bluuebunny/crossref_metadata_2025 huggingface dataset:
IHF‐dependent activation of P1 plasmid origin by DnaA
Authors: Fekete Richard A. , Venkova‐Canova Tatiana , Park Kyusung , Chattoraj Dhruba K.
Published: November 2006

In bacteria, many DNA–protein interactions that initiate transcription, replication and recombination require the mediation of DNA architectural proteins such as IHF and HU. For replication initiation, plasmid P1 requires three origin binding proteins: the architectural protein HU, a plasmid‐specific initiator, RepA, and the Escherichia coli chromosomal initiator, DnaA. The two initiators bind in the origin of replication to multiple sites, called iterons and DnaA boxes respectively. We show here that all five known DnaA boxes can be deleted from the plasmid origin provided the origin is extended by about 120 bp. The additional DNA provides an IHF site and most likely a weak DnaA binding site, because replacing the putative site with an authentic DnaA box enhanced plasmid replication in an IHF‐dependent manner. IHF most likely brings about interactions between distally bound DnaA and RepA by bending the intervening DNA. The role of IHF in activating P1 origin by allowing DnaA binding to a weak site is reminiscent of the role the protein plays in initiating the host chromosomal replication.
High temperature acclimation of C4 photosynthesis is linked to changes in photosynthetic biochemistry
Authors: DWYER SIMON A. , GHANNOUM OULA , NICOTRA ADRIENNE , VON CAEMMERER SUSANNE
Published: November 2006

With average global temperatures predicted to increase over the next century, it is important to understand the extent and mechanisms of C4 photosynthetic acclimation to modest increases in growth temperature. To this end, we compared the photosynthetic responses of two C4 grasses (Panicum coloratum and Cenchrus ciliaris) and one C4 dicot (Flaveria bidentis) to growth at moderate (25/20 °C, day/night) or high (35/30 °C, day/night) temperatures. In all three C4 species, CO2 assimilation rates (A) underwent significant thermal acclimation, such that when compared at growth temperatures, A increased less than what would be expected given the strong response of A to short‐term changes in leaf temperature. Thermal photosynthetic acclimation was further manifested by an increase in the temperature optima of A, and a decrease in leaf nitrogen content and leaf mass per area in the high‐ relative to the moderate‐temperature‐grown plants. Reduced photosynthetic capacity at the higher growth temperature was underpinned by selective changes in photosynthetic components. Plants grown at the higher temperature had lower amounts of ribulose‐1,5‐bisphosphate carboxylase/oxygenase and cytochrome f and activity of carbonic anhydrase. The activities of photosystem II (PSII) and phosphenolpyruvate carboxylase were not affected by growth temperature. Chlorophyll fluorescence measurements of F. bidentis showed a corresponding decrease in the quantum yield of PSII (ΦPSII) and an increase in non‐photochemical quenching (ΦNPQ). It is concluded that through these biochemical changes, C4 plants maintain the balance between the various photosynthetic components at each growth temperature, despite the differing temperature dependence of each process. As such, at higher temperatures photosynthetic nitrogen use efficiency increases more than A. Our results suggest C4 plants will show only modest changes in photosynthetic rates in response to changes in growth temperature, such as those expected within or between seasons, or the warming anticipated as a result of global climate change.
Pustular dermatosis caused by fire ant (Solenopsis invicta) stings in a dog
Authors: Conceição Lissandro G. , Haddad Vidal , Loures Fabricia Hallack
Published: November 2006

This paper reports a case of spontaneous fire ant sting dermatitis in canine. The skin lesions consisted of nonfollicular, grouped pustules in the abdominal region. Several fire ants were found attached to the lesional skin. Histopathological findings included an intraepidermal neutrophilic pustule and predominantly neutrophilic interstitial dermatitis. An extensive area of collagen degeneration was also observed below the epidermal pustule. These clinical and histopathological findings are remarkable similar to those observed in fire ant stings in humans.
Three‐dimensional structure of the α‐MSH‐derived candidacidal peptide [Ac‐CKPV]2
Authors: Catania A. , Grieco P. , Randazzo A. , Novellino E. , Gatti S. , Rossi C. , Colombo G. , Lipton J. M.
Published: November 2006

Abstract:  Previous research has shown that the immunomodulatory peptide α‐melanocyte‐stimulating hormone (α‐MSH) and its carboxy‐terminal tripeptide KPV (Lys‐Pro‐Val α‐MSH11−13) have antimicrobial influences. By inserting a Cys‐Cys linker between two units of KPV, we designed the dimer [Ac‐CKPV]2 that showed excellent candidacidal effects in pilot tests and was the subject of further investigations. [Ac‐CKPV]2 was active against azole‐resistant Candida spp. Therefore, the molecule appeared a promising candidate for therapy of fungal infections and was the subject of a structural study. 1H‐NMR and restrained mechanic and dynamic calculations suggest that the peptide adopts an extended backbone structure with a β‐turn‐like structure. These results open a pathway to development of additional novel compounds that have candidacidal effects potentially useful against clinical infections.
Structure–function studies of the functional and binding epitope of the human 37 kDa laminin receptor precursor protein
Authors: Jaseja M. , Mergen L. , Gillette K. , Forbes K. , Sehgal I. , Copié V.
Published: November 2006

