bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of changes in gingival contour from three‐dimensional co‐ordinate data in subjects with drug‐induced gingival overgrowth
Authors: Thomason J. M. , Ellis J. S. , Jovanovski V. , Corson M. , Lynch E. , Seymour R. A.
Published: September 2005

Objectives: This aim of this study was to develop and assess a technique that could be used to assess accurately the gingival volume changes seen in drug‐induced gingival overgrowth by the analysis of data obtained from an entire gingival surface by means of three‐dimensional imaging.

Material and Methods: Stone dental models of patients before and after gingivectomy procedures were digitized with a laser scanner and then regenerated as computer models constructed from the acquired three‐dimensional co‐ordinate data. A comparison of superposed “before” and “after” surfaces was undertaken to assess and accurately quantify changes in gingival contour.

Results: The mean vertical tissue reduction varied from 1.58 to 2.56 mm in the four study subjects and individual differences are shown. The maximum thickness of removed buccal gingival overgrowth was found to range between 1.20 and 3.40 mm. The volume of tissue removed from each inter‐dental papilla ranged from 4.2 to 46.1 mm3 and the mean volume of the papilla removed from each subject±SD values was 24.8±13.1 mm3.

Conclusion: This method will measure changes in gingival tissues to within 60 μm in one plane, making it ideal for the assessment of longitudinal changes in gingival contour as seen in the development of gingival overgrowth, its recurrence after surgery or the changes in volume brought about by surgery.
The effect of a mouth rinse containing phenolic compounds on plaque formation and developing gingivitis
Authors: Sekino Satoshi , Ramberg Per
Published: September 2005

Background: The clinical effect of Listerine®, a mouth rinse containing a mixture of phenolic compounds, is ascribed to its bactericidal properties. However, phenolic compounds are also known to interfere with the inflammatory process.

Objective: The purpose of this clinical trial was to evaluate the effect of regular mouth rinsing with Listerine®on plaque and gingivitis during a 2‐week period of no mechanical oral hygiene.

Material and Methods: Twenty‐one subjects were recruited for the study. On Day 0 of each 2‐week experimental period, the participants were told to abstain from all mechanical plaque‐control measures but to rinse twice a day with 10 ml of the assigned solution (test: Listerine®, positive control:0.1% chlorhexidine (CHX), negative control: saline) for 60 s. Each experimental period was preceded by a 2‐week period including oral hygiene instruction, scaling and professional mechanical tooth cleaning. Examinations included assessments of plaque and gingivitis (Days 0 and 14), sampling of plaque and collection of gingival crevicular fluid (GCF) (Days 0, 7 and 14). From the supragingival plaque samples, six different morphotypes of bacteria were counted using dark‐field microscopy. The GCF collected was analysed with respect to the content of lactoferrin and albumin.

Results: During the experimental periods, it was observed that significantly less plaque formed and less gingivitis developed when the participants rinsed with the Listerine® mouthwash than with saline solution. However, significantly more plaque formed during the Listerine® than during the CHX rinse period, while there was no significant difference in the development of gingival bleeding between the Listerine® and the CHX rinse regimens. Significantly smaller proportions of motile rods and fusiforms were found in the List and CHX groups than in the control (Ctrl) group. The increase of the lactoferrin/albumin ratio in the List group was significantly smaller than that in the Ctrl group but significantly larger than in the CHX group.

Conclusion: It was suggested that the effect of Listerine® on gingivitis is more pronounced than on plaque formation. This indicates that the phenolic compound may have anti‐inflammatory effects.
Use of the Vector™ scaling unit in supportive periodontal therapy: a subjective patient evaluation
Authors: Hoffman A. , Marshall R. I. , Bartold P. M.
Published: September 2005

Background: Patient discomfort is one reason for poor compliance with supportive periodontal therapy (SPT). The aim of this study was to compare the levels of discomfort during SPT, using the Vector™ system and treatment with a conventional ultrasonic scaler.

Methods: Forty‐six patients with an SPT programme were debrided using both the Vector™ system and a conventional piezo‐electric scaler (Sirona™) in a split mouth design. A visual analogue scale was used to evaluate of pain scores upon completion of treatment. A verbal response scale(VRS) was used to assess discomfort, vibration and noise associated with the scaling system, as well as the volume and taste of the coolant used by these systems.

Results: Patients instrumented with the Vector™ system experienced approximately half the amount of pain compared with the conventional ultrasonic scaling system. The VRS showed that the Vector™ system caused less discomfort than the conventional ultrasonic scaling system when assessed for pain, vibration, noise and volume of coolant. These findings were all statistically significant. There was, however, no statistically significant difference between the two systems when assessed for taste.

Conclusion: During SPT the Vector™ system caused reduced discomforting sensations compared with conventional methods and may be useful in improving compliance with SPT programmes.
Oral findings and periodontal status in children, adolescents and young adults suffering from renal failure
Authors: Davidovich E. , Schwarz Z. , Davidovitch M. , Eidelman E. , Bimstein E.
Published: September 2005

Aim: Describe the oral condition of chronic renal failure and healthy subjects, and the relationship between oral variables, chronic renal failure (CRF) conditions, and their treatment.

