bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diverse approaches to the controlled generation of nanotextured surfaces
Authors: Ramsden Jeremy J. 
Published: August 2008

Abstract
Smooth, chemically uniform surfaces are seldom found in nature. Mimicry of natural variegation is a powerful approach for controlling chemical affinity at the nanoscale. Molecular recognition is one of the fundamental concepts underlying the functioning of living cells, and it depends on a particular relationship between the nanoscale, i.e., molecular, variegations of two potentially interacting molecular partners. The primary subject matter of this paper is how to articially generate appropriate nanoscale texture at the surfaces of materials. Excluding "pick and place" chemistry, in which essentially a Maxwellian demon intervenes to place objects with atomic precision, and nowadays achievable through an adaptation of atomic force microscopy, on the grounds that it is too slow to be practicable for fabricating useful quantities of material, three approaches are explored in some detail: (i) "powder", i.e., mixing at least two individually monofunctional (with respect to the ultimate molecular recognition task) precursor components (possibly with secondary functionality enabling them to appropriately self-assemble on a substratum); (ii) mixing polymers with the possibility of phase separation and frustrated phase separation with block copolymers; and (iii) felting. The emphasis is on processes that create more or less irregular structures, rather than regular arrays. The final section deals with the metrology of nanotexture.
Retrometabolic drug design: Principles and recent developments
Authors: Bodor Nicholas , Buchwald Peter 
Published: August 2008

Abstract
Retrometabolic drug design incorporates two major systematic approaches: the design of soft drugs (SDs) and of chemical delivery systems (CDSs). Both aim to design new, safe drugs with an improved therapeutic index by integrating structure-activity and -metabolism relationships; however, they achieve it by different means: whereas SDs are new, active therapeutic agents that undergo predictable metabolism to inactive metabolites after exerting their desired therapeutic effect, CDSs are biologically inert molecules that provide enhanced and targeted delivery of an active drug to a particular organ or site through a designed sequential metabolism that involves several steps. General principles and recent developments are briefly reviewed with various illustrative examples from different therapeutic areas with special focus on soft corticosteroids and on brain targeting.
New catalytic transformations of carboxylic acids
Authors: Gooßen Lukas J. , Gooßen Käthe , Rodríguez Nuria , Blanchot Mathieu , Linder Christophe , Zimmermann Bettina 
Published: August 2008

Abstract
A series of metal-catalyzed processes are presented, in which carboxylic acids act as sources of either carbon nucleophiles or electrophiles, depending on the catalyst employed, the mode of activation, and the reaction conditions. A first reaction mode is the addition of carboxylic acids or amides over C-C multiple bonds, giving rise to enol esters or enamides, respectively. The challenge here is to control both the regio- and stereoselectivity of these reactions by the choice of the catalyst system. Alternatively, carboxylic acids can efficiently be decarboxylated using new Cu catalysts to give aryl-metal intermediates. Under protic conditions, these carbon nucleophiles give the corresponding arenes. If carboxylate salts are employed instead of the free acids, the aryl-metal species resulting from the catalytic decarboxylation can be utilized for the synthesis of biaryls in a novel cross-coupling reaction with aryl halides, thus replacing stoichiometric organometallic reagents. An activation with coupling reagents or simple conversion to esters allows the oxidative addition of carboxylic acids to transition-metal catalysts under formation of acyl-metal species, which can either be reduced to aldehydes, or coupled with nucleophiles. At elevated temperatures, such acyl-metal species decarbonylate, so that carboxylic acids become synthetic equivalents for aryl or alkyl halides, e.g., in Heck reactions.
High-temperature gradient HPLC and LC-NMR for the analysis of complex polyolefins
Authors: Pasch Harald , Heinz Lars-Christian , Macko Tibor , Hiller Wolf 
Published: August 2008

Abstract
The synthesis and characterization of polyolefins continues to be one of the most important areas for academic and industrial polymer research. One consequence of the development of new "tailor-made" polyolefins is the need for new and improved analytical techniques for the analysis of polyolefins with respect to molar mass and chemical composition distribution. The present article briefly reviews different new and relevant techniques for polyolefin analysis. Crystallization analysis fractionation is a powerful new technique for the analysis of short-chain branching in linear low-density polyethylene (LLDPE) and the analysis of polyolefin blends and copolymers regarding chemical composition. For the fast analysis of the chemical composition distribution, a new high-temperature gradient high-performance liquid chromatography (HPLC) system has been developed. The efficiency of this system for the separation of various olefin copolymers is demonstrated. The correlation between molar mass and chemical composition can be accessed by on-line coupling of high-temperature size exclusion chromatography (HT-SEC) and 1H NMR spectroscopy. It is shown that the on-line NMR analysis of chromatographic fractions yields information on microstructure and tacticity in addition to molar mass and copolymer composition.
The duality of chemistry: Chemistry for peaceful purposes versus chemical weapons
Authors: Trapp Ralf 
Published: August 2008