Abstract:  Expression of the 37 kDa laminin receptor precursor protein (37LRP) correlates directly with increased invasiveness and the metastatic potential of tumors. The 37LRP matures to a 67 kDa protein which facilitates the binding of cancer cells to basement membranes. The palindrome peptide sequence LMWWML, corresponding to the 173–178‐residue stretch of the human 37LRP sequence, has been identified as the laminin‐1‐binding site. Peptides from 37LRP of species that contain this palindrome‐bind laminin‐1 with high affinity. Nuclear magnetic resonance (NMR) conformational studies have been undertaken on a synthetic 15‐residue peptide (KGAHSVGLMWWMLAR) containing the palindrome to establish the structural basis of this activity. To further correlate the structural data with laminin‐1‐binding function, analogous structural studies were conducted for a similar peptide (RGKHSIGLIWYLLAR) lacking the palindrome, originating from 37LRP sequence of Saccharomyces cerevisiae and exhibiting low laminin‐1‐binding affinity. Finally, in vitro cell invasion assays were performed to investigate the possibility that the laminin‐1‐binding affinity of the peptides influences their inhibitory activity.
CUSTOMER CARE AND THE PUBLIC SERVICE ETHOS
Authors: NEEDHAM CATHERINE E.
Published: November 2006

The Labour governments that have been in power in the UK since 1997 have reconceptualized the public service ethos. In an apparent departure from their Conservative predecessors, Labour ministers have argued that the distinctive culture of public service can enhance rather than impede service quality and deliver high levels of customer care. This article utilizes interviews and content analysis data to explore the ethical dimension of public service, the significance of the language of customer in relation to ethos, and the implications for service delivery of a customer care focus. Case study findings show that a customer orientation is endorsed by politicians and bureaucrats in both central and local government, although there is a lack of clarity about the service manifestations of such a shift in emphasis. Respondents voiced concerns about the viability of customer care in the public sector as well as the sidelining of the political role of citizen.
THE ROLE OF BOUNDARY‐SPANNING MANAGERS IN THE ESTABLISHMENT OF PUBLIC‐PRIVATE PARTNERSHIPS
Authors: NOBLE GARY , JONES ROBERT
Published: November 2006

This article presents the findings of a study examining the roles and behaviours of boundary‐spanning managers during the establishment of voluntary public‐private partnerships (PPPs). It responds to recent calls in the literature to pursue research that incorporates the pivotal contribution of individual actors in the collaborative process, and to set this research within the stage specific context of partnerships. The analysis is located within the theoretical framework of organizational sensemaking. Using a grounded methodology of data collection, coding and analysis within ten Australian and UK PPPs, the study demarcates a four‐stage evolutionary establishment process of PPPs. Within each stage there exists a specific managerial focus in conjunction with one or two main managerial challenges. Boundary‐spanning managers employ various strategies to overcome such challenges within each specific stage, thus ensuring the progressive evolution of the PPP. These foci, challenges and strategies are identified and analysed in the article.
FRAGMENTED BUT FORCEFUL: DUTCH ADMINISTRATIVE SCIENCES AND THEIR INSTITUTIONAL EVOLUTION
Authors: NOORDEGRAAF MIRKO , BRANDSEN TACO , HUITEMA DAVE
Published: November 2006

This article is an attempt by three (relatively) young scholars to make sense of the broad field of public administration (PA), in The Netherlands, with particular emphasis on Dutch administrative sciences. The one essential fact about the Dutch administrative sciences is that they lack a real essence, both in institutional and in paradigmatic terms. They are fragmented – yet forceful. Nevertheless, we will argue, they must recast their position in relation to practitioners and other academics if they are to maintain their strength. We start by highlighting the development of The Netherlands itself, moving on to Dutch public administration and Dutch administrative sciences. We explore the historical Dutch emphasis on ‘pragmatic morality’. After this rough historical overview, we move on to contemporary features of Dutch administrative sciences, features which explain why these sciences have become fragmented, yet forceful – as well as why this force is threatened. We conclude with a perspective on the future of the field and will argue in favour of a renewed emphasis on ‘pragmatic morality’ within scholarly circles.
AMBIGUITY IN POLICY LESSONS: THE AGENCIFICATION EXPERIENCE
Authors: MOYNIHAN DONALD P.
Published: November 2006

The policy transfer literature identifies the importance of context in shaping policy selection. However, countries with distinctly different contexts are pursuing the agencification of the public sector. Why? The solution to this puzzle lies in the ambiguity associated with public management ideas, which allows policy adopters room to interpret management doctrines and experience. The result is that public management ideas that carry the same identifying label can mask variation in the understanding of the policy, the motivation for adoption and in implementation outcomes. The process of interpretation allows policy‐makers in different contexts to: (1) adopt superficially similar policy concepts; (2) overlook negative experiential learning that contradicts the policy doctrine; and (3) adopt policies unsuitable to the national context.
Repetitive Occipital Nerve Blockade for Cervicogenic Headache: Expanded Case Report of 47 Adults
Authors: Naja Zoher M. , El‐Rajab Mariam , Al‐Tannir Mohamad A. , Ziade Fouad M. , Tawfik Omar M.
Published: November 2006

Purpose:  To evaluate the repetitive occipital nerve blocks using a nerve stimulator in the treatment of cervicogenic headache.

Methods:  This prospective noncomparative clinical interventional case‐series study included 47 patients suffering from cervicogenic headache using a repetitive guided occipital nerve blockade.

Results:  Forty‐one patients (87%) required more than one injection to achieve six‐month pain‐relief period. For every three years of headache history, the outcomes demonstrated that a patient needed one additional injection to the basic injection.