Materials and Methods: Four renal failure groups: chronic renal disease (n=22); undergoing dialysis (n=22); after dialysis and transplant (n=21); and after transplant (n=32), and a healthy control (n=38) were examined. Caries, enamel hypoplasia, pulp obliteration, plaque index, gingival bleeding, recession, overgrowth and index, probing depths, attachment loss, renal treatments and their relations with the oral variables were analysed.

Results: The renal failure groups had higher gingival index (GI) and bleeding, probing depths, attachment loss, hypoplasia and obliteration and less caries, than the control. Plaque was higher in the dialysis and pre‐dialysis (PD) groups. Overgrowth was evident after transplant. The PD group showed lower GI than other renal groups. Dialysis duration and end‐stage renal failure significantly correlated with gingivitis, probing depth, attachment loss and enamel hypoplasia. Immuran® correlated positively with probing depth, gingival recession and attachment loss. Normiten® and Nifedipine® had positive correlations with gingival overgrowth.

Conclusions: CRF patients are characterized by pulp obliteration, gingival and periodontal diseases. Duration of end stage renal failure and type of systemic treatment have a significant influence on the oral condition.
Adjunctive benefits of systemic amoxicillin and metronidazole in non‐surgical treatment of generalized aggressive periodontitis: a randomized placebo‐controlled clinical trial
Authors: Guerrero Adrian , Griffiths Gareth S. , Nibali Luigi , Suvan Jean , Moles David R. , Laurell Lars , Tonetti Maurizio S.
Published: September 2005

Background: The objective of this study was to assess the adjunctive clinical effect of the administration of systemic amoxicillin and metronidazole in the non‐surgical treatment of generalized aggressive periodontitis (GAP).

Methods: Forty‐one systemically healthy subjects with GAP were included in this 6‐month double‐blind, placebo‐controlled, randomized clinical trial. Patients received a course of full‐mouth non‐surgical periodontal treatment delivered over a 24 h period using machine‐driven and hand instruments. Test subjects received an adjunctive course of systemic antibiotic consisting of 500 mg amoxicillin and 500 mg metronidazole three times a day for 7 days. Clinical parameters were collected at baseline, and at 2 and 6 months post‐treatment.

Results: In both the test and the placebo groups, all clinical parameters improved at 2 and 6 months. In deep pockets (7 mm), the test treatment resulted in an additional 1.4 mm (95% confidence interval 0.8, 2.0 mm) in full‐mouth probing pocket depth (PPD) reduction and 1 mm (0.7, 1.3 mm) of life cumulative attachment loss (LCAL) gain at 6 months. In moderate pockets (4–6 mm), the adjunctive benefit was smaller in magnitude: PPD reduction was 0.4 mm (0.1, 0.7 mm) and LCAL gain was 0.5 mm (0.2, 0.8 mm). In addition, the 6‐month data showed LCAL gains 2 mm at 25% of sites in test patients compared with 16% in placebo (p=0.028). Similarly, PPD reductions of 2 mm or more were observed in 30% of sites in test and 21% of sites in placebo patients. Seventy‐four percent of pockets with PPD 5 mm at baseline were 4 mm or shallower at 6 months in the test group. This compared with 54% in the placebo group (p=0.008). Disease progression at 6 months was observed at 1.5% of test and 3.3% of sites in test and placebo, respectively (p=0.072).

Conclusions: These data indicate that a 7‐day adjunctive course of systemic metronidazole and amoxicillin significantly improved the short‐term clinical outcomes of full‐mouth non‐surgical periodontal debridement in subjects with GAP.
Effects of Tempol, a membrane‐permeable radical scavenger, in a rodent model periodontitis
Authors: Di Paola Rosanna , Mazzon Emanuela , Zito Daniele , Maiere Daniele , Britti Domenico , Genovese Tiziana , Cuzzocrea Salvatore
Published: September 2005

Background: Recent studies have demonstrated that Tempol (4‐hydroxy‐2,2,6,6‐tetramethylpiperidine‐N‐oxyl), a cell membrane‐permeable radical scavenger, exerts protective effects in various models of inflammation and shock. Reactive oxygen species (ROS) plays a pivotal role in the induction of genes involved in physiological processes as well as in the response to inflammation.

Aim: We have investigated the effect of Tempol in a rat model of periodontitis.

Materials and Methods: Periodontitis was induced in rats by placing a 2/0 braided silk ligature around the lower left first molar. At day 8, the gingivomucosal tissue encircling the mandibular first molar was removed for evaluation of neutrophils infiltration, tissue permeability, nitrotyrosine formation, poly‐(ADP‐ribose) polymerase (PARP) activation, radiography and histology.

Results and conclusions: Legation significantly induced an increased neutrophil infiltration and a positive staining for nitrotyrosine formation and PARP activation. Ligation significantly increased Evans blue extravasation in gingivomucosal tissue and alveolar bone erosion as evaluated by radiography analysis. Intraperitonial injection of Tempol (10 mg/kg daily for 8 days) significantly decreased all of the parameters of inflammation as described above. This suggests that antioxidant therapies, which interfere with ROS, may be of benefit in the treatment of periodontitis.
Infection patterns in chronic and aggressive periodontitis
Authors: Picolos Doros K. , Lerche‐Sehm Julia , Abron Armin , Fine James B. , Papapanou Panos N.
Published: September 2005

Background: We revisited the postulate that localized aggressive periodontitis (LAP) patients have robust serum antibody (ab) responses to periodontal pathogens while patients with generalized aggressive periodontitis (GAP) show weak responses. We also studied ab responses in localized chronic (LCP) and generalized chronic periodontitis (GCP).

