bluuebunny/crossref_metadata_2025 huggingface dataset:
Measuring Students' Perceptions of Educational Environment in the PBL Program of Sharjah Medical College
Authors: Nosair Emad , Mirghani Zein , Mostafa Randa M.
Published: December 2015

Background

Students' perception of their educational environment has a significant impact on their behavior and academic progress. The recent worldwide usage of innovative problem-based learning (PBL) medical programs requires major changes in medical schools and their environments. Therefore, measuring students' perceptions of the complex PBL environment has become a critical necessity as a determinant of students' academic success and as a part of attaining the quality standards of education. Ours being a new medical college employing the PBL curriculum, it was important to measure the students' perception of the educational environment in order to identify the strengths and weaknesses of the curriculum and to plan for any future improvements.

Aim and Objectives

The aim of this study was to evaluate students' perceptions in the preclinical phase of the PBL educational environment in the College of Medicine, Sharjah Medical College, United Arab Emirates, and to recommend remedial procedures.

Material and Methods

In this cross-sectional study, the English version of the Dundee Ready Education Environment Measure (DREEM) inventory was submitted to 250 students in years 1, 2, and 3. The data were analyzed using the SPSS 20 software, and significance was taken at P ≤ 0.05. The survey was performed in a mid-semester week, ie, in March 2014. No ethical issues were encountered during the process of this study.

Results

Two-hundred and fifty students responded to the questionnaire (100% response rate). The overall DREEM score was 113.4/200 (56.7%). First-year students expressed higher overall significant level of perception (119.4/200) than second-year (107.4/200) and third-year (112.7/200) students. In addition, first-year students perceived their learning, teaching, and academic climates as more significant than the other two batches. The scores obtained in the five domains were as follows; 28/48 in perception of learning, 26/44 in perception of teaching, 18/32 in academic self-perceptions, 27/48 in perceptions of atmosphere, and 15/28 in social self-perceptions. First-year students achieved the highest score (18.7/32) in the academic self-perception, and second-year students achieved the lowest (16.5/32). The total score was significantly higher in female students than in male students (115.9 vs 108.1).

Conclusions

The present study revealed that the PBL environment is generally perceived positively by our medical students. Female students exhibited higher perception than male students. Nevertheless, areas such as curriculum overload and inadequate student support still require further fine-tuning and remedial measures.
Конечные автоматы и числа
Authors: Aleshin Stanislav Vladimirovich , Panteleev Pavel Anatolyevich
Published: December 2015

Изучаются конечно-автоматные представления числовых колец, которые возникают при рассмотрении класса линейных $p$-адических автоматов, вычисляющих однородные линейные функции с рациональными коэффициентами в кольце целых $p$-адических чисел. Конечные автоматы выступают как в роли элементов колец, так и в качестве операций. Кроме того, изучаются свойства диаграмм переходов линейных $p$-адических автоматов, реализующих функцию одной переменной $f(x)=cx$. В частности, найдены точные значения для числа их состояний и показано, что при $c>0$ их диаграммы обладают свойством, называемым самодвойственностью, обобщающим соответствующее понятие для булевых функций. Также получен критерий того, что автомат, реализующий функцию $f(x)=cx$, является перестановочным, и для всех таких автоматов полностью описаны группы, являющиеся их внутренними полугруппами.
О вырождении разложимых ветвящихся процессов
Authors: Vatutin Vladimir Alekseevich , Dyakonova Elena Evgen'evna
Published: December 2015

Исследуется асимптотическое поведение при $n\rightarrow \infty $ условного распределения числа частиц в разложимом критическом ветвящемся процессе $\mathbf{Z}(m)=(Z_{1}(m),\ldots,Z_{N}(m))$ с $N$ типами частиц в момент $m=n-k$, $k=o(n)$, при условии, что процесс выродился в момент $n$.
Исследование выполнено за счет гранта Российского научного фонда (проект № 14-50-00005).
Теория Галуа для клонов и суперклонов
Authors: Peryazev Nikolai Alekseevich , Sharankhaev Ivan Konstantinovich
Published: December 2015

Рассматриваются клоны (замкнутые множества операций, содержащие все проекции) и суперклоны над конечными множествами. Следуя А.И. Мальцеву, клон можно рассматривать как алгебру. Если в такой алгебре основное множество заменить на множество мультиопераций и добавить операцию разрешимости простейшего уравнения, то получим алгебру, называемую суперклоном. В работе устанавливается связь Галуа между клонами и суперклонами.
Работа выполнена при поддержке РФФИ, проект 12-01-000351a.
Образы конечного множества при итерациях двух случайных зависимых отображений
Authors: Serov Aleksandr Aleksandrovich
Published: December 2015

