bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pulsed electromagnetic field stimulation of bone marrow cells derived from ovariectomized rats affects osteoclast formation and local factor production
Authors: Chang Kyle , Hong‐Shong Chang Walter , Yu Yen‐Hsin , Shih Chung 
Published: January 2004

AbstractThis study examined the effects of a specific pulsed electromagnetic field (PEMF) stimulation on osteoclast formation in bone marrow cells from ovariectomized rats and to determine if the signal modulates the production of cytokines associated with osteoclast formation. Adult female Wistar rats were subjected to bilateral or sham ovariectomy, and primary bone marrow cells were harvested at 4 days (Subgroup I) and 7 days (Subgroup II) after surgery. Primary bone marrow cells were subsequently placed in chamber slides and set inside solenoids powered by a pulse generator (300 μs, 7.5 Hz) for 1 h per day for 9 days (OVX + PEMF group). Others (INT, SHAM, and OVX groups) were cultured under identical conditions, but no signal was applied. Recruitment and authentication of osteoclast‐like cells were evaluated by determining multinuclear, tartrate‐resistant acid phosphatase (TRAP) positive cells on day 10 of culture and by pit formation assay, respectively. The PEMF signal caused significant reductions in osteoclast formation in both Subgroups I (−55%) and II (−43%). Tumor necrosis factor‐α (TNF‐α), interleukin 1β (IL‐1β), and interleukin 6 (IL‐6) in OVX + PEMF group of Subgroup I were significantly reduced at 5, 7, and 9 days as compared to OVX group. The results found in this study suggest that osteoclastogenesis can be inhibited by PEMF stimulation, putatively due to a concomitant decrease in local factor production. Bioelectromagnetics 25:134–141, 2004. © 2004 Wiley‐Liss, Inc.
Geomagnetic field effect on cardiovascular regulation
Authors: Gmitrov Juraj , Gmitrova Anna 
Published: January 2004

AbstractThe goal of the present research was try to explain the physiological mechanism for the influence of the geomagnetic field (GMF) disturbance, reflected by the indices of the geomagnetic activity (K, Kp, Ak, and Ap indices), on cardiovascular regulation. One hundred forty three experimental runs (one daily) comprising 50 min hemodynamic monitoring sequences were carried out in rabbits sedated by pentobarbital infusion (5 mg/kg/h). We examined the arterial baroreflex effects on the short term blood pressure and heart rate (HR) variabilities reflected by the standard deviation (SD) of the average values of the mean femoral arterial blood pressure (MAP) and the HR. Baroreflex sensitivity (BRS) was estimated from blood pressure/HR response to intravenous (i.v.) bolus injections of vasoconstrictor (phenylephrine) and vasodilator (nitroprusside) drugs. We found a significant negative correlation of increasing GMF disturbance (Kp) with BRS (P = 0.008), HR SD (P =0.022), and MAP SD (P = 0.002) signifying the involvement of the arterial baroreflex mechanism. The abrupt change in geomagnetic disturbance from low (K = 0) to high (K = 4–5) values was associated with a significant increase in MAP (83 ± 5 vs. 99 ± 5 mm Hg, P = 0.045) and myocardial oxygen consumption, measured by MAP and HR product (24100 ± 1800 vs. 31000 ± 2500 mm Hg · bpm, P = 0.034), comprising an additional cardiovascular risk. Most likely, GMF affects brainstem and higher neural cardiovascular regulatory centers modulating blood pressure and HR variabilities associated with the arterial baroreflex. Bioelectromagnetics 25:92–101, 2004. © 2004 Wiley‐Liss, Inc.
Mobile phones and children: Is precaution warranted?
Authors: van Rongen Eric , Roubos Eric W. , van Aernsbergen Lodewijk M. , Brussaard Gert , Havenaar Johan , Koops Frans B.J. , van Leeuwen Floor E. , Leonhard Helmut K. , van Rhoon Gerard C. , Swaen Gerard M.H. , van de Weerdt Rik H.J. , Zwamborn A. Peter M. 
Published: January 2004