Methods: Fifty‐seven patients (14–74 years, 25% male, 70% Hispanic, 26% African American) were studied (15 LAP, 19 GAP, 11 LCP, 12 GCP patients). Three plaque samples/subject were analysed with respect to 15 species, and serum immunoglobulin G (IgG) responses to the same bacteria were determined. Ab responses were expressed as log‐transformed titres, and “infection ratios”, i.e., log‐transformed ratios of ab titre over the subject‐based mean bacterial load for the homologous species.

Results: The results failed to corroborate the postulate that LAG patients have robust responses to infecting agents while GAP subjects exhibit weak responses. This held true for ab to “red complex”, “orange complex”, and health‐associated species, and for both titres and infection ratios. Similarly, no differences were found between ab titres or infection ratios in chronic and aggressive periodontitis, or their extent‐based subdivisions.

Conclusions: A distinction between the two principal categories of the current periodontitis classification cannot be established by the study of infection patterns.
Imbalance between soluble tumour necrosis factor receptors type 1 and 2 in chronic periodontitis
Authors: Ikezawa Ikuyo , Tai Hideaki , Shimada Yasuko , Komatsu Yasutaka , Galicia Johnah C. , Yoshie Hiromasa
Published: September 2005

Background: Soluble types of tumour necrosis factor (TNF) receptors type 1 and 2 modulate the TNF‐α‐mediated inflammatory responses in chronic periodontitis (CP).

Objectives: This study investigated the levels of TNF‐α, soluble TNF receptor type 1 and 2 in gingival crevicular fluid (GCF) and serum of healthy subjects and CP patients.

Materials and Methods: Thirty‐eight sera and 73 GCF samples were collected from 16 healthy subjects and 22 CP patients. GCF was collected from probing pocket depth (PPD)3 mm sites of healthy subjects, PPD3, 4–6 and 7 mm sites of CP patients. The levels of TNF‐α, soluble TNF receptor type 1 and 2 in the serum and GCF were quantified by enzyme‐linked immunosorbant assay.

Results: The total amounts of TNF‐α, soluble TNF receptor type 1 and 2 in GCF significantly elevated with increasing PPD in both site‐based (p<0.05) and subject‐based (p<0.05) analyses. However, their levels progressively diverged as the pocket depths increased, with the soluble TNF receptor type 2 level being comparatively lower than type 1. On the other hand, soluble TNF receptor type 2/type 1 ratios in GCF decreased as the severity of periodontitis increased (p<0.0001).

Conclusion: The imbalance between soluble TNF receptor type 1 and 2 levels in GCF could be related to CP severity.
Reproducible resistive switching in nonstoichiometric nickel oxide films grown by rf reactive sputtering for resistive random access memory applications
Authors: Park Jae-Wan , Park Jong-Wan , Kim Dal-Young , Lee Jeon-Kook
Published: September 2005

Ni 1 − δ O binary oxide films were deposited on Pt∕Ti∕SiO2∕Si substrates by radio-frequency reactive magnetron sputtering. The NiO-based metal-oxide-metal structures were fabricated for measurement of electrical properties. The electrical properties of the Pt∕Ni1−δO∕Pt structure as a function of growth temperature were investigated. The growth temperature was varied from room temperature to 400 °C. From all samples, negative resistance phenomenon and nonvolatile memory switching behavior were observed. The ratios between the high-resistance state (OFF state) and the low-resistance state (ON state) were larger than. 102. As the growth temperature was increased, both SET and RESET voltages increased due to the decrease of defects in nickel oxide films. On the basis of x-ray diffraction patterns, we confirmed that the defects in Ni1−δO film decreased with increasing the growth temperature due to sufficient diffusion and redistribution of adatoms. X-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy analysis revealed that the nickel oxide films were Ni deficient and that Ni had three different Ni bond states caused by various defects in nickel oxide films. In order to investigate the influence of the upper limit of SET current (i.e., Compliance SET current), the compliance SET current was varied from 1 to 50 mA. This result showed that the ON-state current and the RESET voltage were strongly dependent on the magnitude of the compliance SET current. As the compliance SET current was increased, both the ON-state current and the RESET voltage increased due to the increase of the conducting path. The results suggest that the resistance switching behavior is related to the formation and fracture of the conducting path which is composed of defects in the nickel oxide film.
Plasma treatment and its prospective application to polymer light-emitting diodes fabricated by ink-jet printing method
Authors: Jo Sung Jin , Jeong Soon Moon , Kim Woo Jin , Koo Won Hoi , Choi Sang Hun , Kim Chang Su , Baik Hong Koo , Lee Se-Jong
Published: September 2005

