bluuebunny/crossref_metadata_2025 huggingface dataset:
Climate Change Impacts on Water Resources in the Upper Blue Nile River Basin, Ethiopia1
Authors: Kim Ungtae , Kaluarachchi Jagath J.
Published: September 2009

Kim, Ungtae and Jagath J. Kaluarachchi, 2009. Climate Change Impacts on Water Resources in the Upper Blue Nile River Basin, Ethiopia. Journal of the American Water Resources Association (JAWRA) 45(6):1361‐1378.

Abstract:  Climate change affects water resources availability of international river basins that are vulnerable to runoff variability of upstream countries especially with increasing water demands. The upper Blue Nile River Basin is a good example because its downstream countries, Sudan and Egypt, depend solely on Nile waters for their economic development. In this study, the impacts of climate change on both hydrology and water resources operations were analyzed using the outcomes of six different general circulation models (GCMs) for the 2050s. The outcomes of these six GCMs were weighted to provide average future changes. Hydrologic sensitivity, flow statistics, a drought index, and water resources assessment indices (reliability, resiliency, and vulnerability) were used as quantitative indicators. The changes in outflows from the two proposed dams (Karadobi and Border) to downstream countries were also assessed. Given the uncertainty of different GCMs, the simulation results of the weighted scenario suggested mild increases in hydrologic variables (precipitation, temperature, potential evapotranspiration, and runoff) across the study area. The weighted scenario also showed that low‐flow statistics and the reliability of streamflows are increased and severe drought events are decreased mainly due to increased precipitation. Joint dam operation performed better than single dam operation in terms of both hydropower generation and mean annual storage without affecting the runoff volume to downstream countries, but enhancing flow characteristics and the robustness of streamflows. This study provides useful information to decision makers for the planning and management of future water resources of the study area and downstream countries.
Metastatic cutaneous malignant melanoma: Spectrum of imaging findings and the role of multimodality imaging
Authors: Kochhar R , Ali H , Mak S , Manoharan P
Published: September 2009

Cutaneous malignant melanoma is one of the most lethal and widely metastasising cancers with unpredictable pathways of spread. One of the most significant factors associated with survival in patients who have distant metastases is the number of organ sites involved. Innovative treatment options are now available for metastatic melanoma, and diagnostic imaging has become crucial for accurate staging and restaging of disease. The objective of this pictorial review is to illustrate the imaging spectrum of metastatic cutaneous malignant melanoma including both the common and the relatively ubiquitous sites of involvement using both conventional cross‐sectional and metabolic molecular imaging. This review also highlights the importance of combining multiple imaging methods for accurate staging of metastatic melanoma.
Economics and Asia‐Pacific Region Territorial and Maritime Disputes: Understanding the Political Limits to Economic Solutions
Authors: Blanchard Jean‐Marc F.
Published: September 2009

Territorial and maritime disputes are a visible part of the tapestry of Asia‐Pacific Region (APR) international relations. They have provoked frictions between states, militarized conflict, and even war. Some believe interstate economic ties or economic inducements have the potential to mitigate and resolve the APR's territorial and maritime controversies. In this article, I analyze, in two primary ways, the potential for economics to calm or resolve the APR's territorial and maritime disputes. One is a theoretical evaluation, while the other is an empirical examination. As for the latter, this article analyzes two specific quarrels: the China‐Japan controversy over the East China Sea and Diaoyu/Senkaku Islands and the Japanese‐Soviet/Russian conflict over the Northern Territories. In both cases, the economic optimist case is proved wanting. This article shows that researchers must pay attention to political factors, domestic and international, to identify the factors that facilitate/hinder a settlement of territorial and maritime disputes.
Inhibition of the active lymph pump by flow in rat mesenteric lymphatics and thoracic duct
Authors: Gashev Anatoliy A. , Davis Michael J. , Zawieja David C.
Published: September 2009

There are only a few reports of the influence of imposed flow on an active lymph pump under conditions of controlled intraluminal pressure. Thus, the mechanisms are not clearly defined. Rat mesenteric lymphatics and thoracic ducts were isolated, cannulated and pressurized. Input and output pressures were adjusted to impose various flows. Lymphatic systolic and diastolic diameters were measured and used to determine contraction frequency and pump flow indices. Imposed flow inhibited the active lymph pump in both mesenteric lymphatics and in the thoracic duct. The active pump of the thoracic duct appeared more sensitive to flow than did the active pump of the mesenteric lymphatics. Imposed flow reduced the frequency and amplitude of the contractions and accordingly the active pump flow. Flow‐induced inhibition of the active lymph pump followed two temporal patterns. The first pattern was a rapidly developing inhibition of contraction frequency. Upon imposition of flow, the contraction frequency immediately fell and then partially recovered over time during continued flow. This effect was dependent on the magnitude of imposed flow, but did not depend on the direction of flow. The effect also depended upon the rate of change in the direction of flow. The second pattern was a slowly developing reduction of the amplitude of the lymphatic contractions, which increased over time during continued flow. The inhibition of contraction amplitude was dependent on the direction of the imposed flow, but independent of the magnitude of flow. Nitric oxide was partly but not completely responsible for the influence of flow on the mesenteric lymph pump. Exposure to NO mimicked the effects of flow, and inhibition of the NO synthase by NG‐monomethyl‐l‐arginine attenuated but did not completely abolish the effects of flow.
Rapidly and slowly activating components of delayed rectifier K+current in guinea‐pig sino‐atrial node pacemaker cells
Authors: Matsuura Hiroshi , Ehara Tsuguhisa , Ding Wei‐Guang , Omatsu‐Kanbe Mariko , Isono Takahiro
Published: September 2009

