2,025,284 research outputs found

    Re-entrant ferroelectricity in liquid crystals

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    The ferroelectric (Sm C^*) -- antiferroelectric (Sm CA^*_A) -- reentrant ferroelectric (re Sm C^*) phase temperature sequence was observed for system with competing synclinic - anticlinic interactions. The basic properties of this system are as follows (1) the Sm C^* phase is metastable in temperature range of the Sm CA^*_A stability (2) the double inversions of the helix handedness at Sm C^* -- Sm CA^*_A and Sm CA^*_A% -- re-Sm C^* phase transitions were found (3) the threshold electric field that is necessary to induce synclinic ordering in the Sm CA^*_A phase decreases near both Sm CA^*_A -- Sm C^* and Sm CA^*_A -- re-Sm C^* phase boundaries, and it has maximum in the middle of the Sm CA^*_A stability region. All these properties are properly described by simple Landau model that accounts for nearest neighboring layer steric interactions and quadrupolar ordering only.Comment: 10 pages, 5 figures, submitted to PR

    Re-entrant ferroelectricity in liquid crystals

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    The ferroelectric (Sm C^*) -- antiferroelectric (Sm CA^*_A) -- reentrant ferroelectric (re Sm C^*) phase temperature sequence was observed for system with competing synclinic - anticlinic interactions. The basic properties of this system are as follows (1) the Sm C^* phase is metastable in temperature range of the Sm CA^*_A stability (2) the double inversions of the helix handedness at Sm C^* -- Sm CA^*_A and Sm CA^*_A% -- re-Sm C^* phase transitions were found (3) the threshold electric field that is necessary to induce synclinic ordering in the Sm CA^*_A phase decreases near both Sm CA^*_A -- Sm C^* and Sm CA^*_A -- re-Sm C^* phase boundaries, and it has maximum in the middle of the Sm CA^*_A stability region. All these properties are properly described by simple Landau model that accounts for nearest neighboring layer steric interactions and quadrupolar ordering only.Comment: 10 pages, 5 figures, submitted to PR

    Multi-temporal evaluation of soil moisture and land surface temperature dynamics using in situ and satellite observations

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    Soil moisture (SM) is an important component of the Earth’s surface water balance and by extension the energy balance, regulating the land surface temperature (LST) and evapotranspiration (ET). Nowadays, there are two missions dedicated to monitoring the Earth’s surface SM using L-band radiometers: ESA’s Soil Moisture and Ocean Salinity (SMOS) and NASA’s Soil Moisture Active Passive (SMAP). LST is remotely sensed using thermal infrared (TIR) sensors on-board satellites, such as NASA’s Terra/Aqua MODIS or ESA & EUMETSAT’s MSG SEVIRI. This study provides an assessment of SM and LST dynamics at daily and seasonal scales, using 4 years (2011–2014) of in situ and satellite observations over the central part of the river Duero basin in Spain. Specifically, the agreement of instantaneous SM with a variety of LST-derived parameters is analyzed to better understand the fundamental link of the SM–LST relationship through ET and thermal inertia. Ground-based SM and LST measurements from the REMEDHUS network are compared to SMOS SM and MODIS LST spaceborne observations. ET is obtained from the HidroMORE regional hydrological model. At the daily scale, a strong anticorrelation is observed between in situ SM and maximum LST (R ˜ -0.6 to -0.8), and between SMOS SM and MODIS LST Terra/Aqua day (R ˜ - 0.7). At the seasonal scale, results show a stronger anticorrelation in autumn, spring and summer (in situ R ˜ -0.5 to -0.7; satellite R ˜ -0.4 to -0.7) indicating SM–LST coupling, than in winter (in situ R ˜ +0.3; satellite R ˜ -0.3) indicating SM–LST decoupling. These different behaviors evidence changes from water-limited to energy-limited moisture flux across seasons, which are confirmed by the observed ET evolution. In water-limited periods, SM is extracted from the soil through ET until critical SM is reached. A method to estimate the soil critical SM is proposed. For REMEDHUS, the critical SM is estimated to be ~0.12 m3/m3 , stable over the study period and consistent between in situ and satellite observations. A better understanding of the SM–LST link could not only help improving the representation of LST in current hydrological and climate prediction models, but also refining SM retrieval or microwave-optical disaggregation algorithms, related to ET and vegetation status.Peer ReviewedPostprint (published version

