bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of endodontic sealers on dowels luted with resin cement
Authors: Burns David R. , Moon Peter C. , Webster Neal P. , Burns Donna A.
Published: October 2010

Purpose This study evaluated the retention of prefabricated parallel‐sided dowels luted with resin cement in extracted teeth that were obturated with gutta percha using a eugenol sealer or a calcium hydroxide sealer.

Materials and Methods Extracted maxillary incisor roots (N = 51) were instrumented to simulate conventional root canal therapy and divided into 3 groups (n = 17). One group was not obturated. Second and third groups were obturated with gutta percha using a eugenol‐containing or calcium hydroxide‐containing sealer. Gutta percha was removed using a heated plugger, and dowel spaces were prepared to a 7 mm depth. Dowel space walls were acid etched and primed, and prefabricated stainless steel dowels were luted using resin cement. After 24 hours, the load required to dislodge each dowel along a path parallel to its long axis was measured and recorded. A one‐way analysis of variance (α= 0.05) was performed to identify differences in the means among groups. The incidence of failure within the cement or at the dentin‐cement interface was also recorded.

Results No statistically significant difference was found among the control (159.9 ± 96.3 N), eugenol sealer (153.1 ± 77.3 N), and calcium hydroxide sealer (192.0 ± 89.3 N) groups. Nearly all specimens displayed adhesive failure at the dentin‐resin cement interface.

Conclusions Conventional endodontic obturation using a eugenol‐containing or a calcium hydroxide‐containing endodontic sealer did not affect retention of prefabricated stainless steel dowels luted with resin cement.
Dentists' preferences of anterior tooth proportion—a Web‐based study
Authors: Rosenstiel Stephen F. , Ward Daniel H. , Rashid Robert G.
Published: October 2010

Purpose This study aimed to determine dentists' esthetic preferences of the maxillary anterior teeth as influenced by different proportions. The goal was to link choices to demographic data as to the experience, gender, and training of the dentist.

Materials and Methods Computer‐manipulated images of the 6 maxillary anterior teeth were generated from a single image and assigned to 5 tooth‐height groups (very short, short, normal height, tall, and very tall). For each group, 4 images were generated by manipulating the relative proportion of the central incisors, lateral incisors, and canines according to the proportions 62% (or “golden proportion”), 70%, 80%, and “normal” or not further altered. The images were randomly ordered on a web page that contained a form asking for demographic data and fields asking for a ranking of the images. Dentists were asked via e‐mail to visit the web page and complete the survey. The responses were tabulated and analyzed with repeated measures logistic regression with the alpha at 0.05. A subset of North American respondents was chosen for further analysis.

Results A total of 549 valid responses were received and analyzed from dentists in 38 countries. There were statistically significant differences in all groups for the variables of proportion, group (tooth height), and their interaction. The 80% proportion was judged best for the Very Short and Short groups. Three of the choices were almost equally picked for the Normal Height and Tall groups, and the golden proportion was judged best for the Very Tall group. The variables of year of graduation, gender, professional activity, generalist or specialist, or number of patients were not significantly correlated with the choices for the North American respondents.

Conclusions Dentists preferred the 80 percent proportion when viewing short or very short teeth and the golden proportion when viewing very tall teeth. Golden proportion was worst for normal height or shorter teeth and the 80% proportion for tall or very tall teeth. They picked no clear‐cut best for normal height or tall teeth, and their choices could not be predicted based on gender, specialist training, experience, or patient load.
Laboratory‐fabricated, acrylic resin cylinders for fixed, provisional implant restorations
Authors: Rungruanganunt Patchanee , Andres Carl J.
Published: October 2010

Commercially produced provisional cylinders are commonly used during fabrication of fixed, provisional implant restorations. A procedure is presented for the fabrication of fixed, provisional implant restorations using laboratory‐fabricated, autopolymerizing acrylic resin cylinders. These cylinders offer a number of advantages over commercially produced cylinders and may reduce the treatment cost of implant prosthodontics.
The dimensions of mandibular lingual tissues relative to the placement of a lingual bar major connector
Authors: Cameron Stephen M. , Torres Gloria T. , Lefler Thomas B. , Parker M. Harry
Published: October 2010

Purpose The purpose of this investigation was to measure and describe the lingual tissues of the anterior mandible to determine the acceptable boundaries of the zone of nonmovable tissue for placement of a lingual bar and to compare these to existing numerical guidelines.

Materials and Methods Eighty subjects, grouped by age and gender, with clinically normal mandibular lingual gingival tissues from second premolar to second premolar were examined. The lingual sulcular depths (AB) and the distance from the gingival crest to movable tissue of the floor of the mouth (AC) were recorded. The zone of lingual nonmovable tissue was calculated (AC − AB) for each tooth.

