bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of temperature on the expression of cytoplasmic male sterility in cultivated barley (Hordeum vulgare L.)
Authors: Abdel‐Ghani Adel H. , Frey Felix P. , Parzies Heiko K. 
Published: November 2012

AbstractTwenty‐three cytoplasmic male sterile BC1F1 barley lines were exposed to varying temperature treatments (TTs) to examine the effect of temperature on the stability of the expression of cytoplasmic male sterility (cms). The TTs used for this test were: (i) controlled low‐temperature treatment of 16°C (CL), (ii) controlled medium‐temperature treatment of 21–24/16–17°C day/night (CM) and (iii) ambient glasshouse‐temperature treatment of 24–41/16–17°C day/night (AG). The expression of cms was found to be variably influenced by temperature and by the genetic background of the cms recipient lines. Ten cms lines exhibited consistently complete male sterility over TTs, indicating that these lines are completely under cms genes control, while other lines showed partial revision to fertility across different TTs with profound influence of warm temperatures (CM and AG) in breaking down the cms in barley.
Investigations on the Endometrial Response to Intrauterine Administration of N‐Acetylcysteine in Oestrous Mares
Authors: Melkus E , Witte T , Walter I , Heuwieser W , Aurich C 
Published: November 2012

ContentsIn mares, mating‐induced persistent endometritis contributes to low fertility. The condition is in part related to delayed clearance of mucus accumulated within the uterine lumen. The objective of this study was to investigate the endometrial response of healthy mares to intrauterine (i.u.) treatment with N‐acetylcysteine (NAC). Oestrous mares (n = 12) were randomly assigned to a treatment (TM) or control (C) group and received an i.u. infusion of 5%NACand saline (total volume 140 ml), respectively. Endometrial biopsies were collected in five of the mares 24 h after treatment, in the remaining seven mares 72 h after treatment. Endometrial biopsies were evaluated for integrity of the luminal epithelium, number of polymorphonuclear neutrophils (PMN), staining for cyclooxygenase 2 (COX2), staining with Kiel 67 antigen (Ki‐67), lectins and periodic acid‐Schiff (PAS). The integrity of endometrial epithelial cells was not affected by treatment (no statistical differences between groups or times). At 24 h after treatment, the mean number ofPMNin endometrial biopsies fromNAC‐ and C‐mares did not differ, but at 72 h after treatment, number ofPMNwas significantly higher (p < 0.05) in C (3.9 ± 0.6PMN/field) compared withNAC‐treated mares (2.3 ± 0.2PMN/field). At 72 h after treatment, the intensity of staining forCOX2 was significantly higher after saline than afterNACtreatment (p < 0.05). In the epithelium, no differences in staining for the proliferation marker Ki‐67 were seen with respect to time and treatment. Score for the lectin wheat germ agglutinin (WGA) was slightly higher inNAC‐treated mares than in C‐mares 72 h after treatment (p < 0.05). Score forPASstaining of mucus in deep uterine glands differed significantly between groups at 24 h after treatment (p < 0.05). The present study demonstrates thatNACdoes not adversely affect the endometrial function. Moreover, an anti‐inflammatory effect on the equine endometrium was observed.
A linear recurrence sequence of composite numbers
Authors: Šiurys Jonas 
Published: November 2012

AbstractWe prove that for each positive integerkin the range 2≤k≤10 and for each positive integerk≡79 (mod 120) there is ak-step Fibonacci-like sequence of composite numbers and give some examples of such sequences. This is a natural extension of a result of Graham for the Fibonacci-like sequence.
Interventricular comparison of the energetics of contraction of trabeculae carneae isolated from the rat heart
Authors: Han June‐Chiew , Taberner Andrew J. , Nielsen Poul M. F. , Loiselle Denis S. 
Published: November 2012

