Chromophore-Free Sealing and Repair of Soft Tissues Using Mid-Infrared Light-Activated Biosealants

Poor strength, infection, leakage, long procedure times, and inflammation limit the efficacy of common tissue sealing devices in surgeries and trauma. Light-activated sealing is attractive for tissue sealing and repair, and can be facilitated by the generation of local heat following absorption of nonionizing laser energy by chromophores. Here, the inherent ability of biomaterials is exploited to absorb nonionizing, mid-infrared (midIR) light in order to engender rapid photothermal sealing and repair of soft tissue wounds. In this approach, the biomaterial simultaneously acts as a photothermal convertor as well as a biosealant, which dispenses the need for exogeneous light-absorbing nanoparticles or dyes. Biomechanical recovery, mathematical modeling, histopathology analyses, tissue strain mapping using digital imaging correlation, and visualization of the biosealant-tissue interface using hyperspectral imaging indicate superior performance of midIR sealing in live mice compared to conventional sutures and glue. The midIR-biosealant approach demonstrates rapid sealing of soft tissues, improves cosmesis, lowers potential for scarring, obviates safety concerns because of the nonionizing light used, and allows adoption of a wide diversity of biomaterials. Taken together, the studies demonstrate a novel advance both in biomaterials for surgical sealing along with the use of nonionizing midIR light, with high potential for clinical translation.     

Use of recursive methods in fuzzy fault tree analysis: an aid to quantitative risk analysis

This paper demonstrates the use of recursive techniques in quantitative risk analysis when the probability of occurrence of the basic events is uncertain (fuzzy) in nature instead of having a precise value. Cases of both coherent and non-coherent fault trees with replicated events are dealt with. The analyses have been computerized using an IBM compatible personal computer (PC-AT). The source code is in C and uses Turbo-C graphics routines for creating plots. A wide variety of examples with different membership functions have been considered.     

Failure Analysis Approach to Fracture Studies in Powder Metallurgy Parts

This paper presents a failure analysis of tool steel and brass powder metallurgy (P/M) parts that failed during service. A detailed failure investigation of fractured tool steel and brass parts was carried out to assess the causes for their premature failures. The fractured surfaces of the broken pieces and the component surfaces were subjected to detailed examination. Investigations were carried out by visual methods, microhardness measurements, and using optical and scanning electron microscopes. In the case of the brass sample, visual examination of the surface indicated flat surface features. Detailed optical and electron microscopic studies corroborated by microhardness indentations have conclusively established that the failure was mainly due to the presence of very small impurities in the brass component material. In the case of the tool steel sample, the fractured surfaces of the component were subjected to destructive and nondestructive tests. Representative fractured pieces were examined visually and tested for their yield strength using simple tensile tests. Optical and scanning electron microscopies at appropriate magnifications were also performed to characterize its microstructure and fracture morphology. Detailed investigations of the tool steel part established that the failure was mainly due to inferior yield strength of the component resulting from improper heat treatment.     

Modelling and experimental investigation of devolatilizing wood in a fluidized bed combustor

A two-dimensional model is developed for the determination of devolatilization time and char yield of cylindrical wood particles in a bubbling fluidized bed combustor. By using the concept of shape factor, the model is extended to particles of cuboid shape. The model prediction of the devolatilization time agrees with the measured data (present and those reported in the literature) for cylindrical and cuboidal shaped particles within ±20% while the char yield is predicted within ±17%. Influence of some important parameters namely, thermal diffusivity, external heat transfer coefficient and shrinkage, on the devolatilization time and char yield are studied. Thermal diffusivity shows noticeable influence on devolatilization time. The external heat transfer coefficient shows little influence beyond a value of 300 W/(m² K). However particle shrinkage shows negligible effect on the devolatilization time but has a significant influence on the char yield.     

