bluuebunny/crossref_metadata_2025 huggingface dataset:
CARCASS AND MEAT QUALITY OF YEARLING BULLS AS AFFECTED BY THE USE OF CLENBUTEROL AND STEROID HORMONES COMBINED WITH DEXAMETHASONE
Authors: MONSÓN FRANCO , SAÑUDO CARLOS , BIANCHI GIANNI , ALBERTÍ PERE , HERRERA ANTONIO , ARIÑO AGUSTÍN
Published: May 2007

Twelve yearling bulls were assigned to one of three groups: (1) control with no treatment; (2) implanted with hormones; or (3) fed with the β‐agonist clenbuterol. Groups b and c were also fed with dexamethasone during the finishing period. After slaughter, six muscles aged for 1, 3, 7, 14 and 21 days at 4C were used for the analyses of the meat quality. Clenbuterol‐fed animals presented the highest muscle percentage (74.72%) and diameter B of the loin (8.05 cm), whereas hormone‐implanted animals had the highest bone percentage (16.12%) and lower percentage of muscle (68.15%). Meat from animals fed with clenbuterol tended to have higher water‐holding capacity than from the other groups. Clenbuterol‐fed animals also presented the lowest CIE a* (redness) values. Instrumental texture was affected by the growth promoters used, although it varied with muscle or aging time. The use of clenbuterol brought about tougher meat, but the combination with dexamethasone might decrease toughness.
ENZYMATIC MODIFICATION THROUGH MICROBIAL TRANSGLUTAMINASE ENHANCES THE VISCOSITY OF STIRRED YOGURT
Authors: JAROS DORIS , HEIDIG CORA , ROHM HARALD
Published: May 2007

Among others, dairy proteins and, especially, the caseins are well‐suited substrates for enzymatic modification by microbial transglutaminase. Apart from studies on chemically acidified dairy gels, some research has been performed on the impact of cross‐linking on rheology and texture of set yogurt. In this study, stirred yogurt was produced from skim milk that was incubated with transglutaminase. Dry matter of the base milk and starter cultures were varied at two levels, and the products were analyzed after 2 and 9 d of storage. The rheological measurements revealed a significant but shear rate‐dependent impact of enzymatic cross‐linking on the properties of stirred yogurt. Under steady‐shear conditions, the viscosity‐enhancing effect was more pronounced at low shear rates or shear stresses, pointing on enhanced interactions among the aggregated proteins in the products made from cross‐linked milk. The cross‐link‐induced viscosity‐enhancing effect diminished with increasing shear rates.

PRACTICAL APPLICATIONS

Microbial transglutaminase represents an interesting tool for texture modification of protein‐containing foods. The formation of new covalent cross‐links among and within protein molecules generates considerable changes in the technofunctional properties of the final products. Acid gels, such as yogurt, made from enzyme‐treated milk are characterized by reduced syneresis and improved viscosity. A better understanding of the enzyme‐catalyzed impact on the rheological behavior of stirred yogurt may help create new products with interesting properties.
METHODOLOGIES FOR SYMMETRICAL‐FLOW FIELD‐FLOW FRACTIONATION ANALYSIS OF POLYMERIC GLUTENIN
Authors: DAQIQ LAILA , FELLOWS CHRISTOPHER M. , BEKES FERENC , LEES EDITH
Published: May 2007

Symmetrical‐flow field‐flow fractionation analysis was used to estimate the molecular size distribution (MSD) of glutenin from Australian wheat cultivars. The high molecular weight end of the MSD is important for predicting dough quality, but is difficult to measure by most characterization methods. Two parameters were considered to quantify the high molecular part of the distribution. A measure of the ratio of the rates of chain extension and termination, Λ, was adopted from methods introduced for synthetic polymers. The molecular weight below which 99% of total signal intensity should be observed, A99, was also estimated. It was hypothesized that Λ would not be sensitive to extraction conditions, but it was found to be dependent on the sonication time used in isolation of the glutenin. Λ and A99 showed strong positive correlations with mixing time and maximum resistance to extension, parameters related to dough quality.

PRACTICAL APPLICATIONS

The goal of this work was to develop structure–property relations allowing prediction of dough quality properties important in bread manufacture (e.g., maximum resistance of dough to extension) from measurements of the size distribution of the glutenins present in the flour. Two parameters were derived enabling such predictions that do not require accurate measurement of the peak size or measurement of the entire glutenin size distribution. These parameters may be of use in assessing wheat cultivars for bread and pasta manufacture.
Diaspora as Process: (De)Constructing Boundaries
Authors: Mavroudi Elizabeth
Published: May 2007

This article discusses different conceptualisations of diaspora, as bounded, unbounded and as a process, in order to help highlight the useful role diaspora can play in explorations and (de)constructions of nation‐state, community and identity boundaries. There are two main ways in which diaspora has been theorised. The first theorises diaspora in relation to defined homeland‐orientated ethnic groups and identities and the second theorises diaspora in relation to fluid, non‐essentialised, nomadic identities. This article argues that it is necessary to look beyond such conceptualisations of diaspora as nomadic/fluid (unbounded) or homeland‐centred/ethnic‐religious (bounded). This article advocates a flexible use of diaspora as process that is able to examine the dynamic negotiations of collective, strategic and politicised identities based around constructions of ‘sameness’ and the homeland, as well as individual identities that are malleable, hybrid and multiple. It stresses that it is within this notion of diaspora as process that geographers, with their emphasis on place, space and time, have an important role to play.
Optimization of the Fermentation Medium for Alpha‐Galactosidase Production from Aspergillus foetidus ZU‐G1 Using Response Surface Methodology
Authors: Liu Caiquin , Ruan Hui , Shen Huafeng , Chen Qihe , Zhou Bing , Li Yi , He Guoqing
Published: May 2007

