Matching Items (14)

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Protecting amphibians from a deadly Chytrid Fungus using a novel technology

Description

Infectious disease in wild animals has historically been a challenge that is difficult to overcome, primarily because isolating a disease outbreak to prevent further transmission in these types of populations

Infectious disease in wild animals has historically been a challenge that is difficult to overcome, primarily because isolating a disease outbreak to prevent further transmission in these types of populations is nearly impossible. Wild animals are free to roam, and humans often have limited means of tracking infection in populations. Vaccines and treatments can be formulated but are often somewhat impractical for wild populations because it is not feasible to vaccinate or treat every member in a susceptible community. One such pathogen, Batrochochytrium dendrobatidis (Bd) is infecting amphibian populations around the world to the point where many species are already extinct. Even though finding an effective preventative for the fungal pathogen may not mean that I am able to reach every member in a population, it may mean the difference between extinction and eventual release back into the wild for threatened populations.
In this study I hoped to create an attenuated version of Batrochochytrium dendrobatidis, by using a novel laser technology: SEPHODIS. This laser technology disrupts hydrogen bonds between proteins in the lumen of the cell while simultaneously preserving the membrane and associated proteins on the outside of the cell. This process ultimately affects the pathogenicity of the target but leaves identity markers intact so that the host immune system may recognize the pathogen and create antibodies against it. The laser was ultimately effective at killing Bd fungal cells, and I did observe a significant change in the appearance of the cells. However, samples obtained after exposure to the laser were contaminated and more research is needed to determine if SEPHODIS could be a feasible method for vaccine production.

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Created

Date Created
  • 2019-05

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The Inactivation of Pathogens in Contaminated Medications Via Selection Photonic Disinfection

Description

Each year the hospitals in the United States dispose of viable medications worth millions of dollars. These facilities are currently forced to do so not because the medications have expired,

Each year the hospitals in the United States dispose of viable medications worth millions of dollars. These facilities are currently forced to do so not because the medications have expired, or are no longer effective, but rather because to re-use any leftover medications would allow for the possibility of spreading disease. Once a medications sterile seal has been broken, any remaining contents of its container are considered potential pathogenic biohazards, and must be disposed of. The main objective of this thesis was to explore a potential alternative to simply discarding these lifesaving and often expensive leftover medications. The ultimate goal of this work is to establish a process by which excess drugs could be safely and effectively purified for re-use, subsequently cutting costs, and enhancing medication availability. Pseudomonas aeruginosa (P.a.) and Staphylococcus aureus (S.a) were cultured for their commonality in healthcare-associated infections (HAI's), and allowed to contaminate medication-like compounds. These bacterially inoculated solutions were meant to mimic the contaminated medications mentioned above and were then treated with a novel, physical means of pathogen inactivation named SElective PHOtonic DISinfection (SEPHODIS). Pathogen load reduction was determined through plate count assays both before and after exposure to the SEPHODIS system. structural preservation of medication was established through the use of infrared spectroscopy. The results of these experiments furthered the confidence of SEPHODIS as an efficient means of pathogen inactivation, while promoting promise of a real-world application in the form of medication purification.

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Date Created
  • 2018-05

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Characterization of Zika Virus Inactivated by Ultrashort Pulsed Laser as a Source for Vaccine Development

Description

The objective of this thesis was to determine whether Zika Virus (ZIKV) can be effectively inactivated by Selective Photonic Disinfection (SEPHODIS) and determine whether key proteins involved in the infection

The objective of this thesis was to determine whether Zika Virus (ZIKV) can be effectively inactivated by Selective Photonic Disinfection (SEPHODIS) and determine whether key proteins involved in the infection process are preserved, making SEPHODIS a possible source for vaccine development. As of January 2018, there have been 3,720 confirmed cases of Congenital Zika Syndrome in infants, making a Zika Vaccine a high priority (Mitchell, 2018). SEPHODIS is a process that involves prolonged exposure of an object to a pulsing laser which can render it ineffective. Initially, ZIKV was subjected to laser inactivation for 6 hours, then a plaque assay was performed on both laser-treated and control samples. ZIKV was inactivated two-fold? after laser treatment, when compared with control, as indicated by the plaque assay results. Additionally, both samples were submitted to ELISA to evaluate antigenicity with a panel of monoclonal and human sera. As a second control, virus inactivated by formaldehyde (2%) was used. ELISA results showed that antigenicity of some proteins were preserved while others were probably disturbed. However, ELISA results show that ZIKV envelope protein (E-protein), the protein responsible for viral entry into cells, was effectively preserved after laser-treatment, implying that if laser parameters were tweaked to obtain more complete inactivation, then SEPHODIS may be an appropriate source for the development of a vaccine.

