bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement of clay surface areas by polyvinylpyrrolidone (PVP) sorption and its use for quantifying illite and smectite abundance
Authors: Blum A. E. , Eberl D. D. 
Published: September 2004

AbstractA new method has been developed for quantifying smectite abundance by sorbing polyvinylpyrrolidone (PVP) on smectite particles dispersed in aqueous solution. The sorption density of PVP-55K on a wide range of smectites, illites and kaolinites is ∼0.99 mg/m2, which corresponds to ∼0.72 g of PVP-55K per gram of montmorillonite. Polyvinylpyrrolidone sorption on smectites is independent of layer charge and solution pH. PVP sorption on SiO2, Fe2O3and ZnO normalized to the BET surface area is similar to the sorption densities on smectites. γ-Al2O3, amorphous Al(OH)3and gibbsite have no PVP sorption over a wide range of pH, and sorption of PVP by organics is minimal. The insensitivity of PVP sorption densities to mineral layer charge, solution pH and mineral surface charge indicates that PVP sorption is not localized at charged sites, but is controlled by more broadly distributed sorption mechanisms such as Van der Waals’ interactions and/or hydrogen bonding. Smectites have very large surface areas when dispersed as single unit-cell-thick particles (∼725 m2/g) and usually dominate the total surface areas of natural samples in which smectites are present. In this case, smectite abundance is directly proportional to PVP sorption. In some cases, however, the accurate quantification of smectite abundance by PVP sorption may require minor corrections for PVP uptake by other phases, principally illite and kaolinite. Quantitative XRD can be combined with PVP uptake measurements to uniquely determine the smectite concentration in such samples.
Na biotite and intermediate Na-K biotite in schists from the Betic Cordilleras (Spain)
Authors: Ruiz Cruz María Dolores 
Published: September 2004

AbstractSubmicroscopic intergrowths of K biotite, Na biotite and intermediate Na-K biotite from a schist near Málaga (Betic Cordilleras, Spain) were discovered using high-resolution transmission electron microscopy and analytical electron microscopy. The sample was also studied with X-ray diffraction, electron microprobe analysis, and scanning electron microscopy. Scanning electron microscopy revealed that the Na-enriched biotite is concentrated in albite-rich microdomains, albite being partially replaced by biotite. These images also revealed that both K and Na-K biotite grains appear locally retrograded to kaolinite. Transmission electron microscopic data indicated that K biotite, Na biotite and Na-K biotite form parallel or subparallel packets with interfaces parallel to the basal planes of biotite. Potassium biotite forms thick packets, chemically homogeneous, with a basal spacing of 10.1 Å. Sodium biotite also occurs as chemically homogeneous stacks of layers with a 9.78 Å periodicity. Sodium-K biotite shows, on the contrary, variable composition and basal spacings intermediate between K and Na biotites. Analytical electron microscopic data revealed important chemical differences between Na and K biotites, which affect both the tetrahedral and the octahedral sheets. Both electron microprobe analysis and analytical electron microscopy indicated that the trioctahedral micas show relatively low interlayer occupancy, suggesting the presence of H3O+ replacing the interlayer cations. Partial hydration of biotite explains the presence of a weak 14 Å reflection in the X-ray patterns. Both chemical and textural data suggested that these trioctahedral micas grew during a common prograde metamorphic episode, the phases with intermediate composition probably being metastable.
Dehydration and rehydration of palygorskite and the influence of water on the nanopores
Authors: Kuang Wenxing , Facey Glenn A. , Detellier Christian 
Published: September 2004

AbstractThe dehydration and rehydration processes of the clay mineral palygorskite (PFl-1) were studied by textural analysis, thermogravimetric analysis connected with mass spectrometry (TGA-MS), and29Si and1H solid-state NMR techniques. The TGA-MS results clearly reveal weight losses at maxima of 70°C, 190°C, 430°C and 860°C. PFl-1 is characterized by a micropore area of 93 m2/g, corresponding to a micropore volume of 47 mm3/g. These values are also obtained for the sample heated up to 200°C for 20 h. Further heating at 300°C produces a collapse of the structure, as shown by the almost complete loss of microporosity.The29Si NMR spectra of palygorskite show two main resonances at −92.0 and −97.5 ppm, attributed to one of the two pairs of equivalent Si nuclei in the basal plane. A minor resonance at −84.3 ppm is attributed to Q2(Si-OH) Si nuclei. The resonance at −92.0 ppm is assigned to the central Si position, while the resonance at −97.5 ppm is assigned to the edge Si sites. It is confirmed bysolid-state29Si and1H NMR that nearly complete rehydration is achieved by exposing palygorskite samples that have been partially dehydrated at 150°C and 300°C, to D2O or water vapor at room temperature. When the rehydration is accomplished with D2O, the atoms are disordered across all the protons sites.
Effects of γ radiation on chromate immobilization by calcined hydrotalcites
Authors: Martinez-Gallegos Sonia , Bulbulian Silvia 
Published: September 2004

