bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase diagrams of the kinetic metamagnetic spin‐3/2 Blume–Capel model in an oscillating external field
Authors: Keskin M. , Canko O. , Kırak M. 
Published: July 2007

AbstractDynamic phase diagrams are calculated, within a mean‐field approach, for the kinetic metamagnetic spin‐3/2 Blume–Capel model in the presence of a time‐dependent oscillating external magnetic field using Glauber‐type stochastic dynamics and six fundamental types of phase diagrams are found in the reduced temperature (T) and magnetic‐field amplitude parameter (h) plane. The phase diagrams exhibit one, two or three dynamic tricritical points, and besides the paramagnetic (P), the antiferromagnetic‐3/2 (AF3/2), the antiferromagnetic‐1/2 (AF1/2) phases, three coexistence phase regions, namely AF3/2 + P, AF1/2 + P, AF3/2 + AF1/2, exist depending upon the interaction parameters. The dynamic phase boundaries between the P and AF3/2 phases are always second‐order lines, but between the P and AF1/2 phases are second‐ or/and first‐order lines. All other dynamic phase boundaries among the disordered, ordered phases and coexistence phase regions are first‐order lines. We have investigated the influence of the crystal field interaction (D) and we obtain five different phase diagram topologies in (d, T) plane, d = D /𝒥′ We have also studied the influence of the frequency on the phase boundaries as well as the dynamic tricritical point and found that the topologies of the phase diagrams slightly change. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical absorption spectra of Fe2+ and Fe3+ in beryl crystals
Authors: Spinolo G. , Fontana I. , Galli A. 
Published: July 2007

AbstractA variety of beryls, inclusive of blue aquamarine, heliodor and goshenite, spanning an iron concentration range of more than one order of magnitude, has been studied by absorption spectroscopy down to 16 K and in the energy range 3000–50000 cm–1. The weak spin‐forbidden transitions of Fe2+ as well as the allowed charge‐transfer transitions, ligand‐to‐metal, mainly due to Fe3+, have been observed for the first time in these diluted systems. The comparison with reference spectra of aqueous solutions containing Fe2+ and Fe3+ allowed to reach, by the aid of d6 (Fe2+) and d5 (Fe3+) Tanabe‐Sugano diagrams for octahedral symmetry, a satisfactory interpretation of the spectra. The colour centres absorption, their thermal instability and contribution to the colour of these crystals has also been considered. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical absorption spectra of Fe2+ and Fe3+ in aqueous solutions and hydrated crystals
Authors: Fontana I. , Lauria A. , Spinolo G. 
Published: July 2007

AbstractAbsorption spectra of aqueous solutions containing Fe2+ and Fe3+ ions and hydrated crystals are studied up to 50000 cm–1. Charge‐transfer transitions for both hydrated ions are here measured for the first time. The weak Fe2+ spin‐forbidden transitions which up to now have received little attention in diluted systems, are put in evidence: as a consequence, we have proposed for the lower energy transitions different attributions respect to the commonly accepted ones. It is further shown that the step by step oxidation process of Fe2+ to Fe3+, starting from Fe(BF4)2 solution, allows us to quantitatively correlate the oscillator strength of the various spin‐allowed, spin‐forbidden and charge‐transfer transitions of both ions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tuning of electron transport through molecular bridge systems: A study of shot noise
Authors: Maiti Santanu K. 
Published: July 2007

AbstractWe study electron transport characteristics through a single phenalenyl molecule attached with two nonsuperconducting electrodes by the use of Green's function technique. Parametric calculations are given based on the tight‐binding model to characterize the electron transport through such molecular bridge system. It is observed that the electron transport properties are significantly influenced by (a) the interference effect and (b) the molecule‐to‐electrodes coupling strength. In this context we also describe the noise power of the current fluctuations that provides an important information about the electron correlation, which is obtained by calculating the Fano factor (F). The knowledge of this current fluctuations gives a key idea for fabrication of efficient molecular devices. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Lattice vacancy effects on electron transport in multiterminal graphene nanodevices
Authors: Jayasekera Thushari , Mintmire J. W. 
Published: July 2007

