Soil carbon mapping is extremely useful in assessing the effect of land management practices on soil carbon storage. Applications of neutron-gamma analysis in scanning mode for mapping of soil carbon are discussed. A Global Positioning System (GPS) device and softwares required to simultaneously acquire gamma signals and geographical positions during scanning operations were added to an existing measurement system. The reliability of soil carbon measurements in scanning mode was demonstrated to be in agreement with results acquired from static mode. The error analysis indicated that scanning measurements can be conducted with the same accuracy as static measurements in approximately one fourth the time. To obtain results suitable for mapping analogous to traditional chemical analyses (i.e., ± 0.5 in weight percent or ± 0.5 w%), scanning time over a given site should be ca. 15 min using the current measurement system configuration. Based on this measurement time, a reasonable towing speed of 3–5 km h–1, the necessity for complete site coverage during scanning, the number of sites (within the surveyed field), and the required total measurement time can be estimated. Soil carbon measurements for 28 field sites (total area ca. 2.5 ha) were conducted in ca. 8 h. Based on acquired data, a soil carbon distribution map was constructed utilizing various softwares. The surveyed field area included an asphalt road that had carbon readings higher than the surrounding land. The clarity with which these carbon-rich zones were delineated on the constructed map represents evidence supporting the veracity of this method. Neutron-gamma analysis technology can greatly facilitate timely construction of soil carbon maps.

Phage-based magnetoelastic (ME) biosensors have been studied as an in-situ, real-time, wireless, direct detection method of foodborne pathogens in recent years. This paper investigates an ME biosensor method for the detection of Salmonella Typhimurium on fresh spinach leaves. A procedure to obtain a concentrated suspension of Salmonella from contaminated spinach leaves is described that is based on methods outlined in the U.S. FDA Bacteriological Analytical Manual for the detection of Salmonella on leafy green vegetables. The effects of an alternative pre-enrichment broth (LB broth vs. lactose broth), incubation time on the detection performance and negative control were investigated. In addition, different blocking agents (BSA, Casein, and Superblock) were evaluated to minimize the effect of nonspecific binding. None of the blocking agents was found to be superior to the others, or even better than none. Unblocked ME biosensors were placed directly in a concentrated suspension and allowed to bind with Salmonella cells for 30 min before measuring the resonant frequency using a surface-scanning coil detector. It was found that 7 h incubation at 37 °C in LB broth was necessary to detect an initial spike of 100 cfu/25 g S. Typhimurium on spinach leaves with a confidence level of difference greater than 95% (p < 0.05). Thus, the ME biosensor method, on both partly and fully detection, was demonstrated to be a robust and competitive method for foodborne pathogens on fresh products.

This paper investigates the effects of surface-scanning detector position on the resonant frequency and signal amplitude of a wireless magnetoelastic (ME) biosensor for direct pathogen detection on solid surfaces. The experiments were conducted on the surface of a polyethylene (PE) plate as a model study. An ME biosensor (1 mm × 0.2 mm × 30 µm) was placed on the PE surface, and a surface-scanning detector was brought close and aligned to the sensor for wireless resonant frequency measurement. The position of the detector was accurately controlled by using a motorized three-axis translation system (i.e., controlled X, Y, and Z positions). The results showed that the resonant frequency variations of the sensor were -125 to +150 Hz for X and Y detector displacements of ± 600 µm and Z displacements of +100 to +500 µm. These resonant frequency variations were small compared to the sensor's initial resonant frequency (< 0.007% of 2.2 MHz initial resonant frequency) measured at the detector home position, indicating high accuracy of the measurement. In addition, the signal amplitude was, as anticipated, found to decrease exponentially with increasing detection distance (i.e., Z distance). Finally, additional experiments were conducted on the surface of cucumbers. Similar results were obtained.

This paper investigates the effects of surface-scanning detector position on the resonant frequency and signal amplitude of a wireless magnetoelastic (ME) biosensor for direct pathogen detection on solid surfaces. The experiments were conducted on the surface of a flat polyethylene (PE) plate as a model study. An ME biosensor (1 mm × 0.2 mm × 30 μm) was placed on the PE surface, and a surface-scanning detector was brought close and aligned to the sensor for wireless resonant frequency measurement. The position of the detector was accurately controlled by using a motorized three-axis translation system (i.e., controlled X, Y, and Z positions). The results showed that the resonant frequency variations of the sensor were -125 to +150 Hz for X and Y detector displacements of ±600 μm and Z displacements of +100 to +500 μm. These resonant frequency variations were small compared to the sensor's initial resonant frequency (< 0.007% of 2.2 MHz initial resonant frequency) measured at the detector home position, indicating high accuracy of the measurement. In addition, the signal amplitude was, as anticipated, found to decrease exponentially with increasing detection distance (i.e., Z distance). Finally, additional experiments were conducted on the surface of cucumbers. Similar results were obtained.