ABSTRACT:  The optimization of fermentation medium for alpha‐galactosidase production by Aspergillus foetidus ZU‐G1 was investigated in shaker flask fermentation. A one‐factor‐at‐a‐time experiment was used to screen the preferable nutriment (carbon sources, nitrogen sources, and essential elements) for alpha‐galactosidase production. A fractional factorial design was used to screen the main 5 factors, soybean meal, wheat bran, KH2PO4, FeSO4·7H2O, and the medium initial pH, that affected the production of alpha‐galactosidase. The central composite experimental design was further adopted to derive a statistical model for optimizing the composition of the fermentation medium. The experimental results showed that the optimum fermentation medium for alpha‐galactosidase production by Aspergillus foetidus ZU‐G1 was composed of 3.2% soybean meal (w/v), 2% wheat bran (w/v), 0.1% KH2PO4 (w/v), and 0.05% FeSO4·7H2O (w/v); initial medium pH was 6.31. The results further predicted that alpha‐galactosidase activity reached 64.75 U/mL after 96‐h incubation in this medium, which was approximately 7 times higher than that incubated in the nonoptimized medium. The time course of alpha‐galactosidase production in the optimized medium composition was also carried out to validate the model.
A Comparative Study of Acrylamide Formation Induced by Microwave and Conventional Heating Methods
Authors: Yuan Y. , Chen F. , Zhao G.‐H. , Liu J. , Zhang H.‐X. , Hu X.‐S.
Published: May 2007

ABSTRACT:  In this study, the formation of acrylamide upon treatment with microwave and conventional heating, boiling, or frying was investigated in both Asn/Fru and Asn/Glc model systems and in potato chips. Acrylamide levels were analyzed by HPLC method, which was confirmed by HPLC‐MS/MS. Present results in model systems showed that pH value had a complex influence on the formation of acrylamide in the 2 systems during both microwaving (600 W) and boiling (120 ± 1 oC). At pH < 8.0, acrylamide content increased with increasing the pH value, reaching the maximum at pH 8.0 whereas acrylamide content decreased with the increase of pH. Regardless of pH and heating methods, acrylamide content generally increased with increasing treatment time. Surprisingly, all present results showed that microwave heating not only induced acrylamide formation in the 2 model systems but also facilitated more acrylamide to be formed as compared to the boiling method at identical pH and treatment time. At pH 4.0, 8.0, and 10.0, the larger the microwave power, the more the acrylamide content. Consistent with the above observation, treatment of potato chips with microwave heating for 2.5 to 3.5 min in the range 550 to 750 W similarly resulted in acrylamide formation. The highest acrylamide content was formed by 750 W microwave treatment as 0.897 ± 0.099 mg/kg, which was significantly higher than that produced by traditional frying (180 ± 1oC), 0.645 ± 0.035 mg/kg (P < 0.05).
Effect of Natural Antioxidants on Oxidative Stability of Cooked, Refrigerated Beef and Pork
Authors: Rojas M.C. , Brewer M.S
Published: May 2007

ABSTRACT:  The effect of grape seed extract (GS; 0.01% and 0.02%), oleoresin rosemary (OR; 0.02%) and water‐soluble oregano extract (WS; 0.02%) on oxidative and color stability of cooked beef and pork patties stored at 4 °C for 8 d was determined. Fresh beef or pork lean and trim were ground, mixed (30% fat), and divided into 5 portions. Antioxidants mixed with salt (2%) were added. Patties were formed, cooked to an internal temperature of 71 °C, overwrapped in PVC, and stored at 4 °C. Lipid oxidation, assessed using thiobarbituric acid reactive substances (TBARS) and sensory evaluation, instrumental and visual color, and pH were determined after 0, 2, 4, 6, and 8 d. Based on TBARS values and off‐odors associated with lipid oxidation such as rancidity, wet cardboard (for beef patties), and grassy (for beef and pork patties), grape seed extract resulted in the best antioxidant activity in both meat species. It did not change instrumental color measures of redness, yellowness, or color intensity, and appeared to reduce visual green discoloration in beef patties. The higher GS concentration (0.02%) exhibited more antioxidant activity than the lower concentration (0.01%). Therefore, grape seed extract at 0.02% has the potential to reduce oxidative rancidity and improve shelf life of refrigerated cooked beef and pork patties.
An allometric function to fit leg‐loop harnesses to terrestrial birds
Authors: Naef‐Daenzer Beat
Published: May 2007

Harnesses are indispensable for a long‐term attachment of instruments to animals, particularly birds. The exact fit is crucial for both the reliability of the tags and the animals’ health and natural behaviour. Using data from 19 bird species ranging from 8–400 g, I present an allometric function to calculate the dimension of leg‐loop harnesses for birds on the basis of body mass data. The model greatly facilitates determining the correct loop span for new species without time‐consuming experiments. More importantly, the equation permits calculation of the excess span that is required for tagging juvenile, still growing birds.
The impact of temporal inaccuracies on 4DCT image quality
Authors: Mutaf Y. D. , Antolak J. A. , Brinkmann D. H.
Published: May 2007

