Identification of common textile microplastics via autofluorescence spectroscopy coupled with k-means cluster analysis.

Microplastics are an emerging anthropogenic pollutant risk with a significant body of research dedicated to understanding the implications further. To generate the databases required to characterize the impact of microplastics on our environment, and improve recovery and recycling of current plastic materials, we need rapid, in-line characterization that can distinguish individual polymer types. Here, autofluorescence spectroscopy was investigated as an alternative characterization method to the current leading techniques based on vibrational spectroscopy. It was confirmed that the autofluorescence of seven common textile polymers (acrylic, polyester, nylon, polyethylene, polypropylene, cellulose/cotton, wool) arose due to the cluster-triggered emission phenomenon. Both simulated polymer aging via photooxidation and dyeing of the polymers were found to affect the resultant autofluorescence spectra. A total of 1485 spectra from 39 unique sample groups (polymer type, colour, and degree of photooxidation) were analysed via machine learning (k-means cluster analysis). Correct identification of the polymer type was achieved in 71% of the cases from only eight input values (normalized intensity values at three autofluorescence emission wavelengths, the total autofluorescence emission intensity, the sample RGB colour values, and the sample shape). This represents a significant step towards automated polymer identification at the sub-second time scales required for the in-line characterization of microplastics.

Dissolution dynamics of a binary switchable hydrophilicity solvent-polymer drop into an acidic aqueous phase.

Switchable hydrophilicity solvents (SHSs) are solvents defined by their ability to switch from their hydrophobic form to a hydrophilic form when brought into contact with an acidic trigger such as CO2. As a consequence, SHSs qualify as promising alternatives to volatile organic compounds during industrial solvent extraction processes, as greener and inexpensive methods can be applied to separate and recover SHSs. Furthermore, because of their less volatile nature, SHSs are less flammable and so increase the safety of a larger scale extraction process. In this work, we study the dynamics and in-drop phase separation during the dissolution process of a drop composed of a SHS and a polymer, triggered by an acid in the surrounding aqueous environment. From 70 different experimental conditions, we found a scaling relationship between the drop dissolution time and the initial volume with an overall scaling coefficient of ∼0.53. We quantitatively assessed and found a shorter dissolution time related to a decrease in the pH of the aqueous phase or an increase in the initial polymer concentration in the drop. Examining the internal state of the drop during the dissolution revealed an in-drop phase separation behavior, resulting in a porous morphology of the final polymer particle. Our experimental results provide a microscopic view of the SHS dissolution process from droplets, and findings may help design SHS extraction processes for particle formation from emulsions.

Temperature and Pressure Dependent Kinetics of QOOH Decomposition and Reaction with O2: Experimental and Theoretical Investigations of QOOH Radicals Derived from Cl + (CH3)3COOH.

QOOH radicals are key species in autoignition, produced by internal isomerizations of RO2 radicals, and are central to chain branching reactions in low-temperature combustion. The kinetics of QOOH radical decomposition and reaction with O2 have been determined as a function of temperature and pressure, using observations of OH radical production and decay following H-atom abstraction from t-butyl hydroperoxide ((CH3)3COOH) by Cl atoms to produce QOOH (CH2(CH3)2COOH) radicals. The kinetics of QOOH decomposition have been investigated as a function of temperature (251-298 K) and pressure (10-350 Torr) in helium and nitrogen bath gases, and those of the reaction between QOOH and O2 have been investigated as a function of temperature (251-304 K) and pressure (10-100 Torr) in He and N2. Decomposition of the QOOH radical was observed to display temperature and pressure dependence, with a barrier height for the decomposition of (44.7 ± 4.0) kJ mol-1 determined by master equation fitting to the experimental data. The rate coefficient for the reaction between QOOH and O2 was determined to be (5.6 ± 1.7) × 10-13 cm3 s-1 at 298 K, with no significant dependence on pressure, and can be described by the Arrhenius parameters A = (7.3 ± 6.8) × 10-14 cm3 s-1 and Ea = -(5.4 ± 2.1) kJ mol-1 in the temperature range of 251-304 K. This work represents the first measurements of any QOOH radical kinetics as a function of temperature and pressure.

An Experimental and Theoretical Study of the Thermal Decomposition of C4H6 Isomers.

