bluuebunny/crossref_metadata_2025 huggingface dataset:
Optometric practice in Norway: a cross‐sectional nationwide study
Authors: Sundling Vibeke , Gulbrandsen Pål , Bragadottir Ragnheiður , Bakketeig Leiv S. , Jervell Jak , Straand Jørund
Published: April 2007

Purpose:  To describe optometric practitioners and their encountering patients.

Methods:  All members of the Norwegian Association of Optometrists working in the community (n = 761) were invited to participate in a questionnaire survey; questionnaire responders (n = 508) were asked to take part in a practice registration. Data collection was carried out between November 2004 and May 2005 using a questionnaire and a practice registration form.

Results:  Five hundred and eight optometrists responded to the questionnaire; of these 212 participated in the practice registration, in which 4052 patient encounters were recorded. All optometrists reported taking patient history in the areas of vision and ocular health; 55% asked questions about general health for all patients. More than 80% collaborated with general practitioners and ophthalmologists. The patient encounters were with 1699 men and 2216 women; 60% of patients were aged 45 years or older. Patients reported a history of ocular disease and other conditions of relevance for ocular health in 12% and 17% of encounters, respectively. One per cent had low vision [best corrected visual acuity (BCVA) < 0.33] and 2% were visually impaired (BCVA < 0.5). Ophthalmoscopy was performed for 88% of patients; dilated fundus examinations were carried out for 2%; clinical findings of cataract were reported for 11%; and retinopathy was suspected in 3%. Six per cent of patients were referred to a general practitioner or ophthalmologist.

Conclusion:  Optometrists generally collaborate with general practitioners and ophthalmologists. They take history, investigate and assess patients with ocular problems. A significant number of patients had primary or secondary ocular disease. This illustrates the role of optometrists as healthcare workers.
Gastroesophageal reflux disease in baboons (Papio sp.): a new animal model
Authors: Glover E.J. , Leland M.M. , Dick E.J. , Hubbard G.B.
Published: April 2007

Background  Gastroesophageal reflux disease (GERD) is increasingly prevalent in the human population. Current animal models require surgical or other manipulation to produce symptoms. An animal model that exhibits spontaneous GERD would provide the opportunity for much‐needed research examining the susceptibility, diagnosis, and treatment of GERD.

Methods  Eight baboons (Papio hamadryas sp.) were diagnosed with GERD histopathologically using biopsies or postmortem tissues.

Results  The disease was characterized by a spectrum of symptoms comparable with that found in the human population. Some subjects had no gross signs of clinical disease, but were diagnosed by histopathological examination. Almost all subjects presented with at least one clinical sign of the disease. Regurgitation was the most common.

Conclusions  The baboon may be a superior animal model for GERD research because it is a naturally occurring model and is anatomically and physiologically similar to humans.
Dental and periodontal findings in hemodialysis patients
Authors: Bayraktar G , Kurtulus I , Duraduryan A , Cintan S , Kazancioglu R , Yildiz A , Bural C , Bozfakioglu S , Besler M , Trablus S , Issever H
Published: April 2007

Objective:  Oral health problems of chronic renal failure patients can compromise systemic health. This study compared the periodontal and dental health status of patients on hemodialysis (HD) with healthy controls (C).

Study design:  Seventy‐six HD patients and 61 controls were examined for plaque deposits, gingivitis, periodontitis, calculus accumulation and oral health status.

Results:  There was no statistically significant difference in the measurement of probing pocket depths (PPD) in HD and C groups, but a highly significant difference was found for plaque index (P < 0.001), gingival index (GI) (P = 0.007) and calculus surface index (P < 0.001). There was a highly significant difference for GI (P = 0.001) and PPD scores (P < 0.001) between subgroups receiving HD for <3 years or more. A positive correlation between time on dialysis and parameter of missing teeth (r = 0.259; P = 0.024), GI scores (r = 0.474; P < 0.001) and measurement of PPD (r = 0.481; P < 0.001) was found in the HD group. Decayed, missing and filled teeth index scores were higher in the controls than the HD group, with no statistical significance.

Conclusions:  The dental and periodontal health status of HD patients is comparable with healthy controls, but becomes worse with time on dialysis. Thus, oral health maintenance is of utmost importance in this patient group.
Rescue of white egg 1 mutant by introduction of the wild‐type Bombyx kynurenine 3–monooxygenase gene
Authors: QUAN GUO‐XING , KOBAYASHI ISAO , KOJIMA KATSURA , UCHINO KEIRO , KANDA TOSHIO , SEZUTSU HIDEKI , SHIMADA TORU , TAMURA TOSHIKI
Published: April 2007

