Name: sandy soil improvement through microbially induced calcite precipitation (micp) by immersion
Uploaded: 2019-09-12T14:30:00
Description: Watch this Scientific Journal Video about Sandy Soil Improvement through Microbially Induced Calcite Precipitation MICP by Immersion at JoVE.com

This work was supported by the National Science Foundation Grant No. 1531382 and MarTREC.

NOTE: All relevant material used in the following procedures are non-hazardous. Personal protective equipment (safety glasses, gloves, lab coat, full length pants, closed-toe shoes) are still needed.
1. Preparation of bacteria solution
<ol>
	<li>Preparation of growth medium (NH4-YE medium) 
	NOTE: The components of growth media per liter of deionized water are: 20 g of yeast extract; 10 g of (NH4)2SO4; and 0.13 M Tris buffer (pH 9.0).
	<ol>
		...

<ol>
	<li>Cheng, L., Shahin, M. A., Mujah, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+key+environmental+conditions+on+microbially+induced+cementation+for+soil+stabilization.">Influence of key environmental conditions on microbially induced cementation for soil stabilization.</a> Journal of Geotechnical and Geoenvironmental Engineering. 143 (1), 04016083-04016091 (2016).</li><li>Whiffin, V. S., van Paassen, L. A., Harkes, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microbial+carbonate+precipitation+as+a+soil+improvement+technique.">Microbial carbonate precipitation as a soil improvement technique.</a> Geomicrobiology Journal. 24 (5), 417-423 (2007).</li><li>van Paassen, L. A., Ghose, R., van der Linden, T. J., van der Star, W. R., van Loosdrecht, M. 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B., N&#252;sslein, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microbially+induced+cementation+to+control+sand+response+to+undrained+shear.">Microbially induced cementation to control sand response to undrained shear.</a> Journal of Geotechnical and Geoenvironmental Engineering. 132 (11), 1381-1392 (2006).</li><li>Zhao, Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Factors+affecting+improvement+of+engineering+properties+of+MICP-treated+soil+catalyzed+by+bacteria+and+urease.">Factors affecting improvement of engineering properties of MICP-treated soil catalyzed by bacteria and urease.</a> Journal of Materials in Civil Engineering. 26 (12), 04014094 (2014).</li><li>Castanier, S., Le M&#233;tayer-Levrel, G., Perthuisot, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ca-carbonates+precipitation+and+limestone+genesis&#8212;the+microbiogeologist+point+of+view.">Ca-carbonates precipitation and limestone genesis&#8212;the microbiogeologist point of view.</a> Sedimentary Geology. 126 (1-4), 9-23 (1999).</li><li>Burne, R. A., Chen, Y. Y. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacterial+ureases+in+infectious+diseases.">Bacterial ureases in infectious diseases.</a> Microbes and Infection. 2 (5), 533-542 (2000).</li><li>Bernardi, D., DeJong, J. T., Montoya, B. M., Martinez, B. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bio-bricks:+biologically+cemented+sandstone+bricks.">Bio-bricks: biologically cemented sandstone bricks.</a> Construction and Building Materials. 55, 462-469 (2014).</li><li>Li, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+fiber+addition+on+mechanical+properties+of+MICP-treated+sand.">Influence of fiber addition on mechanical properties of MICP-treated sand.</a> Journal of Materials in Civil Engineering. 28 (4), 04015166 (2015).</li><li>Achal, V., Kawasaki, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biogrout:+a+novel+binding+material+for+soil+improvement+and+concrete+repair.">Biogrout: a novel binding material for soil improvement and concrete repair.</a> Frontiers in Microbiology. 7, 314 (2016).</li><li>Al Qabany, A., Soga, K., Santamarina, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Factors+affecting+efficiency+of+microbially+induced+calcite+precipitation.">Factors affecting efficiency of microbially induced calcite precipitation.</a> Journal of Geotechnical and Geoenvironmental Engineering. 138 (8), 992-1001 (2011).</li><li>Lin, H., Suleiman, M. T., Brown, D. G., Kavazanjian, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+behavior+of+sands+treated+by+microbially+induced+carbonate+precipitation.">Mechanical behavior of sands treated by microbially induced carbonate precipitation.</a> Journal of Geotechnical and Geoenvironmental Engineering. 142 (2), 04015066 (2015).</li><li>Lauchnor, E. G., Topp, D. M., Parker, A. E., Gerlach, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Whole+cell+kinetics+of+ureolysis+by+sporosarcina+pasteurii.">Whole cell kinetics of ureolysis by sporosarcina pasteurii.</a> Journal of Applied Microbiology. 118 (6), 1321-1332 (2015).</li><li>Nafisi, A., Montoya, B. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+framework+for+identifying+cementation+level+of+MICP-treated+sands.">A new framework for identifying cementation level of MICP-treated sands.</a> IFCEE. , (2018).</li><li>Zhao, Q., Li, L., Li, C., Zhang, H., Amini, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+full+contact+flexible+mold+for+preparing+samples+based+on+microbial-induced+calcite+precipitation+technology.">A full contact flexible mold for preparing samples based on microbial-induced calcite precipitation technology.</a> Geotechnical Testing Journal. 37 (5), 917-921 (2014).</li><li>Bu, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+Rigid+Full-Contact+Mold+for+Preparing+Biobeams+through+Microbial-Induced+Calcite+Precipitation.">Development of a Rigid Full-Contact Mold for Preparing Biobeams through Microbial-Induced Calcite Precipitation.</a> Geotechnical Testing Journal. 42 (3), 656-669 (2018).</li><li>Li, M., Wen, K., Li, Y., Zhu, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+oxygen+availability+on+microbially+induced+calcite+precipitation+(MICP)+treatment.">Impact of oxygen availability on microbially induced calcite precipitation (MICP) treatment.</a> Geomicrobiology Journal. 35 (1), 15-22 (2018).</li><li>Martinez, B. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+optimization+of+microbial-induced+carbonate+precipitation+for+soil+improvement.">Experimental optimization of microbial-induced carbonate precipitation for soil improvement.</a> Journal of Geotechnical and Geoenvironmental Engineering. 139 (4), 587-598 (2013).</li></ol>

