The development of the testing protocol reported in this publication results from a joint research project between Natural Resources Canada (CanmetCERL, Explosives R&#38;D Section) and Orica Mining Services. Permission of Orica Mining Services to publish non-proprietary information on this subject is fully acknowledged. The participation of CanmetCERL&#39;s Analytical Section to the physical characterization of the various AWEs prepared throughout the present work is also gratefully acknowledged.

NOTE: The materials and equipment used here are listed in the Table of Materials.
1. Preparation of Ignition Wire Assemblies
NOTE: Wearing nitrile gloves is recommended for this operation.
<ol>
	<li>Measure a pre-determined length of nichrome (NiCr) wire and cut using a wire cutter. Cut 85 mm lengths for 76.2 mm (3&#34;) long test cells.</li>
	<li>Using needle nose pliers, bend the NiCr wire to make a small loop at each end. With a proper crimping tool, splice each one into 50 cm length of 14 American Wire Gauge (AWG) solid core bare copper wire using uninsulated butt-end splice connectors.</li>
	<li>Repeat Step 1.1-1.2 to make as many assemblies as required. 
	NOTE: It is recommended to prepare several assemblies in advance as each MBP measurement will take 10 to 15 assemblies). A completed wire assembly is shown in Figure 1. If all wires are correctly spliced and crimped to the connector, the resistance measured across the wire assembly (as measured on the copper conductors on either side of the NiCr wire) must be less than 0.5 &#937;.</li>
</ol>
2. Sample and Test Cell Preparation
NOTE: Wearing nitrile gloves is recommended for this operation.
<ol>
	<li>Prepare test cells each consisting of a small cylindrical steel pipe with a length of 7.6 cm and an internal diameter of at least 1.6 cm. Ensure that each test cell has a 3 mm-wide slit machined along the axis to allow combustion gases to escape during the tests. 
	NOTE: AWEs are electrically conductive.</li>
	<li>To ensure that all the ignition current will go through the ignition wire, paint the interior of each cell with two coats of high-temperature non-conductive paint. Prepare several test cells in advance.</li>
	<li>Prepare several No. 0 neoprene stoppers by reaming the inside face to accommodate the splice connectors and the copper conductors of the ignition wire assembly.</li>
	<li>Use the horizontal slit on the test cell to insert the ignition wire into the middle of the cell. Carefully slide a prepared neoprene stopper along each copper wire and insert them into each end of the cell, ensuring that the ignition wire is not compressed or twisted.</li>
	<li>Pull the ignition wire taut and bend the copper leg-wires vertically to secure them (Figure 2, Figure 3).</li>
	<li>Introduce the sample into the cell through the 3 mm-wide slit with caution to avoid causing crystallization of the sample and introducing air voids in the sample. Use a spatula to tamp down the emulsion to remove air voids if necessary. Quickly tap the cell repeatedly on a countertop to ensure that the emulsion settles into voids. Repeat filling, tamping, and tapping until the emulsion no longer settles any further.</li>
</ol>
3. Loading Sample in Pressure Vessel
<ol>
	<li>Prepare a pressure vessel with the following characteristics to load the sample cell: an operating pressure resistance of 20.7 MPa (or 3,000 psig) (see the Table of Materials), made of stainless steel to avoid long-term corrosion damage from the gaseous reaction products, equipped with two insulated rigid feedthrough electrodes capable of carrying an electric current up to 20 A, and sealed to have a pressure rating equivalent to that of the vessel itself.
	<ol>
		<li>For safety reasons, install the vessel in a protected test room equipped with a rupture disc assembly (see the Table of Materials) designed to vent the vessel at a pressure slightly lower than its maximum operating pressure.</li>
		<li>In order to vent the vessel after a test, equip the gas outlet with a high-pressure valve that can be operated remotely. 
		NOTE: This can be achieved in various ways. For example, it can be achieved using a solenoid valve/air operated valve combination. The inlet of the vessel must be connected to a gas manifold system operated from a nearby protected room capable of remotely pressurizing the pressure vessel to a chosen initial pressure using a pressurized cylinder of argon (nitrogen may be an alternative but may not be as inert). This manifold would be typically custom made out of high-pressure stainless-steel tubing, and high-pressure compression fittings and valves. It is recommended that the vessel also be equipped with a 0-20.7 MPa (0-3,000 psig) pressure transducer.</li>
	</ol>
	</li>
	<li>Introduce a test cell with sample (prepared in section 2) into the pressure vessel. Position its long axis horizontally with the slit on the top (Figure 2). Connect the bare copper wires to the electrodes inside the vessel. Ensure the former are not touching the body of the vessel. Close and seal the pressure vessel.</li>
	<li>Using the multimeter ensure there is no electrical contact between each electrode and the body of the pressure vessel. 
	NOTE: If any contact is detected between an electrode and the body of the vessel, its cause(s) must be determined and actions must be taken to eliminate it before testing can proceed.</li>
</ol>
4. Performing a Test
<ol>
	<li>In the protected room, connect the signal from the pressure transducer to the data acquisition (see the Table of Materials) or available oscilloscope. Also, connect the voltage across the high precision shunt resistor to the data acquisition (or oscilloscope). Ensure that this shunt resistor is also connected in series with a constant current source. Connect the series to the electrodes on the pressure vessel to supply a constant current through the NiCr wire. 
	NOTE: Knowing its resistance, the voltage across this shunt resistor provides a measurement of the ignition current.</li>
	<li>Start the PC-based data acquisition system (or available oscilloscope).</li>
	<li>Remotely close the vessel&#39;s outlet valve (see section 3.1 Note). Using a pressurized argon cylinder in the instrument room and the gas manifold (described in section 3), start pressurizing the vessel to the required initial pressure for the test. 
	NOTE: Depending on the formulation of the AWE, this pressure can vary anywhere from 0.3 to 19.3 MPa (50 to 2500 psig). If this is the first test with a given AWE product, make an educated guess of the MBP, based on the formulation of the sample, to decide at what pressure this first test must be performed.
	<ol>
		<li>Once pressurization is achieved, close the vessel&#39;s inlet valve and leave the vessel pressurized for 5 to 10 min to check that the system has no significant leaks. Once this is established, re-open the inlet valve, adjust the pressure to the chosen initial value, and re-close the inlet valve. If a significant leak rate is detected, postpone testing until required maintenance has been performed.</li>
	</ol>
	</li>
	<li>Turn on the constant current source and allow a 10.5 A current to flow through the ignition wire. Keep the current on until the sample ignites and melts the ignition wire, stopping the flow of current; this is expected to take a few s. Turn the power supply off after ignition has taken place and the pressure has started to increase. 
	NOTE: The pressure may go through one or two minima and maxima and should start to decrease continuously. When this has happened, wait for an extra 10 min before doing anything.</li>
	<li>Once the test is completed, remotely open the outlet valve and vent all combustion gases to an appropriate exhaust system. Slowly purge with argon for a few min to remove all toxic gas species before opening the vessel. Ensure the vessel is back to ambient pressure before re-entering the test room.</li>
	<li>Lock out the constant current power supply (either using a lock out key or unplugging it from the AC power) and walk to the pressure vessel room. Wearing a face mask with appropriate general-purpose cartridge, open the vessel. Recuperate the test cell by undoing the copper conductors from the electrodes and note down all visual observations.
	<ol>
		<li>By removing the neoprene stoppers try to observe how much of the sample has burned. Further document these observations by taking photographs. Once finished, clean the vessel thoroughly (see section 6). 
		NOTE: From these observations, if the sample has burned completely (combustion front reached the wall of the test cell; small amount of sample can be left on the neoprene stoppers), the result is deemed to be a &#39;go&#39;. Decrease the pressure for the next test. Otherwise the result is deemed to be a &#39;no-go&#39; and the pressure must be increased for the next test (see typical observations in Figure 4A). The pressure record from the transducer can also be used as evidence of sustained combustion or not (Figure 4B).</li>
	</ol>
	</li>
	<li>Use the steps outlined in section 5 below to analyse the acquired current and pressure data. Repeat steps 4.1 to 4.6 while gradually decreasing the pressure increments (or decrements) until the MBP has been determined to the desired degree of precision (see typical examples in Figure 5).
	<ol>
		<li>Perform a minimum of 10 to 12 tests using this &#39;up-and-down&#39; methodology. 
		NOTE: The quoted MBP must be the mean between the initial pressure of the highest &#39;no-go&#39; event (Pn,max) and that of the lowest &#39;go&#39; event (Pg,min) (Figure 5). The error bar on the measured MBP must be specified as: 
		<img alt="Equation" src="/files/ftp_upload/56167/56167eq1.jpg" /></li>
	</ol>
	</li>
</ol>
5. Data Analysis
NOTE: See Figure 6 for an example of a graph showing an analyzed MBP experiment.
<ol>
	<li>First determine the time, t0, when the ignition wire was turned on (current suddenly increases to 10.5 A). Determine the time when the ignition wire burned out (current suddenly returns to 0), tb. Record the difference &#916;tw = tb &#8211; t0 as the &#34;wire lasted&#34; time.</li>
	<li>Determine the average ignition wire current, Iiw; this is the average of all the data points of the current record between t0 and tb. Determine the time when the pressure trace first deviates from the initial baseline, tp0. Record the difference &#916;tp = tp0 &#8211; t0 as the &#34;Time to Pressure Rise&#34;.</li>
	<li>Determine the average initial pressure, Pi; this is the average of all the data points of the pressure record between t0 and tp0. Determine the maximum pressure, Pmax; this is the maximum value of the pressure record. 
	NOTE: The pressure trace may contain several minima and maxima.</li>
	<li>Locate the last maximum (just before the pressure starts to continuously decrease when burning is complete); this is the burn stop time (ts). Calculate the difference &#916;tb = ts &#8211; tp0 and enter it as the &#34;Burn Time&#34;.</li>
</ol>
6. Cleaning up
<ol>
	<li>Clean and reuse the test cells as much as possible. Dispose of a test cell whenever it is found that solid residues are very difficult to clean out. Clean the cells with water, ethanol and paper towel. If the non-conductive paint is damaged, repaint the cell before re-using it. 
	NOTE: Using soap or any detergent to clean the cells is not recommended because detergent residues may destabilize the surfactant in some emulsion formulations.</li>
	<li>Clean the vessel after each run. 
	NOTE: Wearing a face mask with appropriate general-purpose cartridges is recommended for the person cleaning the vessel. Certain formulations, especially those that contain chemical sensitizers, may create more irritating residues than others.</li>
	<li>Remove dirt and moisture from the pressure vessel using paper towels, applying water or ethanol as required. Ensure that the electrodes are cleaned in a similar manner, including the washers and nuts.</li>
	<li>At the end of the day, return all unused sample material and wastes to an appropriate storage location (usually an explosives magazine).</li>
	<li>Turn off the data acquisition system and computer (or storage oscilloscope).</li>
	<li>Close the main valve on the argon (or nitrogen) cylinder and bleed the argon (or nitrogen) lines.</li>
</ol>