Пусть $\mathcal{N}$ - множество из $N$ элементов и $(F_1,G_1),(F_2,G_2),\ldots$ - последовательность независимых пар таких случайных зависимых отображений $\mathcal{N}\to\mathcal{N}$, что $F_k$ и $G_k$ - случайные равновероятные отображения и $\mathbf{P}\{F_k(x)=G_k(x)\}=\alpha$ для любого $x\in \mathcal{N}$ и всех $k=1,2,\ldots$ Для подмножества $S_0\subset \mathcal{N}$, $|S_0|=n$, рассматриваются последовательности его образов $S_k=F_k(\ldots F_2(F_1(S_0))\ldots)$, $T_k=G_k(\ldots G_2(G_1(S_0))\ldots)$, $k=1,2\ldots$, и последовательности их объединений $S_k\cup T_k$ и пересечений $S_k\cap T_k$, $k=1,2\ldots$ Получены двусторонние неравенства для $\mathbf{M}|S_k\cup T_k|$ и $\mathbf{M}|S_k\cap T_k|$, в которых верхние оценки асимптотически эквивалентны нижним, если $N,n,k\to\infty$, $nk=o(N)$ и $\alpha=O(\tfrac1N)$.
Исследование выполнено за счет гранта Российского научного фонда (проект № 14-50-00005).
Об одном подходе к преобразованию периодических последовательностей
Authors: Chirskii Vladimir Grigor'evich , Nesterenko Alexey Yur'evich
Published: December 2015

Исследуются арифметические свойства числа $\alpha = \sum_{k=0}^\infty \frac{c_k}{k!}$ в случае, когда последовательность коэффициентов $\{c_k\}_{k=0}^\infty$ является чисто периодической. В качестве приложения доказанных теорем предложено простое преобразование, позволяющее выработать из периодической последовательности $\{c_k\}_{k=0}^\infty$ непериодическую последовательность.
Updated ozone absorption cross section will reduce air quality compliance
Authors: Sofen E. D. , Evans M. J. , Lewis A. C.
Published: December 2015

Abstract. Photometric ozone measurements rely upon an accurate value of the ozone absorption cross section at 253.65 nm. This has recently been re-evaluated by Viallon et al. (2015) as 1.8 % smaller than the accepted value (Hearn, 1961) used for the preceding 50 years. Thus, ozone measurements that applied the older cross section systematically underestimate the amount of ozone in air. We correct the reported historical surface data from North America and Europe and find that this modest change in cross section has a significant impact on the number of locations that are out of compliance with air quality regulations if the air quality standards remain the same. We find 18, 23, and 20 % increases in the number of sites that are out of compliance with current US, Canadian, and European ozone air quality health standards for the year 2012. Should the new cross-section value be applied, it would impact attainment of air quality standards and compliance with relevant clean air acts, unless the air quality target values themselves were also changed proportionately. We draw attention to how a small change in gas metrology has a global impact on attainment and compliance with legal air quality standards. We suggest that further laboratory work to evaluate the new cross section is needed and suggest three possible technical and policy responses should the new cross section be adopted.
Absorption coefficient of urban aerosol in Nanjing, west Yangtze River Delta, China
Authors: Zhuang B. L. , Wang T. J. , Liu J. , Ma Y. , Yin C. Q. , Li S. , Xie M. , Han Y. , Zhu J. L. , Yang X. Q. , Fu C. B.
Published: December 2015

Abstract. Absorbing aerosols can significantly modulate short-wave solar radiation in the atmosphere, affecting regional and global climate. The aerosol absorption coefficient (AAC) is an indicator that assesses the impact of absorbing aerosols on radiative forcing. In this study, the near-surface AAC and absorption Ångström exponent (AAE) in the urban area of Nanjing, China, are characterized on the basis of measurements in 2012 and 2013 using the seven-channel Aethalometer (model AE-31, Magee Scientific, USA). The AAC is estimated with direct and indirect corrections, which result in consistent temporal variations and magnitudes of AAC at 532 nm. The mean AAC at 532 nm is about 43.23 ± 28.13 M m−1 in the urban area of Nanjing, which is much lower than that in Pearl River Delta and the same as in rural areas (Lin'an) in Yangtze River Delta. The AAC in the urban area of Nanjing shows strong seasonality (diurnal variations); it is high in cold seasons (at rush hour) and low in summer (in the afternoon). It also shows synoptic and quasi-2-week cycles in response to weather systems. Its frequency distribution follows a typical log-normal pattern. The 532 nm AAC ranging from 15 to 65 M m−1 dominates, accounting for more than 72 % of the total data samples in the entire study period. Frequent high pollution episodes, such as those observed in June 2012 and in winter 2013, greatly enhanced AAC and altered its temporal variations and frequency distributions. These episodes are mostly due to local emissions and regional pollution. Air masses flowing from northern China to Nanjing can sometimes be highly polluted and lead to high AAC at the site. AAE at 660/470 nm from the Schmid correction (Schmid et al., 2006) is about 1.56, which might be more reasonable than from the Weingartner correction (Weingartner et al., 2003). Low AAEs mainly occur in summer, likely due to high relative humidity (RH) in the season. AAC increases with increasing AAE at a fixed aerosol loading. The RH–AAC relationship is more complex. Overall, AAC peaks at RH values of around 40 % (1.3 < AAE < 1.6), 65 % (AAE < 1.3 and AAE > 1.6), and 80 % (1.3 < AAE < 1.6).
Contributions of dust and biomass burning to aerosols at a Colorado mountain-top site
Authors: Hallar A. G. , Petersen R. , Andrews E. , Michalsky J. , McCubbin I. B. , Ogren J. A.
Published: December 2015

