We report precision determinations of the beam-normal single spin asymmetries (A_{n}) in the elastic scattering of 0.95 and 2.18 GeV electrons off ^{12}C, ^{40}Ca, ^{48}Ca, and ^{208}Pb at very ...forward angles where the most detailed theoretical calculations have been performed. The first measurements of A_{n} for ^{40}Ca and ^{48}Ca are found to be similar to that of ^{12}C, consistent with expectations and thus demonstrating the validity of theoretical calculations for nuclei with Z≤20. We also report A_{n} for ^{208}Pb at two new momentum transfers (Q^{2}) extending the previous measurement. Our new data confirm the surprising result previously reported, with all three data points showing significant disagreement with the results from the Z≤20 nuclei. These data confirm our basic understanding of the underlying dynamics that govern A_{n} for nuclei containing ≲50 nucleons, but point to the need for further investigation to understand the unusual A_{n} behavior discovered for scattering off ^{208}Pb.
One of the most widely cited advantages of laser-induced breakdown spectroscopy (LIBS) is that it does not require sample preparation, but this may also be the biggest factor holding it back from ...becoming a mature analytical technique like LA-ICP-MS, ICP-OES, or XRF. While there are certain specimen types that have enjoyed excellent LIBS results without any sample treatment (mostly homogeneous solids such as metals, glass, and polymers), the possible applications of LIBS have been greatly expanded through the use of sample preparation techniques that have resulted in analytical performance (i.e., limits of detection, accuracy, and repeatability) on par with XRF, ICP-OES, and often ICP-MS.
This review highlights the work of many LIBS researchers who have developed, adapted, and improved upon sample preparation techniques for various specimen types in order to improve the quality of the analytical data that LIBS can produce in a large number of research domains. Strategies, not only for solids, but also liquids, gases, and aerosols are discussed, including newly developed nanoparticle enhancement and biological imaging and tagging techniques.
•Sample preparation techniques for LIBS on solids, liquids and gases•Sample preparation for LIBS in biological applications•Sample preparation for enhancing LIBS performances
1 Smooth Muscle Research Group and the Department of Physiology and Biophysics, University of Calgary, Calgary, Alberta, Canada; 2 Department of Pharmacology and Toxicology, Michigan State ...University, East Lansing, Michigan; and 3 Department of Electrical and Computer Engineering, University of Calgary, Calgary, Alberta, Canada
Submitted 28 February 2006
; accepted in final form 30 March 2006
This study examined whether inward rectifying K + (K IR ) channels facilitate cell-to-cell communication along skeletal muscle resistance arteries. With the use of feed arteries from the hamster retractor muscle, experiments examined whether K IR channels were functionally expressed and whether channel blockade attenuated the conduction of acetylcholine-induced vasodilation, an index of cell-to-cell communication. Consistent with K IR channel expression, this study observed the following: 1 ) a sustained Ba 2+ -sensitive, K + -induced dilation in preconstricted arteries; 2 ) a Ba 2+ -sensitive inwardly rectifying K + current in arterial smooth muscle cells; and 3 ) K IR 2.1 and K IR 2.2 expression in the smooth muscle layer of these arteries. It was subsequently shown that the discrete application of acetylcholine elicits a vasodilation that conducts with limited decay along the feed artery wall. In the presence of 100 µM Ba 2+ , the local and conducted response to acetylcholine was attenuated, a finding consistent with a role for K IR in facilitating cell-to-cell communication. A computational model of vascular communication accurately predicted these observations. Control experiments revealed that in contrast to Ba 2+ , ATP-sensitive- and large-conductance Ca 2+ activated-K + channel inhibitors had no effect on the local or conducted vasodilatory response to acetylcholine. We conclude that smooth muscle K IR channels play a key role in facilitating cell-to-cell communication along skeletal muscle resistance arteries. We attribute this facilitation to the intrinsic property of negative slope conductance, a biophysical feature common to K IR 2.1- and 2.2-containing channels, which enables them to increase their activity as a cell hyperpolarizes.
