bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Anatase TiO2 Nanoparticles with β‐Cyclodextrin as a Supramolecular Shell
Authors: Li Landong , Sun Xiaohong , Yang Yali , Guan Naijia , Zhang Fuxiang 
Published: October 2006

AbstractWe report a novel, green hydrothermal‐synthesis route to well‐dispersed anatase TiO2 nanoparticles with particle sizes of 9–16 nm in the presence of β‐CD (β‐cyclodextrin). During the synthesis process, the CD‐containing synthesis mixture assembled in both longitudinal and latitudinal directions. Driven by the interaction between molecules, the β‐CDs assembled in the longitudinal direction to form long‐chain compounds, whereas in the latitudinal direction, they tended to form regular aggregates through coordination with the Ti species from the hydrolysis of tetrabutyl titanate. In view of the effect of the coordination and the steric hindrance of β‐CDs as a supramolecular shell, homogeneous nuclei and slow growth of TiO2 crystals during the synthesis process was observed, which was responsible for the formation of uniform TiO2 nanoparticles. The low β‐CD dosage and the high product yield (>90 %) demonstrated well the potential of this synthesis route in the large‐scale industrial production of anatase nanoparticles.
Orbital Overlap and Chemical Bonding
Authors: Krapp Andreas , Bickelhaupt F. Matthias , Frenking Gernot 
Published: October 2006

AbstractThe chemical bonds in the diatomic molecules Li2–F2 and Na2–Cl2 at different bond lengths have been analyzed by the energy decomposition analysis (EDA) method using DFT calculations at the BP86/TZ2P level. The interatomic interactions are discussed in terms of quasiclassical electrostatic interactions ΔEelstat, Pauli repulsion ΔEPauli and attractive orbital interactions ΔEorb. The energy terms are compared with the orbital overlaps at different interatomic distances. The quasiclassical electrostatic interactions between two electrons occupying 1s, 2s, 2p(σ), and 2p(π) orbitals have been calculated and the results are analyzed and discussed. It is shown that the equilibrium distances of the covalent bonds are not determined by the maximum overlap of the σ valence orbitals, which nearly always has its largest value at clearly shorter distances than the equilibrium bond length. The crucial interaction that prevents shorter bonds is not the loss of attractive interactions, but a sharp increase in the Pauli repulsion between electrons in valence orbitals. The attractive interactions of ΔEorb and the repulsive interactions of ΔEPauli are both determined by the orbital overlap. The net effect of the two terms depends on the occupation of the valence orbitals, but the onset of attractive orbital interactions occurs at longer distances than Pauli repulsion, because overlap of occupied orbitals with vacant orbitals starts earlier than overlap between occupied orbitals. The contribution of ΔEelstat in most nonpolar covalent bonds is strongly attractive. This comes from the deviation of quasiclassical electron–electron repulsion and nuclear–electron attraction from Coulomb's law for point charges. The actual strength of ΔEelstat depends on the size and shape of the occupied valence orbitals. The attractive electrostatic contributions in the diatomic molecules Li2–F2 come from the s and p(σ) electrons, while the p(π) electrons do not compensate for nuclear–nuclear repulsion. It is the interplay of the three terms ΔEorb, ΔEPauli, and ΔEelstat that determines the bond energies and equilibrium distances of covalently bonded molecules. Molecules like N2 and O2, which are usually considered as covalently bonded, would not be bonded without the quasiclassical attraction ΔEelstat.
Exploring Base‐Pair‐Specific Optical Properties of the DNA Stain Thiazole Orange
Authors: Jarikote Dilip Venkatrao , Krebs Nils , Tannert Sebastian , Röder Beate , Seitz Oliver 
Published: October 2006

