Mechanical properties improvement of PM 400 series stainless steels via nickel addition

PM 409L and 434L grades of stainless steels have recently been selected at the optimum materials for automotive exhaust system applications, such as flanges and HEGO bosses. These applications are much more demanding than the most current PM stainless steel applications in terms of mechanical properties, weldability, and resistance to corrosion and thermal fatigue. Also important for these applications are elevated temperature mechanical strength, impact strength and resistance to stress relaxation at elevated temperatures. Significant improvements in both the room and elevated temperature mechanical stregths of these PM materials can be achieved by alloying with small amounts of nickel. The benefits of this approach are found to be significant in the case of 409L and moderate in the case of 434L.     

An atomistic study of the abrasive wear and failure of graphene sheets when used as a solid lubricant and a comparison to diamond-like-carbon coatings

The failure mechanisms of graphene under nanoscale sliding conditions are examined using atomistic simulations to evaluate its use as a solid lubricant and to simultaneously answer principal questions regarding wear of lamellar films comprised of atomically-thin sheets. To determine the failure behavior of graphene and the impact of adhesion on wear and failure, an asperity is slid over a substrate-supported graphene film with various adhesion strengths. For a purely-repulsive asperity, the graphene never delaminates and lower substrate-membrane adhesion appears to reduce the overall damage to the graphene layer and permits the recovery of more of the load-bearing capability of the graphene post-tearing. When tri-layer graphene is benchmarked with a 2 nm repulsive asperity against an 86% sp³ content diamond-like-carbon (DLC) coating of the same thickness (1.0 nm), the graphene supports up to 8.5 times the normal load of DLC during indentation, and up to twice the normal load of DLC during sliding even after failure of one or more layers. The preliminary results indicate that graphene has promise as a solid lubricant with thickness on the order of nanometers due to its atomically-thin configuration and high load carrying capacity.     

Electroaddressing Functionalized Polysaccharides as Model Biofilms for Interrogating Cell Signaling

Bacteria often reside at surfaces as complex biofilms in which an exopolysaccharide matrix entraps the population while allowing access to its chemical environment. There is a growing awareness that the biofilm structure and activity are integral to a wide array of properties important to health (the microbiome), disease (drug resistance) and technology (fouling). Despite the importance of bacterial biofilms, few experimental platforms and systems are available to assemble complex populations and monitor their activities. Here, a functionalized alginate composite material for creating in vitro model biofilms suitable for cell‐cell signaling studies by entrapping bacterial cells in situ is reported. Biofilm assembly is achieved using device‐imposed electrical signals to electrodeposit the stimuli‐responsive polysaccharide alginate. This electrodeposition mechanism is versatile in that it allows control of the bacterial population density and distribution. For instance, it is demonstrated that a mixed population can be homogeneously distributed throughout the biofilm or can be assembled as spatially segregated populations within a stratified biofilm. The “electroaddressable” biofilms are visualized using both a planar 2D chip with patterned electrodes and a microfluidic bioMEMS device with sidewall electrodes. Specifically, it is observed that bacteria entrapped within the model biofilm recognize and respond to chemical stimuli imposed from the fluidic environment. Finally, reporter cells are used to demonstrate that bacteria entrapped within this model biofilm engage in intercellular quorum sensing. This work demonstrates the functionality of the stimuli‐responsive polysaccharide by biofabricating pseudo‐3D cell‐gel biocomposites, mimicking the formation of biofilms, for interrogating phenotypes of E. coli bacterial populations. In addition to controlling assembly, the microfluidic device allows the biofilm to be monitored through the fluorescence methods commonly used in biological research. This platform technology should be able to be exploited for monitoring biofilm development, as well as for extending the understanding of the interactions between various bacterial species arranged in controlled patterns.     