Grafting of methyl methacrylate to nitrocellulose by ceric ions

Studies were carried out on grafting of various vinyl monomers to nitrocellulose by ceric ions. It was observed that graft copolymerization occurred only with methyl methacrylate (MMA) and methyl acrylate monomer. The variables such as initiator concentration, monomer concentration, time of grafting, and nitrocellulose content on grafting of MMA are discussed. By hydrolyzing away the nitrocellulose backbone, the grafted poly(methyl methacrylate) branches were isolated and the >c?o peak at 1740 cm^?1 in the infrared spectra of these isolated branches gave definite evidence of grafting. The molecular weight of isolated branches has been determined by viscometry. The probable mechanism of grafting may be at the α-carbon atom of primary alcohol or at a C₂-C₃ glycol group of the anhydro glucose unit or at the hemiacetal group of the end unit of nitrocellulose, as nitrocellulose is formed by the partial nitration of cotton cellulose.     

Modal analysis of prestressed draft pad of freight wagons using finite element method

The present work intends to investigate dynamic behaviour of draft gear using finite element method. The longitudinal force that the draft gear absorbs usually leads to the failure of its components, especially, the load bearing draft pads. Dynamic behaviour of an individual draft pad and a draft gear is determined and characterized with exciting frequencies and corresponding mode shapes. The effect of compressive prestress load on the dynamic behaviour of an individual draft pad is also determined as the draft pads in assembled state are under constant axial compressive force in the draft gear. The vibration characteristics of individual draft pad are compared with draft pads that are part of draft gear. The modal analysis gives us a basis for subjecting a draft pad to higher frequency loading for determining its fatigue behaviour.

     

Machining characteristics and fracture morphologies in a copper-beryllium (Cu-2Be) alloy

The technology of materials removal is improved greatly by the introduction of advanced cutting tools like cubic boron nitride, ceramics, polycrystalline diamond and the more recent whisker-reinforced materials. In this paper, the influence of cutting temperature on machinability, mechanical properties, microstructure, and fracture morphology of Cu-2Be alloy using a polycrystalline diamond cutter is investigated. The information on machining, microstructure, and fracture morphology of Cu-2Be alloy are very useful to understand their fabrication characteristics and the basic mechanisms of its deformation and fracture. The machinability (in terms of surface finish) of Cu-2Be alloy is evaluated as a function of cutting temperature, resulting from wet and dry cutting. Machining is carried out on a Hardinge Cobra 42 CNC machine (Hardinge Inc., Elmira, NY), and the machining parameters used—cutting speed, depth of cut, and feed rate—are kept constant during both wet and dry cutting. The machined surface finish on Cu-2Be alloy is measured using a surface finish analyzer (Surftest 401, series 178) technique. The machined specimens are examined for their strength and hardness properties using a standard Universal Testing Machine and Rockwell hardness tester, respectively. Wet cutting (using coolants) produced a smooth surface finish when compared with dry cutting of the Cu-2Be alloy. The machined specimens are examined for their microstructural features using a Nikon optical microscope. The specimens are etched using a suitable etchant solution for revealing such microstructure constituents as grain size, phase proportions, and the possible overheated areas (especially in dry cutting). The fractured surfaces from the tensile and impact toughness tests are investigated for their fracture morphologies (dry and wet cutting) using a microprocessor-controlled scanning electron microscope (Jeol Model JSM 5910 LV). A detailed analysis is also made to understand and interpret the basic fracture mechanisms responsible for crack initiation and crack propagation. The Cu-2Be alloy showed relatively higher mechanical properties in wet cutting in comparison to dry cutting operations. Fracture studies demonstrated intergranular and ductile fractures as dominant modes of fracture mechanisms in Cu-2Be alloy.     

TeraGrid Science Gateways and Their Impact on Science

The Science Gateways program seeks to provide researchers with easy access to TeraGrid's high-performance computing resources. A look at four successful gateways illustrates the program's goals, challenges, and opportunities.     

Semiconcurrent Online Testing of Transition Faults through Output Response Comparison of Identical Circuits

We describe a method for online testing of delay faults based on the comparison of output responses of identical circuits. The method allows one of the circuits to participate in useful computations during the testing process, while the other circuit must be idle. We refer to this method as semiconcurrent online testing. While unknown input vectors are applied to the circuit that participates in useful computations, the proposed method applies modified vectors to the idle circuit. In this way, different conditions are created for the detection of delay faults, allowing identical delay faults that affect both circuits to be detected. In designing the modified vectors, we ensure that the expected fault-free responses of the two circuits are identical. We also ensure that the hardware for modifying the vectors applied to the idle circuit will be easy to implement on-chip.