<ol>
	<li>Bluhm, H. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ammonium+nitrate+emulsion+blasting+agent+and+method+of+preparing+same.">Ammonium nitrate emulsion blasting agent and method of preparing same.</a> US Patent. , (1969).</li><li>Persson, P. -. A., Holmberg, R., Lee, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Rock Blasting and Explosives Engineering. , 86 (1993).</li><li>Perlid, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pump+Safety+Tests+Regarding+Emulsion+Explosives.">Pump Safety Tests Regarding Emulsion Explosives.</a> Proceedings of the 22nd Annual Conference on Explosives and Blasting Techniques, International Society of Explosives Engineers. 2, 101-107 (1996).</li><li>Chan, S. K., Kirchnerova, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ignition+and+Combustion+Characteristics+of+Water-gel+Explosives.">Ignition and Combustion Characteristics of Water-gel Explosives.</a> Proceedings of the 18th Explosives Safety Seminar, U.S. DOD. , 193-200 (1978).</li><li>Guidelines for the Pumping of Water-Based Explosives. Natural Resources Canada, Explosives Regulatory Division, Minister of Public Works and Government Services Canada, Catalog no. M37-53/2003E Available from: <a target="_blank" href="https://miningandblasting.files.wordpress.com/2009/09/canadian-guidelines-for-pumping-of-water-based-explosives.pdf">https://miningandblasting.files.wordpress.com/2009/09/canadian-guidelines-for-pumping-of-water-based-explosives.pdf</a> (2016)</li><li>. Guidelines for the Pumping of Bulk, Water-Based Explosives Available from: <a target="_blank" href="https://miningandblasting.files.wordpress.com/2009/09/pumping-of-water-based-explosives-june-2010.pdf">https://miningandblasting.files.wordpress.com/2009/09/pumping-of-water-based-explosives-june-2010.pdf</a> (2010)</li><li>Wang, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Ignition and Combustion Characteristics of Emulsion Explosives under Pressure. , (1991).</li><li>Hirosaki, Y., Suzuki, S., Takahashi, Y., Kato, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Burning+Characteristics+of+Emulsion+Explosives+(I)+–+Pressurized+Vessel+Test.">Burning Characteristics of Emulsion Explosives (I) – Pressurized Vessel Test.</a> Kayaku Gakkaishi. 61, 35-41 (2000).</li><li>Turcotte, R., Lightfoot, P. D., Badeen, C. M., Vachon, M., Jones, D. E. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Pressurized+Vessel+Test+to+Measure+the+Minimum+Burning+Pressure+of+Water-Based+Explosives.">A Pressurized Vessel Test to Measure the Minimum Burning Pressure of Water-Based Explosives.</a> Propellants, Explos., Pyrotech. 30, 118-126 (2005).</li><li>Turcotte, R., Goldthorp, S., Badeen, C., Chan, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hot-wire+Ignition+of+AN-based+Emulsions.">Hot-wire Ignition of AN-based Emulsions.</a> Propellants, Explos., Pyrotech. 33, 472-481 (2008).</li><li>Chan, S. K., Turcotte, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Onset+Temperatures+in+Hot-wire+Ignition+of+AN-Based+Emulsions.">Onset Temperatures in Hot-wire Ignition of AN-Based Emulsions.</a> Propellants, Explos., Pyrotech. 34, 41-49 (2009).</li><li>Goldthorp, S., Turcotte, R., Badeen, C. M., Chan, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Minimum+Pressure+for+Sustained+Combustion+in+AN-based+Emulsions.">Minimum Pressure for Sustained Combustion in AN-based Emulsions.</a> Proceedings of the 35th International Pyrotechnics Seminar. , 385-394 (2008).</li><li>Turcotte, R., Goldthorp, S., Badeen, C. M., Feng, H. <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+Physical+Characteristics+and+Ingredients+on+the+Minimum+Burning+Pressure+of+Ammonium+Nitrate+Emulsions.">Influence of Physical Characteristics and Ingredients on the Minimum Burning Pressure of Ammonium Nitrate Emulsions.</a> Propellants, Explos., Pyrotech. 35, 233-239 (2010).</li><li>Badeen, C. M., Goldthorp, S., Turcotte, R., Feng, H., Chan, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+Formulation+Changes+on+the+Minimum+Burning+Pressure+of+Ammonium+Nitrate+Emulsions.">Effect of Formulation Changes on the Minimum Burning Pressure of Ammonium Nitrate Emulsions.</a> Proceedings of the "10i&#232;me Congr&#232;s International de Pyrotechnie", in conjunction with the 37th International Pyrotechnics Seminar (Europyro 2011) , Session S1a. , (2011).</li><li>Turcotte, R., Goldthorp, S., Badeen, C. M., Johnson, C., Feng, H., Chan, S. K. <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+Physical+Characteristics+and+Ingredients+on+the+Minimum+Burning+Pressure+of+Ammonium+Nitrate+Emulsions.">Influence of Physical Characteristics and Ingredients on the Minimum Burning Pressure of Ammonium Nitrate Emulsions.</a> , 197-206 (2009).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria. , 200-207 (2015).</li><li>The Minimum Burning Test for Ammonium Nitrate Emulsions. SAFEX Newsletter Available from: <a target="_blank" href="https://www.safex-international.org/safex/page-newsletter.html">https://www.safex-international.org/safex/page-newsletter.html</a> (2016)</li></ol>