Conclusion:  The repeated nerve stimulator‐guided occipital nerve blockade is a treatment mode that may relieve cervicogenic headache with no recurrence for at least six months in addition to alleviation of associated symptoms.
Poly(acrylic acid)–Poly(ethylene oxide) Comb Polymer Effects on BaTiO3 Nanoparticle Suspension Stability
Authors: Kirby Glen H. , Harris Daniel J. , Li Qi , Lewis Jennifer A.
Published: November 2006

We have studied the effects of poly(acrylic acid)–poly(ethylene oxide) (PAA–PEO) comb polymers on the stability of aqueous BaTiO3 nanoparticle suspensions over a wide pH range in the presence and absence of mono‐ and divalent salt species. The comb polymer architecture consists of charge‐neutral PEO teeth attached at random intervals along an ionizable PAA backbone. Potentiometric titrations, light scattering, and turbidity measurements were conducted on pure PAA and PAA–PEO solutions to assess their degree of ionization, radius of hydration, and stability. Adsorption isotherm and rheological measurements were conducted on BaTiO3 nanoparticle suspensions to determine the effectiveness of both PAA and PAA–PEO dispersants. Our observations indicate that the presence of PEO teeth effectively shield the underlying PAA backbone from ion interactions, e.g., counterion‐screening or ion‐bridging effects, thereby allowing PAA–PEO dispersants to impart stability to BaTiO3 nanoparticle suspensions over a wide range of pH, ionic strength, and ion valency conditions where pure PAA fails.
Characterization of High‐Fracture Toughness K‐Fluorrichterite‐Fluorapatite Glass Ceramics
Authors: Mirsaneh Mehdi , Reaney Ian M. , Hatton Paul V. , James Peter F.
Published: November 2006

Stoichiometric K‐fluorrichterite (Glass A) and the same composition with 2 mol% P2O5 added (Glass B) were prepared and then heat‐treated isothermally from 550°–1000°C with 50°C intervals. Samples were characterized using X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The biaxial flexural strength and indentation fracture toughness of heat‐treated glass specimens were also determined for both materials. XRD traces and TEM images showed similar phase evolution and fine microstructures for both systems at ≤950°C, with mica and diopside reacting with residual glass to form K‐fluorrichterite as the temperature was increased from 650°C. However, in Glass B, fluorapatite was also present at >800°C. In contrast, coarser microstructures were observed at 1000°C, with larger K‐fluorrichterite (20 μm) and enstatite (10 μm) crystals in Glasses A and B, respectively. The highest fracture toughness (2.69 ± 0.01 MPa·m1/2) and biaxial strength (242.6 ± 3.6 MPa) were recorded for Glass B heat‐treated at 1000°C. This was attributed to the presence of enstatite coupled with an interlocked lath‐like crystalline microstructure.
Mullite/Alumina Mixtures for Use as Porous Matrices in Oxide Fiber Composites
Authors: Fujita Hiroki , Jefferson George , McMeeking Robert M. , Zok Frank W.
Published: November 2006

Weakly bonded particle mixtures of mullite and alumina are assessed as candidate matrixes for use in porous matrix ceramic composites. Conditions for the deflection of a matrix crack at a fiber‐matrix interface are used to identify the combinations of modulus and toughness of the fibers and the matrix for which damage‐tolerant behavior is expected to occur in the composite. Accordingly, the present study focuses on the modulus and toughness of the particle mixtures, as well as the changes in these properties following aging at elevated temperature comparable to the targeted upper‐use temperature for oxide composites. Models based on bonded particle aggregates are presented, assessed, and calibrated. The experimental and modeling results are combined to predict the critical aging times at which damage tolerance is lost because of sintering at the particle junctions and the associated changes in mechanical properties. For an aging temperature of 1200°C, the critical time exceeds 10 000 h for the mullite‐rich mixtures.
In Situ Characterization of Interfaces between Liquid Tin–Vanadium Alloys and Alumina by Neutron Reflection Spectroscopy
Authors: Winn Andrew J. , Derby Brian , Webster John R. P. , Holt Stephen
Published: November 2006

The composition and structure of interfaces between single crystal Al2O3 (sapphire) samples and liquid Sn–V alloys, containing 1% and 3% V, have been characterized in situ at high temperature using neutron reflection spectroscopy. Measurements made at 900°C are shown to be consistent with a thin (10–25 nm) AlV2O4 layer forming at the solid/liquid interface, with possibly a thinner layer of enhanced V content adjacent to the liquid, to promote wetting. After longer time exposure to temperature this interface layer roughens and a more complex interface structure occurs.
Effect of Rare‐Earth Dopants on Mechanical Properties of Alumina
Authors: Rani D. Amutha , Yoshizawa Y. , Hirao K. , Yamauchi Y.
Published: November 2006

We report here about the effect of rare‐earth dopants on the improvement of room‐temperature mechanical properties of alumina. Rare‐earth ions (RE = Yb3+, Er3+, and La3+) of different ionic radii in a minimum concentration of 1000 ppm were added as dopants individually to high‐purity alumina and densified by pressureless sintering. High strength of about 700 MPa was attained for Yb‐doped alumina sintered at 1400°C. And, high toughness of about 7.0 MPa·m1/2 was attained for Er‐ and La‐doped alumina samples.
Fiber Strength Retention of Lanthanum‐ and Cerium Monazite‐Coated Nextel™ 720
Authors: Boakye Emmanuel E. , Mogilevsky Pavel
Published: November 2006