    Activation cross-sections of proton induced reactions on nat^{nat}Sm up to 65 MeV

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    Activation cross sections for proton induced reactions on Sm are presented for the first time for nat^{nat}Sm(p,xn)154,152m2,152m1,152g,150m,150g,149,148,147,146,145^{154,152m2,152m1,152g,150m,150g,149,148,147,146,145}Eu, nat^{nat}Sm(p,x)153,145^{153,145}Sm, nat^{nat}Sm(p,x)151,150,149,148g,148m,146,144,143^{151,150,149,148g,148m,146,144,143}Pm and nat^{nat}Sm(p,x)141^{141}Nd up to 65 MeV. The cross sections were measured via activation method by using a stacked-foil irradiation technique and high resolution gamma ray spectroscopy. The results were compared with results of the nuclear reaction codes ALICE, EMPIRE and TALYS (results taken from TENDL libraries). Integral yields of the activation products were calculated from the excitation functions.Comment: arXiv admin note: text overlap with arXiv:1411.716

    The Impact of Cultural Familiarity on Students’ Social Media Usage in Higher Education

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    Using social media (SM) in Higher education (HE) becomes unavoidable in the new teaching and learning pedagogy. The current generation of students creates their groups on SM for collaboration. However, SM can be a primary source of learning distraction due to its nature, which does not support structured learning. Hence, derived from the literature, this study proposes three learning customised system features, to be implemented on SM when used in Higher Education HE. Nevertheless, some psychological factors appear to have a stronger impact on students’ adoption of SM in learning than the proposed features. A Quantitative survey was conducted at a university in Uzbekistan to collect 52 undergraduate students’ perception of proposed SM learning customised features in Moodle. These features aim to provide localised, personalised, and privacy control self-management environment for collaboration in Moodle. These features could be significant in predicting students’ engagement with SM in HE. The data analysis showed a majority of positive feedback towards the proposed learning customised SM. However, the surveyed students’ engagement with these features was observed as minimal. The course leader initiated a semi-structured interview to investigate the reason. Although the students confirmed their acceptance of the learning customised features, their preferences to alternate SM, which is Telegram overridden their usage of the proposed learning customized SM, which is Twitter. The students avoided the Moodle integrated Twitter (which provided highly accepted features) and chose to use the Telegram as an external collaboration platform driven by their familiarity and social preferences with the Telegram since it is the popular SM in Uzbekistan. This study is part of an ongoing PhD research which involves deeper frame of learners’ cognitive usage of the learning management system. However, this paper exclusively discusses the cultural familiarity impact of student’s adoption of SM in HE

    Aspects of Domain-Wall Standard Model

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    We have recently proposed a setup of the "Domain-Wall Standard Model" in a non-compact 5-dimensional space-time, where all the Standard Model (SM) fields are localized in certain domains of the 5th dimension. While the SM is realized as a 4-dimensional effective theory at low energies, the model involves Kaluza-Klein (KK) modes of the SM particles. In this paper we introduce two simple solvable examples which lead to domain-wall configurations for the SM particles and their KK-modes. Based on the examples, we address a variety of phenomenologies of the Domain-Wall SM, such as the KK-mode gauge boson phenomenology at the Large Hadron Collider (LHC), the effect of the KK-mode SM fermions on Higgs boson phenomenology, and the KK-mode fermion search at the LHC with its decay into a corresponding SM fermion and a Nambu-Goldstone boson associated with a spontaneous breaking of the translational invariance in the 5th dimension. We also propose a simple unified picture of localizing all the SM fields.Comment: 22 pages, 3 figures. arXiv admin note: text overlap with arXiv:1712.0932
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