Update on elbow arthroplasties with emphasis on imaging.

Elbow arthroplasty is increasing in popularity and can be used to treat many conditions, such as trauma, primary and secondary osteoarthritis, inflammatory arthritis, and osteonecrosis. Total elbow arthroplasty (TEA) is reserved for patients with severe symptoms refractory to more conservative management. In addition to TEA, hemi-arthroplasty, interposition arthroplasty, and resection arthroplasty also play roles in the management of elbow pain. There are specific indications for each type of arthroplasty. Postoperative complications may occur with elbow arthroplasties and may be surgery or hardware related. Imaging is important in both pre-operative planning as well as in post-surgical follow-up. This article reviews the different types of elbow arthroplasties, their indications, their normal postoperative imaging appearances, and imaging findings of potential complications.

Kinetics of CN (v = 1) reactions with butadiene isomers at low temperature by cw-cavity ring-down in a pulsed Laval flow with theoretical modelling of rates and entrance channel branching.

We present an experimental and theoretical investigation of the reaction of vibrationally excited CN (v = 1) with isomers of butadiene at low temperature. The experiments were conducted using the newly built apparatus, UF-CRDS, which couples near-infrared cw-cavity ring-down spectroscopy with a pulsed Laval flow. The well-matched hydrodynamic time and long ring-down time decays allow measurement of the kinetics of the reactions within a single trace of a ring-down decay, termed Simultaneous Kinetics and Ring-down (SKaR). The pulsed experiments were carried out using a Laval nozzle designed for the 70 K uniform flow with nitrogen as the carrier gas. The measured bimolecular rates for the reactions of CN (v = 1) with 1,3-butadiene and 1,2-butadiene are (3.96 ± 0.28) × 10-10 and (3.06 ± 0.35) × 10-10 cm3 per molecule per s, respectively. The reaction rate measured for CN (v = 1) with the 1,3-butadiene isomer is in good agreement with the rate previously reported for the reaction with ground state CN (v = 0) under similar conditions. We report the rate of the reaction of CN (v = 1) with the 1,2-butadiene isomer here for the first time. The experimental results were interpreted with the aid of variable reaction-coordinate transition-state theory calculations to determine rates and branching of the addition channels based on a high-level multireference treatment of the potential energy surface. H-abstraction reaction rates were also theoretically determined. For the 1,2-butadiene system, theoretical estimates are then combined with literature values for the energy-dependent product yields from the initial adducts to predict overall temperature-dependent product branching. H loss giving 2-cyano-1,3-butadiene + H is the main product channel, exclusive of abstraction, at all energies, but methyl loss forming 1-cyano-prop-3-yne is 15% at low temperature growing to 35% at 500 K. Abstraction forming HCN and various radicals is important at 500 K and above. The astrochemical implications of these results are discussed.

Antibiotic Prescribing Errors in Patients Discharged From the Pediatric Emergency Department.

