Patent Application
20160077178
This disclosure relates to nuclear quadrupole resonance (NQR) and, more particularly, to using nuclear quadrupole resonance (NQR) for determining properties of substances.
Nuclear quadrupole resonance (NQR) is a phenomenon where certain atomic nuclei generate resonant signals when an oscillating magnetic field at a particular frequency is applied to the nuclei. Some atomic nuclei can generate resonant signals responsive to two or more different applied frequencies. The NQR resonant signals can be detected without an externally applied magnetic field. Different atomic nuclei will have different resonant frequencies. For example, the resonant frequencies of nitrogen are different from the resonant frequencies of chlorine. Also, atomic nuclei of the same chemical element that are located within different chemical species can have different resonant frequencies. For example, the nitrogen nuclei located within the ammonium nitrate will have different resonant frequencies from nitrogen nuclei located within RDX. Furthermore, atomic nuclei of the same chemical element that are located within different sites of a chemical species can also have different resonant frequencies. Such NQR phenomena can be used to determine properties of a substance.
Illustrative embodiments of the present disclosure are directed to a method for identifying chemical species within a substance using nuclear quadrupole resonance (NQR). The method includes applying a number of NQR perturbation-detection pulse sequences to the substance. Each perturbation-detection pulse sequence includes a perturbation segment applied at a perturbation frequency and a detection segment applied at a second different frequency. As the sequences are applied, the perturbation frequency, the second frequency, or both are varied for each pulse sequence. The method also includes applying a number of NQR reference pulse sequences to the substance. Each reference pulse sequence is applied at a reference frequency, which is varied for each pulse sequence. A perturbation-detection set of NQR signals are generated within the substance by each of the perturbation-detection pulse sequences. The perturbation-detection set of NQR signals is detected. Also, a reference set of NQR signals generated within the substance by each of the reference pulse sequences is detected. A chemical species is identified within the substance by comparing the perturbation-detection set of NQR signals and the reference set of NQR signals.
In various embodiments, identifying the chemical species within the substance includes using the set of perturbation-detection NQR signals to generate a two-dimensional spectrum of the perturbation frequency versus the second frequency and using the reference set of NQR signals to generate a reference spectrum for the reference frequency. The two-dimensional spectrum is compared to the reference spectrum to identify the chemical species within the substance.
In some embodiments, comparing the two-dimensional spectrum to the reference spectrum includes generating a difference spectrum using the two-dimensional spectrum and the reference spectrum. Peaks are identified within the difference spectrum. The particular frequencies associated with these peaks can be used to identify the chemical species within the substance.
Various embodiments are also directed to a NQR system for identifying chemical species within a substance. The system includes one or more coils for applying NQR pulse sequences to a substance and for detecting NQR signals generated within the substance. A NQR transmitter is electronically coupled to the coil and generates NQR pulse sequences that are transmitted to the coil. A NQR receiver is coupled to the coil and processes detected NQR signals. The system also includes a processor and a memory that stores instructions executable by the processor to perform various processes. The processes include providing a number of NQR perturbation-detection pulse sequences to the NQR transmitter. Each perturbation-detection pulse sequence includes a perturbation segment at a perturbation frequency and a detection segment at a second different frequency. The perturbation frequency, the second frequency, or both are varied for each pulse sequence. The processes also include providing a number of NQR reference pulse sequences to the NQR transmitter. The reference pulse sequences are applied at a reference frequency that is varied for each pulse sequence. The processes further include receiving (i) a perturbation-detection set of NQR signals generated within the substance by each of the perturbation-detection pulse sequences and (ii) a reference set of NQR signals generated within the substance by each of the reference pulse sequences. A chemical species is identified within the substance by comparing the perturbation-detection set of NQR signals and the reference set of NQR signals.
