LADCAP Ground TestingAllison E. Mundy and David J. Thomas, Ph.D.Science Division, Lyon College, 2300 Highland Rd. Batesville, AR 72501

Fatty Acid Relative Weight Percentages

Determination of Fatty Acid Concentrations in AlgaePayton Ashcraft, Randa Jacks, Blake Martinez, Jason Rodriguez, and Andrew Williams, Ph.D.

School of Mathematical and Natural Sciences, University of Arkansas at Monticello

Background

Algae are of scientific and

commercial interest due to their

ease of growth and content of

fatty acids and other lipids. It is

reasonable to assume that

different strains of algae will

contain different amounts of

varying fatty acids. The

objective was to determine the

types and amounts of the fatty

acids contained within certain

strains of algae in the class

Eustigmatophyceae. The

biochemical properties of the

algae were analyzed for

phylogenetic classification

purposes. Based on their fatty

acid content, a profile was

made of different strains of

algae using relative

percentages of fatty acids as

identifiers.

Methods

Fatty acid methyl esters were

extracted and analyzed from

the algal samples.

Acknowledgments

Funding for the project was provided

by NASA and the Arkansas Space

Grant Consortium. Great appreciation

goes to Marvin Fawley, Ph.D. and

Karen Fawley, Ph.D. for providing the

algae samples, and Lynn Fox,, Ph.D.

for statistical analysis. Special thanks

to the High Performance Structural

Mass Spectrometry Laboratory at the

University of Arkansas at Fayetteville

for assisting in the analysis of the

algae samples.

For more information, contact

williamsa@uamont.edu

Conclusions

Fatty acids within the algal strains

were extracted and identified.

New species of algae are being

discovered regularly, and fatty

acid content of the strains my be

useful in assigning them to their

existing phylogeny. Analyzing

algae strains has raised many

questions regarding fatty acid

synthesis and concentration

variations between strains. Two

algae strains were tested and

significant differences were found

between fatty acid

concentrations. Using these

statistics, a profile was created for

each of these algae strains with

these fatty acid differences acting

as identifiers.

Results

Results were analyzed using the

Related-Samples Friedman’s

Two-way Analysis of Variance by

Rank. This test was used to

compare all of the relative

percentages of fatty acids from

new and old observations in each

individual algae strain. A Post

Hoc (Pairwise Comparison) test

was used to determine the

significant differences between

pairs of fatty acids in each

strain. A Bonferroni adjustment

was included in the Post Hoc test

to avoid type 1 error. A graph

showing the node of the pairwise

comparison table was created.

Phylogenetic Analysis

LypholizationLipid

Extraction

FiltrationEsterification

FAME Extraction

GC-MS

0.00%

5.00%

10.00%

15.00%

20.00%

25.00%

30.00%

35.00%

40.00%

45.00%

C14:0 C16:1 C16:0 C18:2 C18:1 C18:0 C20:4 C20:5 C22:0

Tow 8/18 T-8d

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C14:0 C16:1 C16:0 C18:2 C18:1 C20:4

Bog D 8/9

Related-Samples Freidman’s Two-way

Analysis of Variance by Rank

Pairwise Comparisons

Tow 8/18 T-8d Bog D 8/9

Introduction Nitrite and nitrate are the major oxidative products of nitric

oxide (NO). However, in recent years, scientists have found that dietary nitrate can reduce blood pressure.

In previous study, we discovered that nitrate in vegetables can be reduced to nitrite by some enzymes or bacteria during storage. The intake of excess amount of nitrite is believed to cause increased risk of some cancers and methemoglobinemia in infants

Nitrate from diet such as vegetables is taken up by salivary glands and concentrated into saliva, where it can be converted to nitrite by anaerobic bacteria or enzyme (nitrate reductase), which is then converted to NO in blood and tissues.

Nitric Oxide (NO) has numerous important physiological functions in mammalian systems, including maintenance of normal blood flow and arterial pressure through its vasodilation action via Soluble Guanylyl Cyclase activation.

Vegetables with high nitrate contents will be the potential foods to treat and reduce high blood pressure.

ExperimentsSample Preparation: Approximately 80 grams each of store purchased celery and green cabbage was washed and blended with 200 ml DI water. The blended mixture was filtered using cheesecloth to remove solid residue. The solution volume was measured.