OBJECTIVES: The pediatric emergency department (PED) is an especially high-risk setting for medication errors. Several factors contribute to this risk including the need to provide care to complex patients who are unknown to staff, the frequent use of verbal orders, and the necessity of weight-based dosing. This investigation sought to assess one potentially error-prone event, antibiotic prescriptions written for patients being discharged from the PED, and to characterize the occurrence of medication errors to identify opportunities for improvement. METHODS: This was a retrospective study of pediatric patients seen at a large academic medical center PED. All prescriptions written for an antibiotic for patients 18 years or younger that were discharged from the PED from 2015 to 2018 were evaluated for errors in directions, indication, dose, quantity, and refills. Because antibiotic dosing can vary based on indications, only disease states with guideline-specific dosing recommendations were evaluated for dosing errors. RESULTS: A total of 11,815 antibiotic prescriptions were analyzed for patients discharged from the PED, and 1986 (16.8%) errors were identified. Of all the prescriptions reviewed, 517 (4.4%) contained an incomplete prescription error. Discharge prescriptions written by off-service physicians were more likely to contain incomplete prescription errors (5.1%) when compared with emergency medicine physicians (3.9%; P = 0.022). A dosing error rate of 18.5% (1469 prescriptions) was identified for the 7930 disease state-specific prescriptions reviewed. Underdosing errors were significantly more common (51.6%) than overdosing errors (29.3%; P < 0.0001). Among the different agents, there was noted to be a significant difference in the antibiotics most commonly involved in dosing errors (P < 0.0001). Additionally, there was also a significant difference in the incidence of dosing errors between different disease states (P < 0.0001). No significant difference was found in the incidence of dosing errors across physician specialties (P = 0.872). CONCLUSIONS: We identified 1986 (16.8%) total errors in this analysis of antibiotic prescriptions written on discharge from the PED. Among the disease states evaluated, dosing errors were identified in 18.5% of prescriptions with the most common error being underdosing. Literature evaluating pediatric prescription errors, and specifically antibiotic discharge prescriptions, is quite limited. Further investigation is necessary in this area, and strategies should be developed leveraging technology, enhancing education, and using pharmacy personnel to help reduce antibiotic prescribing errors for patients discharged from the PED.

Characterization of Emergency Department Rabies Post-Exposure Prophylaxis Procedures with an Infectious Diseases Clinic Referral Process.

Purpose: Rabies post-exposure prophylaxis (rPEP) in the emergency department (ED) is associated with high costs, complicated administration protocols, and a time-sensitive vaccination series that often requires ED follow-up visits for subsequent vaccine administration. This study sought to characterize the number of redirected vaccine administrations in those patients referred to ID Clinic, guideline compliance, and opportunities for improvement. Methods: Retrospective chart review of adult and pediatric patients presenting to the ED from 2016 to 2019 and prescribed rabies immunoglobulin. Results: Of the 89 patients included, 66.3% were referred to ID Clinic. Those referred to clinic had significantly fewer average visits to the ED for repeat vaccination (P < .001). Of the 177 vaccinations prescribed for patients referred, 105 were administered in clinic. Overall, having insurance significantly increased the odds of completing the prescribed vaccination series (Odds Ratio (OR) = 4.34, 95% Confidence Interval (CI) = 1.34 to 15.52). Among those patients referred to clinic, having insurance significantly increased the odds of receiving any follow-up doses in clinic (OR = 6.00, 95% CI = 1.48 to 25.98), receiving all of their prescribed follow-up doses in clinic (OR = 10.00, 95% CI = 1.72 to 190.80), and completing the entirety of their vaccination series (OR = 5.89, 95% CI = 1.50 to 26.21). Conclusions: The use of an ID Clinic referral process for rPEP resulted in a significant reduction in the average number of visits to the ED for repeat vaccination, hence avoiding 105 ED visits. Insurance status was a significant factor in both the utilization of the ID Clinic referral system and overall completion of the vaccination series. Future research should explore workflows inclusive of both ED care and outpatient follow-up, care plans for the uninsured, and mechanisms to limit the number of patients that fail to complete the recommended vaccination series.

Risk Factors for Antibiotic Resistant Urinary Pathogens in Patients Discharged From the Emergency Department.