Results For all subjects, the mean value of the probing depth (AB) ranged from 1.22 mm (±0.33 mm) for central incisors to 1.66 mm (±0.43 mm) for second premolars. The mean distance from the gingival crest to movable tissue of the floor of the mouth (AC) ranged from 7.44 mm (±1.59 mm) for central incisors to 10.28 mm (±2.55 mm) for second premolars. The mean height of the lingual nonmovable tissue (the zone available for the lingual bar; AC − AB) ranged from 6.22 mm (±1.59 mm) for central incisors to 8.63 mm (±2.57 mm) for second premolars. Most subjects presented with the minimum zone of nonmovable tissue at the central incisors, but with increasing age more subjects presented with minimum values at the posterior teeth. The multifactorial analysis of variance (ANOVA) for males' available nonmovable tissue shows significance for both tooth (p < 0.001) and age (p < 0.001) factors. The multifactorial ANOVA for females' available nonmovable tissue shows significance for both tooth (p < 0.001) and age (p < 0.001) factors. Of all subjects, 85% (88% of males, 83% of females) had 4 mm or more of nonmovable tissue, sufficient for a lingual bar. The amount of available room decreased in older females.

Conclusion Within the limits of this study, the use of actual measurements of lingual tissues versus existing numerical guidelines increased the percentage of patients for which the lingual bar can be used from approximately 6% to approximately 85%.
Laboratory strength of glass ionomer cement, compomers, and resin composites
Authors: Piwowarczyk Andree , Ottl Peter , Lauer Hans‐Christoph , Büchler Alfred
Published: October 2010

Purpose The study evaluates the compressive, flexural, and diametral tensile strengths of 8 core build‐up materials from different material classes (highly viscous glass ionomer cement, autocured resin composite, and compomers).

Materials and Methods All materials were manipulated according to the manufacturers' recommendations for use as core materials. At a temperature of 23.0 ± 1.0°C the properties of compressive, diametral tensile and flexural strength were determined using a universal testing machine at 15 minutes, 1 hour, and 24 hours after material preparation. Using one‐way analysis of variance (ANOVA), multiple mean value comparisons were performed to determine significant differences (p≤.05) between the core restoration materials.

Results The values for compressive strength varied from 40.3 ± 5.2 MPa (compomer) to 237.4 ± 37.3 MPa (autocured resin composite) for the 3 measurement times. At 15 minutes, 1 hour, and 24 hours after first mixing, the ANOVA showed significant differences (p≤.05) between the resin composite Core Paste and all of the other materials. Diametral tensile strengths ranged from 5.5 ± 1.1 MPa for glass ionomer cement to 39.1 ± 2.9 MPa for composite core material. Three‐point flexural strength showed values ranging from 12.1 ± 2.5 MPa for glass ionomer cement to 92.1 ± 9.7 MPa for compomer between the 3 measurement times.

Conclusions Setting time influences the mechanical properties of the materials tested in this study. Autopolymerizing resin composite Core Paste demonstrated greater compressive and flexural strengths at the 3 measurement times than the other materials tested. Reinforced composites, in comparison to the autocured resin composites, yielded no improvement in tensile strength. Flexural and tensile strengths of the glass ionomer cement were lower than those of autocured resin composites and compomers.
Effects of carbamide peroxides on wear resistance and color change of enamel opposing porcelain
Authors: Clelland Nancy L , Dorosti Yassamin , Seghi Robert R.
Published: October 2010

Purpose This study evaluated the effects of a simulated 1‐ and 2‐week night guard bleaching technique using various bleaching gel concentrations on wear resistance and color change of human enamel opposing a feldspathic porcelain substrate.

Materials and Methods VMK 68 feldspathic porcelain was formed into 15‐mm disks (n = 63) and fired according to manufacturer's recommendations. Enamel cusps were formed and shaped from extracted third molars and treated with 1 of 3 bleaching materials for 7 or 14 days. Specimens were kept at 37°C in 100% humidity. The control group was subjected to identical conditions but with water replacing the bleaching gel between and during bleaching treatments. After simulated bleaching, the enamel cusp specimens were subjected to 3‐body wear testing opposite a highly polished porcelain substrate. Enamel wear was evaluated using optical scanning methods, and color was measured with a small‐aperture colorimeter. Data were subjected to a one‐way repeated‐ measure analysis of variance and various post hoc statistics.

Results Results indicated that the within effect of treatment time (7 or 14 days) did not significantly affect (p= 0.13) the size of the resulting enamel wear facet, whereas the between effect of bleaching concentration was significant (p= 0.01). Statistical analysis of unbleached control groups suggests that between‐group differences can be explained by variations in wear rates of the 3 enamel groups, not by the concentration differences in bleaching gels. All bleaching treatments resulted in significant color changes (p= 0.04) compared to the unbleached control, but the bleach concentration did not significantly influence the magnitude of color change (p= 0.81).

Conclusions A simulated night guard vital bleaching treatment of 1 or 2 weeks had no significant effect on the wear resistance of human enamel in vitro. The increased bleaching treatment time and concentration did not significantly affect the amount of enamel color change.
Classification system for partial edentulism
Authors: McGarry Thomas J. , Nimmo Arthur , Skiba James F. , Ahlstrom Robert H. , Smith Christopher R. , Koumjian Jack H. , Arbree Nancy S.
Published: October 2010

The American College of Prosthodontists (ACP) has developed a classification system for partial edentulism based on diagnostic findings. This classification system is similar to the classification system for complete edentulism previously developed by the ACP. These guidelines are intended to help practitioners determine appropriate treatments for their patients. Four categories of partial edentulism are defined, Class I to Class IV, with Class I representing an uncomplicated clinical situation and class IV representing a complex clinical situation. Each class is differentiated by specific diagnostic criteria. This system is designed for use by dental professionals involved in the diagnosis and treatment of partially edentulous patients. Potential benefits of the system include (1) improved intraoperator consistency, (2) improved professional communication, (3) insurance reimbursement commensurate with complexity of care, (4) improved screening tool for dental school admission clinics, (5) standardized criteria for outcomes assessment and research, (6) enhanced diagnostic consistency, and (7) simplified aid in the decision to refer a patient.
The effect of disinfectants on the properties of dental gypsum: 1. Mechanical properties
Authors: Abdelaziz Khalid M. , Combe Edward C. , Hodges James S.
Published: October 2010

Purpose This study was conducted to evaluate the effect of selected disinfectants incorporated in the liquid of dental stones on material strength properties with the aim of developing a material with acceptable mechanical properties.