gap junctions; intercellular conduction; K + channels; skeletal muscle arteries
Address for reprint requests and other correspondence: D. G. Welsh, Dept. of Physiology and Biophysics, HM-86, Heritage Medical Research Bldg., 3330 Hospital Dr., NW, Calgary, Alberta, Canada, T2N-4N1 (e-mail: dwelsh{at}ucalgary.ca )
The biosynthetic dogma of ribosomally synthesized and posttranslationally modified peptides (RiPP) involves enzymatic intermolecular modification of core peptide motifs in precursor peptides. The ...plant-specific BURP-domain protein family, named after their four founding members, includes autocatalytic peptide cyclases involved in the biosynthesis of side-chain-macrocyclic plant RiPPs. Here we show that AhyBURP, a representative of the founding Unknown Seed Protein-type BURP-domain subfamily, catalyzes intramolecular macrocyclizations of its core peptide during the sequential biosynthesis of monocyclic lyciumin I via glycine-tryptophan crosslinking and bicyclic legumenin via glutamine-tyrosine crosslinking. X-ray crystallography of AhyBURP reveals the BURP-domain fold with two type II copper centers derived from a conserved stapled-disulfide and His motif. We show the macrocyclization of lyciumin-C(sp
)-N-bond formation followed by legumenin-C(sp
)-O-bond formation requires dioxygen and radical involvement based on enzyme assays in anoxic conditions and isotopic labeling. Our study expands enzymatic intramolecular modifications beyond catalytic moiety and chromophore biogenesis to RiPP biosynthesis.
A method for the quantitative elemental analysis of surface soil samples using laser-induced breakdown spectroscopy (LIBS) was developed and applied to the analysis of bulk soil samples for ...discrimination between specimens. The use of a 266 nm laser for LIBS analysis is reported for the first time in forensic soil analysis. Optimization of the LIBS method is discussed, and the results compared favorably to a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) method previously developed. Precision for both methods was <10% for most elements. LIBS limits of detection were <33 ppm and bias <40% for most elements. In a proof of principle study, the LIBS method successfully discriminated samples from two different sites in Dade County, FL. Analysis of variance, Tukey’s post hoc test and Student’s
t
test resulted in 100% discrimination with no type I or type II errors. Principal components analysis (PCA) resulted in clear groupings of the two sites. A correct classification rate of 99.4% was obtained with linear discriminant analysis using leave-one-out validation. Similar results were obtained when the same samples were analyzed by LA-ICP-MS, showing that LIBS can provide similar information to LA-ICP-MS. In a forensic sampling/spatial heterogeneity study, the variation between sites, between sub-plots, between samples and within samples was examined on three similar Dade sites. The closer the sampling locations, the closer the grouping on a PCA plot and the higher the misclassification rate. These results underscore the importance of careful sampling for geographic site characterization.
Elemental analysis of soil is a useful application of both laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and laser-induced breakdown spectroscopy (LIBS) in geological, ...agricultural, environmental, archeological, planetary, and forensic sciences. In forensic science, the question to be answered is often whether soil specimens found on objects (e.g., shoes, tires, or tools) originated from the crime scene or other location of interest. Elemental analysis of the soil from the object and the locations of interest results in a characteristic elemental profile of each specimen, consisting of the amount of each element present. Because multiple elements are measured, multivariate statistics can be used to compare the elemental profiles in order to determine whether the specimen from the object is similar to one of the locations of interest. Previous work involved milling and pressing 0.5 g of soil into pellets before analysis using LA-ICP-MS and LIBS. However, forensic examiners prefer techniques that require smaller samples, are less time consuming, and are less destructive, allowing for future analysis by other techniques. An alternative sample introduction method was developed to meet these needs while still providing quantitative results suitable for multivariate comparisons. The tape-mounting method involved deposition of a thin layer of soil onto double-sided adhesive tape. A comparison of tape-mounting and pellet method performance is reported for both LA-ICP-MS and LIBS. Calibration standards and reference materials, prepared using the tape method, were analyzed by LA-ICP-MS and LIBS. As with the pellet method, linear calibration curves were achieved with the tape method, as well as good precision and low bias. Soil specimens from Miami–Dade County were prepared by both the pellet and tape methods and analyzed by LA-ICP-MS and LIBS. Principal components analysis and linear discriminant analysis were applied to the multivariate data. Results from both the tape method and the pellet method were nearly identical, with clear groupings and correct classification rates of >94%.
We report a precision measurement of the parity-violating asymmetry APV in the elastic scattering of longitudinally polarized electrons from 208Pb. We measure APV= 550 ± 16 (stat) ±8 (syst) parts per ...billion, leading to an extraction of the neutral weak form factor FW(Q2= 0.00616 GeV2) = 0.368 ± 0.013. Combined with our previous measurement, the extracted neutron skin thickness is Rn-Rp= 0.283 ± 0.071 fm. The result also yields the first significant direct measurement of the interior weak density of 208Pb: ρ$^0_W$ = -0.0796 ± 0.0036(exp) ± 0.0013(theo) fm-3 leading to the interior baryon density ρ$^0_b$ = 0.1480 ± 0.0036(exp) ± 0.0013(theo) fm-3. Finally, the measurement accurately constrains the density dependence of the symmetry energy of nuclear matter near saturation density, with implications for the size and composition of neutron stars.