AbstractThe ability of hydrotalcites to retain anionic wastes was studied. In particular, Cr(VI)-adsorbed hydrotalcites were heated to immobilize Cr(VI) in the solid sample. When the heating temperature increased up to 500°C, the lamellar structure of hydrotalcite was lost. At high temperatures (1200°C), the solids were recrystallized in the form of a spinel. Lixiviation with 1 N and 5 N NaCl solutions were utilized to simulate the effect of sea water and of concentrated NaCl solutions in salt mines on the immobilization of Cr. Radiation damage on the solid containing the immobilized Cr was studied by γ-irradiating with a 60Co source at 1000 and 6000 kGy. The Cr-containing samples heated at 1200°C, whether irradiated or not, safely immobilized Cr in the hydrotalcite mainly in the form of MgCr2O4 spinel. Irradiation of hydrotalcites revealed two different effects: (1) samples heated up to 1200°C evolved as a solid in which chromium was retained more firmly than in the non-irradiated material, irradiation enhancing the spinel formation; (2) the structure of samples heated at 1200°C developed a preferential crystallite orientation rather than a purely random one or new location of chromium ions, this effect did not affect Cr immobilization in the solid. Chromium lixiviation with 5 N NaCl solution was always less than the corresponding value with 1 N NaCl solution, probably due to the poor mobility of Cl− ions in the highly concentrated NaCl solution.
Organic Crystal Structure Analysis and Prediction
Authors: Gavezzotti Angelo , Price Sarah L. 
Published: September 2004

Abstract
Organic crystals are central to the pharmaceutical, energetic, and specialty chemicals industries, and so a computational approach to predicting organic crystal structures and their properties has the potential for playing a major role in the design of new organic materials. In recent years, considerable progress has been made toward this end, moving from studies on rigid hydrocarbons to molecules with an increasing range of polar functional groups, as models for the intermolecular forces have become more realistic. Conformational flexibility produces additional challenges, as do the small energy differences between different observed crystal structures. Nevertheless, the path to more accurate thermodynamic and static property predictions is established, and the main fundamental barrier to organic crystal structure prediction is in the kinetic factors that control crystallization.
Natural Transition Orbitals
Authors: Batista Enrique R. , Martin Richard L. 
Published: September 2004

Abstract
The result of a calculation of excited states, be it via configuration interaction methods or density functional response theory, is a set of coefficients describing the contribution that individual orbital excitations make to the total transition. Often times, there is no dominant amplitude describing the transition, making its qualitative description difficult. Natural transition orbitals dramatically simplify the situation by providing a compact representation of the transition density matrix. This is accomplished using the corresponding orbital transformation of Amos and Hall, which renders the transition density matrix diagonal and provides a unique correspondence between the excited ‘particle’ and empty ‘hole’.
MCSTEP‐ A Multiconfigurational‐based Spin Adapted Electron Propagator Approach for Ionization Potentials and Electron Affinities
Authors: Yeager Danny L. 
Published: September 2004

AbstractWith electron propagator (also known assingle particle Green's function) techniques, electron removal and attachment energies are calculated directly. This avoids the sometimes inaccurate process of separately determining the total electronic energies of the neutral and ionic state and subtracting one large number from another to obtain a relatively small value, that is, the ionization potential (IP) or electron affinity (EA) of a molecule. Traditionally, these electron propagator methods used a single determinant wave function as the ‘zero order’ initial state, which was improved with Møller–Plesset perturbation theory. Although these usual perturbative electron propagator methods have been very successful, they are limited in applicability. Usual perturbative approaches usually cannot handle reliably (or at all) systems with initial states that are open shell and/or highly correlated (nondynamical correlation) for either IPs or EAs.We specifically designed the multiconfigurational spin tensor electron propagator method (MCSTEP) and its predecessor the multiconfigurational electron propagator (MCEP) method to provide accurate IPs and EAs for systems that cannot be accurately handled by usual perturbational approaches to single particle Green's function methods, namely, when the initial state is open shell and/or has nondynamical correlation that must be accounted for. In addition, of course, the goal is to also be able to provide accurate IPs and EAs for systems with closed shell initial states without nondynamical correlation, that is, those systems that could be handled as well by usual perturbational electron propagator methods.In this article, I will first review the theory behind the multiconfigurational spin tensor electron propagator method. Since the introduction of MCSTEP over 15 years ago, several accurate MCSTEP atomic and molecular IPs and EAs have been determined. I will summarize several of the more significant calculations to date.An electron propagator method using a multiconfigurational second‐order perturbation theory wave function as the initial state in the fermion operator block (block 1) in the MCSTEP matrix equations was initially developed by Heryadi and Yeager. In the other blocks, an MCSCF wave function is the initial state. This new method is called EPCASPT2 and should be viewed as an extension of MCSTEP. In this article, we will review the theory behind EPCASPT2 and some of the recent calculations done using a CASPT2 wave function as the initial state in the electron propagator. We compare our results with the results of the calculations using multiconfigurational spin tensor electron propagator, full configuration interaction, and for the molecules, the multireference configuration interaction method with the same geometries and basis sets.
Aza‐Baylis–Hillman Reaction of β‐Substituted Activated Olefins with N‐Tosyl Imines
Authors: Shi Yong‐Ling , Xu Yong‐Mei , Shi Min 
Published: September 2004

