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The growing number of studies and interest in two-dimensional (2D) materials has not yet resulted in a wide range of material applications. This is a result of difficulties in getting the properties, which are often determined through numerical experiments or through first-principles predictions, both of which require lots of time and resources. Here we provide a general machine learning (ML) model that works incredibly well as a predictor for a variety of electronic and structural properties such as band gap, fermi level, work function, total energy and area of unit cell for a wide range of 2D materials derived from the Computational 2D Materials Database (C2DB). Our predicted model for classification of samples works extraordinarily well and gives an accuracy of around 99 %. We are able to successfully decrease the number of studied features by employing a strict permutation-based feature selection method along with the sure independence screening and sparsifying operator (SISSO), which further supports the design recommendations for the identification of novel 2D materials with the desired properties. 相似文献
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Zirconium reacts with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in the pH range 3.8-5.8 to form a red chelate that is soluble in methanol-water mixtures. The absorbance of the 1:3 complex obeys Beer's law over the zirconium concentration range 0.02-0.44 mug/ml and has a molar absorptivity of 1.54 x 10(5) 1.mole(-1). cm(-1) at 585 nm. The formation constant is log beta(3) = 16.15. Of 59 species studied, only EDTA, Ga, In, Ti, Hf and V(V) interfere seriously. 相似文献
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Eshwar Jagerdeo Mohamed Abdel-Rehim 《Journal of the American Society for Mass Spectrometry》2009,20(5):891-899
Microextraction by packed sorbent (MEPS) has been evaluated for fast screening of drugs of abuse with mass spectrometric detection.
In this study, C8 (octyl-silica, useful for nonpolar to moderately polar compounds), ENV+ (hydroxylated polystyrene-divinylbenzene copolymer, for extraction of aliphatic and aromatic polar compounds), Oasis MCX
(sulfonic-poly(divinylbenzene-co-N-polyvinyl-pyrrolidone) copolymer), and Clean Screen DAU (mixed mode, ion exchanger for
acidic and basic compounds) were used as sorbents for the MEPS. The focus was on fast extraction and preconcentration of the
drugs with rapid analysis using a time-of-flight (TOF) mass spectrometer as the detector with direct analysis in a real-time
(DART) source. The combination of an analysis time of less than 1 min and accurate mass of the first monoisotopic peak of
the analyte and the relative abundances of the peaks in the isotopic clusters provided reliable information for identification.
Furthermore, the study sought to demonstrate that it is possible to quantify the analyte of interest using a DART source when
an internal standard is used. Of all the sorbents used in the study, Clean Screen DAU performed best for extraction of the
analytes from urine. Using Clean Screen DAU to extract spiked samples containing the drugs, linearity was demonstrated for
ecgonine methyl ester, benzoylecgonine, cocaine, and cocaethylene with average ranges of: 65–910, 75–1100, 95–1200, and 75–1100
ng/mL (n = 5), respectively. The limits of detection (LOD) for ecgonine methyl ester, benzoylecgonine, cocaine, and cocaethylene were
22. 9 ng/mL, 23. 7 ng/mL, 4. 0 ng/mL, and 9.8 ng/mL respectively, using a signal-to-noise ratio of 3:1. 相似文献
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Eshwar Jagerdeo Jason E. Schaff Madeline A. Montgomery Marc A. LeBeau 《Rapid communications in mass spectrometry : RCM》2009,23(17):2697-2705
Marijuana is one of the most commonly abused illicit substances in the USA, making cannabinoids important to detect in clinical and forensic toxicology laboratories. Historically, cannabinoids in biological fluids have been derivatized and analyzed by gas chromatography/mass spectrometry (GC/MS). There has been a gradual shift in many laboratories towards liquid chromatography/mass spectrometry (LC/MS) for this analysis due to its improved sensitivity and reduced sample preparation compared with GC/MS procedures. This paper reports a validated method for the analysis of Δ9‐tetrahydrocannabinol (THC) and its two main metabolites, 11‐nor‐9‐carboxy‐Δ9‐tetrahydrocannabinol (THC‐COOH) and 11‐hydroxy‐Δ9‐tetrahydrocannabinol (THC‐OH), in whole blood samples. The method has also been validated for cannabinol (CBD) and cannabidiol (CDN), two cannabinoids that were shown not to interfere with the method. This method has been successfully applied to samples both from living people and from deceased individuals obtained during autopsy. This method utilizes online solid‐phase extraction (SPE) with LC/MS. Pretreatment of samples involves protein precipitation, sample concentration, ultracentrifugation, and reconstitution. The online SPE procedure was developed using Hysphere C8‐EC sorbent. A chromatographic gradient with an Xterra MS C18 column was used for the separation. Four multiple‐reaction monitoring (MRM) transitions were monitored for each analyte and internal standard. Linearity generally fell between 2 and 200 ng/mL. The limits of detection (LODs) ranged from 0.5 to 3 ng/mL and the limits of quantitation (LOQs) ranged from 2 to 8 ng/mL. The bias and imprecision were determined using a simple analysis of variance (ANOVA: single factor). The results demonstrate bias as <7%, and imprecision as <9%, for all components at each quantity control level. Published in 2009 by John Wiley & Sons, Ltd. 相似文献