AbstractAre there health related arguments to recommend that children limit their use of mobile telephones? The International Expert Group on Mobile Phones from the UK concluded so, but did not come up with convincing scientific data to back this statement. The Health Council of the Netherlands approached the problem by considering whether developmental arguments might be found, i.e., asking if there reason to believe that the heads of children are more susceptible to the electromagnetic fields emitted by mobile telephones than those of adults. It concluded that no major changes in head development occur after the second year of life that might point at a difference in electromagnetic susceptibility between children and adults. The Health Council therefore sees no reason to recommend limiting the use of mobile phones by children. Bioelectromagnetics 25:142–144, 2004. © 2004 Wiley‐Liss, Inc.
High Oxidation State Organometallic Chemistry in Aqueous Media: New Opportunities for Catalysis and Electrocatalysis
Authors: Poli Rinaldo 
Published: January 2004

AbstractMolybdenum has been used as a case study for the rational development of a new domain of organometallic chemistry, combining oxo‐stabilized high oxidation state metals and aqueous media. The pH‐dependent conversion of oxo, hydroxo, and aqua ligands allows the opening of free coordination sites, while the use of a redox active metal opens possible pathways for coupled proton and electron transfer to and from activated substrates. While our work has so far only concentrated on synthesis and analytical investigations, the development of catalytic and electrocatalytic processes in water or aqueous media is a promising application of this new research area.
Enthalpy of Solution of 1,4‐Naphthoquinone in CO2 + n‐Pentane in the Critical Region of the Binary Mixture: Mechanism of Solubility Enhancement
Authors: Mu Tiancheng , Zhang Xiaogang , Liu Zhimin , Han Buxing , Li Zhonghao , Jiang Tao , He Jun , Yang Guanying 
Published: January 2004

AbstractThe enthalpy of solution (ΔsolvHm) and solubility of 1,4‐naphthoquinone in CO2 + n‐pentane were measured at 308.15 K in the critical region of the binary fluid. In order to study the effect of phase behavior of the mixed solvent on ΔsolvHm, the experiments were carried out in the supercritical (SC) and subcritical region of the binary solvent. The density of the mixed solvent in different conditions was determined. The isothermal compressibility (KT) of the mixed solvent, and the partial molar volume (Vn‐pentane) of n‐pentane in the solution were calculated. It was demonstrated that the ΔsolvHm was negative in all conditions. ΔsolvHm is nearly independent of pressure or density in all the solvents in a high‐density region, in which compressibility of the solvent is very small; this indicates that the intermolecular interaction between the solvent and the solute is similar to that for liquid solutions. It is very interesting that ΔsolvHm in the mixed SC fluid differs from the ΔsolvHm in mixed subcritical fluids. The absolute value of ΔsolvHm in the mixed SC fluid is close to that in pure SC CO2 in the high‐density region, and is much lower than that in pure SC CO2 in the low‐density region. In the mixed subcritical fluids, the ΔsolvHm is also close to that in the pure CO2 in the high‐density region. However, at the same density, the absolute value of ΔsolvHm in the binary subcritical fluid is larger than that in pure CO2 in the high‐compressible region of the mixed solvent. The main reason for this is that the degree of clustering in the SC solutions is small at the density in which the degree of clustering is large in the subcritical solutions. It can be concluded that solubility enhancement by n‐pentane in the mixed SC fluid is entropy driven. In contrast, the solubility enhancement by n‐pentane in subcritical fluids is enthalpy driven. The intermolecular interaction in the SC solutions and subcritical solutions can be significantly different even if their densities are the same.
Sol–Gel Polycondensation of Tetraethyl Orthosilicate (TEOS) in Sugar‐Based Porphyrin Organogels: Inorganic Conversion of a Sugar‐Directed Porphyrinic Fiber Library through Sol–Gel Transcription Processes
Authors: Kawano Shin‐ichiro , Tamaru Shun‐ichi , Fujita Norifumi , Shinkai Seiji 
Published: January 2004

