Talks by Students and Others in Materials Engineering. Open to All.
Paper Critique- Advisor: Cory Leclerc
Treatment of textile effluents involves removal of suspended solids, reduction of biological oxygen demand, and removal of dyes and electrolytes. To date, separation methods such as flocculation, coagulation, oxidation, and biological treatments, have been employed to treat this wastewater. However, given the complexity of the wastewater, no single method can effectively remove all the chemicals and dyes that are present. Nanofiltration membrane filtration-based method that uses nanometer-sized through-pores that pass through the membrane has recently brought attention due to its ability to effectively remove dyes from large volumes of water at a low cost are considered to offer a preferable alternative. The critiqued paper title is “Fabrication of loose outer-selective nanofiltration (NF) polyethersulfone (PES) hollow fibers via single-step spinning process for dye removal.” This paper focused on fabrication of the nanofiltration through three
aspects including sulfonated polysulfone (sPSF) concentration, total polymer concentration, and the take-up speed. The objective of this paper was to obtain a valid, relatively stable performance NF hollow fiber membranes to treat dye wastewater. The newly developed NF membrane not only effectively remove indigo carmine with a rejection greater than 94.9%, but also sustain the high rejection during a 72-h continuous operation.
Dissertation Defense- Advisor: Dale Henneke
Thermoluminescent dosimeters (TLDs) are used for a variety of nuclear applications
but are most commonly used to characterize absorbed gamma dose at facilities across
the world. At White Sands Missile Range (WSMR) much of the testing relates to silicon
based devices. Manganese doped calcium fluoride (CaF2:Mn) is an ideal candidate for
such testing because its mass energy absorption coefficient closely matches that of
silicon while also having a linear absorbed dose response range from 1-150,000 cGy(TLD).
There are often a tradeoffs between cost, reusability, and accuracy. Tests using gamma
radiation and thermal annealing were conducted in an effort to improve on the accuracy
and methodology of reusing a CaF2:Mn TLDs. The results suggest that total absorbed
gamma dose is the primary cause of sensitivity loss of TLDs but thermal annealing
is a contributor. Theses effects likely relate to production of F-centers within the
material that degrade the transmittance of the visibily light emitted during the photoluminescent process of the TLD. There was no change to the crystal structure of the TLDs caused by routine thermal annealing or gamma radiation.
Thesis Defense- Advisor: Michaelann S. Tartis
Pancreatic cancer has a poor 5-year survival rate of <10%, with few treatment options: chemotherapy, radiation therapy, and surgery. These options rarely lead to remission and are aimed towards alleviating symptoms and extending survival. Localizing the delivery of treatments are showing positive symptom relief and tumor regressions, by minimizing exposure of therapeutic agents to the rest of the body. Lipid based carriers (liposomes, microbubbles, and nanodroplets) are gaining in popularity as drug delivery vehicles designed for triggered ultrasound deposition. Liposomes (therapeutically) and microbubbles (theranostically) are clinically available, whereas nanodroplets are still under development. These vehicles are designed to systemically circulate through the body with their ‘cargo’ until localized release is activated. Limitations and challenges lipid based carriers face include poor drug incorporation, solubility difficulties, and formulation issues. To improve upon lipid based targeted drug delivery techniques, a progressing trend to remodify therapeutic agents into prodrugs is exhibiting promising results. Prodrugs benefit drug delivery by providing drug release (prodrug activation by chemical or enzymatic hydrolysis), increasing chemical stability and solubility while reducing toxicity before metabolization begins. Incorporating prodrugs within lipid based carriers allows opportunity to utilize ultrasound for localized delivery. A phospholipid attachment strategy generating the prodrugs in this study, is intended to be applied to other well suited drugs varying in application. This work focuses on conjugating phospholipids onto podophyllotoxin (P) and its analogue (N) and characterizing the effects of their incorporation into lipid based drug delivery vehicles for triggered ultrasound delivery. Successfully synthesized lipophilic prodrugs, 2T-P and 2T-N, incorporate within the lipid membranes of liposomes, demonstrated by particle characterization techniques including differential scanning calorimetry (DSC), UV-vis spectroscopy, and dynamic light scattering (DLS). In addition, increased stability and incorporation are observed in 2T-P and 2T-N in comparison to parent compounds, P and N. The biological activity of 2T-N (IC50: 20 nM) was retained in HeLa cells (cervical cancer), whereas 2T-P (IC50: ~4 µM) activity decreased, thought to be caused by steric hindrance. Furthermore, in vitro microbubble ultrasound localized delivery studies establish a proof of concept that these prodrugs are capable of localized drug delivery. This study provides useful information about the synthesis of double tail analogues of insoluble chemotherapeutic agents to facilitate incorporation into drug delivery vehicles.
