Enhanced biocompatibility of Nitinol via surface treatment and alloying

It is projected that by 2020, there will be 138 million Americans over 45, the age at which the increased incidence of heart diseases is documented. Many will require stents. This multi-billion dollar industry, with over 2 million patients worldwide, 15% of whom use Nitinol stents have experienced a decline in sales recently, due in part to thrombosis. It is a sudden blood clot that forms inside stents. As a result, the Food and Drug Administration and American Heart Association are calling for a new generation of stents, new designs and different alloys that are more adaptable to the arteries. The future of Nitinol therefore depends on a better understanding of the mechanisms by which Nitinol surfaces can be rendered stable and inert. In this investigation, binary and ternary Nitinol alloys were prepared and subjected to various surface treatments such as electropolishing (EP), magnetoelectropolishing (MEP) and water boiling & passivation (W&P). In vitro corrosion tests were conducted on Nitinol alloys in accordance with ASTM F 2129-08. The metal ions released into the electrolyte during corrosion tests were measured by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). Biocompatibility was assessed by observing the growth of human umbilical vein endothelial cells (HUVEC) on the surface of Nitinol alloys. Static and dynamic immersion tests were performed by immersing the Nitinol alloys in cell culture media and measuring the amount of metal ions released in solution. Sulforhodamine B (SRB) assays were performed to elucidate the effect of metal ions on the growth of HUVEC cells. The surfaces of the alloys were studied using Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS) respectively. Finally, wettability and surface energy were measured by Contact Angle Meter, whereas surface roughness was measured by Atomic Force Microscopy (AFM). All the surface treated alloys exhibited high resistance to corrosion when compared with untreated alloys. SRB assays revealed that Ni and Cu ions exhibited greater toxicity than Cr, Ta and Ti ions on HUVEC cells. EP and MEP alloys possessed relatively smooth surfaces and some were composed of nickel oxides instead of elemental nickel as determined by XPS. MEP exhibited lowest surface energy and lowest surface roughness.

Differences in treatment and intervention needs of girls arrested for status versus criminal offenses

The purpose of this research was to explore the differences in factors associated with girls' status and criminal arrests. This study used data from six juvenile justice programs in multiple states, which was derived from the Juvenile Assessment and Intervention System (JAIS). The sample of 908 adolescent girls (ages 13-19) was ethnically and racially diverse (41% African American, 32% white, 12% Hispanic, 11% Native American and 4% Other). A structural equation model (SEM) was analyzed which tested the potential effects of adolescent substance use, truancy, suicidal ideation/attempt, self-harm, peer legal trouble, parental criminal history and parental and non-parental abuse on type of offense (status and criminal) and whether any of these relationships varied as a function of race/ethnicity. ^ Complex relationships emerged regarding both status and more serious criminal arrests. One of the most important findings was that distinct and different patterns of factors were associated with status arrests compared to criminal arrests. For example, truancy and parental abuse were directly associated with status offenses, whereas parental criminal history was directly related to criminal arrests. However, both status and criminal arrests shared common associations, including substance use, which signifies that certain variables are influential regarding both non-criminal and more serious crimes. In addition, significant meditating influences were observed which help to explain some underlying mechanisms involved in girls' arrest patterns. Finally, race/ethnicity moderated a key relationship, which has serious implications for treatment. ^ In conclusion, the present study is an important contribution to research regarding girls' delinquency in that it overcomes limitations in the existing literature in four primary areas: (1) it utilizes a large, multi-state, ethnically and racially diverse sample of justice system-involved girls, (2) it examines numerous co-occurring factors influencing delinquency from multiple domains (family, school, peers, etc.) simultaneously, (3) it formally examines race/ethnicity as a moderator of these multivariate relationships, and (4) it looks at status and criminal arrests independently in order to highlight possible differences in the patterning of risk factors associated with each. These findings have important implications for prevention, treatment and interventions with girls involved in the juvenile justice system.^

