bluuebunny/crossref_metadata_2025_split huggingface dataset:
On Some Aspects of Variable Selection for Partial Least Squares Regression Models
Authors: Roy Partha Pratim , Roy Kunal 
Published: July 2007

AbstractThis paper tries to explore the optimum variable selection strategy for Partial Least Squares (PLS) regression using a model dataset of cytoprotection data. The compounds of the dataset were classified using K‐means clustering technique applied on standardized descriptor matrix and ten combinations of training and test sets were generated based on the obtained clusters. For a particular training set, PLS models were developed with a number of components optimized by leave‐one‐out Q2 and then the developed models were validated (externally) using the test set compounds. For each set, PLS model was initially constructed using all descriptors (variables). The variables having least standardized values of regression coefficients were deleted and the next model was developed with a reduced set of variables. These steps were performed several times until further reduction in number of variables did not improve Q2 value. In each case, statistical parameters like predictive R2 (R2pred), squared correlation coefficient between observed and predicted values with (r2) and without ($\rm{ r_0^{\rm{2}} }$) intercept and Root Mean Square Error of Prediction (RMSEP) were calculated from the test set compounds. In case of all ten sets, Q2 values steadily increase on deletion of variables while R2pred values do not show any specific trend. In no case, the highest Q2 and highest R2pred appear in the same trial, i.e., with the same combinations of variables. This suggests that from the viewpoint of external predictability, choice of variables for PLS based on Q2 value may not be optimum. Moreover, a clear separation of r2 and r02 curves in some sets suggests that such models may not be truly predictive in spite of acceptable R2pred values. Another observation is that coefficient of determination R2 for the training set is more immune to changes on deletion of variables than the validation parameters like Q2 and R2pred. Finally, a new parameter rm2 has been suggested to indicate external predictability of QSAR models.
Towards a reliable molecular mass determination of intact glycoproteins by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Giménez Estela , Benavente Fernando , Barbosa José , Sanz‐Nebot Victoria 
Published: July 2007

AbstractDifferent matrices and sample‐matrix preparation procedures have been tested in order to study their influence on the matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectra of intact glycoproteins, which present different degrees of glycosylation (human transferrin; bovine fetuin; bovine α1‐acid‐glycoprotein; recombinant human erythropoietin; and the novel erythropoiesis stimulating protein). Using sinapinic acid (SA) and the fast evaporation method, the studied glycoproteins became susceptible to fragmentation at any laser intensity, suggesting that this ‘hot’ matrix is unsuitable for a reliable molecular mass determination of glycosylated compounds. In contrast, 2,5‐dihydroxybenzoic acid (DHB) and 6‐aza‐2‐thiothymine (ATT), with an adequate sample‐matrix preparation, provided improved results. Samples containing DHB after crystallization by vacuum drying demonstrated the best performance because the labile functional groups from the glycoforms were apparently fragmented to a lower extent. The average molecular masses obtained using this methodology were in all cases a better estimation than those values reported in the literature. The results were reproducible, and sensitivity was similar to that obtained with SA and the fast evaporation method. These excellent results suggest that this MALDI‐TOF‐MS methodology could be useful for an improved determination of the average molecular mass values of microheterogeneous compounds such as glycoproteins, glycosylated compounds or, in general, molecular mass values of molecules with similar labile functional groups. Copyright © 2007 John Wiley & Sons, Ltd.
Post‐source decay of alkylated and functionalized polycyclic aromatic compounds
Authors: Frache Gilles , Krier Gabriel , Vernex‐Loset Lionel , Muller Jean‐François , Manuelli Pascal 
Published: July 2007