Abstract
In April 1997, the Chemical Weapons Convention (CWC) entered into force, banning chemical weapons (CW) worldwide and requiring their destruction under international verification by 2007, a date that has since been extended to 2012. At the same time, the CWC aims to prevent the recurrence of CW, including their possible use by non-State actors such as terrorists. The CWC is an agreement between governments, but it also sets norms that apply, through national laws and ethical principles, to the individual scientist and engineer. Many chemists, however, have had little or no exposure during their training and professional life to the ethical norms and regulatory requirements of the CWC. At the same time, advances in the life sciences are creating enormous opportunities - with the potential of being quite beneficial to humankind but also prone to abuse. Education and awareness-raising about the norms and principles enshrined in the CWC are therefore becoming increasingly important. Through its activities in the field of chemistry education as well as its links to the chemical industry, IUPAC has responsibility, as well as capacity, to promote professional conduct that is in full compliance with the norms of the CWC.
Oxygenases for oxygen sensing
Authors: Loenarz Christoph , Chowdhury Rasheduzzaman , Schofield Christopher J. , Flashman Emily 
Published: August 2008

Abstract
In animals, cellular and physiological responses to oxygen level variations are regulated via the post-translational modification of the heterodimeric hypoxia-inducible transcription factor (HIF). Hydroxylation of the HIF-α subunit at either of two conserved prolyl residues enables binding to the von Hippel-Lindau protein (pVHL) elongin C/B complex (VCB) which targets HIF-α for degradation via the ubiquitin proteasome pathway. Hydroxylation of an asparaginyl residue in the C-terminal transcriptional activation domain of HIF-α reduces its interaction with the transcriptional coactivator p300. Thus, post-translational hydroxylation is used both to "make" (HIF-VCB) and "break" (HIF-p300) protein-protein interactions in the hypoxic response. The requirement for oxygen of the HIF prolyl and asparaginyl hydroxylases in catalysis links changes in oxygen concentration and transcription of the gene array that enables cells to adapt to hypoxia. All four identified human HIF hydroxylases are members of the Fe(II) and 2-oxoglutarate (2OG)-dependent family of oxygenases. Inhibition of HIF hydroxylases mimics the hypoxic response resulting in the upregulation of erythropoietin (EPO), vascular endothelial growth factor (VEGF), and other proteins of biomedicinal importance. We briefly review biochemical analyses on the HIF hydroxylases and discuss how their structural and mechanistic characteristics may make them suited to their oxygen-sensing role.
Mechanical Stimulation of Mesenchymal Stem Cell Proliferation and Differentiation Promotes Osteogenesis While Preventing Dietary-Induced Obesity
Authors: Luu Yen Kim , Capilla Encarnacion , Rosen Clifford J , Gilsanz Vicente , Pessin Jeffrey E , Judex Stefan , Rubin Clinton T 
Published: August 2008

Abstract
Mesenchymal stem cells (MSCs) are defined by their ability to self-renew and differentiate into the cells that form mesodermal tissues such as bone and fat. Low magnitude mechanical signals (LMMS) have been shown to be anabolic to bone and have been recently reported to suppress the development of fat in normal animals fed a regular diet. Using male C57BL/6J mice, the ability of LMMS (0.2g, 90-Hz signal applied for 15 min/d, 5 d/wk) to simultaneously promote bone formation and prevent diet-induced obesity was correlated to mechanical influences on the molecular environment of the bone marrow, as indicated by the population dynamics and lineage commitment of MSCs. Six weeks of LMMS increased the overall marrow-based stem cell population by 37% and the number of MSCs by 46%. Concomitant with the increase in stem cell number, the differentiation potential of MSCs in the bone marrow was biased toward osteoblastic and against adipogenic differentiation, as reflected by upregulation of the transcription factor Runx2 by 72% and downregulation of PPARγ by 27%. The phenotypic impact of LMMS on MSC lineage determination was evident at 14 wk, where visceral adipose tissue formation was suppressed by 28%, whereas trabecular bone volume fraction in the tibia was increased by 11%. Translating this to the clinic, a 1-yr trial in young women (15–20 yr; n = 48) with osteopenia showed that LMMS increased trabecular bone in the spine and kept visceral fat at baseline levels, whereas control subjects showed no change in BMD, yet an increase in visceral fat. Mechanical modulation of stem cell proliferation and differentiation indicates a unique therapeutic target to aid in tissue regeneration and repair and may represent the basis of a nonpharmacologic strategy to simultaneously prevent obesity and osteoporosis.
Al/Si and Ca/Eu short range order in Ca/Eu-bicchulite, studied by FTIR spectroscopy
Authors: Rahmoun Nouri-Said , Peters Lars , Knorr Karsten , Depmeier Wulf 
Published: August 2008

