Metal Segregation During the Solidification of Titanium-Aluminum Alloys for 3D Printing Applications

Titanium-Aluminum alloys are one of the widely used alloys in multiple engineering applications. They are highly preferred in Selective Laser Melting (SLM) processes due to their low density, high melting temperature, and good strength. Segregation occurs during the solidification of most alloys and produces a non-uniform distribution of atoms. In SLM, segregation may depict the type of adhesion between the two deposited interfacial layers and the strength between the interphase between an already solidified layer and a new one, and overall, the quality of the printed part. In order to avoid segregation, the understanding of the segregation behavior at atomistic level is important. The main goal of this work is to understand the metal segregation in titanium-aluminum alloys for 3D printing applications using molecular simulations. For this the solidification of metal alloys is computationally simulated and the atomic ordering and structural transformations of the systems are studied. The thermal stability of different compositions of titanium-aluminum metal alloys and the size effects of the system on atomic ordering, structural transformation, and thermal stabilization of the alloys using Molecular Dynamics (MD) simulations is done. MD simulations are widely used in the studies of atomic transformations and structural evolutions of molecular systems and require the use of forcefields to describe the forces between atoms. In addition to the main goal, in this the performance of the Zope-Mishin Embedded Atom Method (EAM) and the Sun-Ramachandranan-Wick Modified Embedded Atom Method iv (MEAM) potential developed for the titanium-aluminum systems is evaluated. This work is divided into two parts. In the first part, the simulations are carried out in nine different compositions of 3.4 nm titanium-aluminum spherical nanoclusters with the timestep of 2 fs, the equilibration time of 50 ps, and the total simulation time of 2 ns and in the second part the simulations are carried out in two titanium-rich clusters of the same composition but different sizes are done at the timestep of 1 fs, the equilibration time of 100 ps, and the total simulation time of 1 ns. Each study is done twice using two different forcefields each time. The clusters are melted at high temperature and solidified at room temperature (300K) using simulated annealing. The analysis is done using the radial density distribution of atoms, the structural evolutions from the trajectories, and the melting temperature calculations using the combination of caloric and heat capacity curves using both forcefields. From the EAM potential, the solidified titanium-rich clusters show an inclination to icosahedral geometry whereas the MEAM potential shows the solidified aluminum-rich clusters to have an inclination to truncated octahedral geometry. Moreover, MEAM calculated the melting temperature of pure aluminum nanocluster at 711.76K and pure titanium nanocluster at 1185.36K. In the clusters except for the ones with high titanium concentration, aluminum migrates to the surface upon solidification. Due to the presence of titanium in the grain boundary making the adhesion between two SLM interfacial layers stronger. These high titanium clusters are found to have low segregation and suggested in SLM printing applications. The size effect study done shows no significant change in the properties of the structures or the melting temperatures

Sustained release nanoparticles containing acyclovir prodrugs for ocular herpes simplex keratitis and characterization of folate transport proteins in a corneal epithelial cell line

Dissertation advisor: Ashim K. MitraTitle from PDF of title page, viewed on December 21, 2011VitaIncludes bibliographic references (p. 148-160)Thesis (Ph.D.)--School of Pharmacy and Dept. of Chemistry. University of Missouri-Kansas City, 2011Ocular herpes is a persistent viral infection caused by the herpes simplex virus-1. It is one of the most common infectious diseases causing corneal blindness in the United States. In this study, polymeric nanoparticles of stereoisomeric di-peptide prodrugs of acyclovir (L-valine- L-valine-ACV, L-valine-D-valine-ACV, D-valine-L-valine-ACV, and D-valine-D-valine-ACV) were developed and characterized for the treatment of ocular herpes keratitis. L-valine-Lvaline- ACV and L-valine-D-valine-ACV were determined to be optimum in terms of enzymatic stability, uptake and cytotoxicity. Uptake and docking results indicated that Lvaline in the terminal position increases the affinity of prodrug to the peptide transporter protein. Entrapment efficiency values of L-valine-L-valine-ACV and L-valine-D-valine-ACV were optimal with PLGA 75:25 and PLGA 65:35 polymers, respectively. In vitro release of prodrugs from nanoparticles exhibited a biphasic release pattern with initial burst phase followed by sustained release. Dispersion of nanoparticles in thermosensitive gels eliminated the burst release phase. Novel nanoparticulate systems of dipeptide prodrugs of ACV suspended in thermosensitive gels may provide sustained delivery following topical administration. The uptake of nanoparticles into corneal cells can be enhanced by attachment of cell-specific ligands such as folate and biotin. Folate carrier-mediated system is widely used in the targeted delivery of drugs. Thus Staten's Seruminstitut rabbit corneal (SIRC) epithelial cell line was investigated for the expression of folate transport proteins that can be utilized for targeted drug delivery of folate-conjugated nanoparticles and prodrugs to cornea. Linear increase in [3H] Folic acid uptake was observed over 30min. The process followed saturation kinetics with apparent Km of 14.2 nM, Vmax of 1.5x10-5 micro.moles/min/mg protein and Kd of 2.1x10-6 min.-1 Uptake was inhibited in the presence of structural analogs (cold folic acid, MTF and MTX) but structurally unrelated vitamins did not show any effect. RT-PCR and Western blot analysis confirmed the presence of folate receptor-α (FR-α) and proton-coupled folate transporter (PCFT). This work demonstrated the functional and molecular presence of FR-α and PCFT in SIRC cells that can be utilized for enhanced uptake of folate conjugated nanoparticles and prodrugs. In a different study the differential expression of FR-α, sodium dependent multivitamin transporter (SMVT) and amino acid transporter B (0, +) in retinoblastoma (Y-79) and retinal pigment epithelial (ARPE-19) cells. Higher expression of FR-α, SMVT and B (0, +) at mRNA level was observed in cancerous Y- 79 cells compared to normal ARPE-19 cells.Introduction -- Rationale for investigation -- Ocular sustained release nonoparticles containing stereoisomeric di-peptide prodrugs of acyclovir -- Rationale for investigation -- Functional characterization of folate transport proteins in staten's seruminstitut rabbit corneal epithelial cell line -- Rationale for investigation -- Differential expressions of folate receptor-alpha (FR-A), sodium dependent multivitamin transporter (SMVT), and neutral and catonic amino acid transporter B [super] (0, +) in human retinoblastoma (Y-79) and normal human retinal (ARPE-19) cell lines -- Summary and recommendations -- Appendi