Purpose: Urinary tract infections (UTIs) are one of the most common indications for antimicrobial use in the emergency department (ED). Appropriate empiric selection is crucial to ensure optimal care while limiting broad-spectrum antibiotic use. The primary objective of this study was to evaluate the relationship between patient-specific risk factors and drug resistant urinary pathogens in patients discharged from the ED and followed by Emergency Medicine Pharmacists (EMPs). Methods: This was a single-center, retrospective chart review of adult (≥18 years old) patients with positive urine cultures discharged from the ED. The association between risk factors and pathogen resistance to ≥1 classes of antibiotics was evaluated using multivariate logistic regression. Risk factors included the following: hospitalization within the previous 30 days, intravenous antibiotic use within 90 days, diabetes, clinical atherosclerotic cardiovascular disease, psychiatric disorder, dementia, current antibiotic use for any indication, previous lifetime history of UTIs, indwelling or intermittent catheterization, hemodialysis, previous lifetime history of a urologic procedure, urinary tract abnormality, immunosuppressive disease or medications, current residence in a nursing or rehabilitation facility, and history of a multidrug resistant organism (MDRO). Results: A total of 1018 patients were included. There was an increase in the odds of antibiotic resistance in patients with cystitis and ≥2 risk factors (Odds Ratio [OR] = 1.70, 95% CI = 1.24-2.32). In those with pyelonephritis, there was a non-significant increase in the odds of resistance for those with ≥2 risk factors (OR = 1.83, 95% CI = 0.98-3.42). Patients with pyelonephritis discharged on inappropriate antibiotics were more likely to return to the ED within 30 days (P = .03). Conclusions: For patients with cystitis discharged from the ED, those with ≥2 patient-specific risk factors had significantly increased odds of antibiotic resistance. Patients with pyelonephritis, but not cystitis, who were discharged on inappropriate antibiotics were more likely to return to the ED within 30 days. In conjunction with an EMP culture follow-up program, the identification of risk factors for antimicrobial resistance can be used to design more patient-specific empiric antibiotic selections.

Assessment of benzodiazepine dosing strategies for the management of status epilepticus in the emergency department.

PURPOSE: Although guidelines recommend specific benzodiazepine doses for the treatment of generalized convulsive status epilepticus (GCSE), underdosing appears to be common. The purpose of this investigation was to assess benzodiazepine dosing strategies for the initial management of GCSE in patients presenting to the Emergency Department (ED). METHODS: This was a retrospective review of adult patients who received benzodiazepines in the ED for treatment of GCSE. Characteristics of those achieving seizure cessation following initial benzodiazepine therapy were assessed. RESULTS: 222 patients presented to the ED and received 403 doses of benzodiazepines, of which 1.5% conformed with recommendations. First-line therapy was successful in 86.8% of patients with an average dose of 1.6 mg (0.02 mg/kg). No difference in dosing was noted between those experiencing early cessation and those that did not (p = 0.132). Patients experiencing early cessation were significantly less likely to receive further doses, be intubated, or be admitted to the intensive care unit (ICU) or hospital (p < 0.05 for all comparisons). Those that received early antiepileptic drug therapy were significantly less likely to receive additional benzodiazepine doses, be intubated, or be admitted to the ICU or hospital (p < 0.05 for all comparisons). CONCLUSIONS: According to guideline recommendations, there was consistent underdosing of benzodiazepines noted in both prehospital and ED settings. Early seizure cessation and the early receipt of an antiepileptic drug were found to be associated with multiple significant clinical outcomes. Future investigations should explore optimal dosing strategies for benzodiazepines as well as the impact of early antiepileptic drug administration.

Incidence of prescription errors in patients discharged from the emergency department.

PURPOSE: The Emergency Department (ED) is known for its high rates of medication errors secondary to many characteristics such as unfamiliar patients, lack of continuity of care, increasing patient volumes, reliance on verbal orders, and fewer safety mechanisms. The purpose of this study was to quantify and characterize the medication errors that occur in patients discharged from the ED. METHODS: Prescriptions for patients discharged from the adult ED at an academic medical center from 2015 to 2018 were reviewed. Errors in discharge medication orders were documented as well as characteristics of these errors including medication class, errors in prescription directions, quantity prescribed, and refills given inappropriately. RESULTS: A total of 115,933 prescriptions were reviewed and a total of 20,498 errors were identified within 19,126 prescriptions. Of the errors identified, 4048 (19.7%) involved prescription directions, 6537 (31.9%) were errors in quantity prescribed, and 9913 (48.4%) were prescriptions written with refills. The proportion of errors among different prescriber statuses was significantly different when comparing all prescribers (p < .001). Prescriptions written by Non-Emergency Medicine residents had significantly more errors in quantity and refills (p < .001, p < .001), and prescriptions written by Emergency Medicine residents had significantly more errors in directions (p < .001). CONCLUSIONS: This review identified a 16.5% error rate among all prescriptions provided to patients upon ED discharge that varied among different subcategories of medications. This is consistent with the limited literature that is currently available on the topic. These results could assist institutions in developing targeted mitigation strategies to limit medication misadventures in patients discharged from the ED.