Accurate delineation of target volumes is one of the critical components contributing to the success of image‐guided radiotherapy treatments and several imaging modalities are employed to increase the accuracy in target identification. Four‐dimensional (4D) techniques are incorporated into existing radiation imaging techniques like computed tomography (CT) to account for the mobility of the target volumes. However, these methods in some cases introduce further inaccuracies in the target delineation when further quality assurance measures are not implemented. A source of commonly observed inaccuracy is the misidentification of the respiration cycles and resulting respiration phase assignments used in the construction of the 4D patient model. The aim of this work is to emphasize the importance of optimal respiration phase assignment during the 4DCT image acquisition process and to perform a quantitative assessment of the effect of inaccurate phase assignments on the overall image quality. The accuracy of the phase assignment was assessed by comparison with an independent calculation of the respiration phases. Misplaced phase assignments manifest themselves as deformations and artifacts in reconstructed images. These effects are quantified as volumetric discrepancies in the localization of target objects represented by spherical phantoms. Measurements are performed using a fully programmable motion phantom designed and built at Mayo Clinic (Rochester, MN). Implementation of a case based independent check and correction procedure is also demonstrated with emphasis on the use of this procedure in the clinical environment. Review of clinical 4D scans performed in this institution showed discrepancies in the phase assignments in about 40% of the cases when compared to our independent calculations. It is concluded that for improved image reconstruction, an independent check of the sorting procedure should be performed for each clinical 4DCT case.
Slit design for efficient and accurate MTF measurement at megavoltage x‐ray energies
Authors: Sawant Amit , Antonuk Larry , El‐Mohri Youcef
Published: May 2007

Empirical determination of the modulation transfer function (MTF) for analog and digital megavoltage x‐ray imagers is a challenging task. The most common method used to determine MTF at megavoltage x‐ray energies employs a long, narrow slit formed by two parallel, metal blocks in order to form a “slit beam.” In this work, a detailed overview of some of the important considerations of slit design is presented. Based on these considerations, a novel, compact slit, using thick tungsten blocks, was designed. The prototype slit was configured to attach to the accessory slot of the gantry of a linear accelerator, which greatly simplified the measurement process. Measurements were performed to determine the presampling MTF at for an indirect detection active matrix flat panel imager prototype previously developed for megavoltage imaging applications. In addition, the effects of two important slit design parameters, material type and thickness, on the accuracy of MTF determination were investigated via a Monte Carlo‐based theoretical study. Empirically determined MTFs obtained from the prototype slit closely match those from an earlier, less compact slit design based on thick steel blocks. The results of the Monte Carlo‐based theoretical studies indicate that the prototype slit achieves close‐to‐ideal performance in terms of accurately determining the MTF by virtue of practically 100% beam attenuation in regions other than the slit gap. Furthermore, the theoretical results suggest that it may be possible to achieve even further reductions in slit thickness without compromising measurement accuracy.
Relative output factor and beam profile measurements of small radiation fields with an L‐alanine/K‐Band EPR minidosimeter
Authors: Abrego Felipe Chen , Calcina Carmen Sandra Guzmán , de Almeida Adelaide , de Almeida Carlos Eduardo , Baffa Oswaldo
Published: May 2007

The performance of an L‐alanine dosimeter with millimeter dimensions was evaluated for dosimetry in small radiation fields. Relative output factor (ROF) measurements were made for , , , , square fields and for 5‐, 10‐, 20‐, ‐diam circular fields. In beam profile (BP) measurements, only , , square fields and 10‐, 20‐, ‐diam circular fields were used. For square and circular field irradiations, Varian/Clinac 2100, and a Siemens/Mevatron linear accelerators were used, respectively. For a batch of 800 L‐alanine minidosimeters (miniALAs) the average mass was , the diameter was , and the length was . A K‐Band electron paramagnetic resonance (EPR) spectrometer was used for recording the spectrum of irradiated and nonirradiated miniALAs. To evaluate the performance of the miniALAs, their ROF and BP results were compared with those of other types of detectors, such as an ionization chamber (PTW ), a miniTLD (LiF: Mg,Cu,P), and Kodak/X‐Omat V radiographic film. Compared to other dosimeters, the ROF results for miniALA show differences of up to 3% for the smallest fields and 7% for the largest ones. These differences were within the miniALA experimental uncertainty ( at ). For BP measurements, the maximum penumbra width difference observed between miniALA and film (10%–90% width) was less than for square fields and within for circular fields. These penumbra width results indicate that the spatial resolution of the miniALA is comparable to that of radiographic film and its dimensions are adequate for the field sizes used in this experiment. The K‐Band EPR spectrometer provided adequate sensitivity for assessment of miniALAs with doses of the order of tens of Grays, making this dosimetry system (K‐Band/miniALA) a potential candidate for use in radiosurgery dosimetry.
Gamma Knife 3‐D dose distribution near the area of tissue inhomogeneities by normoxic gel dosimetry
Authors: Isbakan Fatih , Ülgen Yekta , Bilge Hatice , Ozen Zeynep , Agus Onur , Buyuksarac Bora
Published: May 2007