AbstractWe investigate the effect of single lattice vacancies on the electron transport of graphene nanoribbon devices using the Landauer formalism within a tight binding approach. For a zigzag nanoribbon, a single lattice vacancy creates conductance dips in the low energy region, due to quasi bound states around the vacancy site. The energy of the bound state is related to the position of the lattice vacancy relative to the edge of the ribbon. We carried out calculations of electron transport properties in a T‐junction device with lattice vacancies. We find that the effect of the vacancies depends on how energetically favorable the lattice vacancy is, which can be studied in terms of the alternate atomic structure of the graphene lattice. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Simulated structure and energetics of endohedral complexes of noble gas atoms in buckminsterfullerene
Authors: Albert Victor V. , Sabin John R. , Harris Frank E. 
Published: July 2007

AbstractClassical molecular dynamics simulations were run for noble gas atoms confined within a buckminsterfullerene cage. The simulations indicated that all the endohedral complexes X@C60 (X = He, Ne, Ar, Kr, Xe) were stable relative to C60 + X, with the Ar complex being the most stable. Except for the He complex, the minimum‐energy configuration was with the endoatom at the geometric center of the cage. The minimum‐energy position of the He atom in He@C60 was off‐center in a high‐symmetry direction, but the energy lowering relative to a centered He atom was found to be small relative to the zero‐point energy of the He atom within the cage. The simulations were checked by comparison of static energy computations with the fullerene fixed in its equilibrium geometry as determined alternatively from experimental data and from empty‐fullerene calculations. The small differences between the alternative geometries were sufficient to cause significant quantitative changes in the computed binding energies but, except for predicting Xe@C60 to be unstable, did not fundamentally alter our qualitative description of the results. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Temperature dependence of oxygen isotope acid fractionation for modern and fossil tooth enamels
Authors: Passey Benjamin H. , Cerling Thure E. , Levin Naomi E. 
Published: July 2007

AbstractThe oxygen isotope ratio of CO2 liberated from structural carbonate in tooth enamel apatite was measured at phosphoric acid reaction temperatures of 25°C, 60°C and 90°C, and it was found that apparent acid fractionation factors for pristine enamel, fossilized enamel, and calcite follow different temperature relationships. Using sealed vessel reactions normalized to α25 = 1.01025 (the fractionation factor for calcite at 25°C), the apparent fractionation factor at 90°C (α*90) for pristine enamel ranged between 1.00771 and 1.00820, and between 1.00695 and 1.00772 for fossilized enamel. Apparent fractionation factors for common acid bath reactions are similar to those for sealed vessel reactions. A significant correlation exists between α*90 and F− content, suggesting that change in the acid fractionation factor may be related to the replacement of OH− with F− during fossilization of bioapatite. These results have important implications for making accurate comparisons between modern and fossil tooth enamel δ18O values, and for the uniformity of isotope data produced in different laboratories using different acid reaction temperatures. Copyright © 2007 John Wiley & Sons, Ltd.
Axial focusing following low kinetic energy pulsed extraction from a miniature linear ion trap
Authors: Dobson Gareth S. , Enke Christie G. 
Published: July 2007

AbstractUsing an axial focusing miniature linear ion trap with tubular end cap lenses (MLIT) we have investigated spatial focusing on ion ejection using low kinetic energy pulsed extraction methods. Ion packet widths focused to ca. 1 mm (in both the radial and axial planes) are produced following collisional cooling with helium buffer gas in an MLIT. Small axial and radial packet widths as well as application of DC extraction voltages allow different ion focusing techniques to be used on batch ion extraction. In particular, controlling the position of the space focus plane (commonly used in time‐of‐flight mass spectrometry) following low kinetic energy (∼10 eV) ion ejection from an MLIT through the application of DC extraction voltages is illustrated. Prior to simultaneous ion ejection, induced axial ion oscillation through a change in the DC potential well shape is also shown to be useful for separating and controlling different mass/charge ion packet spatial distributions in the region of an orthogonal time‐of‐flight (o‐TOF) push pulse. Copyright © 2007 John Wiley & Sons, Ltd.
Elucidation of the complex molecular structure of wheat straw lignin polymer by atmospheric pressure photoionization quadrupole time‐of‐flight tandem mass spectrometry
Authors: Banoub Joseph H. , Benjelloun‐Mlayah Bouchra , Ziarelli Fabio , Joly Nicolas , Delmas Michel 
Published: July 2007