Key points
With each beat of the heart, the left and right ventricles must overcome substantially different arterial pressures in order to eject blood.
We have tested whether this difference in mechanical demand is reflected in different metabolic energy expenditure.
Our experimental preparations were trabeculae isolated from both ventricles; our index of metabolic energy expenditure was their heat production in response to electrical stimulation.
We found that the cost of activating contraction (i.e. the production of heat in the absence of force generation) was higher in trabeculae from the left ventricle, thereby conferring a lower mechanical efficiency on that ventricle.
Correction for the activation heat reveals the thermodynamic efficiency of the actomyosin crossbridges; whereas there was no interventricular difference in this fundamental property of cardiac muscle, its dependence on force development is baffling.
Abstract  We compare the energetics of right ventricular and left ventricular trabeculae carneae isolated from rat hearts. Using our work‐loop calorimeter, we subjected trabeculae to stress‐length work (W), designed to mimic the pressure–volume work of the heart. Simultaneous measurement of heat production (Q) allowed calculation of the accompanying change of enthalpy (ΔH=W+Q). From the mechanical measurements (i.e. stress and change of length), we calculated work, shortening velocity and power. In combination with heat measurements, we calculated activation heat (QA), crossbridge heat (Qxb) and two measures of cardiac efficiency: ‘mechanical efficiency’ (ɛmech=W/ΔH) and ‘crossbridge efficiency’ (ɛxb=W/(ΔH–QA)). With respect to their left ventricular counterparts, right venticular trabeculae have higher peak shortening velocity, and higher peak mechanical efficiency, but with no difference of stress development, twitch duration, work performance, shortening power or crossbridge efficiency. That is, the 35% greater maximum mechanical efficiency of right venticular than left ventricular trabeculae (13.6 vs. 10.2%) is offset by the greater metabolic cost of activation (QA) in the latter. When corrected for this difference, crossbridge efficiency does not differ between the ventricles.
Event time representation in cerebellar mossy fibres arising from the lateral reticular nucleus
Authors: Xu W. , Jones S. , Edgley S. A. 
Published: November 2012

Key points
The lateral reticular nucleus (LRN) sends dense mossy fibre projections to the cerebellum. We report that LRN neurons convey timing signals that, along with measurements of force and distance, are needed for the cerebellum to organise movement.
We show that LRN neurons fire with clock‐like regularity but pause their firing in response to peripheral sensory stimuli; regular firing then resumes at a new, ‘reset’ time. Thus, the firing properties of LRN neurons enable them to signal the timing of sensory events to the cerebellum over prolonged periods.
We show a plausible ionic mechanism for these properties of LRN neurons, involving the concerted activity of the hyperpolarisation‐activated cation conductance (Ih) and the small‐conductance calcium‐activated potassium conductance (SK). Notably, Ih shortens the latency and sharpens the precision of post‐inhibitory spiking.
Overall, we provide evidence for a potential mechanism of time representation in a neural circuit.
Abstract  Time representation is an important element of cerebellar neural processing, but the mechanisms involved are poorly understood. We demonstrate that the major mossy fibre input system originating from the lateral reticular nucleus (LRN) can represent sensory event timing over hundreds of milliseconds. In vivo, cerebellar‐projecting LRN neurons discharge extremely regularly with a clock‐like rhythm. In response to stimulation of a wide peripheral receptive field, firing briefly pauses then resumes with precise timing. The precision of post‐stimulus spikes and the regularity of firing mean that the stimulus timing is represented by LRN spike timing over hundreds of milliseconds. In an arithmetic progression model of LRN neuron firing, highly predictable post‐stimulus spike timing is modulated by changing the variability of the first post‐inhibitory spike and of the subsequent interspike intervals. From in vitro analysis we show that the Ca2+‐activated small‐conductance K+ current (SK) contributes to interspike interval regularity and that the hyperpolarization‐activated cation current (Ih) contributes to short‐latency, high‐precision post‐hyperpolarisation spike timing. Consistent with this, we demonstrate in vivo that resumption of firing becomes more sharply timed after longer stimulus‐evoked pauses. Thus, Ih is a potential conductance that could mediate the precisely timed resumption of firing after the pause. Through the widespread projections of LRN neurons, these properties may enable the LRN to provide precisely timed signals to the cerebellum over a prolonged period following a stimulus, which may also both activate and sustain oscillatory processes in the cerebellar cortex.
Relation between plaque type, plaque thickness, blood shear stress, and plaque stress in coronary arteries assessed by X‐ray Angiography and Intravascular Ultrasound
Authors: Balocco Simone , Gatta Carlo , Alberti Marina , Carrillo Xavier , Rigla Juan , Radeva Petia 
Published: November 2012

