Silver clusters consisting of ∼10 atoms are readily bound by and encapsulated within DNA strands to yield strong absorption and emission. The coordination environments, however, are poorly understood, so cluster adducts can only be empirically tuned. This work describes the C4AC4TC3G strand that templates a particular cluster adduct. Its sequence has three types of nucleobases with distinct rolestracts of cytosines that collectively coordinate the cluster, thymine acting as a junction in the overall strand, and the adenine/guanine pair that exclusively forms the cluster. In relation to the native oligonucleotide, the DNA–silver cluster complex diffuses faster and is more compact, thus suggesting that the strands fold because of the cluster. The Ag10 6+ adduct emits with λex/λem = 490/540 nm, a 19% quantum yield, and a biexponential 1.1/2.1 ns lifetime. The electronic environment for the cluster is controlled by the heteroatoms in the adenine and guanine. Most significantly, the N7 and the N2 in the guanine change the fluorescence quantum yield by 60-fold and shift the fluorescence lifetime by ∼3.8 ns. Thus, our studies discern distinct spectroscopic and structural roles for the nucleobase ligands in C4AC4TC3G, and these findings may help develop new DNA templates for other silver cluster adducts.

Possibility of preconditioning of wires in wire array Z-pinch loads by an auxiliary low-level current pulse was investigated in experiments with two aluminum or two polyimide-coated tungsten wires. It was found that the application of a 1 kA, 10 ns current pulse could convert all the length of the Al wires (1 cm long, 15 μm diameter) and ∼70% of length of the W wires (1 cm long, 15 μm diameter, 2 μm polyimide coating) into a gaseous state via ohmic heating. The expansion and merging of the wires, positioned at separations of 1–3 mm, were investigated with two-wavelength (532 nm and 1064 nm) laser interferometry. The gasified wire expanded freely in a vacuum and its density distribution at different times could be well described using an analytic model for the expansion of the gas into vacuum. Under an energy deposition around its atomization enthalpy of the wire material, the aluminum vapor column had an expansion velocity of 5–7 km/s, larger than the value of ∼4 km/s from tungsten wires. The dynamic atomic polarizabilities of tungsten for 532 nm and 1064 nm were also estimated.

Suppressing of the core-corona structures shows a strong potential as a new breakthrough in the X-ray power production of the wire array Z-pinches. In this letter, the demonstration of suppressing the core-corona structures and its ablation using a novel double pulse current generator "Qin-1" facility is presented. The "Qin-1" facility coupled a ~10 kA 20 ns prepulse generator to a ~ 1 MA 170 ns main current generator. Driven by the prepulse current, the two aluminum wire array were

The dynamics of wire array Z pinches are greatly affected by the initial state of the wires, which can be preconditioned by a prepulse current. Recent advances in experimental research on preconditioned wire array Z pinches at Xi’an Jiaotong University are presented in this paper. Single-wire explosion experiments were carried out to check the state of the preconditioning and to obtain the current parameters needed for wire gasification. Double-wire explosion experiments were conducted to investigate the temporal evolution of the density distribution of the two gasified wires. Based on the results of these experiments, a double-pulse Z-pinch facility, Qin-1, in which a 10 kA prepulse current was coupled with the 0.8 MA main current was designed and constructed. Wire arrays of different wire materials, including silver and tungsten, can be preconditioned by the prepulse current to a gaseous state. Implosion of the two preconditioned aluminum wires exhibited no ablation and little trailing mass.

The density distribution and the energy deposition in dark and light transverse layers from stratification structures were measured and analyzed from electrical exploding wire experiments in vacuum. It is demonstrated that the differences in the areal density of the dark layer and light layer regions were about 2 × 1017/cm2 at 296 ns after voltage collapsed. This difference corresponded to an energy deposition difference of ∼2 eV/atom between the dark and light layers, which likely arises from a ±10% resistivity perturbation during the explosion, as suggested by combining a gas column expansion model and a thermodynamic model.