This paper demonstrates a highly sensitive surface-scanning detector used for magnetoelastic (ME) biosensors for the detection of Salmonella on the surface of a polyethylene (PE) food preparation surface. The design and fabrication methods of the new planar spiral coil are introduced. Different concentrations of Salmonella were measured on the surface of a PE board. The efficacy of Salmonella capture and detection is discussed.

Phage based magnetoelastic (ME) biosensors have been shown to be able to rapidly detect Salmonella in various food systems to serve food pathogen monitoring purposes. In this ME biosensor platform, the free-standing strip-shaped magnetoelastic sensor is the transducer and the phage probe that recognizes Salmonella in food serves as the bio-recognition element. According to Sorokulova et al. at 2005, a developed oligonucleotide probe E2 was reported to have high specificity to Salmonella enterica Typhimurium. In the report, the specificity tests were focused in most of Enterobacterace groups outside of Salmonella family. Here, to understand the specificity of phage E2 to different Salmonella enterica serotypes within Salmonella Family, we further tested the specificity of the phage probe to thirty-two Salmonella serotypes that were present in the major foodborne outbreaks during the past ten years (according to Centers for Disease Control and Prevention). The tests were conducted through an Enzyme linked Immunosorbent Assay (ELISA) format. This assay can mimic probe immobilized conditions on the magnetoelastic biosensor platform and also enable to study the binding specificity of oligonucleotide probes toward different Salmonella while avoiding phage/sensor lot variations. Test results confirmed that this oligonucleotide probe E2 was high specific to Salmonella Typhimurium cells but showed cross reactivity to Salmonella Tennessee and four other serotypes among the thirty-two tested Salmonella serotypes.

Magnetoelastic (ME) biosensors with phage-displayed oligopeptide probes have been demonstrated to be highly successful in rapid detection of various pathogens, including Salmonella enterica, on the fruit and vegetable surfaces. However, in lieu of testing each produce individually, it is advantageous to detect pathogens in the produce wash water for high-throughput analysis. The sanitizing guidelines of the United States Food and Drug Administration (FDA) suggest adding Clorox and chlorine dioxide to the produce wash water in processing plants to disinfect harmful food-borne pathogens on fruit and vegetable surfaces. Therefore, to determine the efficacy of our ME biosensors in testing for food-borne pathogens in produce wash water, we assessed the stability of our biosensors in the presence of Clorox and chlorine dioxide. Specifically, Enzyme Linked Immunosorbent Assay (ELISA) was used to study the potential effect of Clorox and chlorine dioxide on the S. Typhimurium capturing ability of our phage probe. At concentrations recommended by the FDA for Clorox (100 ppm free chlorine content) and by the United States Environmental Protection Agency for chlorine dioxide (4 ppm), we observed no negative effect of these chemicals on the stability and S. Typhimurium capturing ability of our phage-displayed oligopeptide probe. These data demonstrate the potential efficacy of using our ME biosensors with phage-displayed oligopeptide probes in produce wash waters to determine the presence of food-borne pathogens.

This paper investigates a phage-based biomolecular filter that enables the evaluation of large volumes of liquids for the presence of small quantities of bacterial pathogens. The filter is a planar arrangement of phage-coated, strip-shaped magnetoelastic (ME) biosensors (4 mm x 0.8 mm x 0.03 mm), magnetically coupled to a filter frame structure, through which a liquid of interest flows. This "phage filter" is designed to capture specific bacterial pathogens and allow non-specific debris to pass, eliminating the common clogging issue in conventional bead filters. ANSYS Maxwell was used to simulate the magnetic field pattern required to hold ME biosensors densely and to optimize the frame design. Based on the simulation results, a phage filter structure was constructed, and a proof-in-concept experiment was conducted where a Salmonella solution of known concentration were passed through the filter, and the number of captured Salmonella was quantified by plate counting.