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Created

Date Created
  • 2018-05

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Testing a novel method of viral inactivation of a lethal amphibian pathogen

Description

The amphibian pathogen Ambystoma Tigrinum Virus (ATV) has been an important topic of study within the amphibian community since its discovery. ATV threatens many salamander populations across the US, including

The amphibian pathogen Ambystoma Tigrinum Virus (ATV) has been an important topic of study within the amphibian community since its discovery. ATV threatens many salamander populations across the US, including those in east-central and southeast Arizona. These populations remain at risk since there are no treatments available. In this thesis, a novel method of inactivation is tested to produce a vaccine with the aim of safely eliciting an immune response within the salamander host. This novel form of inactivation has been tested on several human pathogens but has yet to be used on amphibian pathogens. It has the potential to revolutionize our traditional approach to inactivating viruses. After laser treatment, viral plaque assays suggested that inactivated ATV ceased to grow completely, pointing to the possibility of creating a vaccine. Animal challenge trials were conducted with 60 juvenile Ambystoma tigrinum, but surprisingly there was no protective effect from viral inactivation. Further study is needed to clarify why in vitro and in vivo tests of viral inactivation produced contradictory results.

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Created

Date Created
  • 2019-05

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Studies of inactivation mechanism of non-enveloped icosahedral virus by a visible ultrashort pulsed laser

Description

Background
Low-power ultrashort pulsed (USP) lasers operating at wavelengths of 425 nm and near infrared region have been shown to effectively inactivate viruses such as human immunodeficiency virus (HIV), M13

Background
Low-power ultrashort pulsed (USP) lasers operating at wavelengths of 425 nm and near infrared region have been shown to effectively inactivate viruses such as human immunodeficiency virus (HIV), M13 bacteriophage, and murine cytomegalovirus (MCMV). It was shown previously that non-enveloped, helical viruses such as M13 bacteriophage, were inactivated by a USP laser through an impulsive stimulated Raman scattering (ISRS) process. Recently, enveloped virus like MCMV has been shown to be inactivated by a USP laser via protein aggregation induced by an ISRS process. However, the inactivation mechanism for a clinically important class of viruses – non-enveloped, icosahedral viruses remains unknown.
Results and discussions
We have ruled out the following four possible inactivation mechanisms for non-enveloped, icosahedral viruses, namely, (1) inactivation due to ultraviolet C (UVC) photons produced by non-linear optical process of the intense, fundamental laser beam at 425 nm; (2) inactivation caused by thermal heating generated by the direct laser absorption/heating of the virion; (3) inactivation resulting from a one-photon absorption process via chromophores such as porphyrin molecules, or indicator dyes, potentially producing reactive oxygen or other species; (4) inactivation by the USP lasers in which the extremely intense laser pulse produces shock wave-like vibrations upon impact with the viral particle. We present data which support that the inactivation mechanism for non-enveloped, icosahedral viruses is the impulsive stimulated Raman scattering process. Real-time PCR experiments show that, within the amplicon size of 273 bp tested, there is no damage on the genome of MNV-1 caused by the USP laser irradiation.
Conclusion
We conclude that our model non-enveloped virus, MNV-1, is inactivated by the ISRS process. These studies provide fundamental knowledge on photon-virus interactions on femtosecond time scales. From the analysis of the transmission electron microscope (TEM) images of viral particles before and after USP laser irradiation, the locations of weak structural links on the capsid of MNV-1 were revealed. This important information will greatly aid our understanding of the structure of non-enveloped, icosahedral viruses. We envision that this non-invasive, efficient viral eradication method will find applications in the disinfection of pharmaceuticals, biologicals and blood products in the near future.

