bluuebunny/crossref_metadata_2025 huggingface dataset:
Sci—Fri PM: Delivery — 12: Scatter‐B‐Gon: Implementing a fast Monte Carlo cone‐beam computed tomography scatter correction on real data
Authors: Watson P , Mainegra‐Hing E , Soisson E , Naqa I El , Seuntjens J
Published: July 2012

A fast and accurate MC‐based scatter correction algorithm was implemented on real cone‐beam computed tomography (CBCT) data. An ACR CT accreditation phantom was imaged on a Varian OBI CBCT scanner using the standard‐dose head protocol (100 kVp, 151 mAs, partial‐angle). A fast Monte Carlo simulation developed in the EGSnrc framework was used to transport photons through the uncorrected CBCT scan. From the simulation output, the contribution from both primary and scattered photons for each projection image was estimated. Using these estimates, a subtractive scatter correction was performed on the CBCT projection data. Implementation of the scatter correction algorithm on real CBCT data was shown to help mitigate scatter‐induced artifacts, such as cupping and streaking. The scatter corrected images were also shown to have improved accuracy in reconstructed attenuation coefficient values. In three regions of interest centered on material inserts in the ACR phantom, the reconstructed CT numbers agreed with clinical CT scan data to within 35 Hounsfield units after scatter correction. These results suggest that the proposed scatter correction algorithm is successful in improving image quality in real CBCT images. The accuracy of the attenuation coefficients extracted from the corrected CBCT scan renders the data suitable for adaptive on the fly dose calculations on individual fractions, as well as vastly improved image registration.
Sci—Sat AM: Brachy — 01: Evaluation of dose‐volume metrics for microbeam radiation therapy
Authors: Anderson D , Siegbahn EA , Fallone BG , Serduc R , Warkentin B
Published: July 2012

Microbeam radiation therapy (MRT) is an experimental technique delivering an array of high dose synchrotron X‐ray microbeams. Development of metrics to predict the biological efficacy of MRT dose distributions is needed to guide further MRT research and for potential translation to human trials. The most commonly used metric is the peak‐to‐valley‐dose ratio (PVDR) relating the dose at the microbeam center to that between two microbeams. We investigate three additional metrics that characterize dose distributions from a more volumetric perspective — the peak‐to‐mean‐valley‐dose ratio (PMVDR), mean dose, and percentage volume below a threshold. The metrics are evaluated for Monte Carlo simulations of dose distributions in three cubic head phantoms (2, 4 and 8 cm side lengths) for microbeam widths of 25, 50, and 75 μm and centre‐to‐centre spacings of 100, 200 and 400 μm. The ratio of the PMVDR to the PVDR varied from 0.24 to 0.80 for the different configurations, indicating a difference in the predicted geometric dependence of outcome for these two metrics. The mean dose was 102, 79, and 42 % of the mean skin dose for the 2, 8, and 16 cm head phantoms, respectively. The percentage volume below a 10% dose threshold was highly dependent on geometry, with ranges for the different collimation configurations of 2 – 87% and 33 – 96% for the 2 and 16 cm heads, respectively. Different dose‐volume metrics exhibit different dependencies on MRT geometry parameters, suggesting that reliance on PVDR as a predictor of therapeutic outcome may be insufficient.
Sci—Sat AM: Brachy — 02: Extracting Wair from the 1976 electron beam measurements of domen and lamperti
Authors: Cojocaru CD , Ross CK
Published: July 2012

The average energy expended by an energetic electron to create an ion pair in air, Wair is an important quantity in radiation dosimetry. The data obtained by Domen and Lamperti using electron beams in the energy range from 15 to 50 MeV can be used to extract a value for Wair if the electron stopping powers of graphite and air are assumed to be known. We use Monte Carlo techniques to reanalyze these data and obtain a new estimate for the value of Wair Using the EGSnrc Monte Carlo and its associated user codes, as well as the best availabl‐e stopping power data for graphite, we calculate the perturbation effects due to the calorimeter and ionization chamber and the effect of extrapolating from scattered to plane‐parallel beams. Without further adjustments, the extracted values of Wair show a significant trend as the mean electron energy decreases. We show that part of this trend can be attributed to an incorrect value of the density assigned to the graphite absorbers and part to the likelihood that the nominal energy assigned to the low‐energy electron beams is not correct. Using all the data, we obtain a value for Wair of 33.84 eV per ion pair with a relative standard uncertainty of 0.4 %. This result serves to complement values obtained using 60Co γ‐rays, for which the value of the mean excitation of graphite contributes significantly to the uncertainty.
Sci—Sat AM: Brachy — 06: Monte carlo DNA damage simulations of kV cbct radiation
Authors: Kirkby C , Ghasroddashti E , Poirier Y , Tambasco M , Stewart RD
Published: July 2012

When performed daily, cone beam CT (CBCT) images can accumulate radiation dose to non‐negligible levels. Because kV x‐rays have a larger relative biological effectiveness (RBE) than its MV x‐rays, the accumulated absorbed dose needs to be multiplied by an appropriate RBE to better evaluate the impact of CBCT dose in a treatment planning context. We investigated this question using PENLEOPE simulations to look in detail at the electron energy spectra produced by kV x‐rays and Co‐60 γ‐rays in biologically motivated geometries. The electron spectra were input into the published Monte Carlo Damage Simulation (MCDS) and used to estimate the average number of double strand breaks (DSBs) per Gy per cell. Our results suggest an approximately 10% increase in the RBE for DSB induction. For the majority of treatment planning scenarios where imaging dose is only a small fraction of the total delivered dose to target volumes and organs at risk, the increase in RBE is not critical to be factored in, however for it may play a significant role in predicting the induction of secondary cancers.
Sci—Sat AM: Brachy — 07: Plastic scintillation detector validation for kV dosimetry
Authors: Lessard F , Archambault L , Plamondon M , Després P , Therriault‐Proulx F , Beddar S , Beaulieu L
Published: July 2012

