As conventional lead solders are being replaced by Pb-free solders in electronic devices, the reliability of solder joints in integrated circuits (ICs) has become a high concern. Due to the miniaturization of ICs and consequently solder joints, the current density through the solder interconnects has increased causing electrical damage known as electromigration. Electromigration, atomic and mass migration due to high electron currents, is one of the most urgent reliability issues delaying the implementation of Pb-free solder materials in electronic devices. The research on Pb-free solders has mainly focused on the qualitative understanding of failure by electromigration. There has been little progress however, on the quantitative analysis of electromigration because of the lack of available material parameters, such as the effective charge, (z*), the driving force for electromigration. The research herein uses idealized interconnects to measure the z* of electromigration of Cu in Sn-3.0Ag-0.5Cu (SAC305) alloy under different experimental conditions. Planar SAC 305 interconnects were sandwiched between two Cu pads and subject to uniaxial current. The crystallographic orientation of Sn in these samples were characterized with electron backscatter diffraction (EBSD) and wavelength dispersive spectroscopy (WDS) before and after electromigration testing. Results indicate that samples with the c-axis aligned perpendicular to current flow, polycrystalline, and those with a diffusion barrier on the cathode side all inhibit the growth of intermetallic compounds (IMC). The effective charge values of Cu in SAC 305 under the different conditions tested were quantified for the first time and included in this dissertation. The following research is expected to help verify and improve the electromigration model and identify the desirable conditions to inhibit damage by electromigration in Pb-free solder joints.

Background

Results

Conclusions

Pancreatic ductal adenocarcinoma (PDA) is characterized by near universal mutations in the Kras proto-oncogene. Targeting constitutively active Kras to the pancreas results in the development of preneoplastic lesions and malignant progression similar to that observed in human PDA. Here we explore the capacity of mutant Kras to initiate PDA by reprogramming pancreatic acinar cells into a lineage that resembles human pancreatic intraepithelial neoplasia (PanIN), believed to be the most common route to PDA in man. Chronic pancreatitis is a major risk factor for human PDA, and chemically induced pancreatitis provides a permissive environment for PanIN and PDA formation in mouse models driven by mutant Kras. We found that mutant Kras dramatically alters the plasticity of acinar cells, preventing regeneration at the expense of a normally restricted, persistently ductal cell fate capable of giving rise to PanINs. Unlike acinar regeneration, which is characterized by activation of Beta-catenin signaling, Beta-catenin signaling is inhibited during early stages of Kras driven metaplasia. Using gain and loss of function approaches, we found that Beta-catenin is required for acinar regeneration and that enforced stabilization of Beta-catenin antagonizes acinar to ductal reprogramming that can give rise to PanINs. Therefore, Kras dependent specification of acinar derived PanINs depends on critical temporal thresholds of Beta-catenin signaling. Continuing the theme of Kras altering pancreatic plasticity, we investigated the role of miRNA processing in Kras driven PDA initiation. We found that deleting the critical miRNA biogenesis enzyme Dicer in the pancreas in the context of mutant Kras dramatically accelerates ductal metaplasia. However, this does not result in accelerated development of PanIN or PDA, and Dicer deficient cells do not contribute to PDA in mice. Dicer deficient acini display compromised expression of markers of acinar differentiation, which provides a permissive environment for Kras dependent ductal reprogramming. However, this differentiation state is unstable and displays considerable apoptosis, likely preventing the cells from contributing to PDA development. Therefore, we hypothesize that miRNA expression must be appropriately tuned to both permit preneoplastic differentiation and maintain cellular viability during Kras driven pancreatic transformation.

Introduction: People with disabilities are generally more vulnerable during disasters and publicemergencies than the general population. Physical, sensory and cognitive impairments may result ingreater difficulty in receiving and understanding emergency alert information, and greater difficulty intaking appropriate action. The use of social media in the United States has grown considerably inrecent years. This has generated increasing interest on the part of national, state and localjurisdictions in leveraging these channels to communicate public health and safety information. Howand to what extent people with disabilities use social and other communications media during publicemergencies can help public safety organizations understand the communication needs of thecitizens in their jurisdictions, and plan their social media and other communications strategiesaccordingly.

Methods: This article presents data from a survey on the use of social media and othercommunications media during public emergencies by people with disabilities conducted fromNovember 1, 2012 through March 30, 2013.

Results: The data presented here show four key results. First, levels of use of social media ingeneral are high for people with disabilities, as well as for the general population. Second, use ofsocial media during emergencies is still low for both groups. Third, levels of use of social media arenot associated with income levels, but are significantly and strongly associated with age: youngerpeople use social media at higher rates than older people in both groups (p,0.001). Fourth,differences in the use of social media during emergencies across disability types are slight, with theexception of deaf and hard-of-hearing respondents, the former more likely to have used social mediato receive (p¼0.002), verify (p¼0.092) and share (p¼0.007) emergency information.

Conclusion: These last two results suggest that effective emergency communications strategiesneed to rely on multiple media types and channels to reach the entire community. [West J EmergMed. 2014;15(5):567–574.]