Nextel™ 720 fibers were coated with LaPO4 and CePO4 monazite. The coatings were applied using washed and unwashed rhabdophane sols derived from La(NO3)3/(NH4)2HPO4 and a washed sol derived from Ce(NO3)3/H3PO4. The coatings were cured in‐line at 900°–1300°C. Multiple coatings were also applied. Fiber strength was retained after coating with washed sols, but not with unwashed sols. These results are consistent with earlier work on LaPO4 monazite fiber coatings derived from La(NO3)3/H3PO4.
Recurrent CXCR4 sequence variation in a girl with WHIM syndrome
Authors: Alapi Krisztina , Erdős Melinda , Kovács Gabriella , Maródi László
Published: November 2006

WHIM (warts‐hypogammaglobulinemia‐infections‐myelokathexis) syndrome is a recently described primary immunodeficiency disorder caused by mutation of the CXCR4 chemokine receptor gene. We report here of a 6.5‐yr‐old girl with bacterial infections, severe chronic neutropenia, and hypogammaglobulinemia. Sequencing the CXCR4 gene revealed a c.1013C>G sequence variant suggesting WHIM syndrome. Recurrent c.1013C>G sequence variant of the CXCR4 gene resulting in p.S338X truncation mutation of this chemokine receptor protein is first reported here.
Emergency department Communication Officer: Response to consumer demand
Authors: Meek Robert , Torsello Sarah
Published: November 2006

Objective:  To determine whether the employment of a Communication Officer (CO) in the ED waiting room improves ED consumer satisfaction with regard to information exchange and general care received in the waiting room.

Methods:  Multifactorial analytic cross sectional survey on convenience samples of ED consumers. Consumers were eligible if they had been in the waiting room for more than 30 min. Comparisons in responses using ordinal regression analysis were made between shifts on which there was no intervention present, where the CO, an educational video or both were present.

Results:  When the CO was present the responses to seven of 10 questions regarding information exchange and general care were significantly improved (all P < 0.01) and three were not. When only the video was running, the responses to none of the 10 questions were significantly improved. The concurrent presence of the video neither enhanced nor detracted from the responses regarding the CO when both were present. Responses to all five questions regarding the CO were positive, and responses to two of three questions regarding the value of the video were positive.

Conclusion:  The presence of a designated CO in the ED waiting room enhances the communication with, and perceptions of general care by ED consumers.
Multislice computed tomographic pulmonary angiography for diagnosing pulmonary embolism in the emergency department: Has the ‘one‐stop shop’ arrived?
Authors: Mountain David
Published: November 2006

Current diagnostic pathways for pulmonary embolism are complex and involve multiple tests. Clinicians await a single diagnostic modality that accurately rules in or out pulmonary embolism and also provides additional diagnostic and prognostic information. Multislice computed tomographic pulmonary angiography (msCTPA) might be that test. msCTPA has good outcomes using current reference standards and can be used as a stand alone test in low risk patients. Additional leg vein imaging should still be performed for higher‐risk patients. CT venography performed immediately after msCTPA has sufficient sensitivity and specificity for proximal deep venous thrombosis to allow a single scan to rule out venous thromboembolism in most patients. Up to 40% of patients have important alternative diagnoses seen on msCTPA. Right ventricular measurements may be calculated from msCTPA data and provide prognostic information for patients with severe PE. This may replace the need for echocardiography in the future. msCTPA provides a safe single radiological investigation for diagnosing PE for most patients, after risk stratification and D‐dimer testing. A pathway is provided for msCTPA use in the management of PE in the ED.
On burnout and other demons
Authors: Cannon Marianne
Published: November 2006

A personal perspective on the subject of burnout in emergency physicians. Causes, identification of and potential pitfalls as well as possible remedies are discussed.
Randomized, single blinded control trial comparing haemolysis rate between two cannula aspiration techniques
Authors: Dwyer Donovan G , Fry Margaret , Somerville Annabel , Holdgate Anna
Published: November 2006

Objective:  Blood aspiration through i.v. cannulae is a common ED sampling method. It is, however, associated with increased haemolysis rates when compared with direct venipuncture. Our ED utilizes two common methods of sampling through cannulae. The aim of the present study was to examine the haemolysis rates for these two techniques.

Methods:  A randomized, single blinded prospective study was performed. From a convenience sample patients were randomized to either ‘Method one’ (blood taken directly from cannula hub) or ‘Method two’ (blood taken using an Interlink device through cannula cap). For each group patient demographics, clinical information and haemolysis were analysed. χ2‐analysis and a multivariate logistic regression model were applied to determine significant relationships.

Results:  A total of 1390 patients were enrolled, 694 had blood collected by ‘Method one’ and 696 by ‘Method two’, with haemolysis rates of 6.5% and 7.2%, respectively. Univariate analysis showed ease of aspiration to be the only variable to have a strong association with haemolysis (P < 0.0001). After allowing for ease of aspiration the technique used did not significantly affect haemolysis rate (P = 0.7).

Conclusions:  The rate of haemolysis is unrelated to the technique of blood aspiration. However, haemolysis rates increase significantly with perceived difficulty of blood draw.
A Comparison of the Efficacy and Tolerability of Tadalafil 10 mg and 20 mg in Japanese Patients with Severe Erectile Dysfunction
Authors: Marumo Ken , Imaoka Takeshi , Fujimoto Kenjiro , Watts Steven , Stothard Diane , McGill James
Published: November 2006

Introduction

Tadalafil is a phosphodiesterase type 5 inhibitor with documented efficacy in the treatment of erectile dysfunction (ED).

