Comparison of synthetic rhamnolipids as chemical precipitants for Pb, La, and Mg.

Identifying and exploiting cost-effective and green methods of metal recovery from natural and contaminated aqueous systems is widely recognized as necessary to supplement the supply of critical elements, decrease the environmental impacts associated with hardrock mining, and remediate metal-contaminated waters. This research examines a novel approach based on rhamnolipid-facilitated chemical precipitation of metals. Three techniques were assessed to remove the rhamnolipid:metal complex from solution: mixing only, and mixing following by filtration or centrifugation. Recent advances in the ability to synthetically produce rhamnolipid surfactants allowed investigation of a variety of rhamnolipid structures. Rhamnolipids differing in the length and number of hydrophobic tails were assessed to remove Pb, La, and Mg from single metal solutions. In general, removal increased with increased rhamnolipid hydrophobicity and with the addition of an active removal step (filtration or centrifugation). Filtration removed up to 96% of all metals while centrifugation removed up to 97% for Pb and La and 60% for Mg. Results suggest tailoring the rhamnolipid structure and removal methods may enable selective metal removal to achieve specific outcomes. Future studies in mixed-metal and real-world solutions will be needed to confirm the viability of these techniques in complex systems.

Removal of uranium from contaminated groundwater using monorhamnolipids and ion flotation.

Mining of uranium for defense-related purposes has left a substantial legacy of pollution that threatens human and environmental health. Contaminated waters in the arid southwest are of particular concern, as water resource demand and water scarcity issues become more pronounced. The development of remediation strategies to treat uranium impacted waters will become increasingly vital to meet future water needs. Ion flotation is one technology with the potential to address legacy uranium contamination. The green biosurfactant rhamnolipid has been shown to bind uranium and act as an effective collector in ion flotation. In this study, uranium contaminated groundwater (∼440 µg L-1 U) from the Monument Valley processing site in northeast Arizona was used as a model solution to test the uranium removal efficacy of ion flotation with biosynthetic (bio-mRL) and three synthetic monorhamnolipids with varying hydrophobic chain lengths: Rha-C10-C10, Rha-C12-C12, and Rha-C14-C14. At the groundwater's native pH 8, and at an adjusted pH 7, no uranium was removed from solution by any collector. However, at pH 6.5 bio-mRL and Rha-C10-C10 removed 239.2 µg L-1 and 242.4 µg L-1 of uranium, respectively. By further decreasing the pH to 5.5, bio-mRL was able to reduce the uranium concentration to near or below the Environmental Protection Agency maximum contaminant level of 30 µg L-1. For the Rha-C12-C12 and Rha-C14-C14 collector ligands, decreasing the pH to 7 or below reduced the foam stability and quantity, such that these collectors were not suitable for treating this groundwater. To contextualize the results, a geochemical analysis of the groundwater was conducted, and a consideration of uranium speciation is described. Based on this study, the efficacy of monorhamnolipid-based ion flotation in real world groundwater has been demonstrated with suitable solution conditions and collectors identified.

Recovery of Critical Metals from Aqueous Sources.

Critical metals, identified from supply, demand, imports, and market factors, include rare earth elements (REE), platinum group metals, precious metals, and other valuable metals such as lithium, cobalt, nickel, and uranium. Extraction of metals from U.S. saline aqueous, emphasizing saline, sources is explored as an alternative to hardrock ore mining. Potential aqueous sources include seawater, desalination brines, oil-and-gas produced waters, geothermal aquifers, and acid mine drainage, among others. A feasibility assessment reveals opportunities for recovery of lithium, strontium, magnesium, and several REE from select sources, in quantities significant for U.S. manufacturing and for reduction of U.S. reliance on international supply chains. This is a conservative assessment given that water quality data are lacking for a significant number of critical metals in certain sources. The technology landscape for extraction and recovery of critical metals from aqueous sources is explored, identifying relevant processes along with knowledge gaps. Our analysis indicates that aqueous mining would result in much lower environmental impacts on water, air, and land than ore mining. Preliminary assessments of the economics and energy consumption of recovery show potential for recovery of critical metals.

Biodegradability and Toxicity of Cellobiosides and Melibiosides.

