Modification and Integration of Shape Memory Alloys Through Thermal Treatments and Dissimilar Metal Joining

While Shape Memory Alloys (SMAs) have been the topic of numerous studies throughout their history, over fifty years after the first observation of the shape memory effect, their widespread use is still limited by the complexity of tuning the shape memory response and furthermore the difficulty in incorporating the materials selectively into practical systems. Recent advancements, however, show the promise of SMAs for use in micro-electro-mechanical systems (MEMS) and medical devices where their unique properties can provide advanced functionalities. This dissertation investigates the use of laser-based treatments for the modification of shape memory properties as well as the joining of a shape memory alloy to a dissimilar metal through a novel process. The shape memory properties of SMAs are a strong function of composition, thermal treatments, microstructure, ambient temperature, and stress state. These effects are often intertwined, further disguising their true relationships. The use of thermal annealing for the formation of non-equilibrium precipitates in Ti-rich NiTi thin films is investigated for control over martensitic microstructure, transformation temperatures, and shape memory recovery. Modifications to shape memory properties are investigated through the use of temperature-dependent optical microscopy, temperature-dependent X-ray diffraction, and nano-indentation. As shape memory alloys are increasingly applied at smaller length scales due to advantages in achievable actuation frequency and the growth of micro-scale applications in medical devices, the anisotropy of the shape memory response at the grain level becomes an important consideration for optimizing device performance. The formation of crystallographic texture in NiTi thin films through controlled melting and abnormal grain growth during solidification is investigated through the use of x-ray diffraction and electron backscatter diffraction measurements. An experimentally validated Monte-Carlo grain growth model is developed to predict the texture formation based on the anisotropy in the surface energy between the growing grains and the adjacent liquid. Despite their unique properties, SMAs are not expected to entirely replace more commonly used alloys in most conceivable applications. Rather, these materials are envisioned to be used selectively, where their properties are most advantageous. Joining dissimilar metals, however, is oftentimes made difficult by the formation of brittle intermetallics when the two base materials are mixed. A novel joining process, Autogenous Laser Brazing, is described for the joining of a shape memory alloy to a dissimilar metal. The morphology and strength of the resultant joints is experimentally characterized. Fundamental understanding of the joint formation mechanism is developed through spatially-resolved composition and phase measurements and predictive numerical simulations. The ability to form joints between materials with different geometries is crucial for the wide applicability of a joining process. To this end, the Autogenous Laser Brazing process is further developed for application to tubular structures. The laser scanning scheme is revised to provide uniform heating both in the circumferential and radial directions. The resultant joints are characterized using spatially resolved phase and material property maps and are found to be formed under a different mechanism than the wire samples

Laser Autogenous Brazing of Biocompatible, Dissimilar Metals in Tubular Geometries

The successful joining of dissimilar metal tubes would enable the selective use of the unique properties exhibited by biocompatible materials such as stainless steel and shape memory materials such as NiTi, to locally tailor the properties of implantable medical devices. The lack of robust joining processes for the dissimilar metal pairs found within these devices, however, is an obstacle to their development and manufacture. Traditional joining methods suffer from weak joints due to the formation of brittle intermetallics or use filler materials that are unsuitable for use within the human body. This study investigates a new process, Laser Autogenous Brazing, that utilizes a thermal accumulation mechanism to form joints between dissimilar metals without filler materials. This process has been shown to produce robust joints between wire specimens but requires additional considerations when applied to tubular parts. The strength, composition, and microstructure of the resultant joints between NiTi and Stainless Steel are investigated and the effects of laser parameters on the thermal profile and joining mechanism are studied through experiments and numerical simulations

Effects of Interfacial Geometry on Laser Joining of Dissimilar NiTi to Stainless Steel Wires

Joining of the dissimilar metal pair NiTi to stainless steel is of great interest for implantable biomedical applications. Formation of brittle intermetallic phases requires that the joining processes limit the amount of over-melting and mixing along the interface. Thus, laser joining is a preferred method due to its ability to precisely control heat input. This study explores a method of using a cup and cone interfacial geometry, with no filler material, to increase the tensile strength of the joint. Not only does the cup and cone geometry increase the surface area of the interface, but it also introduces a shear component, which is shown to be beneficial to tensile strength of the wire as well. The fracture strength for various cone apex angles and laser powers is determined. Compositional profiles of the interfaces are analyzed. A numerical model is used for explanation of the processing

Clustering Malicious DNS Queries for Blacklist-Based Detection

Some of the most serious threats to network security involve malware. One common way to detect malware-infected machines in a network is by monitoring communications based on blacklists. However, such detection is problematic because (1) no blacklist is completely reliable, and (2) blacklists do not provide the sufficient evidence to allow administrators to determine the validity and accuracy of the detection results. In this paper, we propose a malicious DNS query clustering approach for blacklist-based detection. Unlike conventional classification, our cause-based classification can efficiently analyze malware communications, allowing infected machines in the network to be addressed swiftly

