In DNA-based data storage, DNA codes with biochemical constraints and error correction are designed to protect data reliability. Single-stranded DNA sequences with secondary structure avoidance (SSA) help to avoid undesirable secondary structures which may cause chemical inactivity. Homopolymer run-length limit and GC-balanced limit also help to reduce the error probability of DNA sequences during synthesizing and sequencing. In this letter, based on a recent work [4], we construct DNA codes free of secondary structures of stem length ≥ m and have homopolymer run-length ≤ ℓ for odd m ≤ 11 and ℓ ≥ 3 with rate 1 + log 2 ρm − 3/(2 ℓ−1 + ℓ + 1), where ρm is in Table I. In particular, when m = 3, ℓ = 4, its rate tends to 1.3206 bits/nt, beating a previous work by Benerjee et al.. We also construct DNA codes with all of the above three constraints as well as single error correction. At last, codes with GC-locally balanced constraint are presented.
Guided scrambling is an example of multimode coding technique, which belongs to line code. This technique uses scrambling polynomials to form selection sets, by using proper selection criteria, the codeword with least contribution to DC (direct current) content will be chosen for transmitting. This paper designs this kind of GS (guided scrambling) line code which is suitable to be transmitted in long-distance UTP channel. According to the requirement of the real channel, this technique optimizes the design parameters, such as augmenting bits, scrambling polynomials, bit rate and selection criteria, to achieve the high bit rate of 64/67. The simulation experiment shows that this scheme is efficient in suppression of low frequency, and its PSD characteristics meet the requirement of transmission in long-distance UTP channel.
Aims Water resources and nutrient management significantly affect the in-situ remediation of cadmium (Cd)-contaminated soils. This study aimed to evaluate the mechanism of P application on Cd leaching risk under simulated flooding and drying-wet condition.Methods We conducted soil column leaching and incubations experiments to examine the mobility and release characteristics of Cd from contaminated rice soil -water microcosm.Results In soil column, amendments of phosphorous (P) significantly (p<0.01) decreased the mobilization of Cd in leachate. The Cd concentration in leachates showed significantly negative relationship with solution Eh, but positive relationship (P < 0.05) with leachate pH values and DOC, indicating that P addition may decrease Cd emitted from the contaminated soil. In soil incubation, released Cd from soil (Cd 4 mg kg-1) reached up to 192.3 and 210.6 μg L-1 under flooding (P 80 mg kg-1) and drying-wetting (P20 mg kg-1), respectively, and were much lower than that from the corresponding controls without P addition after 90d incubation. Furthermore, released Cd in almost 87.5% soil incubations exceeded the detection limit stipulated in Chinese Environmental Quality Standards for Surface and Ground-water (GB 3838-2002 and GBT14848-2017, 10 μg L -1 Grade V) and poses contamination risk to surface and ground-water.Conclusion This work highlights the key role in site-specific nutrient and irrigation management and showed that P addition with continuous flooding condition management provide a useful control for Cd- contamination soil and to prevent Cd further risk.
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