Spinons in Magnetic Chains of Arbitrary Spins at Finite Temperatures

The thermodynamics of solvable isotropic chains with arbitrary spins is addressed by the recently developed quantum transfer matrix (QTM) approach. The set of nonlinear equations which exactly characterize the free energy is derived by respecting the physical excitations at T=0, spinons and RSOS kinks. We argue the implication of the present formulation to spinon character formula of level k=2S SU(2) WZWN model .Comment: 25 pages, 8 Postscript figures, Latex 2e,uses graphicx, added figures and detailed discussion

Cosmic Dynamics of Bose-Einstein Condensates

A dynamical correspondence is established between positively curved, isotropic, perfect fluid cosmologies and quasi-two-dimensional, harmonically trapped Bose-Einstein condensates by mapping the equations of motion for both systems onto the one-dimensional Ermakov system. Parameters that characterize the physical properties of the condensate wavepacket, such as its width, momentum and energy, may be identified with the scale factor, Hubble expansion parameter and energy density of the universe, respectively. Different forms of cosmic matter correspond to different choices for the time-dependent trapping frequency of the condensate. The trapping frequency that mimics a radiation-dominated universe is determined.Comment: 12 pages, no figures. Extended discussion. In Press, Classical and Quantum Gravit

Analytic curves in algebraic varieties over number fields

We establish algebraicity criteria for formal germs of curves in algebraic varieties over number fields and apply them to derive a rationality criterion for formal germs of functions, which extends the classical rationality theorems of Borel-Dwork and P\'olya-Bertrandias valid over the projective line to arbitrary algebraic curves over a number field. The formulation and the proof of these criteria involve some basic notions in Arakelov geometry, combined with complex and rigid analytic geometry (notably, potential theory over complex and $p$-adic curves). We also discuss geometric analogues, pertaining to the algebraic geometry of projective surfaces, of these arithmetic criteria.Comment: 55 pages. To appear in "Algebra, Arithmetic, and Geometry: In Honor of Y.i. Manin", Y. Tschinkel & Yu. Manin editors, Birkh\"auser, 200

Возможности применения модель-базированных итеративных реконструкций при компьютерной томографии легких

Aim: A literature review of the possibilities of applying model iterative reconstruction (MIR) in computed tomography to improve image quality, including in low-dose scanning protocols.Materials and methods. The analysis of publications devoted to the application of MIR to reduce the radiation dose and improve the quality of images in CT diagnostics of lung pathology with an emphasis on the value of the achieved radiation dose was carried out.Results. The use of MIR eliminates digital noise from medical images, improving their quality. This feature can significantly reduce radiation exposure with low-dose protocols without loss of diagnostic quality. On average, application of MIR allows to reduce the radiation dose by 70% compared to a standard protocol, without increasing the noise level of CT images and maintaining the contrast-to-noise ratio. Previous studies have shown positive experience with the use of MIR in lung cancer screening programs and monitoring of cancer patients.Conclusion. The introduction of MIR in clinical practice can optimize the radiation exposure on the population without reducing the quality of CT images, however, the threshold dose to achieve a satisfactory image quality remains unexplored.Цель исследования: литературный обзор возможностей применения модельной итеративной реконструкции (МИР) при компьютерной томографии (КТ) для улучшения качества изображения, в том числе при низкодозовых протоколах сканирования.Материал и методы. Проведен анализ публикаций, посвященных применению МИР для снижения дозы облучения и улучшения качества изображений при КТ-диагностике патологии легких с акцентом на значение достигнутой дозы облучения.Результаты. Применение МИР позволяет устранять цифровой шум с медицинских изображений, улучшая их качество. Это свойство позволяет значительно снижать лучевую нагрузку при низкодозных протоколах без потери диагностического качества. В среднем использование МИР позволяет снизить дозу облучения на 70% по сравнению со стандартным протоколом, не повышая шумность КТ-изображений и сохраняя соотношение контраст/шум. Предыдущие исследования показали положительный опыт использования МИР в программах скрининга рака легкого и мониторинге онкологических пациентов.Заключение. Внедрение МИР в клиническую практику может оптимизировать лучевую нагрузку на популяцию, не снижая качество КТ-изображений, однако пороговые значения дозы облучения для достижения удовлетворительного качества изображения остаются неизученными

