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Next-generation industrial fiber lasers enable challenging applications that cannot be addressed with legacy fiber lasers. Key features of next-generation fiber lasers include robust back-reflection protection, high power stability, wide power tunability, high-speed modulation and waveform generation, and facile field serviceability. These capabilities are enabled by high-performance components, particularly pump diodes and optical fibers, and by advanced fiber laser designs. We summarize the performance and reliability of nLIGHT diodes, fibers, and next-generation industrial fiber lasers at power levels of 500 W – 8 kW. We show back-reflection studies with up to 1 kW of back-reflected power, power-stability measurements in cw and modulated operation exhibiting sub-1% stability over a 5 – 100% power range, and high-speed modulation (100 kHz) and waveform generation with a bandwidth 20x higher than standard fiber lasers. We show results from representative applications, including cutting and welding of highly reflective metals (Cu and Al) for production of Li-ion battery modules and processing of carbon fiber reinforced polymers.

Previous research conducted in our laboratory found a significant prevalence of multi-drug resistant (MDR) Salmonella and MDR Escherichia coli (MDR EC) in dairy calves and suggests that the MDR EC population may be an important reservoir for resistance elements that could potentially transfer to Salmonella. Therefore, the objective of the current research was to determine if resistance transfers from MDR EC to susceptible strains of inoculated Salmonella. The experiment utilized Holstein calves (approximately 3 weeks old) naturally colonized with MDR EC and fecal culture negative for Salmonella. Fecal samples were collected for culture of Salmonella and MDR EC throughout the experiment following experimental inoculation with the susceptible Salmonella strains. Results initially suggested that resistance did transfer from the MDR E. coli to the inoculated strains of Salmonella, with these stains demonstrating resistance to multiple antibiotics following in vivo exposure to MDR EC. However, serogrouping and serotyping results from a portion of the Salmonella isolates recovered from the calves post-challenge, identified two new strains of Salmonella; therefore transfer of resistance was not demonstrated under these experimental conditions.

Acyl-homoserine-lactone autoinducer (AHL) produced by nonenterohemorrhagic Escherichia coli species in cattle appears to be required for enterohemorrhagic E. coli (EHEC) colonization of the gastrointestinal tract (GIT). The current research aimed to examine the effect of season, diet, EHEC shedding, and location within the GIT on AHL prevalence in the ruminant. Luminal content samples were collected from the rumen and rectum of feedlot cattle at slaughter in the spring, summer, fall, and winter for culture of E. coli O157:H7 and AHL determination. During the spring collection, samples were additionally collected from the cecum and small intestine, but these samples all were AHL negative and therefore not examined again. To assess the influence of diet on AHL prevalence, 14 lambs were fed either 100% forage or 80% concentrate diets and experimentally inoculated with EHEC. At 8 days after infection, all the lambs were killed, and necropsies were taken, with luminal contents collected from the GIT. The collections from the feedlot cattle had AHL in 100% of the rumen content samples from the spring, summer, and fall, but not in any of the winter samples. No other GIT samples from feedlot cattle were AHL positive, and all the samples from the sheep study were AHL negative. The cattle seemed to show a weak correlation between ruminal AHL and EHEC prevalence. This research found AHL only in the rumen and not in the lower GIT of feedlot cattle. However, it is unclear whether this is because the pH of the lower gut destroys the AHL or because a lack of certain bacteria in the lower gut producing AHL.