Aim

To compare the efficacy and tolerability of tadalafil 10 mg and 20 mg in men with severe ED.

Methods

A prespecified subgroup analysis was conducted to compare the efficacy of tadalafil 10 and 20 mg measured by the International Index of Erectile Function (IIEF) erectile function (EF) domain and Sexual Encounter Profile (SEP) among patients with severe ED (EF domain score=1–10) in a Japanese placebo-controlled study (PCT). We also analyzed the efficacy of the two doses in men with severe ED post hoc by pooling data from three tadalafil clinical trials that evaluated these doses using a similar study design (three placebo-controlled trials), and evaluated (post hoc) the presence of organic comorbidities in patients with different levels of response to tadalafil 10 or 20 mg.

Main Outcome Measures

Mean change in the IIEF-EF domain and mean per-patient changes in percent “yes” responses to SEP Question 2 (SEP2) and Question 3 (SEP3).

Results

Patients with severe ED in the Japanese study experienced numerically greater increases (improvements) when taking tadalafil 20 mg compared with 10 mg in the IIEF-EF domain (14.3 vs. 12.4; P =0.355), SEP2 (60% vs. 57%; P =0.781), and SEP3 (61% vs. 49%, P =0.196). When sufficiently powered, these observations reached statistical significance in the three PCTs: patients with severe ED experienced greater increases when taking tadalafil 20 mg compared with 10 mg in the IIEF-EF domain (13.6 vs. 10.4; P =0.014) and SEP3 (56% vs. 43%, P =0.019). Both doses were well tolerated.

Conclusion

Patients with severe ED, and especially those with an organic comorbidity, may derive greater clinical benefits from tadalafil 20 mg compared with 10 mg.
Effective x‐ray attenuation measurements with full field digital mammography
Authors: Heine John J. , Behera Madhusmita
Published: November 2006

This work shows that effective x‐ray attenuation coefficients may be estimated by applying Beer's Law to phantom image data acquired with the General Electric Senographe 2000D full field digital mammography system. Theoretical developments are provided indicating that an approximate form of the Beer's relation holds for polychromatic x‐ray beams. The theoretical values were compared with experimentally determined measured values, which were estimated at various detector locations. The measured effective attenuation coefficients are in agreement with those estimated with theoretical developments and numerical integration. The work shows that the measured quantities show little spatial variation. The main ideas are demonstrated with polymethylmethacrylate and breast tissue equivalent phantom imaging experiments. The work suggests that the effective attenuation coefficients may be used as known values for radiometric standardization applications that compensate for the image acquisition influences. The work indicates that it is possible to make quantitative attenuation coefficient measurements from a system designed for clinical purposes.
Calculated and measured brachytherapy dosimetry parameters in water for the Xoft Axxent X‐Ray Source: An electronic brachytherapy sourcea)
Authors: Rivard Mark J. , Davis Stephen D. , DeWerd Larry A. , Rusch Thomas W. , Axelrod Steve
Published: November 2006

A new x‐ray source, the model S700 Axxent™ X‐Ray Source (Source), has been developed by Xoft Inc. for electronic brachytherapy. Unlike brachytherapy sources containing radionuclides, this Source may be turned on and off at will and may be operated at variable currents and voltages to change the dose rate and penetration properties. The in‐water dosimetry parameters for this electronic brachytherapy source have been determined from measurements and calculations at 40, 45, and settings. Monte Carlo simulations of radiation transport utilized the MCNP5 code and the EPDL97‐based mcplib04 cross‐section library. Inter‐tube consistency was assessed for 20 different Sources, measured with a PTW 34013 ionization chamber. As the Source is intended to be used for a maximum of ten treatment fractions, tube stability was also assessed. Photon spectra were measured using a high‐purity germanium (HPGe) detector, and calculated using MCNP. Parameters used in the two‐dimensional (2D) brachytherapy dosimetry formalism were determined. While the Source was characterized as a point due to the small anode size, , use of the one‐dimensional (1D) brachytherapy dosimetry formalism is not recommended due to polar anisotropy. Consequently, 1D brachytherapy dosimetry parameters were not sought. Calculated point‐source model radial dose functions at were 0.20, 0.24, and 0.29 for the 40, 45, and voltage settings, respectively. For , measured point‐source model radial dose functions were typically within 4% of calculated results. Calculated values for for all operating voltages were within 15% of unity along the distal end , and ranged from to towards the catheter proximal end. For all three operating voltages using the PTW chamber, measured dependence of output as a function of azimuthal angle, , was typically on average for . Excluding an energy response function, measurements of normalized photon energy spectra were made for three operating voltages, and were typically within 2% agreement with the normalized Monte Carlo calculated spectra. In general, the model S700 Source exhibited depth dose behavior similar to low‐energy photon‐emitting low dose rate sources and , yet with capability for variable and much higher dose rates and subsequently adjustable penetration capabilities. This paper presents the calculated and measured in‐water brachytherapy dosimetry parameters for the model S700 Source at the aforementioned three operating voltages.
Simulation studies of field shaping in rotational radiation therapy
Authors: Ivanova T. , Bliznakova K. , Pallikarakis N.
Published: November 2006