Purpose: To characterize the plastic scintillation detectors (PSDs) response in the diagnostic energy range. A fast and adaptable method for real‐time dosimetry in superficial x‐ray therapy and interventional radiology is proposed. Method: A PSD (1 mm diameter and 10 mm long) is coupled to a 5 m long optical fiber. Scintillation photons are guided to a polychromatic photodiode which provides an electrical current proportional to the input light signal. If the incident energy spectrum is known, the dose measured in the PSD's polystyrene sensitive volume can be converted to score dose in any other media such as air, water or soft tissues using the large cavity theory (LCT). A software simulating x‐ray tube spectra and filtration has been benchmarked and is used for analysis. The method is confirmed by Monte Carlo simulations. Results: PSDs cannot be assumed energy independent with low‐energy photons as a factor 2 has been observed in the energy response between 80 kVp and 150 kVp. When the dose is converted to the desired medium, the PSD's energy dependence is compensated and a 2.1% standard deviation was observed upon the studied energy ranges, which is inside the measurement and calculation uncertainties. Percent depth dose (PDD) measurements are in good agreement with Monte Carlo simulations and results can be improved if the proposed method is applied to compensate beam hardening. Conclusion: PSDs present great potential for real‐time dose measurements with radiologic photon energy.
Sci—Sat AM: Brachy — 08: MRI‐guided planning and maximum achievable HR‐CTV doses in cervix brachytherapy
Authors: Menon G , Sloboda R , Ghosh S , Dundas G , Pearcey R , Huang F
Published: July 2012

Purpose: To present an institutional experience with MRI‐based intracavitary brachytherapy planning for cervix cancer treatments using the EMBRACE protocol and to evaluate maximum HR‐CTV doses that can be achieved when OAR (bladder, rectum, and sigmoid) doses are allowed to equal GECESTRO recommended thresholds. Method: Dose metrics from treatment plans for 20 patients created using MR images (for contouring HR‐CTV and OARs) fused with CT images (for applicator reconstruction) are presented. Starting with a standard Manchester loading, plans were manually optimized (MO) by adjusting dwell positions and times to obtain the desired HR‐CTV D90 target coverage of 35 Gy while limiting OAR doses to below recommended tolerances. In addition, retrospective planning was done using: (i) volume optimization (VO) to compare differences with MO in obtaining the desired target coverage; and (ii) MO and VO techniques to get the highest possible HR‐CTV coverage by allowing OAR doses to equal tolerance values. The latter plans are referred to as MAX plans. Results and Conclusions: 3D MRI‐guided treatment planning for cervix brachytherapy was shown to improve dose‐volume coverage of the target and OARs. MO could conform HR‐CTV D90 to the prescribed dose similar to the VO technique. Sigmoid was often the dose limiting structure. With respect to the prescribed HR‐CTV D90 dose of 35 Gy, MAX plans could increase the prescribed dose by about 22% and 30% for MO and VO plans, respectively, without exceeding OAR thresholds. Consequently, dose escalation for MRI‐guided cervix brachytherapy appears feasible should clinical circumstances warrant.
Sci—Sat AM: Brachy — 10: Adaptation of the CVT algorithm for catheter optimization in high dose rate brachytherapy
Authors: Poulin E , Fekete CA Collins , Morrier J , Varfalvy N , Pouliot J , Beaulieu L
Published: July 2012

Introduction: In interstitial high dose rate (HDR) brachytherapy, the number and positions of the catheter are usually fixed by the use of a template, without considering tumor size and shape. In this work, we present a simple and fast method to optimize both the number and position of catheters, using a modified version of the Centroidal Voronoi Tessellations (CVT) algorithm. Methods: 8 prostate HDR clinical cases were chosen randomly to test our method. The treatment plan was obtained from a research version of IPSA. Clinically relevant dosimetric parameters were computed to evaluate our method and help optimizing the CVT algorithm parameters. Plans were generated with a specified number of catheters ranging from 9 to 18 and compared to the clinical cases with 17 catheters. Results: The computation time to optimize the positions of a specific number of catheters was 1.5 s. The prostate V100 was better than the clinical case up to 12 catheters. Plans with 9 or less catheters would not be clinically acceptable in terms of prostate V100 and D90. High conformity is achieved whether the number of catheters used. The V75 of the bladder seems slightly higher, but not significant clinically. All other dosimetric indices are as good as the clinical plan. Conclusion: We have devised a simple, fast and efficient method to optimize the number and position of catheters in HDR brachytherapy. Ultimately, this catheter optimization algorithm could be coupled with a 3D ultrasound system to allow real‐time guidance and planning for any interstitial brachytherapy sites.
Sci—Sat AM: Brachy — 12: Resolving the olefinic lipid resonance from water in proton magnetic resonance spectra of vertebral bone marrow at 3 T
Authors: Yahya A , Troitskaia A , Fallone BG
Published: July 2012

