290 research outputs found
Unusual chemical bond and spectrum of beryllium dimer in ground state
This review outlines the main results which show the dual nature of the
chemical bond in diatomic beryllium molecule in the ground
state. It has been shown that the beryllium atoms are covalently bound at
low-lying vibrational energy levels ({\nu}=0-4), while at higher ones
({\nu}=5-11) they are bound by van der Waals forces near the right turning
points. High precision ab initio quantum calculations of Be resulted in the
development of the modified expanded Morse oscillator potential function which
contains all twelve vibrational energy levels [A.V. Mitin, Chem. Phys. Lett.
682, 30 (2017)]. The dual nature of chemical bond in Be is evidenced as a
sharp corner on the attractive branch of the ground state potential curve.
Moreover, it has been found that the Douglas-Kroll-Hess relativistic
corrections also show a sharp corner when presented in dependence on the
internuclear separation. The difference in energy between the extrapolated and
calculated multi-reference configuration interaction energies in dependence on
the internuclear separation also exhibits singular point in the same region.
The other problems of ab initio quantum calculations of the beryllium dimer are
also discussed. Calculated spectrum of vibrational-rotational bound states and
new metastable states of the beryllium dimer in the ground state important for
laser spectroscopy are presented. The vibration problem was solved for the
modified expanded Morse oscillator potential function and for the potential
function obtained with Slater-type orbitals [M. Lesiuk et al, Chem. Theory
Comput. 15, 2470 (2019)]. The theoretical upper and lower estimates of the
spectrum of vibrational-rotational bound states and the spectrum of
rotational-vibrational metastable states with complex-valued energy eigenvalues
and the scattering length in the beryllium dimer are presented
The Gattini cameras for optical sky brightness measurements at Dome C, Antarctica
The Gattini cameras are two site testing instruments for
the measurement of optical sky brightness, large area cloud cover and auroral detection of the night sky above the high altitude Dome C site in Antarctica. The cameras have been operating since installation in January 2006 and are currently at the end of the first Antarctic winter season. The cameras are transit in nature and are virtually identical both adopting Apogee Alta CCD detectors. By taking frequent images of the night sky we obtain long term cloud cover statistics, measure the sky background intensity as a function of solar and lunar altitude and
phase and directly measure the spatial extent of bright aurora if present and when they occur. The full data set will return in December 2006 however a limited amount of data has been transferred via the Iridium network enabling preliminary data reduction and system evaluation.
An update of the project is presented together with preliminary results from data taken since commencement of the winter season
VLSP SHARED TASK: SENTIMENT ANALYSIS
Sentiment analysis is a natural language processing (NLP) task of identifying orextracting the sentiment content of a text unit. This task has become an active research topic since the early 2000s. During the two last editions of the VLSP workshop series, the shared task on Sentiment Analysis (SA) for Vietnamese has been organized in order to provide an objective evaluation measurement about the performance (quality) of sentiment analysis tools, and encouragethe development of Vietnamese sentiment analysis systems, as well as to provide benchmark datasets for this task. The rst campaign in 2016 only focused on the sentiment polarity classication, with a dataset containing reviews of electronic products. The second campaign in 2018 addressed the problem of Aspect Based Sentiment Analysis (ABSA) for Vietnamese, by providing two datasets containing reviews in restaurant and hotel domains. These data are accessible for research purpose via the VLSP website vlsp.org.vn/resources. This paper describes the built datasets as well as the evaluation results of the systems participating to these campaigns
Required flows for aquatic ecosystems in Ma River, Vietnam
Ecological flow requirements for the Ma River in dry season were assessed in three reaches of Ma â Buoi, Ma â Len and Ma â Chu. 5 indictor fish species was chosen based on biodiversity survey and roles of those species in aquatic ecosystem as well as local communities. Biological and hydrological data (dry season of 2016- 2017) and 35 year recorded hydrological data were collected and analyzed as input data for a physical habitat model River HYdraulic and HABitat SImulation Model â RHYHABSIM. Model results shown that the optimal flows of the reaches were very much higher compare with the minimum annual low flow - MALF. In this study, MALF7day were applied to calculate the recommended minimum flows of the three reaches. The recommended required minimum flows for Ma â Buoi, Ma â Len and Ma â Chu reaches were 51 m3/s, 49 m3/s and 61 m3/s, respectively. It must be stressed that this study only assessed whether or not there is enough habitat available for the river to sustain a healthy ecosystem
Indications for Absorbable Steroid-Eluting Sinus Implants: Viewpoint via the Delphi Method
Absorbable steroid-eluting sinus implants provide targeted corticosteroid release over a sustained period and are designed to prevent both undesirable adhesion formation and sinus ostia restenosis. Here, we highlight the key evidence of these implants to date and query a group of experts via a Delphi process on the indications and optimal timing for intraoperative or in-office placement of these implants. Six of a total of 12 statements reached consensus and were accepted. Overall, experts largely agree that intraoperative or in-office use of steroid-eluting stents could be considered for patients: (1) who are diabetic or intolerant of oral steroids, (2) undergoing extended frontal sinus surgery, and (3) with recurrent stenosis. Given the lack of expert consensus on other key statements, clinicians should carefully consider these treatment options on a case-by-case basis after shared decision-making