Thesis Proposal- Advisor: John McCoy
Coupled chemical and mechanical interactions can lead to leakage pathway development at cement-geomaterial interfaces, negatively impacting integrity of engineered cement barriers. We examine interactions, potential coupling, and pathways to failure in an observational, experimental and modeling study involving cement-clay, cement-salt, and cement-granite interfaces. A sample shotcrete-bentonite interface from the FEBEX heater test at the Grimsel Test Site in Switzerland, and a salt-cement interface from a mined-wellbore within a potash mine in southern New Mexico, are analyzed with micro-CT, multi-beam scanning electron microscopy, and electron X-ray dispersive spectroscopy at cm-to-nm length scales. We examine changes in alteration as manifested by pore structural changes and nanoindentation properties as a function of distance from the interface (bulk and shear modulus). A parallel effort examines interface evolution in controlled triaxial benchtop experiments which monitor cement-granite interface degradation in situ by acoustic and chemical methods, and post-experiment using nanoindentation. Initial results display evolving acoustic properties with time suggesting a mechanism for detecting interface alteration. Experimental results are being used in validating a coupled reactive-transport-mechanics model combining the ALBANY mechanics finite element code, the KAYENTA elasto-plastic constitutive model, and the PFLOTRAN reactive transport finite difference code. Future plans are to use the validated coupled chemo-mechanical model specifically in analyzing the spatio-temporal evolution of the shotcrete-bentonite and cement-salt samples, and in general as a predictive tool for assessment of cement barrier integrity.
Thesis Proposal- Advisor Bhaskar Majumdar
High Entropy Alloys (HEAs) are a new class of alloys that have 5 or more principal
components, associated with a large configurational entropy. The large configurational
entropy of these alloys tends to promote a single phase solid solution. As a result,
significant substitution strengthening and, due to the avoidance of intermetallic
compounds, reasonable ductility occurs. Additionally, it has been theorized that sluggish
diffusion may occur in the highly distorted lattice of HEAs resulting in low creep
rates. For these reasons, HEAs may be suitable for high temperature applications,
such as in aircraft turbines or nuclear power-plant components. Unfortunately, many
single phase HEAs that have acceptable levels of ductility at room temperature suffer
from low strength at elevated temperatures. There has been recent interest in developing
precipitation or dispersed second phases in a HEA matrix in order to improve high
temperature strength. Research shows that a hard second phase results in high strengths
at elevated temperatures. However, very little work has been done on creep resistance
capabilities of single phase or multi-phase HEAs. In addition, the high temperature
stability of these alloys with and without superimposed load needs to be established
to assess the long term high temperature performance. The goal of this work is an
initial attempt to address some of these deficiencies in the literature.
Keyword: HEA; Creep; Entropy
PhD paper critique - Adviser: John McCoy
In the communication, “Something about amber: Fictive temperature and glass transition temperature of extremely old glasses from copal to Triassic amber” Jing Zhao, Eugenio Ragazzi, and Gregory B. McKenna explore the thermal properties of highly aged amber. The authors the examine the thermal properties of 12 different amber and copal samples from different time periods and geographical locations using Differential Scanning Calorimetry in order to better determine the aging behavior of glassy polymers 40°C below their glass transition temperature (Tg). The authors also comment on the stability of amber samples and the relationship between copal and amber as well as how to distinguish between the two based on their thermal properties. Based on these results, the authors comment on the use of Tg as a means of identifying the age amber, the thermal properties of nominally identical amber, and the selection of stable amber samples for further research.
Zhao, J., E. Ragazzi, and G.B. McKenna, Something about amber: Fictive temperature and glass transition temperature of extremely old glasses from copal to Triassic amber. Polymer, 2013. 54(26): p. 7041-7047.