The components and properties of the delayed rectifier K+current (IK) in isolated guinea‐pig sino‐atrial (SA) node pacemaker cells were investigated using the whole‐cell configuration of the patch‐clamp technique. An envelope of tails test was conducted by applying depolarizing pulses from a holding potential of −50 mV to +30 mV for various durations ranging from 40 to 2000 ms. The ratio of the tail current amplitude elicited upon return to the holding potential to the magnitude of the time‐dependent outward current activated during depolarizing steps was dependent on the pulse duration, while after exposure to the selectiveIKrinhibitor E‐4031 (5 μm) this current ratio became practically constant irrespective of the pulse duration. These observations are consistent with the presence of the E‐4031‐sensitive, rapidly activating and E‐4031‐resistant, slowly activating components ofIK(IKrandIKs, respectively) in guinea‐pig SA node cells. The activation range forIKr, defined as the E‐4031‐sensitive current (half‐maximal activation voltage (V1/2) of −26.2 mV) was much more negative than that forIKs, defined as the E‐4031‐resistant current (V1/2of +17.2 mV).IKrexhibited a marked inward rectification at potentials positive to −50 mV, whereasIKsshowed only a slight rectification. In the current‐clamp experiments, bath application of E‐4031 (0.5 and 5 μm) initially slowed the repolarization at potentials negative to approximately −30 mV and produced a significant depolarization of the maximum diastolic potential, followed by the arrest of electrical activity, thus indicating that the late phase of the repolarization leading to the maximum diastolic potential at around −60 mV in spontaneous action potentials is primarily produced byIKrin guinea‐pig SA node cells. External application of the selectiveIKsinhibitor 293B (30 μm) also delayed the repolarization process at potentials negative to about −20 mV and induced moderate depolarization of the maximum diastolic potential leading to the arrest of the spontaneous activity. These results provide evidence to suggest that bothIKrandIKsare present and play crucial roles in the spontaneous electrical activity of guinea‐pig SA node pacemaker cells.
Adenosine inhibition via A1receptor of N‐type Ca2+current and peptide release from isolated neurohypophysial terminals of the rat
Authors: Wang Gang , Dayanithi Govindan , Custer Edward E. , Lemos José R.
Published: September 2009

Effects of adenosine on voltage‐gated Ca2+channel currents and on arginine vasopressin (AVP) and oxytocin (OT) release from isolated neurohypophysial (NH) terminals of the rat were investigated using perforated‐patch clamp recordings and hormone‐specific radioimmunoassays. Adenosine, but not adenosine 5′‐triphosphate (ATP), dose‐dependently and reversibly inhibited the transient component of the whole‐terminal Ba2+currents, with an IC50of 0.875 μm.Adenosine strongly inhibited, in a dose‐dependent manner (IC50= 2.67 μm), depolarization‐triggered AVP and OT release from isolated NH terminals. Adenosine and the N‐type Ca2+channel blocker ω‐conotoxin GVIA, but not other Ca2+channel‐type antagonists, inhibited the same transient component of the Ba2+current. Other components such as the L‐, Q‐ and R‐type channels, however, were insensitive to adenosine. Similarly, only adenosine and ω‐conotoxin GVIA were able to inhibit the same component of AVP release. A1receptor agonists, but not other purinoceptor‐type agonists, inhibited the same transient component of the Ba2+current as adenosine. Furthermore, the A1receptor antagonist 8‐cyclopentyltheophylline (CPT), but not the A2receptor antagonist 3, 7‐dimethyl‐1‐propargylxanthine (DMPGX), reversed inhibition of this current component by adenosine. The inhibition of AVP and OT release also appeared to be via the A1receptor, since it was reversed by CPT. We therefore conclude that adenosine, acting via A1receptors, specifically blocks the terminal N‐type Ca2+channel thus leading to inhibition of the release of both AVP and OT.
On Asymptotic Analysis for Large Amplitude Nonlinear Free Vibration of Simply Supported Laminated Plates
Authors: Lai S. K. , Lim C. W. , Xiang Y. , Zhang W.
Published: September 2009