Abstract. Visible Multifilter Rotating Shadowband Radiometer (vis-MFRSR) data were collected at Storm Peak Laboratory (SPL), a mountain-top facility in northwest Colorado, from 1999 to 2011 and in 2013. From 2011 to 2014, in situ measurements of aerosol light scattering were also obtained. Using these data sets together, the seasonal impact of dust and biomass burning is considered for the western USA. Analysis indicates that the median contributions to spring and summer aerosol optical depth (AOD) from dust and biomass-burning aerosols across the data set are comparable. The mean AOD is slightly greater in the summer, with significantly more frequent and short-duration high AOD measurements due to biomass-burning episodes than in the spring. The Ångström exponent showed a significant increase in the summer for both the in situ and vis-MFRSR data, suggesting an increase in combustion aerosols. Spring dust events are less distinguishable in the in situ data than the column measurement, suggesting that a significant amount of dust may be found above the elevation of SPL, 3220 m a.s.l. Twenty-two known case studies of intercontinental dust, regional dust, and biomass-burning events were investigated. These events were found to follow a similar pattern, in both aerosol loading and Ångström exponent, as the seasonal mean signal in both the vis-MFRSR and ground-based nephelometer. This data set highlights the wide-scale implications of a warmer, drier climate on visibility in the western USA.
The contribution of soil biogenic NO emissions from a managed hyper-arid ecosystem to the regional NO2 emissions during growing season
Authors: Mamtimin B. , Badawy M. , Behrendt T. , Meixner F. X. , Wagner T.
Published: December 2015

Abstract. A study was carried out to understand the contributions of soil biogenic NO emissions from managed (fertilized and irrigated) hyper-arid ecosystem in NW-China to the regional NO2 emissions during growing season. Soil biogenic NO emissions were quantified by laboratory incubation of corresponding soil samples. We have developed the Geoscience General Tool Package (GGTP) to obtain soil temperature, soil moisture and biogenic soil NO emission at oasis scale. Bottom-up anthropogenic NO2 emissions have been scaled down from annual to monthly values to compare mean monthly soil biogenic NO2 emissions. The top-down emission estimates have been derived from satellite observations compared then with the bottom-up emission estimates (anthropogenic and biogenic). The results show that the soil biogenic emissions of NO2 during the growing period are (at least) equal until twofold of the related anthropogenic sources. We found that the grape soils are the main summertime contributor to the biogenic NO emissions of study area, followed by cotton soils. The top-down and bottom-up emission estimates were shown to be useful methods to estimate the monthly/seasonal cycle of the total regional NO2 emissions. The resulting total NO2 emissions show a strong peak in winter and a secondary peak in summer, providing confidence in the method. These findings provide strong evidence that biogenic emissions from soils of managed drylands (irrigated and fertilized) in the growing period can be much more important contributors to the regional NO2 budget (hence to regional photochemistry) of dryland regions than thought before.
Passive air sampling of gaseous elemental mercury: a critical review
Authors: McLagan D. S. , Mazur M. E. E. , Mitchell C. P. J. , Wania F.
Published: December 2015

Abstract. Because gaseous elemental mercury (GEM) is distributed globally through the atmosphere, reliable means of measuring its concentrations in air are important. Passive air samplers (PASs), designed to be cheap, simple to operate, and to work without electricity, could provide an alternative to established active sampling techniques in applications such as (1) long term monitoring of atmospheric GEM levels in remote regions and in developing countries, (2) atmospheric mercury source identification and characterisation through finely-resolved spatial mapping, and (3) the recording of personal exposure to GEM. An effective GEM PAS requires a tightly constrained sampling rate, a large and stable uptake capacity, and a sensitive analytical technique. None of the GEM PASs developed to date achieves levels of accuracy and precision sufficient for the reliable determination of background concentrations over extended deployments. This is due to (1) sampling rates that vary due to meteorological factors and manufacturing inconsistencies and/or (2) an often low, irreproducible and/or unstable uptake capacity of the employed sorbents. While we identify shortcomings of existing GEM PAS, we also reveal potential routes to overcome those difficulties. Activated carbon and nano-structured metal surfaces hold promise as effective sorbents. Sampler designs incorporating diffusive barriers should be able to notably reduce the influence of wind on sampling rates.
The real part of the refractive indices and effective densities for chemically segregated ambient aerosols in Guangzhou by a single particle aerosol mass spectrometer
Authors: Zhang G. , Bi X. , Qiu N. , Han B. , Lin Q. , Peng L. , Chen D. , Wang X. , Peng P. , Sheng G. , Zhou Z.
Published: December 2015

Abstract. Microphysical properties of atmospheric aerosols are essential to better evaluate their radiative forcing. This paper first presents an estimate of the real part of the refractive indices (n) and effective densities (ρeff) of chemically segregated atmospheric aerosols in China. Vacuum aerodynamic diameter, chemical compositions, and light scattering intensities of individual particles were simultaneously measured by a single particle aerosol mass spectrometer (SPAMS) during fall of 2012 in Guangzhou. On the basis of Mie theory, n and ρeff were estimated for 17 particle types in four categories: organics (OC), elemental carbon (EC), internally mixed EC and OC (ECOC), and metal rich, respectively. Results indicate the presence of spherical or nearly spherical shape for majority of particle types, whose partial scattering cross section vs. sizes were well fitted to Mie theoretical modeling results. While sharing n in a narrow range (1.47–1.53), majority of particle types exhibited a wide range of ρeff (0.87–1.51 g cm−3). OC group is associated with the lowest ρeff (0.87–1.07 g cm−3), while metal rich group with the highest ones (1.29–1.51 g cm−3). It is noteworthy that a specific EC type exhibits a complex scattering curve vs. size due to the presence of both compact and irregularly shape particles. Overall, the results on detailed relationship between physical and chemical properties benefits future researches on the impact of aerosols on visibility and climate.
The importance of vehicle emissions as a source of atmospheric ammonia in the megacity of Shanghai
Authors: Chang Y. H. , Zou Z. , Deng C. R. , Huang K. , Collett J. L. , Lin J. , Zhuang G. S.
Published: December 2015

