The effects of land use and management on belowground carbon and nutrient interactions

Carbon (C) turnover has been increasingly shown to be linked to the mineralization of other nutrients due to the co-limitation of these elements on microbial processes. Regional factors such as climate and parent materials, land use and management practices are important controls of soil nutrient and availabilities that potentially result in mineral soils with varied carbon-to-nutrient ratios. The main objectives of this thesis were to study the interactions between C and nutrients in the mineral soils using soil incubation and leaching techniques under controlled environments. To study the intensity of soil priming under different land uses and management, substrate-induced soil incubations were performed using 13C-labelled glucose solution. Overall, land use and management types were observed to affect the rates of CO2 production relative to nutrient release. As hypothesized, this was mainly due to the differences in soil C-to-nutrient ratios between these land use types, where higher ratios were observed in forests than grasslands. In contrast to expectations, CO2-to-N- and CO2-to-S-leaching ratios were significantly higher in grasslands than forests in all regions. This was mostly caused by significantly higher CO2 and significantly lower N and S leaching in grasslands than forests which might be due to higher microbial biomass at the grassland sites. When normalized to microbial biomass C, soil C:N positively correlated to C mineralization DOC leaching, showing that low soil N contents increase C losses per microbial biomass as indicated by the nutrient mining theory. Overall, the findings from this thesis confirmed the importance of nutrient stoichiometry on SOM mineralization, and highlight the important interactions between C, N, P and S mineralization under differently managed soils in forests and grasslands. Land use were shown to be important driver for SOM mineralization and soil priming due to differences in microbial biomass and activities

Perception Driven Texture Generation

This paper investigates a novel task of generating texture images from perceptual descriptions. Previous work on texture generation focused on either synthesis from examples or generation from procedural models. Generating textures from perceptual attributes have not been well studied yet. Meanwhile, perceptual attributes, such as directionality, regularity and roughness are important factors for human observers to describe a texture. In this paper, we propose a joint deep network model that combines adversarial training and perceptual feature regression for texture generation, while only random noise and user-defined perceptual attributes are required as input. In this model, a preliminary trained convolutional neural network is essentially integrated with the adversarial framework, which can drive the generated textures to possess given perceptual attributes. An important aspect of the proposed model is that, if we change one of the input perceptual features, the corresponding appearance of the generated textures will also be changed. We design several experiments to validate the effectiveness of the proposed method. The results show that the proposed method can produce high quality texture images with desired perceptual properties.Comment: 7 pages, 4 figures, icme201

Low-bias Negative Differential Resistance effect in armchair graphene nanoribbon junctions

Graphene nanoribbons with armchair edges (AGNRs) have bandgaps that can be flexibly tuned via the ribbon width. A junction made of a narrower AGNR sandwiched between two wider AGNR leads was recently reported to possess two perfect transmission channels close to the Fermi level. Here, we report that by using a bias voltage to drive these transmission channels into the gap of the wider AGNR lead, we can obtain a negative differential resistance (NDR) effect. Owing to the intrinsic properties of the AGNR junctions, the on-set bias reaches as low as ~ 0.2 V and the valley current almost vanishes. We further show that such NDR effect is robust against details of the atomic structure of the junction, substrate and whether the junction is made by etching or by hydrogenation.Comment: The following article has been submitted to Applied Physics Letters (http://scitation.aip.org/content/aip/journal/apl). Copyright (2014) Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported Licens

Social media use, body image, and body weight status: comparison between university students with and without disordered eating in Universiti Putra Malaysia

Background: Disordered eating, body dissatisfaction, and social media use are increasingly common among university students. This cross-sectional study aimed to compare social media use, body image, and body weight status between disordered eating (DE) and non-disordered eating (NDE) university students. Materials and Methods: There were two phases of data collection. In Phase I, a total of 505 university students (22.6% males and 77.4% females) with a mean age of 21.26 ± 1.41 years from three randomly selected faculties in UPM were screened for disordered eating using the Eating Attitude Test (EAT-26). Sociodemographic background and anthropometric measurements including weight, height, waist circumference, and body fat percentage of respondents were measured. In Phase II, those respondents with DE were matched with those without DE by sex, age, and ethnicity. They answered an online survey on body image and social media use. Result: Out of 505 university students in Phase I, 21.8% were engaged in DE with no sex difference observed (χ2=0.738, p=0.390). In Phase II, 106 DE respondents were matched with 106 NDE respondents. No significant differences were found in body image, social media use (duration, volume, frequency, engagement, selfie sharing, photo investment, and photo manipulation) and body weight status between DE and NDE groups. However, DE respondents reported to have a significantly higher frequency of selfie-taking as compared to NDE respondents (t=-2.338, p=0.020). Conclusion: High prevalence of disordered eating was observed in this study. The contribution of social media use to disordered eating needs to be further studied