AbstractDouble‐stranded DNA offers multiple binding sites to DNA stains. Measurements of noncovalently bound dye–nucleic acid complexes are, necessarily, measurements of an ensemble of chromophores. Thus, it is difficult to assign fluorescence properties to base‐pair‐specific binding modes of cyanine dyes or, vice versa, to obtain information about the local environment of cyanines in nucleic acids by using optical spectroscopy. The feasibility to stain DNA and simultaneously probe local perturbations by optical spectroscopy would be a valuable asset to nucleic acid research. So‐called FIT probes (forced intercalation probes) were used to pinpoint the location of the DNA stain thiazole orange (TO) in PNA⋅DNA duplexes. A detailed analysis of the base‐pair dependence of optical properties is provided and enforced binding of TO is compared with “classical” binding of free TO‐PRO1. UV‐visible absorbance, circular dichroism (CD) and fluorescence spectroscopy, and melting‐curve analyses confirmed site‐specific TO intercalation. Thiazole orange exhibited base‐specific responses that are not observed in noncovalent dye–nucleic acid complexes, such as an extraordinary dependence of the TO extinction coefficient (±60 % variation of the averaged εmax of 57 000 M−1 cm−1) on nearest‐neighbor base pairs. TO signals hybridization, as shown by increases in the steady‐state fluorescence emission. Studies of TO fluorescence lifetimes in FIT–PNA and in DNA⋅DNA and PNA⋅DNA complexes highlighted four different fluorescence‐decay processes that may be closed or opened in response to matched or single‐mismatched hybridization. A very fast decay process (0.04–0.07 ns) and a slow decay process (2.33–3.95 ns) provide reliable monitors of hybridization, and the opening of a fast decay channel (0.22–0.48 ns) that resulted in an attenuation of the fluorescence emission is observed upon the formation of mismatched base pairs.
Stereoselective Preparation of Six Diastereomeric Quatercyclopropanes from Bicyclopropylidene and Some Derivatives
Authors: von Seebach Malte , Kozhushkov Sergei I. , Schill Heiko , Frank Daniel , Boese Roland , Benet‐Buchholz Jordi , Yufit Dmitry S. , de Meijere Armin 
Published: October 2006

AbstractDiastereomericmeso‐ andd,l‐bis(bicyclopropylidenyl) (5) were obtained upon oxidation with oxygen of a higher‐order cuprate generated from lithiobicyclopropylidene (4) in 50 and 31 % yield, respectively. Their perdeuterated analoguesmeso‐[D14]‐ andd,l‐[D14]‐5were obtained along the same route from perdeuterated bicyclopropylidene [D8]‐3(synthesized in six steps in 7.4 % overall yield from [D8]‐THF) in 20.5 % yield each. Dehalogenative coupling of 1,1‐dibromo‐2‐cyclopropylcyclopropane (6) gave a mixture of all possible stereoisomers of 1,5‐dicyclopropylbicyclopropylidene16in 69 % yield, from which (Z)‐cis‐16was separated by preparative gas chromatography (26 % yield). The crystal structure ofmeso‐5looks like a superposition of the crystal structures of two outer bicyclopropylidene units (3) and one inner s‐trans‐bicyclopropyl unit, whereas the two outer cyclopropyl moieties adopt agaucheorientation with respect to the cyclopropane rings at the inner bicyclopropylidene units in (Z)‐cis‐16. Birch reduction with lithium in liquid ammonia ofmeso‐5andd,l‐5gave two pairs of diastereomeric quatercyclopropanestrans,trans‐(R*,S*,R*,S*)‐17/cis,trans‐(R*,S*,R*,R*)‐18andtrans,trans‐(R*,S*,S*,R*)‐19/cis,trans‐(R*,S*,S*,S*)‐20in 97 and 76 % yield, respectively, in a ratio 9:1 for every pair. The latter diastereomer was also obtained as the sole product by Birch reduction of (Z)‐cis‐16in 96 % yield. Under the same conditions, tetradecadeuterio analoguestrans,trans‐[D14]‐(R*,S*,R*,S*)‐17/cis,trans‐[D14]‐(R*,S*,R*,R*)‐18(8:1) andtrans,trans‐[D14]‐(R*,S*,S*,R*)‐19/cis,trans‐[D14]‐(R*,S*,S*,S*)‐20(12:1) were prepared frommeso‐[D14]‐5andd,l‐[D14]‐5in 37 and 63 % yield, respectively. Reduction ofmeso‐5with diimine gave thecis,cis‐quatercyclopropane (S*,S*,R*,R*)‐21as the main product (58 % yield) along with thecis,trans‐diastereomer (S*,S*,R*,S*)‐18(29 % yield). Thus, five of the six possible diastereomeric quatercyclopropanes were obtained frommeso‐5,d,l‐5, and (Z)‐cis‐16. The X‐ray crystal structure analyses oftrans,trans‐(R*,S*,R*,S*)‐17andcis,cis‐(S*,S*,R*,R*)‐21revealed for the both an unusual conformation in which the central bicyclopropyl unit adopts an s‐trans‐(antiperiplanar) orientation withϕ=180.0°, and the two terminal bicyclopropyl moieties adopt a synclinal conformation withϕ=49.8 and 72.0°, respectively. In solution the vicinal coupling constants 〈3JH,H〉 intrans,trans‐(R*,S*,R*,S*)‐[D14]‐17,trans,trans‐(R*,S*,S*,R*)‐[D14]‐19,trans,cis‐(R*,S*,R*,R*)‐[D14]‐18andtrans,cis‐(R*,S*,S*,S*)‐[D14]‐20were found to be 4.1, 4.7, 5.9 and 5.9 Hz, respectively. This indicates a predominance of the all‐gaucheconformer in (R*,S*,R*,S*)‐17and a decreasing fraction of it in this sequence of the other diastereomers.
Structural and Magnetic Resolution of a Two‐Step Full Spin‐Crossover Transition in a Dinuclear Iron(II) Pyridyl‐Bridged Compound
Authors: Amoore Jarrod J. M. , Kepert Cameron J. , Cashion John D. , Moubaraki Boujemaa , Neville Suzanne M. , Murray Keith S. 
Published: October 2006