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Created

Date Created
  • 2014-02-05

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Inhibition of Escherichia coli respiratory enzymes by short visible femtosecond laser irradiation

Description

A visible femtosecond laser is shown to be capable of selectively inactivating a wide spectrum of microorganisms in a wavelength and pulse width dependent manner. However, the mechanism of how

A visible femtosecond laser is shown to be capable of selectively inactivating a wide spectrum of microorganisms in a wavelength and pulse width dependent manner. However, the mechanism of how a visible femtosecond laser affects the viability of different microorganisms is still elusive. In this paper, the cellular surface properties, membrane integrity and metabolic rate of Escherichia coli (E. coli) irradiated by a visible femtosecond laser (λ = 415 nm, pulse width = 100 fs) with different exposure times were investigated. Our results showed that femtosecond laser treatment for 60 min led to cytoplasmic leakage, protein aggregation and alternation of the physical properties of the E. coli cell membrane. In comparison, a 10 min exposure of bacteria to femtosecond laser irradiation induced an immediate reduction of 75% in the glucose-dependent respiratory rate, while the cytoplasmic leakage was not detected. Results from enzymatic assays showed that oxidases and dehydrogenases involved in the E. coli respiratory chain exhibited divergent susceptibility after laser irradiation. This early commencement of respiratory inhibition after a short irradiation is presumed to have a dominant effect on the early stage of bacteria inactivation.

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Agent

Created

Date Created
  • 2014-08-06

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Pathogen Reduction in Human Plasma Using an Ultrashort Pulsed Laser

Description

Pathogen reduction is a viable approach to ensure the continued safety of the blood supply against emerging pathogens. However, the currently licensed pathogen reduction techniques are ineffective against non-enveloped viruses

Pathogen reduction is a viable approach to ensure the continued safety of the blood supply against emerging pathogens. However, the currently licensed pathogen reduction techniques are ineffective against non-enveloped viruses such as hepatitis A virus, and they introduce chemicals with concerns of side effects which prevent their widespread use. In this report, we demonstrate the inactivation of both enveloped and non-enveloped viruses in human plasma using a novel chemical-free method, a visible ultrashort pulsed laser. We found that laser treatment resulted in 2-log, 1-log, and 3-log reductions in human immunodeficiency virus, hepatitis A virus, and murine cytomegalovirus in human plasma, respectively. Laser-treated plasma showed ≥70% retention for most coagulation factors tested. Furthermore, laser treatment did not alter the structure of a model coagulation factor, fibrinogen. Ultrashort pulsed lasers are a promising new method for chemical-free, broad-spectrum pathogen reduction in human plasma.

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Created

Date Created
  • 2014-11-05

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Optical characterization of III nitride semiconductors using cathodoluminescence techniques

Description

Group III-nitride semiconductors have attracted much attention for applications on high brightness light-emitting diodes (LEDs) and laser diodes (LDs) operating in the visible and ultra-violet spectral range using indium gallium

Group III-nitride semiconductors have attracted much attention for applications on high brightness light-emitting diodes (LEDs) and laser diodes (LDs) operating in the visible and ultra-violet spectral range using indium gallium nitride in the active layer. However, the device efficiency in the green to red range is limited by quantum-confined Stark effects resulting from the lattice mismatch between GaN and InGaN. In this dissertation, the optical and micro-structural properties of GaN-based light emitting structures have been analyzed and correlated by utilizing cathodoluminescence and transmission electron microscopy techniques. In the first section, optimization of the design of GaN-based lasers diode structures is presented. The thermal strain present in the GaN underlayer grown on sapphire substrates causes a strain-induced wavelength shift. The insertion of an InGaN waveguide mitigates the mismatch strain at the interface between the InGaN quantum well and the GaN quantum barrier. The second section of the thesis presents a study of the characteristics of thick non-polar m-plane InGaN films and of LED structures containing InGaN quantum wells, which minimize polarization-related electric fields. It is found that in some cases the in-plane piezoelectric fields can still occur due to the existence of misfit dislocations which break the continuity of the film. In the final section, the optical and structural properties of InGaAlN quaternary alloys are analyzed and correlated. The composition of the components of the film is accurately determined by Rutherford backscattering spectroscopy.

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Agent

Created

Date Created
  • 2011

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Andreev reflection spectroscopy: theory and experiment

Description

A theoretical study of a three-dimensional (3D) N/S interface with arbitrary spin

polarization and interface geometry is presented. The 3D model gives the same intrinsic

spin polarization and superconducting gap dependence as

A theoretical study of a three-dimensional (3D) N/S interface with arbitrary spin

polarization and interface geometry is presented. The 3D model gives the same intrinsic

spin polarization and superconducting gap dependence as the 1D model. This

demonstrates that the 1D model can be use to t 3D data.