In silkworms, the white egg 1 (w‐1) mutant, which is characterized by white eyes and white eggs, is deficient in Bombyx kynurenine 3–monooxygenase (KMO) activity. To investigate whether the w‐1 mutant phenotype is rescued by introducing the wild‐type KMO gene, we constructed transgenic silkworms with the wild‐type Bombyx KMO gene under the control of either the cytoplasmic actin gene promoter (A3KMO) or the native KMO gene promoter (KKMO). We created two transgenic lines with A3KMO and one line with KKMO constructs. The eyes of adults in these lines were brown, and the eggs laid by the transgenic females were also brown. Reverse transcription‐polymerase chain reaction(RT‐PCR) analysis showed that the A3KMO silkworm lines expressed the transcript in the mid‐gut, fat bodies, and Malpighian tubules. The KKMO line expressed the transcript only in the fat bodies and Malpighian tubules. The intensity of eye and egg color in the transgenic lines was proportional to the KMO expression level. Interestingly, transgenic larvae with the A3KMO construct had a light brown larval cuticle, but the KKMO line did not. These results indicate that the wild‐type KMO gene can be used as a marker gene for visually screening transgenic silkworms.
Role of venom and ovarian proteins in immune suppression of Ostrinia furnacalis (Lepidoptera: Pyralidae) larvae parasitized by Macrocentrus cingulum (Hymenoptera: Braconidae), a polyembryonic parasitoid
Authors: LI YONG , LU JIAN‐FENG , FENG CONG‐JING , KE XIN , FU WEN‐JUN
Published: April 2007

Venom and ovarian proteins in braconid and ichneumonid wasps play an important role in the successful parasitism of their host, especially for immune suppression immediately after oviposition. In this study, we compared the effect of venom and ovarian proteins collected from the female wasps of Macrocentrus cingulum, a polyembryonic parasitoid of the larvae of Ostrinia funacalis, on the encapsulation capacity of Sephadex A‐25 beads at 4 h and 24 h post‐injection both in vivo and in vitro. The results showed that the ovarian proteins significantly interfered with the encapsulation capacity of hemocytes in a dose‐dependent manner. Spreading and viability of hemocytes in O. furnacalis was not disrupted by venom and ovarian proteins at various concentrations injected. It seems likely that the ovarian proteins from M. cingulum play a role in suppressing the encapsulation capacity of host hemocytes.
Partial genomic organization of ribosomal protein S7 gene from malaria vector Anopheles stephensi
Authors: DIXIT RAJNIKANT , DIXIT SARITA , ROY UPAL , SHOUCHE YOGESH S. , GAKHAR SURENDRA
Published: April 2007

In this study, we describe the partial genomic organization of ribosomal protein S7 gene isolated from the mosquito Anopheles stephensi. Initially a 558 bp partial cDNA sequence was amplified as precursor mRNA sequence containing 223 bp long intron. 5′ and 3′ end sequences were recovered using end specific rapid amplification of cDNA ends (RACE) polymerase chain reaction. The full‐length cDNA sequence was 914 nucleotide long with an open reading frame capable of encoding 192 amino acid long protein with calculated molecular mass of 22 174 Da and a pI point of 9.94. Protein homology search revealed > 75% identity to other insect's S7 ribosomal proteins. Analysis of sequence alignment revealed several highly conserved domains, one of which is related to nuclear localization signal (NLS) region of human rpS7. Interestingly, intron nucleotide sequence comparison with A. gambiae showed a lesser degree of conservation as compared to coding and untranslated regions. Like this, early studies on the genomic organization and cDNA/ Expressed sequence tag analysis (EST) could help in genome annotation of A. stephensi, and would be likely to be sequenced in the future.
Nutrient content affecting Spodoptera frugiperda and Dalbulus maidis occurrence in corn
Authors: BASTOS CRISTINA SCHETINO , CARDOSO GALVÃO JOÃO CARLOS , PICANÇO MARCELO COUTINHO , GOMES PEREIRA PAULO ROBERTO , CECON PAULO ROBERTO
Published: April 2007

This work aims to study the effect of the nutrient contents in the leaves of corn on the incidence of Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) and Dalbulus maidis (Delong & Wolcott) (Homoptera: Cicadellidae). The treatments were represented by unfertilized corn plants and corn plants fertilized with 250 kg of the formulation 4‐14‐8 (N‐P‐K) +100 kg of ammonium sulfate (AS)/ha and 500 kg of the formulation 4‐14‐8 (N‐P‐K) +200 kg of AS/ha, arranged in randomized blocks with four replicates. Attacks by S. frugiperda and D. maidis were higher as the nitrogen, sulfur, calcium and copper content in the leaves of corn increased. The effects of calcium and copper found in this study were not consistent with that of lower susceptibility associated with higher levels of these nutrients mentioned in the literature. We believe that there was a cumulative effect of the nutrients altogether, building up a nutritiously better vegetable which in turn had less reserve for defense, or that the content of both nutrients in the leaves were not high enough to induce such effects.
Host‐herbivore studies of Stenoscepa sp. (Orthoptera: Pyrgomorphidae), a high‐Ni herbivore of the South African Ni hyperaccumulator Berkheya coddii (Asteraceae)
Authors: BOYD ROBERT S. , DAVIS MICHEAL A. , WALL MICHAEL A. , BALKWILL KEVIN
Published: April 2007