Abstract
Powder FTIR spectra of the solid solution series |(Ca2 – xEux)4(OH)8|[(Al2 + xSi1 – x)4O24]-SOD, 0 ≤ x ≤ 1, were taken at room temperature. All members, including the mineral bicchulite, |Ca8(OH)8|[Al8Si4O24]-SOD, have a sodalite-type structure. Spectra taken in the hydroxyl region (4000 − 3000 cm−1) yield information related to the local structural states of the pseudo-cubane-like (Ca2 + x
Eu2 – x
)(OH)4-clusters, 0 ≤ x ≤ 2. Three different patterns of short range order could be identified. Depending on x, different concentrations of Ca4(OH)4, EuCa3(OH)4, and Eu2Ca2(OH)4 clusters are found, whereas Eu3Ca(OH)4 or Eu4(OH)4 clusters are not observed. Hence, short range order is maintained such that each SOD cage of an all-alumina framework contains two Ca and two Eu per cluster. The positions of the framework stretching and bending modes shift linearly towards lower wavenumbers with increasing Al content. The shifts are correlated with changes of the framework geometry. Furthermore, Alrich samples show splitting of the stretching and bending modes. This is interpreted as the change of the local environment of Al due to the substitution of Eu3+ for Ca2+. With the use of deuteration experiments a more detailed assignment could be achieved, especially for the M—OH absorption bands. Finally, changes in the line shape, resulting from cation ordering, are studied by autocorrelation analysis. In particular, samples of intermediate composition show large broadening parameters, Δ
corr
, suggesting high degrees of local structural heterogeneity.
New thallium diphosphates Tl2
Me(H2P2O7)2 · 2 H2O, Me = Mg, Mn, Co, Ni and Zn. Synthesis, single crystal X-ray structures and powder X-ray structure of the Mg phase
Authors: El Bali Brahim , Capitelli Francesco , Alaoui Aziz Tahiri , Lachkar Mohammed , da Silva Iván , Alvarez-Larena Angel , Piniella Juan F. 
Published: August 2008

Abstract
Crystals of thallium dihydrogendiphosphate Tl2
Me(H2P2O7)2 · 2 H2O (Me = Mg (1), Mn (2), Co (3), Ni (4) and Zn (5)), have been synthesized and analyzed by powder X-ray diffractometry (Mg phase) and single crystal X-ray diffractometry (other phases). They resulted to be isostructural within triclinic group P-1, with the following unit-cell parameters: a = 6.9620(1), b = 7.3635(1), c = 7.7713(1) Å, α = 81.8014(5), β = 70.8597(6), γ = 86.1373(7)°, V = 372.44(8) Å3
(1); a = 6.9577(6), b = 7.4745(6), c = 7.8248(7) Å, α = 80.723(2), β = 71.912(1), γ = 85.661(1)°, V = 381.62(6) Å3
(2); a = 6.9767(7), b = 7.3634(7), c = 7.7690(7) Å, α = 81.421(2), β = 71.114(2), γ = 86.424(2)°, V = 373.36(6) Å3
(3); a = 6.9658(7), b = 7.3079(7), c = 7.7016(7) Å, α = 81.801(2), β = 71.185(2), γ = 86.528(2)°, V = 367.27(6) Å3
(4) and a = 6.9628(7), b = 7.3625(7), c = 7.7401(8) Å, α = 81.590(2), β = 71.441(2), γ = 86.323(2)°, V = 372.04(6) Å3
(5).