The influence of CF4 plasma treatment of indium-tin-oxide (ITO) and polyimide (PI) on the patterning of ink-jet printed polymer is presented. Not much difference between the as-received ITO and PI surface energies was found, but a significant difference in surface energies between ITO and PI after CF4 plasma treatment was noted. It is expected that precise patterning can be achieved by using the difference in surface energies between the inside of the pixel and its surroundings. Also the effects of CF4 plasma treatment of ITO have been studied on the performance of polymer light-emitting diodes (PLEDs). X-ray photoelectron spectroscopy revealed that CF4 plasma treatment led to a decrease in the surface content of carbon contaminants and an increase in the surface content of fluorine, which in turn enhance the performance of PLEDs.
Towards the single pump solution: Recent development in high speed machines for dry vacuum pumping
Authors: Chew A. D. , Galtry M. , Livesey R. G. , Stones I.
Published: September 2005

The goal of a single (dry) pump capable of reaching high vacuum and itself exhausting to atmospheric pressure has long existed in the vacuum field. The development of a single-shaft, high-speed pump EPX (second generation) mechanism has gone some considerable way to achieving this goal. The pump exploits molecular drag and a fluid dynamic mechanism and is discussed in terms of the theory of operation, internal flow mechanisms and the technology innovations enabling the mechanism to be produced in large volume quantities. Further development and application examples will be discussed to illustrate the system-simplification that the pump can provide.
Protection schemes for critical surface in vacuum environments
Authors: Kim Jung Hyeun , Asbach Christof , Yook Se-Jin , Fissan Heinz , Orvek Kevin J. , Ramamoorthy Arun , Yan Pei-Yang , Pui David Y. H.
Published: September 2005

This article presents a study of particle formation during vacuum pump down and methods that can be incorporated to protect critical surfaces (like semiconductor wafers or masks) from those particles. Particle formation during pump down was reexamined with temperature measurements. Particles were intentionally produced with hard pump down for studying protection schemes. For the first step, a face-down approach for a critical surface was used to investigate the effect of protection from particle contamination. It was very effective to hold a critical surface face down for protection with the use of high gravitational settling velocity in vacuum environment. However, the face down approach did not sufficiently protect the critical surface. For the second step, a bottom protective plate was introduced below the critical surface to improve the protection efficiency. The bottom plate played a great role in protection of the critical surface with preventing particle formation near the critical surface by keeping the surrounding gas temperature high enough to avoid particle formation as well as with potential blocking of incoming particles toward the critical surface. Higher gas temperature intrinsically avoids formation of residue particles by the condensation process during pump down.
Defect acceptor and donor in ion-bombarded GaN
Authors: Petravic Mladen , Coleman Victoria A. , Kim Ki-Jeong , Kim Bongsoo , Li Gang
Published: September 2005

We have employed synchrotron-based core level photoemission measurements and near-edge x-ray absorption fine structure spectroscopy to identify and characterize nitrogen interstitials in p-type GaN, created by nitrogen bombardment. From absorption measurements around the nitrogen K edge we have identified nitrogen interstitial levels within the band gap, in good agreement with theoretical predictions. The reduction in band bending determined from photoemission measurements was explained by the acceptor-like character of these defects. Argon bombardment produces nitrogen vacancies and the metallic Ga phase at the surface, which will produce the increased band bending and pinning of the surface Fermi level closer to the conduction band minimum.
Evidence of energy transfer from Si agglomerates to Er ions in aluminosilicate glass thin layers
Authors: Gourbilleau F. , Madelon R. , Prassas M. , Rizk R.
Published: September 2005

This paper shows evidence of the possible excitation of Er ions in Si-rich aluminosilicate glass layers deposited by magnetron sputtering through an energy transfer from Si nanoagglomerates formed after annealing at 450 °C. The intensity of the Er emission was found unaffected by the change of the excitation line from resonant to nonresonant over a certain range of wavelengths. The time decay dynamics have been also determined using the 476.5-nm-off-resonant excitation. The lifetime values were found to range between 2 and 4.1 ms, while the effective excitation cross section reaches ∼4×10−6cm2, nearly 4 orders of magnitude higher than its counterpart for the direct excitation of Er3+ ions. These results enhance the potential use of aluminosilicate glasses for the fabrication of planar optical amplifiers.
Real-time spectroscopic ellipsometry study of Ta–Si–N ultrathin diffusion barriers
Authors: Aouadi S. M. , Zhang Y. , Bohnhoff A. , Lee J. , Williams M.
Published: September 2005

This article reports on the use of real-time spectroscopic ellipsometry (RTSE) to (1) understand the growth process of ultrathin (10 nm thick) Ta–Si–N diffusion barriers and to (2) monitor their thermal stability up to a temperature of 800 °C. Thin films of Ta–Si–N diffusion barriers and Cu overlayers were deposited on Si(111) substrates using reactive unbalanced magnetron sputtering. In order to reduce roughness and interdiffusion between consecutive surfaces, a modulated low energy and high flux ion assistance was utilized. The initial part of the films (2 nm) of each layer was deposited with a high flux of low energy ions (<10eV) to reduce intermixing, while higher energies (between 40 and 130 eV) were utilized for the remainder of the layer to decrease the percolation thickness. RTSE data were simulated using the Drude-Lorentz model to obtain information about the growth mechanism and the conduction electron transport properties for these structures. The films were annealed at 800 °C and the diffusion of copper into silicon was evaluated by monitoring changes in the optical properties of the bilayers. The pseudodielectric function of the films was found to be altered whenever diffusion proceeded. Thermal stability at 800 °C was achieved for samples produced using the ion-assistance technique. The results deduced from RTSE were verified by characterizing the elemental composition of the as-deposited and heat-treated films using Rutherford backscattering and time-of-flight secondary ion mass spectrometry.
Target surface oxide layer formed by reactive sputtering of Ti target in Ar+O2 mixed gas
Authors: Abe Yoshio , Takamura Kenji , Kawamura Midori , Sasaki Katsutaka
Published: September 2005

