate of the perfusate. Similarly, a proportion of microbubbles persisted in the myocardium after I-R, which was related to the duration of ischemia (P<0.01) but not of reflow. Crystalloid CP perfusion and I-R resulted in extensive loss of the endothelial glycocalyx without other ultrastructural changes. This effect was partially reversed in the case of crystalloid CP when it was followed by blood CP. CONCLUSIONS: Sonicated albumin microbubbles persist within the myocardium in situations in which the endothelial glycocalyx is damaged. The measurement of the myocardial transit rate of albumin microbubbles may provide an in vivo assessment of endothelial glycocalyx damage.     

Microwave engineering

A brief history of microwave engineering is given. The impact of computer-aided design and monolithic microwave integrated circuits on microwave design is examined. The career potential of microwave engineering is discussed, along with suggestions for related studies that would be useful to the microwave engineer     

Low-power on-chip communication based on transition-aware global signaling (TAGS)

In this paper, we propose a new circuit structure, the transition aware global signaling (TAGS) receiver, that detects transitions at arbitrary switch points. The major performance advantage of this circuit occurs when it switches before the 50% point in the input transition. The TAGS receiver stores the next state of the line while quiet. Upon detection of a transition at the end of the line the output is temporarily driven by the stored next state. Transitions at the output of the receiver are much faster than at the end of the line since they are generated locally. Its ability to detect transitions before a standard inverter and locally generate them at its output, allows its use at the end of long interconnects with fewer repeaters for the same delay as the standard repeater paradigm. The need for fewer repeaters with the TAGS scheme results in lower power consumption for on-chip global communication, while also reducing the placement overhead involved with large buffer blocks. This is shown in the context of bus optimizations, where TAGS achieves up to 50% reduction in power compared to standard repeaters. In an industrial 0.13-/spl mu/m CMOS process, TAGS receivers enable 8-mm-long buses at 1.5-GHz clock rates without repeaters, while the traditional scheme required three repeaters on the line. An extensive analysis of crosstalk noise in the bus environment shows that TAGS can handle the noise levels produced in typical bus structures. Also, the variation of delay in the bus structure under worst-case power supply noise for the TAGS scheme is typically smaller than the delay variation using the standard repeater scheme.     

Neural Network Controller Development and Implementation for Spark Ignition Engines With High EGR Levels

Past research has shown substantial reductions in the oxides of nitrogen (NO_x) concentrations by using 10% -25% exhaust gas recirculation (EGR) in spark ignition (SI) engines (see Dudek and Sain, 1989). However, under high EGR levels, the engine exhibits strong cyclic dispersion in heat release which may lead to instability and unsatisfactory performance preventing commercial engines to operate with high EGR levels. A neural network (NN)-based output feedback controller is developed to reduce cyclic variation in the heat release under high levels of EGR even when the engine dynamics are unknown by using fuel as the control input. A separate control loop was designed for controlling EGR levels. The stability analysis of the closed-loop system is given and the boundedness of the control input is demonstrated by relaxing separation principle, persistency of excitation condition, certainty equivalence principle, and linear in the unknown parameter assumptions. Online training is used for the adaptive NN and no offline training phase is needed. This online learning feature and model-free approach is used to demonstrate the applicability of the controller on a different engine with minimal effort. Simulation results demonstrate that the cyclic dispersion is reduced significantly using the proposed controller when implemented on an engine model that has been validated experimentally. For a single cylinder research engine fitted with a modern four-valve head (Ricardo engine), experimental results at 15% EGR indicate that cyclic dispersion was reduced 33% by the controller, an improvement of fuel efficiency by 2%, and a 90% drop in NO_x from stoichiometric operation without EGR was observed. Moreover, unburned hydrocarbons (uHC) drop by 6% due to NN control as compared to the uncontrolled scenario due to the drop in cyclic dispersion. Similar performance was observed with the controller on a different engine.     