AbstractPost‐source decay (PSD) is a valuable tool for providing structural information from large molecules by time‐of‐flight mass spectrometry (TOFMS). We used PSD to obtain this type of data from small molecules in the laser desorption/ionization (LDI) study of diesel engine exhaust particles. As the original nitrogen laser (λ = 337 nm, E = 3.5 eV/photon) of our TOF mass spectrometer does not yield sufficient energy to ionize polycyclic aromatic hydrocarbons (PAHs), a second laser with a shorter wavelength has been coupled to the instrument. The fourth harmonic of a Nd:YAG laser (λ = 266 nm, 4.6 eV/photon) has been chosen to achieve two‐photon single‐step desorption/ionization of PAHs. The PSD fragmentation of functionalized, alkylated and sulfur PAHs is discussed. Diesel engine exhaust particles are also studied as an example of a real complex sample. This technique is presented herein as a way to identify small molecules in environmental samples. Information provided by LDI‐PSD‐TOFMS can be a way to distinguish pollutants with very close molecular weights even if the resolving power of a TOF mass spectrometer is not sufficient. Copyright © 2007 John Wiley & Sons, Ltd.
The application of ultra‐performance liquid chromatography/tandem mass spectrometry to the detection and quantitation of apolipoproteins in human serum
Authors: Kay Richard G. , Gregory Barbara , Grace Philip B. , Pleasance Steve 
Published: July 2007

AbstractThe detection and quantitation of apolipoproteins, important markers for coronary heart disease, in serum by liquid chromatography/tandem mass spectrometry (LC/MS/MS) using multiple reaction monitoring (MRM) is reported. A tryptic digest of depleted human serum was analysed by nanoflow LC/MS/MS at a flow rate of 300 nL/min and several apolipoproteins (Apo), including Apo A1, A2, A4, C1, C2, C3, D, F and M, were successfully identified. The analysis of the same depleted serum digest by ultra‐performance (UP)LC/MS/MS operating at 700 µL/min resulted in comparable sensitivity and selectivity to the nanoflow method, but with a dramatic (∼20‐fold) reduction in run time. The potential of UPLC/MS/MS for the rapid quantitation of proteins in biological matrices by representative tryptic peptides was further investigated using Apo A1 and its corresponding stable isotopically labelled tryptic AQUA peptide (DYVSQFEGSALGK). A set of serum‐based Apo A1 calibrators from a clinical analyser kit were digested without depletion following the addition of the AQUA peptide and analysed using UPLC/MS/MS. A linear calibration curve was generated from peak area ratios to the labelled peptide with a coefficient of correlation of 0.9989. Standard curves were also generated for other apolipoproteins together with Apo B100, Apo E, lecithin cholesterol acyltransferase and albumin, which were also detected in the standards. The concentration of Apo A1 in five fresh undepleted human serum samples and a quality control (QC) sample were determined using both the UPLC/MS/MS method and a clinical analyser. Results were comparable and the quantitative study, involving 80 injections which took hours rather than days to complete, demonstrates the high‐throughput potential of UPLC/MS/MS to quantify multiple serum proteins without the need for antibodies, and thus provide an alternative to the use of clinical analysers for serum protein biomarkers. Copyright © 2007 John Wiley & Sons, Ltd.
Speciation of M+3‐hydroxypyrone chelation complexes by electrospray ionization ion trap and Fourier transform ion cyclotron resonance mass spectrometry
Authors: Stenson Alexandra C. , Cioffi Eugene A. 
Published: July 2007

AbstractKojic acid (5‐hydroxy‐2‐hydroxymethyl‐4‐pyrone) is known to have a high affinity for transition metals, and it and its derivatized cogeners are used both analytically and clinically. The interactions between kojic acid (KA) and eleven +3 metals (Al+3, As+3, Cr+3, Ga+3, Fe+3, In+3, Yb+3, Y+3, Gd+3, Nd+3, La+3) were examined by electrospray ionization mass spectrometry (ESI‐MS) using an ion trap in an aqueous medium. For a subset of five ions, Fourier transform ion cyclotron resonance (FTICR)‐MS was conducted to provide accurate mass confirmation of peak assignments for metals having clustering of abundant isotopes. KA readily formed complexes with all the metal ions tested. The most common complexes observed were ML3H+ and M2L5. Different behavior was seen for small and large ionic radius ions, with a relative cut‐off between In+3 (∼80 pm) and Yb+3 (∼87 pm); a striking trend in % collision energy vs. cluster complexity was revealed. The KA‐Cr+3complex shows a high affinity for H2O molecules in the gas phase, whilst In+3 shows a preference for dimetal complexes and Y+3 a deviant behavior when complexed to two neutrals. Copyright © 2007 John Wiley & Sons, Ltd.
Molecular depth‐profiling of polycarbonate with low‐energy Cs+ ions
Authors: Mine Nicolas , Douhard Bastien , Brison Jeremy , Houssiau Laurent 
Published: July 2007