Abstract. Agricultural activities are a major source contributing to NH3 emissions in Shanghai and most other regions of China; however, there is a long-standing and ongoing controversy regarding the contributions of vehicle-emitted NH3 to the urban atmosphere. From April 2014 to April 2015, we conducted measurements of a wide range of gases (including NH3) and the chemical properties of PM2.5 at hourly resolution at a Shanghai urban supersite. This large dataset shows NH3 pollution events, lasting several hours with concentrations four times the annual average of 5.3 μg m-3, caused by the burning of crop residues in spring. There are also generally higher NH3 concentrations (mean ± 1σ) in summer (7.3 ± 4.9 μg m-3; n = 2181) because of intensive emissions from temperature-dependent agricultural sources. However, the NH3 concentration in summer was only an average of 2.4 μg m-3 or 41 % higher than the average NH3 concentration of other seasons. Furthermore, the NH3 concentration in winter (5.0 ± 3.7 μg m-3; n = 2113) was similar to that in spring (5.1 ± 3.8 μg m-3; n = 2204) but slightly higher, on average, than that in autumn (4.5 ± 2.3 μg m-3; n = 1949). Moreover, other meteorological parameters like planetary boundary layer height and relative humidity were not major factors affecting seasonal NH3 concentrations. These findings suggest that there may be some climate-independent NH3 sources present in the Shanghai urban area. Independent of season, the concentrations of both NH3 and CO present a marked bimodal diurnal profile, with maxima in the morning and the evening. A spatial analysis suggests that elevated concentrations of NH3 are often associated with transport from regions west-northwest and east-southeast of the city, areas with dense road systems. The spatial origin of NH3 and the diurnal concentration profile together suggest the importance of vehicle-derived NH3 associated with daily commuting in the urban environment. To further examine vehicular NH3 emissions and transport, sampling of the NH3 concentration was performed in (from the entrance to the exit of the tunnel) and out (along a roadside transect spanning 310 m perpendicular to the tunnel) of a heavily trafficked urban tunnel during the spring 2014. NH3 concentrations in the tunnel exit were over 5 and 11 times higher than those in the tunnel entrance and in the ambient air, respectively. Based on the derived mileage-based NH3 emission factor of 28 mg km-1, a population of 3.04 million vehicles in Shanghai produced around 1300 t NH3 in 2014, which accounts for 12 % of total NH3 emissions in the urban area. Collectively, our results clearly show that vehicle emissions associated with combustion are an important NH3 source in Shanghai urban areas and may have potential implications for PM2.5 pollution in the urban atmosphere.
Impact of the Asian monsoon on the extratropical lower stratosphere: trace gas observations during TACTS over Europe 2012
Authors: Müller S. , Hoor P. , Bozem H. , Gute E. , Vogel B. , Zahn A. , Bönisch H. , Keber T. , Krämer M. , Rolf C. , Riese M. , Schlager H. , Engel A.
Published: December 2015

Abstract. The transport of air masses originating from the Asian monsoon anticyclone into the extratropical upper troposphere and lower stratosphere (Ex-UTLS) above potential temperatures Θ = 380 K was identified during the HALO aircraft mission TACTS in August and September 2012. In-situ measurements of CO, O3 and N2O during TACTS Flight 2 on the 30 August 2012 show the irreversible mixing of aged with younger (originating from the troposphere) stratospheric air masses within the Ex-UTLS. Backward trajectories calculated with the trajetory module of the CLaMS model indicate that these tropospherically affected air masses originate from the Asian monsoon anticyclone. From the monsoon circulation region these air masses are quasi-isentropically transported above Θ = 380 K into the Ex-UTLS where they subsequently mix with stratospheric air masses. The overall trace gas distribution measured during TACTS shows that this transport pathway has a significant impact on the Ex-UTLS during boreal summer and autumn. This leads to an intensification of the tropospheric influence on the Ex-UTLS with ΔΘ > 30 K (relative to the tropopause) within three weeks during the TACTS mission. In the same time period a weakening of the tropospheric influence on the lowermost stratosphere (LMS) is determined. Therefore, the study shows that the transport of air masses originating from the Asian summer monsoon region within the lower stratosphere above Θ = 380 K is of major importance for the change of the chemical composition of the Ex-UTLS from summer to autumn.
MIX: a mosaic Asian anthropogenic emission inventory for the MICS-Asia and the HTAP projects
Authors: Li M. , Zhang Q. , Kurokawa J. , Woo J.-H. , He K. B. , Lu Z. , Ohara T. , Song Y. , Streets D. G. , Carmichael G. R. , Cheng Y. F. , Hong C. P. , Huo H. , Jiang X. J. , Kang S. C. , Liu F. , Su H. , Zheng B.
Published: December 2015