Proton magnetic resonance spectroscopy (MRS) of vertebral lipids has been shown to be relevant in the study of cancer. The olefinic resonance (≈ 5.4 ppm) yields a measure of lipid unsaturation. However, its measurement with standard short echo time (TE) MRS sequences is difficult due to the large overlapping water signal. The purpose of this work is to optimize the TE of a PRESS (Point RESolved Spectroscopy) sequence to measure the olefinic resonance from spinal bone marrow with minimal losses due to J‐coupling and minimal contamination from water at 3 T, a field strength becoming more common in the clinic. Experiments were conducted on nine oils and on L4 vertebral bone marrow in vivo at 3 T. The methyléne (or methyl + méthyléne), and olefinic resonances were measured with PRESS using multiple TEs. The effects of J‐coupling evolution of the olefinic protons appeared to be minimal when TE = 200 ms. The TE = 200 ms olefinic/methylene peak area ratios calculated for each oil correlated well with ratios deduced from oil compositions in the literature (R2 = 0.92). The TE = 200 ms PRESS spectra obtained from vertebra of four volunteers showed negligible contribution from water to the olefinic resonance, thereby enabling the olefinic peak area to be quantified more accurately. The results of this work demonstrate that a PRESS sequence with TE = 200 ms is suitable for measuring relative levels of lipid unsaturation and for resolving the olefinic resonance from contaminating water signal in spinal bone marrow.
Upregulation of CaMKIIδ during ischaemia–reperfusion is associated with reperfusion-induced arrhythmias and mechanical dysfunction of the rat heart: involvement of sarcolemmal Ca2+-cycling proteins
Authors: Adameova Adriana , Carnicka Slavka , Rajtik Tomas , Szobi Adrian , Nemcekova Martina , Svec Pavel , Ravingerova Tana
Published: July 2012

Although Ca2+/calmodulin-dependent protein kinase II delta (CaMKIIδ) has been implicated in development of different phenotypes of myocardial ischaemia–reperfusion injury, its involvement in arrhythmogenesis and cardiac stunning is not sufficiently elucidated. Moreover, the mechanisms by which CaMKIIδ mediates disturbances in excitation–contraction coupling, are not exactly known. To investigate this, KN-93 (0.5 µmol/L), a CaMKII inhibitor, was administered before induction of global ischaemia and reperfusion in isolated Langendorff-perfused rat hearts. Expression of CaMKIIδ and the sarcollemal Ca2+-cycling proteins, known to be activated during reperfusion, was analyzed using immunoblotting. KN-93 reduced reperfusion-induced ectopic activity and the incidence of ventricular fibrillation. Likewise, the severity of arrhythmias was lower in KN-treated hearts. During the pre-ischaemia phase, neither inotropic nor chronotropic effects were elicited by KN-93, whereas post-ischaemic contractile recovery was significantly improved. Ischaemia–reperfusion increased the expression of CaMKIIδ and sodium–calcium exchanger (NCX1) proteins without any influence on the protein content of alpha 1c, a pore-forming subunit of L-type calcium channels (LTCCs). On the other hand, inhibition of CaMKII normalized changes in the expression of CaMKIIδ and NCX1. Taken together, CaMKIIδ seems to regulate its own turnover and to be an important component of cascade integrating NCX1, rather than LTCCs that promote ischaemia–reperfusion-induced contractile dysfunction and arrhythmias.
Thyroid hormone and cardiac repair/regeneration: from Prometheus myth to reality?
Authors: Pantos Constantinos , Mourouzis Iordanis , Cokkinos Dennis V.
Published: July 2012

Nature’s models of repair and (or) regeneration provide substantial evidence that a natural healing process may exist in the heart. The potential for repair and (or) regeneration has been evolutionarily conserved in mammals, and seems to be restricted to the early developmental stages. This window of regeneration is reactivated during the disease state in which fetal gene reprogramming occurs in response to stress. Analogies exist between the damaged and developing heart, indicating that a regulatory network that drives embryonic heart development may control aspects of heart repair and (or) regeneration. In this context, thyroid hormone (TH), which is a critical regulator of the maturation of the myocardium, appears to have a reparative role later in adult life. Changes in TH – thyroid hormone receptor (TR) homeostasis govern the return of the injured myocardium to the fetal phenotype. Accordingly, TH can induce cardiac repair and (or) regeneration by reactivating developmental gene programming. As a proof of concept in humans, TH is found to be an independent determinant of functional recovery and mortality after myocardial infarction. The potential of TH to regenerate and (or) repair the ischemic myocardium is now awaited to be tested in clinical trials.
Implication of multiple signaling pathways in the regulation of angiotensin II induced enhanced expression of Giα proteins in vascular smooth muscle cells
Authors: Li Yuan , Anand-Srivastava Madhu B.
Published: July 2012

We have previously shown that A10 vascular smooth muscle cells (VSMC) exposed to angiotensin II (Ang II) exhibited overexpression of Giα proteins. In the present study, we examined the involvement of different signaling pathways in regulating Ang II induced enhanced expression of Giα proteins in VSMC by using pharmacological inhibitors. Ang II induced increased expression of Giα proteins in A10 VSMC was markedly attenuated by actinomycin D, losartan (an AT1receptor antagonist), dibutyryl cAMP, phospholipase C (PLC) inhibitor U73122, protein kinase C (PKC) inhibitors staurosporine and GP109203X, but not by PD123319 (an AT2receptor antagonist). In addition, BAPTA-AM and TMB-8 (chelators of intracellular Ca2+); and nifedipine (a blocker of L-type Ca2+channels) significantly inhibited Ang II induced enhanced expression of Giα proteins. On the other hand, extracellular Ca2+chelation using EGTA did not affect the Ang II evoked enhanced levels of Giα proteins. Furthermore, pretreatment of A10 VSMC with calmidazolium (an inhibitor of calmodulin), or KN93 (an inhibitor of CaM kinase), or genistein (an inhibitor of protein tyrosine kinase, PTK), also attenuated the increased levels of Giα proteins induced by Ang II. These results suggest that Ang II induced enhanced expression of Giα proteins may be regulated by different signaling pathways through AT1receptors in A10 VSMC.
PPAR-alpha activation as a preconditioning-like intervention in rats in vivo confers myocardial protection against acute ischaemia–reperfusion injury: involvement of PI3K–Akt
Authors: Ravingerová Táňa , Čarnická Slávka , Nemčeková Martina , Ledvényiová Veronika , Adameová Adriana , Kelly Tara , Barlaka Eleftheria , Galatou Eleftheria , Khandelwal Vinoth Kumar Megraj , Lazou Antigone
Published: July 2012