AbstractAza‐Baylis–Hillman reactions of β‐substituted activated olefins such as crotonaldehyde, (E)‐propenyl phenyl ketone, hex‐2‐enal or pent‐3‐en‐2‐one with N‐tosyl imines can be carried out for the first time in the presence of tertiary phosphine Lewis bases such as PPh2Me or PPhMe2 to give the corresponding Baylis–Hillman adducts in moderate to good yields under mild reaction conditions.
Scale‐Up Studies for the Asymmetric Juliá–Colonna Epoxidation Reaction
Authors: Gerlach Arne , Geller Thomas 
Published: September 2004

AbstractThe asymmetric Juliá–Colonna epoxidation reaction under triphasic/PTC conditions has been successfully scaled‐up to a one‐hundred gram substrate level providing the corresponding epoxy ketone with high optical purity (up to 97% ee) and in good yield (75–78%). The amount of polyamino acid catalyst could be reduced leading to a simplified reaction work‐up. In order to minimise the overall reaction time baffled reactors with pitched‐blade impellers have been employed.
Polystyrene‐Anchored Cinchona Ammonium Salts: Easily Recoverable Phase‐Transfer Catalysts for the Asymmetric Synthesis of α‐Amino Acids
Authors: Chinchilla Rafael , Mazón Patricia , Nájera Carmen 
Published: September 2004

AbstractCinchonidine, epicinchonidine, cinchonine or quinine have been N‐anchored to cross‐linked polystyrene (Merrifield resin) or grafted polystyrene (SynPhaseTM Lanterns) affording polymer‐supported chiral ammonium salts which are employed as phase‐transfer catalysts in the asymmetric alkylation of N‐(diphenylmethylene)glycine esters. These new polymeric catalysts can be easily recovered after the reaction by simple filtration and reused.
anti‐Selective Asymmetric Synthesis of β‐Hydroxy‐α‐amino Acid Esters by the in situ Generated Chiral Quaternary Ammonium Fluoride‐Catalyzed Mukaiyama‐Type Aldol Reaction
Authors: Ooi Takashi , Taniguchi Mika , Doda Kanae , Maruoka Keiji 
Published: September 2004

AbstractThe aldol coupling of ketene silyl acetal 2 derived from the glycinate Schiff base with aldehydes can be efficiently catalyzed by an in situ generated, chiral quaternary ammonium fluoride of type 1 under mild, neutral conditions, affording the corresponding anti‐β‐hydroxy‐α‐amino esters predominantly with excellent enantioselectivities.
Highly Enantio‐ and Diastereoselective Organocatalytic Domino Michael‐Aldol Reactions of β‐Diketone and β‐Ketosulfone Nucleophiles with α,β‐Unsaturated Ketones
Authors: Pulkkinen Juha , Aburel Pompiliu S. , Halland Nis , Jørgensen Karl Anker 
Published: September 2004

AbstractA chiral imidazolidine catalyst was shown to catalyze the highly enantio‐ and diastereoselective domino Michael‐aldol reaction of β‐diketone and β‐ketosulfone derivatives with α,β‐unsaturated ketones to form optically active cyclohexanones having three or four contiguous chiral centers. The Michael‐aldol adducts were formed as single diastereomers in up 99% ee.
The Development of the Asymmetric Morita—Baylis—Hillman Reaction Catalyzed by Chiral Brønsted Acids
Authors: McDougal Nolan T. , Trevellini Whitney L. , Rodgen Stacy A. , Kliman Laura T. , Schaus Scott E. 
Published: September 2004

