Addictive links: The motivational value of adaptive link annotation

Adaptive link annotation is a popular adaptive navigation support technology. Empirical studies of adaptive annotation in the educational context have demonstrated that it can help students to acquire knowledge faster, improve learning outcomes, reduce navigational overhead, and encourage non-sequential navigation. In this paper, we present our exploration of a lesser known effect of adaptive annotation, its ability to significantly increase students' motivation to work with non-mandatory educational content. We explored this effect and confirmed its significance in the context of two different adaptive hypermedia systems. The paper presents and discusses the results of our work

The problem of quality assessing for the methods of coherence maps calculation in InSAR remote sensing of the Earth data processing

Interferometric coherence is an important indicator of the quality of interferograms obtained by synthetic aperture interferometric radars (InSAR), because the areas with low coherence are not suitable for interferometric data processing. The coherence value is used as a parameter for adaptive phase noise suppression algorithms. It can also be used for surface classification tasks. The paper investigates the problem of the coherence estimate reducing under the influence of the topographic phase slope and considers ways to reduce the impact of the slope on the estimate value. The paper presents a comparative efficiency analysis of four methods for coherence maps calculation used for the phase noise suppression on the interferograms by a spectral adaptive filter in interferometric data processing for the Earth's remote sensing space radar ALOS PALSAR. © Published under licence by IOP Publishing Ltd

Излучение преобразователем волноводного типа в соосные с ним конусные полупространства

Introduction. The present stage of development of hydroacoustic equipment is characterized by a constant improvement of an element base and by an increase in computing power. However, in solving of applied problems one is increasingly faced with a restriction on the realized bandwidth of electroacoustic transducers and antennas. The most of well-known methods of bandwidth expansion do not provide a linear character of the phase-frequency characteristic (PFC) of radiation in the working frequency band, which is of primary importance for the effective formation of relatively short, frequency-tunable, and complex acoustic signals. From this position, the use of a transducer of waveguide type (TWT) is preferential. Its construction and electrical excitation method provides a close to linear phase response of radiation.Aim. The development of a generalized computational model. It has to include particular cases of TWT radiation into cylindrical waveguides coaxial with it and into half-spaces, and also to take into account the influence of waves reflected from the boundaries of the TWT on its field characteristics.Materials and methods. The TWT was presented by a coaxial set of identical water filled piezocylinders with amplitude-phase excitation, provided a mode of broadband radiation in the form of traveling waves. The usage of the method of partial regions allowed one to obtain a solution of the problem of TWT radiation through water filled apertures into the conical adjacent half-spaces, variable in angle.Results. Frequency characteristics of TWT sound pressure results calculated in accordance with the solution of the synthesis problem in the frontal and rear directions for different angles of cone opening were presented and analyzed. Using the proposed computational model of TWT, the possibility of obtaining a bandwidth of the order of 3 octaves was demonstrated. An influence of the thickness of the passive flanges, which are used to link the TWT in the antennas was estimated. The possibility of radiation in the working frequency band of TWT of ultrashort ultra-short single-period pulses for different angles of cone opening was considered. A comparative assessment of the result of calculation with other particular solutions (the radiation by TWT in coaxial water-filled waveguides and also – in half-spaces) was presentedConclusion. An expedient to use a generalized computational model for a more accurate description of the acoustic fields of real antenna models made up of TWT was concluded.Введение. Современный этап развития гидроакустической техники характеризуется постоянным улучшением элементной базы и ростом вычислительных мощностей. На этом этапе при решении прикладных задач все чаще сталкиваются с ограничением ширины полосы пропускания электроакустических преобразователей и антенн. Большинство известных способов расширения полосы пропускания не обеспечивают линейность фазочастотной характеристики (ФЧХ) излучения в рабочей полосе частот, которая имеет первоочередное значение для эффективного формирования сравнительно коротких, перестраиваемых по частоте и сложных по структуре акустических сигналов. В связи с этим преимущественным является использование преобразователя волноводного типа (ПВТ), способ построения и электрического возбуждения которого обеспечивает близкую к линейной ФЧХ излучения.Цель работы. Разработка обобщенной расчетной модели, которая включает в себя частные случаи излучения ПВТ в соосные с ним цилиндрические волноводы и в полупространства, а также учитывает влияние волн, отраженных от границ ПВТ, на его полевые характеристики.Материалы и методы. ПВТ представлен соосным набором идентичных водозаполненных пьезоцилиндров с амплитудно-фазовым возбуждением, обеспечивающим режим широкополосного излучения по типу бегущей волны. Использование метода частичных областей позволяет решить задачу об излучении ПВТ через водозаполненные апертуры в граничащие с ними конусные полупространства с изменяемым углом раскрыва.Результаты. Приведены и проанализированы результаты расчетов частотных характеристик звукового давления при излучении ПВТ, возбуждаемых в соответствии с решением задачи синтеза, во фронтальном и тыльном направлениях для разных углов раскрыва конусов. С использованием предложенной расчетной модели ПВТ показана возможность получения полосы пропускания порядка трех октав. Оценивается влияние толщины пассивных фланцев, которые используются для компоновки ПВТ в антеннах. Рассматривается возможность излучения в рабочей полосе частот ПВТ перестраиваемых по частоте ультракоротких однопериодных импульсов для разных углов раскрыва конусов. Дается сопоставительная оценка результатов расчета с другими частными решениями: излучение ПВТ в соосные водозаполненные волноводы, а также – в полупространства.Заключение. Сделан вывод о целесообразности использования обобщенной расчетной модели для более точного описания акустических полей реальных макетов антенн, составленных из ПВТ

