bluuebunny/crossref_metadata_2025_split huggingface dataset:
The formation of HD 149026 b
Authors: Broeg C. , Wuchterl G. 
Published: February 2007

Abstract
Today, many extrasolar planets have been detected. Some of them exhibit properties quite different from the planets in our Solar system and they have eluded attempts to explain their formation. One such case is HD 149026 b. It was discovered by Sato et al. A transit-determined orbital inclination results in a total mass of 114 M⊕. The unusually small radius can be explained by a condensible element core with an inferred mass of 67 M⊕ for the best-fitting theoretical model.
In the core accretion model, giant planets are assumed to form around a growing core of condensible materials. With increasing core mass, the amount of gravitationally bound envelope mass increases. This continues up to the so-called critical core mass – the largest core allowing a hydrostatic envelope. For larger cores, the lack of static solutions forces a dynamic evolution of the protoplanet, accreting large amounts of gas or ejecting the envelope in the process. This would prevent the formation of HD 149026 b.
By studying all possible hydrostatic equilibria we could show that HD 149026 b can remain hydrostatic up to the inferred heavy core. This is possible if it is formed in situ in a relatively low-pressure nebula. This formation process is confirmed by fluid-dynamic calculations using the environmental conditions as determined by the hydrostatic models.
We present a quantitative in situ formation scenario for the massive core planet HD 149026 b. Furthermore, we predict a wide range of possible core masses for close-in planets like HD 149026 b. This is different from migration, where typical critical core masses should be expected.
The measurement of three dimensional dose distribution of a ruthenium‐106 ophthalmological applicator using magnetic resonance imaging of BANG polymer gels1
Authors: Chan Maria F. , Fung Albert YC , Hu Yu‐Chi , Chui Chen‐Shou , Amols Howard , Zaider Marco , Abramson David 
Published: February 2007

The BANG (MGS Research Inc., Guilford, CT) polymer gel has been used as a dosimeter to determine the three‐dimensional (3D) dose distribution of a ruthenium‐106 (Ru‐106) ophthalmologic applicator. An eye phantom made of the BANG gel was irradiated with the Ru‐106 source for up to 1 h. The phantom and a set of calibration vials were scanned simultaneously in a GE 1.5 T MR imager using the Hahn spin‐echo pulse sequence with a TR of 2000 ms and two TEs of 20 ms and 100 ms. The values were evaluated on a pixel‐by‐pixel basis using custom‐built software on a DEC alpha workstation and converted to dose using calibration data. Depth doses and isodose lines of the Ru‐106 eye‐plaque were generated. It is concluded that the BANG gel dosimetry offers the potential for measuring the 3D dose distributions of an ophthalmologic applicator, with high spatial resolution and relatively good accuracy.PACS number(s): 87.66.–a, 87.90.+y
Book Review
Authors: Smathers Jim 
Published: February 2007

General Practice of Radiation Oncology Physics in the 21st Century. Edited by Almon Shiu, Ph.D. and David Mellenberg Ph.D., 356 pp. Medical Physics Publishing, Madison, WI. 1998. ISBN: 0‐944838‐98‐7. Price: $75.00.PACS number(s): 87.53.–j
A self‐correcting method for improving the precision of beam blocks
Authors: Brezovich Ivan A. , Sparks Karen S. , Duan Jun 
Published: February 2007

A technique for manufacturing precise custom blocks is described. Using the tracing stylus of the mold making machine, reference markers are cut into the lateral borders of the polystyrene mold after the cavities for the blocks have been made. These markers are aligned with the central ray cross hair of the shadow tray when the blocks are mounted on the tray. The ability of the technique to enhance precision has been verified in laboratory tests by intentionally introducing small imperfections into a mold making machine and checking the positional accuracy of the mounted blocks. The clinical performance has been tested by evaluating 47 check films of blocks for 16 randomly selected patients. The average positional error of individual blocks, projected to the isocenter, was less than one mm. The average time needed to cut the reference markers was 25 seconds. Implementing the technique required only minor modifications of a commercial mold making machine.PACS number(s): 87.53.–j, 87.56.–v
A comparison of computer‐controlled versus manual on‐line patient setup adjustment
Authors: Brock Kristy K. , McShan Daniel L. , Balter James M. 
Published: February 2007