Materials and Methods Two types of dental stone (types III and V) were mixed with aqueous solutions of 0.525% sodium hypochlorite, 0.1% and 10% povidone‐iodine, and 2% glutaraldehyde, and with water as a control. The liquid/powder ratios recommended by the manufacturer were used. These materials were subjected to further modification by adding a mixture of 1.0% gum arabic and 0.132% calcium hydroxide to the hemihydrate powders before mixing with the disinfectant solutions at 2 different liquid/powder ratios for each. Both the regular and the modified materials were tested for compressive and diametral tensile strength after 1 hour and 1 week from the start of the mix. The structure of set materials was determined by scanning electron microscopy examination of fracture surfaces.

Results The disinfectants often reduced the strength of both types of dental stone. However, using either 0.1% povidone‐iodine or 0.525% sodium hypochlorite resulted in strength values comparable with that of the control. The addition of gum arabic and calcium hydroxide helped reduce the mixing liquid/powder ratios, improving the strength properties of the disinfected materials.

Conclusions Chemical disinfectants reduce the strength of dental gypsum when used as mixing water substitutes. Gum arabic and calcium hydroxide additives permit a lower liquid/powder ratio and can help offset this weakening.
Survey of implant experience by prosthodontists in the United States
Authors: Eckert Steven E. , Koka Sreenivas , Wolfinger Glenn , Choi Yong‐Geun
Published: October 2010

Purpose The paper presents results of a survey of members of the American College of Prosthodontists (ACP) conducted to determine experiences and practices with dental implants.

Materials and Methods Preliminary survey questions regarding the prosthetic and surgical use of dental implants were developed. The master list of questions was distributed to communities of interest to establish the most pertinent items of interest. The final questionnaire was distributed to all members of the ACP living or practicing in the United States and members engaged in the U.S. armed services. Responses were compiled and analyzed to determine correlation of responses using the chi‐squared test for count data (level of significance α= 0.05). Fisher's exact test was applied to all significant responses.

Results Surveys were distributed to 1815 ACP members. A total of 554 (31%) surveys were completed. On the basis of age distribution of survey respondents, it was determined that the respondents were representative of the ACP membership. The majority of the respondents (82%; CI, 79% to 85%) treat patients with implant‐supported prostheses, while 12% (CI, 10% to 15%) surgically place implants. Of those not placing implants, 24% reported a desire to place implants, while 43% of all respondents expressed a desire for an ACP‐sponsored course in implant placement. Increased age of the prosthodontist correlated negatively with a desire to place implants (p < 0.0001). Dissatisfaction with implant placement by others correlates with willingness to surgically place implants (p < 0.0001).

Conclusions Most prosthodontists (82%) use implant‐supported prostheses in their practices, but most of the implants are placed by non‐prosthodontists. There is general satisfaction with implant placement regardless of the specialty of the practitioner placing the implants. Younger prosthodontists expressed a greater desire to surgically place implants but were not statistically more likely to do so.
Pressure generated on a simulated oral analog by impression materials in custom trays of different designs
Authors: Masri Radi , Driscoll Carl F. , Burkhardt John , von Fraunhofer Anthony , Romberg Elaine
Published: October 2010

Purpose To measure the pressure exerted by maxillary edentulous impressions composed of 3 commonly used impression materials using four different impression tray configurations.

Materials and Methods The study was performed using an oral analog that simulated an edentulous maxillary arch. Three pressure transducers were imbedded in the oral analog, 1 in the mid‐palate area and the other 2 in the right and left ridge (maxillary first premolar areas). Custom trays of 4 different configurations were fabricated. The 3 impression materials tested were irreversible hydrocolloid, light‐body and medium‐body vinyl polysiloxane, and polysulfide. A total of 128 impressions were made. The custom tray and the oral analog were mounted using a reline jig. A Satec universal testing machine was used to apply a constant pressure of 2 kg/cm2 over a period of 5 minutes on the loaded custom tray. The pressure was recorded every 10 seconds. Factorial analysis of variance and Tukey's multiple comparison test were used to analyze the results.

Results A significant difference in the pressure produced using different impression materials was found (p≤0.001). Irreversible hydrocolloid and medium‐body vinyl polysiloxane produced a significantly higher pressure than light‐body vinyl polysiloxane and polysulfide impression materials. The presence of holes and/or relief did not significantly alter the magnitude of pressure.

