Assessing Arsenic Species in Foods Using Regularized Linear Regression of the Arsenic K-edge X-ray Absorption Near Edge Structure.

The toxicity and bioavailability of arsenic is heavily dependent on its speciation. Therefore, robust and accurate methods are needed to determine arsenic speciation profiles for materials related to public health initiatives, such as food safety. Here, X-ray spectroscopies are attractive candidates as they provide , nondestructive analyses of solid samples without perturbation to the arsenic species therein.

Predicting the Mixing Behavior of Aqueous Solutions Using a Machine Learning Framework.

The most direct approach to determining if two aqueous solutions will phase-separate upon mixing is to exhaustively screen them in a pair-wise fashion. This is a time-consuming process that involves preparation of numerous stock solutions, precise transfer of highly concentrated and often viscous solutions, exhaustive agitation to ensure thorough mixing, and time-sensitive monitoring to observe the presence of emulsion characteristics indicative of phase separation. Here, we examined the pair-wise mixing behavior of 68 water-soluble compounds by observing the formation of microscopic phase boundaries and droplets of 2278 unique 2-component solutions.

Uvulopalatopharyngoplasty.

Uvulopalatopharyngoplasty is a generally safe and widely accepted surgical procedure for the treatment of obstructive sleep apnea. Unfortunately, uvulopalatopharyngoplasty does not always result in success, and patients who initially experienced improvement in the severity of their obstructive sleep apnea may relapse. Proper patient selection and performing uvulopalatopharyngoplasty in conjunction with other surgical procedures that are directed at other sites of upper airway collapsibility may yield favorable outcomes.

Laser-Driven Calorimetry and Chemometric Quantification of Standard Reference Material Diesel/Biodiesel Fuel Blends.

Requirements for blends of drop-in petroleum/bio-derived fuels with specific thermophysical and thermochemical properties highlights the need for chemometric models that can predict these properties. Multivariate calibration methods were evaluated using the measured thermograms (i.e.

Placement of Short Implants: A Viable Alternative?

The placement of short implants, which measure less than 10 mm in length, requires the practitioner to have a thorough comprehension of implant dentistry to achieve acceptable results. Innovation of the rough-surface implant and the progression of the implant-abutment interface from an external hex to an internal connection have considerably influenced the longevity of short implants. Dentists are better equipped to serve their patients because the utilization of short implants may preclude the need for advanced surgical bone-grafting procedures.

Botox and Dermal Fillers: Review and Its Role in the Dental Office.

For the general dentist, the use of BTA and dermal fillers confers the ability to exert control over the soft tissues surrounding the mouth to better create a harmonious smile. The injection of BTA and fillers into the facial musculature and dermis requires a level of finesse to achieve the desired outcomes. A sound understanding of the mechanisms of action and the ability to manage potential complications are also necessary, because the dentist administering BTA and dermal fillers must be competent to the same level as other providers who have traditionally been the gatekeepers of such agents.

Chemometric Outlier Classification of 2D-NMR Spectra to Enable Higher Order Structure Characterization of Protein Therapeutics.

Protein therapeutics are vitally important clinically and commercially, with monoclonal antibody (mAb) therapeutic sales alone accounting for $115 billion in revenue for 2018.[1] In order for these therapeutics to be safe and efficacious, their protein components must maintain their high order structure (HOS), which includes retaining their three-dimensional fold and not forming aggregates. As demonstrated in the recent NISTmAb Interlaboratory nuclear magnetic resonance (NMR) Study[2], NMR spectroscopy is a robust and precise approach to address this HOS measurement need.

Grouping of complex substances using analytical chemistry data: A framework for quantitative evaluation and visualization.

A detailed characterization of the chemical composition of complex substances, such as products of petroleum refining and environmental mixtures, is greatly needed in exposure assessment and manufacturing. The inherent complexity and variability in the composition of complex substances obfuscate the choices for their detailed analytical characterization. Yet, in lieu of exact chemical composition of complex substances, evaluation of the degree of similarity is a sensible path toward decision-making in environmental health regulations.

Determination of physicochemical properties of petroleum derivatives and biodiesel using GC/MS and chemometric methods with uncertainty estimation.

The physicochemical properties of a substance, such as a fuel, can vary significantly with composition. Determining these properties with ASTM standard methods is both expensive and time-consuming, which has led to a desire to use chemometric modeling as an alternative. In this study, we compare the accuracy and robustness of two chemometric models, partial least squares (PLS) regression and support vector machine (SVM) with uncertainty estimation to determine how the physicochemical properties depend on the composition.

Evaluated Site-Specific Rate Constants for Reaction of Isobutane with H and CH: Shock Tube Experiments Combined with Bayesian Model Optimization.

Evaluated site-specific rate constants for the reactions of isobutane with CH and H were determined in a combined analysis of new shock tube experiments and existing literature data. In our shock tube experiments, CH radicals, produced from the pyrolysis of di- tert-butylperoxide, and H atoms, produced from the pyrolysis of CHI, were reacted with dilute mixtures of isobutane in argon at 870-1130 K and 140-360 kPa, usually with a radical chain inhibitor. Propene and isobutene, measured with GC/FID and MS, were quantified as characteristic of H-abstraction from the primary and tertiary carbons, respectively.