Peroxisome proliferator-activated receptors (PPAR) regulate the expression of genes involved in lipid metabolism, energy production, and inflammation. Their role in ischaemia–reperfusion (I/R) is less clear, although research indicates involvement of PPARs in some forms of preconditioning. This study aimed to explore the effects of PPAR-α activation on the I/R injury and potential cardioprotective downstream mechanisms involved. Langendorff-perfused hearts of rats pretreated with the selective PPAR-α agonist WY-14643 (WY, pirinixic acid; 3 mg·(kg body mass)·day–1; 5 days) were subjected to 30 min ischaemia – 2 h reperfusion with or without the phosphatidylinositol 3-kinase (PI3K)–Akt inhibitor wortmannin for the evaluation of functional (left ventricular developed pressure, LVDP) recovery, infarct size (IS), and reperfusion-induced arrhythmias. A 2-fold increase in baseline PPAR-α mRNA levels (qPCR) in the WY-treated group and higher post-I/R PPAR-α levels compared with those in untreated controls were accompanied by similar changes in the expression of PPAR-α target genes PDK4 and mCPT-1, regulating glucose and fatty acid metabolism, and by enhanced Akt phosphorylation. Post-ischaemic LVDP restoration in WY-treated hearts reached 60% ± 9% of the pre-ischaemic values compared with 24% ± 3% in the control hearts (P < 0.05), coupled with reduced IS and incidence of ventricular fibrillation that was blunted by wortmannin. Results indicate that PPAR-α up-regulation may confer preconditioning-like protection via metabolic effects. Downstream mechanisms of PPAR-α-mediated cardioprotection may involve PI3K–Akt activation.
Regulation of sarco(endo)plasmic reticulum Ca2+-ATPase and calsequestrin gene expression in the heart
Authors: Zarain-Herzberg Angel , Estrada-Avilés Rafael , Fragoso-Medina Jorge
Published: July 2012

The precise control of Ca2+levels during the contraction–relaxation cycle in cardiac myocytes is extremely important for normal beat-to-beat contractile activity. The sarcoplasmic reticulum (SR) plays a key role controlling calcium concentration in the cytosol. The SR Ca2+-ATPase (SERCA2) transports Ca2+inside the SR lumen during relaxation of the cardiac myocyte. Calsequestrin (Casq2) is the main protein in the SR lumen, functioning as a Ca2+buffer and participating in Ca2+release by interacting with the ryanodine receptor 2 (RyR2) Ca2+-release channel. Alterations in normal Ca2+handling significantly contribute to the contractile dysfunction observed in cardiac hypertrophy and in heart failure. Transcriptional regulation of the SERCA2 gene has been extensively studied and some of the mechanisms regulating its expression have been elucidated. Overexpression of Sp1 factor in cardiac hypertrophy downregulates SERCA2 gene expression and increased levels of thyroid hormone up-regulates its transcription. Other hormones such norepinephrine, angiotensin II, endothelin-1, parathyroid hormone, prostaglandin-F2α, as well the cytokines tumor necrosis factor-α and interleukin-6 also downregulate SERCA2 expression. Calcium acting through the calcineurin–NFAT (nuclear factor of activated T cells) pathway has been suggested to regulate SERCA2 and CASQ2 gene expression. This review focuses on the current knowledge regarding transcriptional regulation of SERCA2 and CASQ2 genes in the normal and pathologic heart.
The effects of phentolamine on fructose-fed rats
Authors: Zhou Kangbin , Kumar Ujendra , Yuen Violet G. , McNeill John H.
Published: July 2012

Metabolic syndrome (MS) is a combination of medical disorders that increase the risk of developing cardiovascular disease and diabetes. MS is associated with obesity, increased blood pressure, hyperlipidemia, and hyperglycemia. This study was designed to investigate the pharmacological profile of phentolamine, a nonselective α adrenergic receptor antagonist, in the prevention of increased blood pressure in fructose-fed rats. Phentolamine prevented the fructose-induced increase in systolic blood pressure without affecting insulin sensitivity and major metabolic parameters. The levels of plasma noradrenaline and angiotensin II, 2 proposed contributors to the development of fructose-induced elevated blood pressure, were examined. Neither noradrenaline nor angiotensin II levels were affected by phentolamine treatment. Since overproduction of nitric oxide has been shown to lead to an elevation in peroxynitrite, the role of oxidative stress, a proposed mechanism of fructose-induced elevated blood pressure and insulin resistance, was examined by measuring plasma levels of total nitrate/nitrite. Plasma nitrate/nitrite was significantly elevated in all fructose-fed animals, regardless of treatment with phentolamine. Another proposed contributor toward fructose-induced MS is an elevation in uric acid levels. In this experiment, plasma levels of uric acid were found to be increased by dietary fructose and were unaffected by phentolamine treatment.
Nutritional aspects of epigenetic inheritance
Authors: Alam Shaan E. , Singh R.B. , Gupta Siddharth , Dherange Parinita , De Meester Fabien , Wilczynska Agnieszka , Dharwadkar Suniti , Wilson Douglas , Hungin Pali
Published: July 2012