Conclusions All impression materials produced pressure during maxillary edentulous impression making. Tray modification was not important in changing the amount of pressure produced. The impression materials used had more effect on the pressure produced during impression making on the simulated oral analog.
Custom modification of the Blom‐Singer tracheostoma valve housing
Authors: Lemon James C. , Lewin Jan S. , Martin Jack W. , Chambers Mark S.
Published: October 2010

A technique is presented for modifying the Blom‐Singer tracheostoma valve housing to improve peristomal skin adherence for hands‐free tracheoesophageal speech production following total laryngectomy. The finished product is thin, flexible, and maintains enhanced tear strength. The edges of a standard housing device for the Blom‐Singer valve are trimmed to allow for better accommodation to the tissue surface without distortion. A punch biopsy instrument is used to cut uniform holes around the housing device to allow for permeation of the silicone mixture for better mechanical adherence of the materials.
Evaluation of the pH of a new carbonated soft drink beverage: An in vivo investigation
Authors: Bartlett David W. , Bureau George P. , Anggiansah Angela
Published: October 2010

Purpose Recently, a modified version of a successful soft drink has been developed that aims to reduce the potential for dental erosion in consumers. The aim of this investigation was to compare the effect of the modified and original formula soft drink on the pH at various tooth surfaces during and after ingestion in subjects without erosion.

Materials and Methods Fifteen subjects (10 female and 5 male) without dental erosion drank both a modified and an unmodified beverage for over 5 minutes in a randomized order. Oral pH was measured with antimony electrodes positioned on the labial and palatal surfaces of an incisor and premolar and held in place by a close‐fitting vacuum‐formed appliance. The results were compared (using the Wilcoxon signed rank test, with matched pairs) for the percentage and total time that pH fell below 4, 5, and 5.5.

Results The percentage and total time that pH fell below 4 was significantly different between the drinks (P <0.02), but the total time that pH fell below 5 and 5.5 was not. The time taken for subjects to return to pre‐exposure pH levels in the mouth showed considerable variation between individuals.

Conclusions The modified‐formula drink appeared to have less erosive potential than the original formula when assessed by measuring pH at the tooth surface. Although the erosive potential has been reduced by modifying the soft drink, it has not been eliminated.
Reestablishing occlusal vertical dimension using a diagnostic treatment prosthesis in the edentulous patient: A clinical report
Authors: Mays Keith A.
Published: October 2010

To maintain a harmonious craniofacial system, the dental practitioner must establish an appropriate occlusal vertical dimension (OVD). Several methods can be used to determine an appropriate OVD. The patient presenting with decreased OVD represents a particular challenge for the dental practitioner in fabricating conventional dentures. This clinical report describes the use of a diagnostic treatment prosthesis to evaluate the patient's ability to manage such an increase in vertical dimension and to reestablish an appropriate occlusal vertical dimension. The use of a diagnostic treatment prosthesis at a vertical dimension 5 mm greater than what the patient presented with was determined to not cause discomfort over a 2‐month period. A conventional complete denture was fabricated based on the patient's ability to handle the increase during the trial period. This report reviews the literature on this topic and describes a clinical technique for reestablishing the OVD in edentulous patients.
On the equivalence of ring-coupled cluster and adiabatic connection fluctuation-dissipation theorem random phase approximation correlation energy expressions
Authors: Jansen Georg , Liu Ru-Fen , Ángyán János G.
Published: October 2010

The correlation energy in the direct random phase approximation (dRPA) can be written, among other possibilities, either in terms of the interaction strength averaged correlation density matrix, or in terms of the coupled cluster doubles amplitudes obtained in the direct ring approximation (drCCD). Although the corresponding dRPA correlation density matrix on the one hand, and the drCCD amplitude matrix on the other hand, differ significantly, they yield identical energies. Similarly, the analogous RPA and rCCD correlation energies calculated from antisymmetrized two-electron integrals are identical to each other despite very different underlying working equations. In the present communication, a direct correspondence between amplitudes and densities is established and investigated with perturbation theory arguments. Our analysis also sheds some light on the properties of recently proposed RPA/rCCD variants which use antisymmetrized integrals in part of the equations and nonantisymmetrized integrals in others.
Dissociation energetics of the phenol+⋯Ar2 cluster ion: The role of π→H isomerization
Authors: Tong Xin , Armentano Antonio , Riese Mikko , BenYezzar Med , Pimblott Simon M. , Müller-Dethlefs Klaus , Ishiuchi Shun-ichi , Sakai Makoto , Takeda Akihiro , Fujii Masaaki , Dopfer Otto
Published: October 2010

The dissociation energetics in the phenol+⋯Ar2(2π) cluster ion have been investigated using photoionization efficiency and mass analyzed threshold ionization spectroscopy. The appearance energies for the loss of one and two Ar atoms are determined as ∼210 and ∼1115 cm−1, respectively. The difference between the appearance energy for the first Ar ligand in phenol+⋯Ar2(2π) and the dissociation energy of the phenol+⋯Ar(π) dimer (535 cm−1) is explained by the isomerization of one π-bound Ar ligand to the OH binding site (H-bond) upon ionization. The energy difference between phenol+⋯Ar2(2π) and phenol+⋯Ar2(H/π) could also be estimated to be around 325 cm−1, which corresponds roughly to the difference of the binding energy of a π-bound and H-bound Ar ligands. The binding energy of the H-bound Ar atom in phenol+⋯Ar2(H/π) is derived to be ∼905 cm−1.
Phase-contrast imaging using ultrafast x-rays in laser-shocked materials
Authors: Workman J. , Cobble J. , Flippo K. , Gautier D. C. , Montgomery D. S. , Offermann D. T.
Published: October 2010

