Fabrication of UV-Curable Polysiloxane Coating with Tunable Refractive Index Based on Controllable Hydrolysis.

In order to improve laser transmission efficiency at 1053 nm and 527 nm, a potassium deuterium phosphate (DKDP) crystal (a key component of high-power laser systems) needs a bi-layer antireflection coating system on its incident surface. UV-curable polysiloxane coatings with a refractive index varying from 1.500 to 1.485 were prepared through the polycondensation of a methacryloxy propyl trimethoxylsilane (MPS) monomer with a controllable degree of hydrolysis. Additionally, the influence rule of the coating structure on the refractive index was intensively studied, and the primary factors that dominate the hydrolysis process were discussed. Further refractive index adjustment was achieved using only a small amount of dopant based on the polysiloxane coating with refractive index of 1.485, allowing for high antireflection of the bi-layer coating system at desired wavelengths to be achieved. In addition, high laser damage resistance and remarkable mechanical properties of the coating were simultaneously realized through the incorporation of a minor quantity of dopants, which benefited from the successful modulation of the intrinsic refractive index of the polysiloxane coating.

Formation mechanism of DKDP surface in single point diamond fly-cutting process and the resulting degradation of laser-induced damage performance.

Laser damage performance of DKDP (KD2xH2(1-x)PO4) crystal is largely determined by the surface microstructures generated in the manufacturing process, more specifically, single point diamond fly-cutting process. However, because of the lack of knowledge about the formation mechanism and damage performance of the microstructures, laser induced damage of DKDP crystal remains a key issue limiting the output energy of the high power laser systems. In this paper, the influence of fly-cutting parameters on the generation of DKDP surface and the underlying material deformation mechanism have been investigated. Except for cracks, two kinds of new microstructures, namely micro grains and ripples, have been found on the processed DKDP surfaces. GIXRD, nano-indentation and nano-scratch test results prove that the micro grains are generated by the slip motion of the crystal, while the simulation results show that the cracks are induced by the tensile stress formed behind the cutting edge. Moreover, the formation of micro grains can facilitate the plastic chip flow through the mechanism of grain boundary sliding, which will further lead to a periodic fluctuation of the chip separation point and the formation of micro ripples. Finally, laser damage test results demonstrate that cracks will degrade the damage performance of DKDP surface significantly, while the formation of micro grains and micro ripples has little impact. The results of this study can deepen the understanding of the formation mechanism of the DKDP surface during the cutting process and provide guidance to improve the laser-induced damage performance of the crystal.

Damage analysis and mechanism study of sol-gel coating over KDP crystal under multi-pulse of laser irradiation at low flux.

The purpose of this study is to analyze the damage of antireflective (AR) coating over potassium dihydrogen phosphate (KDP) crystal subjected to multi-pulse laser irradiation at low flux under vacuum. Fresh silica AR was characterized as a reference; Atomic Force Microscope (AFM), Scanning Electron Microscopy (SEM), profilometer, and Scanning Near-Field Optical Microscope Photo-induced Force Microscope (SNOM-PiFM) were employed to analyze the characteristics of coatings. The experimental results indicated that the damage of AR coating over the KDP crystal was mainly caused by partial exfoliation, which exposed silica particles beneath the surface. It was found that the accumulated tensile stress led to coating damage with the increase of laser pulse. The initial coating damage was observed to extend and interconnect to form large-area exfoliation. Splitting mechanism of SiO-Si TO3 was observed at vibration mode peaks of 1064 cm-1 and 1096 cm-1showing progressing irradiation damage. Based on this study, it would be helpful to suppress the damage probability of AR coating over KDP crystal applied in high-power laser systems. Moreover, the applicability of SNOM-PiFM method to study the Infrared Radiation (IR) spectra of ultra-thin coatings with transparent substrates was proposed.

Interaction Mechanism of Thermal and Mechanical Field in KDP Fly-Cutting Process.

As an important nonlinear optical material, potassium dihydrogen phosphate (KDP) crystal is used in high-power laser beams as the core element of inertial confinement fusion. It is the most general method of single point diamond fly-cutting (SPDF) to produce high precision and crack-free KDP surfaces. Nevertheless, the cutting mechanism of such material remains unclear, and therefore needs further analysis. Firstly, the stress field, cutting force and cutting temperature under different working conditions are calculated by a KDP crystal cutting simulation model. Then, the rules and the cause of change and interaction mechanisms of force and temperature are analyzed by comparing the measurement experiments with simulations. Furthermore, the causes of chip formation and micro-cracks on the machined surface are analyzed based on thermo-mechanical coupling and chip morphology. The conclusion can be deduced: Although the temperature has not reached the phase transition temperature during the finishing process, under high cutting speeds and large unformed chip thickness, such as semi-finishing and roughing, the temperature can reach up to 180 °C or higher, and KDP crystals are very likely to phase transition-chip morphology also verifies this phenomenon.

Epidermal Growth Factor Protects Against High Glucose-Induced Podocyte Injury Possibly via Modulation of Autophagy and PI3K/AKT/mTOR Signaling Pathway Through DNA Methylation.