Chest ultrasonography by frontline physicians is more sensitive than CXR for diagnosing pneumothorax in trauma patients.

SOURCE CITATION: Chan KK, Joo DA, McRae AD, et al. Chest ultrasonography versus supine chest radiography for diagnosis of pneumothorax in trauma patients in the emergency department. Cochrane Database Syst Rev. 2020;7:CD013031. 32702777.

Point-of-care ultrasonography had 92% sensitivity and 97% specificity for diagnosing diverticulitis in the ED.

SOURCE CITATION: Cohen A, Li T, Stankard B, Nelson M. A prospective evaluation of point-of-care ultrasonographic diagnosis of diverticulitis in the emergency department. Ann Emerg Med. 2020. [Epub ahead of print]. 32653332.

Weight-based versus non-weight-based diltiazem dosing in the setting of atrial fibrillation with rapid ventricular response.

PURPOSE: There is conflicting evidence to support the superiority of weight-based (WB) dosing of intravenous (IV) diltiazem over non-weight-based (NWB) dosing strategies in the management of atrial fibrillation (AFib) with rapid ventricular response (RVR). METHODS: A retrospective review evaluated patients presenting to the emergency department (ED) in AFib with RVR and receiving IV diltiazem from 2015 to 2018. Those receiving a NWB dose were compared with those receiving a WB dose based on actual body weight (ABW). Secondary analyses evaluated safety profiles of the regimens and compared response in groups defined by ABW or ideal body weight (IBW). RESULTS: A total of 371 patients were included in the analysis. No significant difference was observed in achieving a therapeutic response (66.5% vs. 73.1%, p = 0.18) or adverse events between the groups. Patients receiving a WB dose were significantly more likely to have a HR < 100 bpm than those receiving a NWB dose (40.9% vs. 53.5%, p = 0.01). When groups were defined by IBW, WB dosing was associated with a significantly higher incidence of achieving a therapeutic response (62.7% vs. 74.3%, p = 0.02). CONCLUSION: In patients presenting with AF with RVR, there was no significant difference in achieving a therapeutic response between the two strategies. A WB dosing approach did result in a greater proportion of patients with a HR < 100 bpm. The utilization of IBW for WB dosing may result in an increased achievement of a therapeutic response.

Evidence for lambda doublet propensity in the UV photodissociation of ozone.

The photodissociation of O3 at 266 nm has been studied using velocity mapped ion imaging. We report temperature-dependent vector correlations for the O2(a1Δg, v = 0, j = 18-20) fragments at molecular beam temperatures of 70 K, 115 K, and 170 K. Both the fragment spatial anisotropy and the v-j correlations are found to be increasingly depolarized with increasing beam temperature. At all temperatures, the v-j correlations for the j = 19 state were shown to be reduced compared to those of j = 18 and 20, while no such odd/even rotational state difference was observed for the spatial anisotropy, consistent with previous measurements. We find that temperature-dependent differences in the populations and v-j correlations between the odd and even rotational states can be explained by a Λ-doublet propensity model. Although symmetry conservation should lead to formation of only the A' Λ-doublet component, and only even rotational states, out-of-plane rotation of the parent molecule breaks the planar symmetry and permits the formation of the A″ Λ-doublet component and odd rotational states. A simple classical model to treat the effect of parent rotation on the v-j correlation and the odd/even rotational population alternation reproduces both the current measurements and previously reported rotational distributions, suggesting that the "odd" behavior originates from a Λ-doublet propensity, and not from a mass independent curve crossing effect, as previously proposed.