Biofabricating Multifunctional Soft Matter with Enzymes and Stimuli‐Responsive Materials

Methods that allow soft matter to be fabricated with controlled structure and function would be beneficial for applications ranging from flexible electronics to regenerative medicine. Here, the assembly of a multifunctional gelatin matrix is demonstrated by triggering its self‐assembly and then enzymatically assembling biological functionality. Triggered self‐assembly relies on electrodeposition of the pH‐responsive hydrogelator, 9‐fluorenylmethoxycarbonyl‐phenylalanine (Fmoc‐Phe), in response to electrical inputs that generate a localized pH‐gradient. Warm solutions of Fmoc‐Phe and gelatin are co‐deposited and, after cooling to room temperature, a physical gelatin network forms. Enzymatic assembly employs the cofactor‐independent enzyme microbial transglutaminase (mTG) to perform two functions: crosslink the gelatin matrix to generate a thermally stable chemical gel and conjugate proteins to the matrix. To conjugate globular proteins to gelatin these proteins are engineered to have short lysine‐rich or glutamine‐rich fusion tags to provide accessible residues for mTG‐catalysis. Viable bacteria can be co‐deposited and entrapped within the crosslinked gelatin matrix and can proliferate upon subsequent incubation. These results demonstrate the potential for enlisting biological materials and mechanisms to biofabricate multifunctional soft matter.     

Simulation of Contaminates Around the Solid Immersion Lens in a Near-Field Optical Recording System

Accurate predictions of contamination in next-generation optical storage drives are paramount when active gap control is employed. In near-field recording devices, the read/write interface can be on the order of 20-30 nm, which means that the gap could be quite susceptible to contamination. Predictive modeling approaches for studying the behavior of contaminates in nanoscale hydrodynamic interfaces are needed. Here, we present such a model. The interface consists of a flat disk surface translating under a solid immersion lens (SIL) of hemispherical geometry. We present the computational modeling simulation results for nano-scale contaminates around the near-field SIL. The simulation shows that the discrete contaminates actually circumnavigate the SIL/disk interface during operation. We identify and discuss the external influences on the discrete contaminate particle behavior     

Low-Cost Fabrication of Tungsten-Rhenium Alloys for Friction Stir Welding Applications

Metallurgical and Materials Transactions B - Friction stir welding (FSW) of high-melting temperature alloys, such as steel and Inconel, requires tooling that can survive under the applied loads at...     

Long-term quality of life after treatment of laryngeal cancer. The Veterans Affairs Laryngeal Cancer Study Group

OBJECTIVE: To assess long-term quality of life in surviving patients with advanced laryngeal cancer. DESIGN: A follow-up long-term quality-of-life survey of patients randomized to the Veterans Affairs Laryngeal Cancer Study No. 268 on induction chemotherapy and radiation (CT + RT) vs surgery and RT. SETTING AND PATIENTS: Forty-six (71%) of the 65 surviving patients with prior stage III or IV laryngeal cancer who could be contacted completed the survey: 25 from the surgery and RT group and 21 from the CT + RT group. Baseline demographic and clinical characteristics among survey respondents were similar, except that those in the CT + RT group were significantly older (mean, 61.2 years) than those in the surgery and RT group (mean, 55.7 years; P<.05). INTERVENTIONS AND MAIN OUTCOME MEASURES: Patients completed the University of Michigan Head and Neck Quality of Life (HNQOL) instrument, the Medical Outcomes Studies Short-Form 36 (SF-36) general health survey, the Beck Depression Inventory as well as smoking and alcohol consumption surveys. RESULTS: Patients randomized to the CT + RT group had significantly better (P<.05) quality-of-life scores on the SF-36 mental health domain (76.0) than the surgery and RT group (63.0), and also had better HNQOL pain scores (81.3 vs 64.3). Compared with patients who underwent laryngectomy, patients with intact larynges (CT + RT with larynx) had significantly less bodily pain (88.5 vs 56.5), better scores on the SF-36 mental health (79.8 vs 64.7), and better HNQOL emotion (89.7 vs 79.4) scores. More patients in the surgery and RT group (28%) were depressed than in the CT + RT group (15%). CONCLUSION: Better quality-of-life scores in the CT + RT groups appear to be related to more freedom from pain, better emotional well-being, and lower levels of depression than to preservation of speech function.     

Local observability of nonlinear differential-algebraic equations(DAEs) from the linearization along a trajectory

The main results of this note establish sufficient rank conditions for local observability of nonlinear differential-algebraic equations (DAE) systems near a known trajectory associated with a given control. Verification of the observability rank condition is addressed, and the relationship with previous work on observability of DAE is indicated