The accuracy of the Leksell GammaPlan®, the dose planning system of the Gamma Knife Model‐B, was evaluated near tissue inhomogeneities, using the gel dosimetry method. The lack of electronic equilibrium around the small‐diameter gamma beams can cause dose calculation errors in the neighborhood of an air‐tissue interface. An experiment was designed to investigate the effects of inhomogeneity near the paranosal sinuses cavities. The homogeneous phantom was a spherical glass balloon of diameter, filled with MAGIC gel; i.e., the normoxic polymer gel. Two hollow PVC balls of radius, filled with gas, represented the air cavities inside the inhomogeneous phantom. For dose calibration purposes, gel‐containing vials were irradiated at predefined doses, and then scanned in a MR unit. Linearity was observed between the delivered dose and the reciprocal of the T2 relaxation time constant of the gel. Dose distributions are the results of a single shot of irradiation, obtained by collimating all 201 cobalt sources to a known target in the phantom. Both phantoms were irradiated at the same dose level at the same coordinates. Stereotactic frames and fiducial markers were attached to the phantoms prior to MR scanning. The dose distribution predicted by the Gamma Knife planning system was compared with that of the gel dosimetry. As expected, for the homogeneous phantom the isodose diameters measured by the gel dosimetry and the GammaPlan® differed by 5% at most. However, with the inhomogeneous phantom, the dose maps in the axial, coronal and sagittal planes were spatially different. The diameters of the 50% isodose curves differed 43% in the axis and 32% in the axis for the axial plane; by 44% in the axis and 24% in the axis for the coronal plane; and by 32% in the axis and 42% in the axis for the sagittal plane. The lack of ability of the GammaPlan® to predict the rapid dose fall off, due to the air cavities behind or near the lesion led to an overestimation of the dose that was actually delivered. Clinically, this can result in underdosing of lesions near tissue inhomogeneities in patients under treatment.
Direct aperture optimization for online adaptive radiation therapy
Authors: Mestrovic Ante , Milette Marie‐Pierre , Nichol Alan , Clark Brenda G. , Otto Karl
Published: May 2007

This paper is the first investigation of using direct aperture optimization (DAO) for online adaptive radiation therapy (ART). A geometrical model representing the anatomy of a typical prostate case was created. To simulate interfractional deformations, four different anatomical deformations were created by systematically deforming the original anatomy by various amounts (0.25, 0.50, 0.75, and ). We describe a series of techniques where the original treatment plan was adapted in order to correct for the deterioration of dose distribution quality caused by the anatomical deformations. We found that the average time needed to adapt the original plan to arrive at a clinically acceptable plan is roughly half of the time needed for a complete plan regeneration, for all four anatomical deformations. Furthermore, through modification of the DAO algorithm the optimization search space was reduced and the plan adaptation was significantly accelerated. For the first anatomical deformation , the plan adaptation was six times more efficient than the complete plan regeneration. For the 0.50 and deformations, the optimization efficiency was increased by a factor of roughly 3 compared to the complete plan regeneration. However, for the anatomical deformation of , the reduction of the optimization search space during plan adaptation did not result in any efficiency improvement over the original (nonmodified) plan adaptation. The anatomical deformation of demonstrates the limit of this approach. We propose an innovative approach to online ART in which the plan adaptation and radiation delivery are merged together and performed concurrently—adaptive radiation delivery (ARD). A fundamental advantage of ARD is the fact that radiation delivery can start almost immediately after image acquisition and evaluation. Most of the original plan adaptation is done during the radiation delivery, so the time spent adapting the original plan does not increase the overall time the patient has to spend on the treatment couch. As a consequence, the effective time allotted for plan adaptation is drastically reduced. For the 0.25, 0.5, and anatomical deformations, the treatment time was increased by only 2, 4, and , respectively, as compared to no plan adaptation. For the anatomical deformation of the time increase was substantially larger. The anatomical deformation of represents an extreme case, which is rarely observed for the prostate, and again demonstrates the limit of this approach. ARD shows great potential for an online adaptive method with minimal extension of treatment time.
Energy dependence of commercially available diode detectors for in‐vivo dosimetry
Authors: Saini Amarjit S. , Zhu Timothy C.
Published: May 2007

The energy dependence of commercially available diode detectors was measured for nominal accelerating potential ranging between and . The measurements were performed in a liquid water phantom at depth for collimator setting and source‐to‐detector distance of . The response (nC/Gy) was normalized to beam after corrections for the dose rate and temperature dependences for each diode. The energy dependence, calculated by taking the percent difference between the maximum and minimum sensitivity normalized to beam, varied by 39% for the ‐type Isorad Red, 26% for the ‐type Isorad Electron, 19% for the QED Red (‐type), 15% for the QED Electron (‐type), 11% for the QED Blue (‐type), and 6% for the EDP10 diode for nominal accelerating potential between and . It varied by 34% for the Isorad‐3 Gold #1 and #2, 35% for the Veridose Green, 15% for the Veridose Yellow, 9% for the Veridose Electron, 21% for the ‐type QED Gold, 24% for the ‐type QED Red, 3% for the , 2% for the PFD (photon field detector), 7% for the , and 16% for the for nominal accelerating potential between and . The magnitude of the energy dependence is verified by Monte Carlo simulation. We concluded that the energy dependence does not depend on whether the diode is ‐ or ‐type but rather depends mainly on the material around the die such as the buildup and the geometry of the buildup material. As a result, the value of the energy dependence can vary for each individual diode depending on the actual geometry and should be used with caution.
Validity of model approximations for receptor‐ligand kinetics in nuclear medicine
Authors: Salinas Cristian A. , Muzic Raymond F. , Saidel Gerald M.
Published: May 2007