Me is octahedrally coordinated by two water molecules and four oxygen atoms belonging to two different diphos phate groups. Thallium cations make up interactions with oxygen atoms within Van der Waals coordination sphere, making up irregular coordination polyhedra. The framework of the present compounds can be described as a three-dimensional framework made from vertex-sharing polyhedra. The basic unit is the [Me(H2P2O7)2 · 2 H2O] moiety, which displays a crystallographic Ci symmetry, with the Me cation on the inversion centre. Such units are held together by an intricate scheme of Tl…O interactions; hydrogen bonds complete the network.
The crystal structure of “bis(trimethyltin)-1,3,4-thiadiazole-2,5-dithiolate” – different bonding of the two trimethyltin groups
Authors: Engel Günther , Mattern Günter 
Published: August 2008

Abstract
[(CH3)3Sn]2S2(C2N2S) is monoclinic, space group P21
/c, a = 10.492(5), b = 12.257(6), c = 12.691(6) Å, β
= 95.86(1)°. The zigzag chain structure of the coordination polymer can be derived by the structure correlation method. The starting point is a monomolecular symmetric bis(trimethyltin)-1,3,4-thiadiazole-2,5-dithiolate (Me3SnS)2 (C2N2S): The first of the Me3SnS moieties, bound to the atom C5 of the heterocyclus, remains tetrahedral, whereas the other, bound to C2, is transformed through the N3 atom of the neighbouring ring to a trigonal bipyramid S···(Me3Sn)···N. The three C atoms and the Sn atom of this Me3Sn group are nearly coplanar and form the equatorial plane. With the N3 atom of the starting molecule, an equivalent linking to the other neighbour takes place. The resultant plane ribbons run parallel to the crystallographic b-axis. The analysis of the bond distances and angles reveals that the regular trigonal bipyramid almost exactly represents the transition state along a chemical reaction pathway for a nucleophilic SN2 displacement at tetrahedrally coordinated tin.
Crystal and molecular structures of three 2-substituted 4-methyloxan-4-ol derivatives studied by X-ray crystallography and by PM6 calculations
Authors: Zukerman-Schpector Julio , Dos Santos Alcindo A. , Macedo Alexandra , Wendler Edison P. , Brito Gilmar A. , Tiekink Edward R. T. 
Published: August 2008

Abstract
The conformational features of three 2-substituted 4-methyloxan-4-ol (tetrahydropyran) derivatives were investigated by single crystal X-ray crystallographic studies and the geometries were optimized using semi-empirical PM6 methods. The tetrahydropyran ring in each of (I)–(III) adopts a chair conformation with their hydroxyl groups occupying equatorial, axial and axial positions, respectively. The strongest hydrogen bonding interactions apparent in each of the respective crystal structures, as judged from distance and angle considerations, involve the ring-bound O2-hydroxyl group and tetrahydropyran ring oxygen atom. These hydrogen bonds lead to a supramolecular chain with a linear topology in each case but generated by glide symmetry in (I) and (II), and 21-screw symmetry in (III). In the latter, a two dimensional array constructed by O—H…O bonding is found leading to undulating layers. Despite the absence of additional O—H…O hydrogen bonding sites, two dimensional arrays are also generated in each of (I) and (II), but this time mediated by C—H…O contacts that lead to flat layers. The theoretical structures for each of (I) and (III) differ from their respective experimental structures in terms of the relative orientation of the aromatic substituent. By contrast, for (II), there is close agreement between the experimental and theoretical structures. (I) C12H16O2, monoclinic, Cc, a = 18.7887(8), b = 6.0634(2), c = 10.4178(4) Å, β = 116.945(7)°, V = 1057.99(10) Å3, Z = 4, R
1 = 0.029; (II) C13H18O3, orthorhombic Pc21n, a = 9.3664(17), b = 10.0472(18), c = 12.240(2) Å, V = 1151.9(3) Å3, Z = 4, R
1 = 0.037; (III) C13H18O4, orthorhombic P212121, a = 9.814(3), b = 9.966(2), c = 11.845(2) Å; V = 1158.5(5) Å3, Z = 4, R
1 = 0.079.
A comparative study of crystal structure of a Cu(II) dicyanamide compound determined independently from X-ray powder- and single-crystal analyses
Authors: Chakraborty Santu , Ghosh Soumen , Mal Dasarath , Koner Subratanath , Mukherjee Alok Kamur 
Published: August 2008