Purpose:Atheromatic plaque progression is affected, among others phenomena, by biomechanical, biochemical, and physiological factors. In this paper, the authors introduce a novel framework able to provide both morphological (vessel radius, plaque thickness, and type) and biomechanical (wall shear stress and Von Mises stress) indices of coronary arteries.Methods:First, the approach reconstructs the three‐dimensional morphology of the vessel from intravascular ultrasound (IVUS) and Angiographic sequences, requiring minimal user interaction. Then, a computational pipeline allows to automatically assess fluid‐dynamic and mechanical indices. Ten coronary arteries are analyzed illustrating the capabilities of the tool and confirming previous technical and clinical observations.Results:The relations between the arterial indices obtained by IVUS measurement and simulations have been quantitatively analyzed along the whole surface of the artery, extending the analysis of the coronary arteries shown in previous state of the art studies. Additionally, for the first time in the literature, the framework allows the computation of the membrane stresses using a simplified mechanical model of the arterial wall.Conclusions:Circumferentially (within a given frame), statistical analysis shows an inverse relation between the wall shear stress and the plaque thickness. At the global level (comparing a frame within the entire vessel), it is observed that heavy plaque accumulations are in general calcified and are located in the areas of the vessel having high wall shear stress. Finally, in their experiments the inverse proportionality between fluid and structural stresses is observed.
Verification of TG‐61 dose for synchrotron‐produced monochromatic x‐ray beams using fluence‐normalized MCNP5 calculations
Authors: Brown Thomas A. D. , Hogstrom Kenneth R. , Alvarez Diane , Matthews Kenneth L. , Ham Kyungmin 
Published: November 2012

Purpose:Ion chamber dosimetry is being used to calibrate dose for cell irradiations designed to investigate photoactivated Auger electron therapy at the Louisiana State University Center for Advanced Microstructures and Devices (CAMD) synchrotron facility. This study performed a dosimetry intercomparison for synchrotron‐produced monochromatic x‐ray beams at 25 and 35 keV. Ion chamber depth‐dose measurements in a polymethylmethacrylate (PMMA) phantom were compared with the product of MCNP5 Monte Carlo calculations of dose per fluence and measured incident fluence.Methods:Monochromatic beams of 25 and 35 keV were generated on the tomography beamline at CAMD. A cylindrical, air‐equivalent ion chamber was used to measure the ionization created in a 10 × 10 × 10‐cm3 PMMA phantom for depths from 0.6 to 7.7 cm. The American Association of Physicists in Medicine TG‐61 protocol was applied to convert measured ionization into dose. Photon fluence was determined using a NaI detector to make scattering measurements of the beam from a thin polyethylene target at angles 30°–60°. Differential Compton and Rayleigh scattering cross sections obtained from xraylib, an ANSI C library for x‐ray‐matter interactions, were applied to derive the incident fluence. MCNP5 simulations of the irradiation geometry provided the dose deposition per photon fluence as a function of depth in the phantom.Results:At 25 keV the fluence‐normalized MCNP5 dose overestimated the ion‐chamber measured dose by an average of 7.2 ± 3.0%–2.1 ± 3.0% for PMMA depths from 0.6 to 7.7 cm, respectively. At 35 keV the fluence‐normalized MCNP5 dose underestimated the ion‐chamber measured dose by an average of 1.0 ± 3.4%–2.5 ± 3.4%, respectively.Conclusions:These results showed that TG‐61 ion chamber dosimetry, used to calibrate dose output for cell irradiations, agreed with fluence‐normalized MCNP5 calculations to within approximately 7% and 3% at 25 and 35 keV, respectively.
Small field segments surrounded by large areas only shielded by a multileaf collimator: Comparison of experiments and dose calculation
Authors: Kron T. , Clivio A. , Vanetti E. , Nicolini G. , Cramb J. , Lonski P. , Cozzi L. , Fogliata A. 
Published: November 2012