An appropriate mathematical model is required for quantitative analysis of high affinity radioligands as direct or surrogate probes to measure receptor distribution, affinity, concentration, binding potential, and endogenous or exogenous ligand occupancy levels. For studies with positron emission tomography (PET) or single photon emission computed tomography (SPECT), the receptor‐ligand compartment model has been well established and widely used. This pharmacokinetic model is represented mathematically by a set of nonlinear ordinary differential equations. Variations of models for PET and SPECT account for radioactive decay differently. These are not equivalent and entail assumptions or approximations that may be not appreciated. In this study, a general form of the model is presented and compared with others with various approximations, which are valid only under specific conditions. The various approximate formulations were analytically compared to the exact model to identify the terms that were neglected in the approximate formulations. The extent to which the approximations impact the model solutions was assessed by computer simulations based on numerical solutions to each set of equations. Specifically, each model formulation was tested using three simulated injection protocols representing a typical PET experiment, a typical SPECT experiment, and an extreme experiment where both the injected activity and the specific activity were very high. No significant differences were found among the output of the three model formulations when the PET and SPECT injection protocols were tested. The only conditions that produced significant differences occurred when the specific activity and the administered activity were simultaneously very high. These conditions, however, have little practical relevance to experimentally achievable conditions due to radiation dose and specific activity of radiopharmaceuticals.
Monte Carlo study of Si diode response in electron beams
Authors: Wang Lilie L. W. , Rogers David W. O.
Published: May 2007

Silicon semiconductor diodes measure almost the same depth‐dose distributions in both photon and electron beams as those measured by ion chambers. A recent study in ion chamber dosimetry has suggested that the wall correction factor for a parallel‐plate ion chamber in electron beams changes with depth by as much as 6%. To investigate diode detector response with respect to depth, a silicon diode model is constructed and the water/silicon dose ratio at various depths in electron beams is calculated using EGSnrc. The results indicate that, for this particular diode model, the diode response per unit water dose (or water/diode dose ratio) in both 6 andelectron beams is flat within 2% versus depth, from near the phantom surface to the depth of(with calculation uncertainty). This suggests that there must be some other correction factors for ion chambers that counter‐balance the large wall correction factor at depth in electron beams. In addition, the beam quality and field‐size dependence of the diode model are also calculated. The results show that the water/diode dose ratio remains constant within 2% over the electron energy range from 6 to. The water/diode dose ratio does not depend on field size as long as the incident electron beam is broad and the electron energy is high. However, for a very small beam sizeand low electron energy, the water/diode dose ratio may decrease by more than 2% compared to that of a broad beam.
Monte Carlo study on the imaging performance of powder phosphor screens under x‐ray excitation: Comparison with screens
Authors: Liaparinos Panagiotis F. , Kandarakis Ioannis S. , Cavouras Dionisis A. , Delis Harry B. , Panayiotakis George S.
Published: May 2007

(LSO) scintillator is a relatively new luminescent material which has been successfully applied in positron emission tomography systems. Since it has been recently commercially available in powder form, it could be of value to investigate its performance for use in x‐ray projection imaging as both physical and scintillating properties indicate a promising material for such applications. In the present study, a custom and validated Monte Carlo simulation code was used in order to examine the performance of LSO, under diagnostic radiology (mammography and general radiography) conditions. The Monte Carlo code was based on a model using Mie scattering theory for the description of light attenuation. Imaging characteristics, related to image brightness, spatial resolution and noise of LSO screens were predicted using only physical parameters of the phosphor. The overall performance of LSO powder phosphor screens was investigated in terms of the: (i) quantum detection efficiency (ii) emitted K‐characteristic radiation (iii) luminescence efficiency (iv) modulation transfer function (v) Swank factor and (vi) zero‐frequency detective quantum efficiency [DQE(0)]. Results were compared to the traditional rare‐earth (GOS) phosphor material. The relative luminescence efficiency of LSO phosphor was found inferior to that of GOS. This is due to the lower intrinsic conversion efficiency of LSO (0.08 instead of 0.15 of GOS) and the relatively high light extinction coefficient of this phosphor ( instead of for GOS). However, the property of increased light extinction combined with the rather sharp angular distribution of scattered light photons (anisotropy factor for LSO instead of 0.494 for GOS) reduce lateral light spreading and improve spatial resolution. In addition, LSO screens were found to exhibit better x‐ray absorption as well as higher signal to noise transfer properties in the energy range from up to (e.g. at and for , instead of 0.58 for GOS). The results indicate that certain optical properties of LSO (optical extinction coefficient, scattering anisotropy factor) combined with the relatively high x‐ray coefficients, make this material a promising phosphor which, under appropriate conditions, could be considered for use in x‐ray projection imaging detectors.
Monte Carlo evaluation of the AAA treatment planning algorithm in a heterogeneous multilayer phantom and IMRT clinical treatments for an Elekta SL25 linear accelerator
Authors: Sterpin E. , Tomsej M. , De Smedt B. , Reynaert N. , Vynckier S.
Published: May 2007