ДИНАМИКА СНЕГОЗАПАСОВ НА РАВНИННОЙ ТЕРРИТОРИИ РОССИИ В ЛЕСУ И В ПОЛЕ ПРИ КЛИМАТИЧЕСКИХ ИЗМЕНЕНИЯХ

In 1966-2010, snow surveys were simultaneously performed in forests and fields on the Russian plain territory. This made it possible to analyze characteristics of snow storages on fields and in forests as well as a dynamics of them under the present-day climate changes. Data of 81 weather stations located on the territory were used. According to data of these stations for the period 2001–2010 we obtained the following estimates for the maximal snow storage values, on average: for 20 stations located on the European territory of Russia to the north of 60° N –167 mmin forests and 162 on fields; for 44 stations to the south of 60° N – 118 and116 mm, respectively; for 10 stations in the south of West Siberia – 125 and107 mm; and for 7 stations in the East Siberia – 64 and70 mm. As one can see the last region is characterized by the opposite relation between forest and field conditions. Comparison of these values with similar data for the period 1966-2000 demonstrated that maximal snow storages decreased in forests by 7% but in fields they increased by 2%. The ratio of the maximum snow storage in the forest to their value in the field (i.e. a coefficient of snow reserve) for the periods 1981–1990, 1991–2000, and 2001–2010 are 1.15; 1.11 and 1.03, respectively. One of the reasons for the equalization of snow storage in forest and field may be changes of intensity and duration of snowstorms. In the calendar winters of 2001-2010, the average number of observations at weather stations with wind speeds over 10 m/s decreased relative to 1966-2010: in the European part of Russia by factor of 8.9 times, and in Western and Eastern Siberia – by 2.0 and 1.9 times, respectively. In the European part ofRussia, the number of observation periods when wind speed from 6 to 10 m/s was observed decreased by 1.9 times.Проведено сравнение снегозапасов в лесу и в поле за десятилетия с 1981 по 2010  г. Для метеостанций с наибольшей изменчивостью коэффициента снегозапасов на Европейской части России, в Западной и Восточной Сибири установлены изменения по десятилетиям числа наблюдений на метеостанциях со скоростями ветра в диапазоне 6–10 м/с и более

High activity redox catalysts synthesized by chemical vapor impregnation

The use of precious metals in heterogeneous catalysis relies on the preparation of small nanoparticles that are stable under reaction conditions. To date, most conventional routes used to prepare noble metal nanoparticles have drawbacks related to surface contamination, particle agglomeration, and reproducibility restraints. We have prepared titania-supported palladium (Pd) and platinum (Pt) catalysts using a simplified vapor deposition technique termed chemical vapor impregnation (CVI) that can be performed in any standard chemical laboratory. These materials, composed of nanoparticles typically below 3 nm in size, show remarkable activity under mild conditions for oxidation and hydrogenation reactions of industrial importance. We demonstrate the preparation of bimetallic Pd–Pt homogeneous alloy nanoparticles by this new CVI method, which show synergistic effects in toluene oxidation. The versatility of our CVI methodology to be able to tailor the composition and morphology of supported nanoparticles in an easily accessible and scalable manner is further demonstrated by the synthesis of Pdshell–Aucore nanoparticles using CVI deposition of Pd onto preformed Au nanoparticles supported on titania (prepared by sol immobilization) in addition to the presence of monometallic Au and Pd nanoparticles