Abstract. An anthropogenic emission inventory for Asia is developed for the years 2008 and 2010 to support the Model Inter-Comparison Study for Asia (MICS-Asia) and the Task Force on Hemispheric Transport of Air Pollution (TF HTAP) projects by a mosaic of up-to-date regional emission inventories. Emissions are estimated for all major anthropogenic sources in 30 countries and regions in Asia. We conducted detailed comparisons of different regional emission inventories and incorporated the best-available ones for each region into the mosaic inventory at a uniform spatial and temporal resolution. We estimate the total Asian emissions of ten species in 2010 as follows: 51.3 Tg SO2, 52.1 Tg NOx, 336.6 Tg CO, 67.0 Tg NMVOC (non-methane volatile organic compounds), 28.8 Tg NH3, 31.7 Tg PM10, 22.7 Tg PM2.5, 3.5 Tg BC, 8.3 Tg OC and 17.3 Pg CO2. Emissions from China and India dominate the emissions of Asia for most of the species. We also estimated Asian emissions in 2006 using the same methodology of MIX. The relative change rates of Asian emissions for the period of 2006–2010 are estimated as follows: −8.0 % for SO2, +19 % for NOx, +4 % for CO, +15 % for NMVOC, +2 % for NH3, −3 % for PM10, −2 % for PM2.5, +6 % for BC, +2 % for OC and +20 % for CO2. Model-ready speciated NMVOC emissions for SAPRC-99 and CB05 mechanisms were developed following a profile-assignment approach. Monthly gridded emissions at a spatial resolution of 0.25° × 0.25° are developed and can be accessed from http://www.meicmodel.org/dataset-mix.
A total sky cloud detection method using real clear sky background
Authors: Yang J. , Min Q. , Lu W. , Ma Y. , Yao W. , Lu T. , Du J. , Liu G.
Published: December 2015

Abstract. The brightness distribution of sky background is usually non-uniform, which creates many problems for traditional cloud detection methods including the failure of thin cloud detection in total sky images and significantly reducing retrieval accuracy in the circumsolar and near-horizon regions. This paper describes the development of a new cloud detection algorithm, named "clear sky background differencing (CSBD)", which is accomplished by differencing the original image and the corresponding clear sky background image using the images' green channel. First, a library of clear sky background images with a variety of solar elevation angles needs to be developed. The image rotation and image brightness adjustment algorithms are applied to ensure the two images being differenced have the same solar position and similar brightness distribution. Sensitivity tests show, as long as the positions of the sun in the two images are the same, the cloud detection results are satisfactory. Several experimental cases show that the CSBD algorithm obtains good cloud recognition results visually, especially for thin clouds.
Carbon dynamics in highly heterotrophic subarctic thaw ponds
Authors: Roiha T. , Laurion I. , Rautio M.
Published: December 2015

Abstract. Global warming has accelerated the formation of permafrost thaw ponds in several subarctic and arctic regions. These ponds are net heterotrophic as evidenced by their greenhouse gas (GHG) supersaturation levels (CO2 and CH4), and generally receive large terrestrial carbon inputs from the thawing and eroding permafrost. We measured seasonal and vertical variations in the concentration and type of dissolved organic matter (DOM) in five subarctic thaw (thermokarst) ponds in northern Quebec, and explored how environmental gradients influenced heterotrophic and phototrophic biomass and productivity. Late winter DOM had low aromaticity indicating reduced inputs of terrestrial carbon, while the high concentration of dissolved organic carbon (DOC) suggests that some production of non-chromophoric dissolved compounds by the microbial food web took place under the ice cover. Summer DOM had a strong terrestrial signature, but was also characterized with significant inputs of algal-derived carbon, especially at the pond surface. During late winter, bacterial production was low (maximum of 0.8 mg C m−3 d−1) and was largely based on free-living bacterioplankton (58 %). Bacterial production in summer was high (up to 58 mg C m−3 d−1), dominated by particle-attached bacteria (67 %), and strongly correlated with the amount of terrestrial carbon. Primary production was restricted to summer surface waters due to strong light limitation deeper in the water column or in winter. The phototrophic biomass was equal to the heterotrophic biomass, but as the algae were mostly composed of mixotrophic species, most probably they used bacteria rather than solar energy in such shaded ponds. Our results point to a strong heterotrophic energy pathway in these thaw pond ecosystems, where bacterioplankton dominates the production of new carbon biomass in both summer and winter.
Dynamics of N2 fixation and fate of diazotroph-derived nitrogen in a low nutrient low chlorophyll ecosystem: results from the VAHINE mesocosm experiment (New Caledonia)
Authors: Bonnet S. , Berthelot H. , Turk-Kubo K. , Fawcett S. , Rahav E. , l'Helguen S. , Berman-Frank I.
Published: December 2015