КОМПЬЮТЕРНАЯ ТОМОГРАФИЯ С ИСПОЛЬЗОВАНИЕМ МОДЕЛЬ-БАЗИРОВАННЫХ ИТЕРАТИВНЫХ РЕКОНСТРУКЦИЙ В КЛИНИЧЕСКОЙ ПРАКТИКЕ

Due to the widespread introduction of CT in clinical practice, the issue of reducing the radiation dose remains one of the most urgent. One of the ways to reduce radiation exposure is to improve the reconstruction algorithms of CT images. When using model interactive reconstruction, images are repeatedly processed to maximize the elimination of digital noise, which allows lowdose studies to be performed without compromising visual quality. The literature review presents the possibilities of applying model iterative reconstruction in CT studies of various organs and systems, including low-dose studies with a radiation exposure of less than 1 mSv, assessment the quality of studies and visualization of the pathology of various organs and systems. The most popular new technique is for screening studies, for example, for LDCT screening of lung cancer, and studies that require high resolution, for example, for CT-coronarography.В связи с широким внедрением КТ в клиническую практику вопрос о снижении дозы облучения остается одним из самых насущных. Одним из направлений снижения лучевой нагрузки является совершенствование алгоритмов реконструкции КТ-изображений. При использовании модельной интерактивной реконструкции изображения многократно  обрабатываются для максимального устранения цифрового шума, что позволяет выполнять низкодозовые исследования без снижения качества визуализации. В обзоре литературы представлены возможности применения модельной итеративной реконструкции при КТ-исследовании различных органов и систем, в том числе при низкодозовых исследованиях с дозой облучения менее 1 мЗв, оценка качества выполненных исследований и визуализации патологии различных органов и систем. Наиболее востребованной новая методика является для скрининговых исследований, например, для НДКТ-скрининга рака легкого, и исследований, в которых требуется высокое разрешение, например, для КТ- коронарографии

Оптимизация низкодозового протокола сканирования органов грудной клетки в диагностике очагов по типу «матового стекла» с применением алгоритмов итеративных реконструкций

Rapid development and implementation of the computed tomography (CT) in the Russian radiological practice reads to the significant increase in both the individual patient doses and collective dose of the Russian population from computed tomography.For the successful implementation of the optimization and dose reduction techniques it is necessary to develop and implement the methods of subjective (expert) image quality assessment. The current study was focused on the development of the composite method of the CT image quality assessment using an anthropomorphic chest phantom and imitators of the nodules for the detection of the ground-glass nodules. The method includes the detection of the nodules on the CT scan series as well as the assessment of the quality of the images using 5-grade Likert scale corresponding to the designed criteria. The method was evaluated for the development of the preliminary low-dose chest CT protocols using different reconstruction algorithms. The results of the study were based on the expert opinion of ten radiologists. They indicate the possibility of the significant (up to a factor of four) reduction of the effective doses of the patients related to the reduction of mAs for the CT scans of the chest for the detection of ground-glass nodules without a reduction in image quality. The best results corresponded to the algorithm of the model iterative reconstructions. Results of the study would be further evaluated on patients within a dedicated clinical trial.Стремительное развитие методов компьютерной томографии в отечественной радиологической практике приводит к росту как индивидуальных доз пациентов, так и коллективной дозы населения России от данного вида лучевой диагностики. Для успешного проведения мероприятий по снижению доз облучения пациентов необходимо разрабатывать и внедрять в практику методы субъективной (экспертной) оценки качества изображения. В данной работе представлена комплексная методика оценки качества КТ-изображений на примере диагностики очагов по типу «матового стекла» с использованием антропоморфного фантома органов грудной клетки и разработанных имитаторов очагов. Методика экспертной оценки включает в себя необходимость локализовать патологический очаг на серии КТ-сканов и оценить качество изображения по пятибалльной шкале Лайкерта в соответствии с представленными критериями. Методика была апробирована при определении потенциальных низкодозовых протоколов сканирования органов грудной клетки с использованием различных алгоритмов реконструкции. Результаты опроса десяти врачей-рентгенологов (экспертов) показали возможность существенного (вплоть до четырех раз) снижения эффективных доз пациентов за счет снижения экспозиции при проведении КТ-сканирования органов грудной клетки в выявлении очагов по типу «матового стекла» без значимого снижения качества изображения. При этом наилучшие результаты соответствовали использованию алгоритма модельных итеративных реконструкций. Результаты исследования будут использованы для клинической апробации на пациентах

Современные подходы к обеспечению качества диагностики в компьютерной томографии

To ensure the quality assurance of CT-examinations, it is necessary to obtain the high-quality diagnostic information and maintain the optimal exposure levels of patients and medical staff. This paper is focused on the requirements and main aspects of quality assurance of CT-examinations, which include quality control of the equipment, methods of CT-image quality control, optimization of radiation protection, as well as management of the unintended and accidental medical exposure. The paper contains recommendations on quality control of diagnostic equipment, methods for monitoring the quality control of CT-images, values of diagnostic reference levels for the detection of abnormally high patient doses and optimization of the radiation protection of patients, as well as the recommendations for management of radiation and non-radiation accidents. All main sections of the paper represent an unified quality assurance system in computed tomography.Обеспечение качества проведения компьютерно-томографических исследований способствует как получению необходимой диагностической информации, так и поддержанию оптимальных уровней облучения пациентов и персонала в этой области лучевой диагностики. В статье рассмотрены требования и основные аспекты обеспечения качества при проведении КТ-исследований, которые включают контроль качества оборудования, методики контроля качества КТ-изображения, методики проведения исследований, вопросы оптимизации радиационной защиты, а также предотвращения и расследования радиационных аварий. Все основные разделы статьи представляют из себя рекомендации по применению единой системы обеспечения качества проведения КТ-исследований