In 2014, almost 16 million tons of surfactants were used globally for cleaning and industrial applications. As a result, massive quantities disperse into environmental compartments every day. There is great market interest in developing highly biodegradable, less-toxic, and renewable alternatives to currently used petroleum-based surfactants. Glycolipid surfactants, composed of a sugar head-group and lipid tail, are effective surfactants and emulsifiers with a high tolerance to electrolytes and are easily tailored to address specific needs. The green synthesis and surfactant characteristics of a suite of cellobiosides and melibiosides were recently described. The biodegradability and toxicity of 1°-alkyl-O-cellobiosides, 2°-alkyl-O-cellobiosides, and 1°-alkyl-O-melibiosides with straight-chain alkyl tails of 8, 10, and 12 are reported in this study. Biodegradability was assessed by quantifying mineralization (CO2 evolution). All of the glycosides were inherently biodegradable and most were readily biodegradable according to OECD and EPA definitions. The Microtox acute toxicity assay showed both chain length and head group had significant effects on toxicity, but most of the molecules were practically non-toxic according to EPA definitions with EC50 values > 100 mg L-1. Cytotoxicity to human lung (H1299) and keratinocyte cell lines (HaCaT) was measured by xCELLigence and MTS assays. Cytotoxicity values were comparable to similar glycosides previously reported. IC50 values were determined but, in general, exceeded surfactant concentrations that are found in the environment. These data demonstrate the promising nature of these molecules as green alternatives to petrochemical surfactants.

Biodegradability and toxicity of monorhamnolipid biosurfactant diastereomers.

Synthetic monorhamnolipids differ from biologically produced material because they are produced as single congeners, depending on the ß-hydroxyalkanoic acid used during synthesis. Each congener is produced as one of four possible diastereomers resulting from two chiral centers at the carbinols of the lipid tails [(R,R), (R,S), (S,R) and (S,S)]. We compare the biodegradability (CO2 respirometry), acute toxicity (Microtox assay), embryo toxicity (Zebrafish assay), and cytotoxicity (xCELLigence and MTS assays) of synthetic rhamnosyl-ß-hydroxydecanoyl-ß-hydroxydecanoate (Rha-C10-C10) monorhamnolipids against biosynthesized monorhamnolipid mixtures (bio-mRL). All Rha-C10-C10 diastereomers and bio-mRL were inherently biodegradable ranging from 34 to 92% mineralized. The Microtox assay showed all Rha-C10-C10 diastereomers and bio-mRL are slightly toxic according to the US EPA ecotoxicity categories with 5 min EC50 values ranging from 39.6 to 87.5 µM. The zebrafish assay showed that of 22 developmental endpoints tested, only mortality was observed at 120 h post fertilization; all Rha-C10-C10 diastereomers and bio-mRL caused significant mortality at 640 µM, except the Rha-C10-C10 (R,R) which showed no developmental effects. xCELLigence and MTS showed IC50 values ranging from 103.4 to 191.1 µM for human lung cell line H1299 after 72 h exposure. These data provide key information regarding Rha-C10-C10 diastereomers that is pertinent when considering potential applications.

High Prevalence of Sterile Pyuria in the Setting of Sexually Transmitted Infection in Women Presenting to an Emergency Department.