The authors declare that they have no competing financial interests.

Our work demonstrated that the linear hot-wire geometry with 0.5 mm diameter NiCr straight wire and 10 to 16 A ignition current was adequate to ignite AWEs with water contents up to 25 mass %. For high viscosity formulations (such as packaged emulsion products), horizontal and vertical configurations provide almost identical results 17. However, for low viscosity formulae (such as bulk emulsion products) gravity effects in vertical configuration induce emulsion flow which disturbs the ignition process. In these cases, the horizontal configuration was found to provide valid and reproducible results 17. It should be noticed that the MBP values obtained in the present work for high water content emulsions are much lower than those reported by Wang 7 for similar products. This difference is probably due to the fact that, in his case, the ignition source had a coil geometry, which is less efficient to transfer energy to the emulsion, compared with the straight cylindrical geometry used in the present work. Also, if the coil is made out of too small diameter wire or if the loops are too close to each other, the ignition coil may burn prematurely, before the emulsion can be ignited. In such a case, it is very likely that failure to ignite may have been confused with failure to propagate.
As an example, for a typical surface bulk AWE such as EM6 (17.4 % water, Figure 5), the MBP measured with the present cylindrical geometry is 8.2 MPa. The MBP quoted by Wang for a similar product with less water (16.0 % water), using the coil geometry, was 15.2 MPa 7, which is almost twice as high. Moreover, using the coil geometry with the same nichrome wire used in the present work, it has been found that a similar emulsion with 16.8 % water could not be ignited to sustained combustion even at initial pressure up to 15.8 MPa 9. In comparison, the emulsions investigated in the present work, which had water contents as high as 24.8 %, could all be ignited to sustained combustion at pressures below 15 MPa.
As expected, the data obtained in the present work clearly demonstrates that water content is the major ingredient controlling the MBP of AWEs. The role of several other ingredients has also been investigated in some detail. However, many unexpected effects of some ingredients (sodium nitrate and glass microspheres, for examples) have been evidenced 14 and more research would be required to fully understand how their presence affects the ignition and propagation of combustion in these AWE systems.
The test, as described in the above protocol, has been added to the requirements for the authorisation of high explosives in Canada by the Explosives Regulatory Division of Natural Resources Canada 18. It became an authorisation test for the acceptance of explosives handled using pumps or augers. This test has also been proposed as an alternative to the UN TDG Series 8c Test (Koenen test) 19 for AWEs. The acceptance of the test is currently pending further discussion within the informal correspondence group being led by Canada 20. This group consists of seven international Competent Authorities and four non-Government Organizations. More detailed information on the above protocol can be obtained by contacting the authors.