Nymphs of Stenoscepa sp. feed on leaves of the Ni hyperaccumulator Berkheya coddii at serpentine sites in Mpumalanga Province, South Africa. These sites contain Ni hyperaccumulators, Ni accumulators, and plants with Ni concentrations in the normal range. We conducted studies to: (i) determine the whole‐body metal concentration of nymphs (including those starved to empty their guts); (ii) compare Stenoscepa sp. nymphs against other grasshoppers in the same habitat for whole‐body metal concentrations; and (iii) compare the suitability of Ni hyperaccumulator and Ni accumulator plants as food sources for Stenoscepa sp. and other grasshoppers. Stenoscepa nymphs had extremely high whole‐body Ni concentrations (3 500 μg Ni/g). This was partly due to food in the gut, as starved insects contained less Ni (950 μg Ni/g). Stenoscepa nymphs survived significantly better than other grasshoppers collected from either a serpentine or a non‐serpentine site when offered high‐Ni plants as food. In a host preference test among four Berkheya species (two Ni hyperaccumulators and two Ni accumulators), Stenoscepa sp. preferred leaves of the Ni hyperaccumulator species. A preference experiment using leaves of three Senecio species (of which one species, Senecio coronatus, was represented by both a Ni hyperaccumulator and a Ni accumulator population) showed that Stenoscepa sp. preferred Ni accumulator Senecio coronatus leaves to all other choices. We conclude that Stenoscepa sp. is extremely Ni‐tolerant. Stenoscepa sp. nymphs prefer leaves of hyperaccumulator Berkheya species, but elevated Ni concentration alone does not determine their food preference. We suggest that the extremely high whole‐body Ni concentration of Stenoscepa nymphs may affect food web relationships in these serpentine communities.
Worker laying in leafcutter ant Acromyrmex subterraneus brunneus (Formicidae, Attini)
Authors: CAMARGO ROBERTO S. , FORTI LUIZ C. , LOPES JULIANE F. S. , NORONHA NEWTON C. , OTTATI ANGELO L. T.
Published: April 2007

We studied the process of offspring production in queenless colonies of Acromyrmex subterraneus brunneus, and particularly evaluated the ovary development of workers as a function of their age. For this, subcolonies were set up and evaluated at different periods of isolation from the queen (2, 4 and 6 months), besides individually labeled age groups. The subcolonies were assessed according to offspring production and ovaries containing oocytes or not. The evaluations showed worker oviposition and development of males originating from worker‐laid eggs. At 2 months’absence of the queen, eggs and larvae were found, with eggs in a higher proportion than larvae. After 4 months, the proportion of eggs had reduced while larvae had increased, and a pupa was found in one subcolony. At 6 months, besides a higher share of larvae, one pupa and one adult male were found. Dissection of workers revealed ovaries containing oocytes during the periods of evaluation. Only a group of medium‐sized and large workers, 23.3%, 20.9% and 37.5% of the population from each period assessed in queenless subcolonies respectively, presented developed oocytes in the ovary. The same was observed in colonies with a queen, with 17.6%, 19.6% and 7.8% of the group of dissected workers from each time period, respectively. With respect to worker age, we observed by dissection of the ovary, that the greatest percentage of individuals with ovarioles containing oocytes occurred at 45 days (6 weeks) up to 90 days (12 weeks). These results probably are associated with the workers reproduction and the laying of trophic and reproductive eggs in colonies with and without a queen; these eggs have distinct functions in each situation.
An Incremental Adaptive Procedure for Viscoelastic Contact Problems
Authors: Mahmoud Fatin F. , El-Shafei Ahmed G. , Attia Mohamed A.
Published: April 2007

Contact pressure distribution throughout the contact interface has a vital role on the tribological aspects of the contact systems. Generally, contact of deformable bodies is a nonlinear problem. Viscoelastic materials have a time-dependent response, since both viscous and elastic characteristics depend on time. Such types of materials have the capability of storing and dissipating energy. When at least one of the contacting bodies is made of a viscoelastic material, contact problems become more difficult, and a nonlinear time-dependent contact problem is obtained. The objective of this paper is to develop an incremental adaptive computational model capable of handling quasistatic viscoelastic frictionless contact problems. The Wiechert model, as an effective model capable of describing both creep and relaxation phenomena, is adopted to simulate the linear behavior of viscoelastic materials. The resulting constitutive integral equations are linearized and, therefore, complications that arise during the direct integration of these equations, specially with contact problems, are avoided. In addition, the incremental convex programming method is adopted and modified to accommodate the contact problem of viscoelastic bodies. The Lagrange multiplier method is adopted to enforce the contact constraints. Two different contact problems are presented to demonstrate the efficient applicability of the proposed model.
An Elastic Adhesion Model for Contacting Cylinder and Perfectly Wetted Plane in the Presence of Meniscus
Authors: Peng Y. F. , Li G. X.
Published: April 2007

The present research concerns the elastic contacting adhesion of a cylinder with a perfectly wetted plane in the presence of a meniscus. The Laplace pressure due to the meniscus is simplified utilizing Maugis–Dugdale approximation. Then the Baney and Hui solution and its extension are used to solve the adhesive interaction of the cylinder and the plane. Simulations of the relationship between the adhesive contact radius and the applied normal load are performed, and the influence of the relative humidity on the relationship is also discussed.
Elastic–Plastic Multi-Asperity Contact Analysis of Cylinder-on-Flat Configuration
Authors: Sabelkin V. , Mall S.
Published: April 2007

The contact interaction between a rough cylindrical body (i.e., with asperities) and a deformable smooth flat was investigated using the finite-element analysis. Analysis included both elastic–plastic deformation and friction. Further, the effects of several parameters of rough surface on the evolution of the contact area with increasing contact load were investigated. These were radius, number, constraint, and placement of asperities. Contact area of rough surface is smaller than its counterpart of smooth surface, and this decrease depends on number, radius, constraint, and placement of asperities. The elastic material behavior results in considerably smaller contact area than that from elastic–plastic material behavior. The evolution of contact area with increasing contact load is of the complex nature with elastic–plastic material deformation since the yielded region widens and/or deepens with increasing load depending on number, radius, and constraint of asperities. The effect of constraint on the asperity depends upon its nature (i.e., from either sides or one side) and radius of the asperity. The effects of these several parameters on the contact area versus applied load relationships are expressed in the graphical form as well as in terms of equations wherever possible.
A Multi-Scale System Analysis and Verification for Improved Contact Fatigue Life Cycle of a Cam-Roller System
Authors: Hua D. Y. , Farhang K. , Seitzman L. E.
Published: April 2007