Oligo-recurrence from anaplastic lymphoma kinase-rearranged lung adenocarcinoma

Anaplastic lymphoma kinase rearranged non-small-cell lung cancer is a rare disease. Among them, a subset of patients exist who exhibit relatively slowly progressing symptoms and have oligo-metastases. In this article, we present two cases of ALK rearran-ged lung adenocarcinoma in patients who experienced postoperative oligo-recurrence. Both cases were treated with surgical resection and gamma knife irradiation for oligo-recurrence. After local therapy, the first patient remained disease free for over  23 months; the second for over 18 months. It appears that some patients with ALK rearranged NSCLC experience oligo-recurrence in their clinical course. For such patients, appropriate local therapy may be beneficial in improving both the quality of life and the prognosis

A Superficial Analysis Approach for Identifying Malicious Domain Names Generated by DGA Malware

Some of the most serious security threats facing computer networks involve malware. To prevent malware-related damage, administrators must swiftly identify and remove the infected machines that may reside in their networks. However, many malware families have domain generation algorithms (DGAs) to avoid detection. A DGA is a technique in which the domain name is changed frequently to hide the callback communication from the infected machine to the command-and-control server. In this article, we propose an approach for estimating the randomness of domain names by superficially analyzing their character strings. This approach is based on the following observations: human-generated benign domain names tend to reflect the intent of their domain registrants, such as an organization, product, or content. In contrast, dynamically generated malicious domain names consist of meaningless character strings because conflicts with already registered domain names must be avoided; hence, there are discernible differences in the strings of dynamically generated and human-generated domain names. Notably, our approach does not require any prior knowledge about DGAs. Our evaluation indicates that the proposed approach is capable of achieving recall and precision as high as 0.9960 and 0.9029, respectively, when used with labeled datasets. Additionally, this approach has proven to be highly effective for datasets collected via a campus network. Thus, these results suggest that malware-infected machines can be swiftly identified and removed from networks using DNS queries for detected malicious domains as triggers

Nintedanib-mediated improvement in CT imaging in pulmonary fibrosis associated with systemic scleroderma

Nintedanib is an antifibrotic drug that has an inhibitory effect on growth factor tyrosine kinases. In patients with idiopathic pulmonary fibrosis and systemic scleroderma-associated interstitial pneumonia (SSc-IP), nintedanib has been effective in suppressing the decline in forced vital capacity over time and the onset of acute exacerbation of interstitial pneumonia. Here, we report a SSc-IP patient who showed an improvement on CT images following nintedanib treatment. To our knowledge, this is the first report of such a case. Although SSc-IP patients are very rare, additional clinical experience and understanding will be required to prove the therapeutic benefit of nintedanib in these cases in relation to improved chest images

Laser Autogenous Brazing of Biocompatible, Dissimilar Metals in Tubular Geometries

ABSTRACT The successful joining of dissimilar metal tubes would enable the selective use of the unique properties exhibited by biocompatible materials such as stainless steel and shape memory materials such as NiTi, to locally tailor the properties of implantable medical devices. The lack of robust joining processes for the dissimilar metal pairs found within these devices, however, is an obstacle to their development and manufacture. Traditional joining methods suffer from weak joints due to the formation of brittle intermetallics or use filler materials that are unsuitable for use within the human body. This study investigates a new process, Laser Autogenous Brazing, that utilizes a thermal accumulation mechanism to form joints between dissimilar metals without filler materials. This process has been shown to produce robust joints between wire specimens but requires additional considerations when applied to tubular parts. The strength, composition, and microstructure of the resultant joints between NiTi and Stainless Steel are investigated and the effects of laser parameters on the thermal profile and joining mechanism are studied through experiments and numerical simulations

IL-17F Induces CCL20 in Bronchial Epithelial Cells

IL-17F plays a crucial role in airway inflammatory diseases including asthma, but its function has not been fully elucidated. CCL20 is also involved in allergic airway inflammation, while its regulatory mechanisms remain to be defined. To further identify a novel role of IL-17F, the expression of CCL20 by IL-17F in bronchial epithelial cells and the signaling mechanisms involved were investigated. Bronchial epithelial cells were stimulated with IL-17F, and the levels of CCL20 gene and protein measured, with the effects of the addition of various kinase inhibitors and siRNAs also investigated. IL-17F significantly induced the expression of CCL20 gene and protein. Pretreatment with inhibitors for MEK1/2, Raf1 and MSK1, and overexpression of a Raf1 dominant-negative mutant significantly diminished IL-17F-induced CCL20 production. Moreover, transfection of the siRNAs targeting MSK1, p90RSK, and CREB blocked CCL20 expression. These findings suggest that IL-17F is able to induce CCL20 via Raf1-MEK1/2-ERK1/2-MSK1/p90RSK-CREB signaling pathway in bronchial epithelial cells. The IL-17F/CCL20 axis may be a novel pharmacological target for asthma