A study was performed to determine the relative advantage of computer‐controlled couch movement versus manual repositioning to correct patient setup error measured using an electronic portal imaging device (EPID). Twenty‐eight on‐line setup adjustment trials of anterior‐posterior (AP) pelvic projections were evaluated, with 13 setups corrected by automated couch movement determined by direct feedback from the EPID image alignment tool and 15 setups manually corrected based on the transformation displayed from the same tool. The speed of setup adjustment and accuracy of corrected setup were determined. Computer controlled setup adjustment was determined to be faster (25.4 s versus 101.9 s) and slightly more accurate (1.8 mm versus 2.5 mm error in adjusted setup) than manual correction.PACS number(s): 87.57.–s, 87.53.–j
Electron energy constancy verification using a double‐wedge phantom
Authors: Wells Derek M. , Picco Philip J. , Ansbacher Will 
Published: February 2007

Routine constancy checks of electron energy are often time consuming because of the necessity to measure a dose at two depths. A technique is described that uses a double‐wedge shaped phantom positioned on a Profiler™ diode array for measuring an electron energy constancy metric similar to . The double‐wedge electron profiles are invariant to phantom alignment in the wedge direction, unlike single wedge techniques, and the sensitivity of the technique is similar to water‐based depth‐dose measurements over an energy range of 6 to 20 MeV. Reproducibility results ranging from 0.01 to 0.03 cm were achieved for measurements taken over the course of 1.5 yrs. The technique is efficient in that only one phantom setup is required for all electron energies.PACS number(s): 87.53.–j, 87.66.–a
Evaluation of an automatic needle‐loading system
Authors: Morrier Janelle , Varfalvy Nicolas , Chrétien Mario , Beaulieu Luc 
Published: February 2007

The purpose of this paper is to evaluate the dosimetric capabilities and the radiation protection (RP) performance of a new automatic needle‐loading system for permanent prostate implants, the Isoloader (Mentor Corp.). The unit has been used in more than 100 clinical cases at our institution.The Isoloader is a computerized workstation that allows automated seed testing by a solid‐state CdZnTe radiation detector and loading in surgical needles. The seeds are received in a shielded and ready‐to‐use cartridge. Radiation protection measurements were done on a cartridge filled with 67 seeds and during dosimetric seed verification and needle loading. The reproducibility of the detector was tested and its accuracy was determined by comparison to specified activities of six calibration seeds and to their measurements in a calibrated well‐chamber (WC). Finally, the times required to complete dosimetric verification and needle loading were evaluated.The cartridge was found to be adequately shielded, since no significant amount of radiation was detected around it. Radiation during seed assay was found to be worst at the cartridge's bottom, where it has a value of ( at 10 cm). For the needle‐loading task, measurements were performed with a typical needle (three seeds) at the shielded needle holder surface yielding ( at 20 cm). Seed dosimetric verification takes an average of 15 s/seed, while it takes a mean time of 50 s/needle to complete the loading task. Measurements of the six seed activities were within 0.65% of the ordered activities and 1.9% higher on average than those from the WC . The reproducibility of the measurements of the CdZnTe detector was excellent, with an average of 0.01% of deviation from a reference measurement .We therefore conclude that the Isoloader is a safe, fast, and effective needle‐loading system.PACS number: 87.53.Jw
Determination of field size‐dependent wedge factors from a few selected measurements
Authors: Popple Richard A. , Brezovich Ivan A. , Duan Jun , Shen Sui , Pareek Prem N. , Ye Sung‐Joon 
Published: February 2007

Some modern treatment‐planning systems (TPSs) provide for input of wedge factor (WF) tables covering the entire range of square and elongated fields available on the LINAC. Depending on the field size increment chosen and the number of available wedge orientations, one may have to take more than 100 measurements per wedge and photon energy to commission the TPS. To expedite TPS commissioning while maintaining high accuracy, we demonstrate a simple method that requires only a few measurements per wedge, from which the remaining wedge factors can be found through linear interpolation based on field area. For the externally mounted wedges of two common LINACs, we have shown that WFs are proportional to field area and are nearly independent of field elongation and wedge orientation. Wedge factors computed from five to seven measurements comprised of square fields and a single, large rectangular field agreed with direct measurements throughout the entire range of achievable field dimensions within 0.6% at 6 MV and within 1% at 15 MV. Making the same set of measurements and using the equivalent square method to find WFs at other field sizes leads to errors up to 2%. Measuring the WF for a field and applying the same value to all field sizes can lead to errors of up to 10% at both 6 MV and 15 MV.PACS numbers: 87.53.Bn, 87.53.Mr
Target localization for post‐prostatectomy patients using CT and ultrasound image guidance
Authors: Paskalev Kamen , Feigenberg Steven , Jacob Rojymon , McNeeley Shawn , Horwitz Eric , Price Robert , Ma Charlie , Pollack Alan 
Published: February 2007