Abstract. N2 fixation rates were measured daily in large (~ 50 m3) mesocosms deployed in the tropical South West Pacific coastal ocean (New Caledonia) to investigate the spatial and temporal dynamics of diazotrophy and the fate of diazotroph-derived nitrogen (DDN) in a low nutrient, low chlorophyll ecosystem. The mesocosms were intentionally fertilized with ~ 0.8 μM dissolved inorganic phosphorus (DIP) to stimulate diazotrophy. Bulk N2 fixation rates were replicable between the three mesocosms, averaged 18.5 ± 1.1 nmol N L−1 d−1 over the 23 days, and increased by a factor of two during the second half of the experiment (days 15 to 23) to reach 27.3 ± 1.0 nmol N L−1 d−1. These rates are higher than the upper range reported for the global ocean, indicating that the waters surrounding New Caledonia are particularly favourable for N2 fixation. During the 23 days of the experiment, N2 fixation rates were positively correlated with seawater temperature, primary production, bacterial production, standing stocks of particulate organic carbon, nitrogen and phosphorus, and alkaline phosphatase activity, and negatively correlated with DIP concentrations, DIP turnover time, nitrate, and dissolved organic nitrogen and phosphorus concentrations. The fate of DDN was investigated during the bloom of the unicellular diazotroph, UCYN-C, that occurred during the second half of the experiment. Quantification of diazotrophs in the sediment traps indicates that ~ 10 % of UCYN-C from the water column were exported daily to the traps, representing as much as 22.4 ± 5.5 % of the total POC exported at the height of the UCYN-C bloom. This export was mainly due to the aggregation of small (5.7 ± 0.8 μm) UCYN-C cells into large (100–500 μm) aggregates. During the same time period, a DDN transfer experiment based on high-resolution nanometer scale secondary ion mass spectrometry (nanoSIMS) coupled with 15N2 isotopic labelling revealed that 16 ± 6 % of the DDN was released to the dissolved pool and 21 ± 4 % was transferred to non-diazotrophic plankton, mainly picoplankton (18 ± 4 %) followed by diatoms (3 ± 2 %) within 24 h of incubation. This is consistent with the observed dramatic increase in picoplankton and diatom abundances, primary production, bacterial production and standing stocks of particulate organic carbon, nitrogen and phosphorus during the second half of the experiment in the mesocosms. These results offer insights into the fate of DDN during a bloom of UCYN-C in low nutrient, low chlorophyll ecosystems.
Direct uptake of organic carbon by grass roots and allocation in leaves and phytoliths: 13C labeling evidence
Authors: Alexandre A. , Balesdent J. , Cazevieille P. , Chevassus-Rosset C. , Signoret P. , Mazur J.-C. , Harutyunyan A. , Doelsch E. , Basile-Doelsch I. , Miche H. , Santos G. M.
Published: December 2015

Abstract. In the rhizosphere, the uptake of low molecular weight carbon (C) and nitrogen (N) by plant roots has been well documented. While organic N uptake relatively to total uptake is important, organic C uptake is supposed to be low relatively to the plant's C budget. Recently, radiocarbon analyses demonstrated that a fraction of C from the soil was occluded in amorphous silica micrometric particles that precipitate in plant cells (phytoliths). Here, we investigated whether and in which extent organic C absorbed by grass roots, under the form of either intact amino acids (AAs) or microbial metabolites, can feed the organic C occluded in phytoliths. For this purpose we added 13C- and 15N-labeled AAs to the silicon-rich hydroponic solution of the grass Festuca arundinacea. The experiment was designed to prevent C leakage from the labeled nutritive solution to the chamber atmosphere. After 14 days of growth, the 13C and 15N enrichments (13C-excess and 15N-excess) in the roots, stems and leaves, and phytoliths, as well as the 13C-excess in AAs extracted from roots and stems and leaves, were quantified relatively to a control experiment in which no labelled AAs were added. The net uptake of 13C derived from the labeled AAs supplied to the nutritive solution (AA-13C) by Festuca arundinacea represented 4.5 % of the total AA-13C supply. AA-13C fixed in the plant represented only 0.13 % of total C. However, the experimental conditions may have underestimated the extent of the process under natural and field conditions. Previous studies showed that 15N and 13C can be absorbed by the roots in several organic and inorganic forms. In the present experiment, the fact that phenylalanine and methionine, that were supplied in high amount to the nutritive solution, were more 13C-enriched than other AAs in the roots and stems and leaves strongly suggested that part of AA-13C was absorbed and translocated in its original AA form. The concentration of AA-13C represented only 0.15 % of the phytolith C (phytC) but was still 1.5 times higher in phytoliths than in leaves supporting that, ultimately, AA-13C was preferentially fixed in organic compounds subject to occlusion in phytoliths. Plausible forms of AA-13C and AA-15N absorbed and translocated, AA-13C fixation in phytoliths and implication of our finding for our understanding of the C cycle at the plant-soil interface are discussed.
Assessing the uncertainty of glacier mass-balance simulations in the European Arctic based on variance decomposition
Authors: Sauter T. , Obleitner F.
Published: December 2015

Abstract. State-of-the-art numerical snowpack models essentially rely on observational data for initialization, forcing, parametrization, and validation. Such data are available in increasing amounts, but the propagation of related uncertainties in simulation results has received rather limited attention so far. Depending on their complexity, even small errors can have a profound effect on simulations, which dilutes our confidence in the results. This paper aims at quantification of the overall and fractional contributions of some archetypical measurement uncertainties on snowpack simulations in arctic environments. The sensitivity pattern is studied at two sites representing the accumulation and ablation area of the Kongsvegen glacier (Svalbard), using the snowpack scheme Crocus. The contribution of measurement errors on model output variance, either alone or by interaction, is decomposed using global sensitivity analysis. This allows one to investigate the temporal evolution of the fractional contribution of different factors on key model output metrics, which provides a more detailed understanding of the model's sensitivity pattern. The analysis demonstrates that the specified uncertainties in precipitation and long-wave radiation forcings had a strong influence on the calculated surface-height changes and surface-energy balance components. The model output sensitivity patterns also revealed some characteristic seasonal imprints. For example, uncertainties in long-wave radiation affect the calculated surface-energy balance throughout the year at both study sites, while precipitation exerted the most influence during the winter and at the upper site. Such findings are valuable for identifying critical parameters and improving their measurement; correspondingly, updated simulations may shed new light on the confidence of results from snow or glacier mass- and energy-balance models. This is relevant for many applications, for example in the fields of avalanche and hydrological forecasting.
An integrated Dissolved Organic Carbon Dynamics Model (DOCDM 1.0): model development and a case study in the Alaskan Yukon River Basin
Authors: Lu X. , Zhuang Q.
Published: December 2015

