Study of femtosecond ablation on aluminum film with 3D two-temperature model and experimental verifications

In this paper, a 3D two-temperature model is introduced to investigate femtosecond ablation on aluminum film. 3D temperature evolutions for both electrons and lattice are obtained, which present us a vivid view of the energy transformation process during femtosecond ablation. Simulated 3D ablation craters irradiated by a single pulse with different energy are acquired, from which we can easily and precisely predict crater depth and radius before ablation takes place. In the experiment we measure the radii of the craters ablated by pulses with different energy and numbers delivered from a chirped pulse amplification Ti: sapphire system. The threshold fluence for both single and multi pulses are obtained. Comparisons are made between results of the experiment and relative simulated calculations show the reliability of our proposed calculation model.     

Turning on the Antimicrobial Activity of Gold Nanoclusters Against Multidrug-Resistant Bacteria**

In this work, we show that the addition of thiourea (TU) initiated broad-spectrum antimicrobial activity of otherwise inactive D-maltose-capped gold nanoclusters (AuNC-Mal). For example, AuNC-Mal/TU was effective against multidrug-resistant Pseudomonas aeruginosa with a minimum inhibitory concentration (MIC) of 1 μg mL⁻¹ (2.5 μM [Au]) while having 30–60 times lower in vitro cytotoxicity against mammalian cells. The reaction of AuNC-Mal and TU generated the antimicrobial species of [Au(TU)₂]⁺ and smaller AuNCs. TU increased the accumulation of Au in bacteria and helped maintain the oxidation state as Au^I (vs. Au^III). The modes of action included the inhibition of thioredoxin reductase, interference with the Cu^I regulation and depletion of ATP. Moreover, the antimicrobial activity did not change in the presence of colistin or carbonyl cyanide 3-chlorophenylhydrazone, suggesting that AuNC-Mal/TU was indifferent to the outer membrane barrier and to bacterial efflux pumps.     

87Sr solid-state NMR as a structurally sensitive tool for the investigation of materials: antiosteoporotic pharmaceuticals and bioactive glasses

Strontium is an element of fundamental importance in biomedical science. Indeed, it has been demonstrated that Sr(2+) ions can promote bone growth and inhibit bone resorption. Thus, the oral administration of Sr-containing medications has been used clinically to prevent osteoporosis, and Sr-containing biomaterials have been developed for implant and tissue engineering applications. The bioavailability of strontium metal cations in the body and their kinetics of release from materials will depend on their local environment. It is thus crucial to be able to characterize, in detail, strontium environments in disordered phases such as bioactive glasses, to understand their structure and rationalize their properties. In this paper, we demonstrate that (87)Sr NMR spectroscopy can serve as a valuable tool of investigation. First, the implementation of high-sensitivity (87)Sr solid-state NMR experiments is presented using (87)Sr-labeled strontium malonate (with DFS (double field sweep), QCPMG (quadrupolar Carr-Purcell-Meiboom-Gill), and WURST (wideband, uniform rate, and smooth truncation) excitation). Then, it is shown that GIPAW DFT (gauge including projector augmented wave density functional theory) calculations can accurately compute (87)Sr NMR parameters. Last and most importantly, (87)Sr NMR is used for the study of a (Ca,Sr)-silicate bioactive glass of limited Sr content (only ~9 wt %). The spectrum is interpreted using structural models of the glass, which are generated through molecular dynamics (MD) simulations and relaxed by DFT, before performing GIPAW calculations of (87)Sr NMR parameters. Finally, changes in the (87)Sr NMR spectrum after immersion of the glass in simulated body fluid (SBF) are reported and discussed.     

Electronic and vibrational spectra of a series of substituted carbazole derivatives

The FTIR and FTR spectra of halogen (Cl, Br, I) substituted carbazole and their N-acetic and propionic acids have been recorded. A number of lines have been assigned on the basis of previous studies on the parent compound and by comparisons with the characteristic vibrations of their constituent structural units as well as comparing the spectra from FTIR and FTR. Some substituent-sensitive bands and characteristic bands were found. The electronic absorption spectra of these compounds in acetonitrile were also measured and are briefly discussed.     

Toward Scalable Nanofluidic Osmotic Power Generation from Hypersaline Water Sources with a Metal–Organic Framework Membrane

Nanofluidic membranes have shown great promise in harvesting osmotic energy but its scalablity remains challenging since most studies only tested with a membrane area of ≈10⁻² mm² or smaller. We demonstrate that metal-organic-framework membranes with subnanometer pores can be used for scalable osmotic power generation from hypersaline water sources. Our membrane can be scaled up to a few mm², and the power density can be stabilized at 1.7 W m⁻². We reveal that the key is to improve the out-of-membrane conductance while keeping the membrane's charge selectivity, contradicting the previous conception that the ionic conductivity of the membrane plays the dominating role. We highlight that subnanometer pores are essential to ensure the charge selectivity in hypersaline water sources. Our results suggest the importance to engineer the interplay between the in-membrane and out-of-membrane ion transport properties for scalable osmotic power generation.