Surface distress in the form of contact fatigue is encountered in cam-roller systems. The contact fatigue appears to be initiated at micrometer-scale subsurface region. High stress is a result of the macro-scale requirement on the cam-roller motion event that produces high contact loads due to inertia of the roller and its follower link. Sliding of the roller and its impact onto the cam surface further compounds the detrimental effect of contact load. While conventionally a Hertz contact stress analysis can be used in ascertaining contact stress and maximum subsurface von Mises stress, it generally underestimates the stress when compared to the micrometer-scale subsurface stresses due to the presence of surface roughness. Contact analyses of cam and roller with rough surfaces are performed to examine the effects of two surface treatments. These involve surface finishing process in which a surface is rendered smooth, and the addition of a coating to the roller surface. Measurements of such cam and roller surfaces are used in micro-contact analysis module of a Surface Distress Analytical Toolkit to examine the effect of surface finish and coating on maximum subsurface stress. It is found that smooth surface provides a 53% reduction in maximum subsurface stress. The analysis also shows that the addition of coating further reduces subsurface stress nearly 7%. The impact of the combined treatment of the surface is an increase in contact fatigue life of the cam-roller system by nearly two orders of magnitude. The above findings are confirmed by laboratory tests using six rollers with various degrees of finishing processes, and with and without addition of coating to the surfaces. Examination of the rollers indicates a general improvement in roller performance due to addition of coating. Most notably, the combination of finishing process and coating was found to provide the best contact fatigue life since the corresponding rollers showed no observable wear even after testing for 2161h, or the same number of cycles accumulated over about 500,000 truck miles.
Energy imparted‐based estimates of the effect of overscanning on adult and pediatric patient effective doses from multi‐slice computed tomography
Authors: Theocharopoulos Nicholas , Damilakis John , Perisinakis Kostas , Gourtsoyiannis Nicholas
Published: April 2007

In the present study effective dose values normalized to computed tomography dose index measured free in air were calculated for adult, newborn, 1, 5, 10 and 15 year old patients regarding scans of the head, chest, abdomen, pelvis, abdomen and pelvis, and trunk, using the energy imparted method. The effect of overscanning on patient doses was accounted for, and normalized doses are provided for varying beam collimation, pitch and reconstruction slice width values. The contribution of overscanning depends on patient age, anatomic region imaged, acquisition and reconstruction settings. For a head scan it constitutes 15% of the adult effective dose and 24% of the effective dose to a newborn but for an abdomen scan it may be as high as 58% for a newborn and 31% for an adult. The ratios of normalized pediatric doses relative to that for adults for helical scans depend not only on age but also on acquisition and reconstruction parameters, because of variations in the relative distance between the primary beam and the radiosensitive tissues/organs of the body. Regarding scans of the trunk, pediatric doses are up to a factor of 2.5 times higher compared to adult doses (abdominal scans), whereas for scans of the head up to a factor of 1.5. Increasing the pitch value of helical scans while maintaining the same effective mAs setting, and hence noise levels, leads to an increase in patient doses which depends on age, body region, scan and reconstruction parameters. The % difference between doses at pitch 1.5 and pitch 1 is more pronounced in the abdominal region (14% increase for adults) and in young patients (31% in a newborn and 18% in a 10 year old patient) and it is minimal in head scans (4% increase in newborns and 1% in adults). If multiple body regions are to be imaged, doses to adults can be reduced by up to 15% and 36% to children by performing single long‐range scans. Scanning adult patients at instead of , results in a 32% reduction in effective dose from head scans and 38% for scans of the torso. The corresponding reduction for a 5 year old patient is 31% for the head and 37% for the trunk. Due to the combined overbeaming and overscanning effect the collimation is more dose effective in the head mode and the collimation in the body mode. Provided data enable informed design of examination protocols, calculation of effective dose values and familiarization with the technical features of multi‐detector technology.
Inversion with early photons
Authors: Turner Gordon M. , Soubret Antoine , Ntziachristos Vasilis
Published: April 2007

Optical tomography using early photons can improve resolution and reduce the ill‐posed nature of the inversion problem. In this work we use projection experimental data to investigate the inversion performance of three commonly used numerical inversion methods: the random algebraic reconstruction technique (rART), singular value decomposition (SVD), and the conjugate‐gradient‐type method LSQR. Results are contrasted to each other and the effects of different photon propagation models are also investigated. We find that all methods perform adequately given appropriate regularization parameters, and that an experimentally measured photon weight function yields superior results over two approximate weights that have been previously used.
BOLD FMRI integration into radiosurgery treatment planning of cerebral vascular malformations
Authors: Stancanello Joseph , Cavedon Carlo , Francescon Paolo , Causin Francesco , Avanzo Michele , Colombo Federico , Cerveri Pietro , Ferrigno Giancarlo , Uggeri Fulvio
Published: April 2007