This article presents simulation studies of field shaping in rotational radiation therapy by means of two categories of beam modifying devices: protectors and shapers. The protectors used are diminished copies of the organs at risk (OARs) and stay parallel to them during gantry rotation. Thus, each protector always keeps the corresponding OAR in its shadow, significantly reducing the irradiation. The shapers are used in order to obtain a more uniform dose distribution in the planning target volume (PTV) while preserving their initial orientation during gantry rotation. Thus, the use of beam modifying devices allows modulation of the beam intensity, to better fit irradiation requirements, at every gantry position. A software tool for calculations of geometrical position and dimensions of the beam modifying devices, using information about the shape, size, and position of the protected organ or area at risk as input, was developed. This tool was integrated into the in‐house‐developed Monte Carlo radiation therapy simulator (MCRTS), used to simulate the particle transport through the designed system. The verification of the software tool showed good agreement between experimental and simulation data, with discrepancies of less than 3%. Dose distributions in solid‐geometry and voxel‐based neck models were evaluated. Furthermore, the effectiveness of the shapers to modify the dose distribution outside the protected area was studied. Results demonstrated that the use of the shapers effectively improves dose uniformity. Studies using shapers of different materials were also carried out and resulted in similar dose distributions. The results of the simulation studies with a voxel‐based model showed that rotational therapy with beam modifying devices offers adequate protection of the OAR and a uniform dose distribution outside the protected region.
Characterization of scattered radiation in kV CBCT images using Monte Carlo simulations
Authors: Jarry Geneviève , Graham Sean A. , Moseley Douglas J. , Jaffray David J. , Siewerdsen Jeffrey H. , Verhaegen Frank
Published: November 2006

Kilovoltage (kV) cone beam computed tomography (CBCT) images suffer from a substantial scatter contribution. In this study, Monte Carlo (MC) simulations are used to evaluate the scattered radiation present in projection images. These predicted scatter distributions are also used as a scatter correction technique. Images were acquired using a kV CBCT bench top system. The EGSnrc MC code was used to model the flat panel imager, the phantoms, and the x‐ray source. The x‐ray source model was validated using first and second half‐value layers (HVL) and profile measurements. The HVLs and the profile were found to agree within 3% and 6%, respectively. MC simulated and measured projection images for a cylindrical water phantom and for an anthropomorphic head phantom agreed within 8% and 10%. A modified version of the DOSXYZnrc MC code was used to score phase space files with identified scattered and primary particles behind the phantoms. The cone angle, the source‐to‐detector distance, the phantom geometry, and the energy were varied to determine their effect on the scattered radiation distribution. A scatter correction technique was developed in which the MC predicted scatter distribution is subtracted from the projections prior to reconstruction. Preliminary testing of the procedure was done with an anthropomorphic head phantom and a contrast phantom. Contrast and profile measurements were obtained for the scatter corrected and noncorrected images. An improvement of 3% for contrast between solid water and a liver insert and 11% between solid water and a Teflon insert were obtained and a significant reduction in cupping and streaking artifacts was observed.
Characteristic features of a high‐energy x‐ray spectra estimation method based on the Waggener iterative perturbation principle
Authors: Iwasaki Akira , Kubota Mamoru , Hirota Junichi , Fujimori Akira , Suzaki Katsumasa , Aoki Masahiko , Abe Yoshinao
Published: November 2006

We have redeveloped a high‐energy x‐ray spectra estimation method reported by Iwasaki et al. [A. Iwasaki, H. Matsutani, M. Kubota, A. Fujimori, K. Suzaki, and Y. Abe, Radiat. Phys. Chem. 67, 81–91 (2003)]. The method is based on the iterative perturbation principle to minimize differences between measured and calculated transmission curves, originally proposed by Waggener et al. [R. G. Waggener, M. M. Blough, J. A. Terry, D. Chen, N. E. Lee, S. Zhang, and W. D. McDavid, Med. Phys. 26, 1269–1278 (1999)]. The method can estimate spectra applicable for media at least from water to lead using only about ten energy bins. Estimating spectra of x‐ray beams from a linear accelerator, we describe characteristic features of the method with regard to parameters including the prespectrum, number of transmission measurements, number of energy bins, energy bin widths, and artifactual bipeaked spectrum production.
Routine testing of magnetic field homogeneity on clinical MRI systems
Authors: Chen Hua‐Hsuan , Boykin Rex D. , Clarke Geoffrey D. , Gao Jia‐Hong T. , Roby John W.
Published: November 2006

Poor main magnetic field homogeneity leads to artifacts and signal losses in magnetic resonance imaging (MRI). The American College of Radiology's MRI quality control manual mandates annual checks of , suggesting tests using spectral linewidth and phase‐difference maps. A new method, the bandwidth‐difference method, which compares the distortion for small and large BW acquisitions to determine the , is proposed. The method has the advantage that it can be used to measure multiple diameters of spherical volumes (DSV) in a single phantom. A phantom has been developed to exploit this method and results obtained with it are compared to those using three standard methods. Small receiver BW in the presence of poor leads to geometric distortions because gradients are reduced to the level of the inhomogeneities. Data were acquired using seven MRI systems from different manufacturers, ranging in field strength from . Fast gradient echo pulse sequences were scanned twice using small and large BWs. was measured from the shift of landmarks between the two BW acquisitions. Results were compared with data from the full width at half maximum (FWHM) method, the method and one manufacturer's resonant frequency mapping data. The FWHM method was available on two systems and the method was available on one. The method could be performed in all scanners investigated. The measured ranged for DSV of . Direct comparisons of the data obtained using the method showed good agreement with data obtained using the FWHM method. Data obtained using the method compared favorably with the manufacturer's resonant frequency map. The method produces measurements of at various DSV values that can be obtained from a single set of phantom images. The accuracy of homogeneity measurements are comparable to the other methods tested.
A Monte Carlo model for calculating out‐of‐field dose from a Varian beam
Authors: Kry Stephen F. , Titt Uwe , Pönisch Falk , Followill David , Vassiliev Oleg N. , Allen White R. , Mohan Radhe , Salehpour Mohammad
Published: November 2006

