Mechanism of alloying element vaporization during laser welding

Vaporization of alloying elements is a serious problem in the laser welding of many important engineering alloys. Since the available mass transfer correlations are not applicable for credible assessment of the rates of transport of vaporized species in the gas phase, the role of gas phase mass transfer in the overall vaporization of alloying elements was examined by conducting several critical experiments. The rates of transport of alloying elements in the weld pool were determined from numerically computed fluid flow fields. Since the weld pool is surrounded by plasma during laser welding, the role of plasma in the vaporization of alloying elements was physically modeled by allowing molten copper drops to vaporize isothermally both in the presence and absence of plasma. The transport of alloying elements in both liquid and gas phases was found to be rapid and the overall vaporization rates were controlled by the plasma influenced intrinsic vaporization of alloying elements at the weld pool surface. The experimentally obtained rates of vaporization of alloying elements from laser melted stainless steel weld pools were compared with the corresponding theoretically calculated values.     

The advancing-front mesh generation method revisited

This paper presents a mesh generation method of the advancing-front type which is designed in such a way that the well-known difficulties of the classical advancing-front method are not present. The retained solution consists of using the first steps of a Voronoï–Delaunay method to construct a background mesh which is then used to govern the algorithm. The two-dimensional case is considered in detail and possible extensions to adaption problems and three dimensions are indicated.     

Response of depressed adolescents to cognitive-behavioral treatment: Do differences in initial severity clarify the comparison of treatments?

Evaluated the impact of pretreatment depression severity and functional impairment on the response of 2 samples of older depressed adolescents (115 Ss total divided into low-severity groups and high-severity groups) to 2 group cognitive-behavioral treatments. Differences between the 2 active treatments and between active treatment and a waiting-list control condition were expected to be greater in the more severely depressed-impaired group. Improvement for the 2 active treatments in comparison to the control condition was greater in the more severely depressed group in one of the samples but not the other. The prediction that the relative effectiveness of the 2 treatments would be accentuated in the more severely depressed adolescents received no support in either sample. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of the inertia tensor in haptically perceiving where an object is grasped.

When an object is held and wielded, a time-invariant quantity of the wielding dynamics is the inertia tensor Iij. Examination of Iij as a function of different locations at which a cylindrical object is grasped revealed that the off-diagonal components of Iij, the products of inertia, related most systematically to grip position. In 3 experiments, Ss wielded an occluded rod held at an intermediate point along its length and reproduced, with the other hand, the felt grip position on a visible rod. In Exp 1, the wielded rods were homogeneous; in Exps 2 and 3, weights were added on either side of the grasp, with different manners of grasp contrasted in Exp 3. In all 3 experiments, perceived hand position was predicted by Iij. Discussion is focused on the role of Iij's eigenvalues in perceiving the magnitudes of objects and Iij's eigenvectors in perceiving hand–object relations (e.g., position of grasp). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adolescent psychopathology: II. Psychosocial risk factors for depression.

In a prospective study of adolescent depression, adolescents (N?=?1,508) were assessed at Time 1 and after 1 yr (Time 2) on psychosocial variables hypothesized to be associated with depression. Most psychosocial variables were associated with current (n?=?45) depression. Formerly depressed adolescents (n?=?217) continued to differ from never depressed controls on many of the psychosocial variables. Many of the depression-related measures also acted as risk factors for future depression (n?=?112), especially past depression, current other mental disorders, past suicide attempt, internalizing behavior problems, and physical symptoms. Young women were more likely to be, to become, and to have been depressed. Controlling for the psychosocial variables eliminated the gender difference for current and future but not for past depression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Appropriation of the Material of Places in the Landscape: the case of tufa and springs

Springs have long been recognized as being significant places in the landscape, and there is ample evidence of later-prehistoric and Roman activity at spring sites. The Christian appropriation of springs as 'places', either indirectly by assigning their origin to saints, or directly by building chapels and churches on spring-head sites, is also well evidenced. The possibility that the material of petrifying springs - tufa - was both transplanted and appropriated, and that the symbolic properties of the material may go back well into British prehistory, is explored.     

Selective interactions among the multiple connexin proteins expressed in the vertebrate lens: the second extracellular domain is a determinant of compatibility between connexins

Gap junctions are collections of intercellular channels composed of structural proteins called connexins (Cx). We have examined the functional interactions of the three rodent connexins present in the lens, Cx43, Cx46, and Cx50, by expressing them in paired Xenopus oocytes. Homotypic channels containing Cx43, Cx46, or Cx50 all developed high conductance. heterotypic channels composed of Cx46 paired with either Cx43 or Cx50 were also well coupled, whereas Cx50 did not form functional channels with Cx43. We also examined the functional response of homotypic and heterotypic channels to transjunctional voltage and cytoplasmic acidification. We show that all lens connexins exhibited sensitivity to cytoplasmic acidification as well as to voltage, and that voltage-dependent closure of heterotypic channels for a given connexin was dramatically influenced by its partner connexins in the adjacent cell. Based on the observation that Cx43 can discriminate between Cx46 and Cx50, we investigated the molecular determinants that specify compatibility by constructing chimeric connexins from portions of Cx46 and Cx50 and testing them for their ability to form channels with Cx43. When the second extracellular (E2) domain in Cx46 was replaced with the E2 of Cx50, the resulting chimera could no longer form heterotypic channels with Cx43. A reciprocal chimera, where the E2 of Cx46 was inserted into Cx50, acquired the ability to functionally interact with Cx43. Together, these results demonstrate that formation of intercellular channels is a selective process dependent on the identity of the connexins expressed in adjacent cells, and that the second extracellular domain is a determinant of heterotypic compatibility between connexins.     

Improving graduate student performance in cognitive assessment: The saga continues.

Investigators have concluded that excessive numbers of errors in test administration and scoring are routinely committed by both graduate students and practicing psychologists. Developing new methods for teaching assessment is viewed as a major means of improving competency. Unlike previous studies, this investigation examined the impact of both lecture and laboratory interventions designed to improve graduate student performance in assessment. Interventions consisted of weekly lecture quizzes and a variety of laboratory interventions. The results suggest that the interventions used can significantly improve students' lecture and laboratory performance when compared with controls. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Post and core reconstruction for fixed prosthodontic restoration

If the previous restorative therapy or dental caries has resulted in substantial loss of tooth structure, the abutment teeth for fixed prosthodontic restorations require a core reconstruction or a post and core. Small dentin defects can be restored with bonded cores; more extensive dentin defects that are often accompanied by previous endodontic treatment generally require additional support for the core material. A direct procedure with a bonded post is a viable treatment method. The decision to use either light-conducting all-ceramic zirconium or titanium as a post material depends on the aesthetic requirements present. The indications for a cast post and core as an indirect procedure for prosthodontic reconstructions appear to be decreasing. The learning objective of this article is to review the past and current post and core materials and techniques. Indications for core reconstruction with vital teeth and posts and cores for pulpless teeth are discussed.