AbstractIn this work, we explored the possibility of performing molecular depth‐profiling by using very low‐energy (about 200 eV) monoatomic Cs+ ions. We show, for the first time, that this simple approach is successful on polymer layers of polycarbonate (PC). Under 200 eV Cs+ irradiation of PC, a fast decrease of all characteristic negatively charged molecular ion signals is first observed but, rather surprisingly, these signals reach a minimum before rising again. A steady state is reached at which time most specific PC fragments are detected, some with even higher signal intensity (e.g. C6H5O−) than before irradiation. It is believed that the implanted Cs plays a major role in enhancing the negative ionisation of molecular fragments, leading to their easy detection for all the profile, although some material degradation obviously occurs. In the positive ion mode, all molecular fragments of the polymer disappear very rapidly, but clusters combining two Cs atoms and one molecular fragment (e.g. Cs2C6H5O+) are detected during the profile, proving that some molecular identification remains possible. In conclusion, this work presents a simple approach to molecular depth‐profiling, complementary to cluster ion beam sputtering. Copyright © 2007 John Wiley & Sons, Ltd.
Modelling patterns of agreement for nominal scales
Authors: Roberts Chris 
Published: July 2007

AbstractThe measurement of agreement of repeat rating is the usual method of assessing the reliability of categorical scales. Measurement of agreement is also important in genetic twin studies based on categorical scales. One of the most commonly used methods of analysis for both types of study is the kappa coefficient. For scales with more than two categories, one approach is to use a single summary kappa coefficient. While this may be sufficient for many studies, in some instances investigation of heterogeneity in the pattern of agreement may give additional insights as there may be greater agreement for some pairs of categories than for others. In this paper, kappa‐type coefficients are used to model heterogeneity in the pattern of agreement. Constraints are added to the heterogeneous model to obtain simplified models. Procedures for estimation, confidence intervals, and inference for these coefficients are described for the case of two ratings per subject for a single sample and for the comparison of two independent samples. Formulae for sample size and power calculation are derived using the non‐central chi‐squared distribution. Two simulation studies are carried out to check the empirical test size and power. Methods are illustrated by two examples involving nominal scales with three categories. Copyright © 2007 John Wiley & Sons, Ltd.
Black feminist thought and cultural contracts: Understanding the intersection and negotiation of racial, gendered, and professional identities in the academy
Authors: Harris Tina M. 
Published: July 2007

AbstractThis chapter explores identity negotiation by women of color in academe at a predominantly white institution. The author discusses use of the title doctor as a form of address to manage interactions with graduate students in the college classroom, and the difficulties associated with negotiating and balancing these diverse and complex identities in an oppressive context.
Analysis of cationic and amphoteric surfactants I. Determination of their homolog distributions by gas chromatography on the basis of the Hofmann degradation
Authors: Takano S. , Takasaki C. , Kunihiro K. , Yamanaka M. 
Published: July 2007

AbstractA method (DMF‐Methylate method) has been described for the homolog analysis of cationic and amphoteric surfactants having a quaternary am‐monium group. The homolog distribution of cationic and amphoteric surfactants obtained by the DMF‐Methylate method closely agrees with that of the original alkyldimethylamines used. Therefore, the DMF‐Methylate method should be applicable to the homolog analysis of these surfactants. This method also offers qualitative information for the identifica‐tion of these surfactants, since the ratio of the α‐olefin to the alkyldimethylamine varies with each sur‐factant. On the basis of the analysis of the elimina‐tion products, it was confirmed that the main degra‐dation process was the elimination of a β‐hydrogen atom. This mechanism is different from that of the pyrolysis gas chromatography, which will be dis‐cussed elsewhere (S. Takano, M. Kuzukawa, and M. Yamanaka, in preparation).
Transfer hydrogenation and transfer hydrogenolysis. X. Selective hydrogenation of methyl linoleate by indoline and isopropyl alcohol
Authors: Nishiguchi T. , Tagawa T. , Imai H. , Fukuzumi K. 
Published: July 2007