With the adoption of visual instrument grading, the calculated yield grade can be used for payment to cattle producers selling on grid pricing systems. The USDA beef carcass grading standards include a relationship between required LM area (LMA) and HCW that is an important component of the final yield grade. As noted on a USDA yield grade LMA grid, a 272-kg (600-lb) carcass requires a 71-cm 2 (11.0-in. 2 ) LMA and a 454-kg (1,000-lb) carcass requires a 102-cm 2 (15.8-in. 2 ) LMA. This is a linear relationship, where required LMA = 0.171(HCW) + 24.526. If a beef carcass has a larger LMA than required, the calculated yield grade is lowered, whereas a smaller LMA than required increases the calculated yield grade. The objective of this investigation was to evaluate the LMA to HCW relationship against data on 434,381 beef carcasses in the West Texas A&M University (WTAMU) Beef Carcass Research Center database. In contrast to the USDA relationship, our data indicate a quadratic relationship [WTAMU LMA = 33.585 + 0.17729(HCW) -0.0000863(HCW 2 )] between LMA and HCW whereby, on average, a 272-kg carcass has a 75-cm 2 (11.6-in. 2 ) LMA and a 454-kg carcass has a 96-cm 2 (14.9-in. 2 ) LMA, indicating a different slope and different intercept than those in the USDA grading standards. These data indicate that the USDA calculated yield grade equation favors carcasses lighter than 363 kg (800 1b) for having above average muscling and penalizes carcasses heavier than 363 kg (800 1b) for having below average muscling. If carcass weights continue to increase, we are likely to observe greater proportions of yield grade 4 and 5 carcasses because of the measurement bias that currently exists in the USDA yield grade equation.

Bioelectrical impedance technology (BIA) is capable of providing an objective method of beef carcass yield estimation with the rapidity of yield grading. Electrical resistance (Rs), reactance (Xc), impedance (I), hot carcass weight (HCW), fat thickness between the 12th and 13th ribs (FT), estimated percentage kidney, pelvic, and heart fat (KPH%), longissimus muscle area (LMA), length between electrodes (LGE) as well as three derived carcass values that included electrical volume (EVOL), reactive density (XcD), and resistive density (RsD) were determined for the carcasses of 41 commercially fed cattle. Carcasses were subsequently fabricated into salable beef products reflective of industry standards. Equations were developed to predict percentage salable carcass yield (SY%) and percentage trimmable fat (FT%). Resulting equations accounted for 81% and 84% of variation in SY% and FT%, respectively. These results indicate that BIA technology is an accurate predictor of beef carcass composition.

This document is a concise compendium of resource material covering assured thermal processing of wastes (ATPW), an area in which Sandia aims to develop a large program. The ATPW program at Sandia is examining a wide variety of waste streams and thermal processes. Waste streams under consideration include municipal, chemical, medical, and mixed wastes. Thermal processes under consideration range from various incineration technologies to non-incineration processes such as supercritical water oxidation or molten metal technologies. Each of the chapters describes the element covered, discusses issues associated with its further development and/or utilization, presents Sandia capabilities that address these issues, and indicates important connections to other ATPW elements. The division of the field into elements was driven by the team`s desire to emphasize areas where Sandia`s capabilities can lead to major advances and is therefore somewhat unconventional. The report will be valuable to Sandians involved in further ATPW program development.

We report theoretical and experimental studies of the effects of collisional quenching and the contributions of thermal gratings in degenerate four-wave mixing (DFWM).1 Using single-mode laser radiation, peak signal intensity measurements were performed on an isolated line in the A-X transition of NO. By using appropriate mixtures of N2 and CO2 as buffer gases, we varied the collisional quenching rate over several orders of magnitude while maintaining a fixed total collisional dephasing rate. The varying quenching rate also had the effect of varying the heat released by population gratings to form thermal gratings, permitting detailed comparisons of signal intensities from both mechanisms.

High resolution Raman studies of the Q branch in H2 perturbed by Ar are relevant to combustion diagnostics and for tests of the intermolecular potential. The use of spectroscopic techniques to study combustion requires accurate models for the line shapes, which can range front Lorentzian to Gaussian to more complicated profiles1 depending on the perturber species, perturber concentration, density and temperature. Calculations with these models require estimates of the speed dependence of the line-shift and line-broadening coefficients. Modern theories are now able to predict the shifting and broadening resulting from collisions but are hampered by uncertainties in the interaction potential. One of the most studied potentials is that of H2-Ar, which has the advantage of being theoretically tractable for line shape computations. Furthermore, since the masses of Ar and molecular O2 and N2 are similar, spectral features depending on the perturber’s mass are expected to be similar. We report preliminary measurements of the density shift of the Q branch lines in H2 as a function of rotational state and temperature.