The MICP technique by immersion was presented in this paper. Soil samples were immersed into the batch reactor to get fully penetrated by cementation media in the MICP process. In this method, a full contact flexible mold, a rigid full contact mold, and a cored brick mold were applied to prepare MICP-treated samples.
Different molds can be designed for different geometry requirements. The fibrous structure of geotextile increased the contact area between sand and cementation media, which effec...

As a biological ground improvement technology, microbially induced calcite precipitation (MICP) is capable of improving engineering properties of soil. It has been used to enhance the strength, stiffness, and permeability of soil. The MICP technique has gained much attention for soil improvement worldwide1,2,3,4. Carbonate precipitation naturally happens and can be induced by nonpathogenic organisms that are native to the soil environment5. The MICP biogeochemical reaction is driven by the existence of ureolytic bacteria, urea and a calcium-rich solution5,6. Sporosarcina pasteurii is a highly active urease enzyme that catalyzes the reaction network towards precipitation of calcite7,8. The urea hydrolysis process produces dissolved ammonium (NH4+) and inorganic carbonate (CO32-). The carbonate ions react with calcium ions to precipitate as calcium carbonate crystals. The urea hydrolysis reactions are shown here:
<img alt="Equation 1" src="/files/ftp_upload/60059/60059equ01.jpg" />
<img alt="Equation 2" src="/files/ftp_upload/60059/60059equ02.jpg" />
The precipitated CaCO3 can bond the sand particles together to improve the engineering properties of MICP-treated soil. The MICP technique has been applied in various applications, such as improvement of strength and stiffness of soil, repair of concrete, and environmental remediation9,10,11,12,13,14,15.
Zhao et al.16 developed an immersion method to prepare MICP-treated samples. A full contact flexible mold made of geotextile was used in this method. The precipitated CaCO3 distributed uniformly throughout their MICP-treated samples. Bu et al.17 developed a rigid full contact mold to prepare MICP-treated beam samples by an immersion method. The MICP-treated sample prepared by this method using a rigid full contact mold can form the suitable beam shape. The MICP-treated sample was divided into four and the CaCO3 contents were measured. The CaCO3 content ranged from 8.4 &#177; 1.5% to 9.4 &#177; 1.2% by weight, which indicated that the CaCO3 distributed uniformly in the MICP-treated samples by the immersion method. These MICP-treated samples also achieved better mechanical properties. These MICP-treated bio-specimens reached a 950 kPa flexure strength, which was similar to that of 20- 25% cement-treated samples (600- 1300 kPa). Li et al.10 added randomly distributed discrete fiber into the sandy soil and treated the soil by the MICP immersion method. They found that the shear strength, ductility, and failure strain of MICP-treated soil were enhanced obviously by adding appropriate fiber.
The immersion method for MICP has been continually improved10,16,17. This method can be used to prepare MICP-treated soil samples and MICP-treated prefabricated building materials, such as bricks and beams. Different geometry dimensions of sample preparation mold were developed. Fibers were added in the MICP-treated samples to enhance their properties. This detailed protocol was intended to document the immersion methods for MICP treatment.