The Anisotropic Analytical Algorithm (AAA) is a new pencil beam convolution/superposition algorithm proposed by Varian for photon dose calculations. The configuration of AAA depends on linear accelerator design and specifications. The purpose of this study was to investigate the accuracy of AAA for an Elekta SL25 linear accelerator for small fields and intensity modulated radiation therapy (IMRT) treatments in inhomogeneous media. The accuracy of AAA was evaluated in two studies. First, AAA was compared both with Monte Carlo (MC) and the measurements in an inhomogeneous phantom simulating lung equivalent tissues and bone ribs. The algorithm was tested under lateral electronic disequilibrium conditions, using small fields . Good agreement was generally achieved for depth dose and profiles, with deviations generally below 3% in lung inhomogeneities and below 5% at interfaces. However, the effects of attenuation and scattering close to the bone ribs were not fully taken into account by AAA, and small inhomogeneities may lead to planning errors. Second, AAA and MC were compared for IMRT plans in clinical conditions, i.e., dose calculations in a computed tomography scan of a patient. One ethmoid tumor, one orophaxynx and two lung tumors are presented in this paper. Small differences were found between the dose volume histograms. For instance, a 1.7% difference for the mean planning target volume dose was obtained for the ethmoid case. Since better agreement was achieved for the same plans but in homogeneous conditions, these differences must be attributed to the handling of inhomogeneities by AAA. Therefore, inherent assumptions of the algorithm, principally the assumption of independent depth and lateral directions in the scaling of the kernels, were slightly influencing AAA's validity in inhomogeneities. However, AAA showed a good accuracy overall and a great ability to handle small fields in inhomogeneous media compared to other pencil beam convolution algorithms.
Specialized Inhibitory Synaptic Actions Between Nearby Neocortical Pyramidal Neurons
Authors: Ren Ming , Yoshimura Yumiko , Takada Naoki , Horibe Shoko , Komatsu Yukio
Published: May 2007

We found that, in the mouse visual cortex, action potentials generated in a single layer-2/3 pyramidal (excitatory) neuron can reliably evoke large, constant-latency inhibitory postsynaptic currents in other nearby pyramidal cells. This effect is mediated by axo-axonic ionotropic glutamate receptor–mediated excitation of the nerve terminals of inhibitory interneurons, which connect to the target pyramidal cells. Therefore, individual cortical excitatory neurons can generate inhibition independently from the somatic firing of inhibitory interneurons.
Beating the Standard Quantum Limit with Four-Entangled Photons
Authors: Nagata Tomohisa , Okamoto Ryo , O'Brien Jeremy L. , Sasaki Keiji , Takeuchi Shigeki
Published: May 2007

Precision measurements are important across all fields of science. In particular, optical phase measurements can be used to measure distance, position, displacement, acceleration, and optical path length. Quantum entanglement enables higher precision than would otherwise be possible. We demonstrated an optical phase measurement with an entangled four-photon interference visibility greater than the threshold to beat the standard quantum limit—the limit attainable without entanglement. These results open the way for new high-precision measurement applications.
Pyroclastic Activity at Home Plate in Gusev Crater, Mars
Authors: Squyres S. W. , Aharonson O. , Clark B.C. , Cohen B. A. , Crumpler L. , de Souza P. A. , Farrand W. H. , Gellert R. , Grant J. , Grotzinger J. P. , Haldemann A. F. C. , Johnson J. R. , Klingelhöfer G. , Lewis K. W. , Li R. , McCoy T. , McEwen A. S. , McSween H. Y. , Ming D. W. , Moore J. M. , Morris R. V. , Parker T. J. , Rice J. W. , Ruff S. , Schmidt M. , Schröder C. , Soderblom L. A. , Yen A.
Published: May 2007

Home Plate is a layered plateau in Gusev crater on Mars. It is composed of clastic rocks of moderately altered alkali basalt composition, enriched in some highly volatile elements. A coarsegrained lower unit lies under a finer-grained upper unit. Textural observations indicate that the lower strata were emplaced in an explosive event, and geochemical considerations favor an explosive volcanic origin over an impact origin. The lower unit likely represents accumulation of pyroclastic materials, whereas the upper unit may represent eolian reworking of the same pyroclastic materials.
Germanium Nanowire Growth Below the Eutectic Temperature
Authors: Kodambaka S. , Tersoff J. , Reuter M. C. , Ross F. M.
Published: May 2007

Nanowires are conventionally assumed to grow via the vapor-liquid-solid process, in which material from the vapor is incorporated into the growing nanowire via a liquid catalyst, commonly a low–melting point eutectic alloy. However, nanowires have been observed to grow below the eutectic temperature, and the state of the catalyst remains controversial. Using in situ microscopy, we showed that, for the classic Ge/Au system, nanowire growth can occur below the eutectic temperature with either liquid or solid catalysts at the same temperature. We found, unexpectedly, that the catalyst state depends on the growth pressure and thermal history. We suggest that these phenomena may be due to kinetic enrichment of the eutectic alloy composition and expect these results to be relevant for other nanowire systems.
Quantum Coherent Tunable Coupling of Superconducting Qubits
Authors: Niskanen A. O. , Harrabi K. , Yoshihara F. , Nakamura Y. , Lloyd S. , Tsai J. S.
Published: May 2007

To do large-scale quantum information processing, it is necessary to control the interactions between individual qubits while retaining quantum coherence. To this end, superconducting circuits allow for a high degree of flexibility. We report on the time-domain tunable coupling of optimally biased superconducting flux qubits. By modulating the nonlinear inductance of an additional coupling element, we parametrically induced a two-qubit transition that was otherwise forbidden. We observed an on/off coupling ratio of 19 and were able to demonstrate a simple quantum protocol.
Reducing Endogenous Tau Ameliorates Amyloid ß-Induced Deficits in an Alzheimer's Disease Mouse Model
Authors: Roberson Erik D. , Scearce-Levie Kimberly , Palop Jorge J. , Yan Fengrong , Cheng Irene H. , Wu Tiffany , Gerstein Hilary , Yu Gui-Qiu , Mucke Lennart
Published: May 2007