Human saliva catalyzing nitrite formation: 1) 4.5 ml celery juice + 4.5 ml DI water + 1.0 ml human saliva mixture; 2) 4.5 ml celery juice + 4.5 ml cabbage juice + 1.0 ml human saliva mixture; 3) control experiment was set up by mixing 4.5 ml celery juice + 5.5 ml DI water. All reaction mixtures were sit in a water bath at 37 ºC, taking out 1.0 ml sample from each reaction mixture every 30 minutes up to 3 hours and boil them at 100 ºC to stop the reaction. The boiled reaction mixture was then ready for the nitrite concentration measurement.

Nitrite concentration measurement (Griess assay ): 1.0 ml of 1% sulfanilamide solution (in 5% H3PO4)and 1.0 ml of 0.1% N-1-napthylethylenediamine (in DI H2O) were added to each boiled reaction mixture sample. After each addition of the solution, the samples were incubated at room temperature in the dark for 10 minutes. The absorbance was then read at 546 nm and compared to a standard curve to obtain the nitrite concentration.

Conclusions

•Human saliva contains bacteria with nitrate reductase (NaR), which can catalyze the formation of nitrite from nitrate in celery juice quickly within one hour at physiological temperature.

• NaR inhibitor, NaWO4, can completely inhibit the formation of nitrite in celery juice that catalyzed by human saliva, which confirmed that NaR was responsible for the formation of nitrite from nitrate in celery juice;

•Cabbage may contain inhibitor of NaR or NaR inhibitor protein (NIP),which inhibits the formation of nitrite from nitrate in celery juice.

Acknowledgements •Financial Support: Arkansas Space Grant Consortium (ASGC, UAM 29023). All saliva donors for this project are greatly appreciated.

Mechanism

* NaR: Nitrate Reductase

NaRNO3

- + 2H+ + 2e- NO2- + H2O

Dynamics and Mechanism of Human Saliva Catalyzing the Formation of Nitrite in Celery

Sara Claycomb, Justin Haney, and Jinming Huang

School of Mathematical and Natural Sciences, University of Arkansas at Monticello

Results

• Nitrite concentration in celery juice mixed with human saliva (male and female) increased very quickly with time (Black circles, Fig 1 and Fig 2);• Nitrite concentration increased much slower in the celery juice mixed with cabbage juice (1:1, volume ratio) and human saliva (Red triangles, Fig 1 and Fig 2); • No nitrite concentration increasing found in celery juice without saliva (Green square, Fig 1 and Fig 2);•No significant difference in nitrite concentration increasing with time found between male saliva and female saliva catalysis (Fig 1 and Fig 2);• Nitrate reductase (NaR) inhibitor, 5 M M NaWO4, can completely inhibit the formation of nitrite in celery juice that catalyzed by human saliva (Fig 3, pink square).

Fig 1. Formation of nitrite in celery catalyzed by female saliva (n= 7)

Time (hr)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

[Nitr

ite] (

uM)

-500

0

500

1000

1500

2000

Celery + female salivaCelery + cabbage + female salivaCelery juice

Fig 2. Formation of nitrite in celery catalyzed by male saliva (n= 7)

Time (hr)

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[Nitri

te] (u

M)

-200

0

200

400

600

800

1000

1200

1400

1600

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Celery + male salivaCelery + cabbage + male salivaCelery juice

Fig 3. The Effect of NaR Inhibitor on the Formation of Nitrite (n= 7)

Time (hr)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

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te] (u

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TEMPLATE DESIGN © 2008

www.PosterPresentations.com

Introduction Hypothesis Model

Extraterrestrial Probing of superconductivity in Metallic Hydrogen

David A. ClineDr. John Nichols

University of Arkansas at Little Rock, Department of Physics and Astronomy

These conditions are not extreme inside Jupiter, however, where pressures can easily exceed 500 GPa.

Earth’s magnetic field is relatively simple and can be expressed as a bar magnet’s field. The field goes uniformly from pole to pole.

Jupiter’s magnetic field, however, is rather peculiar. It comes out a region in the northern hemisphere and a large, abnormal amount returns in a region near the equator, leaving the remaining field to return through the southern hemisphere.

Dr. Neil Ashcroft predicted that metallic hydrogen would be a superconductor at room temperature. However it requires around 500 GPa (~5 Mbar/6,000,000 atm). It is immensely difficult to achieve these pressures, even with the use of diamond anvils, which usually fail around 400 GPa.