Further features and advantages will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings:
Illustrative embodiments are directed to methods and systems for identifying chemical species within an unknown substance using nuclear quadrupole resonance (NQR). One method includes applying a number of NQR perturbation-detection pulse sequences to the substance. Each perturbation-detection pulse sequence includes a perturbation segment applied at a perturbation frequency and a detection segment applied at a second different frequency. As the sequences are applied, the perturbation frequency, the second frequency, or both are varied for each pulse sequence. The method also includes applying a number of NQR reference pulse sequences to the substance. The reference pulse sequences are applied at a reference frequency that is varied for each pulse sequence. A perturbation-detection set of NQR signals is generated within the substance by each of the perturbation-detection pulse sequences. The perturbation-detection set of NQR signals are detected. Also, a reference set of NQR signals generated within the substance by each of the reference pulse sequences is detected. A chemical species is identified within the substance by comparing the perturbation-detection set of NQR signals and the reference set of NQR signals. In this manner, some embodiments of the present disclosure “scan” across many different NQR frequencies to efficiently and accurately identify chemical species within an unknown sample. Details of illustrative embodiments are described below.
Various embodiments of the present disclosure use NQR pulse sequences with perturbation segments. The perturbation segments can be used to improve the accuracy of NQR measurements and determinations.
In various embodiments of the present disclosure, the NQR perturbation-detection sequence 10 can improve the accuracy of NQR measurements and determinations by modulating the populations of energy levels of atomic nuclei at a particular site within a chemical species.
In various embodiments of the present disclosure, the NQR perturbation-detection sequences can be used with other NQR sequences to improve the accuracy of NQR measurements and determinations by identifying the presence of a particular atomic nuclei of interest. For example, a reference NQR pulse sequence, such as an SLSE sequence, is applied to a substance with a frequency (ω1). The frequency (ω1) may match a known resonant frequency (ω0) of a set of atomic nuclei of interest within a chemical species. A reference resonant signal produced by the reference sequence is detected.
Illustrative embodiments of the present disclosure are not limited to using ω0 as the perturbation frequency (ω1) and ω+ as the second frequency (ω2). Many different combinations of known resonant frequencies (e.g., ω0, ω+, and ω−) can achieve similar results. For example, in some cases, the resonant frequencies may produce a resonant signal with amplitude that increases, as compared with the reference resonant signal. Table 1 below shows amplitude changes for various known resonant frequencies.
The perturbation-detection sequences and methods described above can be applied to a substance in order to identify particular chemical species within the substance. Various embodiments described herein are directed to a method that identifies chemical species within the substance (e.g., sample) when the chemical species within the substance are unknown. Details of this method are further described below.
At process 406, the method includes applying a number of NQR reference pulse sequences to the substance. The reference pulse sequences are applied at a reference frequency that is varied for each pulse sequence. In some embodiments, the reference pulse sequence is a SLSE or a SSFP sequence without a perturbation segment. At process 408, a reference set of NQR signals is detected. The reference set of NQR signals is generated within the substance by each of the reference pulse sequences. The reference set of NQR signals are obtained without using a perturbation-detection sequence. In some embodiments, the reference frequency is varied over the same set of frequencies as the second frequency in the perturbation-detection sequence. Processes 406 and 408 can be performed in the following manner to scan across a range of different reference frequencies.
The perturbation-detection sequences and reference sequences described herein can be more efficiently applied by interposing sequences within one another. For example, in some embodiments, at least one NQR perturbation-detection pulse sequence is at least partially interposed within another perturbation-detection sequence. In this manner, NQR measurements can be performed in parallel to more efficiently make measurements, whereas in many conventional systems, the measurements are performed in series.
As shown in
In various embodiments of the present disclosure, the first sequence 102 may match at least one resonant frequency of a first set of atomic nuclei (e.g., a first site of nitrogen in TNT at 842 kHz) and the second segment 104 may match at least one resonant frequency of a second set of atomic nuclei (e.g., a second site of nitrogen in TNT at 768 kHz). In this manner, the first sequence 102 generates a first resonant signal in the first set of nuclei and the second sequence 104 generates a second resonant signal in the second set of nuclei.
In a specific example, the interposed pulse sequences are perturbation-detection sequences. In such an embodiment, the sequences 102, 104 may include four different frequencies. The first sequence 102 includes a first perturbation frequency for the perturbation segment and a second frequency for the detection segment, while the second sequence 104 includes a third perturbation frequency for the perturbation segment and a fourth frequency for the detection segment. In another example, if four perturbation-detection sequences are applied, then the entire resulting sequence may include eight different frequencies.