Reactive sputtering is one of the most widely used techniques for preparing compound thin films. In this study, a Ti model target, a 1μm thick Ti film sputter deposited on a Si wafer, was used as the sputtering target. The thickness of the oxide layer formed on the surface of the model target after sputtering in an Ar+O2 mixed gas atmosphere was measured by ellipsometry under various varying processing parameters including oxygen flow ratio, sputtering time, rf power, and total gas pressure. The oxide layer thickness was varied from a few nanometers to approximately 100nm by changing the parameters, and a nonuniform oxide layer thickness was observed on the target surface.
Work function increase of indium–tin–oxide surfaces by atmospheric air plasma treatment with steady-state airflow
Authors: Choi Jai Hyuk , Lee Eung Suok , Choi Sang Hun , Baik Hong Koo , Song Kie Moon , Lim Yong Sik , Lee Seong-Min
Published: September 2005

Atmospheric air-plasma treatment of indium–tin–oxide (ITO) surfaces has been investigated as an alternative to a conventional oxygen (O2) vacuum plasma process. For this study, we devised an atmospheric air barrier plasma system having a dimension of 1000×600mm2 and successfully verified a possibility to ignite and maintain an atmospheric pressure discharge only in the ambient air. In particular, we used the steady-state airflow to generate more atomic oxygen radicals as oxygen gas during the vacuum plasma process and to prevent redeposition of the removed or transformed impurities onto the indium–tin–oxide substrate. The x-ray photoemission spectroscopy examination indicated that the adoption of the atmospheric-air plasma treatment reduced the surface content of carbon from 22.1% down to 8.5% and increased that of oxygen from 43% up to 57%. According to the photoelectron spectrometer (AC-1, RIKKEN) result, we obtained a work function of 5.11eV for the treated ITO surfaces after 1min treatment time, which is higher than that of 4.87eV for the untreated ITO surface. Consequently, we can effectively remove the carbon contamination and increase the work function of the ITO surface by means of the atmospheric air plasma treatment with steady-state airflow.
Deposition of vanadium carbide thin films using compound target sputtering and their field emission
Authors: Liao M. Y. , Gotoh Y. , Tsuji H. , Ishikawa J.
Published: September 2005

Vanadium carbide (VC) thin films were deposited on silicon substrates by direct sputtering of a VC target in an argon atmosphere. The structure, composition, and electrical properties of the films were investigated as functions of deposition conditions. The crystallographic structure of the film was strongly related to the argon pressure. VC films with (111) preferred orientation were formed at 2.0 Pa regardless of the substrate temperature examined, while amorphous films were obtained at the lowest pressure of 0.5 Pa. It was shown that carbon segregation within the film was difficult to avoid, but could be suppressed to some degree. To make a full understanding of the compositional variation in compound target sputtering process, deposition of chromium carbide thin films was also performed. Some common mechanisms involved in compound target sputtering process were discussed. Field emission measurements revealed that the VC film is a good electron emitter.
Binary and ternary NiTi-based shape memory films deposited by simultaneous sputter deposition from elemental targets
Authors: Sanjabi S. , Cao Y. Z. , Sadrnezhaad S. K. , Barber Z. H.
Published: September 2005

The most challenging requirement for depositing NiTi-based shape memory thin films is the control of film composition because a small deviation can strongly shift the transformation temperatures. This article presents a technique to control film composition via adjustment of the power supplied to the targets during simultaneous sputter deposition from separate Ni, Ti, and X (e.g., Hf) targets. After optimization of sputter parameters such as working gas pressure, target-substrate distance, and target power ratio, binary Ni100−xTix thin films were fabricated and characterized by energy dispersive x-ray spectroscopy in a scanning electron microscope (to measure the film composition and uniformity), in situ x-ray diffraction (to identify the phase structures), and differential scanning calorimetry (to indicate the transformation and crystallization temperatures). To explore the possibility of depositing ternary shape memory NiTi-based thin films with a high temperature transformation >100°C, a Hf target was added to the NiTi deposition system. Annealing was carried out in a high vacuum furnace slightly above the films’ crystallization temperatures (500 and 550 °C for NiTi and NiTiHf films, respectively). Differential scanning calorimetry (DSC) results of free-standing films illustrated the dependence of transformation temperatures on film composition: Ap and Mp (referring to the austenitic and martensitic peaks in the DSC curve) were above room temperature in near equiatomic NiTi and Ti-rich films, but below it in Ni-rich films. In NiTiHf films, the transformation temperatures were a function of Hf content, reaching as high as 414 °C (Ap) at a Hf content of 24.4 at. %. Atomic force microscopy revealed nanostructure surface morphology of both NiTi and NiTiHf films. Detailed characterization showed that the film properties were comparable with those of NiTi and NiTiHf bulk alloys.
Effect of nonsinusoidal bias waveforms on ion energy distributions and fluorocarbon plasma etch selectivity
Authors: Agarwal Ankur , Kushner Mark J.
Published: September 2005

