Moving Boundary Transport Phenomena in Selective Area Laser Deposition Process

The overall selective area laser deposition process was modeled using the two-layer, three dimensional solid phase heat transfer with the moving boundary condition considered, gas phase mass transfer, and film growth coupled equations. A modified front-tracking finite difference method was used to solve the moving boundary heat conduction in thick deposits. The results correlate with the experimental observations.Mechanical Engineerin

Design of a Solid Freeform Fabrication Diamond Reactor

Solid Freeform Fabrication (SFF) has progressed from the visualization aided stage of computer aided designs (CAD) to rapid prototyping of structural parts. Among the promising techniques for producing structural prototypes is the technology ofchemical vapor deposition (CVD) ofpolycrystalline diamond. This paper discusses the thermodynamic and kinetic theories that suggest that structural diamond may be rapidly deposited at rates approaching 1 mmJhr from the vapor phase at metastable thermodynamic conditions. The design of a reactor that will produce structural diamond prototypes is discussed. This reactor combines downstream microwave plasma enhanced chemical vapor deposition (DMWPECVD) with a scanned CO2 laser that locally heats the substrate to diamond deposition temperatures. The input:Fases are H2, 02' CH4, and Ar. The operating pressure range of the reactor is 1 x 10- to 7 x 102 Torr. The reactor is designed for in situ determination of deposit thickness while deposition occurs as well as having the capacity of fitting on an existing resonance enhanced multiphoton ionization time of flight mass spectroscopy (REMPITOFMS) apparatus that will allow for plasma diagnostics immediately above the heated substrate. Plasma diagnostics will be employed to determine the active metastable species that results in diamond deposition so that optimization can be made ofthe operating parameters to maximize diamond selectivity and deposition rate.Mechanical Engineerin

A Model for Pastoral Nurture and Care to African American Persons Who Are HIV Infected or Living With AIDS

Problem. Current statistics reveal that the African American community is disproportionately affected by the AIDS epidemic. The rate of infection for other groups is being impacted by the community education programs, prevention strategies, and service organizations. Messages and service relevant to the African American context are needed. A resource guide and a training model for pastoral care to better serve the Black AIDS patient could address this problem. Method. Published rates of HIV infection for the general public and specific groups in the United States are examined to understand of the impact of AIDS on the Black community. Two pastoral-care training programs are examined for strengths and weaknesses in responding to the African American AIDS patient. Issues impacting the Black community, relative to AIDS, are examined to reveal strategies for providing care. Issues relevant to the pastoral caregiver\u27s response to the African American AIDS patient are discussed. The model for pastoral care is based on the preceding research. A model for training pastoral caregivers to effectively respond to the African American AIDS patient is proposed with recommendations for implementation. Results. Relevant issues of African American life give some indication as to why the Black AIDS numbers are increasing, and the appearance of AIDS denial in the Black community. Current training prepares pastoral caregivers to provide care for AIDS patients in general. Training for the African American context is not provided. This project presents a resource guide and a model for training caregivers for the African American context. Conclusions. Special training to respond to the African American AIDS patient is needed. Black life in America presents specific challenges impacting the Black AIDS patient\u27s ability to cope. Training for caregivers has been in existence for approximately ten years. This project can provide the specific training needed to prepare caregivers to help the Black AIDS patient. African Americans must lead in providing care for the Black AIDS patient. The Black church and the Black pastor are central in this process. Use of the guide, the training model, evaluation, and adjustments over time will result in the effective care and intervention needed in the Black community in response to the AIDS epidemic

Preparation and Properties of In-Situ Devices Using the SALD and SALDVI Techniques

One of the many advantages of Selective Area Laser Deposition (SALD) and Selective Area Laser Deposition Vapor Infiltration (SALDVI) is that they can be used to embed in-situ micro-sensors within macro-components. A single-point SiC/C thermocouple sensor embedded within a SiC macro-component and electrically insulated with silicon nitride layers has been demonstrated. In many applications, multi-point sensors within a single component are needed, e.g., in monitoring the temperature gradient and distribution at different positions. In this paper, multi-point thermocouple devices are demonstrated. The macro-component is a SiC bulk shape made by infiltrating vapor deposited silicon carbide into a silicon carbide powder bed using the SALDVI technique. Multiple SiC/C thermocouples are embedded in-situ in the SiC bulk shape using the SALD technique. The transient and steady state responses ofthe embedded thermocouples are compared to reference thermocouples probing the surfaces of the bulk shape.Mechanical Engineerin