Classification of samples from NMR-based metabolomics using principal components analysis and partial least squares with uncertainty estimation.

Recent progress in metabolomics has been aided by the development of analysis techniques such as gas and liquid chromatography coupled with mass spectrometry (GC-MS and LC-MS) and nuclear magnetic resonance (NMR) spectroscopy. The vast quantities of data produced by these techniques has resulted in an increase in the use of machine algorithms that can aid in the interpretation of this data, such as principal components analysis (PCA) and partial least squares (PLS). Techniques such as these can be applied to biomarker discovery, interlaboratory comparison, and clinical diagnoses.

A scoring metric for multivariate data for reproducibility analysis using chemometric methods.

Process quality control and reproducibility in emerging measurement fields such as metabolomics is normally assured by interlaboratory comparison testing. As a part of this testing process, spectral features from a spectroscopic method such as nuclear magnetic resonance (NMR) spectroscopy are attributed to particular analytes within a mixture, and it is the metabolite concentrations that are returned for comparison between laboratories. However, data quality may also be assessed directly by using binned spectral data before the time-consuming identification and quantification.

Unsupervised classification of petroleum Certified Reference Materials and other fuels by chemometric analysis of gas chromatography-mass spectrometry data.

As feedstocks transition from conventional oil to unconventional petroleum sources and biomass, it will be necessary to determine whether a particular fuel or fuel blend is suitable for use in engines. Certifying a fuel as safe for use is time-consuming and expensive and must be performed for each new fuel. In principle, suitability of a fuel should be completely determined by its chemical composition.

Chemical kinetic model uncertainty minimization through laminar flame speed measurements.

Laminar flame speed measurements were carried for mixture of air with eight C hydrocarbons (propene, propane, 1,3-butadiene, 1-butene, 2-butene, -butene, -butane, and -butane) at the room temperature and ambient pressure. Along with C hydrocarbon data reported in a recent study, the entire dataset was used to demonstrate how laminar flame speed data can be utilized to explore and minimize the uncertainties in a reaction model for foundation fuels. The USC Mech II kinetic model was chosen as a case study.

Mechanical properties of β-HMX.

Background: For a full understanding of the mechanical properties of a material, it is essential to understand the defect structures and associated properties and microhardness indentation is a technique that can aid this understanding.

Results: The Vickers hardness on (010), {011} and {110} faces lay in the range of 304-363 MPa. The Knoop Hardnesses on the same faces lay in the range 314-482 MPa.

Evaluated Kinetics of the Reactions of H and CH3 with n-Alkanes: Experiments with n-Butane and a Combustion Model Reaction Network Analysis.

Presented is a combined experimental and modeling study of the kinetics of the reactions of H and CH3 with n-butane, a representative aliphatic fuel. Abstraction of H from n-alkane fuels creates alkyl radicals that rapidly decompose at high temperatures to alkenes and daughter radicals. In combustion and pyrolysis, the branching ratio for attack on primary and secondary hydrogens is a key determinant of the initial olefin and radical pool, and results propagate through the chemistry of ignition, combustion, and byproduct formation.

Kinetics of the reactions of H and CH3 radicals with n-butane: an experimental design study using reaction network analysis.

The oxidation of hydrocarbon fuels proceeds through the attack of small radicals such as H and CH3 on large molecules. These radicals abstract H atoms from the large molecules, which then usually proceed by β-scission to form C2H4 and C3H6. Quantifying these rates is critical to the development of chemical models for the oxidation of hydrocarbons.

Near-field three-dimensional radar imaging techniques and applications.

Three-dimensional radio frequency imaging techniques have been developed for a variety of near-field applications, including radar cross-section imaging, concealed weapon detection, ground penetrating radar imaging, through-barrier imaging, and nondestructive evaluation. These methods employ active radar transceivers that operate at various frequency ranges covering a wide range, from less than 100 MHz to in excess of 350 GHz, with the frequency range customized for each application. Computational wavefront reconstruction imaging techniques have been developed that optimize the resolution and illumination quality of the images.

Two-year chronic bioassay study of rats exposed to a 1.6 GHz radiofrequency signal.

The purpose of this study was to determine whether long-term exposure to a 1.6 GHz radiofrequency (RF) field would affect the incidence of cancer in Fischer 344 rats. Thirty-six timed-pregnant rats were randomly assigned to each of three treatment groups: two groups exposed to a far-field RF Iridium signal and a third group that was sham exposed.

Error analysis for estimation of trace vapor concentration pathlength in stack plumes.

Near-infrared hyperspectral imaging is finding utility in remote sensing applications such as detection and quantification of chemical vapor effluents in stack plumes. Optimizing the sensing system or quantification algorithms is difficult because reference images are rarely well characterized. The present work uses a radiance model for a down-looking scene and a detailed noise model for dispersive and Fourier transform spectrometers to generate well-characterized synthetic data.

Cephalexin: a channel hydrate.

The antibiotic cephalexin [systematic name: D-7-(2-amino-2-phenylacetamido)-3-methyl-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid] forms a range of isomorphic solvates, with the maximum hydration state of two water molecules formed only at high relative humidities.