Functional magnetic resonance imaging (fMRI) is used to distinguish areas of the brain responsible for different tasks and functions. It is possible, for example, by using fMRI images, to identify particular regions in the brain which can be considered as “functional organs at risk” (fOARs), i.e., regions which would cause significant patient morbidity if compromised. The aim of this study is to propose and validate a method to exploit functional information for the identification of fOARs in CyberKnife (Accuray, Inc., Sunnyvale, CA) radiosurgery treatment planning; in particular, given the high spatial accuracy offered by the CyberKnife system, local nonrigid registration is used to reach accurate image matching. Five patients affected by arteriovenous malformations (AVMs) and scheduled to undergo radiosurgery were scanned prior to treatment using computed tomography (CT), three‐dimensional (3D) rotational angiography (3DRA), T2 weighted and blood oxygenation level dependent echo planar imaging MRI. Tasks were chosen on the basis of lesion location by considering those areas which could be potentially close to treatment targets. Functional data were superimposed on 3DRA and CT used for treatment planning. The procedure for the localization of fMRI areas was validated by direct cortical stimulation on and tumor patients undergoing conventional surgery. Treatment plans studied with and without considering fOARs were significantly different, in particular with respect to both maximum dose and dose volume histograms; consideration of the fOARs allowed quality indices of treatment plans to remain almost constant or to improve in four out of five cases compared to plans with no consideration of fOARs. In conclusion, the presented method provides an accurate tool for the integration of functional information into AVM radiosurgery, which might help to minimize undesirable side effects and to make radiosurgery less invasive.
Influence of monitor chamber calibration on Virtual Wedge™ dosimetrya)
Authors: Malkoske K. E. , Nakonechny K. D.
Published: April 2007

We have investigated the influence of the linear accelerator (LINAC) monitor chamber calibration on the dosimetry of Siemens Virtual Wedge™ (VW.) The doses delivered in the three phases of wedge delivery (initial gap, sweep portion, and open field) utilize the ionization current generated in two dose monitoring ion chambers (MONITOR 1 and MONITOR 2) in the LINAC to control the wedge delivery. We intentionally offset the calibration of each of these chambers by and observed up to a 13% change in the dose along the wedge profile for a beam at a field size of . If the calibration of one of the two dose monitoring chambers changed independently then the relative dose at points along the wedge profile were affected. Furthermore, the percentage change in dose varied across the wedge profile thereby affecting the wedge angle as well as the central axis wedge factor. We also present equations for calculating the change in dose at a position along the wedge profile as a function of monitor chamber calibration. A comparison with measurement showed that our theoretical predictions were accurate to within . The equations have proven useful tools in evaluating periodic drifts in VW dosimetry.
Intraoperative cone‐beam CT for correction of periaxial malrotation of the femoral shaft: A surface‐matching approach
Authors: Khoury Amal , Whyne Cari M. , Daly Michael , Moseley Douglas , Bootsma Greg , Skrinskas Tomas , Siewerdsen Jeffrey , Jaffray David
Published: April 2007

Limb length, alignment and rotation can be difficult to determine in femoral shaft fractures. Shaft axis rotation is particularly difficult to assess intraoperatively. Femoral malpositioning can cause deformity, pain and secondary degenerative joint damage. The aim of this study is to develop an intraoperative method based on cone‐beam computed tomography (CBCT) to guide alignment of femoral shaft fractures. We hypothesize that bone surface matching can predict malrotation even with severe comminution. A cadaveric femur was imaged at 16 femoral periaxial malrotations ( to 60.1°). The images were processed resulting in an unwrapped bone surface plot consisting of a pattern of ridges and valleys. Fracture gaps were simulated by removing midline CT slices. The gaps were reconstituted by extrapolating the existing proximal and distal fragments to the midline of the fracture. The two bone surfaces were then shifted to align bony features. Periaxial malrotation was accurately assessed using surface matching (, slope 1.0). The largest mean error was 2.20° and the average difference between repeated measurements was 0.49°. CBCT can provide intraoperative high‐resolution images with a large field of view. This quality of imaging enables surface matching algorithms to be utilized even with large areas of comminution.
Influence of overscanning on normalized effective doses calculated for pediatric patients undergoing multidetector CT examinations
Authors: Tzedakis Antonis , Damilakis John , Perisinakis Kostas , Karantanas Apostolos , Karabekios Spiros , Gourtsoyiannis Nicholas
Published: April 2007