We conducted a study comparing B‐mode acquisition and targeting (BAT) ultrasound alignments based on CT data in the postoperative setting. CT scans were obtained with a Primatom CT‐on‐rails on nine patients. Two CT scans were obtained each week, while setup error was minimized by BAT ultrasounds. For the first three patients, a direct comparison was performed. For the next six patients, a template based on the shifts from the week 1 CT during treatment was used for subsequent setup. Comparison of isocenter shifts between the BAT ultrasound and CT was made by the difference, absolute difference, and improvement (using CT alignments as the reference technique). A total of 90 image comparisons were made. The average interfraction motion was 3.2 mm in the lateral, 3.0 mm in the longitudinal, and 5.1 mm in the AP direction. The results suggest that the CT‐based ultrasound templates can improve the localization of the prostate bed when the initial displacements are greater than 4 mm. For initial displacements smaller than 4 mm, the technique neither improved nor worsened target localization. However, ultrasound alignments performed without the use of a template deteriorated patient positioning for two out of three patients, demonstrating that the use of a CT template was beneficial even at small initial displacements.PACS numbers: 87.53.‐j, 87.53.Kn, 87.53.Xd
Performance and characteristics of an IR localizing system for radiation therapy
Authors: Lyatskaya Yulia , Lu Hsiao‐Ming , Chin Lee 
Published: February 2007

We report the development of a new system for interactive patient posture, position, and respiratory control during radiation therapy treatment. The system consists of an infrared (IR) camera, retroreflective markers, and dedicated software that makes it practical to use in the clinic. The system is designed to be used with multiple retroreflective markers to monitor not only the position, but also the posture of the patient in real time. Specific features of the system include the following: (1) The system reports an absolute misalignment at several points on a patient and also provides feedback on any necessary adjustments in terms of site‐specific setup parameters, such as focus‐to‐surface distance (PIN), superior and inferior alignment, and chest‐wall angle. (2) The system is based on a set of predefined templates containing the number and position of control points and feedback parameters developed for different treatment sites. (3) A noninvasive IR‐based “virtual portal vision” procedure projects organ contours in the beam's‐eye‐view (BEV) based on the IR marker locations obtained in real time and compares them with digitally reconstructed radiographs (DRRs) from CT simulation. Assuming good correlation between external markers and internal anatomy, the system offers the possibility of mimicking a verification procedure without taking port‐films, which can potentially reduce the setup time. In this paper, we concentrate on the system properties and performance while initial applications on a number of clinical sites are ongoing. Accuracy and precision of this system are evaluated in the context of breast/chest treatments using rigid phantoms. The system has an intrinsic uncertainty of . When two systems in different rooms (CT and treatment rooms) are used for correlating positional information, the uncertainty is less than 2 mm.PACS number: 87.56.Da
Analysis of the sources of uncertainty for EDR2 film‐based IMRT quality assurance
Authors: Shi Chengyu , Papanikolaou Nikos , Yan Yulong , Weng Xuejun , Jiang gyu 
Published: February 2007

In our institution, patient‐specific quality assurance (QA) for intensity‐modulated radiation therapy (IMRT) is usually performed by measuring the dose to a point using an ion chamber and by measuring the dose to a plane using film. In order to perform absolute dose comparison measurements using film, an accurate calibration curve should be used. In this paper, we investigate the film response curve uncertainty factors, including film batch differences, film processor temperature effect, film digitization, and treatment unit. In addition, we reviewed 50 patient‐specific IMRT QA procedures performed in our institution in order to quantify the sources of error in film‐based dosimetry. Our study showed that the EDR2 film dosimetry can be done with less than 3% uncertainty. The EDR2 film response was not affected by the choice of treatment unit provided the nominal energy was the same. This investigation of the different sources of uncertainties in the film calibration procedure can provide a better understanding of the film‐based dosimetry and can improve quality control for IMRT QA.PACS numbers: 87.86.Cd, 87.53.Xd, 87.57.Nk
Long‐term stability of a 50‐kV X‐ray unit for stereotactic irradiation
Authors: Biggs Peter J. 
Published: February 2007