AbstractThis report describes the development of a chiral Brønsted acid‐catalyzed asymmetric Morita–BaylisHillman (MBH) reaction of cyclohexenone with aldehydes. During the course of our studies on chiral Lewis acid‐promoted MBH reactions, we discovered that chiral binaphthol‐derived Brønsted acids serve as promoters of the asymmetric MBH reaction. We propose that the phosphonium enolate of cyclohexenone is stabilized via hydrogen‐bonding with the binaphthol‐derived Brønsted acid, creating a chiral nucleophile. A practical and efficient set of conditions was developed using stoichiometric PEt3 as the nucleophilic promoter and catalytic amounts of a binaphthol‐derived Brønsted acid to effect the reaction of cyclohexenone with various aliphatic and aromatic aldehydes in good yields and enantiomeric excesses (up to 96% ee).
Proline‐Derived N‐Sulfonylcarboxamides: Readily Available, Highly Enantioselective and Versatile Catalysts for Direct Aldol Reactions
Authors: Berkessel Albrecht , Koch Burkhard , Lex Johann 
Published: September 2004

AbstractProline catalysis of the asymmetric direct aldol reaction involves both the secondary amine function and the carboxyl group of the amino acid. N‐Sulfonylcarboxamides are known to be of similar acidity as carboxylic acids, and three N‐arylsulfonyl derivatives of L‐proline amide were synthesized as functionalized and versatile derivatives of L‐Pro. Their catalytic performance was evaluated in the direct aldol addition of acetone to 4‐nitrobenzaldehyde. Significantly improved reactivities and enantioselectivities were achieved in various solvents at low catalyst loadings (5–10 mol %) and at room temperature, with ees ranging up to 98%, whereas L‐proline itself afforded a maximum ee of 80% (in DMSO). Thus, N‐arylsulfonyl derivatives of proline amide represent a novel class of highly enantioselective catalysts for direct aldol reactions. Furthermore, the N‐arylsulfonyl substituent suggests possibilities for incorporation into larger catalyst assemblies (including immobilization) without affecting the catalytically active functional groups.
Catalysis of the Hajos—Parrish—Eder—Sauer—Wiechert Reaction by cis‐ and trans‐4,5‐Methanoprolines: Sensitivity of Proline Catalysis to Pyrrolidine Ring Conformation
Authors: Cheong Paul Ha‐Yeon , Houk K. N. , Warrier Jayakumar S. , Hanessian Stephen 
Published: September 2004

AbstractMethanoprolines are found to be catalysts for the Hajos–Parrish–Eder–Sauer–Wiechert reaction.[1] cis‐4,5‐Methanoproline exhibits catalytic ability similar to proline (86% yield, 93% ee), whereas the trans‐4,5‐methanoproline is less selective (67% yield, 83% ee) and shows less acceleration. The reaction was also studied with hybrid density functional theory (B3LYP). The nearly planar cis‐4,5‐methanoproline amine better reflects the planar iminium of the transition states than the pyramidalized trans‐4,5‐methanoproline. This difference in conformation is responsible for the observed higher enantioselectivity and enhanced catalytic behavior of the cis‐4,5‐methanoproline.
A locus for posterior polymorphous corneal dystrophy (PPCD3) maps to chromosome 10
Authors: Shimizu Satoko , Krafchak Charles , Fuse Nobuo , Epstein Michael P. , Schteingart Miriam T. , Sugar Alan , Eibschitz‐Tsimhoni Maya , Downs Catherine A. , Rozsa Frank , Trager Edward H. , Reed David M. , Boehnke Michael , Moroi Sayoko E. , Richards Julia E. 
Published: September 2004

AbstractPosterior polymorphous corneal dystrophy (PPCD) is an autosomal dominant disorder characterized by corneal endothelial abnormalities, which can lead to blindness due to loss of corneal transparency and sometimes glaucoma. We mapped a new locus responsible for PPCD in a family in which we excluded the previously reported PPCD locus on 20q11, and the region containing COL8A2 on chromosome 1. Results of a 317‐marker genome scan provided significant evidence of linkage of PPCD to markers on chromosome 10, with single‐point LOD scores of 2.63, 1.63, and 3.19 for markers D10S208 (at $\hat \theta = 0.03$), D10S1780 (at $\hat \theta = 0.00$), and D10S578 (at $\hat \theta = 0.06$). A maximum multi‐point LOD score of 4.35 was found at marker D10S1780. Affected family members shared a haplotype in an 8.55 cM critical interval that was bounded by markers D10S213 and D10S578. Our finding of another PPCD locus, PPCD3, on chromosome 10 indicates that PPCD is genetically heterogeneous. Guttae, a common corneal finding sometimes observed along with PPCD, were found among both affected and unaffected members of the proband's sib ship, but were absent in the younger generations of the family. Evaluation of phenotypic differences between family members sharing the same affected haplotype raises questions about whether differences in disease severity, including differences in response to surgical interventions, could be due to genetic background or other factors independent of the PPCD3 locus. © 2004 Wiley‐Liss, Inc.
Clinical variability in a Noonan syndrome family with a new PTPN11 gene mutation
Authors: Bertola Débora Romeo , Pereira Alexandre C. , Oliveira Paulo S.L. de , Kim Chong A. , Krieger José Eduardo 
Published: September 2004