A team at Harvard reportedly managed to get to 495 GPa by removing defects in the diamonds, coating them in aluminum oxide, and minimalizing thermal stress. No experimentation was done to determine the superconductivity, however, due to the extreme conditions.

Superconductors are known to be perfect diamagnets, meaning that they are repelled by an external magnetic field. This also means that they do not allow the field to penetrate the superconductive regions. This is achieved via an induced magnetic field that is in the opposite direction of the external field.

As evident by the inset in the figure below, the metallic hydrogen can achieve superconductivity without having to be at exactly 5 Mbar due to the temperature of that region being capable of supplying the remaining required energy.

Knowing this, and that Jupiter has an antisymmetric dynamo, we are able to work on a model to assist in the interpretation of the magnetometer data gathered by the Juno spacecraft.

Credits:• Moore, K.M., Yadav, R.K., Kulowski, L. et al. A complex dynamo inferred from the

hemispheric dichotomy of Jupiter’s magnetic field. Nature 561, 76–78 (2018). https://doi.org/10.1038/s41586-018-0468-5

• Dietrich, W. & Jones, C. A. Anelastic spherical dynamos with radially variable electrical conductivity. Icarus 305, 15–32 (2018).

• French, M. et al. Ab initio simulations for material properties along the Jupiter adiabat. Astrophys. J. Suppl. Ser. 202, 5 (2012).

• Burnley, Pamela C. The heart of a diamond anvil cell. 2018, University of Nevada, Las Vegas. serc.carleton.edu/NAGTWorkshops/mineralogy/mineral_physics/diamond_anvil.html.

• Nave, Carl R. Mearthbar. . Georgia State University, Atlanta. hyperphysics.phy-astr.gsu.edu/hbase/magnetic/MagEarth.html#c1.

ConclusionBefore the first root and between the roots, our approximation does a good job of calculating Laguerre polynomials, however as 𝑥𝑥 gets larger. After the last root, our approximation tends to deviate more from the value of the true value of the Laguerre polynomial.

Assuming that we have know the zeros of a given Laguerre polynomial, the slope or derivative at the zeros, and the y intercept and the slope there, then we have three cases: the function before the first root, the function in between two roots, and the function after the last root. Let 𝐿𝐿𝑛𝑛𝑘𝑘 be a polynomial with roots 𝑥𝑥1, 𝑥𝑥2, … , 𝑥𝑥𝑛𝑛 .

In between two roots:We will use a cubic function of the form

𝑓𝑓𝑚𝑚 𝑥𝑥 = 𝑥𝑥 − 𝑥𝑥𝑚𝑚 𝑥𝑥 − 𝑥𝑥𝑚𝑚+1 𝑎𝑎𝑥𝑥 + 𝑏𝑏to approximate 𝐿𝐿𝑛𝑛𝑘𝑘 between two consecutive

roots 𝑥𝑥𝑚𝑚 and 𝑥𝑥𝑚𝑚+1 such that 𝑥𝑥𝑚𝑚 < 𝑥𝑥𝑚𝑚+1. To find the coefficient 𝑎𝑎, we take 𝑓𝑓𝑓𝑚𝑚 𝑥𝑥𝑚𝑚 and 𝑓𝑓′𝑚𝑚 𝑥𝑥𝑚𝑚+1 and set them equal to 𝐿𝐿𝑛𝑛𝑘𝑘 𝑓(𝑥𝑥𝑚𝑚) and 𝐿𝐿𝑛𝑛𝑘𝑘

′ 𝑥𝑥𝑚𝑚+1 respectfully. Then, after some algebra we find

𝑎𝑎 =𝐿𝐿𝑛𝑛𝑘𝑘

′ 𝑥𝑥𝑚𝑚 + 𝐿𝐿𝑛𝑛𝑘𝑘 𝑓(𝑥𝑥𝑚𝑚+1)(𝑥𝑥𝑚𝑚+1 − 𝑥𝑥𝑚𝑚)2

and

𝑏𝑏 =−𝐿𝐿𝑛𝑛𝑘𝑘 𝑓(𝑥𝑥𝑚𝑚)

(𝑥𝑥𝑚𝑚+1 − 𝑥𝑥𝑚𝑚)− 𝑎𝑎𝑥𝑥𝑚𝑚

Methods

Approximating Laguerre Polynomials

ExampleI created code using Mathematica to approximate an associated Laguerre polynomial for any 𝑛𝑛 and 𝑘𝑘 value. The following shows the polynomial 𝐿𝐿51 in orange and our approximation in blue.