The impact of diet and environmental factors on genes concerned with epigenetic inheritance and the mechanism of evolution has grown significantly beyond the Modern Synthesis period. Epigenetic inheritance is the passing of phenotypic change to subsequent generations in ways that are outside the genetic code of DNA. Recently, polymorphisms of the human Delta-5 (fatty acid desaturase, FADS1) and Delta-6 (FADS2) desaturase genes have been described as being associated with the level of several long-chain n-3 and n-6 polyunsaturated fatty acids (PUFAs) in serum phospholipids. Increased consumption of refined starches and sugar increases the generation of superoxide anion in the tissues and free fatty acids (FFA) in the blood. There is an increased amount and activity of nuclear factor-κB (NF-κB), a transcriptional factor regulating the activity of at least 125 genes, most of which are pro-inflammatory. The consumption of glucose may be associated with an increase in 2 other pro-inflammatory transcription factors: activating protein-1 (AP-1), and early growth response protein-1 (Egr-1). AP-1 regulates the transcription of matrix metallo-proteinases and Egr-1 modulates the transcription of tissue factor and plasminogen activator inhibitor-1. It is possible that a complex set of factors, including nutritional factors, come into play during epigenetic inheritance.
UNCONVENTIONAL QUANTUM CRITICAL POINTS
Authors: XU CENKE
Published: July 2012

In this paper we review the theory of unconventional quantum critical points that are beyond the Landau's paradigm. Three types of unconventional QCPs will be discussed: (1) The transition between topological order and semiclassical spin ordered phase; (2) The transition between topological order and valence bond solid phase; (3) The direct second order transition between different competing orders. We focus on the field theory and universality class of these unconventional QCPs. Relation of these QCPs with recent numerical simulations and experiments on quantum frustrated magnets are also discussed.
EXACT SOLITON SOLUTIONS AND QUASI-PERIODIC WAVE SOLUTIONS TO THE FORCED VARIABLE-COEFFICIENT KdV EQUATION
Authors: ZHANG YI , CHENG ZHILONG
Published: July 2012

In this paper, the time-dependent variable-coefficient KdV equation with a forcing term is considered. Based on the Hirota bilinear method, the bilinear form of this equation is obtained, and the multi-soliton solutions are studied. Then the periodic wave solutions are obtained by using Riemann theta function, and it is also shown that classical soliton solutions can be reduced from the periodic wave solutions.
NONLINEAR DYNAMICS OF LONG-RANGE PROTEIN-HELICOIDAL DNA INTERACTIONS
Authors: SAHA MIRABEAU , KOFANÉ TIMOLÉON C.
Published: July 2012

The effects of long-range interactions between peptides on the protein–DNA dynamics in the long-wave limit are studied. The investigation, done at the physiological temperature, is based on a coupled spin system of DNA molecule which includes the helicoidal geometry of DNA molecule and the Kac–Baker long-range interaction between the peptides of the protein molecule. By using the Holstein–Primakoff bosonic representation of the spin operators, we show that the original discrete equations for the protein–DNA interaction dynamics can be reduced to the nonlinear Schrödinger (NLS) equation of which the dispersive and the nonlinear coefficients depend among other things on the protein long-range interaction parameter and on the helicoidal coupling coefficient. Furthermore, we find that the amplitude and the width of the resulting breather solution, in the form of the bubble moving along the DNA molecule, are strongly influenced by the long-range and helicoidal interactions. This result shows a relevant length scale for real protein–DNA interaction.
QUANTUM MECHANICAL OBSERVERS AND TIME REPARAMETRIZATION SYMMETRY
Authors: KONISHI EIJI
Published: July 2012

We propose that the degree of freedom of measurement by quantum mechanical observers originates in the Goldstone mode of the spontaneously broken time reparametrization symmetry. Based on the classification of quantum states by their nonunitary temporal behavior as seen in the measurement processes, we describe the concepts of the quantum mechanical observers via the time reparametrization symmetry.
IMPACT OF THE ORDER PARAMETER SYMMETRIES ON THE VORTEX CORE STRUCTURE IN IRON-BASED SUPERCONDUCTORS
Authors: BELOVA POLINA , ZAKHARCHUK IVAN , TRAITO KONSTANTIN BORISOVICH , LÄHDERANTA ERKKI
Published: July 2012

Effects of the order parameter symmetries on the cutoff parameter ξh (determining the magnetic field distribution) in the mixed state are investigated in the framework of quasiclassical Eilenberger theory for isotropic s±, s++ and anisotropic dx2-y2-wave superconducting pairings. These symmetries are proposed for the pairing state of the Fe -pnictides. In s± pairing symmetry, the gap function has opposite sign at the electron and hole pockets of the Fermi surface, it is connected with interband antiferromagnetic spin fluctuations. In s++ pairing symmetry, the gap function has the same sign at the Fermi surface, it is mediated by moderate electron–phonon interaction due to Fe -ion oscillation and the critical orbital fluctuation. The dx2-y2 pairing symmetry can rise from intraband antiferromagnetic spin fluctuation in strongly hole overdoped iron pnictide KFe 2 As 2 and ternary chalcogenides. The s± pairing symmetry results in different effects of intraband (Γ0) and interband (Γπ) impurity scattering on ξh. It is found that ξh/ξc2 value decreases with Γ0 leading to the values much less than those predicted by the analytical Ginzburg–Landau (AGL) theory for high Γ0. At very high Γ0, the interband scattering suppresses ξh/ξc2 considerably below one in the whole field range making it flat for both s± and s++ pairing symmetries. Scaling of the cutoff parameter with the electromagnetic coherence length shows the importance of the nonlocal effects in mixed state. The small values of ξh/ξc2 were observed in μSR measurements of Co -doped BaFe 2 As 2. If Γ0 and Γπ are small and equal than the ξh/ξc2(B/Bc2) dependence for s± symmetry behaves like that of the AGL model and shows a minimum with value much more than that obtained for s++ superconductors. With high Γπ, the ξh/ξc2(B/Bc2) dependence resides above the AGL curve for s± pairing symmetry, as observed in SANS measurements of stoichiometrical LiFeAs compound. In d-wave superconductors, ξh/ξc2 always increases with Γ similar to the s± symmetry case with Γ0 = Γπ.
COLLISION EFFICIENCY OF BROWNIAN COAGULATION FOR NANOPARTICLES TAKING INTO ACCOUNT THE SLIP BOUNDARY CONDITION ON THE PARTICLE SURFACE
Authors: CHEN ZHONGLI , JIANG RENJIE , KU XIAOKE
Published: July 2012