An analytical approximation is developed for solving large amplitude nonlinear free vibration of simply supported laminated cross-ply composite thin plates. Applying Kirchhoff’s hypothesis and the nonlinear von Kármán plate theory, a one-dimensional nonlinear second-order ordinary differential equation with quadratic and cubic nonlinearities is formulated with the aid of an energy function. By imposing Newton’s method and harmonic balancing to the linearized governing equation, we establish the higher-order analytical approximations for solving the nonlinear differential equation with odd nonlinearity. Based on the nonlinear differential equation with odd and even nonlinearities, two new nonlinear differential equations with odd nonlinearity are introduced for constructing the analytical approximations to the nonlinear differential equation with general nonlinearity. The analytical approximations are mathematically formulated by combining piecewise approximate solutions from such two new nonlinear systems. The third-order analytical approximation with better accuracy is proposed here and compared with other numerical and approximate methods with respect to the exact solutions. In addition, the method presented herein is applicable to small as well as large amplitude vibrations of laminated plates. Several examples including large amplitude nonlinear free vibration of simply supported laminated cross-ply rectangular thin plates are illustrated and compared with other published results to demonstrate the applicability and effectiveness of the approach.
Fabrication, Testing, and Modeling of Carbon Nanotube Composites for Vibration Damping
Authors: Dai R. L. , Liao W. H.
Published: September 2009

In this research, carbon nanotube (CNT) composite with epoxy resin is fabricated. The dynamic properties of the nanotube composites are evaluated. A testing apparatus for obtaining dynamic properties of composites is set up, and measurement procedures are given. In particular, the loss factors together with stiffness are measured for the specimens with different CNT weight ratios. Experimental results show that CNT additive can provide the composite with several times higher damping as compared with pure epoxy. A composite unit cell model containing a single CNT segment is developed by using the finite element method. Composite loss factors are calculated based on the average ratio of the unit cell energy loss to the unit cell energy input. Calculated loss factors under different strain are compared with experimental data. With the validated model, a parametric study is subsequently performed. Parameters, such as CNT dimension and CNT alignment orientation, are studied. The factors that lead to higher composite damping capacity are identified.
The Dynamic Analysis of an Energy Storage Flywheel System With Hybrid Bearing Support
Authors: Wang Hongchang , Jiang Shuyun , Shen Zupei
Published: September 2009

Active magnetic bearings and superconducting magnetic bearings were used on a high-speed flywheel energy storage system; however, their wide industrial acceptance is still a challenging task because of the complexity in designing the elaborate active control system and the difficulty in satisfying the cryogenic condition. A hybrid bearing consisting of a permanent magnetic bearing and a pivot jewel bearing is used as the support for the rotor of the energy storage flywheel system. It is simple and has a long working life without requiring maintenance or an active control system. The two squeeze film dampers are employed in the flywheel system to suppress the lateral vibration, to enhance the rotor leaning stability, and to reduce the transmitted forces. The dynamic equation of the flywheel with four degrees of complex freedom is built by means of the Lagrange equation. In order to improve accuracy, the finite element method is utilized to solve the Reynolds equation for the dynamic characteristics of the squeeze film damper. When the calculated unbalance responses are compared with the test responses, they indicate that the dynamics model is correct. Finally, the effect of the squeeze film gap on the transmitted force is analyzed, and the appropriate gap should be selected to cut the energy loss and to control vibration of the flywheel system.
On the Displacement Transmissibility of a Base Excited Viscously Damped Nonlinear Vibration Isolator
Authors: Milovanovic Zarko , Kovacic Ivana , Brennan Michael J.
Published: September 2009

In this article vibration isolators having linear and cubic nonlinearities in stiffness and damping terms are considered under base excitation. The influence of the system parameters on the relative and absolute displacement transmissibility is investigated. The performance characteristics of the nonlinear isolators are evaluated and compared with the performance characteristics of the linear isolators to highlight the beneficial effects in the nonlinear systems considered.
Design Strategies for the Topology Synthesis of Dual Input-Single Output Compliant Mechanisms
Authors: Kim Charles
Published: September 2009

In this paper, design strategies are presented for the topology synthesis of dual input-single output compliant mechanisms. Decomposition methods are proposed to yield tractable subproblems to achieve motion requirements. The methods make use of the single point synthesis, which effectively generates topologies satisfying the motion requirements at one point by assembling compliant building blocks. In this paper, the compliant deviation angle is proposed to measure the ability of building blocks to transmit load with minimal storage of strain energy. The design strategies are versatile in allowing the designer to incorporate auxiliary design considerations and to synthesize mechanism that traverse a locus of output displacements. The building block approach pursued in this paper provides crucial insight to augment designer understanding and ability.
Structural Synthesis
of Serial-Parallel Hybrid Mechanisms Based on Representation and Operation of Logical
Matrix
Authors: Zeng Qiang , Fang Yuefa
Published: September 2009