AIM: Diabetic nephropathy (DN) is a serious health problem worldwide. Epidermal growth factor (EGF) has suggested as a potential biomarker for the progression of chronic kidney disease. In this study, we examined the effects of EGF on the high glucose (HG)-induced podocyte injury and explored the underlying molecular mechanisms. METHODS: The cell proliferation, toxicity, and cell apoptosis of podocytes were determined by CCK-8 assay, lactate dehydrogenase release assay, and flow cytometry, respectively, and protein levels in the podocytes were determined by Western blot assay. Mechanistically, DNA methylation analysis, bioinformatic analysis, methylation­specific PCR and quantitative real-time PCR were used to analyze functional pathways in differentially methylated genes and the expression of the key methylated genes in the podocytes after different interventions. RESULTS: EGF treatment significantly increased the protein expression level of LC3 and decreased the protein level of P62 in HG-stimulated podocytes, which was attenuated by autophagy inhibitor, 3-methyladenine. EGF increased the cell proliferation and the protein expression levels of nephrin and synaptopodin, but reduced cell toxicity and cell apoptosis and protein expression level of cleaved caspase-3, which was partially antagonized by 3-methyladenine. DNA methylation expression profiles revealed the differential hypermethylation sites and hypomethylation sites among podocytes treated with normal glucose, HG and HG+EGF. GO enrichment analysis showed that DNA methylation was significantly enriched in negative regulation of phosphorylation, cell-cell junction and GTPase binding. KEGG pathway analysis showed that these genes were mainly enriched in PI3K-Akt, Hippo and autophagy pathways. Further validation studies revealed that six hub genes (ITGB1, GRB2, FN1, ITGB3, FZD10 and FGFR1) may be associated with the protective effects of EGF on the HG-induced podocyte injury. CONCLUSION: In summary, our results demonstrated that EGF exerted protective effects on HG-induced podocytes injury via enhancing cell proliferation and inhibiting cell apoptosis. Further mechanistic studies implied that EGF-mediated protective effects in HG-stimulated podocytes may be associated with modulation of autophagy and PI3K/AKT/mTOR signaling pathway.

Effect of laser pulse duration and fluence on DKDP crystal laser conditioning.

The impact of laser conditioning (LC) fluence and pulse duration on nanosecond (ns) laser damage performance of deuterated potassium dihydrogen phosphate (DKDP) crystal is studied. The result shows that higher LC fluence leads to a better damage resistance. In general, the sub-nanosecond LC effect is better than the nanosecond LC. However, in the range of 0.3 ns to 0.8 ns, the pulse duration has no obvious impact on the LC effect. An ultra-fast process characterization technology is employed to demonstrate that the cleaning effect of the protuberance defects on the surface is one of sub-ns LC mechanism. Eventually, a couple of optimized LC parameters that doubled the maximum damage threshold of DKDP crystal is proposed.

Influence of the arrangement of vacuum chuck holes on the transmittance wavefront of large-aperture KDP in single-point diamond turning.

Serious edge effects of potassium dihydrogen phosphate (${{\rm KH}_2}{{\rm PO}_4}$KH2PO4, KDP) manufactured using single-point diamond turning (SPDT) often result in disqualification of the transmittance wavefront for high-power laser systems. In this paper, based on the theoretical analysis of sucker hole configuration and the pressure distribution law under the vacuum chuck condition of crystal elements, the influence of sucker hole configuration on the transmittance wavefront root-mean-square gradient (GRMS) is verified through fly-cutting experiments. By adopting the newly designed vacuum chuck, the vacuum-chucking quality is effectively improved, and the edge effect is accordingly suppressed in the SPDT. Moreover, the accuracy of the transmittance wavefront GRMS has an improvement of about 25% under the same processing parameters.

Template-Free Fabrication of Refractive Index Tunable Polysiloxane Coating Using Homogeneous Embedding Strategy: Application in High-Power Laser System.

A refractive index (RI) tunable polysiloxane coating was fabricated based on the cross-linked network structure embedded with mesoporous silica nanoparticles (MSNs), in which the MSNs were utilized to modulate the RI as well as to support the interior structure of the polysiloxane coating. The Si-O-Si inorganic backbone structure in combination with characteristics from the photopolymerization of active bonds produced the main cross-linked network structure, and controllable embedding of MSNs constructed the network-sphere structure. This approach eliminated the high-temperature post-treatment that was needed to remove the template, which ensures the safe application for temperature-sensitive laser crystal substrates and avoids coating structure collapse. In addition, degradation of the resulting coating can be minimized due to the similar chemical formation between MSN and polysiloxane coating. Hereby, a polysiloxane coating with expected spectral and laser damage-resistant properties can be obtained. This will facilitate the fabrication and application of a laser component with both high-transmission and high-flux capability for a high-power laser system.

Simulation of the nanosecond-pulse laser damage of KDP surface by the smoothed particle hydrodynamics method.