<table>
	<tbody>
		<tr>
			<td>Ammonium Chloride, &#62;99%</td>
			<td>Bio-world</td>
			<td>40100196-3 (705033)</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium Sulfate</td>
			<td>Bio-world</td>
			<td>30635330-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Calcium Chloride Dihydrate, &#62;99%</td>
			<td>Bio-world</td>
			<td>40300016-3 (705111)</td>
			<td></td>
		</tr>
		<tr>
			<td>Nutrient Broth</td>
			<td>Bio-world</td>
			<td>30620056-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Bicarbonate, &#62;99%</td>
			<td>Bio-world</td>
			<td>41900068-3 (705727)</td>
			<td></td>
		</tr>
		<tr>
			<td>Sporosarcina pasteurii</td>
			<td>American Type Culture Collection</td>
			<td>ATCC 11859</td>
			<td></td>
		</tr>
		<tr>
			<td>Synthetic fiber</td>
			<td>FIBERMESH</td>
			<td>Fibermesh 150e3</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris-Base, Biotechnology Grade, &#62;99.7%</td>
			<td>Bio-world</td>
			<td>42020309-2 (730205)</td>
			<td></td>
		</tr>
		<tr>
			<td>Urea, USP Grade, &#62;99%</td>
			<td>Bio-world</td>
			<td>42100008-2 (705986)</td>
			<td></td>
		</tr>
		<tr>
			<td>Yeast Extract</td>
			<td>Bio-world</td>
			<td>30620096-3 (760095)</td>
			<td></td>
		</tr>
	</tbody>
</table>

sandy soil improvement through microbially induced calcite precipitation (micp) by immersion

The goal of this article is to develop an immersion method to improve the microbially induced calcite precipitation (MICP) treated samples. A batch reactor was assembled to immerse soil samples into cementation media. The cementation media can freely diffuse into the soil samples in the batch reactor instead of cementation media being injected. A full contact flexible mold, a rigid full contact mold, and a cored brick mold were used to prepare different soil sample holders. Synthetic fibers and natural fibers were selected to reinforce the MICP-treated soil samples. The precipitated CaCO3 in different areas of the MICP-treated samples was measured. The CaCO3 distribution results demonstrated that the precipitated CaCO3 was distributed uniformly in the soil sample by the immersion method.

Figure 7 shows the distribution of precipitated CaCO3 throughout the MICP-treated sample. The MICP-treated sample was divided into three different areas. The CaCO3 content in each area was tested by the acid washing method. To dissolve precipitated carbonates, the dry MICP-treated samples were washed in a HCl solution (0.1 M), then rinsed, drained, and oven-dried for 48 hours. The difference value between the masses of samples before and after acid washing was considere...

Watch this Scientific Journal Video about Sandy Soil Improvement through Microbially Induced Calcite Precipitation MICP by Immersion at JoVE.com

Sandy Soil Improvement through Microbially Induced Calcite Precipitation MICP by Immersion

Here, microbially induced calcite precipitation (MICP) technology is presented to improve soil properties by immersion.

Sandy Soil Improvement through Microbially Induced Calcite Precipitation (MICP) by Immersion

The goal of this article is to develop an immersion method to improve the microbially induced calcite precipitation (MICP) treated samples. A batch ...