Many potential treatments for Alzheimer's disease target amyloid-β peptides (Aβ), which are widely presumed to cause the disease. The microtubule-associated protein tau is also involved in the disease, but it is unclear whether treatments aimed at tau could block Aβ-induced cognitive impairments. Here, we found that reducing endogenous tau levels prevented behavioral deficits in transgenic mice expressing human amyloid precursor protein, without altering their high Aβ levels. Tau reduction also protected both transgenic and nontransgenic mice against excitotoxicity. Thus, tau reduction can block Aβ- and excitotoxin-induced neuronal dysfunction and may represent an effective strategy for treating Alzheimer's disease and related conditions.
Genetic and Antigenic Diversity of the Surface Protective Antigen Proteins of
Erysipelothrix rhusiopathiae
Authors: To Ho , Nagai Shinya
Published: May 2007

The surface protective antigen (Spa) protein of
Erysipelothrix rhusiopathiae
has been shown to be highly immunogenic and is a potential candidate for a new vaccine against erysipelas. In this study, we cloned and sequenced
spa
genes from all
E. rhusiopathiae
serovar reference strains as well as from a serovar 18 strain which was not classified as any species in the genus
Erysipelothrix.
Sequence analysis revealed that the Spa proteins could be classified into three molecular species, including SpaA, which was previously found in serovars 1a and 2, and the newly designated SpaB and SpaC proteins. The SpaA protein is produced by
E. rhusiopathiae
serovars 1a, 1b, 2, 5, 8, 9, 12, 15, 16, 17, and N, the SpaB protein is produced by
E. rhusiopathiae
serovars 4, 6, 11, 19, and 21, and the SpaC protein is produced only by serovar 18. The amino acid sequence similarity was high among members of each Spa type (96 to 99%) but low between different Spa types (∼60%). The greatest diversity in Spa proteins was found in the N-terminal half of the molecule (50 to 57% similarity), which was shown to be involved in immunoprotection. Coinciding with this, immunoblot analysis revealed that rabbit antisera specific to each Spa reacted strongly with the homologous Spa protein but weakly with heterologous Spa proteins. A mouse cross-protection study showed that the three recombinant Spa (rSpa) proteins elicited complete protection against challenge with homologous strains but that the level of protection against challenge with heterologous strains varied depending on the rSpa protein used for immunization. Our study is the first to demonstrate sequence and antigenic diversity in Spa proteins and to indicate that rSpaC may be the most promising antigen for use as a vaccine component because of its broad cross-protectiveness.
Detection of Mutations Conferring Resistance to Linezolid in
Enterococcus
spp. by Fluorescence In Situ Hybridization
Authors: Werner Guido , Bartel Melanie , Wellinghausen Nele , Essig Andreas , Klare Ingo , Witte Wolfgang , Poppert Sven
Published: May 2007

A fluorescence in situ hybridization (FISH) assay was established to detect linezolid resistance (conferred by the mutation 2576G>T in the gene coding for the 23 string of the ribosomal RNA) in enterococci. The assay was evaluated with 106
Enterococcus
isolates; it showed a sensitivity of 100% for the detection of phenotypic resistance and was even able to identify a single mutated allele in phenotypically linezolid-susceptible isolates.
Detection and Identification ofLeishmaniaSpecies from Clinical Specimens by Using a Real-Time PCR Assay and Sequencing of the CytochromebGene
Authors: Foulet Françoise , Botterel Françoise , Buffet Pierre , Morizot Gloria , Rivollet Danièle , Deniau Michèle , Pratlong Francine , Costa Jean-Marc , Bretagne Stéphane
Published: May 2007

Visceral and cutaneous leishmaniases are heterogenous entities. TheLeishmaniaspecies that a given patient harbors usually cannot be determined clinically, and this identification is essential to prescribe the best species-specific therapeutic regimen. Our diagnosis procedure includes a real-time PCR assay targeted at the 18S rRNA gene, which detects allLeishmaniaspecies but which is not specific for a givenLeishmaniaspecies. We developed a species identification based on sequencing of the cytochromeb(cytb) gene directly from the DNA extracted from the clinical specimen. The sequences were analyzed using the Sequence Analysis/Seqscape v2.1 software (Applied Biosystems). This software is designed to automatically identify the closest sequences from a reference library after analysis of all known or unknown polymorphic positions. The library was built with theLeishmaniacytbgene sequences available in GenBank. Fifty-three consecutive real-time PCR-positive specimens were studied for species identification. The cytbgene was amplified in the 53 specimens. Sequencing resulted in the identification of six different species with ≥99% identity with the reference sequences over 872 nucleotides. The identification was obtained in two working days and was in accordance with the multilocus enzyme electrophoresis identification when available. Real-time PCR followed by sequencing of the cytbgene confirmed the diagnosis of leishmaniasis and rapidly determined the infecting species directly from the clinical specimen without the need for the isolation of parasites. This technique has the potential to significantly accelerate species-adapted therapeutic decisions regarding treatment of leishmaniasis.
Entry of
Rice Dwarf Virus
into Cultured Cells of Its Insect Vector Involves Clathrin-Mediated Endocytosis
Authors: Wei Taiyun , Chen Hongyan , Ichiki-Uehara Tamaki , Hibino Hiroyuki , Omura Toshihiro
Published: May 2007