The chemistry of small unsaturated hydrocarbons, such as 1,3-butadiene (1,3-C4H6), 1,2-butadiene (1,2-C4H6), 2-butyne (2-C4H6), and 1-butyne (1-C4H6), is of central importance to the modeling of combustion systems. These species are important intermediates in combustion processes, and yet their high-temperature chemistry remains poorly understood, with various dissociation and isomerization pathways proposed in the literature. Here we investigate the thermal decompositions of 1,3-C4H6, 1,2-C4H6, 2-C4H6, and 1-C4H6 inside a diaphragmless shock tube, at postshock total pressures of 26-261 Torr and temperatures ranging from 1428 to 2354 K, using laser schlieren densitometry. The experimental work was complemented by high-level ab initio calculations, which collectively provide strong evidence that formally direct dissociation is the major channel for pyrolysis of 1,3-C4H6 and 2-C4H6; these paths have not been previously reported but are critical to reconciling the current work and disparate literature reports. The reaction mechanism presented here simulates the current experiments and experimental data from the literature very well. Pressure- and temperature-dependent rate coefficients are given for the isomerization, formally direct, and direct dissociation paths.

Observation of a new channel, the production of CH3, in the abstraction reaction of OH radicals with acetaldehyde.

Using laser flash photolysis coupled to photo-ionization time-of-flight mass spectrometry (PIMS), methyl radicals (CH3) have been detected as primary products from the reaction of OH radicals with acetaldehyde (ethanal, CH3CHO) with a yield of ∼15% at 1-2 Torr of helium bath gas. Supporting measurements based on laser induced fluorescence studies of OH recycling in the OH/CH3CHO/O2 system are consistent with the PIMS study. Master equation calculations suggest that the origin of the methyl radicals is from prompt dissociation of chemically activated acetyl products and hence is consistent with previous studies which have shown that abstraction, rather than addition/elimination, is the sole route for the OH + acetaldehyde reaction. However, the observation of a significant methyl product yield suggests that energy partitioning in the reaction is different from the typical early barrier mechanism where reaction exothermicity is channeled preferentially into the newly formed bond. The master equation calculations predict atmospheric yields of methyl radicals of ∼9%. The implications of the observations in atmospheric and combustion chemistry are briefly discussed.

Kinetic study of the OH + glyoxal reaction: experimental evidence and quantification of direct OH recycling.

The kinetics of the OH + glyoxal, (HCO)2, reaction have been studied in N2 and N2/O2 bath gas from 5-80 Torr total pressure and 212-295 K, by monitoring the OH decay via laser induced fluorescence (LIF) in excess (HCO)2. The following rate coefficients, kOH+(HCO)2 = (9.7 ± 1.2), (12.2 ± 1.6), and (15.4 ± 2.0) × 10(-12) cm(3) molecule(-1) s(-1) (where errors represent a combination of statistical errors at the 2σ level and estimates of systematic errors) were measured in nitrogen at temperatures of 295, 250, and 212 K, respectively. Rate coefficient measurements were observed to be independent of total pressure but decreased following the addition of O2 to the reaction cell, consistent with direct OH recycling. OH yields, ΦOH, for this reaction were quantified experimentally for the first time as a function of total pressure, temperature, and O2 concentration. The experimental results have been parametrized using a chemical scheme where a fraction of the HC(O)CO population promptly dissociates to HCO + CO, the remaining HC(O)CO either dissociates thermally or reacts with O2 to give CO2, CO, and regenerate OH. A maximum ΦOH of (0.38 ± 0.02) was observed at 212 K, independent of total pressure, suggesting that ∼60% of the HC(O)CO population promptly dissociates upon formation. Qualitatively similar behavior is observed at 250 K, with a maximum ΦOH of (0.31 ± 0.03); at 295 K, the maximum ΦOH decreased further to (0.29 ± 0.03). From the parametrization, an OH yield of ΦOH = 0.19 is calculated for 295 K and 1 atm of air. It is shown that the proposed mechanism is consistent with previous chamber studies. While the fits are robust, experimental evidence suggests that the system is influenced by chemical activation and cannot be fully described by thermal rate coefficients. The atmospheric implications of the measurements are briefly discussed.

Mechanism of the reaction of OH with alkynes in the presence of oxygen.