High-energy x-rays, >10 keV, can be efficiently produced from ultrafast laser target interactions with many applications to dense target materials in inertial confinement fusion and high-energy density physics. These same x-rays can also be applied to measurements of low-density materials inside high-density Hohlraum environments. In the experiments presented, high-energy x-ray images of laser-shocked polystyrene are produced through phase contrast imaging. The plastic targets are nominally transparent to traditional x-ray absorption but show detailed features in regions of high density gradients due to refractive effects often called phase contrast imaging. The 200 TW Trident laser is used both to produce the x-ray source and to shock the polystyrene target. X-rays at 17 keV produced from 2 ps, 100 J laser interactions with a 12 μm molybdenum wire are used to produce a small source size, required for optimizing refractive effects. Shocks are driven in the 1 mm thick polystyrene target using 2 ns, 250 J, 532 nm laser drive with phase plates. X-ray images of shocks compare well to one-dimensional hydro calculations.
The Fourier transform spectrometer of the Université Pierre et Marie Curie QualAir platform
Authors: Té Y. , Jeseck P. , Payan S. , Pépin I. , Camy-Peyret C.
Published: October 2010

A Bruker Optics IFS 125HR Fourier transform spectrometer (FTS) and the Laboratoire de Physique Moléculaire pour l'Atmosphère et l'Astrophysique retrieval algorithm were adapted for ground based atmospheric measurements. As one of the major instruments of the experimental research platform QualAir, this FTS is dedicated to study the urban air composition of large megacity such as Paris. The precise concentration measurements of the most important atmospheric pollutants are a key to improve the understanding and modeling of urban air pollution processes. Located in the center of Paris, this remote sensing spectrometer enables to monitor many pollutants. Examples for NO2 and CO are demonstrating the performances of this new experimental setup.
Note: Light output enhanced fast response and low afterglow L6i glass scintillator as potential down-scattered neutron diagnostics for inertial confinement fusion
Authors: Arikawa Yasunobu , Yamanoi Kohei , Nagai Takahiro , Watanabe Kozue , Kouno Masahiro , Sakai Kohei , Nakazato Tomoharu , Shimizu Toshihiko , Cadatal Marilou Raduban , Estacio Elmer Surat , Sarukura Nobuhiko , Nakai Mitsuo , Norimatsu Takayoshi , Azechi Hiroshi , Murata Takahiro , Fujino Shigeru , Yoshida Hideki , Izumi Nobuhiko , Satoh Nakahiro , Kan Hirofumi
Published: October 2010

The characteristics of an APLF80+3Ce scintillator are presented. Its sufficiently fast decay profile, low afterglow, and an improved light output compared to the recently developed APLF80+3Pr, were experimentally demonstrated. This scintillator material holds promise for applications in neutron imaging diagnostics at the energy regions of 0.27 MeV of DD fusion down-scattered neutron peak at the world’s largest inertial confinement fusion facilities such as the National Ignition Facility and the Laser Mégajoule.
Suppression of bimolecular recombination by UV-sensitive electron transport layers in organic solar cells
Authors: Ko Doo-Hyun , Tumbleston John R. , Ok Myoung-Ryul , Chun Honggu , Lopez Rene , Samulski Edward
Published: October 2010

Incorporating UV-sensitive electron transport layers (ETLs) into organic bulk heterojunction (BHJ) photovoltaic devices dramatically impacts short-circuit current (Jsc) and fill factor characteristics. Resistivity changes induced by UV illumination in the ETL of inverted BHJ devices suppress bimolecular recombination producing up to a two orders of magnitude change in Jsc. Electro-optical modeling and light intensity experiments effectively demonstrate that bimolecular recombination, in the form of diode current losses, controls the extracted photocurrent and is directly dependent on the ETL resistivity.
Simultaneous projection and detection system of four different frequencies for microwave imaging reflectometry in Large Helical Device
Authors: Yoshinaga T. , Nagayama Y. , Kuwahara D. , Tsuchiya H. , Yamaguchi S. , Kogi Y. , Tsuji-Iio S. , Mase A.
Published: October 2010

A simultaneous projection/detection system of four different frequencies for microwave imaging reflectometry (MIR) was developed for three-dimensional observation of electron density fluctuations in the Large Helical Device (LHD). The microwave with four frequency components at 60.410, 61.808, 63.008, and 64.610 GHz is projected in a continuous-wave mode to illuminate the target LHD plasma. A two-dimensional horn-antenna mixer array (2D HMA) receives the reflected wave from the plasma as well as the wave from the local oscillator operating at 55.800 GHz. The first intermediate frequency (IF) signals at 4.610, 6.008, 7.208, and 8.810 GHz were confirmed to be obtained by downconversion of these microwaves using the 2D HMA. Each of these first IF components is filtered from each other and downconverted again for the superheterodyne detection. It was confirmed that both the amplitudes and the phases of the detected signals reflect the fluctuations in LHD plasmas.
Kinetics of surface enrichment: A molecular dynamics study
Authors: Jaiswal Prabhat K. , Puri Sanjay , Das Subir K.
Published: October 2010