This paper presents a systematic approach on structural synthesis of serial-parallel hybrid mechanisms from the point of displacement group theory and mathematical logic. The hybrid mechanisms can be represented by binary 12 bit string matrix, where the lower 4 bits represents the universal set of spatial displacement subsets, while the higher 8 bits represents the two-order adjacent relations of spatial displacement subsets. Meanwhile, the concept of an arrangement matrix and three types of fractal operations can be developed. Utilizing the novel representational approach of mechanisms, the displacement subsets and spatial adjacent relations can be operated in logical matrices based on the given mapping of logical matrix operation. The binary logical mirror coordinate system of mechanisms is developed by logical representations. Finally, an example of structural synthesis of hybrid mechanism (two-order hybrid mechanism) is introduced using the proposed approach. The approach is helpful for the processing of serial-parallel hybrid mechanism designs.
Workspace Analysis for Planar and Spatial Redundant Cable Robots
Authors: Ghasemi Ali , Eghtesad Mohammad , Farid Mehrdad
Published: September 2009

This paper presents workspace analysis of planar and spatial cable robots having one or more redundant cables. The proposed approach, which is based on a variant of Bland’s pivot rule, provides all poses (positions/orientations) reachable by the cable robot platform with any number of cable redundancies. By virtue of this method, there is no need to use successive determinants to compute the workspace; this results in less computation time. Additionally, another algorithm, which takes advantage of reduced row-echelon form of the system matrix, is proposed for the case of cable robots with only one redundant cable and also to include upper limit for tensions in cables as an important factor in workspace analysis of the cable robots. Simulation results are provided to show the merits of the proposed methods to compute the available static workspace of the redundant cable robots.
Mechanical Issues Inherent in Antagonistically Actuated Systems
Authors: Russell Donald L. , McTavish Megan , English Chad E.
Published: September 2009

The relationship between the stiffness properties of actuators configured in an agonist-antagonist configuration and the stiffness of the joint is simple but not intuitively obvious. In this paper, this relationship is investigated and it is shown that the stiffness properties (hardening or softening) of the joint depend on the second derivative of the individual actuator stiffness with respect to actuator displacement. Numerical examples are given to illustrate the relationship and two practical examples, in which the actuators stiffness arises from Belleville washers or from an air piston, are analyzed.
Nondestructive measurement of the grid ratio using a single image
Authors: Pasciak A. S. , Jones A. Kyle
Published: September 2009

The antiscatter grid is an essential part of modern radiographic systems. Since the introduction of the antiscatter grid, however, there have been few methods proposed for acceptance testing and verification of manufacturer‐supplied grid specifications. The grid ratio is an important parameter describing the antiscatter grid because it affects many other grid quality metrics, such as the contrast improvement ratio , primary transmission , and scatter transmission . Also, the grid ratio in large part determines the primary clinical use of the grid. To this end, the authors present a technique for the nondestructive measurement of the grid ratio of antiscatter grids. They derived an equation that can be used to calculate the grid ratio from a single off‐focus flat field image by exploiting the relationship between grid cutoff and off‐focus distance. The calculation can be performed by hand or with included analysis software. They calculated the grid ratios of several different grids throughout the institution, and afterward they destructively measured the grid ratio of a nominal grid previously evaluated with the method. They also studied the sensitivity of the method to technical factors and choice of parameters. With one exception, the results for the grids found in the institution were in agreement with the manufacturer's specifications and international standards. The nondestructive evaluation of the grid indicated a ratio of 7.3, while the destructive measurement indicated a ratio of . Repeated evaluations of the same grid yielded consistent results. The technique provides the medical physicist with a new tool for quantitative evaluation of the grid ratio, an important grid performance criterion. The method is robust and repeatable when appropriate choices of technical factors and other parameters are made.
Adaptive two‐pass cone‐beam artifact correction using a FOV‐preserving two‐source geometry: A simulation study
Authors: Forthmann P. , Grass M. , Proksa R.
Published: September 2009

The evolution to ever wider detector arrays that are able to cover whole organs with a single circular gantry sweep has revitalized the research efforts toward finding improved axial scanning algorithms and protocols. The authors propose a computed tomography scan and reconstruction concept using two sources, a single detector and a two‐pass cone‐beam correction method, as an integral part of the reconstruction. Compared with standard circular acquisition and reconstruction methods, the new concept excels with improved coverage and very low cone‐beam artifact level also for short scan acquisitions, which makes it especially attractive for cardiac applications.
A solid iodinated phantom material for use in tomographic x‐ray imaging
Authors: Hill Melissa L. , Mainprize James G. , Mawdsley Gordon E. , Yaffe Martin J.
Published: September 2009

PURPOSE:

Iodinated phantoms are of value in x‐ray imaging for quality control measurements, system calibration, and for use in the research setting; however, the liquid phantoms that are most often used have several limitations including variability between repeated dilutions, inhomogeneities from air bubbles or precipitants, and long set up times. Although suitable materials have been investigated for projection radiography, quantitative measurements of contrast enhancement in computed tomography (CT) have become increasingly important in the clinic, and a need exists for a durable and reproducible iodinated phantom material. In this work, the authors describe a solid radiographic phantom material that has an accurately known concentration of iodine distributed uniformly throughout its volume and that has stable properties over time. This material can be molded or machined into a desired shape to create a test object or for use in an anthropomorphic phantom.