Emily Freeman and Todd Tinsley

MotivationThe neutralino is a hypothetical particle and is a leading candidate for dark matter. Interactions with charged particles in supernova could be a possible method of detection. Calculating the likelihood of these interactions is difficult because it involves calculating associated Laguerre polynomials with large degrees.

BackgroundAssociated Laguerre polynomials are solutions to the second order differential equation:

𝑥𝑥𝑥𝑥′′ + 𝑘𝑘 + 1 − 𝑥𝑥 𝑥𝑥𝑓 + 𝑛𝑛𝑥𝑥 = 0. They are given explicitly by the formula:

𝐿𝐿𝑛𝑛𝑘𝑘 = �𝑚𝑚=0

𝑛𝑛

(−1)𝑚𝑚𝑛𝑛 + 𝑘𝑘 !

𝑛𝑛 − 𝑚𝑚 ! 𝑘𝑘 + 𝑚𝑚 !𝑚𝑚!𝑥𝑥𝑚𝑚

In Dr. Tinsley’s lab the Fortran program was calculating the Laguerre polynomials using this formula. However, this method was not working well when 𝑛𝑛 and 𝑘𝑘 were large. So, we decided to find a new way to calculate these polynomials which uses the roots and the slope at each root to fit a function in between the roots.

Hendrix College

Medicinal BiomoleculesChromatography

Extraction and Analysis of Medicinal Biomolecules in Witch HazelA. Glover, L. Taylor, L. Van Dee, A. Williams, Ph.D.

School of Mathematical and Natural Sciences, University of Arkansas at Monticello

Background Methods

Acknowledgments

Funding for the project was provided

by NASA and the Arkansas Space

Grant Consortium.

For more information, contact

williamsa@uamont.edu

References

Apparatus

Witch hazel (Hamamelis

virginiana) is native to eastern

North America and is a small

shrub or tree found growing in

bunches all over the United

States. It is most commonly

known for its use on skin irritants

and commercially used in

dermatological topical agents.

Because it is readily available

and biologically active, we want

to extract and analyze these

compounds and determine their

quantities. Once this data has

been analyzed, we will begin

more studies on their medicinal

functions and practicality. The

biologically active molecules in

Witch hazel can be extracted in

aqueous solution. We also want

to determine how Witch hazel

responds to low gravity

situations. The medicinal

biomolecules found in Witch

hazel will possibly be a safe and

green method to improve

astronaut health.

Witch hazel samples were

collected in Bradley County,

AR and stored in the freezer

overnight. Samples were

separated into bark, wood,

woody fruit, and fruit buds,

and placed into a thimble. To

set up our apparatus, we

used a Soxhlet extractor and

condensing tube. We placed

a round bottom flask with

distilled water on a heating

mantle and boiled for

approximately 24 hours.

Dichloromethane was used

as a solvent.

Tannins are water soluble polyphenols

found in many plants. Tannins are

responsible for a wide variety of effects

ranging from antimicrobial and

anticarcinogenic to reducing blood

pressure and accelerating blood

clotting1. Hamamelitannin (2′,5-di-O-

galloyl-D-hamamelose) is one of the

hydrolysable tannins found in Witch

hazel. Hamamelitannin is reported to

have specific cytotoxicity to colon

cancer cells2, increase antibiotic

susceptibility of Staphylococcus

aureus biofilms3, and inhibit the tumor

necrosis factor alpha-mediated

endothelial cell death and DNA

fragmentation in a dose dependent

manner4. Hamamelitannin is of interest

due to its potential medicinal qualities.

Current Analysis

Many peaks have been identified via GC-MS. Potential

biomolecules correlating with the peaks have been suggested by

the associated mass spec library. We took the suggested

biomolecules, and reviewed possible medicinal properties.

[1] K. T. Chung, T. Y. Wong, C. I. Wei, Y. W. Huang, Y. Lin, Crit. Rev. Food

Sci. Nutr., 38 (1998) 421-464.