The collision efficiency of Brownian coagulation for monodisperse nanoparticles is considered. A new expression for friction coefficient of particle pair is proposed based on an assumption from a statistical point of view and the relative diffusion coefficient is thus be modified in order to take into account this influence as well as the effects of slip. The modified diffusion coefficient increases the collision efficiency to some extent as expected whether van der Waals interparticle potential is considered or not. A comparison with experimental measurements shows the accuracy of the results predicted by modified theory and the necessity of considering the decrease of friction coefficient due to the random motion of nanoparticles as well as the slip effects arising from the finite mean free path of gas molecules.
TEMPERATURE DEPENDENCE OF ELECTRICAL RESISTANCE OF INDIVIDUAL CARBON NANOTUBES AND CARBON NANOTUBES NETWORK
Authors: DEHGHANI SAJJAD , MORAVVEJ-FARSHI MOHAMMAD KAZEM , SHEIKHI MOHAMMAD HOSSEIN
Published: July 2012

We present a model to understand the effect of temperature on the electrical resistance of individual semiconducting single wall carbon nanotubes (s-SWCNTs) of various diameters under various electric fields. The temperature dependence of the resistance of s-SWCNTs and metallic SWCNTs (m-SWCNTs) are compared. These results help us to understand the temperature dependence of the resistance of SWCNTs network. We experimentally examine the temperature dependence of the resistance of random networks of SWCNTs, prepared by dispersing CNTs in ethanol and drop-casting the solution on prefabricated metallic electrodes. Examining various samples with different electrode materials and spacings, we find that the dominant resistance in determination of the temperature dependence of resistance of the network is the resistance of individual tubes, rather than the tube–tube resistance or tube–metal contact resistance. It is also found that the tube–tube resistance depends on the electrode spacing and it is more important for larger electrode spacings. By applying high electric field to burn the all-metallic paths of the SWCNTs network, the temperature dependence of the resistance of s-SWCNTs is also examined. We also investigate the effect of acid treatment of CNTs on the temperature dependence of the resistance of SWCNTs and also multi-wall CNTs (MWCNTs) networks.
LOOSE MECHANOCHEMICAL COUPLING OF MOLECULAR MOTORS
Authors: ZHANG YUNXIN
Published: July 2012

In living cells, molecular motors convert chemical energy into mechanical work. Its thermodynamic energy efficiency, i.e. the ratio of output mechanical work to input chemical energy, is usually high. However, using two-state models, we found the motion of molecular motors is loosely coupled to the chemical cycle. Only part of the input energy can be converted into mechanical work. Others are dissipated into environment during substeps without contributions to the unidirectional movement.
NUMERICAL SIMULATION OF CELL ADHESION AND DETACHMENT IN MICROFLUIDICS
Authors: BAI BOFENG , LUO ZHENGYUAN , LU TIANJIAN , XU FENG
Published: July 2012

Inspired by the complex biophysical processes of cell adhesion and detachment under blood flow in vivo, numerous novel microfluidic devices have been developed to manipulate, capture, and separate bio-particles for various applications, such as cell analysis and cell enumeration. However, the underlying physical mechanisms are yet unclear, which has limited the further development of microfluidic devices and point-of-care (POC) systems. Mathematical modeling is an enabling tool to study the physical mechanisms of biological processes for its relative simplicity, low cost, and high efficiency. Recent development in computation technology for multiphase flow simulation enables the theoretical study of the complex flow processes of cell adhesion and detachment in microfluidics. Various mathematical methods (e.g., front tracking method, level set method, volume of fluid (VOF) method, fluid–solid interaction method, and particulate modeling method) have been developed to investigate the effects of cell properties (i.e., cell membrane, cytoplasma, and nucleus), flow conditions, and microchannel structures on cell adhesion and detachment in microfluidic channels. In this paper, with focus on our own simulation results, we review these methods and compare their advantages and disadvantages for cell adhesion/detachment modeling. The mathematical approaches discussed here would allow us to study microfluidics for cell capture and separation, and to develop more effective POC devices for disease diagnostics.
THE BIOMECHANICAL EFFECTS OF DIFFERENT INTERNAL FIXATIONS IN THE TREATMENT OF FEMORAL NECK FRACTURES
Authors: MA XIN-LONG , MA JIAN-XIONG , MA TAO , XING DAN , WANG JIE , YANG YANG , ZHU SHAO-WEN , MA BAO-YI , CHEN YANG , XU WEIGUO , WANG ZHI-BIN
Published: July 2012

The objective of this study was to contrast the biomechanical effects of standard internal fixations for femoral neck fracture treatment and provide a theoretical basis for the selection of the ideal internal fixation in the clinic.