IMPORTANCE: Type 2 diabetes is associated with increased cardiovascular (CV) risk. Prior trials have demonstrated CV safety of 3 dipeptidyl peptidase 4 (DPP-4) inhibitors but have included limited ...numbers of patients with high CV risk and chronic kidney disease. OBJECTIVE: To evaluate the effect of linagliptin, a selective DPP-4 inhibitor, on CV outcomes and kidney outcomes in patients with type 2 diabetes at high risk of CV and kidney events. DESIGN, SETTING, AND PARTICIPANTS: Randomized, placebo-controlled, multicenter noninferiority trial conducted from August 2013 to August 2016 at 605 clinic sites in 27 countries among adults with type 2 diabetes, hemoglobin A1c of 6.5% to 10.0%, high CV risk (history of vascular disease and urine-albumin creatinine ratio UACR >200 mg/g), and high renal risk (reduced eGFR and micro- or macroalbuminuria). Participants with end-stage renal disease (ESRD) were excluded. Final follow-up occurred on January 18, 2018. INTERVENTIONS: Patients were randomized to receive linagliptin, 5 mg once daily (n = 3494), or placebo once daily (n = 3485) added to usual care. Other glucose-lowering medications or insulin could be added based on clinical need and local clinical guidelines. MAIN OUTCOMES AND MEASURES: Primary outcome was time to first occurrence of the composite of CV death, nonfatal myocardial infarction, or nonfatal stroke. Criteria for noninferiority of linagliptin vs placebo was defined by the upper limit of the 2-sided 95% CI for the hazard ratio (HR) of linagliptin relative to placebo being less than 1.3. Secondary outcome was time to first occurrence of adjudicated death due to renal failure, ESRD, or sustained 40% or higher decrease in eGFR from baseline. RESULTS: Of 6991 enrollees, 6979 (mean age, 65.9 years; eGFR, 54.6 mL/min/1.73 m2; 80.1% with UACR >30 mg/g) received at least 1 dose of study medication and 98.7% completed the study. During a median follow-up of 2.2 years, the primary outcome occurred in 434 of 3494 (12.4%) and 420 of 3485 (12.1%) in the linagliptin and placebo groups, respectively, (absolute incidence rate difference, 0.13 95% CI, −0.63 to 0.90 per 100 person-years) (HR, 1.02; 95% CI, 0.89-1.17; P < .001 for noninferiority). The kidney outcome occurred in 327 of 3494 (9.4%) and 306 of 3485 (8.8%), respectively (absolute incidence rate difference, 0.22 95% CI, −0.52 to 0.97 per 100 person-years) (HR, 1.04; 95% CI, 0.89-1.22; P = .62). Adverse events occurred in 2697 (77.2%) and 2723 (78.1%) patients in the linagliptin and placebo groups; 1036 (29.7%) and 1024 (29.4%) had 1 or more episodes of hypoglycemia; and there were 9 (0.3%) vs 5 (0.1%) events of adjudication-confirmed acute pancreatitis. CONCLUSIONS AND RELEVANCE: Among adults with type 2 diabetes and high CV and renal risk, linagliptin added to usual care compared with placebo added to usual care resulted in a noninferior risk of a composite CV outcome over a median 2.2 years. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01897532
Rapid (<2 min) and quantitative genotyping for single nucleotide polymorphisms (SNPs) associated with spinal muscular atrophy was done using a reusable (approximately 80 cycles of application) ...fibre‐optic biosensor over a clinically relevant range (0–4 gene copies). Sensors were functionalized with oligonucleotide probes immobilized at high density (∼7 pmol/cm2) to impart enhanced selectivity for SNP discrimination and used in a total internal reflection fluorescence detection motif to detect 202 bp PCR amplicons from patient samples. Real‐time detection may be done over a range of ionic strength conditions (0.1–1.0 M) without stringency rinsing to remove non‐selectively bound materials and without loss of selectivity, permitting a means for facile sample preparation. By using the time‐derivative of fluorescence intensity as the analytical parameter, linearity of response may be maintained while allowing for significant reductions in analysis time (10–100‐fold), permitting for the completion of measurements in under 1 min.
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