A fully-adjustable picosecond resolution arbitrary timing generator based on multi-stage time interpolation.

We report a fully adjustable arbitrary timing generator (ATG) that is based on a multistage time interpolation method. A 3 ps timing adjustment resolution is achieved using a three-stage time interpolation module. The output signal amplitude of the ATG is adjustable, as a current controlled output module is designed to adjust the output voltage of driver circuits. A field programmable gate array is used to realize the main logic of the ATG. A 3.2 ps short term jitter, a pulse width dynamic range from 6.25 ns to 5 s, and an output voltage range between -1 and +5 V are obtained. The arbitrary timing generator can be used in the applications that require high precision timing control and adjustable output capacity.

In silico post-SELEX screening and experimental characterizations for acquisition of high affinity DNA aptamers against carcinoembryonic antigen.

DNA aptamers against carcinoembryonic antigen (CEA) have been identified through the systematic evolution of ligands by exponential enrichment (SELEX) technique, but their affinity needs to be improved. In this study, an in silico approach was firstly used to screen the mutation sequences of a reported DNA aptamer (the parent aptamer, denoted as P) against CEA. The affinities of several high-score DNA mutants were determined by the biolayer interferometry technique. Finally, the newly obtained aptamers were verified in an aptasensor application. For the in silico approach, Mfold and RNA Composer were combined to generate the 3D RNA structures of the DNA mutants. The RNA structures were then modified to 3D DNA structures with the Write program. The docking model and binding ability of the 3D DNA structures with CEA were simulated and predicted with the ZDOCK program. Two mutation sequences (P-ATG and GAC-P) exhibited significantly higher ZDOCK scores than P. The dissociation constant of P-ATG and GAC-P to CEA was determined to be 4.62 and 3.93 nM respectively, obviously superior to that of P (6.95 nM). The detection limit of the P-ATG and GAC-P based aptasensors was 1.5 and 1.2 ng mL-1, respectively, markedly better than that based on P (3.4 ng mL-1). The consistency between the in silico and the experimental results indicates that the developed in silico post-SELEX screening approach is feasible for improving DNA aptamers. The P-ATG and GAC-P aptamers found in this study could be used for future CEA aptasensor design and fabrication, promisingly applicable for highly sensitive CEA detection and early cancer diagnosis.

A pico-second resolution arbitrary timing generator based on time folding and time interpolating.

We report a pico-second resolution arbitrary timing generator which is implemented with a field-programmable-gate-array. The arbitrary timing/pattern generator is based on a time folding method which is combined with a delay chain for fine time interpolating. The time folding method can not only break the limitation of sequence time resolution contributed by the minimum chain cell delay but also improve the chain linearity. The arbitrary timing generator which is based on the time folding technique is integrated in a printed-circuit board, and a 5 ps time resolution with enhanced output linearity is obtained. The dynamic range of output pulses from the arbitrary timing generator is from 5 ns to 10 s. In this paper, we describe the principle, the circuit design, and the characterizations of the arbitrary timing generator. We also discuss the improvement of performance in timing generation using the time folding method. The high-performance arbitrary timing generator has a bright future to be used in the applications that require high-resolution timing sequence generation.

[A long distance colonization event of Chinese endemic bat Myotis davidii].

In order to reveal the population phylogenetic relationships and colonization history of Chinese endemic bat species Myotis davidii, a total of 126 samples from 14 populations in nationwide were collected in 2001-2009, taking the mitochondrial control region as the molecular marker. Based on the TCS network diagram of the mitochondrial DNA control region sequences, the 14 geographical populations were divided into three geographical regions, i.e., mid-east plain region, southwest plateau region, and south hills region. In the 53 haplotypes, the No. 14 in Zhejiang Province, No. 47 in Guizhou Province, and No. 50 in Guangdong Province were the ancestors in the three regions, respectively. Based on Geodis analysis, mismatch distribution analysis, and neutrality test, the population expansion events were found in mid-eastern plain region (76.12 and 79.17 ka BP) and southwest plateau (69.12 ka BP). In 61.24 ka BP, a long distance migration event originated from the southwest plateau region to the mid-east plain region occurred. The evidences of molecular biology, bionics, anatomy, and aerodynamics all revealed the long-distance migration capability of M. davidii.

Experimental demonstration of a nondestructive controlled-NOT quantum gate for two independent photon qubits.

Universal logic gates for two quantum bits (qubits) form an essential ingredient of quantum information processing. However, photons, one of the best candidates for qubits, suffer from a lack of strong nonlinear coupling, which is required for quantum logic operations. Here we show how this drawback can be overcome by reporting a proof-of-principle experimental demonstration of a nondestructive controlled-NOT (CNOT) gate for two independent photons using only linear optical elements in conjunction with single-photon sources and conditional dynamics. Moreover, we exploit the CNOT gate to discriminate all four Bell states in a teleportation experiment.