Twelve artificial PMMA femoral models were selected, and the central necks of the specimens were sawn with a electric saw at Pauwels angle of 70° to form an adduction-type femoral neck fracture model. After anatomic reduction, we fixed the specimens respectively with the DHS, three hollow screws, PFN, and dynamic sleeve three-wing screw according to the operative approach. Instron-8874 servo-hydraulic mechanical testing machine was used to fix the specimens which simulated uniped standing. We selected 15 key points on the proximal femur as test points and gave the model gradation loading at the rate of 10 mm/min with linear load 0 ~ 1200 N. The strain of each point under 1200 N load, head sink displacement under different loads, and the strain of eight points on principal pressure side were measured.

A peak was observed at the eight resistance strain gages at 1200 N load, with the strain values of the DHS, three hollow screws, PFN, and dynamic sleeve three-wing screw were (-700 ± 35), (-756 ± 14), (-1362 ± 136), and (3024 ± 127) με, showing statistical significance (P < 0.01). Under the same load, the head sink displacement in the group with the dynamic sleeve three-wing screw was greater than the hollow screws and PFN groups (P < 0.01), but smaller than the DHS group (P < 0.01). The strain values at the eight resistance strain gages in the group with the dynamic sleeve three-wing screw was larger than the other three groups under the same load, showing statistical significance (P < 0.01), and the strain values demonstrated an increasing trend with the increase of load at the same fixation group.

The dynamic sleeve three-wing screw has good biomechanical stability for the treatment of femoral neck fractures, which can be applied in clinical practice.
AN ANALYSIS OF ENTREPRENEURSHIP ACROSS FIVE MAJOR NATIONALITY GROUPS IN THE UNITED ARAB EMIRATES
Authors: TONG QINGXIA , McCROHAN DECLAN , EROGUL MURAT SAKIR
Published: July 2012

The paper investigates differences in entrepreneurial activity, attitudes, aspirations, connectivity and behavior among nascent entrepreneurs across five key nationality groups residing in the United Arab Emirates (UAE). It also seeks to identify key differences between entrepreneurs and non-entrepreneurs' perceptions and attitudes toward entrepreneurship. More than 8000 adult residents were randomly surveyed as part of the GEM UAE studies conducted in 2006, 2007, 2009 and 2011. The findings indicate that the temporary residency status of expatriate workers has not prevented them from becoming entrepreneurs in the UAE. Arab expatriates in particular, have higher entrepreneurship rates compared to other nationality groups. Sharing a common culture and language appears to play a part in increased entrepreneurial activity. Moreover, socioeconomic factors like income and employment have a significant influence in determining entrepreneurship activity in the UAE. Regardless of nationality, entrepreneurs have more in common with each other compared to non-entrepreneurs in regards to their attitudes, connectivity and activities related to entrepreneurship, suggesting some homogenizing force that exists within the entrepreneurial population of the UAE.
ENTREPRENEURIAL CAPITAL: EXAMINING LINKAGES IN HUMAN AND SOCIAL CAPITAL OF NEW VENTURES
Authors: SCHENKEL MARK T. , D'SOUZA RODNEY R. , MATTHEWS CHARLES H.
Published: July 2012

Despite advancing extant theory, studies have tended to oversimplify the roles of human and social capital influences on nascent activity by underemphasizing the importance of motivational factors, construct dimensionality and context. This study seeks to extend previous efforts by investigating the relationship between various forms of human and social capital in the new venture creation process, both generally and across high and low technological contexts. Findings show that certain aspects of human capital are systematically related to certain aspects of social capital regardless of technological context, suggesting that nascent entrepreneurs may benefit more broadly from engaging in systematic efforts to construct certain types of social capital in support of venturing activities. Equally important, these findings support the central proposition that entrepreneurship theory and practice will benefit from more focused research efforts to generate insights into the dynamic relationships between individuals, their social worlds and entrepreneurial outcomes.
THE IMPACT OF PUBLIC PROGRAMS ON THE SURVIVAL AND PROFITS OF STARTUPS: EVIDENCE FROM A REGION OF SPAIN
Authors: ALONSO-NUEZ MARÍA J. , GALVE-GÓRRIZ CARMEN
Published: July 2012

In spite of their significance, the analyses of public subsidies for startups have been scant in the scientific literature. The focus has been more on justifying or arguing against the state's intervention through the granting of subsidies. The main aim of these public policies is to create companies by disadvantaged groups. Looking at the data we observe that the aim was achieved. Given this evidence, this paper analyzes how public programs that promote the creation of companies affect those companies' survival and net profits over a period of five years. Using a bivariate probit econometric model for a sample of businesses in a particular region of Spain, the results do not reveal the existence of differences, in terms of survival and profits, between companies created with and without public subsidies. The results do not support the arguments for or against the effectiveness of public programs, because subsidized companies neither survive longer nor have less net profits than unsubsidized companies.
AN ANALYSIS OF FUNDING DECISIONS FOR NICHE AGRICULTURAL PRODUCTS
Authors: VAN AUKEN HOWARD , CARRAHER SHAWN
Published: July 2012