Analytical methods for RE-Co alloys

Total RE, Co and Fe in mischmetal and its cobalt alloys are determined by visual complexometric methods and instrumental x-ray fluorescence techniques. As Fe causes interference in the determinations of RE and Co and its own determination is affected by the presence of Co, it is removed by precipitation. The iron is determined from the precipitate and RE and Co from the filtrate. Accuracy of the method is checked by analysing synthetic mixtures of RE, Co and Fe. The individual REs in mischmetal are determined by x-ray fluorescence method. The analysis technique is based on comparison of the oxides of the test samples with standards (both in pressed pellet form) in the appropriate composition range. The total RE content of mischmetal determined through complexometric analysis is compared with the total RE determined through x-ray fluorescence.     

Inactivation of tumor suppressor p53 by mot-2, a hsp70 family member

The mortalin genes, mot-1 and mot-2, are hsp70 family members that were originally cloned from normal and immortal murine cells, respectively. Their proteins differ by only two amino acid residues but exhibit different subcellular localizations, arise from two distinct genes, and have contrasting biological activities. We report here that the two proteins also differ in their interactions with the tumor suppressor protein p53. The pancytosolic mot-1 protein in normal cells did not show colocalization with p53; in contrast, nonpancytosolic mot-2 and p53 overlapped significantly in immortal cells. Transfection of mot-2 but not mot-1 resulted in the repression of p53-mediated transactivation in p53-responsive reporter assays. Inactivation of p53 by mot-2 was supported by the down-regulation of p53-responsive genes p21(WAF-1) and mdm-2 in mot-2-transfected cells only. Furthermore, NIH 3T3 cells transfected with expression plasmid encoding green fluorescent protein-tagged mot-2 but not mot-1 showed an abrogation of nuclear translocation of wild-type p53. These results demonstrate a novel mechanism of p53 inactivation by mot-2 protein.     

Counselor race and power base: Effects on attitudes and behavior.

Assessed the effects of expert and referent power bases and counselor race on Ss' attitude and behavior change. 32 White undergraduates who identified themselves as having procrastination and career-planning problems were divided into internal or external groups on the basis of their scores on Rotter's Internal–External Locus of Control Scale. Four female interviewers, 2 Black and 2 White, portrayed either an expert or referent role and attempted to influence Ss to use a problem-solving process and perform a career-planning activity. Dependent variables included a measure of attitude change, a measure assessing knowledge of the problem-solving process, and 2 behavioral measures. Results show that (a) the roles were perceived as intended, (b) Ss of expert interviewers recalled more of the problem-solving process, and (c) significant interactions of race and role were obtained such that Black-expert and White-referent interviewers were most influential both in attitude and behavior change. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Epitaxial phase stabilisation phenomena in rare earth manganites

Using injection, powder-flash and band-flash MOCVD techniques, epitaxial thin films of Nd, Ho, Y, Tm, Dy and Lu manganites were prepared. The formation of high-pressure phase NdMn₇O₁₂ as a thin surface layer on Pnma Nd_1−xMnO_3+δ (x0.15) in an Nd-deficient system and HoMnO₃, YMnO₃, TmMnO₃ and LuMnO₃ as perovskite phases (known in the bulk only as high-pressure phases) on a LaAlO₃ substrate were observed. The remarkable reduction in the pressure needed for formation of the phases in epitaxial films in comparison with bulk samples is a manifestation of the epitaxial stabilisation discussed in the paper. The details of the crystal and domain structure of the films as observed by X-ray diffraction (XRD), selected-area electron diffraction (SAED) and high-resolution electron microscopy (HREM) techniques are described.     

Nutritional potential, bioaccessibility of minerals and functionality of watermelon (Citrullus vulgaris) seeds

Watermelon (Citrullus vulgaris) seeds are high in protein and fat, on enriching protein, it can find application as a protein source in various food formulations. Most of the processed foods are generally fortified with micronutrients. The effect of the matrix on the mineral bioavailability is highly important and hence investigated. Defatted flour and protein isolate were prepared from watermelon seed meal and chemical composition and functionality was analyzed by standard techniques. Multiple regression analysis was done to study the compositional influence on the mineral bioaccessibility. Invitro digestibility of the protein was good. The seeds were a moderate source of iron and zinc. The percent bioaccessibility of all the minerals were found to correlate (R = 0.97-0.99) with the concentration of phytate, tannin and oxalate contents. The seed components exhibited good functionality with good macro and micronutrient density and can find application in many food products.