Previous work has shown that the branching ratio of the reaction of OH/C2H2/O2 to glyoxal and formic acid is dependent on oxygen fraction, and a significant component of the product yield under atmospheric conditions is formed from reaction of chemically activated OH-C2H2 adduct. In this article, isotopic substitution is used to determine the mechanism of the OH/C2H2/O2 reaction resolving previous contradictory observations in the literature. Using laser flash photolysis and probing OH concentrations via laser induced fluorescence, a rate coefficient of kHO-C2H2+O2 = (6.17 ± 0.68) × 10(-12) cm(3) molecule(-1) s(-1) is determined at 298 K from the analysis of biexponential OH decays in the presence of C2H2 and low concentrations of O2. The studies have been extended to propyne and but-2-yne. The reactions of OH with propyne and but-2-yne have been studied as a function of pressure in the absence of oxygen. The reaction of OH with propyne is in the fall off region from 2-25 Torr of nitrogen at room temperature. A pressure independent value of (4.21 ± 0.47) × 10(-12) cm(3) molecule(-1) s(-1) was obtained from averaging the eight independent measurements at 25 and 75 Torr. The reaction of OH with but-2-yne at 298 K is pressure independent (5-25 Torr N2) with a value of (1.87 ± 0.19) × 10(-11) cm(3) molecule(-1) s(-1). Analysis of biexpontial OH decays in alkyne/low O2 conditions gives the following rate coefficients at 298 K: kHO-C3H4+O2 = (8.00 ± 0.82) × 10(-12) cm(3) molecule(-1) s(-1) and kHO-C4H6+O2 = (6.45 ± 0.68) × 10(-12) cm(3) molecule(-1) s(-1). The branching ratio of bicarbonyl to organic acid in the presence of excess oxygen also shows an oxygen fraction dependence for propyne and but-2-yne, qualitatively similar to that for acetylene. For an oxygen fraction of 0.2 at 298 K, pressure independent yields of methylglyoxal (0.70 ± 0.03) and biacetyl (0.74 ± 0.03) were determined for the propyne and but-2-yne systems, respectively. The yield of acid increases with temperature from 212-500 K. Master equation calculations show that, under atmospheric conditions, the acetyl cofragment of organic acid production will dissociate, consistent with experimental observations.

Autofluorescence spectroscopy for quantitative analysis of cellulose nanocrystals.

The ability to determine the physicochemical properties of nanoparticles, such as cellulose nanocrystals, in suspension is critically important to maximize their potential. Currently, various techniques are required to ascertain different properties, which results in a laborious analysis procedure. Here, autofluorescence arising from the cluster-triggered emission (CTE) photoluminescence mechanism is utilized as an analytical spectroscopic tool to determine multiple properties from one data acquisition sequence. This study confirms that key properties - including the nanoparticle concentration in suspension, the critical concentration for liquid crystal formation, and the surface charge content - can be obtained simultaneously. Measured values are accurate to within 10% of conventional techniques with average residual errors of 0.4 wt% for the critical concentration, and 11 mmol kg-1 CNC for the surface charge content. This charge-coupled device (CCD) sensor-based methodology is rapid and does not require the addition of further chemicals. These results support the theory behind CTE and represent a new opportunity for quantitatively analysing non-aromatic, heteroatom-containing nanoparticles in flow based on understanding their inter- and intra-particle interactions.

Patient-reported symptoms and quality of life during treatment with tamoxifen or raloxifene for breast cancer prevention: the NSABP Study of Tamoxifen and Raloxifene (STAR) P-2 trial.