The interposed pulse sequences (e.g., perturbation-detection or reference sequences) can be applied using a non-resonant transmitter, such as the non-resonant transmitter described below. Further details regarding interposed sequences can be found in U.S. Publication No. 2012/0001629 published on Jan. 5, 2012, and PCT Publication No. WO 2013/134474, published on Sep. 12, 2013. Both of these references are incorporated herein, in their entireties, by reference.
Referring back to
S
d(ω1,ω2)=sign[S(ω1,ω2)−S0(ω2)] (1)
Equation 2 below can be used to determine a normalized difference spectrum:
S
d(ω1,ω2)=S(ω1,ω2)/S0(ω2)−1 (2)
A threshold can also be applied to the difference spectrum at an appropriate level in order to identify coupling between NQR lines. Differences between S(ω1,ω2) and S0(ω2) that are smaller than the threshold are ignored, i.e., the corresponding values in the difference spectrum Sd(ω1,ω2) are set to zero. The value of this threshold is designed to be high enough to remove random differences between S(ω1,ω2) and S0(ω2) due to noise, but low enough to allow systematic differences due to coupling between NQR lines to be retained and easily identified.
The positive and negative peaks within the difference spectrum can then be used to identify a chemical species by comparing the frequencies associated with the positive and negative peaks with the spectral lines of the chemical species, such as those chemical species shown in Table 2 below.
Sub-processes (A)-(H) described above are not limited to this particular order. For example, in another embodiment, sub-processes (F)-(H) can take place before sub-processes (A)-(E). In other words, processes 406 and 408 can take place before processes 402 and 404. To this end, in various embodiments, the reference spectrum generated using the reference frequencies (ω3) can be used to inform selection of the perturbation frequency associated with the perturbation segment and the second frequency associated with the detection segment. For example, a number of NQR reference pulse sequences are applied to the substance. Each reference pulse sequence is applied at a reference frequency that is varied for each pulse sequence. A reference set of NQR signals generated within the substance by each of the reference pulse sequences is detected. The NQR signals generated within the substance by the series of NQR pulse sequences are detected and used to generate a one-dimensional reference spectrum for the first frequency. A number of peaks are identified within the one-dimensional reference spectrum. Then, the perturbation-detection pulse sequences are applied to the substance. The perturbation frequency and the second frequency within the perturbation-detection pulse sequences can be selected to match frequencies associated with the identified peaks in the reference spectrum (e.g., ωa, ωb, ωc). Thus, each perturbation-detection pulse sequence includes a perturbation frequency associated with one of the identified peaks and a detection segment associated with one of the identified peaks (e.g., a first pulse sequence using ωb and ωa, a second pulse sequence using ωc and ωa, a third pulse sequence using ωa and ωb, a fourth pulse sequence using ωc and ωb, and . . . ).
The NQR signals generated within the substance by the perturbation-detection pulse sequences are detected and chemical species within the substance can be identified using the detected NQR signals. If a particular perturbation-detection pulse sequence produces a decrease or an increase in amplitude for an identified peak, then the frequencies (e.g., lines) for that particular sequence are coupled. For example, if a pulse sequence includes a perturbation segment with a frequency of ωa and a detection segment with a frequency of ωb, and the amplitude of the resonant signal produced by this pulse sequence is larger than the initial amplitude at ωb, then the ωa and the ωb lines are coupled and this coupling can be used to identify a site within the chemical species.
In one specific example, coupling between three NQR lines was determined by running SLSE experiments for possible pairs of lines, and comparing the resultant amplitudes with a reference case (e.g., perturbation pulse switched off). This approach is faster than running a full two-dimensional scan because a smaller set of experiments can be performed (e.g., a total of six SLSE experiments on the three lines). In general, this approach performs N(N−1) SLSE experiments on N lines.
The methods described herein can be used to identify various different chemical species. The chemical species can be a single chemical element, such as nitrogen, chlorine, potassium, and copper, or a chemical compound that includes any one of those atomic nuclei, such as glycine, ammonium nitrate, TNT (2,4,6-trinitrotoluene), RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), cocaine hydro-chloride, and/or heroin hydro-chloride (3,6-diacetoxy-7,8-dehydro-4,5-epoxy-N-methylmorphinan hydrochloride monohydrate). Table 2 shows the spectral lines for nitrogen, potassium, and chlorine at each site within several chemical species. The column headings are described below.