Progress of the LUNEX5 Project
http://accelconf.web.cern.ch/AccelConf/FEL2013/papers/wepso05.pdfInternational audienceLUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) aims at investigating the production of short, intense, and coherent pulses in the soft X-ray region. A 400 MeV superconducting linear accelerator and a laser wakefield accelerator (LWFA), will feed a single Free Electron Laser line with High order Harmonic in Gas and Echo Enable Harmonic Generation seeding. After the Conceptual Design Report (CDR), R&D has been launched on specific magnetic elements (cryo-ready 3 m long in-vacuum undulator, a variable strong permanent magnet quadrupoles), on diagnostics (Smith-Purcell, electro-optics). In recent transport studies of a LWFA based on more realistic beam parameters (1 % energy spread, 1 ÎŒm beam size and 1 mrad divergence) than the ones assumed in the CDR, a longitudinal and transverse manipulation enables to provide theoretical amplification. A test experiment is under preparation. It is noted in this context that among the French scientific community's interest in experiments at operating FELs is increasing
EZH2 Cooperates with BRD4-NUT to Drive NUT Carcinoma Growth by Silencing Key Tumor Suppressor Genes
NUT carcinoma (NC) is an aggressive carcinoma driven by the BRD4-NUT fusion oncoprotein, which activates chromatin to promote expression of pro-growth genes. BET bromodomain inhibitors (BETi) are a promising treatment for NC that can impede BRD4-NUTâs ability to activate genes, but the efficacy of BETi as monotherapy are limited. Here, we demonstrated that EZH2, which silences genes through establishment of repressive chromatin, is a dependency in NC. Inhibition of EZH2 with the clinical compound tazemetostat (taz) potently blocked growth of NC cells. Epigenetic and transcriptomic analysis revealed that taz reversed the EZH2-specific H3K27me3 silencing mark and restored expression of multiple tumor suppressor genes while having no effect on key oncogenic BRD4-NUT-regulated genes. Indeed, H3K27me3 and H3K27ac domains were found to be mutually exclusive in NC cells. CDKN2A was identified as the only gene among all taz-derepressed genes to confer resistance to taz in a CRISPR-Cas9 screen. Combined inhibition of EZH2 and BET synergized to downregulate cell proliferation genes resulting in more pronounced growth arrest and differentiation than either inhibitor alone. In pre-clinical models, combined taz and BETi synergistically blocked tumor growth and prolonged survival of NC-xenografted mice, with complete remission without relapse in one cohort. Identification of EZH2 as a dependency in NC substantiates the reliance of NC tumor cells on epigenetic dysregulation of functionally opposite, yet highly complementary, chromatin regulatory pathways to maintain NC growth
Surface-enhanced Raman spectroscopy study of 4-ATP on gold nanoparticles for basal cell carcinoma fingerprint detection
The surface-enhanced Raman signals of 4-aminothiophenol (4-ATP) attached to the surface of colloidal gold nanoparticles with size distribution of 2 to 5 nm were used as a labeling agent to detect basal cell carcinoma (BCC) of the skin. The enhanced Raman band at 1075 cm-1 corresponding to the C-S stretching vibration in 4-ATP was observed during attachment to the surface of the gold nanoparticles. The frequency and intensity of this band did not change when the colloids were conjugated with BerEP4 antibody, which speciïŹcally binds to BCC. We show the feasibility of imaging BCC by surface-enhanced Raman spectroscopy, scanning the 1075 cm-1 band to detect the distribution of 4ATP-coated gold nanoparticles attached to skin tissue ex vivo
Predicting range shifts of African apes under global change scenarios
Aim:
Modelling African great ape distribution has until now focused on current or past conditions, while future scenarios remain scarcely explored. Using an ensemble forecasting approach, we predicted changes in taxon-specific distribution under future scenarios of climate, land use and human populations for (1) areas outside protected areas (PAs) only (assuming complete management effectiveness of PAs), (2) the entire study region and (3) interspecies range overlap.
Location:
Tropical Africa.
Methods:
We compiled occurrence data (n = 5,203) on African apes from the IUCN A.P.E.S. database and extracted relevant climate-, habitat- and human-related predictors representing current and future (2050) conditions to predict taxon-specific range change under a best- and a worst-case scenario, using ensemble forecasting.
Results
The predictive performance of the models varied across taxa. Synergistic interactions between predictors are shaping African ape distribution, particularly human-related variables. On average across taxa, a range decline of 50% is expected outside PAs under the best scenario if no dispersal occurs (61% in worst scenario). Otherwise, an 85% range reduction is predicted to occur across study regions (94% worst). However, range gains are predicted outside PAs if dispersal occurs (52% best, 21% worst), with a slight increase in gains expected across study regions (66% best, 24% worst). Moreover, more than half of range losses and gains are predicted to occur outside PAs where interspecific ranges overlap.
Main Conclusions:
Massive range decline is expected by 2050, but range gain is uncertain as African apes will not be able to occupy these new areas immediately due to their limited dispersal capacity, migration lag and ecological constraints. Given that most future range changes are predicted outside PAs, Africa's current PA network is likely to be insufficient for preserving suitable habitats and maintaining connected ape populations. Thus, conservation planners urgently need to integrate land use planning and climate change mitigation measures at all decision-making levels both in range countries and abroad
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