12,955 research outputs found
Recent progress on weight distributions of cyclic codes over finite fields
Cyclic codes are an interesting type of linear codes and have wide applications in communication and storage systems due to their efficient encoding and decoding algorithms. In coding theory it is often desirable to know the weight distribution of a cyclic code to estimate the error correcting capability and error probability. In this paper, we present the recent progress on the weight distributions of cyclic codes over finite fields, which had been determined by exponential sums. The cyclic codes with few weights which are very useful are discussed and their existence conditions are listed. Furthermore, we discuss the more general case of constacyclic codes and give some equivalences to characterize their weight distributions
Coherent laser control of the current through molecular junctions
The electron tunneling through a molecular junction modeled by a single site
weakly coupled to two leads is studied in the presence of a time-dependent
external field using a master equation approach. In the case of small bias
voltages and high carrier frequencies of the external field, we observe the
phenomenon of coherent destruction of tunneling, i.e. the current through the
molecular junction vanishes completely for certain parameters of the external
field. In previous studies the tunneling within isolated and open multi-site
systems was suppressed; it is shown here that the tunneling between a single
site and electronic reservoirs, i.e. the leads, can be suppressed as well. For
larger bias voltages the current does not vanish any more since further
tunneling channels participate in the electron conduction and we also observe
photon-assisted tunneling which leads to steps in the current-voltage
characteristics. The described phenomena are demonstrated not only for
monochromatic fields but also for laser pulses and therefore could be used for
ultrafast optical switching of the current through molecular junctions.Comment: 6 pages and 4 figure
Epitranscriptomics for Biomedical Discovery
Epitranscriptomics is a newly burgeoning field pertaining to the complete delineation and elucidation of chemical modifications of nucleotides found within all classes of RNA that do not involve a change in the ribonucleotide sequence. More than 140 diverse and distinct nucleotide modifications have been identified in RNA, dwarfing the number of nucleotide modifications found in DNA. The majority of epitranscriptomic modifications have been identified in ribosomal RNA (rRNA), transfer RNA (tRNA), and small nuclear RNA (snRNA). However, in total, the knowledge of the occurrence, and specifically the function, of RNA modifications remains scarce. Recently, the rapid advancement of next‐generation sequencing and mass spectrometry technologies have allowed for the identification and functional characterization of nucleotide modifications in both protein‐coding and non‐coding RNA on a global, transcriptome scale. In this chapter, we will introduce the concepts of nucleotide modification, summarize transcriptome‐wide RNA modification mapping techniques, highlight recent studies exploring the functions of RNA modifications and their association to disease, and finally offer insight into the future progression of epitranscriptomics
Phase diagram of a Bose-Fermi mixture in a one-dimensional optical lattice in terms of fidelity and entanglement
We study the ground-state phase diagram of a Bose-Fermi mixture loaded in a
one-dimensional optical lattice by computing the ground-state fidelity and
quantum entanglement. We find that the fidelity is able to signal quantum phase
transitions between the Luttinger liquid phase, the density-wave phase, and the
phase separation state of the system; and the concurrence can be used to signal
the transition between the density-wave phase and the Ising phase.Comment: 4 pages 3 figure
Synthesis and photocatalytic properties of a new paddle-wheel Cu(II) complex: An integrated experimental and theoretical investigation
A new paddle-wheel Cu(II) complex having formula [Cu(L)2(DMF)] (1) (HL = 2-fluorobenzoic acid) has been synthesized and characterized using FTIR and single crystal X-ray diffraction. The single crystal X-ray diffraction study indicates that the carboxylic acid ligand adopt bridging bidentate modes to coordinate Cu(II) centers thereby forming a binuclear copper(II)carboxylate type structure. The complex has been utilized as photocatalyst to photodegrade model aromatic dyes viz. methyl violet (MV) and rhodamine B (Rh B) in UV light. The photocatalytic results indicated that1 offered moderate photocatalytic activity and offers good stability after performing photocatalysis. The plausible mechanism through which 1 exerted photcatalytic property had been proposed by using density of states (DOS) and partial DOS calculations. KEY WORDS: Photocatalysis, Aromatic dyes, 2-Fluorobenzoic acid, Calculation Bull. Chem. Soc. Ethiop. 2019, 33(2), 285-292.DOI: https://dx.doi.org/10.4314/bcse.v33i2.
Attribution of growing season evapotranspiration variability considering snowmelt and vegetation changes in the arid alpine basins
Previous studies have successfully applied variance decomposition
frameworks based on the Budyko equations to determine the relative
contribution of variability in precipitation, potential evapotranspiration
(E0), and total water storage changes (ΔS) to evapotranspiration
variance (σET2) on different timescales; however, the effects
of snowmelt (Qm) and vegetation (M) changes have not been incorporated
into this framework in snow-dependent basins. Taking the arid alpine basins
in the Qilian Mountains in northwest China as the study area, we extended
the Budyko framework to decompose the growing season σET2 into
the temporal variance and covariance of rainfall (R), E0, ΔS,Qm,
and M. The results indicate that the incorporation of Qm could improve
the performance of the Budyko framework on a monthly scale; σET2 was primarily controlled by the R variance with a mean
contribution of 63 %, followed by the coupled R and M (24.3 %) and then
the coupled R and E0 (14.1 %). The effects of M variance or Qm
variance cannot be ignored because they contribute 4.3 % and 1.8 % of
σET2, respectively. By contrast, the interaction of some
coupled factors adversely affected σET2, and the
out-of-phase seasonality between R and Qm had the largest effect
(−7.6 %). Our methodology and these findings are helpful for
quantitatively assessing and understanding hydrological responses to climate
and vegetation changes in snow-dependent regions on a finer timescale.</p
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