CONTEXT: Tamoxifen has been approved for breast cancer risk reduction in high-risk women, but how raloxifene compares with tamoxifen is unknown. OBJECTIVE: To compare the differences in patient-reported outcomes, quality of life [QOL], and symptoms in Study of Tamoxifen and Raloxifene (STAR) participants by treatment assignment. DESIGN, SETTING, PARTICIPANTS, AND INTERVENTIONS: STAR was a double-blind, randomized phase 3 prevention trial designed to evaluate the relative efficacy of raloxifene vs tamoxifen in reducing the incidence of invasive breast cancer in high-risk postmenopausal women. Between July 1, 1999, and November 4, 2004, 19,747 participants were enrolled at centers throughout North America, with a median potential follow-up time of 4.6 years (range, 1.2-6.5 years). Patient-reported symptoms were collected from all participants using a 36-item symptom checklist. Quality of life was measured with the Medical Outcomes Study Short-Form Health Survey (SF-36), the Center for Epidemiologic Studies-Depression (CES-D), and the Medical Outcomes Study Sexual Activity Questionnaire in a substudy of 1983 participants, median potential follow-up 5.4 years (range, 4.6-6.0 years). Questionnaires were administered before treatment, every 6 months for 60 months and at 72 months. MAIN OUTCOME MEASURES: Primary QOL end points were the SF-36 physical (PCS) and mental (MCS) component summaries. RESULTS: Among women in the QOL analysis, mean PCS, MCS, and CES-D scores worsened modestly over the study's 60 months, with no significant difference between the tamoxifen (n = 973) and raloxifene (n = 1010) groups (P>.2). Sexual function was slightly better for participants assigned to tamoxifen (age-adjusted repeated measure odds ratio, 1.22%; 95% CI, 1.01-1.46). Of the women in the symptom assessment analyses, the 9769 in the raloxifene group reported greater mean symptom severity over 60 months of assessments than the 9743 in the tamoxifen group for musculoskeletal problems (1.15 vs 1.10, P = .002), dyspareunia (0.78 vs 0.68, P<.001), and weight gain (0.82 vs 0.76, P<.001). Women in the tamoxifen group reported greater mean symptom severity for gynecological problems (0.29 vs 0.19, P<.001), vasomotor symptoms (0.96 vs 0.85, P<.001), leg cramps (1.10 vs 0.91, P<.001), and bladder control symptoms (0.88 vs 0.73, P<.001). CONCLUSIONS: No significant differences existed between the tamoxifen and raloxifene groups in patient-reported outcomes for physical health, mental health, and depression, although the tamoxifen group reported better sexual function. Although mean symptom severity was low among these postmenopausal women, those in the tamoxifen group reported more gynecological problems, vasomotor symptoms, leg cramps, and bladder control problems, whereas women in the raloxifene group reported more musculoskeletal problems, dyspareunia, and weight gain. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00003906.

Optimum growth initiation time for shoot buds of deciduous plants in a temperate climate.

A model predicting optimum growth initiation times for shoot buds of deciduous plants has been derived from simple assumptions based on maximizing average annual photosynthesis as a function of photosynthetic rates, length of growing season and the probability of late frost. This formulation predicts that optimum bud initiation time is sensitive to the variance in the frost probability but is independent of the average photosynthetic rate. Predicted optimal initiation times are only slightly affected by substantial changes in the length of the growing season (over a considerable change in latitude) except when the growing season is very short. The advantage of maximum frost resistance is also greatest in very short growing seasons. It is pointed out that the optimum time of leaf senescence at the end of the growing season must be based on more complex criteria than the time of growth initiation. Certain difficulties in interpreting bud break data from tree transplant experiments are discussed.

Interception of excited vibrational quantum states by O2 in atmospheric association reactions.

Bimolecular reactions in Earth's atmosphere are generally assumed to proceed between reactants whose internal quantum states are fully thermally relaxed. Here, we highlight a dramatic role for vibrationally excited bimolecular reactants in the oxidation of acetylene. The reaction proceeds by preliminary adduct formation between the alkyne and OH radical, with subsequent O(2) addition. Using a detailed theoretical model, we show that the product-branching ratio is determined by the excited vibrational quantum-state distribution of the adduct at the moment it reacts with O(2). Experimentally, we found that under the simulated atmospheric conditions O(2) intercepts ~25% of the excited adducts before their vibrational quantum states have fully relaxed. Analogous interception of excited-state radicals by O(2) is likely common to a range of atmospheric reactions that proceed through peroxy complexes.

Are lateral electronic portal images adequate for accurate on-line daily targeting of the prostate? Results of a prospective study.

The purpose of this report was to evaluate the magnitude of the error that would be introduced if only a lateral (LAT) portal image, as opposed to a pair of orthogonal images, was used to verify and correct daily setup errors and organ motion in external beam radiation therapy (EBRT) of prostate cancer. The 3-dimensional (3D) coordinates of gold markers from 12 consecutive prostate patients were reconstructed using a pair of orthogonal images. The data were re-analyzed using only the LAT images. Couch moves from the 2-dimensional (2D)-only data were compared with the complete 3D data set. The 2D-only data provided couch moves that differed on average from the 3D data by 2.3 +/- 3.0, 0.0 +/- 0.0, and 0.8 +/- 1.0 mm in the Lat, AP, and SI directions, respectively. Along AP and SI axes, the LAT image provided positional information similar to the orthogonal pair. The error along the LAT axis may be acceptable provided lateral margins are large enough. A LAT-only setup protocol reduces patient treatment times and increases patient throughput. In most circumstances, with exceptions such as morbidly obese patients, acquisition of only a LAT image for daily targeting of the prostate will provide adequate positional precision.