The immersion method demonstrated in this protocol help researcher remove unbroken MICP-treated soil sample for mechanical testing through different mold. This technique help MICP-treated soil sample get more uniform precipitated calcium carbonate. Those MICP-treated soil samples also get better mechanic properties through this method.The most important aspect of this technique is to ensure the activity of bacteria is good enough for MICP process to avoid time consuming and material wasting. Designing appropriate molds for different application is considered to be another important aspect for researchers who intend to select this technique for the first time. To begin, transfer 0.1 milliliter of bacterial suspension to a centrifuge tube filled with 10 milliliters of fresh growth medium.Mix well by inverting and then, loosen the lid of the tube in order to maintain aerobic conditions. Prepare six tubes of bacterial suspensions with growth medium and one control tube with 10 milliliters of fresh growth medium alone. Incubate all tubes in a shaker at 200 RPM and 30 degrees Celsius for 48 to 72 hours.If the growth medium becomes turbid after 48 hours, stop the incubation. Centrifuge the tubes with bacteria and growth medium at 4, 000 times g for 20 minutes. Remove the supernatant, replace with 25 milliliters of fresh growth medium, and mix well using a vortex machine.Then, to enhance the culture of bacteria, transfer 0.25 milliliters of the suspension from the tubes into new tubes with 25 milliliters of growth medium to inoculate. Incubate all tubes in a shaker at 200 RPM and 30 degrees Celsius for 48 hours. Centrifuge the tubes with bacteria and growth medium at 4, 000 times g for 20 minutes.Remove the supernatant, replace with fresh growth medium, and mix well using a vortex machine. Measure the optical density of the suspension at 600 nanometers on a spectrophotometer. Adjust the bacteria concentration using fresh growth medium to an OD600 of 0.6.Add approximately 140 grams of dry Ottawa sand with 99.7%cords into molds by the air pluviation method to reach a median dense condition with relative density in the range of 42 to 55%and sand dry density in the range of 1.58 to 1.64 grams per cubic centimeters. Place a cover on top of the samples and fix it by sewing. Pour the bacterial solution through the permeable geotextile cover into the samples.When flowing bacterial solution is observed on the bottom of soil samples, they are considered saturated. Next, place the samples on the shelf. Immerse the entire shelf into a batch reactor filled with cementation media.Turn on the air supply and adjust the air output to keep 100%air saturation. Wait for seven days of MICP reaction. Take out the samples from the reactor.Use a knife to cut the full-contact flexible mold. Then, wash the samples with water to remove the residual solution in the pore spaces. Place the samples in a 105-degree Celsius oven for 48 hours until their weights remain constant.For the synthetic fiber, mix 2.7 grams of the fibers and 900 grams of the dry sand in small increments by hand to obtain a uniform mixture with 0.3%fiber content. For the natural palm fiber, prepare four parts of sand with 190 grams each. Prepare three layers of fibers with approximately 1.8 grams each.Add the four parts of sand and three layers of fibers in rigid full-contact mold at intervals. Next, repeat the MICP treatment as previously. In this protocol, precipitated calcium carbonate was observed throughout the MICP-treated sample.The MICP-treated sample was divided into three different areas. The calcium carbonate content of the MICP-treated sample by the immersion method ranged from 9.0 to 9.5%indicating the precipitated calcium carbonate was distributed uniformly throughout the soil sample. The stress strain curves of bio-brick reinforced with three layers of palm fiber and unreinforced bio-brick showed the flexure strength of unreinforced bio-brick was 1, 150 kilopascals, while that of reinforced bio-brick was 980 kilopascals.The flexure strain was improved significantly by addition of the palm fiber. It is very important to ensure the activity of bacteria solution before MICP process. If not, it is uncertain to be successful in the experiment.Once the experiment fails, it should be a waste of time and materials. Following this procedure, different molds can be designed for different experimental purpose through MICP technique. The influence of MICP on different kinds of structure or different materials can be simulated by these molds.

sandy-soil-improvement-through-microbially-induced-calcite

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Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a significant role in laser-material interaction, especially in the air environment1-11.
Early plasma evolution has been captured through pump-probe shadowgraphy1-3 and interferometry1,4-7. However, the studied time frames and applied laser parameter ranges are limited. For example, direct examinations of plasma front locations and electron number densities within a delay time of 100 picosecond (ps) with respect to the laser pulse peak are still very few, especially for the ultrashort pulse of a duration around 100 femtosecond (fs) and a low power density around 1014 W/cm2. Early plasma generated under these conditions has only been captured recently with high temporal and spatial resolutions12. The detailed setup strategy and procedures of this high precision measurement will be illustrated in this paper. The rationale of the measurement is optical pump-probe shadowgraphy: one ultrashort laser pulse is split to a pump pulse and a probe pulse, while the delay time between them can be adjusted by changing their beam path lengths. The pump pulse ablates the target and generates the early plasma, and the probe pulse propagates through the plasma region and detects the non-uniformity of electron number density. In addition, animations are generated using the calculated results from the simulation model of Ref. 12 to illustrate the plasma formation and evolution with a very high resolution (0.04 ~ 1 ps).
Both the experimental method and the simulation method can be applied to a broad range of time frames and laser parameters. These methods can be used to examine the early plasma generated not only from metals, but also from semiconductors and insulators.

