Scattering Problems via Real-time Wave Packet Scattering

In this paper, we use a straightforward numerical method to solve scattering models in one-dimensional lattices based on a tight-binding band structure. We do this by using the wave packet approach to scattering, which presents a more intuitive physical picture than the traditional plane wave approach. Moreover, a general matrix diagonalization method that is easily accessible to undergraduate students taking a first course in quantum mechanics is used. Beginning with a brief review of wave packet transport in the continuum limit, comparisons are made with its counterpart in a lattice. The numerical results obtained through the diagonalization method are then benchmarked against analytic results. The case of a resonant dimer is investigated in the lattice, and several resonant values of the mean wave packet momentum are identified. The transmission coefficients obtained for a plane wave incident on a step potential and rectangular barrier are compared by investigating an equivalent scenario in a lattice. Lastly, we present several short simulations of the scattering process which emphasize how a simple methodology can be used to visualize some remarkable phenomena.Comment: 11 pages, 3 new figures added as "gateways" to the animation

Use of the GATE Monte Carlo package for dosimetry applications

6 pages, 3 figures - submitted to NIM A, presented by D. VisvikisInternational audienceOne of the roles for MC simulation studies is in the area of dosimetry. A number of different codes dedicated to dosimetry applications are available and widely used today, such as MCNP, EGSnrc and PTRAN. However, such codes do not easily facilitate the description of complicated 3D sources or emission tomography systems and associated data flow, which may be useful in different dosimetry application domains. Such problems can be overcome by the use of specific MC codes such as GATE, which is based on Geant4 libraries, providing a scripting interface with a number of advantages for the simulation of SPECT and PET systems. Despite this potential, its major disadvantage is in terms of efficiency involving long execution times for applications such as dosimetry. The strong points and disadvantages of GATE in comparison to other dosimetry specific codes are discussed and illustrated in terms of accuracy, efficiency and flexibility. A number of features, such as the use of voxelised and moving sources, as well as developments such as advanced visualisation tools and the development of dose estimation maps allowing GATE to be used for dosimetry applications are presented. In addition, different examples from dosimetry applications with GATE are given. Finally, future directions with respect to the use of GATE for dosimetry applications are outlined

GATE : a simulation toolkit for PET and SPECT

Monte Carlo simulation is an essential tool in emission tomography that can assist in the design of new medical imaging devices, the optimization of acquisition protocols, and the development or assessment of image reconstruction algorithms and correction techniques. GATE, the Geant4 Application for Tomographic Emission, encapsulates the Geant4 libraries to achieve a modular, versatile, scripted simulation toolkit adapted to the field of nuclear medicine. In particular, GATE allows the description of time-dependent phenomena such as source or detector movement, and source decay kinetics. This feature makes it possible to simulate time curves under realistic acquisition conditions and to test dynamic reconstruction algorithms. A public release of GATE licensed under the GNU Lesser General Public License can be downloaded at the address http://www-lphe.epfl.ch/GATE/

Experimental investigation on consolidation behavior of mud: Subreport 1. Methodology study

Due to the complex nature of mud consolidation within harbours, a robust and accurate guideline to evaluate the nautical depth is still under debate. Besides, alternative dredging techniques (e.g. mud conditioning/fluidising) have proven to be an applicable method to reduce dredging costs in a number of harbours. Yet, before one can define new criteria for nautical depth or implement new dredging techniques, a deeper understanding of the temporal evolution of rheological, mechanical and biological characteristics of mud is needed. In this study, we aim to improve the understanding of the rheological properties of consolidating mud by comparing the consolidation process of mud from 5 different locations namely the harbours of Zeebrugge (ZB) and Deurganckdok (DG) in Belgium, the harbours of Rotterdam (RO) and Ijmuiden (IJ) in the Netherlands and the Emden (EM) harbour in Germany. The main objectives of this project are to examine the effect of the consolidation process on the mechanical, rheological and biological characteristics of mud as well as to explain the differences in consolidation processes between muds from different origins.This sub-report describes the properties of different mud types used for the experiments as well as the experimental setup. The experimental setup includes a detailed description of the governing parameters, experimental design and measurement techniques conducted on two different consolidation columns, small and large