AbstractThe selective hydrogenation of methyl linoleate was studied using indoline and isopropyl alcohol as hydrogen sources. Many transition metal compounds and metallic palladium were examined as catalysts. High selectivity to monoenes and little formation oftrans isomers were realized under mild conditions in some reaction systems. For example, the system in which isopropyl alcohol and RuCl2(PPh3)3 were used as hydrogen donor and catalyst was excellent. Also in the hydrogen transfer from indoline to the linoleate catalyzed by PdCl2 and (NH4)2PdCl4, high selec‐tivity was realized. In the RuCl2(PPh3)3‐isopropyl alcohol, (NH4)2PdCl4‐indoline and PdCl2‐indoline system, methylcis‐ trans conjugated octadecadienoate was reduced rapidly with complete selectivity, where‐as the same hydrogen transfer systems resulted in little if any reaction with methyl oleate. High selec‐tivity in the reduction of linoleate is presumed to be realized through prior conjugation of the substrate.
Studies on methanolysis of triglycerides on thin layer chromatoplate
Authors: Saha S. , Dutta J. 
Published: July 2007

AbstractMethanolysis of triglycerides on thin layer chro‐matography plate, for the preparation of correspond‐ing fatty acid methyl esters suitable for gas liquid chromatography analysis, has been studied with synthetic mixtures of pure tricaprylin, trilaurin, tri‐palmitin, and triolein. The long chain saturated glyc‐eride, tripalmitin, has been found to be least suscep‐tible to methanolysis. Plate temperature of 65 C and KOMe‐methanol reagent concentration of 1.0 N have been found to be optimal for samples containing large amount of trisaturated glyceride like tripalmitin without appreciable loss in short chain components by evaporation. For fats containing lower proportions of trisaturated glyceride like vegetable oils, a lower concentration, i.e., 0.5 N of the reagent can be used at the above temperature. Addition of lipid solvent like benzene in the reagent has little effect on the conversion. Long chain triglycerides containing one or more double bonds in the molecule respond more to this reaction than do trisaturated glycerides of the same carbon number. Fatty acid compositions of cottonseed and peanut oil triglycerides obtained by the GLC analysis of the methyl esters prepared by the present method and that of Luddy et al. [JAOCS 45:549 (1968)] have been found to agree well.
Urethane foams from animal fats: X. urethane polyols from epoxidized tallow, trimethylolpropane, and propylene oxide1
Authors: Bilyk A. , Saggese E. J. , Monroe H. A. , Zubillaga M. P. 
Published: July 2007

AbstractA convenient three‐stage reaction has been devel‐oped for the preparation of polyols from epoxidized tallow (ET), trimethylolpropane (TMP), and propyl‐ene oxide (PO), without the previously required water washing step. ET is first heated with excess TMP under catalysis by BF3, causing rapid ring open‐ing of the oxirane function. In the second stage, KOH catalyzes ester interchange of TMP with the triglyc‐eride. Finally, PO is caused to react with free TMP and with other available hydroxylic components, to produce a homogeneous mixture of polyols. The polyols, all liquid at room temperature, were adjusted to equivalent weights of 100 and 120 with added triisopropanolamine and reacted with a polymeric isocyanate in the presence of a blowing agent to give low‐density rigid foams. Densities ranged from 1.6 to 1.8 lb/ft3 and compressive strengths from 21 to 30psi.
The Association of Official Analytical Chemists (AOAC)
Authors: Baur Fred J. , Ensminger Luther G. 
Published: July 2007

AbstractThe analytical methods adopted by the AOAC (Association of Official Analytical Chemists) are used by government agencies concerned with the analysis of fertilizers, foods, feeds, pesticides, drugs, cos‐metics, hazardous substances, and other materials related to agriculture, health and welfare, and the environment. AOAC methods are also used by indus‐try to check compliance of their products. The AOCS and AOAC have cooperated in the past in achieving common methodology for fatty acids, hydrocarbons and mineral oils, and monoglycerides. Present cooper‐ative effort centers primarily in the mycotoxins area. The various methods adopted by the AOAC appear in the book, Official Methods of Analysis, which is published every five years with annual supplements. The 12th edition was published in January 1975. Industrial scientists cannot be full or active members but they can serve as associate members of the AOAC. Active membership is limited to government scientists. Industry can and should, however, partici‐pate in the activities of the AOAC‐particularly in the key task of developing, testing, and validating methods of analysis. Uniform methodology should be the goal of all societies. The purpose of this paper is twofold: (a) to explain the structure, functions, and goals of the AOAC; and (b) to inform potential industrial representatives how they may participate in the Association’s activities.
Making use of “outside” research and analysis
Authors: Coon Francis B. 
Published: July 2007