Purpose:Complex radiotherapy fields delivered using a tertiary multileaf collimator (MLC) often feature small open segments surrounded by large areas of the beam only shielded by the MLC. The aim of this study was to test the ability of two modern dose calculation algorithms to accurately calculate the dose in these fields which would be common, for example, in volumetric modulated arc treatment (VMAT) and study the impact of variations in dosimetric leaf gap (DLG), focal spot size, and MLC transmission in the beam models.Methods:Nine test fields with small fields (0.6–3 cm side length) surrounded by large MLC shielded areas (secondary collimator 12 × 12 cm2) were created using a 6 MV beam from a Varian Clinac iX linear accelerator with 120 leaf MLC. Measurements of output factors and profiles were performed using a diamond detector (PTW) and compared to two dose calculations algorithms anisotropic analytical algorithm [(AAA) and Acuros XB] implemented on a commercial radiotherapy treatment planning system (Varian Eclipse 10).Results:Both calculation algorithms predicted output factors within 1% for field sizes larger than 1 × 1 cm2. For smaller fields AAA tended to underestimate the dose. Profiles were predicted well for all fields except for problems of Acuros XB to model the secondary penumbra between MLC shielded fields and the secondary collimator. A focal spot size of 1 mm or less, DLG 1.4 mm and MLC transmission of 1.4% provided a generally good model for our experimental setup.Conclusions:AAA and Acuros XB were found to predict the dose under small MLC defined field segments well. While DLG and focal spot affect mostly the penumbra, the choice of correct MLC transmission will be essential to model treatments such as VMAT accurately.
Imaging of cardiac perfusion of free‐breathing small animals using dynamic phase‐correlated micro‐CT
Authors: Sawall Stefan , Kuntz Jan , Socher Michaela , Knaup Michael , Hess Andreas , Bartling Sönke , Kachelrieß Marc 
Published: November 2012

Purpose:Mouse models of cardiac diseases have proven to be a valuable tool in preclinical research. The high cardiac and respiratory rates of free breathing mice prohibit conventionalin vivo cardiac perfusion studies using computed tomography even if gating methods are applied. This makes a sacrification of the animals unavoidable and only allows for the application of ex vivo methods.Methods:To overcome this issue the authors propose a low dose scan protocol and an associated reconstruction algorithm that allows forin vivo imaging of cardiac perfusion and associated processes that are retrospectively synchronized to the respiratory and cardiac motion of the animal. The scan protocol consists of repetitive injections of contrast media within several consecutive scans while the ECG, respiratory motion, and timestamp of contrast injection are recorded and synchronized to the acquired projections. The iterative reconstruction algorithm employs a six‐dimensional edge‐preserving filter to provide low‐noise, motion artifact‐free images of the animal examined using the authors’ low dose scan protocol.Results:The reconstructions obtained show that the complete temporal bolus evolution can be visualized and quantified in any desired combination of cardiac and respiratory phase including reperfusion phases. The proposed reconstruction method thereby keeps the administered radiation dose at a minimum and thus reduces metabolic inference to the animal allowing for longitudinal studies.Conclusions:The authors’ low dose scan protocol and phase‐correlated dynamic reconstruction algorithm allow for an easy and effective way to visualize phase‐correlated perfusion processes in routine laboratory studies using free‐breathing mice.
Dynamically accumulated dose and 4D accumulated dose for moving tumors
Authors: Li Heng , Li Yupeng , Zhang Xiaodong , Li Xiaoqiang , Liu Wei , Gillin Michael T. , Zhu X. Ronald 
Published: November 2012