The γ-system (A2Σ+ X2Π) of nitric oxide (NO) is observed in many environments including combustion and atmospheric applications. Molecular properties of the A2Σ+ state are thus important in collision theories used to predict A-X radiative efficiencies. These theories often involve electric-multipole expansions,1,2 in which the permanent electric dipole moment of A2Σ+ (µA) is the leading term for long-range interactions. Moreover, µA is a basic property of the molecular charge distribution and has often been used to gauge the accuracy of ab initio quantum chemistry calculations.3-6 Here we describe measurements of Stark quantum beats in the fluorescence of NO from which we derive a precise value for µA in v'=0. This is the vibrational level most often excited in laser-based methods for detecting NO. Bergeman and Zare,7 using a radio frequency-optical double-resonance technique, provide the only other measurement of µA in a different vibrational level (v'=3). We thus also determine the change in µA with v', which provides a sensitive test of computed dipole moment functions.

Rotational energy transfer is an important process affecting the spectroscopy of molecules in the gas phase. The collisional broadening observed in Raman and infrared-absorption transitions is typically dominated by rotational relaxation.1 The saturation characteristics of N2 coherent anti-Stokes Raman spectroscopy (CARS) spectra2 and the collapse of N2 Q-branch spectra at high pressures3 are known to depend sensitively on rotational transfer. To predict N2 Raman spectra under these conditions, many empirical models for the J-dependent transfer rates have been proposed.3

The potential of resonant degenerate four-wave mixing (DFWM) as a sensitive, coherent diagnostic probe of combustion species has recently been demonstrated.1,2 Similar to coherent anti-Stokes Raman spectroscopy (CARS), DFWM generates a highly collimated, narrow bandwidth signal beam that allows remote detection, requires minimal optical access, and provides excellent immunity to background luminosity. However, since DFWM is typically performed with resonant radiation, it offers much greater sensitivity than CARS, permitting trace-species detection. While DFWM has been extensively studied in the context of phase conjugation,3 comparatively little has been reported on the development of DFWM for quantitative molecular spectroscopy.

In degenerate four-wave mixing, three input beams of identical frequency interact with a nonlinear medium to generate a fourth coherent signal beam. The efficiency is resonant with an atomic or molecular transition. The coherent nature of the signal beam offers many advantages for minor species detection. Prior experiments using ultraviolet wavelengths to detect OH or NH radicals in flames and NO as a low pressure gas readily demonstrated good background discrimination and high signal collection efficiency. The current experiments illustrate the potential of infrared DFWM for minor species detection. Extension of degenerate four-wave mixing to the infrared region of the spectrum offers exciting potential for species diagnostics. Many molecules are not easily detected using laser-induced fluorescence or multiphoton ionization because they do not have readily accessible and well characterized electronic absorptions. Almost all molecules have ro-vibrational transitions that are accessible using infrared light. However, detection of molecules using infrared diagnostic methods has often proved difficult.

We have observed line profiles in Raman Q‐branch transitions of H2 perturbed by Ar that are asymmetric about the line center using high resolution inverse Raman spectroscopy. These effects are observed at densities normally considered to be in the impact regime, i.e., well above the Dicke minimum for H2‐Ar(∼1 amagat) and below those densities for which finite collision‐duration or collision‐induced scattering become important. We have successfully modeled the observed line profiles by incorporating inhomogeneous broadening arising from a strong dependence of the collisional line shift on radiator speed. The model is more complex than the speed‐dependent Voigt line profile1,2 since the effects of speed‐changing collisions, which coherently narrow the inhomogeneous part of the line profile, must be included. In H2 the asymmetry is more pronounced for heavy perturbers and essentially disappears in H2/He mixtures and in pure H2.