INTRODUCTION: The clinical presentations for sexually transmitted infections (STI) and urinary tract infections (UTI) often overlap, and symptoms of dysuria and urinary frequency/urgency occur with both STIs and UTIs. Abnormal urinalysis (UA) findings and pyuria are common in both UTIs and STIs, and confirmatory urine cultures are not available to emergency clinicians to aid in decision-making regarding prescribing antibiotics for UTIs. The objective of this study was to determine the frequency of sterile pyuria in women with confirmed STIs, as well as whether the absolute number of leukocytes on microscopy or nitrite on urine dipstick correlated with positive urine cultures in patients with confirmed STIs. We also sought to determine how many patients with STIs were inappropriately prescribed a UTI antibiotic. METHODS: We performed a retrospective chart review of patients aged 18-50 who had a urinalysis and pelvic examination in the emergency department (including cervical cultures), and tested positive for Neisseria gonorrhoeae, Chlamydia trachomatis, and/or Trichomonas vaginalis. Descriptive statistics were obtained for all variables, and associations between various findings were sought using the Fisher's exact test for categorical variables. We calculated comparison of proportions using the N-1 chi-squared analysis. RESULTS: A total of 1,052 female patients tested positive for Neisseria gonorrhoeae, Chlamydia trachomatis, and/or Trichomonas vaginalis and were entered into the database. The prevalence of pyuria in all cases was 394/1,052, 37% (95% confidence interval [CI] [0.34-0.40]). Of the cases with pyuria, 293/394, 74% (95% CI [0.70-0.78]) had sterile pyuria with negative urine cultures. The prevalence of positive urine cultures in our study population was 101/1,052, 9.6% (95% CI [0.08-0.11]). Culture positive urines had a mean of 34 leukocytes per high-power field, and culture negative urines had a mean of 24 leukocytes per high-power field, with a difference of 10, (95% CI [3.46-16.15]), which was statistically significant (p=0.003). Only 123 cases tested positive for nitrite on the urinalysis dipstick; 50/123, 41% (95% CI [0.32-0.49]) had positive urine cultures, and 73/123, 59% (95% CI [0.51-0.68]) had negative urine cultures. Nitrite-positive urines were actually 18% more likely to be associated with negative urine cultures in the setting of positive STI cases, (95% CI [4.95-30.42], p=0.0048). Antibiotics were prescribed for 295 patients with suspected UTI. Of these, 195/295, 66% (95% CI [0.61-0.71]) had negative urine cultures, and 100/295, 34% (0.33, 95% CI [0.28-0.39]) had positive urine cultures. Chi-square analysis yielded a difference of these proportions of 32% (95% CI [23.92-39.62], p<0.0001). CONCLUSION: This study demonstrated that in female patients with STIs who have pyuria, there is a high prevalence of sterile pyuria. Our results suggest that reliance on pyuria or positive nitrite for the decision to add antimicrobial therapy empirically for a presumed urinary tract infection in cases in which an STI is confirmed or highly suspected is likely to result in substantial over-treatment.

Rhamnolipid biosurfactant complexation of rare earth elements.

Rare earth elements (REE) are vital for modern technologies and considered critical materials. This study investigated monorhamnolipid biosurfactant interactions with REE as the basis for REE recovery technology. Conditional stability constants (log ß), measured using a resin-based ion exchange method, are reported for 16 REE and metals. These results were combined with existing data for 10 other metals to assess comparative strength and determinants of binding. The stability constants could be divided into three groups: weakly, moderately, and strongly bound. The REE were all in the strongly bound group (UO22+, Eu3+, Nd3+, Tb3+, Dy3+, La3+, Cu2+, Al3+, Pb2+, Y3+, Pr3+, and Lu3+) with log ß ranging from 9.82 to 8.20. The elements Cd2+, In3+, Zn2+, Fe3+, Hg2+, and Ca2+ were moderately bound with log ß=7.17-4.10. Finally, Sr2+, Co2+, Ni2+, UO22+, Ba2+, Mn2+, Mg2+, Rb+, and K+ were weakly bound with log ß=3.95-0.96. Two log ß values are reported for the uranyl ion due to two distinct binding regions. A mixed metals study and associated selectivity coefficients confirmed monorhamnolipids preferentially remove metals with large log ß values over those with smaller values. Preferential complexation by monorhamnolipids may constitute a green pathway for recovery of REE from alternative, non-traditional sources.

Evolution of Aggregate Structure in Solutions of Anionic Monorhamnolipids: Experimental and Computational Results.