METHODS:

Two sets of calibration phantoms were produced with a clinically relevant range of iodine concentrations. Measurements were made on these phantoms to characterize the material properties in terms of accuracy of iodine concentration, radiographic uniformity, temporal stability of x‐ray attenuation, and manufacturing repeatability. Experimentally measured linear x‐ray attenuation coefficients were compared to those predicted by a theoretical model. The uniformity of the iodine distribution in the material was assessed by measuring image intensity variation, both in projection images and in reconstructed CT volumes. The reproducibility of manufacture was estimated on a set of independently produced samples. A longitudinal study was performed to assess the stability of the material x‐ray characteristics over time by making measurements at 6 month intervals.

RESULTS:

Good agreement was seen between the experimental measurements of effective attenuation and the theoretically predicted values. It is estimated that a desired iodine concentration could be produced to within 0.04 mg/ml. Comparison of the measured effective linear iodine attenuation coefficients of eight 1.0 mg/ml samples indicated a manufacturing reproducibility of ±0.03 mg/ml iodine. Variations in uniformity across each of the samples were on the order of image intensity fluctuations. No inhomogeneities due to mixing or settling were apparent. An analysis of longitudinal data collected for both calibration sets revealed no perceptible change in radiographic properties over the first 6 months after manufacture, nor over a subsequent 1.5 yr period from 1 yr postmanufacture onward.

CONCLUSIONS:

The uniformity, stability, and precision of this iodinated material suggest that it is suitable for use in accurate calibration tools for contrast tomographic imaging.
Design and characterization of a spatially distributed multibeam field emission x‐ray source for stationary digital breast tomosynthesis
Authors: Qian Xin , Rajaram Ramya , Calderon‐Colon Xiomara , Yang Guang , Phan Tuyen , Lalush David S. , Lu Jianping , Zhou Otto
Published: September 2009

Digital breast tomosynthesis (DBT) is a limited angle computed tomography technique that can distinguish tumors from its overlying breast tissues and has potentials for detection of cancers at a smaller size and earlier stage. Current prototype DBT scanners are based on the regular full‐field digital mammography systems and require partial isocentric motion of an x‐ray tube over certain angular range to record the projection views. This prolongs the scanning time and, in turn, degrades the imaging quality due to motion blur. To mitigate the above limitations, the concept of a stationary DBT (s‐DBT) scanner has been recently proposed based on the newly developed spatially distributed multibeam field emission x‐ray (MBFEX) source technique using the carbon nanotube. The purpose of this article is to evaluate the performance of the 25‐beam MBFEX source array that has been designed and fabricated for the s‐DBT system. The s‐DBT system records all the projection images by electronically activating the multiple x‐ray beams from different viewing angles without any mechanical motion. The configuration of the MBFEX source is close to the published values from the Siemens Mammomat system. The key issues including the x‐ray flux, focal spot size, spatial resolution, scanning time, beam‐to‐beam consistency, and reliability are evaluated using the standard procedures. In this article, the authors describe the design and performance of a distributed x‐ray source array specifically designed for the s‐DBT system. They evaluate the emission current, current variation, lifetime, and focal spot sizes of the source array. An emission current of up to 18 mA was obtained at effective focal spot size. The experimentally measured focal spot sizes are comparable to that of a typical commercial mammography tube without motion blurring. Trade‐off between the system spatial resolution, x‐ray flux, and scanning time are also discussed. Projection images of a breast phantom were collected using the x‐ray source array from 25 different viewing angles without motion. These preliminary results demonstrate the feasibility of the proposed s‐DBT scanner. The technology has the potential to increase the resolution and reduce the imaging time for DBT. With the present design of 25 views, they demonstrated experimentally the feasibility of achieving 11 s scanning time at full detector resolution with source resolution without motion blur. The flexibility in configuration of the x‐ray source array will also allow system designers to consider imaging geometries that are difficult to achieve with the conventional single‐source rotating approach.
RBE estimation of proton radiation fields using a telescope
Authors: Wroe Andrew , Schulte Reinhard , Fazzi Alberto , Pola Andrea , Agosteo Stefano , Rosenfeld Anatoly
Published: September 2009

A new monolithic silicon telescope was evaluated in unmodulated and modulated 100 MeV proton beams used for hadron therapy. Compared to a classical microdosimetry detector, which provides one‐dimensional information on lineal energy of charged particles, this detector system provides two‐dimensional information on lineal energy and particle energy based on energy depositions, collected in coincidence, within the and stages of the detector. The authors investigated the possibility to use the information obtained with the telescope to determine the relative biological effectiveness (RBE) at defined locations within the proton Bragg peak and spread‐out Bragg peak (SOBP). An RBE matrix based on the established in vitro V79 cell survival data was developed to link the output of the device directly to , the RBE in the low‐dose limit, at various depths in a homogeneous polystyrene phantom. In the SOBP of a 100 MeV proton beam, the increased from 4.04 proximal to the SOBP to a maximum value of 5.4 at the distal edge. The telescope, with its high spatial resolution, has potential applications to biologically weighted hadron treatment planning as it provides a compact and portable means for estimating the RBE in rapidly changing hadron radiation fields within phantoms.
A more accurate reconstruction system matrix for quantitative proton computed tomography
Authors: Penfold S. N. , Rosenfeld A. B. , Schulte R. W. , Schubert K. E.
Published: September 2009