AbstractA dinuclear iron(II) complex containing the new pyridyl bridging ligand, 2,5‐di(2′,2′′‐dipyridylamino)pyridine (ddpp) has been synthesised and characterised by single‐crystal X‐ray diffraction, magnetic susceptibility and Mössbauer spectral methods. This compound, [Fe2(ddpp)2(NCS)4]⋅4 CH2Cl2, undergoes a two‐step full spin crossover. Structural analysis at each of the three plateau temperatures has revealed a dinuclear molecule with spin states HS–HS, HS–LS and LS–LS (HS: high spin, LS: low spin) for the two iron(II) centres. This is the first time that resolution of the metal centres in a HS–LS ordered state has been achieved in a two‐step dinuclear iron(II) spin‐crossover compound. Thermogravimetric data show that the dichloromethane solvate molecules can be removed in two distinct steps at 120 °C and 200 °C. The partially de‐solvated clathrate, [Fe2(ddpp)2(NCS)4]⋅CH2Cl2, undergoes a one‐step transition with an increased transition temperature with respect to the as synthesised material. Structural characterisation of this material reveals subtle changes to the coordination geometries at each of the iron(II) centres and striking changes to the local environment of the dinuclear complex. The fully de‐solvated material remains high spin over all temperatures. Interestingly, the solvent can be re‐introduced into the monosolvated solid to achieve complete conversion back to the original two‐step crossover material, [Fe2(ddpp)2(NCS)4]⋅4 CH2Cl2.
Conformational Control of [26]Hexaphyrins(1.1.1.1.1.1) by meso‐Thienyl Substituents
Authors: Suzuki Masaaki , Osuka Atsuhiro 
Published: October 2006