The purpose of this study was to evaluate the effect of overscanning on normalized effective dose for pediatric patients undergoing multidetector‐computed tomography (CT) examinations. Five commercially available mathematical anthropomorphic phantoms representing newborn, 1‐, 5‐, 10‐, and 15‐year‐old patients and the Monte Carlo N‐Particle (MCNP, version 4C2) radiation transport code were employed in the current study to simulate pediatric CT exposures. For all phantoms, axial and helical examinations at tube voltage were simulated. Scans performed at were also simulated. Sex‐specific normalized effective doses were estimated for four standard CT examinations i.e., head‐neck, chest, abdomen‐pelvis, and trunk, for all pediatric phantoms. Data for both axial and helical mode acquisition were obtained. In the helical mode, overscanning was taken into account. The validity of the Monte Carlo results was verified by comparison with dose data obtained using thermoluminescence dosimetry and a physical pediatric anthropomorphic phantom simulating a 10‐year‐old child. In all cases normalized effective dose values were found to increase with increasing overscanning. The percentage differences in normalized data between axial and helical scans may reach 43%, 70%, 36%, and 26% for head‐neck, chest, abdomen‐pelvis, and trunk studies, respectively. Normalized data for female pediatric patients was in general higher compared to male patients for all ages, examined regions, and overscanning values. For both male and female children, the normalized effective dose values were reduced as the age was increased. For the same typical exposure conditions, dose values decreased when lower tube voltage was used; for a 1‐year‐old child, for example, the effective dose was 3.8 times lower when instead of was used. Normalized data for the estimation of effective dose to pediatric patients undergoing standard axial and helical CT examinations on an multidetector CT system were calculated. This data was found to depend strongly on CT acquisition mode and exposure parameters as well as patient age and sex. The effective dose from a pediatric CT scan performed in axial mode was always considerably lower compared to the corresponding scan performed in helical mode, due to the additional tissue regions exposed to the primary beam in helical examinations as a result of overscanning.
Accuracy and stability of positioning in radiosurgery: Long term results of the Gamma Knife system
Authors: Heck Bernhard , Jess‐Hempen Anja , Kreiner Hans Jürg , Schöpgens Hans , Mack Andreas
Published: April 2007

The primary aim of this investigation was to determine the long term overall accuracy of an irradiation position of Gamma Knife systems. The mechanical accuracy of the system as well as the overall accuracy of an irradiation position was examined by irradiating radiosensitive films. To measure the mechanical accuracy, the GafChromic® film was fixed by a special tool at the unit center point (UCP). For overall accuracy the film was mounted inside a phantom at a target position given by a two‐dimensional cross. Its position was determined by CT or MRI scans, a treatment was planned to hit this target by use of the standard planning software and the radiation was finally delivered. This procedure is named “system test” according to DIN 6875‐1 and is equivalent to a treatment simulation. The used GafChromic® films were evaluated by high resolution densitometric measurements. The Munich Gamma Knife UCP coincided within : ; ; to the center of dose distribution. There was no trend in the measured data observed over more than ten years. All measured data were within a sphere of radius. When basing the target definition in the system test on MRI scans, we obtained an overall accuracy of an irradiation position in the direction of and in the direction . When a CT‐based target definition was used, we measured distances in direction and in direction , respectively. These results were compared with those obtained with a Gamma Knife equipped with an automatic positioning system (APS) by use of a different phantom. This phantom was found to be slightly less accurate due to its mechanical construction and the soft fixation into the frame. The phantom related position deviation was found to be about , and therefore the measured accuracy of the APS Gamma Knife was evidently less precise by additional . These measurements demonstrate that an irradiation position defined by a CT scan can be hit within the intrinsic system precision. In radiosurgery with the Gamma Knife, a fixation with the Leksell stereotactic frame is applied. As this frame is considered to add no further uncertainties due to patient movements, the measured accuracy applies to a real patient treatment situation. The major contribution to the overall accuracy of an irradiation position is given by the MRI scans.
Pulmonary nodule registration in serial CT scans based on rib anatomy and nodule template matching
Authors: Shi Jiazheng , Sahiner Berkman , Chan Heang‐Ping , Hadjiiski Lubomir , Zhou Chuan , Cascade Philip N. , Bogot Naama , Kazerooni Ella A. , Wu Yi‐Ta , Wei Jun
Published: April 2007

An automated method is being developed in order to identify corresponding nodules in serial thoracic CT scans for interval change analysis. The method uses the rib centerlines as the reference for initial nodule registration. A spatially adaptive rib segmentation method first locates the regions where the ribs join the spine, which define the starting locations for rib tracking. Each rib is tracked and locally segmented by expectation‐maximization. The ribs are automatically labeled, and the centerlines are estimated using skeletonization. For a given nodule in the source scan, the closest three ribs are identified. A three‐dimensional (3D) rigid affine transformation guided by simplex optimization aligns the centerlines of each of the three rib pairs in the source and target CT volumes. Automatically defined control points along the centerlines of the three ribs in the source scan and the registered ribs in the target scan are used to guide an initial registration using a second 3D rigid affine transformation. A search volume of interest (VOI) is then located in the target scan. Nodule candidate locations within the search VOI are identified as regions with high Hessian responses. The initial registration is refined by searching for the maximum cross‐correlation between the nodule template from the source scan and the candidate locations. The method was evaluated on 48 CT scans from 20 patients. Experienced radiologists identified 101 pairs of corresponding nodules. Three metrics were used for performance evaluation. The first metric was the Euclidean distance between the nodule centers identified by the radiologist and the computer registration, the second metric was a volume overlap measure between the nodule VOIs identified by the radiologist and the computer registration, and the third metric was the hit rate, which measures the fraction of nodules whose centroid computed by the computer registration in the target scan falls within the VOI identified by the radiologist. The average Euclidean distance error was . Only two pairs had an error larger than . The average volume overlap measure was Eighty‐three of the 101 pairs had ratios larger than 0.5, and only two pairs had no overlap. The final hit rate was .
Photon spectrometry for the determination of the dose‐rate constant of low‐energy photon‐emitting brachytherapy sources
Authors: Chen Zhe Jay , Nath Ravinder
Published: April 2007