AbstractWheat straw lignin was extracted using the novel CIMV procedure which selectively separates the cellulose, hemicelluloses and lignin. Solid‐state 13C NMR experiments using cross polarization/magic angle spinning (CP/MAS) were carried out on the extracted wheat straw lignin and some structural indices were revealed. Atmospheric pressure photoionization mass spectrometry (APPI‐MS) has proven to be a powerful analytical tool capable of ionizing small to large lignin oligomers, which cannot be ionized efficiently by atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI). The APPI mass spectra of the extracted wheat straw lignin were recorded in the positive and negative ion modes. Positive ion mode APPI‐MS indicated the exact presence of 39 specific oligomeric ions. Negative ion APPI‐MS indicated the additional presence of at least 18 specific oligomeric ions. The structural characterization of this novel and complete series of 57 specific related oligomers was achieved by calculating the exact molecular masses measured by high‐resolution quadrupole time‐of‐flight mass spectrometry (QqToF‐MS). Some oligomeric species photoionized in both the positive and negative ion modes to form the respective protonated and deprotonated molecules. Low‐energy collision‐induced dissociation tandem mass spectrometric analyses performed with a QqToF‐MS/MS hybrid instrument provided unique dissociation patterns of the complete series of novel precursor ions. These MS/MS analyses provided diagnostic product ions, which enabled us to determine the exact molecular structures and arrangement of the selected 57 different related ionic species. Copyright © 2007 John Wiley & Sons, Ltd.
Scientific explanations: Characterizing and evaluating the effects of teachers' instructional practices on student learning
Authors: McNeill Katherine L. , Krajcik Joseph 
Published: July 2007

AbstractTeacher practices are essential for supporting students in scientific inquiry practices, such as the construction of scientific explanations. In this study, we examine what instructional practices teachers engage in when they introduce scientific explanation and whether these practices influence students' ability to construct scientific explanations during a middle school chemistry unit. Thirteen teachers enacted a project‐based chemistry unit, How can I make new stuff from old stuff?, with 1197 seventh grade students. We videotaped each teacher's enactment of the focal lesson on scientific explanation and then coded the videotape for four different instructional practices: modeling scientific explanation, making the rationale of scientific explanation explicit, defining scientific explanation, and connecting scientific explanation to everyday explanation. Our results suggest that when teachers introduce scientific explanation, they vary in the practices they engage in as well as the quality of their use of these practices. We also found that teachers' use of instructional practices can influence student learning of scientific explanation and that the effect of these instructional practices depends on the context in terms of what other instructional practices the teacher uses. © 2007 Wiley Periodicals, Inc. J Res Sci Teach 45: 53–78, 2008
Evaluation of distribution and bioavailability of Cr, Mn, Fe, Cu, Zn and Pb in the waters of the upper course of the Lerma River
Authors: Avila‐Pérez P. , Zarazúa G. , Tejeda S. , Barceló‐Quintal I. , Díaz‐Delgado C. , Carreño‐León C. 
Published: July 2007

AbstractDistribution and bioavailability of Cr, Mn, Fe, Cu, Zn, and Pb in the waters of the upper course of the Lerma River (UCLR), Mexico, were evaluated by means total reflection x‐ray fluorescence spectrometry. The surface water samples were collected from eight sites distributed along the flow direction of the river. Four sampling campaigns were carried out in each site during a one‐year period. The water samples were analyzed in triplicate, using a TXRF Spectrometer ‘TX‐2000 Ital Structures’ with a Si(Li) detector and a resolution of 140 eV (FWHM) at Mn Kα. A Mo tube (40 kV, 30 mA) with 17.4 KeV excitation energy was used for a counting time of 500 s. Results show that the concentration ranges of heavy metals in the water are the following: Cr, from < 5 to 56 µg/l; Mn, from 9 to 788 µg/l; Fe, from 98 to 8474 µg/l; Cu, from 10 to 225 µg/l; Zn, from 23 to 189 µg/l and Pb, from < 3 to 30 µg/l. There are significant statistical differences in the concentration of heavy metals between the different sampling sites and between the different sampling campaigns. The Pearson correlation results indicate a strong correlation between some heavy metals in the water, this significant correlation (p < 0.05) indicating a natural or/and a shared contamination source for these metals. Metal concentration in the water mostly did not exceed the guide values given by Mexican regulation for agricultural use. Only Cu, Mn and Fe in total water phase exceeded the maximum permissible limits for irrigation proposes at some sites. Copyright © 2007 John Wiley & Sons, Ltd.
A Study of Fecal Incontinence in Patients with Chronic Anal Fissure: Prospective, Randomized, Controlled Trial of the Extent of Internal Anal Sphincter Division During Lateral Sphincterotomy
Authors: Elsebae Magdy M. A. 
Published: July 2007