The ammonium nitrate water-based emulsion (AWE) explosive was invented in 1961. It consists of microscopic droplets of a liquid oxidizer solution surrounded by a continuous oil phase. The first stable and practically useful emulsion blasting explosive was developed by Harold F. Bluhm in the USA (1969) 1,2. However, the successful commercialization of this type of explosive did not really happen before the beginning of the 1980s.
With the large scale of modern mining operations and the advent of fast bulk explosive loading methodology, very large volumes of AWE explosives have to be manufactured and transported. One tanker load typically transports 20 tons of AWE and many such truck loads are usually necessary to load only one blast. Accidental initiation of such large quantities of explosives would be particularly disastrous and, therefore, a good knowledge of their hazardous properties is required to design corresponding safe handling systems. While it is well known that emulsions are relatively insensitive to mechanical events (i.e. impact and friction events), accidental explosions have still been reported 3 while handling this type of explosive, particularly in pumping applications.
It has been known since the 1970&#39;s 4 that a minimum ambient pressure is required for self-sustained combustion to take place into water-based explosives. This latter value has usually been termed the &#34;Minimum Burning Pressure&#34; (MBP). From a safety point of view, knowledge of this threshold could allow manufacturers to better estimate safe operating pressures for various handling equipment.
The Department of Natural Resources of the Government of Canada has published &#34;Guidelines for the Pumping of Water-Based explosives&#34; 5, which state that using pumping pressures well below the MBP of the emulsions or watergels is a good safety practice. It should be noticed that these guidelines were designed with the collaboration of most commercial manufacturers and that, in the USA, the Institute of Makers of Explosives (IME) has also published very similar guidelines 6. However, in these documents, there was no description or prescription on how the MBP should be measured.
In the last decades, only a few studies related to MBP measurements have been reported. Chan et al. 4 reported the results of MBP measurements for watergel explosives, which are also ammonium nitrate and water-based. They have concluded that the MBP can have a strong dependency on several formulation factors such as water content, presence of chemical sensitizers or metallic powders. In another study, Wang 7 described a 2.5 L pressure vessel pressurized with N2 and used a Bruceton up-and-down method to determine the MBP for basic AWEs. With this system, MBP values of the order of 15 MPa were measured for a basic emulsion having a water content of 16 mass %.
Using a similar pressurized vessel test, Hirosaki et al. 8 have reported the results of some MBP measurements for AWE explosives. They have noted that the nature (i.e. glass or resin) of the micro-spheres being used to sensitize the explosives also has a strong influence on the results. More recently, Turcotte et al. 9 have developed a system similar to that of Wang and Hirosaki et al. and have attempted to use it to measure the MBP of some AWEs. However, they have found many possible problems that may lead to erroneous MBP determinations. In particular, it was noted that the ignition source geometry (nichrome wire coil) had never been properly validated for AWEs. In 2008, Turcotte et al. 10 and Chan et al. 11, have developed both an apparatus based on a calibrated ignition wire system and an associated methodology to measure the MBP of AWEs. They have also used the facility to study the ignition characteristics of typical AWEs, measured the energy requirements to obtain reliable ignitions 12 and studied the influence of physical characteristics and ingredients on the MBP of a wide variety of AWE explosives 13,14. This MBP measurement technique is presently being proposed as a standard test within the United Nation Transport of Dangerous Goods (UN TDG) Tests and Criteria for the classification for transport of AWEs 15.