AbstractThe services offered by commercial research and analysis laboratories are discussed with emphasis on what a user may expect. Suggestions are given on what to look for in an “outside” laboratory, and what should be done in cases of dissatisfaction or uncertainty. Problems a service laboratory may have with users and ways to resolve such problems are given. Typical examples illustrate the usefulness of “outside” research and analysis.
Requirements of a good analytical chemistry research paper
Authors: Petruzzi Josephine M. 
Published: July 2007

AbstractA good analytical chemistry research paper may be defined as one that passes the critical review of one’s peers for publication in a recognized reviewed jour‐nal. Factors to consider in publishing an analytical paper include careful selection of the right journal, clear concise presentation that emphasizes the re‐search contribution and its significance to the field, and careful revision if called for to account for the reviewers’ and editors’ criticisms. Rather special requirements apply to methods papers as opposed to other types of analytical papers. Data should be included to establish the accuracy and precision of the method by the use of standard reference mate‐rials, standard addition studies, interference studies, and comparisons with established methods. Day‐to‐day and run precision studies of the proposed method in a real setting help validate the method. Common problems with analytical papers are discussed. Specific suggestions are given for improving the likeli‐hood of publication. Data are given on the ultimate disposition of manuscripts submitted toAnalytical Chemistry. Reasons for rejection of papers submitted to the journal are summarized.
Isolation of isomeric hydroperoxides from the peanut lipoxygenase‐ linoleic acid reaction
Authors: Pattee Harold E. , Singleton John A. 
Published: July 2007

AbstractHydroperoxides were isolated from the peanut lipoxygenase‐linoleic acid reaction mixture and were separated as their methyl esters by high performance liquid chromatography. Mass spectrometry and infra‐red analysis indicated the isolated hydroperoxides to be 13‐hydroperoxy‐cis‐9,trans‐ 11‐octadecadienoic acid; 13‐hydroperoxy‐trans‐ 9,trans‐ 11‐octadeca‐dienoic acid; and 9‐hydroperoxy‐trans‐l0,trans‐ 12‐ octadecadienoic acid. The percentages of the hydro‐peroxides in the reaction mixture were 72.8%, 3.6%, and 23.6% under the conditions used. 1 Paper No. 4973 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, NC 27607.
Detergent raw material trends in western europe
Authors: Carlotti R. 
Published: July 2007

AbstractHousehold detergent sales during 1975 in Western Europe totaled more than $4 billion and are expected to continue to grow at approximately 3 to 4 percent annual increments during next decade. There is a trend toward more uniform formulations, but factors affecting future market growth include washing practices and conditions that vary from nation to nation. Demand for surfactants is dominated by LAS, accounting for 80 percent of total synthetic actives used in laundry detergent, with increasing use of linear alcohol ethoxylates. Environmental considera‐tions, cost, and energy savings are factors in a trend toward less use of phosphate, compensated by greater use of LAS or ethoxylate or both to maintain clean‐ing performance. New investment in detergent raw materials is more likely for detergent alcohols and alpha olefin derivatives, and not in LAB.
Industrial hydrogenation of rapeseed oil with nickel catalyst
Authors: Ahmad Iqbal , Ali Amjad 
Published: July 2007

AbstractRefined and deodorized rapeseed oil was hydrogenated using Girdler nickel catalyst at a starting temperature of 140 C and at 25 and 30 psig hydrogen gas pressures. The studies revealed that the hydrogenation was more effective, as determined by rate of decrease in iodine value (Wi js) and increase in the melting point, at 25 psig than at 30 psig. The rate of effectiveness was, however, not significant. The rate of hydrogenation was compared to cottonseed oil subjected to hydrogenation under identical conditions. Cottonseed oil showed a better, though insignificant, rate of increase in melting point per unit increase in time.