Abstract. Quantitative understanding of the variation in dissolved organic carbon (DOC) is important to studying the terrestrial ecosystem carbon cycle. This study presents a process-based, dissolved organic carbon dynamics model (DOCDM 1.0) that couples the soil heat conduction, water flow, DOC production, mineralization and transport in both surface and subsurface of soil profile to quantify DOC dynamics in boreal terrestrial ecosystems. The model is first evaluated and then applied for a watershed in Alaska to investigate its DOC production and transport. We find that 42 and 27 % of precipitation infiltrates to soils in 2004, a warmer year, and in 1976, a colder year, respectively. Under warming conditions, DOC transported via overland flow does not show the expected decrease trend while the overland DOC yield shows a 4 % increase. The horizontal subsurface flow only accounts for 1–2 % of total water flux, but transports 30–50 % of DOC into rivers. Water flush due to water infiltration controls DOC transport. Snowmelt plays a noticeable role in DOC flush-out and DOC transport significantly depends on flowpaths in the study region. High soil temperature stimulates DOC production. The overland DOC export does not necessarily follow the DOC downward trend in surface water transport. Overall, this study shows that DOC export behavior is complex under changing temperature and hydrological conditions in cold-region watersheds. To adequately quantify DOC dynamics in northern high latitudes, more DOC and hydrological data are needed to better parameterize and test the developed model before extrapolating it to the region.
From meteorological to hydrological drought using standardised indicators
Authors: Barker L. J. , Hannaford J. , Chiverton A. , Svensson C.
Published: December 2015

Abstract. Drought monitoring and early warning (M&EW) systems are a crucial component of drought preparedness. M&EW systems typically make use of drought indicators such as the Standardised Precipitation Index (SPI), but such indicators are not widely used in the UK. More generally, such tools have not been well developed for hydrological (i.e. streamflow) drought. To fill these research gaps, this paper characterises meteorological and hydrological droughts, and the propagation from one to the other using the SPI and the related Standardised Streamflow Index (SSI), with the objective of improving understanding of the drought hazard in the UK. SPI and SSI time series were calculated for 121 near-natural catchments in the UK for accumulation periods of 1–24 months. From these time series, drought events were identified and for each event, the duration and severity was calculated. The relationship between meteorological and hydrological drought was examined by cross-correlating the one month SSI with various SPI accumulation periods. Finally, the influence of climate and catchment properties on the drought characteristics and propagation were investigated. Results showed that at short accumulation periods meteorological drought characteristics showed little spatial variability, whilst hydrological drought characteristics showed fewer but longer and more severe droughts in the south and east than in the north and west of the UK. Propagation characteristics showed a similar spatial pattern with catchments underlain by productive aquifers, mostly in the south and east, having longer SPI accumulation periods strongly correlated with the one-month SSI. For catchments in the north and west of the UK, which typically have little catchment storage, standard-period annual average rainfall was strongly correlated to drought and propagation characteristics. However, in the south and east, catchment properties describing storage, such as base flow index, percentage of highly productive fractured rock and typical soil wetness, were more influential on drought characteristics. This knowledge forms a basis for more informed application of standardised indicators in the UK in future, which could aid in the development of improved M&EW systems. Given the paucity of studies applying standardised indicators to hydrological droughts, and the diversity of catchment types encompassed here, the findings could prove valuable for enhancing the hydrological aspects of M&EW systems elsewhere in the world.
Static behaviour of induced seismicity
Authors: Mignan A.
Published: December 2015

Abstract. The standard paradigm to describe seismicity induced by fluid injection is to apply nonlinear diffusion dynamics in a poroelastic medium. I show that the spatiotemporal behaviour and rate evolution of induced seismicity can, instead, be expressed by geometric operations on a static stress field produced by volume change at depth. I obtain laws similar in form to the ones derived from poroelasticity while requiring a lower description length. Although fluid flow is known to occur in the ground, it is not pertinent to the behaviour of induced seismicity. The proposed model is equivalent to the static stress model for tectonic foreshocks generated by the Non-Critical Precursory Accelerating Seismicity Theory. This study hence verifies the explanatory power of this theory outside of its original scope.
Theoretical comparison of subgrid turbulence in the atmosphere and ocean
Authors: Kitsios V. , Frederiksen J. S. , Zidikheri M. J.
Published: December 2015