<table>
	<tbody>
		<tr>
			<td>Nitrile gloves (100/pk)</td>
			<td>Fisher Scientific</td>
			<td>19149863B</td>
			<td>https://www.fishersci.ca/shop/products/purple-nitrile-exam-gloves-6/19149863b?searchHijack=true&#38;searchTerm=19149863B&#38;searchType=RAPID&#38;matchedCatNo=19149863B</td>
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			<td>NiCr60 wire 24 AWG (200 feet per roll)</td>
			<td>Omega Engineering</td>
			<td>NIC60-020-200</td>
			<td>http://www.omega.ca/pptst_eng/NI60.html</td>
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		<tr>
			<td>Wire cutters: Mini Diagonal Cutting Pliers, 5 in.</td>
			<td>Canadian Tire</td>
			<td>Product #058-4736-0</td>
			<td>http://www.canadiantire.ca/en/pdp/mastercraft-mini-diagonal-cutting-pliers-0584736p.html#srp</td>
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			<td>Mini needle nose pliers, 5 in.</td>
			<td>Canadian Tire</td>
			<td>Product #058-4731-0</td>
			<td>http://www.canadiantire.ca/en/pdp/mastercraft-mini-needle-nose-pliers-0584731p.html#srp</td>
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			<td>Crimping tool, 8.5 in.</td>
			<td>Canadian Tire</td>
			<td>Product #058-4617-4</td>
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			<td>Bare copper wire (14AWG)</td>
			<td>Electronics Plus</td>
			<td>2000BC-14-5/5 lb roll</td>
			<td>Bare (uninsulated) copper wire</td>
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			<td>Non-insulated butt-splice connectors (100 units)</td>
			<td>Electrosonic</td>
			<td>Panduit BS14-C</td>
			<td>http://www.alliedelec.com/panduit-bs14-c/70044299/?mkwid=si03ezhXY&#38;pcrid=64596948257&#38;pkw=panduit%20bs14-c&#38;pmt=b&#38;pdv=c&#38;gclid=CM_1jO-DsdMCFZKIswodMugASw</td>
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			<td>Stainless Steel pipe nipples (10 - 20 units)</td>
			<td>Wolseley Inc.</td>
			<td>SSNKX3</td>
			<td>sample cells: 76.2 mm long x 12.7 mm od (3&#34; long x 0.5&#34; od) with 3 mm slit machined along the length of the cell, painted inside and out with two coats of non-conductive paint (e.g., high-heat barbeque Armor Coat or Krylon brands).</td>
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			<td>High-temperature non-conductive paint</td>
			<td>Canadian Tire</td>
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			<td>Solid green neoprene stoppers (size 0; 1 package of 68)</td>
			<td>Cole-Palmer</td>
			<td>OF-62991-04</td>
			<td>https://www.coleparmer.ca/i/cole-parmer-solid-green-neoprene-stoppers-standard-size-0-68-pk/6299104?searchterm=OF-62991-04</td>
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			<td>Spatula, stainless steel</td>
			<td>Fisher Scientific</td>
			<td>14-375-10</td>
			<td>https://www.fishersci.ca/shop/products/fisherbrand-spoonula-lab-spoon/1437510?searchHijack=true&#38;searchTerm=1437510&#38;searchType=RAPID&#38;matchedCatNo=1437510</td>
		</tr>
		<tr>
			<td>7.5 L Pressure Vessel</td>
			<td>Autoclave Engineers</td>
			<td>40A-9104, 9122, 40C-1365, 2376</td>
			<td>minimum internal diameter of 127 mm; equipped with 20.7 MPa (3000 psi) rupture disc assembly; Solenoid&#38; air operated valve on the outlet; http://www.autoclaveengineers.com/products/pressure_vessels/PV_Bolted_Closure/index.html</td>
		</tr>
		<tr>
			<td>Electrodes (set of 2)</td>
			<td>Electo-meters</td>
			<td>Conax EG-375-A-SS-T, 25.4 cm (10&#34;) conductor</td>
			<td>with Teflon sealing glands; https://www.conaxtechnologies.com/wp-content/uploads/2016/03/5001D-80-105-Flanges-and-Accessories.pdf</td>
		</tr>
		<tr>
			<td>Rupture disc</td>
			<td>Oseco</td>
			<td>39859-3-1</td>
			<td>http://www.oseco.com/imgUL/files/STD_0515.pdf</td>
		</tr>
		<tr>
			<td>Universal safety head (rupture disc assembly)</td>
			<td>Autoclave Engineers</td>
			<td>SS-4600-1/2F</td>
			<td>http://www.autoclave.com/products/accessories/universal_safety_heads/index.html</td>
		</tr>
		<tr>
			<td>High-pressure valve (air-operated, fail-open)</td>
			<td>Autoclave Engineers</td>
			<td>1/2&#34; SW8XXX-CM</td>
			<td>http://www.autoclave.com/aefc_pdfs/OM_P1_Manual_Air_Valve.pdf?zoom_highlightsub=air+operated+valve#search=&#34;air operated valve&#34;</td>
		</tr>
		<tr>
			<td>Pressure transducer</td>
			<td>Omega Engineering</td>
			<td>PX176-3KS5V</td>
			<td>Amplified Voltage Output Transducer for Absolute; 0-20.7 Mpa (0-3000 psi) sealed gauge, 91 cm (36&#34;) cable http://www.omega.ca/pptst_eng/PX176.html</td>
		</tr>
		<tr>
			<td>Digital multimeter</td>
			<td>Amazon.com</td>
			<td>Fluke Model 110 Plus</td>
			<td>https://www.amazon.com/Fluke-110-Plus-essential-multimeter/dp/B01JX912I2</td>
		</tr>
		<tr>
			<td>Data acquisition Interface</td>
			<td>IOTECH</td>
			<td>Model Daqlab 2000 with DBK15 acquisition board</td>
			<td>http://www.mccdaq.com/products/daqlab2000s</td>
		</tr>
		<tr>
			<td>Personal Computer with monitor and National Instruments DASYLab Software (V13, basic) installed</td>
			<td>DELL</td>
			<td>CORETMi7 vProTM</td>
			<td>Computer must meet requirements for Dasylab 13: 1GHz + x86 compatible; Windows 7 or 8, 32-bit or 64-bit; 2 GB+ RAM</td>
		</tr>
		<tr>
			<td>oscilloscope</td>
			<td></td>
			<td></td>
			<td>Any storage oscilloscope with 2 input channels (0-10 V), 12k samples per channel and acquisition frequency of 10 ms/sample.</td>
		</tr>
		<tr>
			<td>Precision Shunt Resister</td>
			<td>Canadian Shunt Industries</td>
			<td>LA-20-100</td>
			<td>(20 A, 100 mV) Enclosed in custom box http://www.cshunt.com/pdf/la.pdf</td>
		</tr>
		<tr>
			<td>Constant Current Power Supply</td>
			<td>Agilent</td>
			<td>N6700B Low-Profile MPS Mainframe, 400W; N6754A DC Power Supply with High Speed Test Extensions option</td>
			<td>http://www.keysight.com/en/pd-1125217-pn-N6754A/high-performance-autoranging-dc-power-module-60v-20a-300w?cc=CA&#38;lc=eng</td>
		</tr>
		<tr>
			<td>Inlet valve</td>
			<td>Ottawa Valves and Fittings</td>
			<td>Swagelok SS-43GS4-PT</td>
			<td>https://www.swagelok.com/en/catalog/Product/Detail?part=SS-43GS4</td>
		</tr>
		<tr>
			<td>Full face mask</td>
			<td>Cooper Safety</td>
			<td>3M 7800 series</td>
			<td>http://www.coopersafety.com/product/3m-7800-series-full-face-respirator-1124.aspx</td>
		</tr>
		<tr>
			<td>General purpose cartridges</td>
			<td>Cooper Safety</td>
			<td>3M 60923</td>
			<td>http://www.coopersafety.com/product/3m-60923-organic-vapor-acid-gas-p100-cartridge-1533.aspx?sid=101950</td>
		</tr>
	</tbody>
</table>

minimum burning pressures of water-based emulsion explosives

This manuscript describes a protocol to measure the minimum pressure required for sustained burning of water-based emulsion explosives. Pumping water-based emulsion explosives for blasting applications can be very hazardous, as demonstrated by a number of pump accidents around the globe in the last decades, including some that resulted in fatalities. In Canada, the recognition of this hazard has led to the development of pumping guidelines that were endorsed by both the explosives industry and the Explosive Regulatory Division of the Canadian government. In these guidelines, it was noted that the minimum burning pressures (MBP) measured in a laboratory would provide a good guide to characterize the behaviour of these products in pumping systems. The same guidelines also call for the design of pump systems that prevent, whenever possible, pressures from exceeding the MBP of the product being pumped. At the time of publication of these guidelines, a methodology existed for measuring such MBP values but it had never been validated to measure the MBP of ammonium nitrate water-based emulsions (AWEs). AWEs are now used much more widely than any other water-based explosives and precursors in on-site bulk loading operations.
The Canadian Explosives Research Laboratory (CanmetCERL) has been conducting research over the last ten years to develop a validated testing protocol to measure and interpret representative MBP values for AWEs. The test, as it is performed today, will be described and the critical components will be justified by reference to recent published data. Results of MBP measurements, for a range of AWE products, will be presented. Inclusion of the MBP test in the test standards for the authorization of high explosives in Canada will also be discussed.