AbstractBackgroundTroublesome fecal incontinence following a lateral internal sphincterotomy is often attributed to faulty surgical technique. However, it may be associated with coexisting occult sphincter defects. Whether continence is related to the extent of sphincterotomy remains debatable. The aim of the study is to identify fecal incontinence related to chronic anal fissure before and after lateral internal sphincterotomy and its relationship to the extent of internal anal sphincter division.MethodsOne hundred eight patients with chronic anal fissure were prospectively studied before and after lateral internal sphincterotomy. A questionnaire was completed for each patient before and after surgery with regard to any degree of fecal incontinence. Fecal incontinence severity index was assessed using the Cleveland Clinic Incontinence Score. The patients with preoperative perfect continence were randomized into two groups (46 patients in each group): Group 1 underwent traditional lateral internal sphincterotomy (up to the dentate line) and Group 2 were underwent a conservative internal anal sphincterotomy (up to the height of the fissure apex or just below it).ResultsMinor degrees of incontinence were present before surgery in 16 patients (14.8%). Results of the randomized trial revealed that temporary postoperative incontinence was newly developed in 6/92 of patients (6.52 %) who did not have it before surgery. Five of the six (10.86%) were in Group 1 one (2.17%) was in Group 2 (p = 0.039). Persistent incontinence occurred in two in Group 1 (4.35%). All of them were females. All have had a history of one or more vaginal deliveries.ConclusionA mild degree of fecal incontinence may be associated with chronic anal fissure at presentation rather than as a result of internal sphincterotomy. Troublesome fecal incontinence after lateral internal sphincterotomy is uncommon. Sphincterotomy up to the dentate line provided faster pain relief and faster anal fissure healing, but it was associated with a significant postoperative alteration in fecal incontinence than was sphincterotomy up to the fissure apex. Care should be exercised in female patients with a history of previous obstetric trauma, as internal anal sphincter division may further compromise sphincter function.
Liver Manipulation Causes Hepatocyte Injury and Precedes Systemic Inflammation in Patients Undergoing Liver Resection
Authors: van de Poll Marcel C. G. , Derikx Joep P. M. , Buurman Wim A. , Peters Wilbert H. M. , Roelofs Hennie M. J. , Wigmore Stephen J. , Dejong Cornelis HC 
Published: July 2007

AbstractBackgroundLiver failure following liver surgery is caused by an insufficient functioning remnant cell mass. This can be due to insufficient liver volume and can be aggravated by additional cell death during or after surgery. The aim of this study was to elucidate the causes of hepatocellular injury in patients undergoing liver resection.MethodsMarkers of hepatocyte injury (AST, GSTα, and L‐FABP) and inflammation (IL‐6) were measured in plasma of patients undergoing liver resection with and without intermittent inflow occlusion. To study the separate involvement of the intestines and the liver in systemic L‐FABP release, arteriovenous concentration differences for L‐FABP were measured.ResultsDuring liver manipulation, liver injury markers increased significantly. Arterial plasma levels and transhepatic and transintestinal concentration gradients of L‐FABP indicated that this increase was exclusively due to hepatic and not due to intestinal release. Intermittent hepatic inflow occlusion, anesthesia, and liver transection did not further enhance arterial L‐FABP and GSTα levels. Hepatocyte injury was followed by an inflammatory response.ConclusionsThis study shows that liver manipulation is a leading cause of hepatocyte injury during liver surgery. A potential causal relation between liver manipulation and systemic inflammation remains to be established; but since the inflammatory response is apparently initiated early during major abdominal surgery, interventions aimed at reducing postoperative inflammation and related complications should be started early during surgery or beforehand.
Brief report: Risky sexual behavior of adolescents in Belgrade: Association with socioeconomic status and family structure
Authors: Vukovic Dejana S. , Bjegovic Vesna M. 
Published: July 2007