The evolution of solution aggregates of the anionic form of the native monorhamnolipid (mRL) mixture produced by Pseudomonas aeruginosa ATCC 9027 is explored at pH 8.0 using both experimental and computational approaches. Experiments utilizing surface tension measurements, dynamic light scattering, and both steady-state and time-resolved fluorescence spectroscopy reveal solution aggregation properties. All-atom molecular dynamics simulations on self-assemblies of the most abundant monorhamnolipid molecule, l-rhamnosyl-ß-hydroxydecanoyl-ß-hydroxydecanoate (Rha-C10-C10), in its anionic state explore the formation of aggregates and the role of hydrogen bonding, substantiating the experimental results. At pH 8.0, at concentrations above the critical aggregation concentration of 201 µM but below ∼7.5 mM, small premicelles exist in solution; above ∼7.5 mM, micelles with hydrodynamic radii of ∼2.5 nm dominate, although two discrete populations of larger lamellar aggregates (hydrodynamic radii of ∼10 and 90 nm) are also present in solution in much smaller number densities. The critical aggregation number for the micelles is determined to be ∼26 monomers/micelle using fluorescence quenching measurements, with micelles gradually increasing in size with monorhamnolipid concentration. Molecular dynamics simulations on systems with between 10 and 100 molecules of Rha-C10-C10 indicate the presence of stable premicelles of seven monomers with the most prevalent micelle being ∼25 monomers and relatively spherical. A range of slightly larger micelles of comparable stability can also exist that become increasing elliptical with increasing monomer number. Intermolecular hydrogen bonding is shown to play a significant role in stabilization of these aggregates. In total, the computational results are in excellent agreement with the experimental results.

Simple infrared thermometry in fever detection: consideration in mass fever screening.

OBJECTIVE: The need to rapidly screen patients during outbreaks has prompted Cutaneous Infrared Thermometry (CIT) use. Little is known of CIT performance in this context. What are the performance characteristics of simple CIT in detecting fever? DESIGN: Prospective cohort, sequential convenience sample. PARTICIPANTS: All patients presenting to the study Emergency Department for care. INTERVENTION: CIT and oral temperature measurements. MAIN OUTCOMES: Fever defined as oral temperature≥38°C. CIT is measured simultaneously with oral temperatures. Comparisons of temperatures are expressed as means and 95% confidence intervals. Means are compared using Student's t test. Limits of agreement are measured using Bland-Altman. Receiver operating characteristics are determined. RESULTS: There are 548 cases comprising 224 males, 324 females, with mean age 26 years. The mean temperature difference is 12.95°C, (13.18-9.08°C) p≤0.0001. Bland-Altman demonstrates bias at 8.680 (-9.084 to -8.275) p≤0.0001 with upper and lower level bias values of 18.124 (18.819-17.435) and 0.768 (0.076-1.459), respectively. Based on Receiver Operator Characteristics analysis, detection of hyperpyrexia at a CIT of 35.3°C provided sensitivity of 0.236 (0.143-0.359), specificity 0.977 (0.959-0.989), positive predictive value 0.589 (0.325-0.810), negative predictive value 0.904 (0.891-0.919), and accuracy of 0.888 (0.861-0.913). CONCLUSIONS: The use of a readily available CIT measurement device predicted hyperpyrexia about 59 percent of the time and the absence of hyperpyrexia about 90 percent of the time. This is consistent with previous reports of more complex infrared measurement devices. Although commonly used in mass fever screening, the current performance characteristics of CIT are limited and may add little to detection of target diseases in a mass screening context.

Comparison of two protocols for pulseless cardiopulmonary arrest: vasopressin combined with epinephrine versus epinephrine alone.

INTRODUCTION: Survival from pulseless cardiac arrest typically is dismal. Some suggest that adding vasopressin to epinephrine as a cardiovascular stimulant can improve outcomes. PROBLEM: This study compares survival outcomes using epinephrine verses vasopressin and epinephrine in persons with pulseless cardiac arrest. METHODS: This is a retrospective, cohort evaluation of two resuscitative protocols (P1-epinephrine or P2-vasopressin with epinephrine) in a tiered response, community emergency medical service (EMS) with an approximately 100,000 catchment area. Cases are defined as 18 years or older determined to be in pulseless cardiac arrest. Outcomes were survival to emergency department arrival, to 24 hours, and to hospital discharge. Data were entered into Microsoft Office Excel® and processed using Analyze-it® for continuous and categorical data and Epi-Info® for odds ratios with confidence intervals. RESULTS: There were 204 cases (60.3% males and 39.7% females) who met the inclusion criteria. Thirteen cases received electrical therapy only, and were dropped from analysis, leaving 191 (93.6%) who were included in the study; P1 to 85 (44.5%) and P2 to 106 (55.5%). Younger age was associated with improved survival to discharge home in both protocols, p = 0.003 (95% CI = 0.004-0.010). No difference in survival was noted at the levels of emergency department arrival OR 1.42 (95% CI = 0.73, 2.76) p = 0.26; 24 hour survival OR 0.54 (95% CI = 0.22-1.30) p = 0.133, or discharge home OR = 1.81 (95% CI = 0.49-6.88) p = 0.319. CONCLUSIONS: This study in a community EMS did not demonstrate improved survival with the addition of vasopressin to epinephrine for pulseless cardiac arrest.