Typical raw signals from a test resulting in a fully propagated event (i.e. &#34;go&#34;) are shown in Figure 6. The ignition current (blue curve) is seen to come on at t0 = 0 and to stay on until the NiCr wire burns at tb = 19.1 s. The computed average ignition current (i.e. average of all data points between t0 and tb is Ihw = 10.59 A. On the pressure record (red curve), the first sign of clear departure from the initial baseline is observed to occur at tp0 = 17.3 s. The computed average initial pressure (i.e. average of all data points between t0 and tp0) is Pi = 4.924 MPa (700 psig). From tp0, the pressure is seen to rapidly increase to a maximum of Pmax = 6.095 MPa (870 psig) at ts = 33.7s. At this point the burning front has reached the internal wall of the cell and the pressure quickly decreases as combustion ceases.
The MBP measurement protocol presented here has been developed through a careful study of the many physical effects that can influence the outcome of the measurements. Through the publication of several documents, MBP data on a very wide variety of AWE formulations have been presented, thus establishing the usefulness and reproducibility 16 of the proposed measurement protocol.
In particular, the preponderant effect of the water content on the MBP of AWE formulations has been clearly demonstrated. This can be seen in Figure 5 showing the MBP data for five AWE formulations with water content varying between 11.7 and 24.8 mass percent (%). For these five emulsions, the oxidizer solution consisted of only ammonium nitrate and water while the oil phase (oil + surfactant) amount and composition was kept fixed. It can be observed that, for each measurement, a series of 12 to 16 tests were performed. For each measurement, the two short horizontal bars indicate the pressure interval between of the highest &#34;no-go (or partial)&#34; event and the lowest &#34;go&#34; event, as specified in the above protocol. This illustrates well the strong dependence of the MBP of these particular formulae on the water content. From Figure 5, it can also be observed that the scatter in the MBP data is much higher for the two formulae with lowest water content (EM4 and EM5). Since these formulae contained only ammonium nitrate in their oxidizer solution (no other salts), they have relatively high crystallization temperatures and, as such, may be more prone to crystallization upon manipulation. This could induce a certain degree of non-uniformity in the samples and, therefore, a more important scatter in the data.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56167/56167fig1.jpg" /> 
Figure 1: Complete ignition wire assembly. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56167/56167fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56167/56167fig2.jpg" /> 
Figure 2: Typical MBP test cell with installed ignition assembly and emulsion sample. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56167/56167fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56167/56167fig3.jpg" /> 
Figure 3: Test cell. (A) Assembled test cell just before introduction of emulsion sample through the slit. (B) View of test cell from one open end with neoprene stopper removed, showing the details of the NiCr wire running along the axis of the stainless-steel cell. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56167/56167fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/56167/56167fig4.jpg" /> 
Figure 4: Visual observations and pressure recordings. (A) Typical visual observations for a &#34;Go&#34; (left) and &#34;No-Go&#34; (right) events. (B) Typical pressure records for &#34;Go&#34; &#38; &#34;No-Go&#34; events. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56167/56167fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/56167/56167fig5.jpg" /> 
Figure 5: Summary of results for the MBP measurements of ammonium nitrate/water AWE formulae. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56167/56167fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/56167/56167fig6.jpg" /> 
Figure 6: Example of an analyzed MBP experiment. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56167/56167fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Minimum Burning Pressures of Water-based Emulsion Explosives at JoVE.com

Minimum Burning Pressures of Water-based Emulsion Explosives

We present an apparatus based on hot-wire ignition in a pressurized enclosure and an associated methodology to measure the minimum pressure required to induce sustained combustion in water-based emulsion explosives. This method improves product characterization to allow one to use them more safely during pumping and mixing operations.

This manuscript describes a protocol to measure the minimum pressure required for sustained burning of water-based emulsion explosives. Pumping ...

minimum-burning-pressures-of-water-based-emulsion-explosives

Nanyang Technological University

Research

JoVE Journal

Chemistry

8.3K Views.  Natural Resources Canada. We present an apparatus based on hot-wire ignition in a pressurized enclosure and an associated methodology to measure the minimum pressure required to induce sustained combustion in water-based emulsion explosives. This method improves product characterization to allow one to use them more safely during pumping and mixing operations.

Video: Minimum Burning Pressures of Water-based Emulsion Explosives

Determination of the Gas-phase Acidities of Oligopeptides

Amino acid residues located at different positions in folded proteins often exhibit different degrees of acidities. For example, a cysteine residue located at or near the N-terminus of a helix is often more acidic than that at or near the C-terminus 1-6. Although extensive experimental studies on the acid-base properties of peptides have been carried out in the condensed phase, in particular in aqueous solutions 6-8, the results are often complicated by solvent effects 7. In fact, most of the active sites in proteins are located near the interior region where solvent effects have been minimized 9,10. In order to understand intrinsic acid-base properties of peptides and proteins, it is important to perform the studies in a solvent-free environment.
We present a method to measure the acidities of oligopeptides in the gas-phase. We use a cysteine-containing oligopeptide, Ala3CysNH2 (A3CH), as the model compound. The measurements are based on the well-established extended Cooks kinetic method (Figure 1) 11-16. The experiments are carried out using a triple-quadrupole mass spectrometer interfaced with an electrospray ionization (ESI) ion source (Figure 2). For each peptide sample, several reference acids are selected. The reference acids are structurally similar organic compounds with known gas-phase acidities. A solution of the mixture of the peptide and a reference acid is introduced into the mass spectrometer, and a gas-phase proton-bound anionic cluster of peptide-reference acid is formed. The proton-bound cluster is mass isolated and subsequently fragmented via collision-induced dissociation (CID) experiments. The resulting fragment ion abundances are analyzed using a relationship between the acidities and the cluster ion dissociation kinetics. The gas-phase acidity of the peptide is then obtained by linear regression of the thermo-kinetic plots 17,18.
The method can be applied to a variety of molecular systems, including organic compounds, amino acids and their derivatives, oligonucleotides, and oligopeptides. By comparing the gas-phase acidities measured experimentally with those values calculated for different conformers, conformational effects on the acidities can be evaluated.

The determination of the gas-phase acidities of cysteine-containing oligopeptides is described. The experiments are performed using a triple quadrupole mass spectrometer. The relative acidities of the peptides are measured using collision-induced dissociation experiments, and the quantitative acidities are determined using the extended Cooks kinetic method.

Amino acid residues located at different positions in folded proteins often exhibit different degrees of acidities. For example, a cysteine residue ...

Formation of Ordered Biomolecular Structures by the Self-assembly of Short Peptides

In nature, complex functional structures are formed by the self-assembly of biomolecules under mild conditions. Understanding the forces that control self-assembly and mimicking this process in vitro will bring about major advances in the areas of materials science and nanotechnology. Among the available biological building blocks, peptides have several advantages as they present substantial diversity, their synthesis in large scale is straightforward, and they can easily be modified with biological and chemical entities1,2. Several classes of designed peptides such as cyclic peptides, amphiphile peptides and peptide-conjugates self-assemble into ordered structures in solution. Homoaromatic dipeptides, are a class of short self-assembled peptides that contain all the molecular information needed to form ordered structures such as nanotubes, spheres and fibrils3-8. A large variety of these peptides is commercially available.
This paper presents a procedure that leads to the formation of ordered structures by the self-assembly of homoaromatic peptides. The protocol requires only commercial reagents and basic laboratory equipment. In addition, the paper describes some of the methods available for the characterization of peptide-based assemblies. These methods include electron and atomic force microscopy and Fourier-Transform Infrared Spectroscopy (FT-IR). Moreover, the manuscript demonstrates the blending of peptides (coassembly) and the formation of a &#34;beads on a string&#34;-like structure by this process.9 The protocols presented here can be adapted to other classes of peptides or biological building blocks and can potentially lead to the discovery of new peptide-based structures and to better control of their assembly.

