Effects of Welding Parameters on Toughness and Hardness in 690 Weld Zone MPa Steel

ABSTRACT. Specifications for the welding of high-strength steels are generally intended to control hydrogen cracking and provide adequate weld zone toughness for resistance to fatigue cracking and shock loading. The specifications should also allow welding to be undertaken safely and profitably. The work described here was designed to identify the optimum match of welding parameters, notably preheat, interpass temperature and heat input, for the welding of a 690 MPa (100 ksi) microalloy quench and tempered steel. The paper covers investigations into two aspects of weldability: toughness and hardness. The first part involved shielded metal arc (SMA) butt joint welding of carefully designed plates at a range of preheat and interpass temperatures and heat input values, to identify welding procedures that give maximum HAZ and weld metal toughness. The second is a laboratory study of bead-on-plate submerged arc welds to clearly identify the relationship between hardness and welding parameters. The test procedure for the first investigation involved SMA welding at preheat and interpass (P and I) temperatures from -20°C to 220°C (-4 ° to 428°F) using heat input values of (approximately) 1.3, 2.9 and 4 kJ/mm (33, 74 and 102 KJ/in.) Charpy V-notch energy and fracture appearance transition curves were then generated with the Charpy notches being carefully located to give the lowest toughness values. Results showed that the minimum preheat and interpass temperature for control of weld metal hydrogen cracking was 60°C (140°F) and that low values of toughness in both weld and heat-affected zone consistently occurred in the weld root region. Low preheat techniques and one-sided welding should therefore be avoided for critical applications. For weld metal, greatest toughness occurred at high preheat and interpass temperatures (160°C; 320°F) combined with low welding heat input (1.2 kJ/mm; 30 KJ/in). For high heat input welding, preheat and interpass temperature had little influence on toughness over the range of temperatures examined. For heat-affected zone regions, levels of toughness obtained when using the high preheat/low heat input and low preheat/high heat input techniques were similar. It was found, however, that careful control of preheat and interpass temperature was essential, for each heat input value, because toughness can drop off rapidly on either side of the optimum interpass temperature. For some applications, optimum preheat and interpass temperatures were found to lie between 60 ° and 90°C (140 ° and 194°F). In the second study, a series of beadon-plate submerged arc welds was deposited using a wide range of preheat and KEY WORDS Welding Parameters SMAW Toughness Hardness 690 MPa Steel Preheat Temperature Interpass Temperature Heat Input Butt Joint Welding Bead-on-Plate interpass temperatures, voltages, currents and travel speeds. In each case, the welding parameters were chosen so that the welding power input (V x I) could be held constant while varying heat input, or vice versa. For each weld, hardness readings were taken in both the weld deposit and HAZ at approximately 1 mm (0.04 in.) from the weld interface. It was found that: 1) HAZ hardness readings (390~130 HV 30 for heat input values up to 2 kJ/mm) were consistently higher than weld metal hardness readings. 2) Heat input has a marginal effect on HAZ hardness up to about 2 kJ/mm (51 kJ/in.), however, above 2 kJ/mm the hardness drops off at a rate of approximately HV 30 for each increase of 1 kJ/mm (25 kJ/i n.). 3) Weld metal hardness dropped continuously over the range of 0.5 to 4.5 kJ/mm (13 to 114 kJ/in.). 4) Both HAZ and weld metal hardness drops approximately 1 HV 30 for every 4°C (7.2°F) increase in preheat and interpass temperature. The results of this work have been used to develop an optimized weld design for butt joint welding of 35-50 mm (1.4-2 in.) plate. This uses high heat input for all but the weld capping passes, where high interpass temperatures and low heat input techniques are employed

Grip control and motor coordination with implanted and surface electrodes while grasping with an osseointegrated prosthetic hand

Background: Replacement of a lost limb by an artificial substitute is not yet ideal. Resolution and coordination of motor control approximating that of a biological limb could dramatically improve the functionality of prosthetic devices, and thus reduce the gap towards a suitable limb replacement. Methods: In this study, we investigated the control resolution and coordination exhibited by subjects with transhumeral amputation who were implanted with epimysial electrodes and an osseointegrated interface that provides bidirectional communication in addition to skeletal attachment (e-OPRA Implant System). We assessed control resolution and coordination in the context of routine and delicate grasping using the Pick and Lift and the Virtual Eggs Tests. Performance when utilizing implanted electrodes was compared with the standard-of-care technology for myoelectric prostheses, namely surface electrodes. Results: Results showed that implanted electrodes provide superior controllability over the prosthetic terminal device compared to conventional surface electrodes. Significant improvements were found in the control of the grip force and its reliability during object transfer. However, these improvements failed to increase motor coordination, and surprisingly decreased the temporal correlation between grip and load forces observed with surface electrodes. We found that despite being more functional and reliable, prosthetic control via implanted electrodes still depended highly on visual feedback. Conclusions: Our findings indicate that incidental sensory feedback (visual, auditory, and osseoperceptive in this case) is insufficient for restoring natural grasp behavior in amputees, and support the idea that supplemental tactile sensory feedback is needed to learn and maintain the motor tasks internal model, which could ultimately restore natural grasp behavior in subjects using prosthetic hands