Electron microscopy revealed that the entry of
Rice dwarf virus
(RDV) into insect vector cells involved endocytosis via coated pits. The treatment of cells with drugs that block receptor-mediated or clathrin-mediated endocytosis significantly reduced RDV infectivity. However, the drug that blocks caveola-mediated endocytosis had a negligible effect on such infection. Infection was also inhibited when cells had been pretreated with bafilomycin A1, which interferes with acidification of endosomes. Moreover, immunofluorescence staining indicated that the virus is internalized into early endosomes. Together, our data indicate that RDV enters insect vector cells through receptor-mediated, clathrin-dependent endocytosis and is sequestered in early endosomes.
The F Gene of Rodent Brain-Adapted Mumps Virus Is a Major Determinant of Neurovirulence
Authors: Lemon Ken , Rima Bertus K. , McQuaid Stephen , Allen Ingrid V. , Duprex W. Paul
Published: May 2007

Prior to the introduction of live-attenuated vaccines, mumps virus (MuV) was the leading cause of virus-induced meningitis. Although vaccination has been effective at controlling the disease, the use of insufficiently attenuated strains has been associated with high rates of aseptic meningitis in vaccinees. The molecular basis of MuV attenuation is poorly understood, and no reliable molecular markers of virulence have been identified. In this study, reverse genetics has been used to identify molecular determinants of MuV neuropathogenesis. Recombinant viruses, containing the envelope-associated genes from the Kilham (MuVKH) rodent brain-adapted strain of MuV, were generated in the Jeryl Lynn 5 (MuVJL5) vaccine strain background. The syncytium phenotypes of the recombinant viruses on Vero cells differed depending on the source of the fusion (F) and hemagglutinin-neuraminidase (HN) glycoproteins, with heterologous combinations showing either an increase or a decrease in the level of cell fusion compared to that of the homologous parental combinations. This was confirmed by transiently cotransfecting eukaryotic F and HN glycoprotein expression constructs. A Lewis rat model that discriminates between neurovirulent and nonneurovirulent MuV strains based on the extent of hydrocephalus induced in the rat brain after intracerebral inoculation was used to assess the phenotype of the recombinant viruses. Expression of the matrix (M), small hydrophobic (SH), or HN gene in isolation did not confer a neurovirulent phenotype. Expression of the F gene of the neurovirulent strain alone was sufficient to induce significant levels of hydrocephalus. Coexpression of the homologous HN gene led to a marginal increase in the level of hydrocephalus.
Tumor Necrosis Factor Activates a Conserved Innate Antiviral Response to Hepatitis B Virus That Destabilizes Nucleocapsids and Reduces Nuclear Viral DNA
Authors: Puro Robyn , Schneider Robert J.
Published: May 2007

Tumor necrosis factor (TNF) is critical for the control of hepatitis B virus (HBV) in the clinical setting and in model systems. TNF induces noncytopathic suppression and clearance of HBV in animal models, possibly through reduction of viral nucleocapsids, but the mechanism is not well described. Here, we demonstrate the molecular mechanism and broad host range for TNF action against HBV. We show that TNF rapidly blocks HBV replication by promoting destabilization of preexisting cytoplasmic viral nucleocapsids containing viral RNA and DNA, as well as empty nucleocapsids. TNF destabilized human HBV nucleocapsids in a variety of human hepatocytic cell lines and in primary rat hepatocytes and also destabilized duck HBV (DHBV) nucleocapsids in chicken hepatocytic cells. Lysates from TNF-treated uninfected cells also destabilized HBV nucleocapsids in vitro. Moreover, inhibition of DHBV DNA replication by TNF blocks nuclear accumulation of the viral transcription template, maintenance of which is essential for the establishment and maintenance of chronic infection. We show that TNF destabilization of HBV nucleocapsids does not involve ubiquitination or methylation of the viral core protein and is not mediated by the nitric oxide free radical arm of the TNF pathway. These results define a novel antiviral mechanism mediated by TNF against multiple types of HBVs in different species.
Bovine Papillomavirus Type 1 Infection Is Mediated by SNARE Syntaxin 18
Authors: Laniosz Valerie , Nguyen Kha C. , Meneses Patricio I.
Published: May 2007

Events that lead to viral infections include the binding of the virus to the target cells, internalization of the virus into the cells, and the ability of the viral genome to be expressed. These steps are mediated by cellular and viral proteins and are temporally regulated. The papillomavirus capsid consists of two virally encoded capsid proteins, L1 and L2. Much is known about the role of the major capsid protein L1 compared to what is known of the role of the L2 protein. We identified the interaction of the L2 protein with SNARE protein syntaxin 18, which mediates the trafficking of vesicles and their cargo between the endoplasmic reticulum, the
cis
-Golgi compartment, and possibly the plasma membrane. Mutations of L2 residues 41 to 44 prevented the interaction of L2 protein with syntaxin 18 in cotransfection experiments and resulted in noninfectious pseudovirions. In this paper, we describe that syntaxin 18 colocalizes with infectious bovine papillomavirus type 1 (BPV1) pseudovirions during infection but does not colocalize with the noninfectious BPV1 pseudovirions made with an L2 mutant at residues 41 to 44. We show that an antibody against BPV1 L2 residues 36 to 49 (αL2 36-49) binds to in vitro-generated BPV1 pseudoviral capsids and does not coimmunoprecipitate syntaxin 18- and BPV1 L2-transfected proteins. αL2 36-49 was able to partially or completely neutralize infection of BPV1 pseudovirions and genuine virions. These results support the dependence of syntaxin 18 during BPV1 infection and the ability to interfere with infection by targeting the L2-syntaxin 18 interaction and further define the infectious route of BPV1 mediated by the L2 protein.