Delayed Intracranial Hemorrhage in Anticoagulated Geriatric Patients After Ground Level Falls.

BACKGROUND: The reported risk of delayed intracranial hemorrhage (ICH) in a trauma patient on warfarin is estimated to be between 0.6% and 6%. The risk of delayed ICH in trauma patients taking novel oral anticoagulants (NOACs) is not well-defined. OBJECTIVE: We hypothesized that there was a significant number of delayed presentations of ICH in patients on NOACs. METHODS: A retrospective review of our trauma registry was performed on geriatric patients (age older than 64 years) who were initially evaluated at our level I trauma center, had fall from standing height or less, and were anticoagulated (warfarin or NOACs), from April 2017 to March 2018. RESULTS: Seventy-seven patients met inclusion criteria. The mean age was 80 ± 7.7 years and 46% of patients were male. The admission head computed tomography scan was positive in 20.8% of patients. Positive scans were more common in patients on warfarin vs. NOACs (30% vs. 14%; p = 0.074) and had a significantly higher Injury Severity Score (median [interquartile range]: 9 [3-15] vs. 5 [1-9]; p = 0.030) and Abbreviated Injury Scale-Head score (median [interquartile range]: 1 [0-3] vs. 1 [0-2]; p = 0.035). The agreement between loss of consciousness (LOC) and ICH was 72% (κ = -0.064; p = 0.263). Fifty-one percent of patients had a repeat head CT. New ICH was diagnosed in 9.6% of patients. All of these patients were on NOACs. CONCLUSIONS: A fall from standing or less in anticoagulated geriatric patients is a significant mechanism of injury resulting in ICH. The absence of LOC does not eliminate the possibility of ICH. There is a significant risk of delayed ICH for patients on NOACs and repeat evaluations should be performed. A prospective multicenter evaluation of this finding is warranted.

Dextran Sulfate Sodium Colitis Facilitates Colonization with Shiga Toxin-Producing Escherichia coli: a Novel Murine Model for the Study of Shiga Toxicosis.

Shiga toxin-producing Escherichia coli (STEC) bacteria are globally important gastrointestinal pathogens causing hemorrhagic gastroenteritis with variable progression to potentially fatal Shiga toxicosis. Little is known about the potential effects of E. coli-derived Shiga-like toxins (STXs) on host gastrointestinal immune responses during infection, in part due to the lack of a reproducible immunocompetent-animal model of STEC infection without depleting the commensal microbiota. Here, we describe a novel and reproducible murine model utilizing dextran sulfate sodium (DSS) colitis to induce susceptibility to colonization with clinical-isolate STEC strains. After exposure to DSS and subsequent oral STEC challenge, all the mice were colonized, and 66% of STEC-infected mice required early euthanasia. Morbidity during STEC infection, but not infection with an isogenic STEC mutant with toxin deleted, was associated with increased renal transcripts of the injury markers KIM1 and NGAL, histological evidence of renal tubular injury, and increased renal interleukin 6 gene (IL-6) and CXCL1 inflammatory transcripts. Interestingly, the intestinal burden of STEC during infection was increased compared to its isogenic Shiga toxin deletion strain. Increased bacterial burdens during Shiga toxin production coincided with decreased induction of colonic IL-23 axis transcripts known to be critical for clearance of similar gastrointestinal pathogens in mice, suggesting a previously undescribed role for STEC Shiga toxins in suppressing host immune responses during STEC infection and survival. The DSS+STEC model establishes infection with clinical-isolate strains of STEC in immunocompetent mice without depleting the gastrointestinal microbiota, enabling characterization of the effects of STXs on the IL-23 axis and other gastrointestinal pathogen-host interactions.

Frequency measurements and self-broadening of sub-Doppler transitions in the v 1 + v 3 band of C2H2.