Accurate determination of dose‐rate constant for interstitial brachytherapy sources emitting low‐energy photons has remained a challenge in radiation dosimetry because of the lack of a suitable absolute dosimeter for accurate measurement of the dose rates near these sources. Indeed, a consensus value of taken as the arithmetic mean of the dose‐rate constants determined by different research groups and dosimetry techniques has to be used at present for each source model in order to minimize the uncertainties associated with individual determinations of . Because the dosimetric properties of a source are fundamentally determined by the characteristics of the photons emitted by the source, a new technique based on photon spectrometry was developed in this work for the determination of dose‐rate constant. The photon spectrometry technique utilized a high‐resolution gamma‐ray spectrometer to measure source‐specific photon characteristics emitted by the low‐energy sources and determine their dose‐rate constants based on the measured photon‐energy spectra and known dose‐deposition properties of mono‐energetic photons in water. This technique eliminates many of the difficulties arising from detector size, the energy dependence of detector sensitivity, and the use of non‐water‐equivalent solid phantoms in absolute dose rate measurements. It also circumvents the uncertainties that might be associated with the source modeling in Monte Carlo simulation techniques. It was shown that the estimated overall uncertainty of the photon spectrometry technique was less than 4%, which is significantly smaller than the reported 8–10% uncertainty associated with the current thermo‐luminescent dosimetry technique. In addition, the photon spectrometry technique was found to be stable and quick in determination after initial setup and calibration. A dose‐rate constant can be determined in less than two hours for each source. These features make it ideal to determine the dose‐rate constant of each source model from a larger and more representative sample of actual sources and to use it as a quality assurance resource for periodic monitoring of the constancy of for brachytherapy sources used in patient treatments.
Biophotonics: Visions for Better Health Care
Authors: Wang Brian
Published: April 2007

Biophotonics: Visions for Better Health Care Popp Jürgen and Strehle Marion 622 pp., ISBN 3‐527‐40622‐0, Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, 2006. $165.00 (hardcover).
Quantitative Analysis in Nuclear Medicine Imaging
Authors: Madsen Mark
Published: April 2007

Quantitative Analysis in Nuclear Medicine Imaging Zaidi Habib 538 pp., Springer‐Verlag, 2006. $125.00. ISBN 9780387238548.
Nonstoichiometric Dislocation Cores in α-Alumina
Authors: Shibata N. , Chisholm M. F. , Nakamura A. , Pennycook S. J. , Yamamoto T. , Ikuhara Y.
Published: April 2007

Little is known about dislocation core structures in oxides, despite their central importance in controlling electrical, optical, and mechanical properties. It has often been assumed, on the basis of charge considerations, that a nonstoichiometric core structure could not exist. We report atomic-resolution images that directly resolve the cation and anion sublattices in alumina (α-Al
2
O
3
). A dissociated basal edge dislocation is seen to consist of two cores; an aluminum column terminates one partial, and an oxygen column terminates the second partial. Each partial core is locally nonstoichiometric due to the excess of aluminum or oxygen at the core. The implication for mechanical properties is that the mobile high-temperature dislocation core structure consists of two closely spaced partial dislocations. For basal slip to occur, synchronized motion of the partials on adjacent planes is required.
Agreement between Self- and Clinician-Collected Specimen Results for Detection and Typing of High-Risk Human Papillomavirus in Specimens from Women in Gugulethu, South Africa
Authors: Jones Heidi E. , Allan Bruce R. , van de Wijgert Janneke H. H. M. , Altini Lydia , Taylor Sylvia M. , de Kock Alana , Coetzee Nicol , Williamson Anna-Lise
Published: April 2007

We assessed the agreement in detection of high-risk human papillomavirus (HPV), as well as specific HPV types, between self- and clinician-obtained specimens for 450 women over 18 years of age attending a community health center in Gugulethu, South Africa. Both self-collected swabs and tampons had high agreement with clinician-obtained brushes when the Roche Reverse Line Blot Assay (RLBA) was used (for swabs, 86% concordance, with a kappa statistic [κ] of 0.71; for tampons, 89% concordance, with κ of 0.75). Agreement was lower, although still fair, with the Digene Hybrid Capture 2 test (HC2), with κ higher for swabs than for tampons (for swabs, 81% concordance, with κ of 0.61; for tampons, 82% concordance, with κ of 0.55). Low-risk HPV types were nearly two times more common in self-collected specimens than in clinician-collected specimens tested by RLBA. All 15 women diagnosed with high-grade lesions by cytology tested positive for high-risk HPV with clinician-collected specimens tested by RLBA and HC2, while 11 out of 15 tested positive with self-collected specimens by HC2 and 5 out of 6 tested positive by RLBA. Self-collected specimens can provide valid specimens for HPV testing using nucleic acid amplification tests, although a few cytological abnormalities may be missed.
Neutralizing Antibody Responses in Acute Human Immunodeficiency Virus Type 1 Subtype C Infection
Authors: Gray E. S. , Moore P. L. , Choge I. A. , Decker J. M. , Bibollet-Ruche F. , Li H. , Leseka N. , Treurnicht F. , Mlisana K. , Shaw G. M. , Karim S. S. Abdool , Williamson C. , Morris L.
Published: April 2007