Dose to the patient outside of the treatment field is important when evaluating the outcome of radiotherapy treatments. However, determining out‐of‐field doses for any particular treatment plan currently requires either time‐consuming measurements or calculated estimations that may be highly uncertain. A Monte Carlo model may allow these doses to be determined quickly, accurately, and with a great degree of flexibility. MCNPX was used to create a Monte Carlo model of a Varian Clinac 2100 accelerator head operated at . Simulations of the dose out‐of‐field were made and measurements were taken with thermoluminescent dosimeters in an acrylic phantom and with an ion chamber in a water tank to validate the Monte Carlo model. Although local differences between the out‐of‐field doses calculated by the model and those measured did exceed 50% at some points far from the treatment field, the average local difference was only 16%. This included a range of doses as low as 0.01% of the central axis dose, and at distances in excess of from the central axis of the treatment field. The out‐of‐field dose was found to vary with field size and distance from the central axis, but was almost independent of the depth in the phantom except where the dose increased substantially at depths less than . The relationship between dose and kerma was also investigated, and kerma was found to be a good estimate of dose (within 3% on average) except near the surface and in the field penumbra. Our Monte Carlo model was found to well represent typical Varian 2100 accelerators operated at .
Image‐Guided IMRT
Authors: Low Daniel
Published: November 2006

Image‐Guided IMRT Bortfeld Thomas Schmidt‐Ulrich Rupert De Neve Wilfried Wazer David E. Springer (2006) ISBN: 3‐540‐20511‐X ($199 hard copy).
Mesh adaptation technique for Fourier‐domain fluorescence lifetime imaging
Authors: Soloviev Vadim Y.
Published: November 2006

A novel adaptive mesh technique in the Fourier domain is introduced for problems in fluorescence lifetime imaging. A dynamical adaptation of the three‐dimensional scheme based on the finite volume formulation reduces computational time and balances the ill‐posed nature of the inverse problem. Light propagation in the medium is modeled by the telegraph equation, while the lifetime reconstruction algorithm is derived from the Fredholm integral equation of the first kind. Stability and computational efficiency of the method are demonstrated by image reconstruction of two spherical fluorescent objects embedded in a tissue phantom.
Comparison of clinical and physical measures of image quality in chest and pelvis computed radiography at different tube voltages
Authors: Sandborg Michael , Tingberg Anders , Ullman Gustaf , Dance David R. , Alm Carlsson Gudrun
Published: November 2006

The aim of this work was to study the dependence of image quality in digital chest and pelvis radiography on tube voltage, and to explore correlations between clinical and physical measures of image quality. The effect on image quality of tube voltage in these two examinations was assessed using two methods. The first method relies on radiologists’ observations of images of an anthropomorphic phantom, and the second method was based on computer modeling of the imaging system using an anthropomorphic voxel phantom. The tube voltage was varied within a broad range , including those values typically used with screen‐film radiography. The tube charge was altered so that the same effective dose was achieved for each projection. Two x‐ray units were employed using a computed radiography (CR) image detector with standard tube filtration and antiscatter device. Clinical image quality was assessed by a group of radiologists using a visual grading analysis (VGA) technique based on the revised CEC image criteria. Physical image quality was derived from a Monte Carlo computer model in terms of the signal‐to‐noise ratio, SNR, of anatomical structures corresponding to the image criteria. Both the VGAS (visual grading analysis score) and SNR decrease with increasing tube voltage in both chest PA and pelvis AP examinations, indicating superior performance if lower tube voltages are employed. Hence, a positive correlation between clinical and physical measures of image quality was found. The pros and cons of using lower tube voltages with CR digital radiography than typically used in analog screen‐film radiography are discussed, as well as the relevance of using VGAS and quantum‐noise SNR as measures of image quality in pelvis and chest radiography.
Electronic portal imaging based on Cerenkov radiation: A new approach and its feasibility
Authors: Mei X. , Rowlands J. A. , Pang G.
Published: November 2006

Most electronic portal imaging devices (EPIDs) developed so far use a Cu plate/phosphor screen to absorb x rays and convert their energies into light, and the light image is then read out. The main problem with this approach is that the Cu plate/phosphor screen must be thin ( thick) in order to obtain a high spatial resolution, resulting in a low x‐ray absorption or low quantum efficiency for megavoltage x rays (typically 2–4%). In addition, the phosphor screen contains high atomic number (high‐) materials, resulting in an over‐response of the detector to low‐energy x rays in dosimetric verification. In this paper, we propose a new approach that uses Cerenkov radiation to convert x‐ray energy absorbed by the detector into light for portal imaging applications. With our approach, a thick energy conversion layer made of a low‐ dielectric medium, such as a large‐area, thick fiber‐optic taper consisting of a matrix of optical fibers aligned with the incident x rays, is used to replace the thin Cu plate/phosphor screen. The feasibility of this approach has been investigated using a single optical fiber embedded in a solid material. The spatial resolution expressed by the modulation transfer function (MTF) and the sensitivity of the detector at low doses ( one Linac pulse) have been measured. It is predicted that, using this approach, a detective quantum efficiency of an order of magnitude higher at zero frequency can be obtained while maintaining a reasonable MTF, as compared to current EPIDs.
Staphylococcus aureus
and Staphylococcal Enterotoxin A in Breaded Chicken Products: Detection and Behavior during the Cooking Process
Authors: Pepe Olimpia , Blaiotta Giuseppe , Bucci Francesca , Anastasio Marilena , Aponte Maria , Villani Francesco
Published: November 2006