The distributions of ion energies incident on the wafer significantly influence feature profiles and selectivity during plasma etching. Control of ion energies is typically obtained by varying the amplitude or frequency of a radio frequency sinusoidal bias voltage applied to the substrate. The resulting ion energy distribution (IED), though, is generally broad. Controlling the width and shape of the IED can potentially improve etch selectivity by distinguishing between threshold energies of surface processes. In this article, control of the IED was computationally investigated by applying a tailored, nonsinusoidal bias waveform to the substrate of an inductively coupled plasma. The waveform we investigated, a quasi-dc negative bias having a short positive pulse each cycle, produced a narrow IED whose width was controllable based on the length of the positive spike and frequency. We found that the selectivity between etching Si and SiO2 in fluorocarbon plasmas could be controlled by adjusting the width and energy of the IED. Control of the energy of a narrow IED enables etching recipes that transition between speed and selectivity without change of gas mixture.
Metrology and characterization of application specific chemical mechanical polishing pads
Authors: Zantye Parshuram B. , Mudhivarthi S. , Kumar Ashok , Obeng Yaw
Published: September 2005

There is a need for metrology, characterization, and optimization of chemical mechanical polishing (CMP) pad architecture before being put into service. A polishing pad which is made up of polyolefin material instead of conventional polyurethane has been developed. The surface of the pad has been modified to match the hardness of the surface of the material that is being polished. In this research, we coated the pad with tetraethylorthosilicate using plasma enhanced chemical vapor deposition for varying durations of time for optimum pad output. The pad was then extensively characterized using the several standard metrology techniques such as scanning electron microscopy, x-ray photoelectron spectroscopy, nanoindentation, etc. The CMP performance evaluation of all the candidate pads along with in situ measurement of dynamic coefficients of friction, material removal rate, and acoustic emission was done using CETR CP-4™ bench top CMP tester. There was a correlation and interdependence of the pad coating time and surface chemical, micromechanical, and tribological properties. However, their impact on the pad CMP performance was found to be indirect. Based upon these findings, suggestions were given for final pad architecture for commercialization. The demonstrated methodology can also be implemented for parametric optimization of novel polishing pads in the future.
Morphological and structural characterization of epitaxial α-Fe2O3 (0001) deposited on Al2O3 (0001) by dc sputter deposition
Authors: Lee Ik Jae , Kim Jae-Yong , Yu Chungjong , Chang Chang-Hwan , Joo Man-Kil , Lee Young Pak , Hur Tae-Bong , Kim Hyung-Kook
Published: September 2005

We investigated α-Fe2O3 (0001) film growth on α-Al2O3 (0001) using a laboratory-built dc faced magnetron sputtering system with x-ray diffraction, x-ray reflectivity, and atomic force microscopy (AFM). The films were deposited from iron targets at a growth rate of ∼6.3nm∕min in an ambient argon and oxygen mixture. The structural properties and quality of the α-Fe2O3 thin films were characterized using high-resolution synchrotron x-ray scattering. Films thinner than 16nm were to be found highly strained due to the large lattice mismatch between film and substrate of 5.8%. This strain was found to decrease as the film thickness increased, and most of the strain was released through surface modulation once the film thickness reached 20nm. The epitaxial relationships were found to be α-Fe2O3 [0001]‖α-Al2O3 [0001] in the out-of-plane direction. That the film and substrate display the in-plane alignment anticipated for the epitaxy of isomorphous materials was established by verifying that the [112¯0] directions of film and substrate were coincident. X-ray reflectivity and AFM were used to show that layer-by-layer growth of α-Fe2O3 (0001) occurs up to a thickness of 11nm despite the large lattice mismatch.
Hydrogen etching mechanism in nitrogen implanted iron alloys studied with in situ photoemission electron spectroscopy
Authors: Figueroa C. A. , Alvarez F.
Published: September 2005

In situ photoemission electron spectroscopy (XPS) is used to elucidate the hydrogen etching mechanism in nitrogen implanted iron alloys. The samples were prepared by bombarding stainless steel with a broad nitrogen ion source in a high vacuum chamber. The photoemission spectra evolution on increasing hydrogen ion current is correlated with the nitrided surface properties. The presence of hydrogen is associated with oxygen removal, augmenting the surface nitrogen concentration. The total active sites at the surface are constant, i.e., oxygen competes with nitrogen sites on the surface. The absorbed oxygen is etched following a linear law on hydrogen ion flux. Simultaneously, the formation of metallic nitrides is enhanced. At the working temperature, the efficiency of the process is determined by a characteristic time that depends on hydrogen retention time, water formation and desorption time.
Dosimetric effects of seed anisotropy and interseed attenuation for and prostate implants
Authors: Chibani Omar , Williamson Jeffrey F. , Todor Dorin
Published: September 2005