Enhanced Biocompatibility of NiTi (Nitinol) Via Surface Treatment and Alloying

It is projected that by 2020, there will be 138 million Americans over 45, the age at which the increased incidence of heart diseases is documented. Many will require stents. This multi-billion dollar industry, with over 2 million patients worldwide, 15% of whom use Nitinol stents have experienced a decline in sales recently, due in part to thrombosis. It is a sudden blood clot that forms inside stents. As a result, the Food and Drug Administration and American Heart Association are calling for a new generation of stents, new designs and different alloys that are more adaptable to the arteries. The future of Nitinol therefore depends on a better understanding of the mechanisms by which Nitinol surfaces can be rendered stable and inert. In this investigation, binary and ternary Nitinol alloys were prepared and subjected to various surface treatments such as electropolishing (EP), magnetoelectropolishing (MEP) and water boiling & passivation (W&P). In vitro corrosion tests were conducted on Nitinol alloys in accordance with ASTM F 2129-08. The metal ions released into the electrolyte during corrosion tests were measured by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). Biocompatibility was assessed by observing the growth of human umbilical vein endothelial cells (HUVEC) on the surface of Nitinol alloys. Static and dynamic immersion tests were performed by immersing the Nitinol alloys in cell culture media and measuring the amount of metal ions released in solution. Sulforhodamine B (SRB) assays were performed to elucidate the effect of metal ions on the growth of HUVEC cells. The surfaces of the alloys were studied using Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS) respectively. Finally, wettability and surface energy were measured by Contact Angle Meter, whereas surface roughness was measured by Atomic Force Microscopy (AFM). All the surface treated alloys exhibited high resistance to corrosion when compared with untreated alloys. SRB assays revealed that Ni and Cu ions exhibited greater toxicity than Cr, Ta and Ti ions on HUVEC cells. EP and MEP alloys possessed relatively smooth surfaces and some were composed of nickel oxides instead of elemental nickel as determined by XPS. MEP exhibited lowest surface energy and lowest surface roughness.

Role of Pseudomonas aeruginosa mifSR Two-Component System in Antibiotic Resistance and Biofilm Formation

Pseudomonas aeruginosa is an opportunistic pathogen found in a wide variety of environments. It is one of the leading causes of morbidity and mortality in cystic fibrosis patients, and one of the main sources of nosocomial infections in the United States. One of the most prominent features of this pathogen is its wide resistance to antibiotics. P. aeruginosa employs a variety of mechanisms including efflux pumps and the expression of B-lactamases to overcome antibiotic treatment. Two chromosomally encoded lactamases, ampC and poxB, have been identified in P. aeruginosa. Sequence analyses have shown the presence of a two-component system (TCS) called MifSR (MifS-Sensor and MifR-Response Regulator), immediately upstream of the poxAB operon. It is hypothesized that the MifSR TCS is involved in B-lactam resistance via the regulation of poxB. Recently, the response regulator MifR has been reported to play a crucial role in biofilm formation, a major characteristic of chronic infections and increased antibiotic resistance. In this study, mifR and mifSR deletion mutants were constructed, and compared to the wild type parent strain PAOl for differences in growth and B-lactam sensitivity. Results obtained thus far indicate that mifR and mifSR are not essential for growth, and do not confer B-lactam resistance under the conditions tested. This study is significant because biofilm formation and antibiotic resistance are two hallmarks of P. aeruginosa infections, and finding a link between these two may lead to the development of improved treatment strategies.

An evaluation of coping ability as a guide to the treatment of persons diagnosed with schizophrenia and substance abuse

This dissertation introduced substance abuse to the Dynamic Vulnerability Formulation (DVF) and the social competence model to determine if the relationship between schizophrenic symptomatology and coping ability in the DVF applied also to the dually diagnosed schizophrenic or if these variables needed to be modified. It compared the coping abilities of dually and singly diagnosed clients in day treatment and identified, examined, and assessed the relative influence of relevant mediating variables on two dimensions of coping ability of the dually diagnosed: coping skills and coping effort. These variables were: presence of negative and nonnegative symptoms, duration of mental illness, type of substance used, and age of first substance use.^ A priori effect sizes based on previous empirical research were used to interpret the results related to the comparison of demographic, socioeconomic, and treatment characteristics between the singly and dually diagnosed study samples. The data suggested that the singly diagnosed group had higher coping skills than the dually diagnosed group, particularly in the areas of housing stability, work affect, and total social adjustment. The dually diagnosed group had lower scores on one aspect of coping effort--agency or self-efficacy. The data supported the presence of an inverse relationship between symptom severity and coping skills, particularly for the dually diagnosed group. The data did not support the presence of an inverse relationship between symptom severity and coping effort, but did suggest a positive relationship between symptom severity and one measure of coping effort, agency, for the dually diagnosed group. Regression equations using each summary measure of coping skill--social adjustment and role functioning--yielded statistically significant F-ratios. Thirty-six percent of the variance in social adjustment and thirty-one percent of the variance in role functioning were explained by the relative influence of the relevant variables. Both negative and non-negative symptoms were the only significant predictors of social adjustment. The non-negative symptoms variable was the sole significant predictor of role functioning. The results of this study provided partial support for the use of the Dynamic Vulnerability Formulation (DVF) with the dually diagnosed. ^

