bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reorientational Dynamics of Organophosphate Glass Formers – a Joint Study by 31P NMR, Dielectric Spectroscopy and Light Scattering
Authors: Adishchev Sergey , Bock Daniel , Gainaru Catalin , Kahlau Robert , Micko Björn , Petzold Nikolaus , Pötzschner Björn , Rössler Ernst A. 
Published: October 2012

Abstract
We study molecular reorientation in the glass formers triethyl-, tripropyl-, and m-tricresyl phosphate by measuring 31P NMR spectra, relaxation (T
1 and T
2), stimulated echo decays and two-dimensional spectra over a large temperature range (130–370 K). The results are compared to those from dielectric spectroscopy (DS) and depolarized light scattering (LS). While the time constants τ

α
of the primary (α-) process in the range × 10−11–100 s well agree, the stretching of the reorientational correlation function is probe dependent, i.e., the rank-two functions (NMR and LS) essentially agree whereas the rank-one function (DS) is less stretched. The very similar 2D spectra recorded as a function of mixing time demonstrate that the reorientational mechanism does not significantly vary among the super-cooled liquids. A model of combining large- and small-angle reorientation allows for reproducing the 2D spectra and may be taken as generic for the dynamics in viscous molecular liquids. Pronounced secondary (β-) processes do not only effect the NMR relaxation but can be identified directly in the time domain by the stimulated echo technique. This becomes possible due to its broad time window (10 μs–100 s). Thus, applying the different 1D and 2D techniques makes 31P NMR well suited to probe molecular reorientation over a wide dynamic range.
1H NMR T
1 Relaxation of Polymer/Montmorillonite Nanocomposites with Different Clay Contents and Degrees of Exfoliation: Magnetic Field Effects
Authors: Xu Bo , Leisen Johannes , Boehme Ute , Scheler Ulrich , Beckham Haskell W. 
Published: October 2012

Abstract
The initial stage of the NMR 1H T
1 relaxation of well-defined polypropylene-montmorillonite nanocomposites was investigated at two different magnetic fields of 0.54 and 7.05 T. At 0.54 T, two periods can be distinguished during the first 30 ms after a saturation pulse train. Both periods scale linearly with the square root of the recovery time. The first period occurs during the first 1 ms and is attributed to direct dipolar relaxation of nuclei in immediate proximity to the clay. It is caused by paramagnetic impurities within the clay and is characterized by a magnetization recovery curve with a slope proportional to the concentration of these impurities. The second period occurs at 4 to 30 ms after saturation and is due to spin diffusion between the sink, formed by the initial relaxation at the clay surface, and the surrounding polymer matrix, which relaxes at a much slower rate. The second period is characterized by a magnetization recovery curve with a slope proportional to the effective surface area of the clay, from which a degree of exfoliation may be determined. At 7.05 T, only a single relaxation recovery period is observed. At this higher magnetic field, the direct relaxation is characterized by a substantially longer relaxation time so that it is not distinguished from the spin-diffusion process. As with the slope of the second period of the magnetization recovery at 0.54 T, the slope of the magnetization recovery curve at 7.05 T can be utilized to extract a degree of exfoliation.
Dynamical Line-Shifts in High-Field Electron Spin Resonance: Applications to Polymer Physics
Authors: Bercu Vasile , Martinelli Massimo , Pardi Luca , Massa Carlo Andrea , Leporini Dino 
Published: October 2012

Abstract
High-field high-frequency Electron Paramagnetic Resonance spectroscopy (HF
2
-EPR) is a powerful tool to investigate, with ultra-high angular resolution, the rotational dynamics of complex systems like polymers, viscous fluids and glasses. Usually, information is drawn by detailed numerical analysis of the overall lineshape. Here, we present a simplified analytical model of the line shifts due to the rotational dynamics of the paramagnetic centre. The model captures the basic features of the reorientation process (time scale and size of the angular jump). It is compared with experimental results concerning the reorientation of a paramagnetic guest molecule dissolved in polystyrene. We find that, if the rotational model to describe the reorientation of the radical is consistent, the best-fit parameters yield equally acceptable best-fits of the overall spectrum by numerical simulations and dynamical line shifts by independent analytic expressions.
Multinuclear NMR Study of Zinc Dicyanide
Authors: Werner-Zwanziger Ulrike , Chapman Karena W. , Zwanziger Josef W. 
Published: October 2012