A low‐energy (50 kV) X‐ray tube used for the stereotactic irradiation of intracranial lesions has been in use since 1999. The unit is calibrated prior to every procedure and during periodic quality assurance (QA) tests. The unit uses an internal and an external scintillation detector to monitor dose as well as a conventional timer. The records of these calibrations were reviewed to see whether a change in the output had occurred over that period. Using time as the reference, it was found that both the internal radiation monitor (IRM) and the beam output, determined with a parallel plate ionization chamber, dropped by variable amounts over the given period. The beam output dropped significantly more than the IRM, while the external radiation monitor (ERM) showed no significant deviation from its initial value. The beam output dropped to about 90% of its initial value after about 200 days but remained relatively constant thereafter. The IRM dropped steadily to about 96% to 97% of its initial value at 1000 days, but recovered to about 98% after that. Calibration prior to each procedure is strongly recommended.PACS numbers: 87.53.Dq; 87.56.By
Investigating treatment dose error due to beam attenuation by a carbon fiber tabletop
Authors: Myint W. Kenji , Niedbala Malgorzata , Wilkins David , Gerig Lee H. 
Published: February 2007

Carbon fiber is commonly used in radiation therapy for treatment tabletops and various immobilization and support devices, partially because it is generally perceived to be almost radiotransparent to high‐energy photons. To avoid exposure to normal tissue during modern radiation therapy, one must deliver the radiation from all gantry angles; hence, beams often transit the couch proximal to the patient. The effects of the beam attenuation by the support structure of the couch are often neglected in the planning process. In this study, we investigate the attenuation of 6‐MV and 18‐MV photon beams by a Medtec (Orange City, IA) carbon fiber couch. We have determined that neglecting the attenuation of oblique treatment fields by the carbon fiber couch can result in localized dose reduction from 4% to 16%, depending on energy, field size, and geometry. Further, we investigate the ability of a commercial treatment‐planning system (Theraplan Plus v3.8) to account for the attenuation by the treatment couch. Results show that incorporating the carbon fiber couch in the patient model reduces the dose error to less than 2%. The variation in dose reduction as a function of longitudinal couch position was also measured. In the triangular strut region of the couch, the attenuation varied following the periodic nature of the support structure. Based on these findings, we propose the routine incorporation of the treatment tabletop into patient treatment planning dose calculations.PACS numbers: 87.53.Dq, 87.53.Mr
A New Phylogenetic Cluster of Cereulide-Producing
Bacillus cereus
Strains
Authors: Vassileva Maria , Torii Keizo , Oshimoto Megumi , Okamoto Akira , Agata Norio , Yamada Keiko , Hasegawa Tadao , Ohta Michio 
Published: February 2007

ABSTRACT

Phenotypic and molecular studies have established that cereulide-producing strains of
Bacillus cereus
are a distinct and probably recently emerged clone within the
Bacillus
population. We analyzed a set of
B. cereus
strains, both cereulide producers and nonproducers, by multilocus sequence typing. Consistent with earlier reports, nonproducers demonstrated high heterogeneity. Most cereulide-producing strains and all flagellar antigen type H1 strains were allocated to the known sequence type of exclusively emetic
B. cereus
strains. Several cereulide-producing strains, however, were recovered at a new phylogenetic location, all of which were serotype H3 or H12. We hypothesize that the group of cereulide producers is diversifying progressively, probably by lateral transfer of the corresponding gene complex.
Failure To Control an Outbreak of
qnrA1
-Positive Multidrug-Resistant
Enterobacter cloacae
Infection despite Adequate Implementation of Recommended Infection Control Measures
Authors: Paauw Armand , Verhoef Jan , Fluit Ad C. , Blok Hetty E. M. , Hopmans Titia E. M. , Troelstra Annet , Leverstein-van Hall Maurine A. 
Published: February 2007