Frequency comb-referenced measurements of sub-Doppler laser saturation dip absorption lines in the v 1 + v 3 band of acetylene near 1.5 µm are reported. These measurements include transitions involving higher rotational levels than previously frequency measured in this band. The accuracy of the measured frequencies is typically better than 10 kHz. Measurements of the observed sub-Doppler line widths as a function of pressure showed that the self-pressure-broadening coefficients are about 3.5 times larger than those derived from conventional pressure broadening of unsaturated Doppler-limited spectra. This is attributed to the contribution of velocity-changing collisions to the total dephasing rate in the low pressure sub-Doppler measurements. At higher pressures, when the homogeneous broadening becomes comparable to the typical Doppler shift per elastic collision, the velocity changing collisions cease to contribute significantly to the incremental pressure broadening. A time-dependent soft collision model is developed to illustrate the transition between low and high pressure regimes of sub-Doppler pressure-broadening.

Supercontinuum Fourier transform spectrometry with balanced detection on a single photodiode.

We demonstrate a method of combining a supercontinuum light source with a commercial Fourier transform spectrometer, using a novel approach to dual-beam balanced detection, implemented with phase-sensitive detection on a single light detector. A 40 dB reduction in the relative intensity noise is achieved for broadband light, analogous to conventional balanced detection methods using two matched photodetectors. Unlike conventional balanced detection, however, this method exploits the time structure of the broadband source to interleave signal and reference pulse trains in the time domain, recording the broadband differential signal at the fundamental pulse repetition frequency of the supercontinuum. The method is capable of real-time correction for instability in the supercontinuum spectral structure over a broad range of wavelengths and is compatible with commercially designed spectrometers. A proof-of-principle experimental setup is demonstrated for weak absorption in the 1500-1600 nm region.

Quadrupole splittings in the near-infrared spectrum of 14NH3.

Sub-Doppler, saturation dip, spectra of lines in the v1 + v3, v1 + 2v4, and v3 + 2v4 bands of 14NH3 have been measured by frequency comb-referenced diode laser absorption spectroscopy. The observed spectral line widths are dominated by transit time broadening and show resolved or partially-resolved hyperfine splittings that are primarily determined by the 14N quadrupole coupling. Modeling of the observed line shapes based on the known hyperfine level structure of the ground state of the molecule shows that, in nearly all cases, the excited state level has hyperfine splittings similar to the same rotational level in the ground state. The data provide accurate frequencies for the line positions and easily separate lines overlapped in Doppler-limited spectra. The observed hyperfine splittings can be used to make and confirm rotational assignments and ground state combination differences obtained from the measured frequencies are comparable in accuracy to those obtained from conventional microwave spectroscopy. Several of the measured transitions do not show the quadrupole hyperfine splittings expected based on their existing rotational assignments. Either the assignments are incorrect or the upper levels involved are perturbed in a way that affects the nuclear hyperfine structure.

The near-infrared spectrum of ethynyl radical.

Transient diode laser absorption spectroscopy has been used to measure three strong vibronic bands in the near infrared spectrum of the C2H, ethynyl, radical not previously observed in the gas phase. The radical was produced by ultraviolet excimer laser photolysis of either acetylene or (1,1,1)-trifluoropropyne in a slowly flowing sample of the precursor diluted in inert gas, and the spectral resolution was Doppler-limited. The character of the upper states was determined from the rotational and fine structure in the observed spectra and assigned by measurement of ground state rotational combination differences. The upper states include a (2)Σ(+) state at 6696 cm(-1), a second (2)Σ(+) state at 7088 cm(-1), and a (2)Π state at 7110 cm(-1). By comparison with published calculations [R. Tarroni and S. Carter, J. Chem. Phys 119, 12878 (2003); Mol. Phys. 102, 2167 (2004)], the vibronic character of these levels was also assigned. The observed states contain both X(2)Σ(+) and A(2)Π electronic characters. Several local rotational level perturbations were observed in the excited states. Kinetic measurements of the time-evolution of the ground state populations following collisional relaxation and reactive loss of the radicals formed in a hot, non-thermal, population distribution were made using some of the strong rotational lines observed. The case of C2H may be a good place to investigate the behavior at intermediate pressures of inert colliders, where the competition between relaxation and reaction can be tuned and observed to compare with master equation models, rather than deliberately suppressed to measure thermal rate constants.