A Monte Carlo study is carried out to quantify the effects of seed anisotropy and interseed attenuation for and prostate implants. Two idealized and two real prostate implants are considered. Full Monte Carlo simulation (FMCS) of implants (seeds are physically and simultaneously simulated) is compared with isotropic point‐source dose‐kernel superposition (PSKS) and line‐source dose‐kernel superposition (LSKS) methods. For clinical pre‐ and post‐procedure implants, the dose to the different structures (prostate, rectum wall, and urethra) is calculated. The discretized volumes of these structures are reconstructed using transrectal ultrasound contours. Local dose differences (PSKS versus FMCS and LSKS versus FMCS) are investigated. The dose contributions from primary versus scattered photons are calculated separately. For , the average absolute total dose difference between FMCS and PSKS can be as high as 7.4% for the idealized model and 6.1% for the clinical preprocedure implant. Similarly, the total dose difference is lower for the case of : 4.4% for the idealized model and 4.6% for a clinical post‐procedure implant. Average absolute dose differences between LSKS and FMCS are less significant for both seed models: 3 to 3.6% for the idealized models and 2.9 to 3.2% for the clinical plans. Dose differences between PSKS and FMCS are due to the absence of both seed anisotropy and interseed attenuation modeling in the PSKS approach. LSKS accounts for seed anisotropy but not for the interseed effect, leading to systematically overestimated dose values in comparison with the more accurate FMCS method. For both idealized and clinical implants the dose from scattered photons represent less than of the total dose. For all studied cases, LSKS prostate DVHs overestimate by 2 to 5% because of the missing interseed attenuation effect. PSKS and LSKS predictions of and are overestimated by up to 9% in comparison with the FMCS results. Finally, effects of seed anisotropy and interseed attenuation must be viewed in the context of other significant sources of dose uncertainty, namely seed orientation, source misplacement, prostate morphological changes and tissue heterogeneity.
PI‐line‐based image reconstruction in helical cone‐beam computed tomography with a variable pitch
Authors: Zou Yu , Pan Xiaochuan , Xia Dan , Wang Ge
Published: September 2005

Current applications of helical cone‐beam computed tomography (CT) involve primarily a constant pitch where the translating speed of the table and the rotation speed of the source‐detector remain constant. However, situations do exist where it may be more desirable to use a helical scan with a variable translating speed of the table, leading a variable pitch. One of such applications could arise in helical cone‐beam CT fluoroscopy for the determination of vascular structures through real‐time imaging of contrast bolus arrival. Most of the existing reconstruction algorithms have been developed only for helical cone‐beam CT with constant pitch, including the backprojection‐filtration (BPF) and filtered‐backprojection (FBP) algorithms that we proposed previously. It is possible to generalize some of these algorithms to reconstruct images exactly for helical cone‐beam CT with a variable pitch. In this work, we generalize our BPF and FBP algorithms to reconstruct images directly from data acquired in helical cone‐beam CT with a variable pitch. We have also performed a preliminary numerical study to demonstrate and verify the generalization of the two algorithms. The results of the study confirm that our generalized BPF and FBP algorithms can yield exact reconstruction in helical cone‐beam CT with a variable pitch. It should be pointed out that our generalized BPF algorithm is the only algorithm that is capable of reconstructing exactly region‐of‐interest image from data containing transverse truncations.
Incorporating organ movements in IMRT treatment planning for prostate cancer: Minimizing uncertainties in the inverse planning process
Authors: Unkelbach Jan , Oelfke Uwe
Published: September 2005

We investigate an off‐line strategy to incorporate inter fraction organ movements in IMRT treatment planning. Nowadays, imaging modalities located in the treatment room allow for several CT scans of a patient during the course of treatment. These multiple CT scans can be used to estimate a probability distribution of possible patient geometries. This probability distribution can subsequently be used to calculate the expectation value of the delivered dose distribution. In order to incorporate organ movements into the treatment planning process, it was suggested that inverse planning could be based on that probability distribution of patient geometries instead of a single snapshot. However, it was shown that a straightforward optimization of the expectation value of the dose may be insufficient since the expected dose distribution is related to several uncertainties: first, this probability distribution has to be estimated from only a few images. And second, the distribution is only sparsely sampled over the treatment course due to a finite number of fractions. In order to obtain a robust treatment plan these uncertainties should be considered and minimized in the inverse planning process. In the current paper, we calculate a 3D variance distribution in addition to the expectation value of the dose distribution which are simultaniously optimized. The variance is used as a surrogate to quantify the associated risks of a treatment plan. The feasibility of this approach is demonstrated for clinical data of prostate patients. Different scenarios of dose expectation values and corresponding variances are discussed.
Computer‐aided detection of lung nodules: False positive reduction using a 3D gradient field method and 3D ellipsoid fitting
Authors: Ge Zhanyu , Sahiner Berkman , Chan Heang‐Ping , Hadjiiski Lubomir M. , Cascade Philip N. , Bogot Naama , Kazerooni Ella A. , Wei Jun , Zhou Chuan
Published: September 2005