AbstractNoonan syndrome (NS) is an autosomal dominant disorder comprising short stature, facial dysmorphism, short and/or webbed neck, heart defects, and cryptorchidism in males. The gene responsible for the disorder (PTPN11) was recently identified, and explains 30–50% of the cases clinically diagnosed as NS. Cardiofaciocutaneous (CFC) syndrome, a similar but distinct entity, is characterized by relative macrocephaly, characteristic facial appearance, ectodermal abnormalities (sparse and friable hair, sparse eyebrows, hyperkeratotic skin), congenital heart defects, and growth and mental retardation. We describe on a young woman who presents clinical features of NS (short stature, triangular facies, with dowslanting palpebral fissures and apparent hypertelorism, webbed neck, pulmonary stenosis, bleeding diathesis, prominent corneal nerves), but with a more prominent ectodermal involvement (sparse and very coarse hair, sparse eyebrows and eyelashes) and developmental delay/mental retardation, which are characteristic of CFC patients. Sequencing of the PTPN11 gene showed a T411M substitution, not previously described in patients with NS. The same mutation was found in her mother and older sister, not initially considered to be affected by NS, but with very subtle clinical findings compatible with this diagnosis. Molecular dynamic studies indicate that this new mutation, similar to other previously described mutations, favors a more active protein conformation. However, the main disruptive effect is not directly in the catalytic domain, suggesting that the location of this mutation could make the protein more susceptible to gene–gene or gene–environment interactions. Atypical cases of NS should be screened for mutations in the PTPN11 gene and in the case of a positive result, first‐degree relatives should also be tested for the specific mutation. © 2004 Wiley‐Liss, Inc.
Deficiency of pyruvate dehydrogenase caused by novel and known mutations in the E1α subunit
Authors: Cameron Jessie M. , Levandovskiy Valeriy , MacKay Neviana , Tein Ingrid , Robinson Brian H. 
Published: September 2004

AbstractPyruvate dehydrogenase (PDH)‐complex deficiency (OMIM 312170) is a clinically heterogeneous disorder, with phenotypes ranging from fatal lactic acidosis (LA) in the newborn to chronic neurological dysfunction. To date, over 80 different mutations have been identified in the PDHA1 gene in patients with PDH complex deficiency, which are thus thought to contribute to the PDH deficient phenotype. We have identified 14 additional patients with total PDH complex deficiency, all of whom were found to contain mutations within the PDHA1 gene (E1α subunit). The mutations include both missense mutations and duplications. Eight of these patients had novel mutations, and the remaining had mutations that have been identified previously in PDH complex deficient patients, with residual fibroblast activity ranging from 2.4 to 69% of control values. The nature of these mutations illustrates the variability in phenotype for a given gene defect, with intermittent ataxia being the mildest presentation, Leigh syndrome being the most common and severe neonatal LA the most severe. © 2004 Wiley‐Liss, Inc.
Costello syndrome with pancreatic islet cell hyperplasia
Authors: Dickson Patricia I. , Briones Norman Y. , Baylen Barry G. , Jonas Adam J. , French Samuel W. , Lin Henry J. 
Published: September 2004

AbstractA 3‐month‐old boy with Costello syndrome (CS) developed respiratory distress and fatal arrhythmias. An autopsy showed cardiac hypertrophy, mild coarctation of the aorta, and pancreatic islet cell hyperplasia. To our knowledge, this is the first report of a pancreatic abnormality in CS. Islet cell hyperplasia has also been observed in leprechaunism, Beckwith–Wiedemann (BWS), and Simpson–Golabi–Behmel syndromes. The syndromes are thought to involve abnormal insulin or insulin‐like growth factor (IGF) pathways. Clinical similarities among these disorders and CS, together with the finding of islet cell hyperplasia, suggest that they may be related. © 2004 Wiley‐Liss, Inc.