AbstractConformational preference and chemical stability of meso‐aryl‐substituted [26]hexaphyrins(1.1.1.1.1.1) ([26]ArH) depend upon meso‐aryl substituents. Although only a planar and rectangular conformation (type‐II conformation) has been identified for [26]ArH so far, we have demonstrated here that a different conformation with all the pyrroles pointing inward (type‐I conformation) is preferred for [26]ArH (7 and 11‐I) bearing small 2‐thienyl or 3‐thineyl substituents at 15‐ and 30‐positions. Both type‐I and type‐II [26]ArH exhibit diatropic ring currents, reflecting aromatic character. Type‐I [26]ArH, such as 7 and 11‐I, have been shown to serve as an effective ligand for PdII ions to provide bis‐PdII complexes 12 and 13 with N3C1 coordination through facile CH bond activation.
Long‐term outcome of hematuria home screening for bladder cancer in men
Authors: Messing Edward M. , Madeb Ralph , Young Terry , Gilchrist Kennedy W. , Bram Lora , Greenberg E. Barry , Wegenke John D. , Stephenson Laura , Gee Jason , Feng Changyong 
Published: October 2006

AbstractBACKGROUND.The objectives of this study were to determine whether bladder cancer (BC) screening in healthy men could lead to earlier detection and reduced BC mortality compared with unscreened men and to determine long‐term outcomes of a geographically defined, unscreened population with newly diagnosed BC.METHODS.In 1987 and from 1998 to 1992, 1575 men ages 50 years and older who were solicited from well patient rosters in clinics in and around Madison, Wisconsin, tested their urine repetitively with a chemical reagent strip for hemoglobin. Participants who had positive test results underwent standard urologic evaluation. BC grades and stages and the outcomes of men with BC detected by screening were compared with the grades, stages, and outcomes of 87% of men ages 50 years and older with newly diagnosed BC who were reported to the Wisconsin Tumor Registry in 1988 (n = 509 men).RESULTS.Two hundred fifty‐eight screening participants (16.4%) were evaluated for hematuria, and 21 participants (8.1%) were diagnosed with BC. Proportions of low‐grade (Grade 1 and 2) superficial (Stage Ta and T1) versus high‐grade (Grade 3) superficial or invasive (Stage ≥ T2) cancers in screened men (52.4% vs. 47.7%) and in men from the tumor registry (60.3% vs. 39.7%) were similar (P = .50). The proportion of high‐grade superficial or invasive BCs that were invasive were lower in screened men (10%) than in unscreened men (60%; P = .002). At 14 years of follow‐up, no men with screen‐detected BC had died of BC, whereas 20.4% of men with unscreened BC had died of BC (P = .02).CONCLUSIONS.Screening effected the early detection of BC and may reduce mortality from BC compared with BC that is diagnosed at standard clinical presentation. Cancer 2006. © 2006 American Cancer Society.
Identification of high‐grade cervical dysplasia by the detection of p16INK4a in cell lysates obtained from cervical samples
Authors: Wentzensen Nicolas , Hampl Monika , Herkert Matthias , Reichert Anja , Trunk Marcus J. , Poremba Christopher , Ridder Ruediger , von Knebel Doeberitz Magnus 
Published: October 2006

AbstractBACKGROUND.Current cervical cancer screening approaches are based on cytology supplemented by human papillomavirus (HPV) testing in some settings. Whereas cytology is laborious and depends on the cytologists' experience, HPV testing has limited specificity when it is used to detect high‐grade lesions. A dichotomous test to identify high‐grade lesions with greater specificity may be a useful tool for cervical cancer screening. p16INK4a is a cell‐cycle regulator that has demonstrated strong overexpression in cervical precancer cells and cervical cancer induced by the deregulated expression of HPV oncogenes.METHODS.The authors used a sandwich enzyme‐linked immunosorbent assay (ELISA) to quantify the amount of solubilized p16INK4a protein in lysates that were prepared from cervical samples to detect high‐grade cervical lesions. In total, 187 specimens that were obtained after sampling for conventional cytology in women who attended a cervical colposcopy clinic were analyzed. Seventy‐six women underwent a biopsy, and 45 of those women showed histologically confirmed, high‐grade cervical intraepithelial neoplasia.RESULTS.For 76 women with biopsy‐proven diagnoses, receiver operating characteristic (ROC) analysis of different cutoff values showed an area under the ROC curve of 0.89 for the detection of high‐grade cervical dysplasia. At a cutoff value of 8 U/mL, the sensitivity of the p16INK4a ELISA for detecting high‐grade dysplastic cervical lesions was 96%.CONCLUSIONS.The data obtained in this study suggested that ELISA‐based quantification of solubilized p16INK4a protein may have high sensitivity for detecting cervical precancer. Further population‐based studies will be necessary to analyze the specificity and predictive values of p16INK4a protein quantification in cervical samples. Cancer 2006. © 2006 American Cancer Society.
Expression of protein kinase C‐substrate mRNAs in the basal ganglia of adult and infant macaque monkeys
Authors: Higo Noriyuki , Oishi Takao , Yamashita Akiko , Murata Yumi , Matsuda Keiji , Hayashi Motoharu 
Published: October 2006