We are developing a computer‐aided detection system to assist radiologists in the detection of lung nodules on thoracic computed tomography (CT) images. The purpose of this study was to improve the false‐positive (FP) reduction stage of our algorithm by developing features that extract three‐dimensional (3D) shape information from volumes of interest identified in the prescreening stage. We formulated 3D gradient field descriptors, and derived 19 gradient field features from their statistics. Six ellipsoid features were obtained by computing the lengths and the length ratios of the principal axes of an ellipsoid fitted to a segmented object. Both the gradient field features and the ellipsoid features were designed to distinguish spherical objects such as lung nodules from elongated objects such as vessels. The FP reduction performance in this new 25‐dimensional feature space was compared to the performance in a 19‐dimensional space that consisted of features extracted using previously developed methods. The performance in the 44‐dimensional combined feature space was also evaluated. Linear discriminant analysis with stepwise feature selection was used for classification. The parameters used for feature selection were optimized using the simplex algorithm. Training and testing were performed using a leave‐one‐patient‐out scheme. The FP reduction performances in different feature spaces were evaluated by using the area under the receiver operating characteristic curve and the number of FPs per CT section at a given sensitivity as accuracy measures. Our data set consisted of 82 CT scans (3551 axial sections) from 56 patients with section thickness ranging from . Our prescreening algorithm detected 111 of the 116 solid nodules (nodule size: ) marked by experienced thoracic radiologists. The test values were , , and in the new, previous, and combined feature spaces, respectively. The number of FPs per section at 80% sensitivity in these three feature spaces were 0.37, 1.61, and 0.34, respectively. The improvement in the test with the 25 new features was statistically significant compared to that with the previous 19 features alone.
Patient radiation doses for electron beam CT
Authors: Castellano Isabel A. , Dance David R. , Skinner Claire L. , Evans Phil M.
Published: September 2005

A Monte Carlo based computer model has been developed for electron beam computed tomography (EBCT) to calculate organ and effective doses in a humanoid hermaphrodite phantom. The program has been validated by comparison with experimental measurements of the CT dose index in standard head and body CT dose phantoms; agreement to better than 8% has been found. The robustness of the model has been established by varying the input parameters. The amount of energy deposited at the 12:00 position of the standard body CT dose phantom is most susceptible to rotation angle, whereas that in the central region is strongly influenced by the beam quality. The program has been used to investigate the changes in organ absorbed doses arising from partial and full rotation about supine and prone subjects. Superficial organs experience the largest changes in absorbed dose with a change in subject orientation and for partial rotation. Effective doses for typical clinical scan protocols have been calculated and compared with values obtained using existing dosimetry techniques based on full rotation. Calculations which make use of Monte Carlo conversion factors for the scanner that best matches the EBCT dosimetric characteristics consistently overestimate the effective dose in supine subjects by typically 20%, and underestimate the effective dose in prone subjects by typically 13%. These factors can therefore be used to correct values obtained in this way. Empirical dosimetric techniques based on the dose‐length product yield errors as great as 77%. This is due to the sensitivity of the dose length product to individual scan lengths. The magnitude of these errors is reduced if empirical dosimetric techniques based on the average absorbed dose in the irradiated volume are used. Therefore conversion factors specific to EBCT have been calculated to convert the to an effective dose.
Influence of phantom material and phantom size on radiographic film response in therapy photon beams
Authors: Palm Åsa , LoSasso Thomas
Published: September 2005

The energy dependence of radiographic film can introduce dosimetric errors when evaluating photon beams. The variation of the film response, which is attributed to the changing photon spectrum with depth and field size, has been the subject of numerous publications in recent years. However, these data show large unexplained differences in the magnitude of this variation among independent studies. To try to resolve this inconsistency, this study assesses the dependence of radiographic film response on phantom material and phantom size using film measurements and Monte Carlo calculations. The relative dose measured with film exposed to 6 MV x rays in various phantoms (polystyrene, acrylic, Solid Water, and water; the lateral phantom dimensions vary from 25 to 50 cm square; backscatter thickness varies from 10 to 30 cm) is compared with ion chamber measurements in water. Ranges of field size ( to ) and depth ( to 20 cm) are studied. For similar phantom and beam configurations, Monte Carlo techniques generate photon fluence spectra from which the relative film response is known from an earlier study. Results from film response measurements agree with those derived from Monte Carlo calculations within 3%. For small fields and shallow depths the film response variation is small, less than 4%, for all phantoms. However, for larger field sizes and depths, the phantom material and phantom size have a greater influence on the magnitude of the film response. The variation of film response, over the ranges of field sizes and depths studied, is 50% in polystyrene compared with 30% in water. Film responses in Solid Water and water phantoms are similar; acrylic is between water and polystyrene. In polystyrene the variation of film response for a 50 cm square phantom is nearly twice that observed in a 25 cm square phantom. This study shows that differences in the configuration of the phantoms used for film dosimetry can explain much of the inconsistency for film response reported in the literature.
L‐curve analysis of radiotherapy optimization problems
Authors: Chvetsov Alexei V.
Published: September 2005

We attempt to select an optimal value of regularization parameter in the optimization problems for intensity‐modulated radiotherapy which are solved using a variational regularization technique. We apply to inverse treatment planning the L‐curve method which was developed to determine the regularization parameter in the discrete ill‐posed problems. The L‐curve method is based on finding the regularization parameter which minimizes the residual norm which is a measure of accuracy of fit and the solution norm which is a measure of smoothness of solution. The main idea of the L‐curve method is to plot the smoothing norm as a function of the residual norm for all values of the regularization parameter. This characteristic curve has an L‐shaped dependence and the optimal value of regularization parameter can be found at the “corner” of the L‐curve. We plot the L‐curves for the optimization problems which simulate prostate radiotherapy cancer treatment with intensity‐modulated beams. Different numerical methods are applied to calculate the point of maximum curvature of the L‐curves which is a criterion to locate the corner. We show that the point of maximum curvature can be located in a most robust way using a formula derived from the singular value decomposition analysis.