“Chemical Species” is a particular chemical species of interest;
“Site #” is a position of an atomic nucleus within a particular chemical species;
“Type” is an atomic nucleus at a site (e.g., chemical element and isotope);
“Weight %” is a contribution of a site to a total weight of a molecule of a chemical species;
“QCC” is a quadrupole coupling constant for a site;
“η” is a symmetry parameter for a site;
“NQR Frequency” is a known resonant frequency of an atomic nucleus within a particular site within a chemical species;
“FWHM” is an NQR line width for a particular NQR frequency (full-width at half-maximum);
“T1” is a T1 relaxation time for an atomic nucleus at a particular site;
“T2” is a T2 relaxation time for an atomic nucleus at a particular site; and
“dv/dT” is a temperature coefficient for a particular NQR frequency.
39K
15Cl
Illustrative embodiments described herein are not limited to detecting the chemical species described in Table 2. The chemical species presented in Table 2 are presented as non-limiting examples.
Further examples of two-dimensional NQR experiments are described herein. In these experiments, the frequency of the perturbation pulse is referred to as (18 in
Table 3 below shows the measured amplitude changes (in percent) for each line. The table clearly shows that line 2 is not coupled to lines 1 and 3. However, lines 1 and 3 are coupled to each other. Moreover, the fact that the amplitude changes related to lines 1 and 3 are negative confirms that these correspond to the ω− and ω+ transitions of a single site (see Table 1). These results confirm that lines 1 and 3 are the ω− and ω+ transitions of glycine, while line 2 is the ω0 transition of sodium nitrite.
Table 3 was generated by applying perturbation-detection sequences at each pair of lines. In each case the flip angle of the perturbation pulse was fixed at 257 degrees, while that of the detection pulses was fixed at 120 degrees. The uncertainties correspond to one standard deviation.
It should also be noted that there is a statistically substantial decrease in amplitude (26.1%) when the signal detected at line 1 is perturbed by a pulse at line 2, even though lines 1 and 2 are not coupled to each other. This is because the frequencies of lines 2 and 3 are separated by only 15 kHz, which is comparable to the bandwidth of the initial pulse.
The NQR transmitter 1404 includes a NQR transmitter circuit 1410 that is coupled to the coil 1402. The transmitter circuit 1410 generates NQR pulse sequences and provides the NQR pulse sequences to the coil 1402. The NQR pulse sequences can be any of the NQR sequences described herein (e.g., multi-segment sequences, an interposed pulse sequences, SLSE sequences, and/or perturbation-detection sequences).
In some embodiments, the NMR transmitter 1404 uses a “tuned” NMR transmitter circuit 1410. A tuned NMR transmitter is tuned to a particular Larmor frequency using a capacitor that is coupled to the coil. The particular capacitance of the capacitor and the inductance of the coil determine the resonant frequency that is generated by the coil.
In other embodiments, a non-resonant transmitter circuit 1410 can be used to more effectively and efficiently apply the pulses described herein (e.g., the interposed sequences and the perturbation-detection sequences). A non-resonant transmitter circuit is “non-resonant” because the resonant frequency of the circuit does not need to match the Larmor frequency of interest. Although the non-resonant transmitter circuit and coil 1402 may use capacitors and have some associated capacitance, this capacitance is not specifically selected to match a Larmor frequency of interest. Instead, the transmitter circuit includes a plurality of switches that couple and decouple the coil 1402 with a power source. Operation of the switches generates a particular frequency. Thus, the frequency produced by the transmitter circuit can be modulated directly by a spectrometer. In some cases, the NQR transmitter 1404 (and the coil 1402) can switch between frequencies with a frequency difference as great as 10% of an initial applied frequency. In various other embodiments, the frequency can be even greater (e.g., 20% 30% or 50%). Also, in some embodiments, the NQR transmitter 1404 can switch between frequencies in less than 5 μs. In yet further embodiments, the NQR transmitter 1404 can switch between frequencies in less than 20 μs or 50 μs. Furthermore, in some embodiments, the NQR transmitter 1404 can operate within a frequency range of 50 kHz to 10 MHz.
Further details regarding non-resonant transmitters are provided in U.S. Publication No. 2012/0001629 published on Jan. 5, 2012; U.S. application Ser. No. 13/774,457, filed on Feb. 22, 2013, and U.S. patent application Ser. No. 13/963,826, filed on Aug. 9, 2013. These references are incorporated by reference in their entireties.