This paper presents a comparison of directly measured rotational energy transfer rates in N2 (v=1) with predictions of several common models. Reasonable agreement is found with the modified exponential gap law; better agreement is found using the sudden approximation if experimental values of J=0 to J=J’ rates are used. (AIP)

Raman backscattering spectroscopy is used to characterize thin non-metallic films for applications in materials research. In situ studies of the oxidation and hot salt corrosion of iron- and nickel-based alloys demonstrate the capability of obtaining structural and chemical information from surface films on samples at elevated temperatures (up to 850°C). Studies of the oxidation of SAE 310 stainless steel and similar alloys show that phases of iron, chromium and mixed spinel oxides are identifiable in surface films which are too thin for analysis by X-ray diffractometry. This information is obtained both during and after exposure to high temperature environments. Similar data are obtained from alloys undergoing corrosive attack by a surface coating of molten salt. Both salt chemistry and oxide formation are simultaneously monitored using the Raman technique.

We have measured state‐resolved rotational energy transfer rates of H2 (v=1) in collisions with H2 (v=0) at 295 K, using optical pump/probe techniques. A single rotational level was populated using stimulated Raman pumping, and the degree of collision‐induced population transfer was monitored using either coherent anti‐Stokes Raman spectroscopy (CARS) or resonance‐enhanced multiphoton ionization spectroscopy (REMPI). The CARS and REMPI results are in good agreement; averages of the two sets of rates are 180±27×106 s−1 amagat−1 for j=0→2 and 50±8×106 s−1 amagat−1 for j=1→3. We also observed transfer of vibrational excitation from paraspin v=1 states to ortho v=0 states due to v–v exchange, measuring a rate of 1.9±0.8×106 s−1 amagat−1 for this process.

Raman spectroscopy is shown to provide direct information on the composition and structure of surface oxides formed on alloys. Previously, identification of specific compounds present in these oxides only could be inferred from conventional surface analysis methods. In our studies, backscattering spectra were obtained from thick oxide films (⪞10 μm) present on high purity and commercial stainless steels after exposure to air and coal gasifier environments at 980 °C. With as‐grown oxides, data were obtained from the outer oxide regions. Spectra from inner regions also were measured using grazing‐angle sectioning techniques. The presence of impurities and minor alloying constituents in the substrates are shown to have profound effect on results; for example, the addition of a few percent of titanium and manganese resulted in the formation of a duplex scale with a thin, complex, outer layer and a relatively thick α–Cr2O3 inner scale.

Backscattering Raman spectroscopy is demonstrated to be a useful technique for in situ characterization of oxide films on metals at high temperatures. Data obtained during oxidation at temperatures between 300 and 850 °C are presented for two different iron‐based alloys. The sensitivity and specificity of the technique were sufficient to detect the formation of iron oxide films (Fe2O3 and Fe3O4) less than 150 A in thickness at temperatures below 350 °C. Above 600 °C, the predominant oxide was Cr2O3; however, the presence of a few weight percent Mn in a commercial alloy produced a mixed spinel oxide in addition to Cr2O3.

Coherent emission from Ho3+ ions (2.1 μm) in a YIG host at 77 °K has been observed by optical pumping into the electronic absorption bands of the YIG host material, using (i) a pulsed Nd : glass laser to pump into the tail of the 6A1g→4T1g band (which has an absorption coefficient α=0.18 cm−1 at 1.06 μm) or (ii) a pulsed ruby laser (0.6943 μm) to pump the 6A1g→4T2g band near its peak (where α=300 cm−1). The Ho3+ emission from an illuminated slab 30–40 μm was investigated as a function of input pump energy. The electronic absorption bands of YIG are strong, broad, and have good energy‐transfer efficiency to the upper laser level of the Ho3+ ions.