AbstractSugar‐appended porphyrins (1 a–e) with monosaccharide groups at their periphery have been rationally designed for a new class of gelating reagents. A few of these compounds have the tendancy to form one‐dimensional aggregates stable enough to show successful gelation ability for DMF–alcohol mixed solvents. The aggregation mode in the specific columnar super structures has been evaluated in detail by UV‐visible spectrometry (UV/Vis), circular dichroism (CD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). All UV‐visible spectra of sugar‐appended porphyrinic gels obtained from 1 a–c exhibit Soret band absorptions, which shift to lower wavelength and are significantly broadened. This phenomenon indicates that these porphyrin cores strongly interact with each other in an H‐aggregate fashion, which drives the generation of a one‐dimensional porphyrin‐stacking array. The CD spectra of the organogels from 1 a and 1 b, which are in anomers, exhibit an almost symmetric pattern, whereas the gel from 1 c gives a completely different pattern. This implies that the gel fibrils wind themselves in a right‐ or left‐handed fashion; this reflects chirality in the specific molecular structure of the gelators. The results from SEM for the gel fibrils are in good agreement with the CD patterns. The gel fibrils in 1 a possess left‐handed helicity, whereas those in 1 b wind themselves right‐handedly. Macroscopic helical morphology reflects the microscopic structure well at a molecular level, which gives structural variety of the gel fibrils, which can be defined by the sugar library. Inorganic conversion of the organic helical fibrils by a sol–gel transcription process successfully gives the helical‐silica structures, which finely inherit the organic morphology. A striking observation is that a unimolecular porphyrin‐stacking array is also transcribed into silica fibers when the optimized sol–gel reaction conditions are selected. A sugar‐based organic‐fiber library in porphyrinic gels thus provides a variety of inorganic materials through the sol–gel transcription process.
Chemical Tailoring of Porous Silica Xerogels: Local Structure by Vibrational Spectroscopy
Authors: Fidalgo Alexandra , Ilharco Laura M. 
Published: January 2004

AbstractMonolithic porous silica xerogels were synthesized by the sol–gel process, and their local structure was analysed by vibrational spectroscopy. The silica alcogels were prepared by a two‐step hydrolytic polycondensation of tetraethoxysilane (TEOS) in isopropanol, with a water/TEOS molar ratio of 4. The hydrolysis step was catalysed by hydrochloric acid (HCl), with different HCl/TEOS molar ratios (ranging from 0.0005 to 0.009), and the condensation step was catalysed by ammonia (NH3), with different NH3/HCl molar ratios (ranging from 0.7 to 1.7). After appropriate ageing, the alcogels were washed with isopropanol and subcritically dried at atmospheric pressure. The diffuse reflectance infrared Fourier transform (DRIFT) spectra were analysed in terms of the main siloxane rings that form the silica particles, taking into account the splitting of the νasSiOSi mode into pairs of longitudinal and transverse optic components, by long‐range Coulomb interactions. It was proven that the proportion of residual silanol groups (which correlates with hydrophilicity), and the fraction of siloxane 6‐rings (which correlates with porosity) may be tailored by adequate catalytic conditions, mostly by the hydrolysis pH. This was explained in terms of the reactions' mechanisms taking place in the two‐step sol–gel process followed.
Stereocontrolled Synthesis of 8,11‐Dideoxytetrodotoxin, An Unnatural Analogue of Puffer Fish Toxin
Authors: Nishikawa Toshio , Urabe Daisuke , Yoshida Kazumasa , Iwabuchi Tomoko , Asai Masanori , Isobe Minoru 
Published: January 2004

Abstract8,11‐Dideoxytetrodotoxin, an unnatural tetrodotoxin analogue, was synthesized in a highly stereoselective manner from a common intermediate from our synthetic studies on tetrodotoxin. The key features in the synthesis were as follows: neighboring group participation of a trichloroacetamide to allow regioselective and stereoselective hydroxylation, protection of a δ‐hydroxylactone as an ortho ester, and guanidine installation through the use of Boc‐protected isothiourea. Global deprotection of the fully protected intermediate under acidic conditions gave 8,11‐dideoxytetrodotoxin, which exhibited very weak biological activities.
Photohydroxylation of 1,4‐Benzoquinone in Aqueous Solution Revisited
Authors: von Sonntag Justus , Mvula Eino , Hildenbrand Knut , von Sonntag Clemens 
Published: January 2004