AbstractWe performed in situ hybridization histochemistry on the monkey basal ganglia to investigate the mRNA localization of three protein kinase C substrates (GAP‐43, MARCKS, and neurogranin), of which expression plays a role in structural changes in neurites and synapses. Weak hybridization signals for GAP‐43 mRNA and intense signals for both MARCKS and neurogranin mRNAs were observed in the adult neostriatum. All three of the mRNAs were expressed in both substance P‐positive direct pathway neurons and enkephalin‐positive indirect pathway neurons. In the nucleus accumbens, the hybridization signals for the three mRNAs were weaker than those in the neostriatum. Double‐label in situ hybridization histochemistry in the neostriatum revealed that GAP‐43 and neurogranin mRNAs were expressed in a subset of MARCKS‐positive neurons. While intense hybridization signals for MARCKS mRNA were observed in all of the other basal ganglia regions such as the globus pallidus, substantia innominata, subthalamic nucleus, and substantia nigra, intense signals for GAP‐43 mRNA were restricted to the substantia innominata and substantia nigra pars compacta. No signal for neurogranin mRNA was observed in the basal ganglia regions outside the neostriatum and the nucleus accumbens. These results indicate that the protein kinase C substrates are abundant in some specific connections in cortico‐basal ganglia circuits. Developmental analysis showed that the expression level in the putamen and nucleus accumbens, but not in the caudate nucleus, was higher in the infant than in the adult, suggesting that synaptic maturation in the caudate nucleus occurs earlier than that in the putamen and nucleus accumbens. J. Comp. Neurol. 499:662–676, 2006. © 2006 Wiley‐Liss, Inc.
Estradiol‐induced modulation of estrogen receptor‐β and GABA within the adult neocortex: A potential transsynaptic mechanism for estrogen modulation of BDNF
Authors: Blurton‐Jones Mathew , Tuszynski Mark H. 
Published: October 2006

AbstractEstrogen influences brain‐derived neurotrophic factor (BDNF) expression in the neocortex. However, BDNF‐producing cortical neurons do not express detectable levels of nuclear estrogen receptors; instead, the most abundant cortical nuclear estrogen receptor, ER‐β, is present in GABAergic neurons, prompting us to test the hypothesis that estrogen effects on BDNF are mediated via cortical inhibitory interneurons. Adult female ovariectomized rats were provided acute estrogen replacement and the number of cortical GABA, ER‐β, and ER‐β/GABA double‐labeled neurons was examined. Within 48 hours of injection of 17‐β‐estradiol, the number of perirhinal neurons double‐labeled for ER‐β/GABA was reduced by 28% (P < 0.01 compared to vehicle‐treated ovariectomized controls), and all cells expressing detectable levels of GABA were reduced by 19% (P < 0.01). To investigate potential relationships between estrogen receptors, GABAergic neurons, and BDNF‐expressing cells, brain sections were double‐ or triple‐labeled for ER‐β, GABAergic, and BDNF immunomarkers. The findings indicated that ER‐β‐bearing inhibitory neurons project onto other GABAergic neurons that lack nuclear estrogen receptors; these inhibitory neurons in turn innervate BDNF‐expressing excitatory cells. High estrogen states reduce cortical GABA levels, presumably releasing inhibition on BDNF‐expressing neurons. This identifies a putative two‐step transsynaptic mechanism whereby estrogen availability modulates expression of inhibitory transmitters, resulting in increased BDNF expression. J. Comp. Neurol. 499:603–612, 2006. © 2006 Wiley‐Liss, Inc.
Clinical psychology service provision and ethnic diversity within the UK: a review of the literature
Authors: Williams Patricia E. , Turpin Graham , Hardy Gillian 
Published: October 2006