Using this model, a Heusler alloy is investigated. Andreev reflection measurements

show that the spin polarization is 80% in samples sputtered on unheated MgO(100)

substrates and annealed at high temperatures. However, the spin polarization is

considerably smaller in samples deposited on heated substrates.

Ferromagnetic FexSi􀀀x alloys have been proposed as potential spin injectors into

silicon with a substantial spin polarization. Andreev Reflection Spectroscopy (ARS) is

utilized to determine the spin polarization of both amorphous and crystalline Fe65Si35

alloys. The amorphous phase has a significantly higher spin polarization than that of

the crystalline phase.

In this thesis, (1111) Fe SmO0:82F0:18FeAs and Pb superconductors are used to

measure the spin polarization of a highly spin-polarized material, La0:67Sr0:33MnO3.

Both materials yield the same intrinsic spin polarization, therefore, Fe-superconductors

can be used in ARS. Based on the behavior of the differential conductance for highly

spin polarized LSMO and small polarization of Au, it can be concluded that the Fe-Sc

is not a triplet superconductor.

Zero bias anomaly (ZBA), in point contact Andreev reflection (PCAR), has been

utilized as a characteristic feature to reveal many novel physics. Complexities at a

normal metal/superconducting interface often cause nonessential ZBA-like features,

which may be mistaken as ZBA. In this work, it is shown that an extrinsic ZBA,

which is due to the contact resistance, cannot be suppressed by a highly spin-polarized

current while a nonessential ZBA cannot be affected the contact resistance.

Finally, Cu/Cu multilayer GMR structures were fabricated and the GMR% measured

at 300 K and 4.5 K gave responses of 63% and 115% respectively. Not only

do the GMR structures have a large enhancement of resistance, but by applying an

external magnetic eld it is shown that, unlike most materials, the spin polarization

can be tuned to values of 0.386 to 0.415 from H = 0 kOe to H = 15 kOe.

Contributors

Agent

Created

Date Created
  • 2015

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Polarization effects in group III-nitride materials and devices

Description

Group III-nitride semiconductors have wide application in optoelectronic devices. Spontaneous and piezoelectric polarization effects have been found to be critical for electric and optical properties of group III-nitrides. In this

Group III-nitride semiconductors have wide application in optoelectronic devices. Spontaneous and piezoelectric polarization effects have been found to be critical for electric and optical properties of group III-nitrides. In this dissertation, firstly, the crystal orientation dependence of the polarization is calculated and in-plane polarization is revealed. The in-plane polarization is sensitive to the lateral characteristic dimension determined by the microstructure. Specific semi-polar plane growth is suggested for reducing quantum-confined Stark effect. The macroscopic electrostatic field from the polarization discontinuity in the heterostructures is discussed, b ased on that, the band diagram of InGaN/GaN quantum well/barrier and AlGaN/GaN heterojunction is obtained from the self-consistent solution of Schrodinger and Poisson equations. New device design such as triangular quantum well with the quenched polarization field is proposed. Electron holography in the transmission electron microscopy is used to examine the electrostatic potential under polarization effects. The measured potential energy profiles of heterostructure are compared with the band simulation, and evidences of two-dimensional hole gas (2DHG) in a wurtzite AlGaN/ AlN/ GaN superlattice, as well as quasi two-dimensional electron gas (2DEG) in a zinc-blende AlGaN/GaN are found. The large polarization discontinuity of AlN/GaN is the main source of the 2DHG of wurtzite nitrides, while the impurity introduced during the growth of AlGaN layer provides the donor states that to a great extent balance the free electrons in zinc-blende nitrides. It is also found that the quasi-2DEG concentration in zinc-blende AlGaN/GaN is about one order of magnitude lower than the wurtzite AlGaN/GaN, due to the absence of polarization. Finally, the InAlN/GaN lattice-matched epitaxy, which ideally has a zero piezoelectric polarization and strong spontaneous polarization, is experimentally studied. The breakdown in compositional homogeneity is triggered by threading dislocations with a screw component propagating from the GaN underlayer, which tend to open up into V-grooves at a certain thickness of the InxAl1-xN layer. The V-grooves coalesce at 200 nm and are filled with material that exhibits a significant drop in indium content and a broad luminescence peak. The structural breakdown is due to heterogeneous nucleation and growth at the facets of the V-grooves.

Contributors

Agent

Created

Date Created
  • 2012