ТОЛЩИНА СНЕЖНОГО ПОКРОВА НА ЛЕДНИКЕ ВОСТОЧНЫЙ ГРЁНФЬОРД (ШПИЦБЕРГЕН) ПО ДАННЫМ РАДАРНЫХ ИЗМЕРЕНИЙ И СТАНДАРТНЫХ СНЕГОМЕРНЫХ СЪЁМОК

Summary Comparison of two methods of measurements of snow cover thickness on the glacier Austre Grønfjordbreen, Svalbard was performed in the spring of 2014. These methods were the radar (500 MHz) observations and standard snow surveys. Measurements were conducted in 77 different points on the surface of the glacier. A good correlation (R2 = 0.98) was revealed. In comparison with the data of snow surveys, the radar measurements show a similar but more detailed pattern of the distribution of the snow cover depth. The discrepancy between the depths of snow cover on maps plotted from data of both methods did not exceed 30 cm in most parts of the glacier. The standard error of interpolation of the radar data onto the entire glacier surface amounts, on average, to 18 cm. This corresponds to the error of radar measurements of 18.8% when an average snow depth is about 160 cm and 9.4% at its maximum thickness of 320 cm. The distance between the measurement points at which the spatial covariance of the snow depth disappears falls between 236 and 283 m along the glacier, and between 117 and 165 m across its position. We compared the results of radar measurements of the pulse-delay time of reflections from the base of the snow cover with the data of manual probe measurements at 10 points and direct measurements of snow depth and average density in 12 snow pits. The average speed of radio waves propagation in the snow was determined as Vcr = 23.4±0.2 cm ns−1. This magnitude and the Looyenga and Kovacs formulas allowed estimating the average density of snow cover ρL = 353.1±13.1 kg m−3 and ρK = 337.4±12.9 kg m−3. The difference from average density measured in 12 pits ρav.meas = 387.4±12.9 kg m−3 amounts to −10.8% and −14.8%. In 2014, according to snow and radar measurements, altitudinal gradient of snow accumulation on the glacier Austre Grønfjordbreen was equal to 0.21 m/100 m, which is smaller than the average values (0.35 m/100 m). According to the results of snow measurements of 2011–2014, the average thickness of the snow cover on the glacier Austre Grønfjordbreen was by 17 cm greater than in 1979. In the very snowy year 2012, it was higher by 21.5 cm in comparison with the year 1979, and its spatial variability (standard deviation σН) had increased by 25.6 cm. Estimates of spatial and temporal variability of snow cover depth will be used to analyze the hydrothermal state of the glacier and its changes with regard to revealed features and climatic trends.Приведены результаты измерений толщины снежного покрова на леднике Восточный Грёнфьорд (Шпицберген) весной 2014 г. По этим данным оценена точность радиолокационных измерений толщины и средней плотности снежного покрова, а также их пространственная и временнáя изменчивость по сравнению со снегомерными измерениями 2011–2014 и 1979 гг