An accurate system matrix is required for quantitative proton CT (pCT) image reconstruction with iterative projection algorithms. The system matrix is composed of chord lengths of individual proton path intersections with reconstruction pixels. In previous work, reconstructions were performed assuming constant intersection chord lengths, which led to systematic errors of the reconstructed proton stopping powers. The purpose of the present work was to introduce a computationally efficient variable intersection chord length in order to improve the accuracy of the system matrix. An analytical expression that takes into account the discrete stepping nature of the pCT most likely path (MLP) reconstruction procedure was created to describe an angle‐dependent effective mean chord length function. A pCT dataset was simulated with GEANT4 using a parallel beam of 200 MeV protons intersecting a computerized head phantom consisting of tissue‐equivalent materials with known relative stopping power. The phantom stopping powers were reconstructed with the constant chord length, exact chord length, and effective mean chord length approaches, in combination with the algebraic reconstruction technique. Relative stopping power errors were calculated for each anatomical phantom region and compared for the various methods. It was found that the error of approximately 10% in the mean reconstructed stopping power value for a given anatomical region, resulting from a system matrix with a constant chord length, could be reduced to less than 0.5% with either the effective mean chord length or exact chord length approaches. Reconstructions with the effective mean chord length were found to be approximately 20% faster than reconstructions with an exact chord length. The effective mean chord length method provides the possibility for more accurate, computationally efficient quantitative pCT reconstructions.
First application of dynamic infrared imaging in boron neutron capture therapy for cutaneous malignant melanoma
Authors: Santa Cruz G. A. , González S. J. , Bertotti J. , Marín J.
Published: September 2009

Purpose:

The purpose of this study is to assess the potential of dynamic infrared imaging (DIRI) as a functional, noninvasive technique for evaluating the skin acute toxicity and tumor control within the framework of the Argentine boron neutron capture therapy (BNCT) program for cutaneous malignant melanoma.

Methods:

Two patients enrolled in the Argentine phase I/II BNCT clinical trial for cutaneous malignant melanoma were studied with DIRI. An uncooled infrared camera, providing a video output signal, was employed to register the temperature evolution of the normal skin and tumor regions in patients subjected to a mild local cooling (cold stimulus). In order to study the spatial correlation between dose and acute skin reactions, three‐dimensional representations of the superficial dose delivered to skin were constructed and cameralike projections of the dose distribution were coregistered with visible and infrared images.

Results:

The main erythematous reaction was observed clinically between the second and fifth week post‐BNCT. Concurrently, with its clinical onset, a reactive increase above the basal skin temperature was observed with DIRI in the third week post‐BNCT within regions that received therapeutic doses. Melanoma nodules appeared as highly localized hyperthermic regions. 2 min after stimulus, these regions reached a temperature plateau and increased in size. Temperature differences with respect to normal skin up to were observed in the larger nodules.

Conclusions:

Preliminary results suggest that DIRI, enhanced by the application of cold stimuli, may provide useful functional information associated with the metabolism and vasculature of tumors and inflammatory processes related to radiation‐induced changes in the skin as well. These capabilities are aimed at complementing the clinical observations and standard imaging techniques, such as CT and Doppler ultrasound.
Development of a high precision dosimetry system for the measurement of surface dose rate distribution for eye applicators
Authors: Eichmann Marion , Flühs Dirk , Spaan Bernhard
Published: September 2009

Purpose:

The therapeutic outcome of the therapy with ophthalmic applicators is highly dependent on the application of a sufficient dose to the tumor, whereas the dose applied to the surrounding tissue needs to be minimized. The goal for the newly developed apparatus described in this work is the determination of the individual applicator surface dose rate distribution with a high spatial resolution and a high precision in dose rate with respect to time and budget constraints especially important for clinical procedures. Inhomogeneities of the dose rate distribution can be detected and taken into consideration for the treatment planning.

Methods:

In order to achieve this, a dose rate profile as well as a surface profile of the applicator are measured and correlated with each other. An instrumental setup has been developed consisting of a plastic scintillator detector system and a newly designed apparatus for guiding the detector across the applicator surface at a constant small distance. It performs an angular movement of detector and applicator with high precision.

Results:

The measurements of surface dose rate distributions discussed in this work demonstrate the successful operation of the measuring setup. Measuring the surface dose rate distribution with a small distance between applicator and detector and with a high density of measuring points results in a complete and gapless coverage of the applicator surface, being capable of distinguishing small sized spots with high activities. The dosimetrical accuracy of the measurements and its analysis is sufficient (uncertainty in the dose rate in terms of absorbed dose to water is), especially when taking the surgical techniques in positioning of the applicator on the eyeball into account.