Abstract
The isotropic negative expansion of Zn(CN)2 has been linked to a temperature induced increase in off-axis tilting of the C–N bond direction and an increase in CN-bond length. However, the bond length could be determined only indirectly based on pair-distribution function analysis and was found to be surprisingly large. Here we study Zn(CN)2 by nuclear magnetic resonance spectroscopy and first principles calculations. By using samples enriched in
13
C and
15
N the dipole coupling between carbon and nitrogen is determined, and from this an upper bound on the C–N bond length of 1.19 ± 0.01 Å is derived. This quantity agrees with earlier determinations based on diffraction but is shorter than estimates based on pair distribution function analysis. The relation of this estimate to possible dynamics in the sample is discussed. Finally,
67
Zn NMR is used together with first principles calculations to assess disorder in the material.
Melting of Low Molecular Weight Compounds in Confinement Observed by2H-Solid State NMR: Biphenyl, a Case Study
Authors: de Sousa Amadeu Nader , Grünberg Bob , Frydel Jarek , Werner Mayke , Limbach Hans-Heinrich , Breitzke Hergen , Buntkowsky Gerd 
Published: October 2012

AbstractThe2H-NMR solid echo spectra of biphenyl molecules as guests in the mesopores of neat and silylated SBA-15 have been measured as a function of temperature. At low temperatures typical2H-Pake patterns with parameters of (Qzz=132 kHz, corresponding to Qcc=176 kHz) and (η=0.04) are observed. All samples exhibit a strong reduction of the melting point from the bulk value of 342.4 K to values between 222 K and 229 K, depending on both the pore diameter and the surface state and a glass like behavior of the biphenyl molecules in the melting regime. Employing the Roesslertwo-phase modelof the modeling of glass-transitions by2H-solid state NMR the distribution of activation energies for the rotational motions has been determined. At temperatures closely below the glass-transition temperature deviations from a static Pake pattern of an aromatic deuteron are observed, which indicate a pre-melting motion of biphenyl, which could be caused by C2-ring flips of the phenyl rings.
Kinetics of Coupled Double Proton and Deuteron Transfer in Hydrogen-Bonded Ribbons of Crystalline Pyrazole-4-carboxylic Acid
Authors: Torres Verónica , Lopez Juan-Miguel , Langer Uwe , Buntkowsky Gerd , Vieth Hans-Martin , Elguero José , Limbach Hans-Heinrich 
Published: October 2012

Abstract
The proton tautomerism of pyrazole-4-carboxylic acid (PCA) has been studied by a combination of 15N CPMAS and 2H NMR spectroscopy and relaxometry. Down to 250 K, PCA forms a hydrogen bonded ribbon where adjacent carboxylic and pyrazole groups are linked by an OH···N and an O···HN hydrogen bond, forming either the tautomeric state A or B. Down to about 250 K, the tautomerism is fast on the NMR timescale and degenerate, corresponding to a phase exhibiting dynamic proton disorder. At lower temperatures, a transition to an ordered phase is observed with localized protons, assigned to an all-syn conformation adopting the sequence of tautomeric states ..ABABA.. The longitudinal 15N relaxation times T
1 of PCA-15N2 have been measured at 9.12 MHz (2.1 T). Because of the low field, a chemical shift anisotropy mechanism could be neglected, and the data were analyzed in terms of a dipolar 1H-15N relaxation mechanism, yielding the rate constants k
HH. The rate constants k
HD and k
DD were obtained from the measurement and analysis of the 2H T
1 values of PCA-15N1-d0.9 and PCA-15N1-d0.1 measured at 46.03 MHz. Within the margin of error, no kinetic isotope effects could be detected, in contrast to previous results reported for the very fast tautomerism of solid benzoic acid dimers and the much slower tautomerism of solid 3,5-diphenyl-4-brompyrazole (DPBrP) dimers. The Arrhenius curves of all three systems were simulated using the Bell–Limbach tunneling model. Evidence for a major heavy atom motion for the tautomerism of PCA is obtained, associated with small angle reorientation of PCA molecules around the molecular axis. The observed proton order-disorder transition and the mechanism of the observed rate process are discussed in terms of a coupling of adjacent tautomeric states.
Transfer of Parahydrogen Induced Polarization in Scalar Coupled Systems at Variable Magnetic Field
Authors: Kiryutin Alexey S. , Ivanov Konstantin L. , Yurkovskaya Alexandra V. , Kaptein Robert , Vieth Hans-Martin 
Published: October 2012