Oncogenic KRAS sensitises colorectal tumour cells to chemotherapy by p53-dependent induction of Noxa

BACKGROUND: Oxaliplatin and 5-fluorouracil (5-FU) currently form the backbone of conservative treatment in patients with metastatic colorectal cancer. Tumour responses to these agents are highly variable, but the underlying mechanisms are poorly understood. Our previous results have indicated that oncogenic KRAS in colorectal tumour cells sensitises these cells to chemotherapy. METHODS: FACS analysis was used to determine cell-cycle distribution and the percentage of apoptotic and mitotic cells. A multiplexed RT-PCR assay was used to identify KRAS-controlled apoptosis regulators after exposure to 5-FU or oxaliplatin. Lentiviral expression of short-hairpin RNAs was used to suppress p53 or Noxa. RESULTS: Oncogenic KRAS sensitised colorectal tumour cells to oxaliplatin and 5-FU in a p53-dependent manner and promoted p53 phosphorylation at Ser37 and Ser392, without affecting p53 stabilisation, p21 induction, or cell-cycle arrest. Chemotherapy-induced expression of the p53 target gene Noxa was selectively enhanced by oncogenic KRAS. Suppression of Noxa did not affect p21 induction or cell-cycle arrest, but reduced KRAS/p53-dependent apoptosis after exposure to chemotherapy in vitro and in tumour xenografts. Noxa suppression did not affect tumour growth per se, but strongly reduced the response of these tumours to chemotherapy. CONCLUSION: Oncogenic KRAS determines the cellular response to p53 activation by oxaliplatin or 5-FU, by facilitating apoptosis induction through Noxa. British Journal of Cancer (2010) 102, 1254-1264. doi: 10.1038/sj.bjc.6605633 www.bjcancer.com Published online 30 March 2010 (C) 2010 Cancer Research U

H2AX phosphorylation at the sites of DNA double-strand breaks in cultivated mammalian cells and tissues

A sequence variant of histone H2A called H2AX is one of the key components of chromatin involved in DNA damage response induced by different genotoxic stresses. Phosphorylated H2AX (γH2AX) is rapidly concentrated in chromatin domains around DNA double-strand breaks (DSBs) after the action of ionizing radiation or chemical agents and at stalled replication forks during replication stress. γH2AX foci could be easily detected in cell nuclei using immunofluorescence microscopy that allows to use γH2AX as a quantitative marker of DSBs in various applications. H2AX is phosphorylated in situ by ATM, ATR, and DNA-PK kinases that have distinct roles in different pathways of DSB repair. The γH2AX serves as a docking site for the accumulation of DNA repair proteins, and after rejoining of DSBs, it is released from chromatin. The molecular mechanism of γH2AX dephosphorylation is not clear. It is complicated and requires the activity of different proteins including phosphatases and chromatin-remodeling complexes. In this review, we summarize recently published data concerning the mechanisms and kinetics of γH2AX loss in normal cells and tissues as well as in those deficient in ATM, DNA-PK, and DSB repair proteins activity. The results of the latest scientific research of the low-dose irradiation phenomenon are presented including the bystander effect and the adaptive response estimated by γH2AX detection in cells and tissues

Cause of Death and Predictors of All-Cause Mortality in Anticoagulated Patients With Nonvalvular Atrial Fibrillation : Data From ROCKET AF

M. Kaste on työryhmän ROCKET AF Steering Comm jäsen.Background-Atrial fibrillation is associated with higher mortality. Identification of causes of death and contemporary risk factors for all-cause mortality may guide interventions. Methods and Results-In the Rivaroxaban Once Daily Oral Direct Factor Xa Inhibition Compared with Vitamin K Antagonism for Prevention of Stroke and Embolism Trial in Atrial Fibrillation (ROCKET AF) study, patients with nonvalvular atrial fibrillation were randomized to rivaroxaban or dose-adjusted warfarin. Cox proportional hazards regression with backward elimination identified factors at randomization that were independently associated with all-cause mortality in the 14 171 participants in the intention-to-treat population. The median age was 73 years, and the mean CHADS(2) score was 3.5. Over 1.9 years of median follow-up, 1214 (8.6%) patients died. Kaplan-Meier mortality rates were 4.2% at 1 year and 8.9% at 2 years. The majority of classified deaths (1081) were cardiovascular (72%), whereas only 6% were nonhemorrhagic stroke or systemic embolism. No significant difference in all-cause mortality was observed between the rivaroxaban and warfarin arms (P=0.15). Heart failure (hazard ratio 1.51, 95% CI 1.33-1.70, P= 75 years (hazard ratio 1.69, 95% CI 1.51-1.90, P Conclusions-In a large population of patients anticoagulated for nonvalvular atrial fibrillation, approximate to 7 in 10 deaths were cardiovascular, whereasPeer reviewe