An experimental method to examine the early plasma evolution induced by ultrashort laser pulses is described. Using this method, high quality images of early plasma are obtained with high temporal and spatial resolutions. A novel integrated atomistic model is used to simulate and explain the mechanisms of early plasma.

Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a ...

Real-Time DC-dynamic Biasing Method for Switching Time Improvement in Severely Underdamped Fringing-field Electrostatic MEMS Actuators

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input bias voltage. However, the tradeoff for the improved switching performance is a relatively long settling time to reach each gap height in response to various applied voltages. Transient applied bias waveforms are employed to facilitate reduced switching times for electrostatic fringing-field MEMS actuators with high mechanical quality factors. Removing the underlying substrate of the fringing-field actuator creates the low mechanical damping environment necessary to effectively test the concept. The removal of the underlying substrate also a has substantial improvement on the reliability performance of the device in regards to failure due to stiction. Although DC-dynamic biasing is useful in improving settling time, the required slew rates for typical MEMS devices may place aggressive requirements on the charge pumps for fully-integrated on-chip designs. Additionally, there may be challenges integrating the substrate removal step into the back-end-of-line commercial CMOS processing steps. Experimental validation of fabricated actuators demonstrates an improvement of 50x in switching time when compared to conventional step biasing results. Compared to theoretical calculations, the experimental results are in good agreement.

The robust device design of fringing-field electrostatic MEMS actuators results in inherently low squeeze-film damping conditions and long settling times when performing switching operations using conventional step biasing. Real-time switching time improvement with DC-dynamic waveforms reduces the settling time of fringing-field MEMS actuators when transitioning between up-to-down and down-to-up states.

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input ...

Visible-light Induced Reduction of Graphene Oxide Using Plasmonic Nanoparticle

Present work demonstrates the simple, chemical free, fast, and energy efficient method to produce reduced graphene oxide (r-GO) solution at RT using visible light irradiation with plasmonic nanoparticles. The plasmonic nanoparticle is used to improve the reduction efficiency of GO. It only takes 30 min&#160;at RT by illuminating the solutions with Xe-lamp, the r-GO solutions can be obtained by completely removing gold nanoparticles through simple centrifugation step. The spherical gold nanoparticles (AuNPs) as compared to the other nanostructures is the most suitable plasmonic nanostructure for r-GO preparation. The reduced graphene oxide prepared using visible light and AuNPs was equally qualitative as chemically reduced graphene oxide, which was supported by various analytical techniques such as UV-Vis spectroscopy, Raman spectroscopy, powder XRD and XPS. The reduced graphene oxide prepared with visible light shows excellent quenching properties over the fluorescent molecules modified on ssDNA and excellent fluorescence recovery for target DNA detection. The r-GO prepared by recycled AuNPs is found to be of same quality with that of chemically reduced r-GO. The use of visible light with plasmonic nanoparticle demonstrates the good alternative method for r-GO synthesis.

A simple protocol for the preparation of reduced graphene oxide using visible light and plasmonic nanoparticle is described.

Present work demonstrates the simple, chemical free, fast, and energy efficient method to produce reduced graphene oxide (r-GO) solution at RT using ...

Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation

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This manuscript describes how to create regular bedforms in a flume, visualize flow through the bedforms, and use computer simulations to simulate the hyporheic flow. The computer simulations compare well with the experimental observations. This coupled simulation and experiment is well-suited for both research and educational purposes.

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute ...