We use molecular dynamics to study the kinetics of surface enrichment (SE) in a stable homogeneous mixture (AB), placed in contact with a surface which preferentially attracts A. The SE profiles show a characteristic double-exponential behavior with two length scales: ξ−, which rapidly saturates to its equilibrium value, and ξ+, which diverges as a power-law with time (ξ+∼tθ). We find that hydrodynamic effects result in a crossover of the growth exponent from θ≃0.5 to θ≃1.0. There is also a corresponding crossover in the growth dynamics of the SE layer thickness.
Note: A time-resolved Kerr rotation system with a rotatable in-plane magnetic field
Authors: Qian Xuan , Gu Xiaofang , Ji Yang
Published: October 2010

A time-resolved Kerr rotation system with a rotatable in-plane magnetic field has been constructed to study anisotropic spin relaxation of electrons in semiconductors. A permanent magnet magic ring is placed on top of a motor-driven rotation stage (RS) to create the rotatable in-plane magnetic field. The RS is placed on a second translation stage to vary the local magnetic field around a sample. The in-plane magnetic field in such a system varies from 0.05 to 0.95 T, with full-round 360° rotatablity, thus offering a convenient and low-cost way to study the anisotropy of spin dynamics in semiconductors. Its performance was demonstrated via measurement of the anisotropy of the spin dephasing time (SDT) of electrons in a two-dimensional electron system embedded in a GaAs/Al0.35Ga0.65As heterostructure. The SDT with B∥[11¯0] was observed to be 10% larger than that with B∥[110], consistent with the results of others, which was measured via rotating sample.
Morphological control of GaAs quantum dots grown by droplet epitaxy using a thin AlGaAs capping layer
Authors: Jo Masafumi , Mano Takaaki , Sakoda Kazuaki
Published: October 2010

We demonstrate the control of GaAs quantum dots morphology by using a thin AlGaAs capping layer. The AlGaAs layer uniformly covers the GaAs quantum dots and provides protections against thermally induced deformation up to 580 °C, which allows improved dot quality. In addition, annealing of AlGaAs-capped quantum dots at 640 °C flattens the top of the dots, leading to the formation of height-controlled quantum dots and their narrow inhomogeneous width of 28 meV.
Size-dependent elastic properties of Au nanowires under bending and tension—Surfaces versus core nonlinearity
Authors: Wang Zhi-Jia , Liu Chong , Li Zhigang , Zhang Tong-Yi
Published: October 2010

The present work investigates contributions from surfaces and core nonlinearity to the size-dependent elastic properties of nanowires under bending and tension-compression. When a nanowire is formed by removing it from its parent bulk material, relaxation occurs inevitably because of high energy of newly created surfaces or born high surface eigenstress. Relaxation-induced initial strain could be large and nonlinear, which causes the size-dependent elastic properties of nanowires. If relaxation-induced initial strain is small and linear, the size-dependent elastic properties of nanowires are caused by surface Young’s modulus. The eigenstress model for surface stress of solids {Zhang et al. [Phys. Rev. B 81, 195427 (2010)]} is further developed here for nanowires under bending and tension-compression. The developed eigenstress model leads to general scaling laws for nanowires under bending and tension-compression. In the scaling laws, there are the surface and nonlinearity factors, which measure quantitatively the contributions of surfaces and core nonlinearity, respectively, to the nominal Young’s modulus of nanowires. Atomistic simulations on Au [001] nanowires verify the theoretical predictions.
Depletion interaction between spheres in an ideal equilibrium polymer fluid: Exact asymptotic results
Authors: Woodward Clifford E. , Forsman Jan
Published: October 2010

We use a continuum chain model and develop an analytical theory for the interaction between two spheres immersed in a fluid of ideal equilibrium polymers. The theory can be applied to both adsorbing and nonadsorbing spheres. Here we focus on two nonadsorbing spheres and determine the classical depletion interaction between them. Compact, and exact, results are derived for the asymptotic behavior of the depletion interaction, which has a Yukawa form. We show also that in the limit of large spheres (and large surface to surface separation) the Derjaguin approximation is valid. We compare our asymptotic expression with numerical solutions of an ideal equilibrium polymer fluid consisting of discrete chains. Our asymptotic approximation accurately predicts long-range interactions between small spheres. For large spheres it predicts the interaction very well over most of the separation range. We also consider a single sphere immersed in the polymer fluid and show how our results can be generalized to treat polydisperse polymer fluids, where the polydispersity is described by a Schulz–Flory distribution.
Point defects analysis of zinc oxide thin films annealed at different temperatures with photoluminescence, Hall mobility, and low frequency noise
Authors: Ke Lin , Lai Szu Cheng , Ye Jian Dong , Kaixin Vivian Lin , Chua Soo Jin
Published: October 2010

Zinc oxide (ZnO) thin films annealed at different temperatures were studied with photoluminescence (PL), electrical resistivity, Hall mobility, and 1/f noise spectroscopy. Relatively high electrical conductivity and carrier concentration in sample annealed at 400 °C suggested the presence of ZnO interstitials. Rapid reduction in electrical conductivity and carrier concentration upon increasing the annealing temperature suggested that ZnO interstitials could be eliminated by high temperature annealing. Presence of G-R noise in sample annealed at 400 °C indicated high level of electron trapping activities. Density of Zn vacancies acting as electron traps was estimated by Lorentzian fitting on the G-R noise. PL spectra exhibiting dominant green emission in all samples suggested the presence of Zn vacancies in high concentration. Yellow-orange emission in PL in samples annealed at 600 °C and below indicated the presence of O interstitials, while the same emission in samples annealed at higher temperatures were ascribed to Si impurities diffused from the substrate. Sharp reduction in mobility and surge in Hooge’s parameter in sample annealed at 700 °C implied high level of electron scattering due to large extrinsic Si impurities. Gradual rise in green-yellow emission and electron concentration as annealing temperature increased from 500 to 700 °C were ascribed to the gradual formation of O vacancies.
General boundary stabilization of memory-type thermoelasticity
Authors: Messaoudi Salim A. , Al-Shehri Aisha
Published: October 2010