[2] S. Sanchez-Tena, M. L. Fernandez-Cachon, A. Carreras, M. L. Mateos-

Martin, N. Costoya, M. P. Moyer, M. J. Nunez, J. L. Torres, M. Cascante, J.

Nat. Prod. 75 (2012) 26-33.

[3] G. Brackman, K. Breyne, R. D. Rycke, A. Vermote, F. V. Nieuwerburgh,

E. Meyer, S. V. Calenbergh, T. Coenye, Scientific Reports 6 (2016) 1-14

[4] S. Habtemariam, Toxicon 40 (2002) 83-88

Picture 2. Soxhlet apparatus Picture 1. Hamamelis virginiana

Figure 1. Wood with no bark.

GC-MS – spectra obtained from Harding University in Searcy, AR.

Figure 3. Fruit buds.

GC-SH-Rxi-5Sil MS Column, 0.25 um thickness, 0.25 mm diameter, 30.0 m length.

Oven Temp 60.0 °C, Injection Temp 280 ° C. Pressure at 65.2 kPa, Total Flow 11.9

mL/min, Column Flow 1.10 mL/min.

MS- Ion Source Temp: 250 ° C, Interface Temp: 250 ° C, Solvent Cut Time 1.9 min..

Figure 2. Woody Fruit.

Figure 4. Bark.

Figure 5. Store Bought.

Metal Oxide Nanostructures via Hot Water Treatment to Purify Water for Space Travel

Ranjitha Hariharalakshmanan and Tansel Karabacak

Department of Physics & Astronomy , University of Arkansas at Little Rock

Methods

Figure 6 : Degradation of methylene blue under UV light in the presence of ZnO nanostructured photocatalyst and its analysis using UV-Vis spectrophotometry

Characterization of ZnO nanostructures

Figure 7 (a) : concentration of methylene blue decreased in the presence of nanostructured ZnO photocatalyst

Figure 7 (b) : No significant change in the concentration of methylene blue in the absence of nanostructured ZnO photocatalyst

AbstractThe water treatment system in the International Space Station (ISS) recycles its own wastewater into potable water. One of the challenges faced by the current system is the removal of certain organic molecules such as DMSD, originating from personal hygiene products. Recently, semiconductor photocatalysis has received significant attention for the application of water purification. It is a process in which semiconducting materials absorb light and produce highly reactive free radicals called reactive oxygen species (ROS). ROS can degrade organic molecules to less-toxic products. Nanostructures of metal oxides such as TiO2 and ZnO have shown excellent photocatalytic activity, however, their synthesis is often costly, complicated and harmful to the environment. In this work, we present a novel hot water treatment (HWT) method to synthesize metal oxide nanostructures for photocatalytic water treatment, in a simple, low-cost, ecofriendly and scalable way. Here we discuss the synthesis of ZnO nanostructures by HWT and the photocatalytic performance of the same via organic dye degradation tests. Our results indicate that HWT nanostructures could be promising photocatalysts for water purification during space travel.

IntroductionHot water treatment (HWT)HWT is a one-step, low-cost, eco-friendly, and scalable nanostructure growth method. By HWT, various metal oxide nanostructures can be produced simply by the interaction of metals with hot water without the need for any chemical additives.

Advantages of nanostructured photocatalyst• High surface area• Enhanced light trapping and charge separation efficiency

Results

Conclusions • We obtained 65% decrease in the concentration of methylene blue when

it was exposed to UV light along with the nanostructured ZnO photocatalyst

• We did not observe any decrease in concentration when methylene blue alone was exposed to UV light

• These preliminary results indicate that HWT method presents a simple, cost-effective, scalable, and eco–friendly method for the synthesis of metal oxide nanostructures for photocatalytic water treatment during space travel.

References1) Saadi, N. S., Hassan, L. B., & Karabacak, T. (2017). Metal oxide nanostructures by

a simple hot water treatment. Scientific reports, 7(1), 7158. 2) Zhou, Qiong et al. “Synthesis of Vertically-Aligned Zinc Oxide Nanowires and Their

Application as a Photocatalyst.” Nanomaterials (Basel, Switzerland) vol. 7,1 9.11Jan. 2017

3) Fresno, Fernando & Portela, Raquel & Suárez, Silvia & Coronado, Juan. (2014). Photocatalytic materials: Recent achievements and near future trends. Journal of Materials Chemistry. 2. 2863. 10.1039/C3TA13793G

Figure 4 : SEM images of ZnO nanostructured powder produced after HWT

AcknowledgmentThe authors thank the Center for Integrative Nanotechnology Sciences at UA Little rock for their help with SEM images.