Тактика хирургического лечения пациентов с инфарктом мозжечка

The aim of the study is to specify tactics of surgical treatment of cerebellar infarction (CI).Material and methods. The results of treatment of 80 patients with CI were studied. According to the clinical course of stroke, the patients were divided into 2 groups. The group of malicious cerebellar infarction included 55 patients (69%) (Group I), the group cerebellar infarction with benign course included 25 patients (31%) (Group II). Patients of Group I were divided into subgroups, in one of them surgical treatment was performed (surgical subgroup), and in the another one, only conservative (conservative subgroup) treatment was performed. In the surgical subgroup, 16 patients underwent isolated ventriculostomy, 5 - posterior fossa decompression (PFD), 18 - combination of ventriculostomy and PFD. The criteria of efficacy of surgery were recovery of consciousness and/or IV ventricle and the quadrigeminal cistern configurations. Results of treatment were assessed according to the Glasgow Outcome Scale.Results. Malicious cerebellar infarctions occurred more frequently in patients with volume of ischemia exceeding 20 cm3 in the first day of the disease. The threshold value of mass effect, which may cause further a malocious cerebellar infarction, in the first day of the disease was score 3 according to the M. Jauss scale. In group of patients with malicious cerebellar infarction, surgical treatment reduced the mortality rate of occlusion and dislocation syndrome by 35.8%. The most effective type of intervention was a combination of decompressive trepanation of the posterior cranial fossa and external ventricular drainage. Combined ventriculostomy and PFD were 34 % more effective than just ventriculostomy, and 38 % more effective than just PFD.Conclusion. Patients with cerebellar infarction of more than 20 cm3 and signs of a mass effect in the posterior cranial fossa score 3 or higher according to M. Jauss scale, are prone to developing a malicious course of the disease. After the development of clinical manifestations of occlusive and dislocation syndrome, they need surgical treatment.In the surgical treatment of malignant cerebellar infarction, ventriculostomy with PFD are advisable, as each operation separately does not always provide a necessary effect in decompensation of dislocation syndrome.Цель исследования материал и методы. Исследованы результаты лечения 80 пациентов с ИМ. По характеру клинического течения ИМ пациенты были распределены на две группы. В группу злокачественного течения ИМ вошли 55 пациентов (69%) (группа I), в группу доброкачественного течения ИМ - 25 пациентов (31%) (группа II). Пациенты I группы были дополнительно разделены на подгруппы, в которых проводили хирургическое (хирургическая подгруппа) и только консервативное (консервативная подгруппа) лечение. В хирургической подгруппе 16 пациентов перенесли ликворошунтирующие операции (ЛО), 5 - декомпрессивную трепанацию задней черепной ямки (ДКТ ЗЧЯ), 18 - ЛО в сочетании с ДКТ ЗЧЯ. Критериями эффективности хирургического лечения считали восстановление сознания до ясного и/или восстановление конфигурации IV желудочка и четверохолмной цистерны. Результаты лечения оценивали по шкале исходов Глазго.Результаты. Злокачественное течение ИМ чаще возникало у пациентов с объемом ишемии, превышающим 20 см3 в 1-е сут заболевания. Пороговое значение масс-эффекта в первые сутки заболевания по шкале М. Jouss, которое может в последующем вызвать злокачественный ИМ, составило 3 балла. У больных со злокачественным ИМ хирургическое лечение позволило снизить летальность от окклюзионно-дислокационного синдрома (ОДС) на 35,8%. Эффективность хирургического лечения среди больных, которым выполнили ДКТ ЗЧЯ совместно с ЛО, была выше на 34% по сравнению с ЛО и на 38% по сравнению с результатами больных с изолированной ДКТ ЗЧЯ.Заключение. Пациенты с ИМ объемом более 20 см3, сопровождающимся масс-эффектом в ЗЧЯ 3 балла и более по шкале М. Jouss, склонны к развитию злокачественного течения заболевания. При развитии клинической картины ОДС им показано хирургическое лечение.При хирургическом лечении злокачественного ИМ целесообразно выполнять совместно с вентрикулостомией ДКТ ЗЧЯ, так как каждая операция по отдельности не исключает дальнейшего прогрессирования ОДС

In the Search For New Anticancer Drugs .28. Synthesis and Evaluation of Highly-Active Aminoxyl Labeled Amino-Acid Derivatives Containing the [N'-(2-Chloroethyl)-N'-Nitrosoamino]Carbonyl Group

WOS: A1994NX39000014PubMed ID: 7965680The aminoxyl (nitroxyl) labeled (2-chloroethyl)nitrosocarbamoyl (CNC) derivatives of amino acids, i.e., N-[[N'-(2-chloroethyl)N'-nitrosoamino] carbonyl]-A-(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl)amides, A = glycyl (10a), A = L-alanyl (10b), A = L-valyl (10c), A = L-phenylalanyl (10d), were synthesized and evaluated in vitro for their anticancer activities against the murine lymphocytic leukemia P388. Compounds 10a-d possessed activities ranging from 242 to 456% increase in life span (%ILS). All CDF1 male mice treated with the highly active compounds 10b and 10c at 12 mg/kg/day for 9 days were alive after 30 days. Compounds 10a-d were then tested in vivo against the murine lymphoid leukemia L1210. Compounds 10a-d exhibited, on day 60, a %ILS of 496, 663, 663, and 581, respectively. All CDF1 male mice treated with the highly active compounds 10b and 10c at 12 mg/kg/day for 9 days were alive after 60 days. The lipophilicities of compounds 10a-d were determined using the UV method. The %ILS parameters obtained against the P388 and L1210 tumor lines were correlated with the corresponding lipophilicities, and a trend was generally observed toward an increase in cytotoxicity with a concomitant decrease in hydrophobicity