Multiple information sources in the analysis of a disaster.

OBJECTIVE: Disasters are complex events making epidemiologic studies and determination of accurate denominators difficult due to the poor nature of available records. However, these data are essential to perform useful calculations and accurate descriptions of disaster medical impacts. This study was undertaken to identify the availability and utility of various information sources in the analysis of a mass casualty disaster. In addition, characteristics of cases presenting for care are described. DESIGN: This is a retrospective cohort study abstracting medical records and other documents relating to an explosion and fire. Public domain documents are obtained by written request or by filing a Freedom of Information Act (FOIA) request. SETTING: A rural EMS and tertiary hospital. CASES: Individuals directly exposed to the forces of the explosion. OUTCOME MEASURES: The number of cases detected by various information sources. In addition, the demographics, dispositions, and nature of the physical injuries of the cases are reported. RESULTS: Seven sources of case information were identified. The most cases were identified by investigative agencies (33) and the fewest by medical records (18). Rates include; injury 0.68, admission 0.20, and operative 0.14, with no deaths. Case locations during the explosion were determined for all cases. No association was noted between admission and location in the building. CONCLUSIONS: This study demonstrates the availability and usefulness of data in the public domain. Using FOIA requests or partnerships with public or private agencies may more clearly define denominator data in epidemiologic evaluations of disasters.

Music training and semantic clustering in college students.

College students with 5 or more years of music training recalled significantly more words from a 16-item word list than did students with 0-4 years of training. The superior recall of the extensively trained students linked to better application of a semantic-clustering strategy across a series of 3 test trials. Music education and language experience may have similar influences on the development of verbal memory.

Nuclear terrorism.

Recent events have heightened awareness of the potential for terrorist attacks employing nonconventional weaponry such as biological agents and radiation. Historically, the philosophy of nuclear risk has focused on global or strategic nuclear exchanges and the resulting damage from large-scale releases. Currently, nuclear accidents or terrorist attacks involving low-level or regional release of radiation are considered the most likely events. Thus far, there have been several regional radiation incidents exposing hundreds of thousands of people to radiation, but there have been only a limited number of significant contaminations resulting in death. There are several different types of radioactive particles that differ in mass, extent of radiation emitted, and the degree to which tissue penetration occurs. Radiation affects its toxicity on biological systems by ionization, which creates tissue damage by the generation of free radicals, disruption of chemical bonds, and directly damaging cellular DNA and enzymes. The extent of damage depends on the type of radioisotope and the radiation dose. Radiation doses exceeding 2 to 10 Gy are considered lethal. Optimal management of radiation casualties requires knowledge of the type and dose of radiation received, a recognition of the manifestations of radiation sickness, and the use of standard medical care, decontamination, and decorporation techniques.

Impact of a tornado on a community hospital.

A significant tornado passed through the Oklahoma City metropolitan area on May 3,1999. This study was undertaken at St Michael Hospital (Oklahoma City, Okla) to describe the impact on a community hospital's emergency department close to the tornado strike zone. Cases were defined as patients receiving diagnostic procedures, care, and interventions at the study hospital's emergency department for injuries related to the tornado. Medical records were abstracted and entered into a custom database; descriptive analysis was done using Microsoft Excel 97. A total of 147 patients met the study criteria, with an admission rate of 31 (21%) [corrected] of 147 patients (6 [19.4%] of 31 to the operating room, 4 [12.9%] of 31 to the intensive care unit, and 21 [67.7%] [corrected] of 31 to ward beds). In addition, 4 (2.7%) of the 147 patients were transferred to tertiary-care facilities (3 pediatric patients with head injuries and 1 adult patient with spinal cord injury). Complex soft tissue wounds, head injuries, and fractures were the most common diagnoses. The number of head-injured patients arriving alive to the emergency department was higher than expected. Most soft tissue wounds were closed primarily in the emergency department. The authors recommend that preexisting referral patterns for trauma and specialty care should be a part of the overall disaster plans for community hospitals.