Abstract
The dicyanamido diethelenetriamine copper (II) compound, C8H13CuN9 (I), has been synthesized, and structurally characterized independently using X-ray powder- and single-crystal diffraction data. The direct methods program package EXPO-2004 has been used for structure solution from laboratory powder diffraction data. Intermolecular N—H···N hydrogen bonds in (I) generate R2
2(16) rings, which are fused forming molecular columns propagating along the [100] direction. Further linking of parallel columns through N—H···N hydrogen bonds results into a three-dimensional supramolecular network.
Hypocortisolemic clamp unmasks jointly feedforward- and feedback-dependent control of overnight ACTH secretion
Authors: Iranmanesh Ali , Veldhuis Johannes D 
Published: August 2008

BackgroundACTH secretion is under hypothalamic stimulatory (feedforward) and adrenal inhibitory (feedback) control.HypothesisAssessment of overnight ACTH secretion during a hypocortisolemic clamp will permit the estimation of changing feedforward and feedback.SubjectsSeven healthy men.InterventionsAn oral dose of placebo (PLAC), metyrapone (METY, 3 g), or ketoconazole (KTCZ, 1.2 g) was given at midnight (MN) to block glucocorticoid synthesis. Plasma ACTH was sampled every 10 min (MN to 0800 h).AnalysisVariable-waveform deconvolution analysis of ACTH secretion and approximate entropy (ApEn) analysis of pattern regularity.ResultsCompared with PLAC, administration of METY and KTCZ reduced morning cortisol concentrations by ≥77 and 54% respectively (P<0.001). Hypocortisolemia elevated pulsatile ACTH secretion by 8.2- (METY) and 5.3-fold (KTCZ; both P<0.001). Basal ACTH secretion rose by 3.4-fold under METY-induced cortisol depletion (P=0.020). ACTH secretory-burst shape and half-life were stable. ApEn of ACTH release declined overnight (P=0.021) and with the drug (P=0.001), denoting enhanced feedforward coordination.ConclusionThe combined data predict overnight amplification and coordination of hypothalamic feedforward drive onto ACTH release. Therefore, disruption of either mechanism might contribute to clinical pathophysiology, such as late-day elevations of cortisol output in fasting, alcoholism, depression, or aging.
The Texture of Acidized Fracture Surfaces: Implications for Acid Fracture Conductivity
Authors: Malagon C. , Pournik M. , Hill A. D. 
Published: August 2008

Summary
In an acid-fracturing treatment, fracture conductivity is created by differential etching of the fracture surface by the acid; without nonuniform dissolution along the fracture face, the fracture will close after pumping ceases, and little lasting conductivity will be created. Despite this critical role of differential etching in the creation of fracture conductivity, little is known about the texture of the fracture surface created during acid fracturing or about the dependence of this texture on the acidizing conditions. To study this important aspect of the acid-fracturing process, we developed a new surface profilometer to measure the surface profile of a rock sample accurately and rapidly and used the instrument to characterize fracture surfaces after acidizing.
The profilometer measures the distance to the rock surface with a laser device that measures distance with an accuracy of 0.001 in. The rock sample is mounted on a servo-table that automatically moves the sample in selectable increments (typically, 0.025 in.). With this device, the surface of a standard API fracture-conductivity sample can be scanned in a few hours, and a digitized profile image can be obtained. This digital image is used to characterize the etched surface topography quantitatively.
We have measured the etched-fracture-surface profile for a wide range of acidizing conditions. The etched-surface characteristics depend strongly on the acidizing conditions, including acid type and strength, velocity in the fracture, leakoff rate, and rock type. Results for typical acid-fracturing fluids and conditions are presented along with recommendations for fluid systems that create the smallest-scale differential etching.
Application of Relative Permeability Modifiers To Control Water Cut Following Hydraulic Fracturing in Western Siberia Oilfields—Russian Case-History Study
Authors: Borodin E. G. , Vakhoureshev P. E. , Stolyarov S. M. , Kalfayan L. J. 
Published: August 2008

Summary
Because of the geological characteristics and low permeability of Western Siberia hydrocarbon reservoirs, hydraulic fracturing is the most effective method for improving hydrocarbon production. During recent years, the massive fracturing treatments in this area have led to a reduction of well candidates for this type of production-enhancement technique. Currently, the majority of selected wells for fracture stimulation are considered risky because of significant water cut increase after stimulation. The question arises: How to reduce water production while enhancing oil production?
This paper reviews 26 case histories exemplifying the use of relatively permeability modifiers (RPMs) in hydraulic fracturing to enhance oil recovery and control water production. Also, results of laboratory studies are included to support the RPM-fracturing concept and -placement techniques.