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Ioanna T. Nakou Dr. Matthew Jenner Dr. Yousef Dashti Dr. Isolda Romero-Canelón Dr. Joleen Masschelein Prof. Eshwar Mahenthiralingam Prof. Gregory L. Challis 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(51):23345-23353
A gene cluster encoding a cryptic trans-acyl transferase polyketide synthase (PKS) was identified in the genomes of Burkholderia gladioli BCC0238 and BCC1622, both isolated from the lungs of cystic fibrosis patients. Bioinfomatics analyses indicated the PKS assembles a novel member of the glutarimide class of antibiotics, hitherto only isolated from Streptomyces species. Screening of a range of growth parameters led to the identification of gladiostatin, the metabolic product of the PKS. NMR spectroscopic analysis revealed that gladiostatin, which has promising activity against several human cancer cell lines and inhibits tumor cell migration, contains an unusual 2-acyl-4-hydroxy-3-methylbutenolide in addition to the glutarimide pharmacophore. An AfsA-like domain at the C-terminus of the PKS was shown to catalyze condensation of 3-ketothioesters with dihydroxyacetone phosphate, thus indicating it plays a key role in polyketide chain release and butenolide formation. 相似文献
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Eshwar Jagerdeo Madeline A. Montgomery Roman P. Karas Martin Sibum 《Analytical and bioanalytical chemistry》2010,398(1):329-338
Marijuana is one of the most commonly used illicit substances. The high usage of this substance results in it being commonly
encountered in clinical samples throughout the USA and Europe. Due to its wide availability and use, marijuana is also commonly
encountered in forensic toxicology laboratories. The proposed method utilized an automated solid phase extraction (SPE) coupled
to liquid chromatography/mass spectrometry (LC/MS). The automated SPE procedure was developed using Hysphere C8-EC sorbent,
and the high performance liquid chromatography (HPLC) separation was performed using an Xterra MS C18 column with a total runtime of 10 min. The standard curves linearity generally fell between 6 and 500 ng/mL. The limits of
detection ranged from 2 to 4 ng/mL, and the limits of quantitation ranged from 8 to 12 ng/mL. The bias and imprecision were
determined using a simple analysis of variance (single factor). The results demonstrate bias as <11% and percent imprecision
as <12% for all components at four quality control levels. This method has been in use for over 2 years and has been applied
to numerous forensic samples. When compared to other published methods, it exceeds others in its simplicity and speed of analysis.
This method takes advantage of robotics and automation for a total analysis time of 10 min, including sample preparation,
separation, and detection. 相似文献
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Mahenthiralingam E Song L Sass A White J Wilmot C Marchbank A Boaisha O Paine J Knight D Challis GL 《Chemistry & biology》2011,18(5):665-677
Gram-negative Burkholderia cepacia complex (Bcc) isolates were screened for antimicrobial activity against cystic fibrosis microbial pathogens, and the ability of B.?ambifaria to inhibit B.?multivorans was identified. The activity was mapped to a cluster of cryptic, quorum-sensing-regulated modular polyketide synthase (PKS) genes. Enacyloxin IIa and its stereoisomer designated iso-enacyloxin IIa were identified as metabolic products of the gene cluster, which encoded an unusual hybrid modular PKS consisting of multiple proteins with sequence similarity to cis-acyltransferase (cis-AT) PKSs and a single protein with sequence similarity to trans-AT PKSs. The discovery of the potent activity of enacyloxins against drug-resistant bacteria and the gene cluster that directs their production provides an opportunity for engineered biosynthesis of innovative enacyloxin derivatives and highlights the potential of Bcc bacteria as an underexploited resource for antibiotic discovery. 相似文献
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Summary Manganese forms a red chelate with 4-(2-thiazolylazo)-resorcinol at pH 8.8 (borate buffer), and absorbance is measured after 30 s, at 540 nm in the presence of 20%tert-butyl alcohol (by volume). The 12 complex obeys Beer's law for manganese concentration of 0.04–1.4g per ml, has molar absorptivity 4.176 x 104 and Sandell sensitivity 0.0013g cm–2. The formation constant (logK) is found to be 9.32, and relative standard deviation ±0.22%. Of the 48 ions studied for interference, only Co(II), Zn(II), Cd(II), Pb(II) and EDTA2– are found to interfere. This method has been applied for the determination of manganese content in alloy steels.
Spektrophotometrische Bestimmung von Mangan(II) mit 4-(2-Thiazolylazo)-resorcin
Zusammenfassung Mangan bildet bei pH 8,8 (Boratpuffer) mit 4-(2-Thiazolylazo)-resorcin ein rotes Chelat, dessen Absorbanz nach 30 sec bei 540 nm in Gegenwart von 20% tert. Butylalkohol gemessen wird. Dieser 12-Komplex entspricht bei einer Mangan-Konzentration von 0,04–1,4g/ml dem Beerschen Gesetz; seine molare Absorption beträgt 4,176 x 104, die Empfindlichkeit nach Sandell 0,0013g·cm–2. Die Bildungskonstante (log K) beträgt 9,32, die rel. Standardabweichung ±0,22%. Unter 48 untersuchten Ionen erwiesen sich nur Co(II), Zn(II), Cd(II), Pb(II) und EDTA als störend.-Das Verfahren wurde zur Bestimmung des Mangangehaltes in Stahl verwendet.相似文献