AbstractThere is substantial evidence to suggest that clinical psychology services are failing to meet the psychological and clinical needs of people from minority ethnic groups. This paper reviews current knowledge and understanding of factors that may be contributing to this, by examining the diversity of clinical psychology service provisions for minority ethnic groups in the United Kingdom (UK). Research that focuses on the poor utilization of clinical psychology services by minority ethnic groups is identified, and this is related to the limitations offered by mainstream psychological services. References to developments from abroad are also included where they enhance understanding of the current situation affecting minority ethnic groups in the UK. The findings show that minority ethnic groups are generally marginalized and excluded from mainstream clinical psychology services on a number of different levels. These are often influenced by referral conventions, professional misunderstandings of psychological distress and an over‐reliance on ethnocentric and eurocentric conceptual frameworks. Cultural factors are also implicated. This review illustrates that the profession needs to be more considerate in its provision of services for minority ethnic users and indelible steps taken to increase the accessibility and credibility of clinical psychology services to Black and other minority ethnic groups. Copyright © 2006 John Wiley & Sons, Ltd.
Two‐dimensional morphogen gradient in Xenopus: Boundary formation and real‐time transduction response
Authors: Kinoshita T. , Jullien J. , Gurdon J.B. 
Published: October 2006

AbstractMorphogen gradients play an important role in pattern formation in embryo. However, the interpretation of position in a morphogen gradient is not well understood. Because it is hard to analyze morphogen gradients especially in opaque embryos such as those of Xenopus, it is necessary to fix and section the embryo, thereby eliminating the possibility of real‐time observation, and making more difficult the interpretation of events that take place in three dimensions. We describe here a two‐dimensional preparation of cells from a Xenopus blastula animal cap, in which an activin concentration gradient appears to be formed and interpreted at the same rate and in the same way as in normal embryos. We use two‐dimensional preparations of this kind to contribute the following new information about gradient formation and interpretation in embryo. We determine the dynamics of formation of an activin activity gradient in real time. We demonstrate that this gradient is established by diffusion of activin through intercellular space and does not require internalization of receptor or ligand. We also show that the generation of a boundary of gene expression depends on the interpretation, rather than a change of composition, of the concentration gradient. Developmental Dynamics 235:3189–3198, 2006. © 2006 Wiley‐Liss, Inc.
Open‐tubular capillary columns with a porous layer of monolithic polymer for highly efficient and fast separations in electrochromatography
Authors: Eeltink Sebastiaan , Svec Frantisek , Fréchet Jean M. J. 
Published: October 2006

AbstractOpen‐tubular columns for CEC separations having inner‐wall coated with a thin layer of porous monolithic polymer have been studied. A two‐step process including (i) UV‐initiated polymerization leading to a layer of porous poly(butyl methacrylate‐co‐ethylene dimethacrylate), and (ii) UV‐initiated grafting of ionizable monomers appear to be well suited for the preparation of these columns. The thickness of the porous polymer layer is controlled by the percentage of monomers in the polymerization mixture and/or length of the irradiation time. The layer thickness significantly affects retention, efficiency, and resolution in open‐tubular CEC. Under optimized conditions, column efficiencies up to 400 000 plates/m can be achieved. Use of higher temperature and application of pressure enables a significant acceleration of the open‐tubular CEC separations.