ABSTRACTObjectiveThe aim of this study was to investigate the association between socioeconomic status and family structure with risky sexual behaviors in adolescents.MethodsA total of 1782 15‐year‐old Belgrade schoolchildren (47.5% boys and 52.5% girls) completed a questionnaire from the WHO study, “Health behavior of schoolchildren”.ResultsAdolescents with a higher weekly disposable income, those who perceived their family as wealthy, and those with difficulties in communication with their mothers were more likely to have had been sexually active (odds ratios (OR)=2.497, 1.876, and 1.253, respectively). Adolescents with a higher weekly disposable income were more likely to use contraception (OR=0.233), but those who perceived their families as better‐off and those living with only one parent were more likely not to use contraception (OR=4.794, 22.295 [living with father], and 6.169 [living with mother], respectively).ConclusionsThe perceived family wealth was significantly associated with having sexual intercourse and having sexual intercourse without using contraception. Family structure had a limited independent association with sexual behavior.
Differential prognostic importance of QRS duration in heart failure and acute myocardial infarction associated with left ventricular dysfunction
Authors: Fosbøl Emil Loldrup , Seibæk Marie , Brendorp Bente , Møller Daniél Vega , Ersbøll Mads , Torp‐Pedersen Christian , Køber Lars ,   for the Danish Investigations and Arrhythmia ON Dofetilide (DIAMOND) study group
Published: July 2007

AbstractBackground/AimsStudies of the prognostic importance of QRS duration in patients with heart failure (HF) have shown conflicting results and few studies have estimated the importance after myocardial infarction (MI).MethodsThe Danish Investigations and Arrhythmia ON Dofetilide (DIAMOND) study randomised 3028 patients to dofetilide (class III antiarrhythmic) or placebo. The study consisted of two almost identical trials conducted simultaneously. One trial included 1518 patients with chronic HF and the other trial 1510 patients with a recent MI. All patients had left ventricular dysfunction. Dofetilide did not influence mortality in either trial. QRS duration was systematically measured at randomisation and was available in 2972 patients.ResultsOver a 10 year observation period 1037 (70%) patients in the MI study and 1324 (87%) in the HF study died. In the MI study, risk of death increased 6% for each 10 ms increase in QRS duration (HR=1.06/10 ms increase in QRS (CI=1.04–1.09), p<0.0001) whereas QRS duration had no influence in the HF study after multivariable adjustment. The difference between HF and MI was significant (p<0.0004 for interaction).ConclusionQRS duration predicts death in patients with left ventricular dysfunction who have suffered MI. In patients with HF QRS duration is not predictive of mortality.
Treatment with beta‐blockers in nurse‐led heart failure clinics: Titration efficacy and predictors of failure
Authors: Gustafsson Finn , Schou Morten , Videbæk Lars , Nielsen Tonny , Ulriksen Hans , Markenvard John , Svendsen Tage Lysbo , Ryde Henrik , Vigholt Else , Hildebrandt Per ,   on behalf of the Danish Heart Failure Clinics Network
Published: July 2007

AbstractBackground:Beta‐blockers (BBs) are a cornerstone in the treatment of chronic heart failure (HF), but several surveys have documented that many patients are not offered treatment or are not titrated to target doses. In part to address this problem, specialized, nurse‐led HF clinics have been initiated in many countries. However, little information is available to describe if such programs are successful in initiating and up‐titrating BBs in daily clinical practice.Aims:To assess the proportion of patients with HF due to left ventricular systolic dysfunction on BB treatment three months after referral to a nurse‐led HF clinic, and to identify baseline predictors of treatment failure.Methods:Consecutive records from 14 Danish nurse‐led HF clinics were used.Results:1533 patients met inclusion criteria. Mean age was 68.7 years and 72= were men. Three months after the initial HF clinic visit 63= of the patients were being treated with a BB. Mean dose (relative to target dose) was 63 (±35)= in patients receiving a BB and target dose was reached by 21=. Patients who were not on BBs were more often female, elderly and in NYHA class III–IV. In a multivariable model only lower age predicted BB use at three months (P<0.05). Younger age (P<0.001) and higher systolic blood pressure (P<0.001) were associated with higher doses of BB.Conclusion:BB up‐titration continues to be a challenge even in specialized clinics dedicated to this task. Elderly patients appear to be less likely to receive treatment.