AbstractIn water, photolysis of 1,4‐benzoquinone,Qgives rise to equal amounts of 2‐hydroxy‐1,4‐benzoquinoneHOQand hydroquinoneQH2which are formed with a quantum yield ofΦ=0.42, independent of pH andQconcentration. By contrast, the rate of decay of the triplet (λmax=282 and ∼410 nm) which is the precursor of these products increases nonlinearly (k=(2→3.8)×106s−1) with increasingQconcentration ((0.2→10) mM). The free‐radical yield detected by laser flash photolysis after the decay of the triplet also increases with increasingQconcentration but follows a different functional form. These observations are explained by a rapid equilibrium of a monomeric tripletQ*and an exciplexQ2*(K=5500±1000 M−1). WhileQ*adds water and subsequent enolizes into 1,2,4‐trihydroxybenzenePh(OH)3,Q2*decays by electron transfer and water addition yielding benzosemiquinone.QHand.OH adduct radicals.QOH. The latter enolizes to the 2‐hydroxy‐1,4‐semiquinone radical.Q(OH)Hwithin the time scale of the triplet decay and is subsequently rapidly (microsecond time scale) oxidized byQtoHOQwith the concomitant formation of.QH. On the post‐millisecond time scale, that is, when.QHhas decayed,Ph(OH)3is oxidized byQyieldingHOQandQH2as followed by laser flash photolysis with diode array detection. The rate of this pH‐ andQconcentration‐dependent reaction was independently determined by stopped‐flow. This shows that there are two pathways to photohydroxylation; a free‐radical pathway at high and a non‐radical one at lowQconcentration. In agreement with this, the yield ofPh(OH)3is most pronounced at lowQconcentration. In the presence of phosphate buffer,Q*reacts with H2PO4−giving rise to an adduct which is subsequently oxidized byQto 2‐phosphato‐1,4‐benzoquinoneQP. The current view that.OH is an intermediate in the photohydroxylation ofQhas been overturned. This view had been based on the observation of the.OH adduct of DMPO whenQis photolyzed in the presence of this spin trap. It is now shown thatQ*/Q2*oxidizes DMPO (k≈1×108 M−1 s−1) to its radical cation which subsequently reacts with water.Q*/Q2*react with alcohols by H abstraction (rates in units ofM−1 s−1): methanol (4.2×107), ethanol (6.7×107), 2‐propanol (13×107) and tertiary butyl alcohol (∼0.2×107). DMSO (2.7×109) and O2(∼2×109) act as physical quenchers.
Synthesis of Scroll‐Type Composite Microtubes of Mo2C/MoCO by Controlled Pyrolysis of Mo(CO)6
Authors: Li Xiao‐Lin , Li Ya‐Dong 
Published: January 2004

AbstractComposite microtubes of Mo2C/MoCO have been synthesized for the first time under well‐controlled conditions by thermal decomposition of Mo(CO)6 at about 600 °C. Here, thermal stability and phase transition of the products, as well as the influence of reaction temperature and argon flow rate, have been carefully investigated. All samples were characterized by X‐ray powder diffraction (XRD), scanning electron microscopy (SEM), and X‐ray photoelectron spectroscopy (XPS). The reaction model and rolling mechanism were proposed on the basis of the experimental facts.
Solid‐Phase Synthesis of 89 Polyamine‐Based Cationic Lipids for DNA Delivery to Mammalian Cells
Authors: Yingyongnarongkul Boon‐ek , Howarth Mark , Elliott Tim , Bradley Mark 
Published: January 2004

AbstractThe ability of non‐viral gene delivery systems to overcome extracellular and intracellular barriers is a critical issue for future clinical applications of gene therapy. In recent years much effort has been focused on the development of a variety of DNA carriers, and cationic liposomes have become the most common non‐viral gene delivery system. Solid‐phase synthesis was used to produce three libraries of polyamine‐based cationic lipids with diverse hydrophobic tails. These were characterised, and structure‐activity relationships were determined for DNA binding and transfection ability of these compounds when formulated as cationic liposomes. Two of the cationic lipids produced high‐efficiency transfection of human cells. Surprisingly, these two compounds were from the library with two headgroups and one aliphatic tail, a compound class regarded as detergent‐like and little investigated for transfection. These cationic lipids are promising reagents for gene delivery and illustrate the potential of solid‐phase synthesis methods for lipoplex discovery.
Effects of Metal Ions on Photoinduced Electron Transfer in Zinc Porphyrin–Naphthalenediimide Linked Systems
Authors: Okamoto Ken , Mori Yukie , Yamada Hiroko , Imahori Hiroshi , Fukuzumi Shunichi 
Published: January 2004