In this paper we consider an n-dimensional system of thermoelasticity, where a viscoelastic dissipation is acting on a part of the boundary. By using a lemma, first appeared in the work of Messaoudi and Soufyane [“General decay of solutions of a wave equation with a boundary control of memory type,” Nonlinear Anal.: Real World Appl. (to be published)], we establish a general decay result, from which the usual exponential and polynomial decay are only special cases. Our result improves earlier ones in the literature and extends the general result of Messaoudi and Soufyane [“General decay of solutions of a wave equation with a boundary control of memory type,” Nonlinear Anal.: Real World Appl. 11, 2896 (2010] to thermoelastic systems.
Tailoring GaAs terahertz radiative properties with surface phonons polaritons
Authors: Vassant S. , Marquier F. , Greffet J. J. , Pardo F. , Pelouard J. L.
Published: October 2010

Absorption of visible and infrared radiation by gratings due to the resonant excitation of surface waves is a well-known phenomenon. In this paper, we study the resonant absorption of terahertz (THz) radiation due to the excitation of surface phonon polaritons on a grating ruled on a GaAs substrate. We report the design and fabrication of such a grating. Reflectivity measurements clearly show the excitation of surface phonon polariton. Numerical simulations indicate that the radiative properties depend critically on the surface profile. We finally discuss potential applications to THz thermal emission.
Effect of gap thickness on the viscoelasticity of magnetorheological fluids
Authors: López-López Modesto T. , Rodríguez-Arco Laura , Zubarev Andrey , Iskakova Larisa , Durán Juan D. G.
Published: October 2010

In this work, the effect of confinement distance on the magnetorheological (MR) properties of a conventional MR fluid, constituted by 30 vol % of iron microparticles dispersed in a liquid carrier, is studied. With this aim a commercial magnetorheometer supplied with parallel-plate geometry was used. The distance between the upper and the lower plate (gap thickness) was tuned from 10 to 400 μm. The steady-state and the dynamic regimes of the MR fluid in the presence of applied magnetic fields were studied as a function of the gap length. The experimental results show that in the preyield regime there is a strong increase in the magnitude of the viscoelastic moduli and the shear stress as the gap thickness is increased. The physical reason for this effect might be the influence of gap thickness on the particle structures induced by the field. This hypothesis is corroborated by microscopic observations in diluted systems. These experiments show that the aspect ratio (length/diameter) of the field-induced structures increases with the gap thickness. Theoretical analysis shows that the increase in the storage modulus with gap thickness can be explained by a decrease in the demagnetizing factor of these structures and, as a consequence, by an increase in the restoring torque, acting on them. The dissipation effects in the suspension under oscillating flow are rather produced by contact friction between the particles in the dense structures.
Ion temperature effect on the electron-dust collisions in complex dusty plasmas
Authors: Ki Dae-Han , Jung Young-Dae
Published: October 2010

The effects of ion temperature on the electron-dust collision process are investigated in complex dusty plasmas. The second-order eikonal method is employed to obtain the scattering phase and cross section for the electron-dust grain collision as functions of the impact parameter, collision energy, ion temperature, density, and Debye length. The results show that the eikonal scattering phase and eikonal electron-dust grain collision cross section decrease with decreasing ion temperature in dusty plasmas. It is also found that the effect of ion temperature on the electron-dust grain collision process is more significant than the effect of electron density in dusty plasmas. In addition, it is shown that the density effect is more significant when the electron temperature is comparable to the ion temperature.
X-ray photoelectron spectroscopy characterization of fluorite and perovskite phases in Sr1−xBi2+yTa2O9−z films
Authors: Akazawa Housei , Ando Hiroshi
Published: October 2010

High-resolution x-ray photoelectron spectroscopy of strontium bismuth tantalate films revealed distinct chemical states of constituent atoms in fluorite and perovskite crystals. Reflecting the number of nearest-neighbor oxygen atoms coordinated with Bi3+ ions, the Bi 4f peak could be deconvoluted into Bi2O3 (sixfold coordination), Bi2O2 (fourfold coordination), and (Bi2O2)2+ (intermediate between sixfold and fourfold coordination) components. We found that amorphous and fluorite phases could be expressed as a mixture of Bi2O3 and Bi2O2, whereas the (Bi2O2)2+ component representing the bismuth oxide layer, being adjacent to the (SrTa2O7)2− block, predominated in the perovskite phase. Similarly, the Sr 3d peak could be deconvoluted into the components of Sr oxide (SrO) and Sr in (SrTa2O7)2−. The volume fraction of the (SrTa2O7)2− component increased at higher annealing temperatures. The Ta 4d peaks, in contrast, located at the same binding energy for all samples, indicated that an energetically stable TaO6 octahedron unit is preferentially created. The binding energies of the O 1s state corresponding to O–Bi, O–Ta, and O–Sr bonds were identified at 531, 530, and 528.9 eV, respectively.
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emission of highly thulium doped fluorophosphate glasses
Authors: Tian Ying , Xu Rongrong , Zhang Liyan , Hu Lili , Zhang Junjie
Published: October 2010