ABSTRACT

A large outbreak with an aminoglycoside-resistant
Enterobacter cloacae
(AREC) clone occurred at the University Medical Center Utrecht beginning in 2001 and continued up through the time that this study was completed. This clone (genotype I) contains a conjugative R plasmid carrying the
qnrA1
,
bla
CTX-M-9
, and
aadB
genes, encoding resistance to quinolones, extended-spectrum β-lactamases, and aminoglycosides, respectively. The aim of this study was to determine whether this clone was more transmissible than other AREC strains. Therefore, the dissemination of this genotype and of other
E. cloacae
strains was studied. In addition, infection control measures taken were evaluated. Pulsed-field gel electrophoresis analysis divided the 191 AREC strains into 42 different genotypes, of which 5 (12%) involved at least three patients. Aside from this outbreak (133 patients), only two other small outbreaks occurred, showing that the infection control measures were successful for all strains but one. Among 324 aminoglycoside-susceptible
E. cloacae
strains, 34/166 (20%) genotypes were identified from at least three patients, but only 4 involved small outbreaks. The outbreak strain was also detected in 11 of 15 other Dutch hospitals and caused outbreaks in at least 4. Evaluation of infection control measures showed that the outbreak strain disseminated throughout the hospital despite adequate implementation of internationally accepted guidelines on the control of multidrug-resistant
Enterobacteriaceae
(MRE). In conclusion, some MRE strains are better able to spread than others, and these strains may not be controlled by the current infection control guidelines. Strategies to identify such strains in an early phase and adapted guidelines for such “superbugs” are needed to prevent these clones from becoming endemic.
Determination of the Ex Vivo Rates of Human Immunodeficiency Virus Type 1 Reverse Transcription by Using Novel Strand-Specific Amplification Analysis
Authors: Thomas David C. , Voronin Yegor A. , Nikolenko Galina N. , Chen Jianbo , Hu Wei-Shau , Pathak Vinay K. 
Published: February 2007

ABSTRACT

Replication of human immunodeficiency virus type 1 (HIV-1), like all organisms, involves synthesis of a minus-strand and a plus-strand of nucleic acid. Currently available PCR methods cannot distinguish between the two strands of nucleic acids. To carry out detailed analysis of HIV-1 reverse transcription from infected cells, we have developed a novel strand-specific amplification (SSA) assay using single-stranded padlock probes that are specifically hybridized to a target strand, ligated, and quantified for sensitive analysis of the kinetics of HIV-1 reverse transcription in cells. Using SSA, we have determined for the first time the ex vivo rates of HIV-1 minus-strand DNA synthesis in 293T and human primary CD4
+
T cells (∼68 to 70 nucleotides/min). We also determined the rates of minus-strand DNA transfer (∼4 min), plus-strand DNA transfer (∼26 min), and initiation of plus-strand DNA synthesis (∼9 min) in 293T cells. Additionally, our results indicate that plus-strand DNA synthesis is initiated at multiple sites and that several reverse transcriptase inhibitors influence the kinetics of minus-strand DNA synthesis differently, providing insights into their mechanism of inhibition. The SSA technology provides a novel approach to analyzing DNA replication processes and should facilitate the development of new antiretroviral drugs that target specific steps in HIV-1 reverse transcription.
Some Physical and Dielectric Properties of Hydrous Alumina Films
Authors: Alwitt Robert S. 
Published: February 2007

Properties of pseudoboehmite films, produced by the reaction of aluminum foil with boiling water, were studied by a variety of techniques. For reaction times of 1–30 min the average film porosity decreased linearly with increasing film weight. The surface area of freshly prepared films was similar to that of alumina gel, but decreased on aging in air. Aging in

1
N

NaNO

3

inhibited the area decrease. The series capacitance decreased on aging in air or nitrate electrolyte. It was determined that with the sample immersed in electrolyte the measured dielectric properties were those of an inner region impermeable to electrolyte. This layer was not the same as a typical barrier oxide. The films exhibited a low frequency dielectric dispersion. From the temperature dependence of the loss maxima the activation energy and relaxation time for the process were found to be 13.4 kcal/mole and 6.2 × 10−15 sec. These are in the range found for other systems containing hydroxyl chains or bound water.