The mechanism of metal oxide photocatalysis

Figure 1: HWT method

Beer- Lambert law

A = ɛCl

A = Absorbanceɛ = Molar absorptivityC = Concentration l = Length of the cuvette

Figure 2 : Synthesis of ZnO nanostructures by hot water treatment

Figure 3 : SEM images of Zinc plate before and after HWT

Figure 5 : XRD of ZnO nanostructured powder produced after HWT

The Effects of Temperature in Photocatalytic Reactivity throughout Thermal/Ultraviolet Oxidation Processes and its Contribution to Dimethylsilanediol (DMSD) Reduction at Low Concentrations

Experimental Methods and Approach

Results and DiscussionIntroduction

Conclusion

Figure 1. Experimental apparatus designed to control the temperature, mass, and UV exposure of each DMSD sample

Previous experiments at Harding University already prove that the ultraviolet LEDs break down DMSD at a linear rate. The goal of this experiment is to show how temperature alters that linear curve. The approach is to create an apparatus that will hold the DMSD samples at a constant temperature as well as keep the mass of the sample constant. The following experimental setup, Figure 1, shows how the DMSD will be tested. The setup incorporates a double boiler that indirectly heats the sample, a condenser, and a digital hotplate that stirs the sample and reads/controls the temperature of the samples. Six DMSD samples will be exposed to the Ultraviolet radiation for a minimum of six hours, each being held at a different temperature. The DMSD concentration of the samples were measured to be 106 ppm before the experiment. The DMSD stock was approximated:

52.1𝑥𝑥40

= 132 mg DMSD (1)Every 60 minutes, a secondary sample from the apparatus will be taken and the temperature will be recorded. These secondary samples will be kept in ## and run through the Chromatograph to precisely measure the final concentration of DMSD after UV exposure.

Based on the mechanistic models for other solar based water disinfection processes3, reactions by solar or UV radiation accelerate with an increase in temperature of the reactants due to higher reactive oxygen species and a higher probability of kinetic interactions. Studies of bacterial UV disinfection suggest that DMSD will follow the synergistic model shown in Figure 2 that the reactivity improves with moderate to substantial temperature increase. Figure 2 presents how the results of this experiment should behave in a 6-hour trial of 6 different temperature series. The expected trend should follow the following equations:

𝑦𝑦 = 𝐴𝐴𝑡𝑡2 − 𝐵𝐵𝑡𝑡 + 106 (2)𝐴𝐴 = 0.001𝑥𝑥2 − 0.039 (3)

𝐵𝐵 = −0.0002𝑥𝑥3 + 0.0438𝑥𝑥2 − 1.8𝑥𝑥 + 26.733 (4)

We can expect the reduction of DMSD to behave this way assuming an initially linear trend followed by an exponential decay. The parameters A and B that control this behavior, as seen in Figure 3, suggest that disinfection will continue to increase with respect to temperature until the rate of decay approaches a limit within the constant UV energy capacity of the LEDs.

Using an apparatus that maintains a homogeneous environment, excluding temperature as the the only altered variable, this experiment was conducted to observe how temperature changes the rate of DMSD reduction under Ultraviolet exposure. This study suggests that temperature will likely contribute to the photocatalytic reaction by increasing the rate at which the contaminant decays. The experiment is expected to exhibit the characteristics represented by current mechanistic modeling.

-20

0

20

40

60

80

100

120

0 1 2 3 4 5 6

DMSD

Con

cent

ratio

n (P

PM)

Time (Hours)

30 40 50 65 75 90Temperature (°C)

Low concentrations of Dimethylsilanediol (DMSD), an organosilicon compound present in humidity and moisture aboard the International Space Station (ISS), results when similar compounds are added to water. The resident water processing systems do not effectively remove DMSD compounds under the current concentration levels¹. However, current research at Harding University suggests that Thermal/Ultraviolet (UVLED) Oxidation and Hydroxide (OH) production could provide a sustainable solution to removing low concentrations of DMSD under the known conditions. This experiment investigates how temperature affects the photocatalytic reduction of DMSD and most likely improves reactivity with increasing temperature.