Selective Area Laser Deposition Joining of Aluminum Oxide

Selective area laser deposition (SALD) is a chemical vapor deposition technique used to deposit ceramic material. The technique allows localized deposition in the area of the laser spot; complex depositions can be achieved through the use of a computer control program. It is possible to free form fabricate arbitrary shapes. In particular by defining the space between two work pieces as the envelope for deposition, it is possible to form a monolithic joint. The use of a trimethylaluminum and diethyl ether precursor system is explored as a means of depositing aluminum oxide. The alumina is used as joint fill material for alumina SALD joining.Mechanical Engineerin

Religious Popular Music: Between the Instrumental, Transcendent and Transgressive

The use of post-rock ‘n’ roll popular music genres by religious groups is accompanied by a notable ambiguity: Is religious popular music designed to be an instrumental tool for outreach/evangelism, or does it have an intrinsic value in summoning and exploring the transcendent? The article focuses on the previously rarely explored idea that the instrumental use of popular music in Christian andJewish settings is often much more important than its transcendent qualities. The importance of the instrumental in Christian and Jewish popular music reveals itself in subtle and not-so-subtle signifiers and practices that point to an anxious desire to discipline music’s possible transgressive force

Method of producing parts and molds using composite ceramic powders

A method and apparatus for selectively sintering a layer of powder to produce a part comprising a plurality of sintered layers. The apparatus includes a computer controlling a laser to direct the laser energy onto the powder to produce a sintered mass. The computer either determines or is programmed with the boundaries of the desired cross-sectional regions of the part. For each cross-section, the aim of the laser beam is scanned over a layer of powder and the beam is switched on to sinter only the powder within the boundaries of the cross-section. Powder is applied and successive layers sintered until a completed part is formed. Preferably, the powder comprises a plurality of materials having different dissociation or bonding temperatures. The powder preferably comprises blended or coated materials, including precursor materials which are formed into a mass at the irradiated locations, and which either react due to the laser thermal energy or in a later heat treatment to form a compound with properties different than the precursors. Examples are disclosed wherein a compound is formed which has a significantly higher melting point than that of one or more of the precursor powders. A ceramic part, such as a mold for investment casting, may be formed according to the method, where a first material (e.g., ammonium dihydrogen phosphate) has a melting point sufficiently low that it is melted so as to bind the second material (e.g., alumina). Subsequent heat treatment enables chemical reaction of the two materials to form a ceramic (e.g., aluminum phosphate) capable of withstanding high temperatures.Board of Regents, University of Texas Syste

Gas Phase Solid Freeform for Fabrication of Three-dimensional Ceramic Structures

Solid free form of ceramic materials can be achieved by deposition from the gas phase. The Selective Area Laser Deposition, or SALD, technique can be utilized to make ceramic depositions with a uniform chemical composition. In order to make all classes of ceramics, including carbides, nitrides, and oxides, selection of a precursor is an essential step. Often the correct precursor for the deposition requires a special environment, namely, one that can be uniformly heated. System design for a heated deposition chamber is discussed as well as preliminary tests of the system functionality. Silicon Carbide depositions were performed as a means of evaluating system parameters.Mechanical Engineerin

Selective Area Laser Deposition for Silicon Nitride Joining

Ceramic joining is a difficult step in ceramic manufacturing. Joining ceramics, in a chemically homogeneous way, can be performed through the repurposing of an additive manufacturing technique involving local deposition of ceramics from the gas phase. Selective area laser deposition uses a gas phase precursor environment and a laser heat source to form ceramic deposits. These deposits can be positioned with great spatial resolution; as such, it is possible to form the joint with the ceramic material to create a monolithic structure. Silicon nitride is explored as a joining material for silicon nitride work pieces. The experimental conditions are described and the joint formation is characterized.Mechanical Engineerin

Mycophenolic Acid Inhibits Dengue Virus Infection by Preventing Replication of Viral RNA

AbstractDengue fever is a mosquito-borne viral disease of global importance with no available antiviral therapy. We assessed the ability of mycophenolic acid (MPA), a drug currently used as an immunosuppressive agent, to inhibit dengue virus (DV) antigen expression, RNA replication, and virus production. Pharmacological concentrations of MPA effectively blocked DV infection, decreasing the percentage of infected cells by 99% and the levels of secreted virus by up to a millionfold. Results were reproduced with four hepatoma cell lines and different flaviviruses, including a recent West Nile virus isolate. Experiments were performed to define the stage in the viral lifecycle at which MPA abrogates infection. Early steps in viral infection, such as viral entry and nucleocapsid uncoating, were not the primary targets of MPA action since its inhibitory effect was retained when naked DV RNA was transfected directly into cells. Biosynthetic labeling experiments showed that MPA did not block the initial phase of viral translation but did interfere with viral protein synthesis in the amplification phase. Quantitative RT-PCR demonstrated that MPA prevented the accumulation of viral positive- and negative-strand RNA as the infection proceeded. We conclude that MPA inhibits flavivirus infection by preventing synthesis and accumulation of viral RNA