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a new and inexpensive procedure to force mode locking in a pre-adjusted nonlinear polarization rotation fiber laser. This procedure is based on the detection of a sudden change in the output polarization state when mode locking occurs. This change is used to command the alignment of the intra-cavity polarization controller in order to find mode-locking conditions. More specifically, the value of the first Stokes parameter varies when the angle of the polarization controller is swept and, moreover, it undergoes an abrupt variation when the laser enters the mode-locked state. Monitoring this abrupt variation provides a practical easy-to-detect signal that can be used to command the alignment of the polarization controller and drive the laser towards mode locking. This monitoring is achieved by feeding a small portion of the signal to a polarization analyzer measuring the first Stokes parameter. A sudden change in the read out of this parameter from the analyzer will occur when the laser enters the mode-locked state. At this moment, the required angle of the polarization controller is kept fixed. The alignment is completed. This procedure provides an alternate way to existing automating procedures that use equipment such as an optical spectrum analyzer, an RF spectrum analyzer, a photodiode connected to an electronic pulse-counter or a nonlinear detecting scheme based on two-photon absorption or second harmonic generation. It is suitable for lasers mode locked by nonlinear polarization rotation. It is relatively easy to implement, it requires inexpensive means, especially at a wavelength of 1550 nm, and it lowers the production and operation costs incurred in comparison to the above-mentioned techniques.

A protocol to detect and automate mode locking in a pre-adjusted nonlinear polarization rotation fiber laser is presented. The detection of a sudden change in the output polarization state when mode locking occurs is used to command the alignment of an intra-cavity polarization controller in order to find mode-locking conditions.

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a ...

Laser-induced Forward Transfer of Ag Nanopaste

Over the past decade, there has been much development of non-lithographic methods1-3 for printing metallic inks or other functional materials. Many of these processes such as inkjet3 and laser-induced forward transfer (LIFT)4 have become increasingly popular as interest in printable electronics and maskless patterning has grown. These additive manufacturing processes are inexpensive, environmentally friendly, and well suited for rapid prototyping, when compared to more traditional semiconductor processing techniques. While most direct-write processes are confined to two-dimensional structures and cannot handle materials with high viscosity (particularly inkjet), LIFT can transcend both constraints if performed properly. Congruent transfer of three dimensional pixels (called voxels), also referred to as laser decal transfer (LDT)5-9, has recently been demonstrated with the LIFT technique using highly viscous Ag nanopastes to fabricate freestanding interconnects, complex voxel shapes, and high-aspect-ratio structures. In this paper, we demonstrate a simple yet versatile process for fabricating a variety of micro- and macroscale Ag structures. Structures include simple shapes for patterning electrical contacts, bridging and cantilever structures, high-aspect-ratio structures, and single-shot, large area transfers using a commercial digital micromirror device (DMD) chip.

We demonstrate the use of the Laser-induced forward transfer technique (LIFT) for the printing of high-viscosity Ag paste. This technique offers a simple, low temperature, robust process for non-lithographically printing microscale 2D and 3D structures.

Over the past decade, there has been much development of non-lithographic methods1-3 for printing metallic inks or other functional materials. Many of ...

Magnetically Induced Rotating Rayleigh-Taylor Instability

Classical techniques for investigating the Rayleigh-Taylor instability include using compressed gasses1, rocketry2 or linear electric motors3 to reverse the effective direction of gravity, and accelerate the lighter fluid toward the denser fluid. Other authorse.g. 4,5,6 have separated a gravitationally unstable stratification with a barrier that is removed to initiate the flow. However, the parabolic initial interface in the case of a rotating stratification imposes significant technical difficulties experimentally. We wish to be able to spin-up the stratification into solid-body rotation and only then initiate the flow in order to investigate the effects of rotation upon the Rayleigh-Taylor instability. The approach we have adopted here is to use the magnetic field of a superconducting magnet to manipulate the effective weight of the two liquids to initiate the flow. We create a gravitationally stable two-layer stratification using standard flotation techniques. The upper layer is less dense than the lower layer and so the system is Rayleigh-Taylor stable. This stratification is then spun-up until both layers are in solid-body rotation and a parabolic interface is observed. These experiments use fluids with low magnetic susceptibility, |&#967;| ~ 10-6 - 10-5, compared to a ferrofluids. The dominant effect of the magnetic field applies a body-force to each layer changing the effective weight. The upper layer is weakly paramagnetic while the lower layer is weakly diamagnetic. When the magnetic field is applied, the lower layer is repelled from the magnet while the upper layer is attracted towards the magnet. A Rayleigh-Taylor instability is achieved with application of a high gradient magnetic field. We further observed that increasing the dynamic viscosity of the fluid in each layer, increases the length-scale of the instability.

We present a protocol for preparing a two-layer density-stratified liquid that can be spun-up into solid body rotation and subsequently induced into Rayleigh-Taylor instability by applying a gradient magnetic field.

Classical techniques for investigating the Rayleigh-Taylor instability include using compressed gasses1, rocketry2 or linear electric motors3 to reverse ...