ANALISIS TEKNIK PERGERAKAN KAMERA PADA FILM BERGENRE ACTION FAST AND FURIOUS 7

ABSTRAK ANALISIS TEKNIK PERGERAKAN KAMERA PADA FILM BERGENRE ACTION FAST AND FURIOUS 7 (Jwala Candra Gita Kosala, 2017, 72 halaman). Skripsi S-1 Program Studi Televisi dan Film, Jurusan Seni Media Rekam, Fakultas Seni Rupa dan Desain, Institut Seni Indonesia Surakarta. Penelitian film action Fast and Furious 7 dilatar belakangi oleh adanya aksi berbahaya, antara lain seperti petarungan di atas pesawat, peledakan bom, bertarung atas gedung pencakar langit, serta identik dengan aksi kebut-kebutan mobil di jalanan, sehingga sisi dramatis film ini mampu mempengaruhi daya tarik penonton. Peranan teknik pergerakan kamera pan, tilt, tracking, crane shot, crabbing, dan zooming, pada tiap adegan action film Fast and Furious 7 dibentuk saat kamera bergerak, sehingga mempengaruhi type of shot dan ukuran gambar yang diambil. Begitu pula sebaliknya, ketika objek yang bergerak, maka juga akan mempengaruhi type of shot dan ukuran gambarnya. Permasalahan ini difokuskan pada persoalan bagaimana peranan teknik pergerakan kamera yang digunakan dalam film action Fast and Furious 7 melalui analisis type of shot (ukuran gambar), camera angle (sudut pengambilan gambar) dan camera movement (gerakan kamera). Sumber acuan konseptual diacu dari pendapat Himawan Pratista dan Januarius Andi Purba yang menjabarkan pengetahuan tentang teknik pergerakan kamera dan genre film, sehingga beberapa acuan tersebut menunjang proses penelitian tentang analisis film dari segi sinematiknya. Sumber data diperoleh melalui observasi dan studi pustaka. Proses analisis terdiri dari beberapa tahapan yaitu reduksi data, penyajian data, penarikan kesimpulan dan verifikasi. Penelitian ini menunjukkan kesimpulan bahwa peranan teknik pergerakan kamera pan, tracking, zooming dan crane shot pada adegan film action Fast and Furious 7 cenderung digunakan untuk mengungkapkan lingkungan sekitar dalam situasi dramatis dan tegang, sehingga penonton dapat memahami dan ikut terbawa untuk merasakan ketegangan yang terjadi pada adegan action kejarkejaran mobil maupun adegan kecelakaan. Teknik pergerakan kamera tilt dan crabbing justru cenderung dimotivasi dari ukuran gambar yang dekat seperti medium close up, medium shot, dan knee shot karena pada ukuran gambar tersebut memungkinkan penonton untuk melihat subjek secara lebih jelas, misalnya pada adegan action pertarungan dan penonton dapat menikmati secara jelas detail-detail seperti pukulan atau tendangan yang dilakukan pemain saat bertarung. Kata Kunci: pergerakan kamera, action, Fast and Furious 7, type of shot, camera angle, dramatis