Universal Rights and Wrongs

This paper argues for the important role of customers as a source of competitive advantage and firm growth, an issue which has been largely neglected in the resource-based view of the firm. It conceptualizes Penrose’s (1959) notion of an ‘inside track’ and illustrates how in-depth knowledge about established customers combines with joint problem-solving activities and the rapid assimilation of new and previously unexploited skills and resources. It is suggested that the inside track represents a distinct and perhaps underestimated way of generating rents and securing long-term growth. This also implies that the sources of sustainable competitive advantage in important respects can be sought in idiosyncratic interfirm relationships rather than within the firm itself

Apoptosis-Like Death in Bacteria Induced by HAMLET, a Human Milk Lipid-Protein Complex

Background: Apoptosis is the primary means for eliminating unwanted cells in multicellular organisms in order to preserve tissue homeostasis and function. It is characterized by distinct changes in the morphology of the dying cell that are orchestrated by a series of discrete biochemical events. Although there is evidence of primitive forms of programmed cell death also in prokaryotes, no information is available to suggest that prokaryotic death displays mechanistic similarities to the highly regulated programmed death of eukaryotic cells. In this study we compared the characteristics of tumor and bacterial cell death induced by HAMLET, a human milk complex of alpha-lactalbumin and oleic acid. Methodology/Principal Findings: We show that HAMLET-treated bacteria undergo cell death with mechanistic and morphologic similarities to apoptotic death of tumor cells. In Jurkat cells and Streptococcus pneumoniae death was accompanied by apoptosis-like morphology such as cell shrinkage, DNA condensation, and DNA degradation into high molecular weight fragments of similar sizes, detected by field inverse gel electrophoresis. HAMLET was internalized into tumor cells and associated with mitochondria, causing a rapid depolarization of the mitochondrial membrane and bound to and induced depolarization of the pneumococcal membrane with similar kinetic and magnitude as in mitochondria. Membrane depolarization in both systems required calcium transport, and both tumor cells and bacteria were found to require serine protease activity (but not caspase activity) to execute cell death. Conclusions/Significance: Our results suggest that many of the morphological changes and biochemical responses associated with apoptosis are present in prokaryotes. Identifying the mechanisms of bacterial cell death has the potential to reveal novel targets for future antimicrobial therapy and to further our understanding of core activation mechanisms of cell death in eukaryote cells

Activated Ion Electron Capture Dissociation (AI ECD) of proteins: synchronization of infrared and electron irradiation with ion magnetron motion.

Here, we show that to perform activated ion electron capture dissociation (AI-ECD) in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer equipped with a CO(2) laser, it is necessary to synchronize both infrared irradiation and electron capture dissociation with ion magnetron motion. This requirement is essential for instruments in which the infrared laser is angled off-axis, such as the Thermo Finnigan LTQ FT. Generally, the electron irradiation time required for proteins is much shorter (ms) than that required for peptides (tens of ms), and the modulation of ECD, AI ECD, and infrared multiphoton dissociation (IRMPD) with ion magnetron motion is more pronounced. We have optimized AI ECD for ubiquitin, cytochrome c, and myoglobin; however the results can be extended to other proteins. We demonstrate that pre-ECD and post-ECD activation are physically different and display different kinetics. We also demonstrate how, by use of appropriate AI ECD time sequences and normalization, the kinetics of protein gas-phase refolding can be deconvoluted from the diffusion of the ion cloud and measured on the time scale longer than the period of ion magnetron motion

Regional Adoption of Business-to-Business Electronic Commerce in China: Role of E-Readiness