As shown in
The NQR system also includes a spectrometer 1408 that is used to provide NQR pulse sequences to the NQR transmitter 1404 and to analyze the NQR signal received from the NQR receiver 1406. In various embodiments, the detected NQR signal is output by the NQR receiver 1406 in analog form. In such embodiments, the spectrometer 1408 may include a digitizer 1420 (e.g., analog-to-digital converter) for converting the detected NQR signal into digital data. Furthermore, in various embodiments, demodulation of the NQR signal can occur within the spectrometer 1408. In various other embodiments, however, demodulation of the NQR signal can also occur within the NQR receiver 1406. The spectrometer 1416 also includes a post-processor 1422 that is used to interpret the detected digital NQR data and to determine NQR properties from the detected data. This data can be presented to a user using an operator interface with a graphical user interface (GUI). The spectrometer 1408 also includes a pulse sequence generator 1424 that generates NQR pulse sequences based upon parameters selected by an operator at the operator interface. The pulse sequence generator provides the sequences to the NQR transmitter 1404. In one particular embodiment, the spectrometer 1408 is a KEA™, which can be obtained from Magritek of Wellington, New Zealand. The spectrometer 1408 can be controlled from the operator interface using PROSPA™ software, which can also be obtained from Magritek.
Further details of NQR electronics, NQR transmitters, non-resonant transmitter circuits, and NQR receivers are described in U.S. Publication No. 2012/0001629 published on Jan. 5, 2012, and PCT Publication No. WO 2013/134474, published on Sep. 12, 2013. Both of these references are incorporated herein, in their entireties, by reference.
As shown in
The NQR system 1400 also includes an operator interface 1428 for communicating with the spectrometer 1408. The operator interface 1428 includes a computer system. The computer system may include a computer processor 1430 (e.g., a microprocessor, microcontroller, digital signal processor, or general purpose computer) for executing any of the methods and processes described herein. The computer system may further include a memory 1432 such as a semiconductor memory device (e.g., a RAM, ROM, PROM, EEPROM, or Flash-Programmable RAM), a magnetic memory device (e.g., a diskette or fixed disk), an optical memory device (e.g., a CD-ROM), a PC card (e.g., PCMCIA card), or other memory device. The memory 1432 can be used to store computer instructions (e.g., computer program code) that are interpreted and executed by the processor 1430.
NQR pulse sequences may be implemented as a series of computer instructions (e.g., software or firmware) fixed on a non-transitory tangible medium, such as a computer readable medium (e.g., a memory), or transmittable to the computer system, via a modem or other interface device, such as a communications adapter connected to a network over a tangible medium (e.g., optical or analog communications lines). The series of computer instructions can embody all or part of the NQR pulse sequences described herein. The processor 1430 may be configured to retrieve the sequences from the memory 1432 and provide instructions to the NQR electronics 1404, 1406, 1408 to apply the sequences to the substance 1401. The detected resonant signals may also be communicated from the NQR electronics 1404, 1406, 1408 to the processor 1430 for storage on the memory 1432.
The NQR system 1400 may also include a temperature sensor (not shown) within or adjacent to the sample 1401 and coupled to the operator interface 1428 so that the NQR system 1400 can correctly determine resonant frequencies of atomic nuclei in an environment with dynamic temperatures. Many NQR transition frequencies are affected by temperature.
The operator interface 1428 also supports the graphical user interface 1434 (GUI) (e.g., a monitor, a touch screen, a mouse, a keyboard and/or a joystick). The GUI 1434 allows an operator to control and communicate with the NQR electronics 1404, 1406, 1408. In various embodiments, the operator interface 1428 can be used to perform functions selected from the following non-limiting list:
In various embodiments, the NQR electronics 1404, 1406, 1408 and the operator interface 1428 are physically located in the same place as a single system. This may be the case when the system is used in a surface environment, such as a building or laboratory (e.g., a bomb detection system or a drug detection system).
Illustrative embodiments of the present disclosure are not limited to the NQR system 1400 shown in
Furthermore, in various embodiments, the NQR system 1400 can operate between an NQR mode and a NMR mode. In other words, the NQR system can apply both NQR pulse sequences and NMR pulse sequences to a substance of interest.