The study of the evolution and specificities of neutralizing antibodies during the course of human immunodeficiency virus type 1 (HIV-1) infection may be important in the discovery of possible targets for vaccine design. In this study, we assessed the autologous and heterologous neutralization responses of 14 HIV-1 subtype C-infected individuals, using envelope clones obtained within the first 2 months postinfection. Our data show that potent but relatively strain-specific neutralizing antibodies develop within 3 to 12 months of HIV-1 infection. The magnitude of this response was associated with shorter V1-to-V5 envelope lengths and fewer glycosylation sites, particularly in the V1-V2 region. Anti-MPER antibodies were detected in 4 of 14 individuals within a year of infection, while antibodies to CD4-induced (CD4i) epitopes developed to high titers in 12 participants, in most cases before the development of autologous neutralizing antibodies. However, neither anti-MPER nor anti-CD4i antibody specificity conferred neutralization breadth. These data provide insights into the kinetics, potency, breadth, and epitope specificity of neutralizing antibody responses in acute HIV-1 subtype C infection.
Lassa Virus Infection in Experimentally Infected Marmosets: Liver Pathology and Immunophenotypic Alterations in Target Tissues
Authors: Carrion Ricardo , Brasky Kathleen , Mansfield Keith , Johnson Curtis , Gonzales Monica , Ticer Anysha , Lukashevich Igor , Tardif Suzette , Patterson Jean
Published: April 2007

Lassa virus causes thousands of deaths annually in western Africa and is considered a potential biological weapon. In an attempt to develop a small nonhuman primate model of Lassa fever, common marmosets were subcutaneously inoculated with Lassa virus strain Josiah. This inoculation resulted in a systemic disease with clinical and morphological features mirroring those in fatal human Lassa infection: fever, weight loss, high viremia and viral RNA load in tissues, elevated liver enzymes, and severe morbidity between days 15 and 20. The most prominent histopathology findings included multifocal hepatic necrosis with mild inflammation and hepatocyte proliferation, lymphoid depletion, and interstitial nephritis. Cellular aggregates in regions of hepatocellular necrosis were largely composed of HAM56-positive macrophages, devoid of CD3-positive and CD20-positive cells, and characterized by marked reductions in the intensity of HLA-DP, DQ, DR staining. A marked reduction in the major histocompatibility complex class II expression was also observed in the lymph nodes. Immunophenotypic alterations in spleen included reductions in overall numbers of CD20-positive and CD3-positive cells and the disruption of lymphoid follicular architecture. These findings identify the common marmoset as an appropriate model of human Lassa fever and present the first experimental evidence that replication of Lassa virus in tissues is associated with alterations that would be expected to impair adaptive immunity.
SPECIFIC FACTORS AND HECKSCHER-OHLIN: AN INTERTEMPORAL BLEND
Authors: JONES RONALD W.
Published: April 2007

A blend of the Specific Factors and Heckscher-Ohlin models can be fashioned, making use of some of the ideas in the earlier vintage capital literature. At any given time, production in many sectors reflects past decisions to create sector-specific capital in those sectors. In addition, current capital formation can be focused on one or two best sectors depicted by the Hicksian composite unit-value isoquant. Thus, international trade concentrates current investment decisions and yet allows a variety of goods to be produced.
FOREIGN LABOR AND ECONOMIC GROWTH POLICY OPTIONS FOR SINGAPORE
Authors: HUI WENG-TAT , HASHMI AAMIR RAFIQUE
Published: April 2007

Prior to the Asian economic crisis in 1997, Singapore's official projected medium-term GDP growth target was set at 7% per annum. Since then, the targeted growth rate has been reduced to 5%. This paper examines the implications of the 5% growth target on the labor requirements of the Singapore economy. It is shown that the projected resident labor force will not be able to keep pace with the increased labor demand and the share of foreigners in the labor force will increase significantly even under the most favorable scenario. Some implications of the increased dependence on foreign labor in Singapore are discussed. With permanent immigration fixed at the current level, various policy options and their effects on the demand for foreign labor are considered. These include improving labor productivity, raising the total fertility rate, increasing labor force participation of older workers and lowering the targeted rate of economic growth.
1/f NOISE DUE TO THE RETURN STATISTICS OF MOBILE POINT DEFECTS IN EXTRINSIC SEMICONDUCTOR MATERIALS
Authors: GRÜNEIS FERDINAND
Published: April 2007

We investigate fixed dopants in the presence of mobile point defects like foreign atoms or vacancies. A mobile defect entering the first Bohr radius RB of a dopant will modulate the generation-recombination process. The times a defect walks inside or outside RB are shown to be power-law distributed giving rise to 1 / fb noise. The predicted Hooge coefficient αdef depends on RB, on the normalized fluctuations of charge carriers and on the number of charge carriers compared to lattice sites; our model suggests that the magnitude of 1/ f noise can be decreased at will by increasing the ionization of dopants.
ELECTRON SPIN DYNAMICS THROUGH FERROMAGNETIC QUANTUM POINT CONTACT
Authors: AWAD ALLA ATTIA A. , ALY ARAFA H. , PHILLIPS ADEL H.
Published: April 2007

We study spin-dependent tunneling through ferromagnetic quantum point contact. It was found that both the current and the conductance show increasing oscillatory fluctuations with the variation of Fermi energy and contact area at different temperatures. These oscillations are due to polarization inversion at the incoming of each new sub-band and increasing transmission probability through the higher sub-bands. The results are found to be in good concordance with those in the literature.