Conclusions:

The method developed so far allows a fully automated quality assurance of eye applicators even under clinical conditions. These measurements provide the basis for future calculation of a full 3D dose rate distribution, which then can be used as input for a refined clinical treatment planning system. The improved dose rate measurements will facilitate a clinical study, which could correlate the therapeutic outcome of a brachytherapy treatment with an applicator and its individual dose rate distribution.
Demons deformable registration for CBCT‐guided procedures in the head and neck: Convergence and accuracy
Authors: Nithiananthan S. , Brock K. K. , Daly M. J. , Chan H. , Irish J. C. , Siewerdsen J. H.
Published: September 2009

Purpose:

The accuracy and convergence behavior of a variant of the Demons deformable registration algorithm were investigated for use in cone‐beam CT (CBCT)‐guided procedures of the head and neck. Online use of deformable registration for guidance of therapeutic procedures such as image‐guided surgery or radiation therapy places trade‐offs on accuracy and computational expense. This work describes a convergence criterion for Demons registration developed to balance these demands; the accuracy of a multiscale Demons implementation using this convergence criterion is quantified in CBCT images of the head and neck.

Methods:

Using an open‐source “symmetric” Demons registration algorithm, a convergence criterion based on the change in the deformation field between iterations was developed to advance among multiple levels of a multiscale image pyramid in a manner that optimized accuracy and computation time. The convergence criterion was optimized in cadaver studies involving CBCT images acquired using a surgical C‐arm prototype modified for 3D intraoperative imaging. CBCT‐to‐CBCT registration was performed and accuracy was quantified in terms of the normalized cross‐correlation (NCC) and target registration error (TRE). The accuracy and robustness of the algorithm were then tested in clinical CBCT images of ten patients undergoing radiation therapy of the head and neck.

Results:

The cadaver model allowed optimization of the convergence factor and initial measurements of registration accuracy: Demons registration exhibited and in the cadaveric head compared to and with rigid registration. Similarly for the patient data, Demons registration gave mean compared to rigid registration , suggesting registration accuracy at or near the voxel size of the patient images . The multiscale implementation based on optimal convergence criteria completed registration in for the cadaveric head and in an average time of for the larger FOV patient images.

Conclusions:

Appropriate selection of convergence and multiscale parameters in Demons registration was shown to reduce computational expense without sacrificing registration performance. For intraoperative CBCT imaging with deformable registration, the ability to perform accurate registration within the stringent time requirements of the operating environment could offer a useful clinical tool allowing integration of preoperative information while accurately reflecting changes in the patient anatomy. Similarly for CBCT‐guided radiation therapy, fast accurate deformable registration could further augment high‐precision treatment strategies.
Coxiella burnetiiIsolates Cause Genogroup-Specific Virulence in Mouse and Guinea Pig Models of Acute Q Fever
Authors: Russell-Lodrigue K. E. , Andoh M. , Poels M. W. J. , Shive H. R. , Weeks B. R. , Zhang G. Q. , Tersteeg C. , Masegi T. , Hotta A. , Yamaguchi T. , Fukushi H. , Hirai K. , McMurray D. N. , Samuel J. E.
Published: September 2009

Q fever is a zoonotic disease of worldwide significance caused by the obligate intracellular bacteriumCoxiella burnetii. Humans with Q fever may experience an acute flu-like illness and pneumonia and/or chronic hepatitis or endocarditis. Various markers demonstrate significant phylogenetic separation between and clustering among isolates from acute and chronic human disease. The clinical and pathological responses to infection with phase IC. burnetiiisolates from the following four genomic groups were evaluated in immunocompetent and immunocompromised mice and in guinea pig infection models: group I (Nine Mile, African, and Ohio), group IV (Priscilla and P), group V (G and S), and group VI (Dugway). Isolates from all of the groups produced disease in the SCID mouse model, and genogroup-consistent trends were noted in cytokine production in response to infection in the immunocompetent-mouse model. Guinea pigs developed severe acute disease when aerosol challenged with group I isolates, mild to moderate acute disease in response to group V isolates, and no acute disease when infected with group IV and VI isolates.C. burnetiiisolates have a range of disease potentials; isolates within the same genomic group cause similar pathological responses, and there is a clear distinction in strain virulence between these genomic groups.
The enigmatic diapsid Acerosodontosaurus piveteaui (Reptilia: Neodiapsida) from the Upper Permian of Madagascar and the paraphyly of “younginiform” reptiles
Authors: Bickelmann Constanze , Müller Johannes , Reisz Robert R.
Published: September 2009