This paper describes the formation of highly ordered peptide-based structures by the spontaneous process of self-assembly. The method utilizes commercially available peptides and common lab equipment. This technique can be applied to a large variety of peptides and may lead to the discovery of new peptide-based assemblies.

In nature, complex functional structures are formed by the self-assembly of biomolecules under mild conditions. Understanding the forces that control ...

Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia

Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high surface area microporous materials, such as metal-organic frameworks (MOFs), unique challenges present themselves for PECVD treatments. Herein the protocol for development of a MOF that was previously unstable to humid conditions is presented. The protocol describes the synthesis of Cu-BTC (also known as HKUST-1), the treatment of Cu-BTC with PECVD of perfluoroalkanes, the aging of materials under humid conditions, and the subsequent ammonia microbreakthrough experiments on milligram quantities of microporous materials. Cu-BTC has an extremely high surface area (~1,800 m2/g) when compared to most materials or surfaces that have been previously treated by PECVD methods. Parameters such as chamber pressure and treatment time are extremely important to ensure the perfluoroalkane plasma penetrates to and reacts with the inner MOF surfaces. Furthermore, the protocol for ammonia microbreakthrough experiments set forth here can be utilized for a variety of test gases and microporous materials.

Herein the procedures for plasma enhanced chemical vapor deposition of perfluoroalkanes on microporous materials such as metal-organic frameworks to enhance their stability and hydrophobicity are described. Furthermore, breakthrough testing of milligram quantities of samples is described in detail.

Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high ...

Synthesis of Indoxyl-glycosides for Detection of Glycosidase Activities

Indoxyl glycosides proved to be valuable and versatile tools for monitoring glycosidase activities. Indoxyls are released by enzymatic hydrolysis and are rapidly oxidized, for example by atmospheric oxygen, to indigo type dyes. This reaction enables fast and easy screening in vivo without isolation or purification of enzymes, as well as rapid tests on agar plates or in solution (e.g., blue-white screening, micro-wells) and is used in biochemistry, histochemistry, bacteriology and molecular biology. Unfortunately the synthesis of such substrates proved to be difficult, due to various side reactions and the low reactivity of the indoxyl hydroxyl function. Especially for glucose type structures low yields were observed. Our novel approach employs indoxylic acid ester as key intermediates. Indoxylic acid esters with varied substitution patterns were prepared on scalable pathways. Phase transfer glycosylations with those acceptors and peracetylated glycosyl halides can be performed under common conditions in high yields. Ester cleavage and subsequent mild silver mediated glycosylation yields the peracetylated indoxyl glycosides in high yields. Finally deprotection is performed according to Zempl&#233;n.

Indoxyl glycosides are well-established and widely used tools for enzyme screening and enzyme activity monitoring. Especially for glucose type structures previous syntheses proved to be challenging and low yielding. Our novel approach employs indoxylic acid esters as precious intermediates to yield a considerable number of indoxyl glycosides in good yields.

Indoxyl glycosides proved to be valuable and versatile tools for monitoring glycosidase activities. Indoxyls are released by enzymatic hydrolysis and are ...

Visualization of Ambient Mass Spectrometry with the Use of Schlieren Photography

This manuscript outlines how to visualize mass spectrometry ambient ionization sources using schlieren photography. In order to properly optimize the mass spectrometer, it is necessary to characterize and understand the physical principles of the source. Most commercial ambient ionization sources utilize jets of nitrogen, helium, or atmospheric air to facilitate the ionization of the analyte. As a consequence, schlieren photography can be used to visualize the gas streams by exploiting the differences in refractive index between the streams and ambient air for visualization in real time. The basic setup requires a camera, mirror, flashlight, and razor blade. When properly configured, a real time image of the source is observed by watching its reflection. This allows for insight into the mechanism of action in the source, and pathways to its optimization can be elucidated. Light is shed on an otherwise invisible situation.

This paper presents a protocol for the visualization of gaseous streams of an ambient ionization source using schlieren photography and mass spectrometry.

This manuscript outlines how to visualize mass spectrometry ambient ionization sources using schlieren photography. In order to properly optimize the mass ...

Preparation of Hollow Polystyrene Particles and Microcapsules by Radical Polymerization of Janus Droplets Consisting of Hydrocarbon and Fluorocarbon Oils

In this article, we have demonstrated a method for producing hollow particles and microcapsules using oil droplets consisting of hydrocarbon oil (styrene) and fluorocarbon oil (perfluoro-n-octane, PFO) in aqueous surfactant (sodium dodecylsulfate, SDS) solutions. Since fluorocarbon oils are immiscible with hydrocarbon oils, the two oils are separated. Emulsions are prepared by stirring styrene/PFO/aqueous SDS solution mixtures at 80 &#176;C. The type of emulsions and the morphology of droplets in the emulsions are observed by light microscope and scanning confocal fluorescence microscope. It is found that oil droplets with Janus-type morphologies consisting of mutually immiscible styrene and PFO are formed in aqueous SDS solutions. Polystyrene particles are fabricated by radical polymerization of the ternary mixtures of styrene/PFO/aqueous SDS solution at 80 &#176;C. The morphologies of the polystyrene are confirmed by scanning electron microscopy and scanning transmission electron microscopy observations. These observations show the preparation of hollow polystyrene particles with a single hole on the surface. To our knowledge, this method is a novel strategy using the immiscibility of hydrocarbon and fluorocarbon oils. The hollow particles can also be applied to the preparation of microcapsules.

A protocol for the fabrication of hollow polymer particles and microcapsules by radical polymerization using emulsions consisting of styrene, perfluoro-n-octane, and aqueous SDS (sodium dodecylsulfate) solution is presented.

In this article, we have demonstrated a method for producing hollow particles and microcapsules using oil droplets consisting of hydrocarbon oil (styrene) ...

Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F&#8722;

Anion photoelectron imaging is a very efficient method for the study of energy states of bound negative ions, neutral species and interactions of unbound electrons with neutral molecules/atoms. State-of-the-art in vacuo anion generation techniques allow application to a broad range of atomic, molecular, and cluster anion systems. These are separated and selected using time-of-flight mass spectrometry. Electrons are removed by linearly polarized photons (photo detachment) using table-top laser sources which provide ready access to excitation energies from the infra-red to the near ultraviolet. Detecting the photoelectrons with a velocity mapped imaging lens and position sensitive detector means that, in principle, every photoelectron reaches the detector and the detection efficiency is uniform for all kinetic energies. Photoelectron spectra extracted from the images via mathematical reconstruction using an inverse Abel transformation reveal details of the anion internal energy state distribution and the resultant neutral energy states. At low electron kinetic energy, typical resolution is sufficient to reveal energy level differences on the order of a few millielectron-volts, i.e., different vibrational levels for molecular species or spin-orbit splitting in atoms. Photoelectron angular distributions extracted from the inverse Abel transformation represent the signatures of the bound electron orbital, allowing more detailed probing of electronic structure. The spectra and angular distributions also encode details of the interactions between the outgoing electron and the residual neutral species subsequent to excitation. The technique is illustrated by the application to an atomic anion (F&#8722;), but it can also be applied to the measurement of molecular anion spectroscopy, the study of low lying anion resonances (as an alternative to scattering experiments) and femtosecond (fs) time resolved studies of the dynamic evolution of anions.

Here, we present a protocol for photoelectron imaging of anionic species. Anions generated in vacuo and separated by mass spectrometry are probed using velocity mapped photoelectron imaging, providing details of anion and neutral energy levels, anion and neutral structure and the nature of the anion electronic state.

Anion photoelectron imaging is a very efficient method for the study of energy states of bound negative ions, neutral species and interactions of unbound ...

Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source

Herein is presented a general strategy to perform reactions under mild to moderate CO2 pressures with dry ice. This technique obviates the need for specialized equipment to achieve modest pressures, and can even be used to achieve higher pressures in more specialized equipment and sturdier reaction vessels. At the end of the reaction, the vials can be easily depressurized by opening at room temperature. In the present example CO2 serves as both a putative directing group as well as a way to passivate amine substrates, thereby preventing oxidation during the organometallic reaction. In addition to being easily added, the directing group is also removed under vacuum, obviating the need for extensive purification to remove the directing group. This strategy allows the facile &#947;-C(sp3)-H arylation of aliphatic amines and has the potential to be applied to a variety of other amine-based reactions.

Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source

Here we present a protocol for performing reactions in simple reaction vessels under low-to-moderate pressures of CO2. The reactions can be performed in a variety of vessels simply by administering the carbon dioxide in the form of dry ice, without the need for costly or elaborate equipment or set-ups.

Herein is presented a general strategy to perform reactions under mild to moderate CO2 pressures with dry ice. This technique obviates the need for ...

Bio-inspired Polydopamine Surface Modification of Nanodiamonds and Its Reduction of Silver Nanoparticles

Surface functionalization of nanodiamonds (NDs) is still challenging due to the diversity of functional groups on the ND surfaces. Here, we demonstrate a simple protocol for the multifunctional surface modification of NDs by using mussel-inspired polydopamine (PDA) coating. In addition, the functional layer of PDA on NDs could serve as a reducing agent to synthesize and stabilize metal nanoparticles. Dopamine (DA) can self-polymerize and spontaneously form PDA layers on ND surfaces if the NDs and dopamine are simply mixed together. The thickness of a PDA layer is controlled by varying the concentration of DA. A typical result shows that a thickness of ~5 to ~15 nm of the PDA layer can be reached by adding 50 to 100 &#181;g/mL of DA to 100 nm ND suspensions. Furthermore, the PDA-NDs are used as a substrate to reduce metal ions, such as Ag[(NH3)2]+, to silver nanoparticles (AgNPs). The sizes of the AgNPs rely on the initial concentrations of Ag[(NH3)2]+. Along with an increase in the concentration of Ag[(NH3)2]+, the number of NPs increases, as well as the diameters of the NPs. In summary, this study not only presents a facile method for modifying the surfaces of NDs with PDA, but also demonstrates the enhanced functionality of NDs by anchoring various species of interest (such as AgNPs) for advanced applications.

A facile protocol is presented to functionalize the surfaces of nanodiamonds with polydopamine.

Surface functionalization of nanodiamonds (NDs) is still challenging due to the diversity of functional groups on the ND surfaces. Here, we demonstrate a ...

Enzymatic Synthesis of Epoxidized Metabolites of Docosahexaenoic, Eicosapentaenoic, and Arachidonic Acids

The epoxidized metabolites of various polyunsaturated fatty acids (PUFAs), termed epoxy fatty acids, have a wide range of roles in human physiology. These metabolites are produced endogenously by the cytochrome P450 class of enzymes. Because of their diverse and potent biological effects, there is considerable interest in studying these metabolites. Determining the unique roles of these metabolites in the body is a difficult task, as the epoxy fatty acids must first be obtained in significant amounts and with high purity. Obtaining compounds from natural sources is often labor intensive, and soluble epoxide hydrolases (sEH) rapidly hydrolyze the metabolites. On the other hand, obtaining these metabolites via chemical reactions is very inefficient, due to the difficulty of obtaining pure regioisomers and enantiomers, low yields, and extensive (and expensive) purification. Here, we present an efficient enzymatic synthesis of 19(S),20(R)- and 16(S),17(R)-epoxydocosapentaenoic acids (EDPs) from DHA via epoxidation with BM3, a bacterial CYP450 enzyme isolated originally from Bacillus megaterium (that is readily expressed in Escherichia coli). Characterization and determination of purity is performed with nuclear magnetic resonance spectroscopy (NMR), high-performance liquid chromatography (HPLC), and mass spectrometry (MS). This procedure illustrates the benefits of enzymatic synthesis of PUFA epoxy metabolites, and is applicable to the epoxidation of other fatty acids, including arachidonic acid (AA) and eicosapentaenoic acid (EPA) to produce the analogous epoxyeicosatrienoic acids (EETs) and epoxyeicosatetraenoic acids (EEQs), respectively.

We present a method useful for large-scale enzymatic synthesis and purification of specific enantiomers and regioisomers of epoxides of arachidonic acid (AA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA) with the use of a bacterial cytochrome P450 enzyme (BM3).

The epoxidized metabolites of various polyunsaturated fatty acids (PUFAs), termed epoxy fatty acids, have a wide range of roles in human physiology. These ...