To avoid food contaminated by pathogens such as Salmonella, magnetoelastic biosensors were used for rapid, wireless, and on-field detection. This paper demonstrates a series of measurements from low to high concentration of Salmonella typhimurium on a polyethylene (PE) chopping board by using a highly sensitive surface-scanning system. In this research, two-dimensional planar spiral coils were fabricated and utilized as the surface scanning detectors in the measurement system for the rapid and sensitive detection of Salmonella. ME biosensors, which was made by metallic glass (Metglas alloy 2826MB) with great magnetoelastic properties were applied on the sample surface for the real-time and in-situ measurement process. The resonant frequency changes of different measurement sensors (coated with E2 phage) change with the various of the Salmonella concentration. At the same time, the stability of control sensors (coated with blocking only) confirmed the specific binding of Salmonella typhimurium by the E2 phage.

This paper presents a rapid method for detecting small quantities of specific bacteria. The method combines phage-coated magnetoelastic (ME) biosensors, microfabricated arrayed bathtubs for cell culture, a surface-scanning detector, and a motorized translation system, enabling real-time monitoring of the growth of specific bacteria in a nutrient broth. Rapid detection of a few bacterial cells is possible, depending on the sensor size and efficiency of bacterial growth.

This paper presents a method for rapid detection of small quantities of specific bacteria. The method combines wireless phage-coated magnetoelastic (ME) biosensors, a surface-scanning detector, and a motorized translation system, enabling real-time monitoring of the growth of specific bacteria in a nutrient broth. The ME biosensor used in this investigation is composed of a freestanding, strip-shaped ME resonator upon which an engineered bacteriophage is coated to capture a pathogen of interest. E2 phage with high binding affinity for Salmonella Typhimurium was used as a model study. The specificity of E2 phage has been reported to be 1 in 10 5 background bacteria. The phage-coated ME biosensors were first exposed to a low-concentration Salmonella suspension to capture roughly 300 cells on the sensor surface. When the growth of Salmonella in the broth occurs, the mass of the biosensor increases, which results in a decrease in the biosensor's resonant frequency. Monitoring of this mass-induced resonant frequency change allows for real-time detection of the presence of Salmonella. Detection of a few bacteria is also possible by growing them to a sufficient number. The surface-scanning detector was used to measure resonant frequency changes of 25 biosensors sequentially in an automated manner as a function of time. This methodology offers direct, real-time detection and quantification of specific bacteria. The rate of the sensor's resonant frequency change was found to be largely dependent on the number of initially bound cells and the efficiency of cell growth.

Rapid and reliable detections for foodborne pathogens are essential to monitor food and improve food safety procedures. Food monitoring, such as monitoring contaminated foods in poultry processing plants and/or field farms with high heat environments, requires thermostable bio-probes on the sensor surfaces for accurate detections. Phage based magnetoelastic (ME) biosensors have been recently developed as a real-time and wireless platform for Salmonella enterica serotype Typhimurum detection in various food systems. The thermostability of phage and aptamer probes were studied here and their binding to Salmonella Typhimurium cells were evaluated using enzyme-linked immunosorbent assay (ELISA) format at various temperatures. The ELISA format can be used to mimic the probe immobilization conditions on ME sensor surfaces and can test bio-probes' performance without the variability that arises from different ME sensor lots. The results of this study can be further applied in the development of the ME biosensor platform.

This paper presents a revolutionary method of bacterial detection that directly detects and quantifies the presence of specific bacteria on the surfaces of fresh produce without sample preparation (water rinse, soak, stomaching) and/or enrichment. The speed of detection is from 2 to 10 minutes with a limit of detection in a range of 10^2 to 10^4 cfu/mm^2. The specificity of detection is 2 in 10^6 background bacteria. This technology was awarded a $20,000 prize in the first United States Food and Drug Administration (FDA) Food Safety Challenge. The method combines wireless magnetoelastic (ME) biosensors and a surface-scanning detector for rapid determination of bacterial contamination. Tests were conducted on tomatoes and grapes spiked with different concentrations of Salmonella Typhimurium. The resonant frequency changes of the biosensors were found to be dependent on the surface concentration of Salmonella. Detection limits were found to be affected by the surface roughness of the food. A 90-second video of a test for Salmonella on tomato can be viewed at http://eng.auburn.edu/food-safety. The method presented in this paper is envisioned for use at ports of entry for the swift screening of foods.