A restudy of the Upper Permian diapsid Acerosodontosaurus piveteaui from Madagascar indicates that the bone formerly identified as the quadratojugal is a fragment of a rib. This in turn implies that, in contrast to previous studies, the lower temporal arcade must be considered incomplete and derived relative to the ancestral condition. Since the phylogenetic position of Acerosodontosaurus is poorly understood, the taxon was entered into a modified phylogenetic data matrix of diapsid reptiles, and the purported monophyly of “Younginiformes” was tested for the first time by including all potential members of the clade as separate taxa, as well as other taxa from the same deposits. The results of the phylogenetic analysis do not support the monophyly of “younginiform” reptiles. Instead, most taxa cluster unresolved at the base of Neodiapsida, a finding that has important implications for the understanding of early diapsid evolution because it suggests that early neodiapsids represent several distinct evolutionary lineages. Acerosodontosaurus and Hovasaurus do form a clade, a finding consistent with the stratigraphic age and biogeography of these taxa.
Paleomagnetism and U–Pb geochronology of Franklin dykes in High Arctic Canada and Greenland: a revised age and paleomagnetic pole constraining block rotations in the Nares Strait regionThis is a companion paper to Denyszyn, S.W., Davis, D.W., and Halls, H.C. Paleomagnetism and U–Pb geochronology of the Clarence Head dykes, Arctic Canada: orthogonal emplacement of mafic dykes in a large igneous province. Canadian Journal of Earth Sciences, 46(3): 155–167.
Authors: Denyszyn Steven W. , Halls Henry C. , Davis Don W. , Evans David A.D.
Published: September 2009

U–Pb baddeleyite ages and paleomagnetic poles obtained for dykes on Devon Island and Ellesmere Island in the Canadian Arctic and the Thule region of Greenland show that they are associated with the Franklin magmatic event. This study is the only one devoted to Franklin igneous rocks where a primary paleomagnetic remanence and U–Pb age have been obtained from the same rocks. Ages from this study range from 721 to 712 Ma, but paleomagnetic directional data show no clear age progression. The paleomagnetic poles from each of the two regional subsets are significantly different at the 95% confidence level from paleomagnetic results previously published for the Franklin event in the Canadian Shield. The difference in the pole locations can be accounted for, to first approximation, by a simple model of early Cenozoic block rotations among the North American plate, Greenland, and a hypothesized ancient microplate comprising Ellesmere, Devon, Cornwallis, and perhaps Somerset islands. A new grand-mean paleopole for the Franklin event, including restoration of Greenland and the proposed “Ellesmere microplate” to North America, is located at (8.4°N, 163.8°E, A95 = 2.8°, N = 78 sites) and is a key pole for Neoproterozoic supercontinent reconstructions.
Effects of the parental environment on full-sib families of Pinussylvestris
Authors: Dormling Ingegerd , Johnsen Øystein
Published: September 2009

Identical pair crosses, including reciprocals, in Pinussylvestris L. (Scots pine) were made on ramets of the same clones in three clonal archives (seed orchards) in Sweden: Sävar (64°N), Röskär (59.5°N), and Degeberga (56°N). The offspring were used to test the hypothesis that the parental environment could affect the performance of the progeny (aftereffects). Growth and freezing tests were performed in the controlled conditions of the Stockholm Phytotron. Parental environment affected seed weight: the heaviest seeds came from Röskär and the lightest seeds, from Degeberga. Height development was affected in the two growth periods tested: seeds from Sävar produced the shortest plants and seeds from Röskär, the tallest plants. There was an effect on the autumn frost hardiness in the first growth period that disappeared after the second growth period. The most hardy progenies came from Sävar. The aftereffects of the parental environment were less than the maternal effects on seed weight and also less than the effects of full-sib families on growth and autumn frost hardiness. Small but mostly significant reciprocal effects were found for height and height increment during the second growth period. There was a significant reciprocal effect for seed weight. Seed weight differences could explain only a small part of the effects on growth and none of the effects on hardiness.
Variation in water potential components among half-sib families of shortleaf pine (Pinusechinata) in response to soil drought
Authors: Choi H.S.
Published: September 2009

To assess family differences in response to drought, various water potential components of seedlings from six half-sib families of shortleaf pine (Pinusechinata Mill.) were compared under control (well-watered) and drought conditions. Drought stress resulted in significant changes in water relations parameters of the seedlings between treatments and among families. Although both Montgomery (103) and Pope (322) families had a superior capacity to adjust osmotically to both treatments, Montgomery (103) family exhibited greater potential to adapt to droughty environments through having the lowest values of osmotic potential both at maximum turgor and at the turgor loss point and having the highest values of (i) mean volume of osmostic water at the turgor loss point per volume of symplasmic water, (ii) symplasmic water volume per total shoot water volume, (iii) maximum bulk elastic modules, and (iv) turgor potential. Families Polk (115) and Scott (202) showed intermediate responses to drought. Both Scott (219) and Yell (342) families showed the lowest ability for osmotic adjustment to both treatments, but Yell (342) family revealed even lower drought resistance responses. Results from this study may provide the means of screening families that have high drought resistance potential during the field establishment period.