Purpose:The purpose of this work was to investigate the relationship between dynamically accumulated dose (dynamic dose) and 4D accumulated dose (4D dose) for irradiation of moving tumors, and to quantify the dose uncertainty induced by tumor motion.Methods:The authors established that regardless of treatment modality and delivery properties, the dynamic dose will converge to the 4D dose, instead of the 3D static dose, after multiple deliveries. The bounds of dynamic dose, or the maximum estimation error using 4D or static dose, were established for the 4D and static doses, respectively. Numerical simulations were performed (1) to prove the principle that for each phase, after multiple deliveries, the average number of deliveries for any given time converges to the total number of fractions (K) over the number of phases (N); (2) to investigate the dose difference between the 4D and dynamic doses as a function of the number of deliveries for deliveries of a “pulsed beam”; and (3) to investigate the dose difference between 4D dose and dynamic doses as a function of delivery time for deliveries of a “continuous beam.” A Poisson model was developed to estimate the mean dose error as a function of number of deliveries or delivered time for both pulsed beam and continuous beam.Results:The numerical simulations confirmed that the number of deliveries for each phase converges toK/N, assuming a random starting phase. Simulations for the pulsed beam and continuous beam also suggested that the dose error is a strong function of the number of deliveries and/or total deliver time and could be a function of the breathing cycle, depending on the mode of delivery. The Poisson model agrees well with the simulation.Conclusions:Dynamically accumulated dose will converge to the 4D accumulated dose after multiple deliveries, regardless of treatment modality. Bounds of the dynamic dose could be determined using quantities derived from 4D doses, and the mean dose difference between the dynamic dose and 4D dose as a function of number of deliveries and/or total deliver time was also established.
A GPU tool for efficient, accurate, and realistic simulation of cone beam CT projections
Authors: Jia Xun , Yan Hao , Cerviño Laura , Folkerts Michael , Jiang Steve B. 
Published: November 2012

Purpose:Simulation of x‐ray projection images plays an important role in cone beam CT (CBCT) related research projects, such as the design of reconstruction algorithms or scanners. A projection image contains primary signal, scatter signal, and noise. It is computationally demanding to perform accurate and realistic computations for all of these components. In this work, the authors develop a package on graphics processing unit (GPU), called gDRR, for the accurate and efficient computations of x‐ray projection images in CBCT under clinically realistic conditions.Methods:The primary signal is computed by a trilinear ray‐tracing algorithm. A Monte Carlo (MC) simulation is then performed, yielding the primary signal and the scatter signal, both with noise. A denoising process specifically designed for Poisson noise removal is applied to obtain a smooth scatter signal. The noise component is then obtained by combining the difference between the MC primary and the ray‐tracing primary signals, and the difference between the MC simulated scatter and the denoised scatter signals. Finally, a calibration step converts the calculated noise signal into a realistic one by scaling its amplitude according to a specified mAs level. The computations of gDRR include a number of realistic features, e.g., a bowtie filter, a polyenergetic spectrum, and detector response. The implementation is fine‐tuned for a GPU platform to yield high computational efficiency.Results:For a typical CBCT projection with a polyenergetic spectrum, the calculation time for the primary signal using the ray‐tracing algorithms is 1.2–2.3 s, while the MC simulations take 28.1–95.3 s, depending on the voxel size. Computation time for all other steps is negligible. The ray‐tracing primary signal matches well with the primary part of the MC simulation result. The MC simulated scatter signal using gDRR is in agreement with EGSnrc results with a relative difference of 3.8%. A noise calibration process is conducted to calibrate gDRR against a real CBCT scanner. The calculated projections are accurate and realistic, such that beam‐hardening artifacts and scatter artifacts can be reproduced using the simulated projections. The noise amplitudes in the CBCT images reconstructed from the simulated projections also agree with those in the measured images at corresponding mAs levels.Conclusions:A GPU computational tool, gDRR, has been developed for the accurate and efficient simulations of x‐ray projections of CBCT with realistic configurations.