Abstract
Para-Hydrogen Induced Polarization (PHIP) experiments were performed in coupled multispin systems at variable magnetic fields. We studied the magnetic field dependence of PHIP in styrene, which is the product of hydrogenation of phenylacetylene. At low magnetic fields where the spins are coupled strongly by scalar interaction efficient polarization transfer among the interacting protons takes place. The experimentally observed spectra are in good agreement with the simulation, which takes into account eight coupled spins. We also demonstrate effects of nuclear spin level anti-crossings on the PHIP pattern. It is shown that rapid passage through the level anti-crossing enables highly efficient polarization transfer between specific spin orders. In addition, we studied PHIP transfer to
13
C and
19
F hetero-nuclei. It is shown that hetero-nuclei can be efficiently polarized in a wide field range; in particular, for polarizing them it is not necessary to go to ultra-low fields, which provide their strong coupling to protons. The resulting polarization is of the multiplet type and gives strong enhancements of the individual NMR lines. In general, variation of the magnetic field gives the opportunity for manipulating PHIP patterns and transferring polarization to target spins of choice.
Concentration and Humidity Effect on Gelatin Films Studied by NMR
Authors: Ghoshal Sushanta , Mattea Carlos , Du Lijun , Stapf Siegfried 
Published: October 2012

Abstract
Gelatin films were prepared using different initial concentrations (1 to 30%) in H2O (w/v). The solid films were kept at four different environmental conditions at 20%, 43%, 75%, and 90% relative humidity, until complete equilibrium was achieved. Spin–spin relaxation (T
2) and spin–lattice relaxation (T
1) times of the samples were determined using a low-field nuclear magnetic resonance (NMR) spectrometer operated at 40 MHz proton (1H) Larmor frequency and were correlated with the molecular mobility of the system influenced by the humidity conditions and initial concentration. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were performed as well to investigate the thermal properties of the samples. The results indicate an increase in molecular mobility of the gelatin films with the increase of storage humidity independent of the initial concentration and suggest that the dynamic of the films depends on the amount of the water in the amorphous region of the film.
Deuteron Magnetic Resonance Studies of Anhydrous Caffeine
Authors: Nowaczyk Andre , Nath Ramesh Chandra , Zimmermann Herbert , Böhmer Roland 
Published: October 2012

AbstractMethyl deuterated caffeine powder was studied using2H-NMR relaxometry and line shape analysis. In caffeine's low-temperature phase the spin-lattice relaxation times indicate a thermally activated CD3reorientation (activation energy ≈4 kJ/mol). Below theT1minimum near 35 K the quadrupolar echo spectra develop features indicative for quantum mechanical tunneling. Dielectric measurements indicate the presence of dipole moment fluctuations with times scales that follow an Arrhenius law (energy barrier ≈107 kJ/mol). It is argued that the underlying motion involves small-angle molecular excursions and therefore remains undetectedviastimulated-echo spectroscopy. The hysteresis accompanying the order/disorder transition taking place above 400 K was monitored using solid-echo line shapes as well asviaspin relaxation times. In the high-temperature phase indications for the onset of anisotropic large-angle motions were obtained.
A Logical and Progressive Approach to Computed Tomography–Guided Implantology
Authors: Califano Joseph V. , Rosenfeld Alan , Mandelaris George 
Published: October 2012