Abstract. Due to the massive disparity between the largest and smallest eddies in the atmosphere and ocean, it is not possible to simulate these flows by explicitly resolving all scales on a computational grid. Instead the large scales are explicitly resolved, and the interactions between the unresolved subgrid turbulence and large resolved scales are parameterised. If these interactions are not properly represented then an increase in resolution will not necessarily improve the accuracy of the large scales. This has been a significant and long standing problem since the earliest climate simulations. Historically subgrid models for the atmosphere and ocean have been developed in isolation, with the structure of each motivated by different physical phenomena. Here we solve the turbulence closure problem by determining the parameterisation coefficients (eddy viscosities) from the subgrid statistics of high resolution quasi-geostrophic atmospheric and oceanic simulations. These subgrid coefficients are characterised into a set of simple unifying scaling laws, for truncations made within the enstrophy cascading inertial range. The ocean additionally has an inverse energy cascading range, within which the subgrid model coefficients have alternative scaling properties. Simulations adopting these scaling laws are shown to reproduce the statistics of the reference benchmark simulations across resolved scales, with orders of magnitude improvement in computational efficiency. This reduction in both resolution dependence and computational effort will improve the efficiency and accuracy of geophysical research and operational activities that require data generated by general circulation models, including: weather, seasonal and climate prediction; transport studies; and understanding natural variability and extreme events.
Annual Greenland accumulation rates (2009–2012) from airborne Snow Radar
Authors: Koenig L. S. , Ivanoff A. , Alexander P. M. , MacGregor J. A. , Fettweis X. , Panzer B. , Paden J. D. , Forster R. R. , Das I. , McConnell J. , Tedesco M. , Leuschen C. , Gogineni P.
Published: December 2015

Abstract. Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet (GrIS) through increasing surface melt, emphasizing the need to closely monitor surface mass balance (SMB) in order to improve sea-level rise predictions. Here, we quantify accumulation rates, the largest component of GrIS SMB, at a higher spatial resolution than currently available, using Snow Radar stratigraphy. We use a semi-automated method to derive annual-net accumulation rates from airborne Snow Radar data collected by NASA's Operation IceBridge from 2009 to 2012. An initial comparison of the accumulation rates from the Snow Radar and the outputs of a regional climate model (MAR) shows that, in general, the radar-derived accumulation matches closely with MAR in the interior of the ice sheet but MAR estimates are high over the southeast GrIS. Comparing the radar-derived accumulation with contemporaneous ice cores reveals that the radar captures the annual and long-term mean. The radar-derived accumulation rates resolve large-scale patterns across the GrIS with uncertainties of up to 11 %, attributed mostly to uncertainty in the snow/firn density profile.
Lazzaro in guerra. Esperienze e trasfigurazione della trincea in Clemente Rebora
Authors: Cicala Roberto , Rossi Valerio
Published: December 2015

Lazzaro in guerra. Esperienze e trasfigurazione della trincea in Clemente Rebora
Curzio Malaparte: "La rivolta dei santi maledetti"
Authors: Martellini Luigi
Published: December 2015

Curzio Malaparte: "La rivolta dei santi maledetti"
Ungaretti e il sentimento della guerra
Authors: Verdino Stefano
Published: December 2015

Ungaretti e il sentimento della guerra
Aspetti problematici del Discorso Accademico: un’analisi dei riassunti delle tesi di laurea
Authors: Fiorentino Giuliana
Published: December 2015

Aspetti problematici del Discorso Accademico: un’analisi dei riassuntidelle tesi di laurea
"Io che mi racconto": il romanzo del divenire. "In contumacia" di Giacoma Limentani
Authors: Lucamante Stefania
Published: December 2015

"Io che mi racconto": il romanzo del divenire. "In contumacia" di Giacoma Limentani
Evaluation of Physical and Framework Condition of Administrative Buildings in Order to Crisis Management in 5th Sector Isfahan City
Authors: Taghvaei Masoud , Rahmani Neda , Taghvaei Mahtab
Published: December 2015

Natural disasters have always existed during the life of earth. There is no place safe against natural disasters and crises. Therefore, communities were always looking for solutions to reducing damages and losses of Supervene incidents. One of the most fundamental human actions to decreasing losses of crisis incidence is “crisis management”. As an important element, administrative units can play an important role during crisis in cities. These units can be used in management, organizing rescue affairs, storage, habitation and shelter of victims. In this research, physical and framework condition of administrative buildings in 5th sector of Isfahan city is evaluated. Heretofore, there is no study on evaluating physical and framework condition of administrative buildings in Isfahan city. This research is descriptive-analytic and survey and required information are gathered in five indicators using questionnaire through field studies. This information is evaluated and weighted using AHP method. The results indicated that among evaluated administrative centers, 15-code office with weight of 121% had the most vulnerability and 14-code office with weight of 0.21% had the lowest vulnerability.
What’s in Your File Folder? Part 2: Epistemology, Logic, and “The Objective”
Authors: Bissell Roger E.
Published: December 2015

The author discusses how Rand’s largely underdeveloped concept of the “dual-aspect objective,” first introduced in the 1960s, is vital for understanding how knowledge is grounded in reality. He defines it, then applies it to perception and introspection, and to concepts, propositions, and syllogisms. The author also defines content of awareness, carefully distinguishing it from both object and form of awareness, and applies those distinctions throughout. In addition, he discusses how truth is both dual-aspect and contextual, and he extends his discussion in Part 1 of Rand’s “unit-perspective,” showing how units, too, have a dual-aspect, even on the level of syllogisms.
Reply to Fred Seddon: What Does Ayn Rand Have to Do with Who Says That’s Art?
Authors: Kamhi Michelle Marder
Published: December 2015

This commentary is in response to Fred Seddon’s review of Who Says That’s Art? A Commonsense View of the Visual Arts in The Journal of Ayn Rand Studies (December 2014). In addition to answering objections raised in the review about such matters as whether “abstract art” and photography should qualify as “fine art,” it aims to show in what respects the book was influenced by Rand’s thought.