A new type of fluorophosphate glasses with high thulium doping concentration (up to 10 mol % Tm3+) is investigated. The intensive 1.8 μm fluorescence is demonstrated with lower concentration quenching. On the basis of the measured Raman spectroscopy, it is revealed that the glass structure will be changed when adding Tm3+ ions into fluorophosphate glasses. Besides, the Judd–Ofelt parameters and radiative properties are calculated and discussed based on Judd–Ofelt theory. And the absorption and emission cross-sections of F34→H36 transition are also calculated by using McCumber and Beer–Lambert theories.
On the intermolecular Coulombic decay of singly and doubly ionized states of water dimer
Authors: Stoychev Spas D. , Kuleff Alexander I. , Cederbaum Lorenz S.
Published: October 2010

A semiquantitative study of the intermolecular Coulombic decay (ICD) of singly and doubly ionized water dimer has been carried out with the help of ab initio computed ionization spectra and potential energy curves (PECs). These PECs are particular cuts through the (H2O)2, (H2O)2+, and (H2O)2++ hypersurfaces along the distance between the two oxygen atoms. A comparison with the recently published experimental data for the ICD in singly ionized water dimers [T. Jahnke, H. Sann, T. Havermeier et al., Nat. Phys. 6, 139 (2010)] and in large water clusters [M. Mucke, M. Braune, S. Barth et al., Nat. Phys. 6, 143 (2010)] shows that such a simplified description in which the internal degrees of freedom of the water molecules are frozen gives surprisingly useful results. Other possible decay channels of the singly ionized water dimer are also investigated and the influence of the H-atom participating in the hydrogen bond on the spectra of the proton-donor and proton-acceptor molecules in the dimer is discussed. Importantly, the decay processes of one-site dicationic states of water dimer are discussed and an estimate of the ICD-electron spectra is made. More than 33% of the dications produced by Auger decay are found to undergo ICD. The qualitative results show that the ICD following Auger decay in water is also expected to be an additional source of low-energy electrons proven to be extremely important for causing damages to living tissues.
Si–InAs heterojunction Esaki tunnel diodes with high current densities
Authors: Björk M. T. , Schmid H. , Bessire C. D. , Moselund K. E. , Ghoneim H. , Karg S. , Lörtscher E. , Riel H.
Published: October 2010

Si–InAs heterojunction p-n diodes were fabricated by growing InAs nanowires in oxide mask openings on silicon substrates. At substrate doping concentrations of 1×1016 and 1×1019 cm−3, conventional diode characteristics were obtained, from which a valence band offset between Si and InAs of 130 meV was extracted. For a substrate doping of 4×1019 cm−3, heterojunction tunnel diode characteristics were obtained showing current densities in the range of 50 kA/cm2 at 0.5 V reverse bias. In addition, in situ doping of the InAs wires was performed using disilane to further boost the tunnel currents up to 100 kA/cm2 at 0.5 V reverse bias for the highest doping ratios.
Three-dimensional localization precision of the double-helix point spread function versus astigmatism and biplane
Authors: Badieirostami Majid , Lew Matthew D. , Thompson Michael A. , Moerner W. E.
Published: October 2010

Wide-field microscopy with a double-helix point spread function (DH-PSF) provides three-dimensional (3D) position information beyond the optical diffraction limit. We compare the theoretical localization precision for an unbiased estimator of the DH-PSF to that for 3D localization by astigmatic and biplane imaging using Fisher information analysis including pixelation and varying levels of background. The DH-PSF results in almost constant localization precision in all three dimensions for a 2 μm thick depth of field while astigmatism and biplane improve the axial localization precision over smaller axial ranges. For high signal-to-background ratio, the DH-PSF on average achieves better localization precision.
Picosecond absorption relaxation measured with nanosecond laser photoacoustics
Authors: Danielli Amos , Favazza Christopher P. , Maslov Konstantin , Wang Lihong V.
Published: October 2010

Picosecond absorption relaxation—central to many disciplines—is typically measured by ultrafast (femtosecond or picosecond) pump-probe techniques, which however are restricted to optically thin and weakly scattering materials or require artificial sample preparation. Here, we developed a reflection-mode relaxation photoacoustic microscope based on a nanosecond laser and measured picosecond absorption relaxation times. The relaxation times of oxygenated and deoxygenated hemoglobin molecules, both possessing extremely low fluorescence quantum yields, were measured at 576 nm. The added advantages in dispersion susceptibility, laser-wavelength availability, reflection sensing, and expense foster the study of natural—including strongly scattering and nonfluorescent—materials.
A Schwinger disentangling theorem
Authors: Cross Daniel J. , Gilmore Robert
Published: October 2010

Baker–Campbell–Hausdorff formulas are exceedingly useful for disentangling operators so that they may be more easily evaluated on particular states. We present such a disentangling theorem for general bilinear and linear combinations of multiple boson creation and annihilation operators. This work generalizes a classical result of Schwinger.