Various embodiments of the present disclosure have application in non-invasive detection of chemical species. In various embodiments, the NQR system, NQR methods (e.g., generating difference spectrums), and NQR sequences (e.g., interposed sequences, SLSE sequences, reference sequences, and/or perturbation-detection sequences) described herein can be used for detection of explosives, such as ammonium nitrate, TNT, and/or RDX. In one example, the NQR system is used to detect explosives concealed in luggage at airports or border crossings. In another example, the NQR system is used to detect landmines in a battlefield environment. In further embodiments, the NQR system and NQR sequences described herein can be used for detection of illegal drug detection, such as heroin hydro-chloride and/or cocaine hydro-chloride. Various embodiments described herein can also be used for detecting counterfeit or adulterated versions of legal drugs, such as metformin and paracetamol.
Illustrative embodiments of the present disclosure are also directed to oil and gas field applications. For example, in one specific example, the NQR system and NQR sequences described herein can be used to detect and determine the composition of kerogen. Kerogen contains nitrogen which can be detected according to the illustrative embodiments described herein. Kerogen is a solid mixture of organic chemical compounds that make up a portion of the organic matter in sedimentary rocks. Oil shale, an organic-rich fine-grained sedimentary rock, contains significant amounts of kerogen, from which liquid hydrocarbons called shale oil can be produced. Kerogen is a mixture of organic materials, rather than a specific chemical, and therefore does not have a unique chemical formula. The chemical composition of kerogen can vary distinctively from sample to sample. As an example, kerogen from the Green River Formation oil shale deposit of western North America contains elements in the following proportions: carbon 215:hydrogen 330:oxygen 12:nitrogen 5:sulfur 1. Thus, the fraction of nitrogen by weight is 5/563=0.89% in this case. However, analysis of a variety of other kerogen samples shows that this fraction can vary between 0.8% and 2%. Oil shale contains a lower percentage of organic matter than coal. In commercial grades of oil shale, the ratio of organic matter to mineral matter lies approximately between 0.75:5 and 1.5:5 (13% and 23%). Thus, the fraction of nitrogen in oil shale ranges from 0.12% to 0.46% (approximately 1 in 800 to 1 in 200). The resultant NQR resonant frequencies for shales can be determined by identifying where so-called “quadrupole dips” occur in measurements of biological samples using field cycling NMR spectrometers. A quadrupole dip is a reduction in proton T1 relaxation time (e.g., 10%-15% reduction) due to cross-relaxation between protons and adjacent nitrogen atoms in proteins and amino acids. These dips can be centered at 650 kHz, 2.1 MHz, and 2.75 MHz. An NQR oil and gas field tool is described below.
As shown in
The NQR logging module 1514 also includes at least one coil 1524 and NQR electronics 1526 electronically coupled to the coil. The coil 1516 and NQR electronics 1526 apply an oscillating field to an area of interest 1528 within the earth formation 1504. The area of interest 1502 may be located within the sensitivity zone 1522 of the electro-magnetic device 1520 (if the device is used). In accordance with exemplary embodiments of the present disclosure, the oscillating field applied to the earth formation 1504 includes any of the NQR sequences described herein (e.g., interposed sequences, SLSE sequences, reference sequences, and/or perturbation-detection sequences). The oscillating field generates NQR signals within the area of interest 1528. These NQR signals are detected by the coil 1524. The detected NQR signals are used to determine characteristics of the substance 1502 within the area of interest 1528.
The wireline system 1500 includes surface equipment 1530 for supporting the wireline tool 1508 within the wellbore 1506. In various embodiments, the surface equipment 1530 includes a power supply for providing electrical power to the wireline tool 1508. The surface equipment 1530 also includes an operator interface for communicating with the NQR logging module 1514. Such an operator interface has already been described with reference to
The method and systems described herein are not limited to any particular wellbore application. The NQR systems and methods described herein can be used with wireline systems, such as the one shown in
Although several example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from the scope of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure.
The present application claims the benefit of U.S. Application Ser. No. 61/819,374, filed May 3, 2013, which application is incorporated herein, in its entirety, by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US14/36286 | 5/1/2014 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61819374 | May 2013 | US |