Matthew Hernandez Engineering & Physics Dept. at Harding University, Searcy, AR

-100

1020304050

20 40 60 80 100Para

met

er C

onst

ant

Temperature (°C)Paramter A Parameter B

Figure 3. Quadratic Modeling of DMSD Reduction

Figure 2. Mechanistic Model of Dimethylsilendiol (DMSD) undergoing Photocatalytic Reaction through Ultraviolet Exposure at Various Temperatures

With the measured results, the next step is to seek the optimal temperature at which DMSD reacts and model the reduction rate to later apply in the overall water purification system being designed at Harding University.

Further Research

AcknowledgmentsThis study was funded by the NASA Arkansas Space Grant Consortium.

Supervisors: Dr. Jeffery Massey, Harding University, Professor of Engineering & PhysicsDr. Dennis Province, UAMS, Professor of ChemistryDr. Jon White, Harding University, Professor of Electrical and Computer Engineering

Peer-Reviewed Article references: ¹Carter, L., Muirhead, D. L., “Dimethylsilanediol (DMSD) Source Assessment and Mitigation on ISS: Estimated Contributions from Personal Hygiene Products Containing Volatile Methyl Siloxanes (VMS)”, ICES-2018-123, , 48th International Conference on Environmental Systems, Albuquerque, New Mexico, 2018. 2Schultz, John, et al. “Discovery and Identification of Dimethylsilanediol as a Contaminant in ISS Potable Water.” American Institute of Aeronautics and Astronautics, 2011, doi:10.2514/6.2011-5154.3M. Castro-Alférez, M.I. Polo-López, J. Marugán, P.F. Ibáñez, “Mechanistic modeling of UV and mild-heat synergistic effect on solar water disinfection” Chemical Engineering Journal, Almaría, Spain, 2017. 4Schultz, John, et al. “Discovery and Identification of Dimethylsilanediol as a Contaminant in ISS Potable Water.” American Institute of Aeronautics and Astronautics, 2011, doi:10.2514/6.2011-5154.5“Specifications for Nichia UV LED”, Model NSHU591B, Nichia Corporation

BackgroundAs NASA begins its mission to Mars, it has become

highly necessary to ensure the ability of the closedwater system of International Space Station (ISS) toprevent an overwhelming microbial load and biofilmformation (Fig 1),1 and a cheap and effective solution“is critical due to the anticipated extension in missionlength, limited detection abilities, and known detrimentof the astronaut immune system.”2

Figure 1. Biofilm formation occurs in a number of steps, including attachment, proliferation and formation of the extra polymeric substances (EPS), and then detachment and reattachment at

another location.

Since titanium surfaces have exhibited antimicrobialand photocatalytic abilities to prevent biofilmformation,3 we previously found that heat-treatingtitanium by heating over a Meker burner andsubmerging the surface after turning an orange color inwater (Fig 2a) increased its photocatalytic ability byproducing reactive oxygen species (ROS) (Fig 2b),which can damage the cell wall, organelles, and DNA,possibly leading to death.

Heat-treated Titanium Surfaces Exhibit Antimicrobial Properties Rachel Palmer, Emory Malone, Dennis Province Ph.D. and Cindy White Ph.D.

Department of Chemistry and Biochemistry, Harding University, Searcy, AR

References

Results

AcknowledgementsWe thank Harding University Department of Chemistry and Biochemistry for funding this research and providing the facilities used. I also thank others helping me on this project, including Dr. David Donley, Sidney Brandon, Hannah Hefley, and Dakota Ungerbuehler.

1. Be, N. A.; Avila-Herrera, A.; Allen, J. E.; Singh, N.; Checinska Sielaff, A.; Jaing, C.; Venkateswaran, K. Whole Metagenome Profiles of Particulates Collected from the International Space Station. Microbiome2017, 5 (1), 81. https://doi.org/10.1186/s40168-017-0292-4.

2. Diaz, A. M.; Li, W.; Irwin, T. D.; Calle, L. M.; Callahan, M. R. Investigation of Biofilm Formation and Control for Spacecraft - An Early Literature Review; Boston, Massachusetts, 2019.