Focused Clinical Question: What are the important factors contributing to the success of computed tomography (CT)–guided implantology, and how might this technology best be incorporated into practice?Summary: CT‐guided implantology has provided an opportunity to more completely assess and plan the surgical placement of dental implants. This technology allows viewing of both anatomic and prosthetic information preoperatively in an interactive format. A precise plan can be developed and transferred to the surgery with a computer‐generated surgical template. In addition, it facilitates preoperative collaboration among the restoring dentist, laboratory technologist, surgeon, and patient that establishes treatment goals and expectations. There are several types of guides that may be used in CT‐guided implantology, with each having different levels of guidance. A logical and progressive approach to implementing CT‐guided technology in practice involves a gradual increase in complexity while minimizing risk during the learning curve. Each case can be evaluated, planned, and suited to the patient's needs, as well as the clinician's preference, experience, and risk tolerance.Conclusions: Incorporating technological advances, such as CT‐guided implantology, into clinical practice requires cooperative and collaborative input of all those responsible for patient care. Each clinician must determine the most appropriate diagnostic approach for a given situation. Success in CT interpretation and guided surgery execution is proportional to experience and detail in planning. This paper provides some guidelines and options to incorporate such technology into practice and suggests a logical and progressive approach to ensure success.
Antibiotic Susceptibility of Periodontal Enterococcus faecalis
Authors: Rams Thomas E. , Feik Diane , Mortensen Joel E. , Degener John E. , van Winkelhoff Arie J. 
Published: October 2012

Background: Enterococcus faecalis may contribute to periodontal breakdown in heavily infected subgingival sites, particularly in patients responding poorly to mechanical forms of periodontal therapy. Because only limited data are available on the antimicrobial sensitivity of enterococci of subgingival origin, this study evaluates the in vitro antibiotic susceptibility of E. faecalis isolated from periodontitis patients in the United States.Methods: Pure cultures of 47 subgingival E. faecalis clinical isolates were each inoculated onto specially prepared broth microdilution susceptibility panels containing vancomycin, teicoplanin, and six oral antibiotics of potential use in periodontal therapy. After incubation in ambient air for 18 to 20 hours, minimal inhibitory drug concentrations were determined using applicable Clinical and Laboratory Standards Institute criteria and interpretative guidelines. The organisms were additionally evaluated for in vitro resistance to metronidazole at 4 μg/mL.Results: Periodontal E. faecalis exhibited substantial in vitro resistance to tetracycline (53.2% resistant), erythromycin (80.8% resistant or intermediate resistant), clindamycin (100% resistant to 2 μg/mL), and metronidazole (100% resistant to 4 μg/mL). In comparison, the clinical isolates were generally sensitive to ciprofloxacin (89.4% susceptible; 10.6% intermediate resistant) and 100% susceptible in vitro to ampicillin, amoxicillin/clavulanate, vancomycin, and teicoplanin.Conclusions: Tetracycline, erythromycin, clindamycin, and metronidazole revealed poor in vitro activity against human subgingival E. faecalis clinical isolates, and would likely be ineffective therapeutic agents against these species in periodontal pockets. Among orally administered antibiotics, ampicillin, amoxicillin/clavulanate, and ciprofloxacin exhibited marked in vitro inhibitory activity against periodontal E. faecalis, and may be clinically useful in treatment of periodontal infections involving enterococci.
Periodontal Disease and Pregnancy Hypertension: A Clinical Correlation
Authors: Pralhad Swati , Thomas Betsy , Kushtagi Pralhad 
Published: October 2012