In this study we examined the presence of
Staphylococcus aureus
and staphylococcal enterotoxin A (SEA) in 20 industrial breaded chicken products obtained from different retail butchers and supermarket stores in Italy. The levels of contamination in the products analyzed were quite low, although the pH values and water activities (a
w
) in the samples considered were in ranges favorable for
S. aureus
growth. As demonstrated by phenotypic and molecular characterization, in spite of the high percentage of coagulase-positive
Staphylococcus
strains, only three strains could be referred to the species
S. aureus
. Moreover, all the strains were negative in PCR assays targeting staphylococcal enterotoxin genes (
se
A to
se
E,
se
G to
se
J, and
se
M to
se
O), as well as the toxic shock syndrome toxin 1 gene, and no SEA was detected in the retail breaded chicken samples analyzed by a reversed passive latex agglutination assay or by Western blotting. Hence, we evaluated the thermal resistance of two strains of SEA-producing
S. aureus
in a laboratory-scale preparation of precooked breaded chicken cutlets. The heat treatment employed in the manufacture determined the inactivation of
S. aureus
cells, but the preformed SEA remained active during product storage at 4°C. The presence of the staphylococci and, in particular, of
S. aureus
in the retail breaded chicken products analyzed is a potential health risk for consumers since the pH and a
w
values of these kinds of products are favorable for
S. aureus
growth. The thermal process used during their manufacture can limit staphylococcal contamination but cannot eliminate preformed toxins.
In Vivo Insertional Mutagenesis in
Corynebacterium pseudotuberculosis
: an Efficient Means To Identify DNA Sequences Encoding Exported Proteins
Authors: Dorella Fernanda A. , Estevam Estela M. , Pacheco Luis G. C. , Guimarães Cláudia T. , Lana Ubiraci G. P. , Gomes Eliane A. , Barsante Michele M. , Oliveira Sérgio C. , Meyer Roberto , Miyoshi Anderson , Azevedo Vasco
Published: November 2006

The reporter transposon-based system TnFuZ was used to identify exported proteins of the animal pathogen
Corynebacterium pseudotuberculosis
. Thirty-four out of 1,500 mutants had detectable alkaline phosphatase (PhoZ) activity. This activity was from 21
C. pseudotuberculosis
loci that code for fimbrial and transport subunits and for hypothetical and unknown-function proteins.
Examination of the Watershed-Wide Distribution of
Escherichia coli
along Southern Lake Michigan: an Integrated Approach
Authors: Whitman Richard L. , Nevers Meredith B. , Byappanahalli Muruleedhara N.
Published: November 2006

Recent research has highlighted the occurrence of
Escherichia coli
in natural habitats not directly influenced by sewage inputs. Most studies on
E. coli
in recreational water typically focus on discernible sources (e.g., effluent discharge and runoff) and fall short of integrating riparian, nearshore, onshore, and outfall sources. An integrated “beachshed” approach that links
E. coli
inputs and interactions would be helpful to understand the difference between background loading and sewage pollution; to develop more accurate predictive models; and to understand the differences between potential, net, and apparent culturable
E. coli
. The objective of this study was to examine the interrelatedness of
E. coli
occurrence from various coastal watershed components along southern Lake Michigan. The study shows that once established in forest soil,
E. coli
can persist throughout the year, potentially acting as a continuous non-point source of
E. coli
to nearby streams. Year-round background stream loading of
E. coli
can influence beach water quality.
E. coli
is present in highly variable counts in beach sand to depths just below the water table and to distances at least 5 m inland from the shore, providing a large potential area of input to beach water. In summary,
E. coli
in the fluvial-lacustrine system may be stored in forest soils, sediments surrounding springs, bank seeps, stream margins and pools, foreshore sand, and surface groundwater. While rainfall events may increase
E. coli
counts in the foreshore sand and lake water, concentrations quickly decline to prerain concentrations. Onshore winds cause an increase in
E. coli
in shallow nearshore water, likely resulting from resuspension of
E. coli
-laden beach sand. When examining indicator bacteria source, flux, and context, the entire “beachshed” as a dynamic interacting system should be considered.
Molecular Analysis of
tet
(W) Gene-Mediated Tetracycline Resistance in Dominant Intestinal
Bifidobacterium
Species from Healthy Humans
Authors: Flórez Ana Belén , Ammor Mohammed Salim , Álvarez-Martín Pablo , Margolles Abelardo , Mayo Baltasar
Published: November 2006

tet
(W) was found responsible for tetracycline resistance (MICs, 4 to ≥32 μg ml
−1
) in dominant bifidobacterial species from the gastrointestinal tracts of healthy humans. The gene from
Bifidobacterium longum
H66 proved to be identical over a 2.6-kbp region to the recently described
tet
(W) determinant of
Butyrivibrio fibrisolvens
.