Adoption of B2B e-commerce is a powerful driver of economic success in developed and developing countries. However, adoption rates in developing countries lag far behind. This paper draws on the Perceived eReadiness Model and research on the influence of inter-organizational relationships and economic-cultural contexts to explain the importance of three factors—inter-organizational power dependence, cooperativeness, and regional economic-cultural differences—for achieving higher levels of Internet-based Electronic Data Interchange (EDI) in the developing country of China. We employ survey data to empirically test both the individual and joint influence of these factors. The findings suggest that beyond intra-organizational and external factors, managers and policy makers wanting to promote Internet-based EDI adoption in developing countries must also account for the inter-organizational relationships of firms and the economic and cultural circumstances of the regions in which they operate

Conformational effects on the Circular Dichroism of Human Carbonic Anhydrase II: a multilevel computational study

Circular Dichroism (CD) spectroscopy is a powerful method for investigating conformational changes in proteins and therefore has numerous applications in structural and molecular biology. Here a computational investigation of the CD spectrum of the Human Carbonic Anhydrase II (HCAII), with main focus on the near-UV CD spectra of the wild-type enzyme and it seven tryptophan mutant forms, is presented and compared to experimental studies. Multilevel computational methods (Molecular Dynamics, Semiempirical Quantum Mechanics, Time-Dependent Density Functional Theory) were applied in order to gain insight into the mechanisms of interaction between the aromatic chromophores within the protein environment and understand how the conformational flexibility of the protein influences these mechanisms. The analysis suggests that combining CD semi empirical calculations, crystal structures and molecular dynamics (MD) could help in achieving a better agreement between the computed and experimental protein spectra and provide some unique insight into the dynamic nature of the mechanisms of chromophore interactions

Electron Capture Dissociation Mass Spectrometry of Tyrosine Nitrated Peptides

In vivo protein nitration is associated with many disease conditions that involve oxidative stress and inflammatory response. The modification involves addition of a nitro group at the position ortho to the phenol group of tyrosine to give 3-nitrotyrosine. To understand the mechanisms and consequences of protein nitration, it is necessary to develop methods for identification of nitrotyrosine-containing proteins and localization of the sites of modification.Here, we have investigated the electron capture dissociation (ECD) and collision-induced association (CID) behavior of 3-nitrotyrosine-containing peptides. The presence of nitration did not affect the CID behavior of the peptides. For the doubly-charged peptides, addition of nitration severely inhibited the production of ECD sequence fragments. However, ECD of the triply-charged nitrated peptides resulted in some singly-charged sequence fragments. ECD of the nitrated peptides is characterized by multiple losses of small neutral species including hydroxyl radicals, water and ammonia. The origin of the neutral losses has been investigated by use of activated ion (AI) ECD. Loss of ammonia appears to be the result of non-covalent interactions between the nitro group and protonated lysine side-chains

Districts, multinationals and global/digital networks

This paper reflects on what remains of Becattini’s utopia in the new context of a globalized and digital economy. Can one still foresee a global world populated with local societies able to produce value by following their own inspirations and chorally participating in a world-wide division of cognitive labor? It is suggested that the interpretive value of Becattini’s theorizing remains, to the extent that one moves away from the consideration of the classical district model, and adopts his more general way of thinking about the economy, which is only exemplified by the historical circumstance of industrial districts. His view may well apply to a variety of circumstances, not only to industrial districts and it is flexible enough to encompass economic change under different environmental conditions

Risk factors for Group B Streptococcus colonisation and disease in Gambian women and their infants.

OBJECTIVES: To determine risk factors for GBS colonisation in Gambian mothers and in their infants from birth to day 60-89 of age. METHODS: Swabs and breastmilk from mothers/infant pairs were collected and cultured on selective agar. Negative samples were analysed for GBS DNA via real-time PCR. Positive isolates were serotyped using multiplex PCR and gel-agarose electrophoresis. RESULTS: Seven hundred and fifty women/infant pairs were recruited. 253 women (33.7%) were GBS-colonised at delivery. The predominant serotypes were: V (55%), II (16%), III (10%), Ia (8%) and Ib (8%). 186 infants were colonised (24.8%) at birth, 181 (24.1%) at 6 days and 96 at day 60-89 (14%). Infants born before 34 weeks of gestation and to women with rectovaginal and breastmilk colonisation at delivery had increased odds of GBS colonisation at birth. Season of birth was associated with increased odds of persistent infant GBS colonisation (dry season vs. wet season AOR 2.9; 95% CI 1.6-5.2). CONCLUSION: GBS colonisation is common in Gambian women at delivery and in their infants to day 60-89 and is dominated by serotype V. In addition to maternal colonisation, breastmilk and season of birth are important risk factors for infant GBS colonisation