Background: Periodontal disease is thought to be associated with increased risk of systemic diseases and adverse pregnancy outcomes, including pregnancy hypertension (PH). The aim of the present study is to find the prevalence of periodontal disease in females with PH in a rural‐based medical institute.Methods: The present case control study was performed with 200 females, 100 with PH and 100 without PH. Antenatal periodontal screening was performed within 72 hours of their hospital admission for delivery. The periodontal parameters assessed were oral hygiene index–simplified, gingival index, mean probing depth, and loss of attachment.Results: Prevalence of periodontal disease was 65.5% and was significantly higher (P <0.0001) in females with hypertension (relative risk = 1.5; 95% confidence interval [CI] = 1.3 to 1.9). Socioeconomic status, education, occupation, and body mass index did not appear to influence the relationship between periodontal disease and PH on bivariate multiple logistic regression analysis. Nulliparous females were at higher odds to develop periodontal disease and PH (odds ratio = 1.7; 95% CI = 0.5 to 6.1). As the severity of periodontal disease increased from moderate to severe, the severity of hypertension also increased (r2 = 0.8 and 0.5 for moderate and severe periodontal disease, respectively).Conclusion: Periodontal disease is more prevalent in females with PH.
Effectiveness of Periodontal Treatment to Improve Metabolic Control in Patients With Chronic Periodontitis and Type 2 Diabetes: A Meta‐Analysis of Randomized Clinical Trials
Authors: Sgolastra Fabrizio , Severino Marco , Pietropaoli Davide , Gatto Roberto , Monaco Annalisa 
Published: October 2012

Background: It was recently suggested that scaling and root planing (SRP) may help to improve glycemic and metabolic control in patients with chronic periodontitis (CP) and type 2 diabetes mellitus (DM2); however, the effectiveness of SRP in this role remains unclear. This meta‐analysis assesses the effectiveness of SRP in improving glycemic and metabolic control in patients with CP and DM2.Methods: A literature search of electronic databases was performed for articles published through May 16, 2012, followed by a manual search of several dental journals. A meta‐analysis was conducted according to the recommendations of the Cochrane Collaboration and the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA). Weighted mean differences (MDs) and 95% confidence intervals (CIs) were calculated for glycated hemoglobin A1c (HbA1c), fasting plasma glucose (FPG), total cholesterol (TC), triglycerides (TG), and high‐ and low‐density lipoprotein cholesterol (HDL and LDL, respectively). All outcomes were evaluated as changes from baseline to the end of follow‐up. Heterogeneity was assessed with the χ2‐based Cochran Q test and I2 statistic. The level of significance was set at P <0.05.Results: After the study selection process, five randomized clinical trials were included. Results of the meta‐analysis indicated that SRP was effective in the reduction of HbA1c (MD = 0.65; 95% CI 0.43 to 0.88; P <0.05) and FPG (MD = 9.04; 95% CI 2.17 to 15.9; P <0.05), but no significant differences were found in the reduction of TC, TG, HDL, or LDL. No evidence of heterogeneity was detected.Conclusion: The meta‐analysis results seem to support the effectiveness of SRP in the improvement of glycemic control in patients with CP and DM2; however, future studies are needed to confirm these results.
A Randomized, Double‐Masked Clinical Trial Comparing Four Periodontitis Treatment Strategies: 1‐Year Clinical Results
Authors: Preus Hans R. , Gunleiksrud Therese Mehlum , Sandvik Leiv , Gjermo Per , Baelum Vibeke 
Published: October 2012

Background: The benefit of full‐mouth disinfection (FDIS) over traditional scaling and root planing (SRP) remains equivocal, and it is not known whether the use of adjunctive antibiotics may enhance the effect of FDIS. The aim of the present study is to test the hypothesis that there is no difference in the 1‐year clinical outcome of therapy among groups of patients treated with conventional SRP performed over 2 to 3 weeks, or same‐day FDIS, with or without adjunctive metronidazole.Methods: A total of 184 patients with moderate‐to‐severe periodontitis were randomly allocated to one of four treatment groups: 1) FDIS+metronidazole; 2) FDIS+placebo; 3) SRP+metronidazole; or 4) SRP+placebo. Recordings of plaque, bleeding on probing, probing depth (PD), and clinical attachment level (CAL) were carried out in four sites per tooth at baseline and at 3 and 12 months after treatment.Results: No differences were observed in the mean CAL or PD values between the four experimental groups at baseline and 3 or 12 months post‐treatment. All four groups displayed significant improvements in all parameters. However, using absence of pockets ≥5 mm as the criterion for treatment success, the two groups receiving adjunctive metronidazole performed significantly better than the two placebo groups.Conclusion: Metronidazole had a significant, adjunctive effect in patients with a metronidazole‐sensitive subgingival microbiota on the clinical parameters of CAL, PD, and absence of pockets ≥5 mm.