3. Xiao, X.; Zhu, W.-W.; Liu, Q.-Y.; Yuan, H.; Li, W.-W.; Wu, L.-J.; Li, Q.; Yu, H.-Q. Impairment of Biofilm Formation by TiO 2 Photocatalysis through Quorum Quenching. Environ. Sci. Technol. 2016, 50 (21), 11895–11902. https://doi.org/10.1021/acs.est.6b03134.

4. O’Toole, G. A. Microtiter Dish Biofilm Formation Assay. JoVE 2011, No. 47, 2437. https://doi.org/10.3791/2437.

5. Beenken, K. E.; Blevins, J. S.; Smeltzer, M. S. Mutation of SarA in Staphylococcus Aureus Limits Biofilm Formation. IAI 2003, 71 (7), 4206–4211. https://doi.org/10.1128/IAI.71.7.4206-4211.2003.

Future Directions

Figure 4. The growth curves ofE. coli after 6 hours of treatmentwith either no UV irradiation andan untreated titanium surface(a) or heat-treated titaniumsurface (b), or UV irradiationand an untreated titaniumsurface (c) or heat-treatedtitanium surface (d).

Methods

Conclusions

Figure 5. The means of the growth rates were significantly different (F3,92 = 46.67, p < 2e-16). Only significant differences between the irradiated and non-irradiated surfaces (p < 0.001) (a). The means of the OD after exposure to the surfaces for about 6 hours was different (F3,92 = 69.85, p < 2e-16). All the treatments were significantly different from one another (p < 0.05) (b).There is a significant difference in the means of the time of maximal proliferation due to treatment (F3,92 = 768.1, p < 2e-16). All treatments were significantly different except between the two irradiated surfaces (p = 0.95) (c).

Next, more focus will be allocated to the underlying biochemical mechanisms by analyzing ATP production on a SeaHorse and finding the time-dependent manner of bacterial kill by a LIVE/DEAD assay and flow cytometry. In addition, scanning electron microscopy (SEM) may be used to visualize the bactericidal and bacteriostatic effects on the cell wall.

a b

c d

a b

ca b

Figure 2. Heat-treatment of the titanium surfaces over a Meker burner (a) and generation of a hydroxyl radical via photocatalysis and generation of electron hole (h+) (b).

The microtiter dish assay protocol (Fig 3) was adapted from O’Toole et al.4 and Beenken et al.5 protocol for assessing biofilm growth and is shown in Figure 1 to the left. First a stock culture of E. coli was inoculated in fresh tryptic soy broth (TSB), which promotes bacterial growth and incubated overnight at 37°C. In the morning, 9 ml of a 1:200 dilution of the inoculum into fresh TSB was pipetted into each well plate of two different 6-well plates. In addition, half of the wells in each well plate contained either a heat-treated titanium surface or an untreated titanium surface. On plate was exposed to UV irradiation (365 nm) while the other was not. After about 6 hr of exposure, 200 μl samples were pipetted from each well of the 6-well plates into a 96-well plate, and an absorbance (600 nm) was taken in a plate reader. Then, the plate was incubated overnight (37°C ) in the plate reader while an absorbance (600 nm) was taken every 5 minutes to establish a growth curve (Fig 2). Analysis of the growth curves was conducted using the growthcurver package in RStudio. Values from the growth curve, including generation time, the time of maximal proliferation, carrying capacity, and growth rate were statistically analyzed on RStudio as well and plotted using Seaborn on Python.

The K12 Escherichia coli strain was bought from Carolina.Titanium surfaces were given from our partners at Universityof Arkansas in Little Rock (UALR) for antimicrobial analysis. AThorlabs Optical Power and Energy Meter was used tomeasure the intensity of the UV (365 nm) lamp (~0.60mW/cm2).

Figure 3. Antimicrobial assessment of heat-treated versus untreated titanium surfaces based on adapted protocols from O’Toole et al.4 and Beenken et al.5 by analyzing growth curves after exposure to titanium and/or UV irradiation (365 nm).

The absorbances taken directly after treatment indicated that the heat-treated titanium sheets were more bactericidal than the untreated titanium sheets (Fig 5b). UV irradiation will delay microbial growth both on the individual cellular level (Fig 5b) as well as during the exponential phase of biofilm formation (Fig 5c). Overall, this illustrates that heat-treating the titanium surfaces in the closed water system of the ISS may be an effective, cheap, and simple solution to aid in maintaining the microbial load in the closed water system of the ISS.