This paper presents a method for detection of a few pathogenic bacteria and determination of live versus dead cells. The method combines wireless phage-coated magnetoelastic (ME) biosensors and a surface-scanning dectector, enabling real-time monitoring of the growth of specific bacteria in a nutrient broth. The ME biosensor used in this investigation is composed of a strip-shaped ME resonator upon which an engineered bacteriophage is coated to capture a pathogen of interest. E2 phage with high binding affinity for Salmonella Typhimurium was used as a model study. The specificity of E2 phage has been reported to be 1 in 105 background bacteria. The phage-coated ME biosensors were first exposed to a low-concentration Salmonella suspension to capture roughly 300 cells on the sensor surface. When the growth of Salmonella in the broth occurs, the mass of the biosensor increases, which results in a decrease in the biosensor's resonant frequency. Monitoring of this mass- induced resonant frequency change allows for real-time detection of the presence of Salmonella. Detection of a few bacteria is also possible by growing them to a sufficient number. The surface-scanning detector was used to measure resonant frequency changes of 25 biosensors sequentially in an automated manner as a function of time. This methodology offers direct, real-time detection, quantification, and viability determination of specific bacteria. The rate of the sensor's resonant frequency change was found to be largely dependent on the number of initially bound cells and the efficiency of cell growth.

A method of ballistic impact welding pure copper to low carbon steel was developed based on the prediction of the critical parameters. The macro profile, microstructure, element distribution across the interface, and the mechanical properties of the welds were studied. It showed that a wavy bond profile was formed at the interface and no intermetallic layer was formed near the interface. The microstructures and the properties exhibited different characteristics in different areas with different distance to the interface for both the copper side and low carbon steel side. Moreover, the additional increase in temperature due to the viscous friction caused by the spinning of projectile between the spinning copper projectile and the low carbon steel results in a recrystallization annealing on the copper side.

The wireless phage-based magnetoelastic (ME) biosensor has proven to be promising for real-time detection of pathogenic bacteria on fresh produces. The ME biosensor consists of a freestanding ME resonator as the signal transducer and filamentous phage as the biomolecular-recognition element, which can specifically bind to a pathogen of interest. Due to the Joule magnetostriction effect, the biosensors can be placed into mechanical resonance when subjected to a time-varying magnetic field alternating at the sensor’s resonant frequency. Upon the attachment of the target pathogen, the mass of the biosensor increases, thereby decreasing its resonant frequency. This paper presents an investigation of blocking reagents immobilization for detecting Salmonella Typhimurium on fresh food surfaces. Three different blocking reagents (BSA, SuperBlock blocking buffer, and blocker BLOTTO) were used and compared. The optical microscope was used for bacterial cells binding observation. Student t-test was used to statistically analysis the experiment results. The results shows that SuperBlock blocking buffer and blocker BLOTTO have much better blocking performance than usually used BSA.

This chapter introduces freestanding, phage-based magnetoelastic (ME) biosensors and their applications as a label-free wireless method for real-time pathogen detection. The ME biosensor is composed of an ME resonator that is coated with a biomolecular recognition element that binds specifically with a target pathogen. Interrogated through magnetic signals, ME biosensors can provide real-time, remote, and specific detection of foodborne pathogens in water, buffer, liquid food, and food surfaces. This chapter introduces the detection principle, the interrogation system, the fabrication of ME biosensors, and their current and future applications in high throughput screening of pathogens in food.

This paper presents an investigation into magnetoelastic (ME) biosentinels that seek out, capture, and detect target pathogens in stagnant liquids. The ME biosentinels are designed to mimic various types of white blood cells, the main defensive mechanism in the human body against different pathogenic invaders. This nature-inspired ME biosentinel is composed of a freestanding ME resonator coated with a landscape phage that is engineered to bind specifically with the pathogen of interest. When subjected to an externally applied alternating magnetic field, the biosentinel can be placed into mechanical resonance (i.e., bending or longitudinal mode of vibration) by magnetostriction. The resonating biosentinel can then move autonomously through a liquid due to the net acting force and fluid-structure interactions. As soon as the biosentinel finds and binds with the target pathogen, changes in the mass as well as resonant frequency of the biosentinel occur, and thereby the presence of the target pathogen can be detected. Due to the wireless nature of detection, the resonance frequency changes can be measured in real time without any physical connection to a detector (by using a designed electromagnetic coil and a network analyzer operating in the reflection mode). In order to actuate the biosentinel into mechanical resonance of a desired mode, modal analysis using the three-dimensional finite element method was first performed, followed by determination of the resonant frequency. In addition, the net acting force and resultant motion of the biosentinel due to the induced mechanical vibration were calculated. As a model study, this paper presents detection of Bacillus anthracis spores, a Category A bioterrorism agent, under stagnant flow conditions. Both dynamic simulation and experimental results showed that the ME biosentinels can move autonomously through the liquid and actively bind with the target pathogen. This investigation will advance the fundamental scientific theories describing the operation of biosentinels and have broad societal impact by improving human health through earlier detection of pathogens. Potential short-term applications include the capture and detection of pathogenic bacteria in liquid food products such as juices and milk.