Preparation of Liquid Crystal Networks for Macroscopic Oscillatory Motion Induced by Light

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous light irradiation. The photo-excitation of dopants that can quickly dissipate light into heat, coupled with anisotropic thermal expansion and self-shadowing of the film, gives rise to the self-sustained deformation. The oscillations observed are influenced by the dimensions and the modulus of the film, and by the directionality and intensity of the light. The system developed offers applications in energy conversion and harvesting for soft-robotics and automated systems.
The general method described here consists of creating free-standing liquid crystalline films and characterizing the mechanical and thermal effects observed. The molecular alignment is achieved using alignment layers (rubbed polyimide), commonly used in the display manufacturing industry. To obtain actuators with large deformation, the mesogens are aligned and polymerized in a splay/bend configuration, i.e., with the director of the liquid crystals (LCs) going gradually from planar to homeotropic through the film thickness. Upon irradiation, the mechanical and thermal oscillations obtained are monitored with a high-speed camera. The results are further quantified by image analysis using an image processing program.

The goal of the protocol is to create liquid crystalline polymer films that can mechanically oscillate under continuous light irradiation. We describe in great detail the conception of free-standing films, from the liquid crystal alignment method to the photo-actuation. The experimental protocol applied to prepare this material is broadly applicable.

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous ...

Measurements of Soil Carbon by Neutron-Gamma Analysis in Static and Scanning Modes

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of gamma rays created when neutrons interact with soil elements. The main parts of the INS system are a pulsed neutron generator, NaI(Tl) gamma detectors, split electronics to separate gamma spectra due to INS and thermo-neutron capture (TNC) processes, and software for gamma spectra acquisition and data processing. This method has several advantages over other methods in that it is a non-destructive in situ method that measures the average carbon content in large soil volumes, is negligibly impacted by local sharp changes in soil carbon, and can be used in stationary or scanning modes. The result of the INS method is the carbon content from a site with a footprint of ~2.5 - 3 m2 in the stationary regime, or the average carbon content of the traversed area in the scanning regime. The measurement range of the current INS system is &#62;1.5 carbon weight % (standard deviation &#177; 0.3 w%) in the upper 10 cm soil layer for a 1 hmeasurement.

Here, we present the protocol for in situ measurement of soil carbon using the neutron-gamma technique for single point measurements (static mode) or field averages (scanning mode). We also describe system construction and elaborate data treatment procedures.

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of ...

Quantitative Analysis of Vacuum Induction Melting by Laser-induced Breakdown Spectroscopy

Vacuum induction melting is a popular method for refining high purity metal and alloys. Traditionally, standard process control in metallurgy involves several steps, include drawing samples, cooling, cutting, transport to the laboratory, and analysis. The whole analysis process requires more than 30 minutes, which hinders on-line process control. Laser-induced breakdown spectroscopy is an excellent on-line analysis method that can satisfy the requirements of vacuum induction melting because it is fast and noncontact and does not require sample preparation. The experimental facility uses a lamp-pumped Q-switched laser to ablate melted liquid steel with an output energy of 80 mJ, a frequency of 5 Hz, a FWHM pulse width of 20 ns, and a working wavelength of 1,064 nm. A multi-channel linear charge coupled device (CCD) spectrometer is used to measure the emission spectrum in real time, with a spectral range from 190 to 600 nm and a resolution of 0.06 nm at a wavelength of 200 nm. The protocol includes several steps: standard alloy sample preparation and an ingredient test, smelting of standard samples and determination of the laser breakdown spectrum, and construction of the elements concentration quantitative analysis curve of each element. To realize the concentration analysis of unknown samples, the spectrum of a sample also needs to be measured and disposed with the same process. The composition of all main elements in the melted alloy can be quantitatively analyzed with an internal standard method. The calibration curve shows that the limit of detection of most metal elements ranges from 20-250 ppm. The concentration of elements, such as Ti, Mo, Nb, V, and Cu, can be lower than 100 ppm, and the concentrations of Cr, Al, Co, Fe, Mn, C, and Si range from 100-200 ppm. The R2 of some calibration curves can exceed 0.94.

During vacuum induction melting, laser-induced breakdown spectroscopy is used to perform real-time quantitative analysis of the main-ingredient elements of a molten alloy.

Vacuum induction melting is a popular method for refining high purity metal and alloys. Traditionally, standard process control in metallurgy involves ...