Treatment patterns in older patients with locally advanced head and neck squamous cell carcinoma:Results from an EORTC led survey

OBJECTIVES: We aimed to assess patterns of care delivered to older patients with locally advanced head and neck squamous cell carcinoma (LA-HNSCC), and to analyze the use of geriatric assessment (GA) and assessment of quality of life (QoL).MATERIALS AND METHODS: Members of the head and neck cancer group and the older task force of the European Organisation for Research and Treatment of Cancer (EORTC), members the European Head and Neck Society and members of national groups in Europe were asked to complete a questionnaire about treatment delivered, use of GA, and QoL assessment in older patients with LA-HNSCC.RESULTS: Investigators from 111 centers replied, including 90 (81.1%) academic centers, 16 (14.4%) community hospitals, and 5 (4.5%) private clinics. Large differences in treatment patterns were found. For instance, for oropharyngeal carcinoma, one third of the centers indicated that they treat &lt;5% of older patients with chemoradiation, while 18 centers (16.2%) treat &gt;40% of older patients with chemoradiation. Fourteen centers (12.6%) routinely perform GA, while 43 centers (38.7%) never do, and 39 centers (35.1%) sometimes do. QoL is assessed on a routine basis in one fifth of the centers.CONCLUSIONS: Large differences exist across institutions in the patterns of care delivered to older patients with LA-HNSCC. Prospective studies are required to learn how GA can guide treatment decisions, and how QoL and treatment outcome can be improved. For that, consensus on standard of care is essential.</p

Absence of cardiovascular manifestations in a haploinsufficient Tgfbr1 mouse model

Loeys-Dietz syndrome (LDS) is an autosomal dominant arterial aneurysm disease belonging to the spectrum of transforming growth factor β (TGFβ)-associated vasculopathies. In its most typical form it is characterized by the presence of hypertelorism, bifid uvula/cleft palate and aortic aneurysm and/or arterial tortuosity. LDS is caused by heterozygous loss of function mutations in the genes encoding TGFβ receptor 1 and 2 (TGFBR1 and -2), which lead to a paradoxical increase in TGFβ signaling. To address this apparent paradox and to gain more insight into the pathophysiology of aneurysmal disease, we characterized a new Tgfbr1 mouse model carrying a p.Y378*nonsense mutation. Study of the natural history in this model showed that homozygous mutant mice die during embryonic development due to defective vascularization. Heterozygous mutant mice aged 6 and 12 months were morphologically and (immuno)histochemically indistinguishable from wild-type mice. We show that the mutant allele is degraded by nonsense mediated mRNA decay, expected to result in haploinsufficiency of the mutant allele. Since this haploinsufficiency model does not result in cardiovascular malformations, it does not allow further study of the process of aneurysm formation. In addition to providing a comprehensive method for cardiovascular phenotyping in mice, the results of this study confirm that haploinsuffciency is not the underlying genetic mechanism in human LDS

Hybrid video quality prediction: reviewing video quality measurement for widening application scope

A tremendous number of objective video quality measurement algorithms have been developed during the last two decades. Most of them either measure a very limited aspect of the perceived video quality or they measure broad ranges of quality with limited prediction accuracy. This paper lists several perceptual artifacts that may be computationally measured in an isolated algorithm and some of the modeling approaches that have been proposed to predict the resulting quality from those algorithms. These algorithms usually have a very limited application scope but have been verified carefully. The paper continues with a review of some standardized and well-known video quality measurement algorithms that are meant for a wide range of applications, thus have a larger scope. Their individual artifacts prediction accuracy is usually lower but some of them were validated to perform sufficiently well for standardization. Several difficulties and shortcomings in developing a general purpose model with high prediction performance are identified such as a common objective quality scale or the behavior of individual indicators when confronted with stimuli that are out of their prediction scope. The paper concludes with a systematic framework approach to tackle the development of a hybrid video quality measurement in a joint research collaboration.Polish National Centre for Research and Development (NCRD) SP/I/1/77065/10, Swedish Governmental Agency for Innovation Systems (Vinnova