This paper examines the flow of funds from providers of capital to niche agricultural users of capital. Various programs through the US government, state/local economic development and private agencies work to improve the flow of capital to the niche agricultural sector. However, despite the expansion of programs aimed at providing financial resources to the agricultural sector, many sectors remain poorly served. Previous studies have suggested that agencies need to facilitate the flow of capital to small agricultural firms. The results showed that providers of capital believed more technical assistance was the best way to increase the flow of capital to producers. However, few providers of capital provided technical support. Regression analysis showed that the number of applications funded was significantly associated with the (1) weak/no business plan and (2) age of funding agency, while the percent of funds committed was significantly associated with weak/no business plan. The results provide managerial implications that can be used by funding agencies and niche agricultural producers to better understand obstacles to capital acquisition. Agencies may better understand the lack of technical assistance advice, especially because of the role of technical assistance in developing business plans, financial strategies and collateral requirements.
Cerulein hyperstimulation decreases AMP-activated protein kinase levels at the site of maximal zymogen activation
Authors: Shugrue Christine A. , Alexandre Martine , de Villalvilla Alexander Diaz , Kolodecik Thomas R. , Young Lawrence H. , Gorelick Fred S. , Thrower Edwin C.
Published: July 2012

The premature activation of digestive enzyme zymogens in the pancreatic acinar cell is an important initiating event in acute pancreatitis. We have previously demonstrated that vacuolar ATPase (vATPase) activity is required for zymogen activation. Adenosine monophosphate-activated protein kinase (AMPK) regulates vATPase function in kidney and epididymal clear cells. To determine whether AMPK could affect pancreatitis responses, its effects were first examined in a cellular model of pancreatitis, cerulein-hyperstimulated (100 nM) pancreatic acini. This treatment caused a prominent increase in trypsin and chymotrypsin activities. Pretreatment with AICAR or metformin (AMPK activators) or compound C (an AMPK inhibitor) reduced or increased cerulein-induced zymogen activation, respectively. The association of the vATPase E subunit with membranes, a marker of its activation, tended to be inversely related to AMPK activity (assessed by AICAR and compound C treatments). Cerulein treatment did not change AMPK (α and β) levels but did lead to an increase in its activation (phosphorylation of Thr172) and induced the time-dependent translocation of the enzyme to a Triton-insoluble compartment. Basal in vivo studies showed that AMPK was widely distributed between membrane and soluble fractions generated by differential centrifugation. After cerulein hyperstimulation, AMPK levels selectively decreased in fractions containing the highest levels of active zymogens. These studies suggest that AMPK activity has a protective role in the pancreatic acinar cell that inhibits zymogen activation in the basal state, and this AMPK effect is reduced during pancreatitis. Therapies that prevent the selective reduction of AMPK in compartments that support zymogen activation could reduce injury during pancreatitis.
Sequence Complexity of Chromosome 3 inCaenorhabditis elegans
Authors: Pierro Gaetano
Published: July 2012

The nucleotide sequences complexity in chromosome 3 ofCaenorhabditis elegans(C. elegans) is studied. The complexity of these sequences is compared with some random sequences. Moreover, by using some parameters related to complexity such as fractal dimension and frequency, indicator matrix is given a first classification of sequences ofC. elegans. In particular, the sequences with highest and lowest fractal value are singled out. It is shown that the intrinsic nature of the low fractal dimension sequences has many common features with the random sequences.
Abstract 1740: Analogs of OSI-930 as potent ABCG2-mediated multidrug resistance reversal agents
Authors: Patel Jay P. , Kuang Ye-Hong , Sodani Kamlesh , Wu Chun-Pu , Liao Li-Qiu , Tiwari Amit K. , Dai Chun-ling , Chen Xiang , Fu Li-Wu , Ambudkar Suresh V. , Korlipara Vijaya L. , Chen Zhe-Sheng
Published: July 2012

OSI-930 {N-(4-trifluoromethoxyphenyl) 3-((quinolin-4-ylmethyl) amino) thiophene-2-carboxamide}, a dual c-Kit and KDR tyrosine kinase inhibitor, has been reported to be undergoing Phase I dose escalation study in cancer patients. A series of sixteen pyridyl and phenyl analogs (JP compounds) of OSI-930 was designed and synthesized. Extensive screening of these compounds led to the discovery that nitropyridyl and nitrophenyl analogs of OSI-930, JP1 and JP3, were effective in reversing ABC subfamily G member 2 (ABCG2/BCRP/MXR) transporter-mediated multidrug resistance (MDR). In the present study, JP1 and JP3 significantly sensitized ABCG2-expressing cells to established substrates of ABCG2 including mitoxantrone, SN-38 and doxorubicin in a concentration-dependent manner, but not to the non-ABCG2 substrate cisplatin. Furthermore, JP1 and JP3 were unable to reverse ABCB1- or ABCC1-mediated MDR indicating their selectivity for ABCG2. Western blot analysis was used to evaluate ABCG2 expression and it was found that neither JP1 nor JP3 significantly altered ABCG2 protein expression during the course of our experiment. Accumulation study with an ABCG2 substrate [3H]-mitoxantrone demonstrated that JP1 and JP3 increased the intracellular accumulation of [3H]-mitoxantrone. JP1 and JP3 also significantly inhibited the transport of [3H]-methotrexate by ABCG2 in the in vitro transport assays using membrane vesicles. Importantly, both JP1 and JP3 efficaciously stimulated the activity of ATPase of ABCG2 and inhibited the photoaffinity labeling of this transporter with its substrate [125I]-iodoarylazidoprazosin. Results from the present study suggest that analogs of OSI-930, JP1 and JP3, specifically inhibit the function of ABCG2 through direct interaction with its substrate binding site(s). Thus the OSI-930 analogs represent a new class of potential reversal compounds for the treatment of MDR in ABCG2 over-expressing tumors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1740. doi:10.1158/1538-7445.AM2011-1740