AbstractZinc porphyrin–naphthalenediimide (ZnP–NIm) dyads and zinc porphyrin–pyromellitdiimide–naphthalenediimide (ZnP–Im–NIm) triad have been employed to examine the effects of metal ions on photoinduced charge‐separation (CS) and charge‐recombination (CR) processes in the presence of metal ions (scandium triflate (Sc(OTf)3) or lutetium triflate (Lu(OTf)3), both of which can bind with the radical anion of NIm). Formation of the charge‐separated states in the absence and in the presence of Sc3+ was confirmed by the appearance of absorption bands due to ZnP.+ and NIm.− in the absence of metal ions and of those due to ZnP.+ and the NIm.−/Sc3+ complex in the presence of Sc3+ in the time‐resolved transient absorption spectra of dyads and triad. The lifetimes of the charge‐separated states in the presence of 1.0×10−3 M Sc3+ (14 μs for ZnP–NIm, 8.3 μs for ZnP–Im–NIm) are more than ten times longer than those in the absence of metal ions (1.3 μs for ZnP–NIm, 0.33 μs for ZnP–Im–NIm). In contrast, the rate constants of the CS step determined by the fluorescence lifetime measurements are the same, irrespective of the presence or absence of metal ions. This indicates that photoinduced electron transfer from 1ZnP* to NIm in the presence of Sc3+ occurs without involvement of the metal ion to produce ZnP.+–NIm.−, followed by complexation with Sc3+ to afford the ZnP.+–NIm.−/Sc3+ complex. The one‐electron reduction potential (Ered) of the NIm moiety in the presence of a metal ion is shifted in a positive direction with increasing metal ion concentration, obeying the Nernst equation, whereas the one‐electron oxidation potential of the ZnP moiety remains the same. The driving force dependence of the observed rate constants (kET) of CS and CR processes in the absence and in the presence of metal ions is well evaluated in terms of the Marcus theory of electron transfer. In the presence of metal ions, the driving force of the CS process is the same as that in the absence of metal ions, whereas the driving force of the CR process decreases with increasing metal ion concentration. The reorganization energy of the CR process also decreases with increasing metal ion concentration, when the CR rate constant becomes independent of the metal ion concentration.
Stabilization of p‐Block Organoelement Terminal Hydroxides, Thiols, and Selenols Requires Newer Synthetic Strategies
Authors: Roesky Herbert W. , Murugavel Ramaswamy , Walawalkar Mrinalini G. 
Published: January 2004

AbstractMetal hydroxides represent a very interesting and highly useful class of compounds that have been known to chemists for a very long time. While alkali and alkaline earth metal hydroxides (s‐block) are commonplace chemicals in terms of their abundance and their use in a chemical laboratory as bases, the interest in Brønsted acidic molecular terminal hydroxides of p‐block elements, such as aluminum and silicon, has been of recent origin, with respect to the variety of applications these compounds can offer both in materials science and catalysis. Moreover, these systems are environmentally friendly, relative to the metal halides, owing to their ‐OH functionality (resembling that of water). Design and conceptualization of the corresponding terminal thiols, selenols, and tellurols (MSH, MSeH, and MTeH) offer even more challenging problems to synthetic inorganic chemists. This concept summarizes some of the recent strategies developed to stabilize these otherwise very unstable species. The successful preparation of a number of silicon trihydroxides a few years back resulted in the generation of several model compounds for metal–silicates. The recent synthesis of unusual aluminum compounds such as RAl(OH)2, RAl(SH)2, and RAl(SeH)2 with terminal EH (E=O, Se, or Se) groups is likely to change the ways in which some of the well‐known catalytic conversions are being carried out. The need for very flexible and innovative synthetic strategies to achieve these unusual compounds is emphasized in this concept.
Benzofuran Trimers for Organic Electroluminescence
Authors: Anderson Sally , Taylor Peter N. , Verschoor Geraldine L. B. 
Published: January 2004

AbstractFour linear benzofuran trimers have been prepared by a two‐stage synthetic procedure. They were tested as materials for organic electroluminescence (OEL). Precursor phenylene ethynylene oligomers were formed in the first stage, then after removal of the phenolic hydroxyl protecting groups, a base was used to promote the cyclization of ortho‐hydroxy phenylene ethynylenes to benzofurans. Both acetate esters and tert‐butyl carbonates were employed as protecting groups. tert‐Butyl and n‐hexyl substituents on the benzofurans were used to modulate solubility, aggregation, and film‐forming properties; two tert‐butyl groups prevented aggregation in the solid state, thus maintaining emission in the blue region of the visible spectrum. The OEL characteristics of the tert‐butyl‐substituted benzofuran trimer were explored, and blue emission was observed. The two‐stage synthetic procedure employed for the preparation of these benzofuran trimers may be applied to a wide variety of benzofuran oligomer and polymer targets.