Epidemiological study of phylogenetic transmission clusters in a local HIV-1 epidemic reveals distinct differences between subtype B and non-B infections

<p>Abstract</p> <p>Background</p> <p>The number of HIV-1 infected individuals in the Western world continues to rise. More in-depth understanding of regional HIV-1 epidemics is necessary for the optimal design and adequate use of future prevention strategies. The use of a combination of phylogenetic analysis of HIV sequences, with data on patients' demographics, infection route, clinical information and laboratory results, will allow a better characterization of individuals responsible for local transmission.</p> <p>Methods</p> <p>Baseline HIV-1 <it>pol </it>sequences, obtained through routine drug-resistance testing, from 506 patients, newly diagnosed between 2001 and 2009, were used to construct phylogenetic trees and identify transmission-clusters. Patients' demographics, laboratory and clinical data, were retrieved anonymously. Statistical analysis was performed to identify subtype-specific and transmission-cluster-specific characteristics.</p> <p>Results</p> <p>Multivariate analysis showed significant differences between the 59.7% of individuals with subtype B infection and the 40.3% non-B infected individuals, with regard to route of transmission, origin, infection with <it>Chlamydia </it>(p = 0.01) and infection with Hepatitis C virus (p = 0.017). More and larger transmission-clusters were identified among the subtype B infections (p < 0.001). Overall, in multivariate analysis, clustering was significantly associated with Caucasian origin, infection through homosexual contact and younger age (all p < 0.001). Bivariate analysis additionally showed a correlation between clustering and syphilis (p < 0.001), higher CD4 counts (p = 0.002), <it>Chlamydia </it>infection (p = 0.013) and primary HIV (p = 0.017).</p> <p>Conclusions</p> <p>Combination of phylogenetics with demographic information, laboratory and clinical data, revealed that HIV-1 subtype B infected Caucasian men-who-have-sex-with-men with high prevalence of sexually transmitted diseases, account for the majority of local HIV-transmissions. This finding elucidates observed epidemiological trends through molecular analysis, and justifies sustained focus in prevention on this high risk group.</p

Trends in axillary lymph node dissection for early-stage breast cancer in Europe: Impact of evidence on practice

Background: Data from recently published trials have provided practice-changing recommendations for the surgical approach to the axilla in breast cancer. Patients with T1-2 lesions, treated with breast conservation, who have not received neoadjuvant chemotherapy and have 1\u20132 positive sentinel nodes (Z0011-criteria) may avoid axillary lymph node dissection (ALND). We aim to describe the dissemination of this practice in Europe over an extended period of time. Methods: Our source of data was the eusomaDB, a central data warehouse of prospectively collected information of the European Society of Breast Cancer Specialists (EUSOMA). We identified cases fulfilling Z0011-criteria from 2005 to 2016 from 34 European breast centers and report trends in ALND. Data derived from Germany, Italy, Belgium, Switzerland, Austria, and Netherlands. Results: 6671 patients fulfilled Z0011-criteria. Rates of ALND showed a statistically significant decrease from 2010 (89%) to 2011 (73%), reaching 46% in 2016 (p < 0.001). After multivariable analysis, factors associated with higher probability of ALND were earlier year of surgery, younger age, increasing tumor size and grade, and being operated in Italy (p < 0.001). The minimum and maximal rates of ALND in the most recent two-year period (2015\u20132016) were 0% and 83% in two centers located in different countries (p < 0.001). Conclusion: Our study demonstrates, a decrease in rates of ALND that started after year 2010 through the end of the study period. Wide differences were observed among centers and countries indicating the need to spread unified clinical guidelines in Europe to allow for homogeneous evidence-based practice patterns