Study of carbon nanotube film and shape memory alloys treatment for sensing and structural vibration control

Structural vibration control is of great importance. Current active and passive vibration control strategies usually employ individual elements to fulfill this task, such as viscoelastic patches for providing damping, transducers for picking up signals and actuators for inputting actuating forces. The goal of this dissertation work is to design, manufacture, investigate and apply a new type of multifunctional composite material for structural vibration control. This new composite, which is based on multi-walled carbon nanotube (MWCNT) film, is potentially to function as free layer damping treatment and strain sensor simultaneously. That is, the new material integrates the transducer and the damping patch into one element. The multifunctional composite was prepared by sandwiching the MWCNT film between two adhesive layers. Static sensing test indicated that the MWCNT film sensor resistance changes almost linearly with the applied load. Sensor sensitivity factors were comparable to those of the foil strain gauges. Dynamic test indicated that the MWCNT film sensor can outperform the foil strain gage in high frequency ranges. Temperature test indicated the MWCNT sensor had good temperature stability over the range of 237 K-363 K. The Young’s modulus and shear modulus of the MWCNT film composite were acquired by nanoindentation test and direct shear test, respectively. A free vibration damping test indicated that the MWCNT composite sensor can also provide good damping without adding excessive weight to the base structure. A new model for sandwich structural vibration control was then proposed. In this new configuration, a cantilever beam covered with MWCNT composite on top and one layer of shape memory alloy (SMA) on the bottom was used to illustrate this concept. The MWCNT composite simultaneously serves as free layer damping and strain sensor, and the SMA acts as actuator. Simple on-off controller was designed for controlling the temperature of the SMA so as to control the SMA recovery stress as input and the system stiffness. Both free and forced vibrations were analyzed. Simulation work showed that this new configuration for sandwich structural vibration control was successful especially for low frequency system.

Enhanced Growth of Tetracycline-susceptible Soil Bacteria Treated with Iron and Oxytetracycline

Antibiotic resistance has become an important area of research because of the excessive use of antibiotics in clinical and agricultural settings that are driving the evolution of antibiotic resistant bacteria. However, drug tolerance is a naturally occurring phenomenon in soil communities, and is often linked to those soils that are exposed to heavy metals as well as antibiotics. Resistance to antibiotics maybe coupled with resistance to heavy metals in soil bacteria through efflux pumps that can be regulated by iron. Although considered s a heavy metal, iron is an essential component of life that regulates gene expression through the Ferric Uptake Regulator (Fur) protein. This master regulator protein is known to control siderophore production, and other biological pathways. As a suspected controller of biofilm formation, the role of Fur in environmental antibiotic resistance may be greater than is currently realized. In this study, we sought to explore a potential Fur-regulated drug tolerance pathway by understanding the response of soil bacteria when stressed with oxytetracycline and iron. Bacteria were collected from two locations in Miami Dade County. Isolates were first tested using Kirby-Bauer Disk Diffusion tests for antibiotic resistance/susceptibility and identified by 16S rDNA sequencing. A 96-well growth assay was developed to measure planktonic cell growth with 3 mM FeCl3, Oxytetracycline HCl, and the combination treatments. A Microtiter Dish Biofilm Formation Assay was employed and Fur diversity was evaluated. Tetracycline-susceptible bacterial isolates developed drug resistance with iron supplementation, but iron did not enhance biofilm formation. Development of a Fur-dependent drug resistance may be selected for, but further study is required to evaluate Fur evolution in the studied isolates. Gene expression analysis is also needed to further understand the ecological role of Fur and antibiotic resistance.