Rotational and angular distributions of NO products from NO-Rg (Rg = He, Ne, Ar) complex photodissociation.

We present the results of an investigation into the rotational and angular distributions of the NO à state fragment following photodissociation of the NO-He, NO-Ne, and NO-Ar van der Waals complexes excited via the à ← X̃ transition. For each complex, the dissociation is probed for several values of Ea, the available energy above the dissociation threshold. For NO-He, the Ea values probed were 59, 172, and 273 cm(-1); for NO-Ne they were 50 and 166 cm(-1); and for NO-Ar they were 44, 94, 194, and 423 cm(-1). The NO à state rotational distributions arising from NO-He are cold, with most products in low angular momentum states. NO-Ne leads to broader NO rotational distributions but they do not extend to the maximum possible given the energy available. In the case of NO-Ar, the distributions extend to the maximum allowed at that energy and show the unusual shapes associated with the rotational rainbow effect reported in previous studies. This is the only complex for which a rotational rainbow effect is observed at the chosen Ea values. Product angular distributions have also been measured for the NO à photodissociation product for the three complexes. NO-He produces nearly isotropic fragments, but the anisotropy parameter, ß, for NO-Ne and NO-Ar photofragments shows a surprising change in sign from negative to positive as Ea increases within the unstructured excitation profile. Franck-Condon selection of a broader distribution of geometries including more linear geometries at lower excitation energies and more T-shaped geometries at higher energies can account for the changing recoil anisotropy. Two-dimensional wavepacket calculations are reported to model the rotational state distributions and the bound-continuum absorption spectra.

Plutonium isotopes in the terrestrial environment at the Savannah River Site, USA: a long-term study.

This work presents the findings of a long-term plutonium (Pu) study at Savannah River Site (SRS) conducted between 2003 and 2013. Terrestrial environmental samples were obtained at the Savannah River National Laboratory (SRNL) in the A-Area. Plutonium content and isotopic abundances were measured over this time period by α particle and thermal ionization mass spectrometry (3STIMS). We detail the complete process of the sample collection, radiochemical separation, and measurement procedure specifically targeted to trace plutonium in bulk environmental samples. Total plutonium activities were determined to be not significantly above atmospheric global fallout. However, the (238)Pu/(239+240)Pu activity ratios attributed to SRS are substantially different than fallout due to past (238)Pu production on the site. The (240)Pu/(239)Pu atom ratios are reasonably consistent from year to year and are lower than fallout indicating an admixture of weapons-grade material, while the (242)Pu/(239)Pu atom ratios are higher than fallout values, again due to actinide production activities. Overall, the plutonium signatures obtained in this study reflect a distinctive mixture of weapons-grade, heat source, and higher burn-up plutonium with fallout material. This study provides a unique opportunity for developing and demonstrating a blue print for long-term low-level monitoring of trace plutonium in the environment.

Doppler-Resolved Kinetics of Saturation Recovery.

Frequency-modulated laser transient absorption has been used to monitor the ground-state rotational energy-transfer rates of CN radicals in a double-resonance, depletion recovery experiment. When a pulsed laser is used to burn a hole in the equilibrium ground-state population of one rotational state without velocity selection, the population recovery rate is found to depend strongly on the Doppler detuning of a narrow-band probe laser. Similar effects should be apparent for any relaxation rate process that competes effectively with velocity randomization. Alternative methods of extracting thermal rate constants in the presence of these non-thermal conditions are evaluated. Total recovery rate constants, analogous to total removal rate constants in an experiment preparing a single initial rotational level, are in good agreement with quantum scattering calculations, but are slower than previously reported experiments and show qualitatively different rotational state dependence between Ar and He collision partners. Quasi-classical trajectory studies confirm that the differing rotational state dependence is primarily a kinematic effect.