We present a simulation method to reproduce the damage crater formation and particle ejection phenomena observed in the laser-induced surface damage process of potassium dihydrogen phosphate (KDP) crystals. Based on the smoothed particle hydrodynamics method, which is commonly used for solving shock and blast problems, equivalent explosion simulation models of the laser-induced damage process have been established. Moreover, laser damage experiments combined with time-resolved techniques are performed on KDP surfaces to investigate the impact of laser fluences on the shockwave propagation and the particle ejection speed. We find that the simulation models can predict the laser-induced damage behaviors of the KDP crystal, which verifies the validity of the proposed method.

Investigation of the laser-induced surface damage of KDP crystal by explosion simulation.

Under nanosecond pulse irradiation, laser-induced damage of Potassium Dihydrogen Phosphate (KDP) crystal is a multi-physical coupling process which mainly includes energy absorption by precursor defects, temperature and pressure rise in the absorption center, and subsequent micro-explosion event. Till now, related research work mainly focuses on modeling the energy absorption stage and determining the temperature or pressure in the absorption center, but knowledge about the explosion stage is rather limited. In this paper, laser-induced damage of KDP crystal has been investigated through explosion simulation. According to the laser damage test results and morphologies of the damage craters, typical precursor defects inducing KDP surface damage have been determined. Based on the knowledge, equivalent explosion simulation models of the laser damage process have been established to reproduce damage crater formation and shockwave propagation. Finally, laser damage experiments, combined with time resolved techniques, have been utilized to investigate the variation of damage crater size and shockwave speed with laser fluences. Simulation results given by single core explosion models agree well with the experimental results at fluences lower than 60 J/cm2, while a multicore explosion model is needed to reliably simulate damage crater formation at higher fluences.

Fabrication of Refractive Index Tunable Coating with Moisture-Resistant Function for High-Power Laser Systems Based on Homogeneous Embedding of Surface-Modified Nanoparticles.

Moisture-resistant silicone coatings were prepared on the surface of potassium dihydrogen phosphate (KDP) crystal by means of spin-coating, in which hydrophobic-modified SiO2 nanoparticles were embedded in a certain proportion. The refractive index of such coating can be tuned arbitrarily in the range of 1.21⁻1.44, which endows the KDP optical component with excellent transmission capability as well as the moisture proof effect. A dual-layer anti-reflective coating system was obtained by covering this silicone coating with a porous SiO2 coating which is specially treated to enhance the moisture resistance. Transmittance of such a dual-layer coating system could reach 99.60% and 99.62% at 1064 nm and 532 nm, respectively, by precisely matching the refractive index of both layers. Furthermore, the long-term stability of this coating system has been verified at high humidity ambient of 80% RH for 27 weeks.

Influences of surface defects on the laser-induced damage performances of KDP crystal.

When potassium dihydrogen phosphate (KDP) crystals are exposed to high-energy laser irradiation, the pre-existing surface defects may act as damage precursors and will reduce the lifespan of the crystal components. Although it has been found that different kinds of surface defects exhibit distinct damage characteristics, the influence of surface defects on the laser-induced damage performance of KDP crystal is not yet clear. In this paper, KDP surface defects have been characterized by multiple measuring methods and classified into five categories according to their structure features. Laser-induced damage tests were then carried out to investigate the laser-induced damage thresholds of different kinds of KDP surface defects as well as the evolution of the morphology of damage sites. The results of the experiment indicate that the damage thresholds of cracks, fracture pits, and surface protuberances are between 6 and 11 J/cm2 (355 nm, 3 ns, similarly hereinafter), which are much lower than the thresholds of plastic scratches, discontinuous scratches, and a defect-free KDP surface. In addition, it has been found that fluorescence enhancement is just a necessary condition for reduction of damage thresholds. Finally, reasons for the formation of the most threatening KDP surface defects have been analyzed and corresponding suppression measures have been proposed for increasing the surface damage thresholds of the crystal components.

Mutagenesis of lysines 156 and 159 in human immunodeficiency virus type 1 integrase (IN) reveals differential interactions between these residues and different IN inhibitors.

Human immunodeficiency virus (HIV) type I integrase (IN) active site, and viral DNA-binding residues K156 and K159 are predicted to interact both with strand transfer-selective IN inhibitors (STI), e.g. L-731,988, Elvitegravir (EVG), and the FDA-approved IN inhibitor, Raltegravir (RGV), and strand transfer non-selective inhibitors, e.g. dicaffeoyltartaric acids (DCTAs), e.g. L-chicoric acid (L-CA). To test posited roles for these two lysine residues in inhibitor action we assayed the potency of L-CA and several STI against a panel of K156 and K159 mutants. Mutagenesis of K156 conferred resistance to L-CA and mutagenesis of either K156 or K159 conferred resistance to STI indicating that the cationic charge at these two viral DNA-binding residues is important for inhibitor potency. IN K156N, a reported polymorphism associated with resistance to RGV, conferred resistance to L-CA and STI as well. To investigate the apparent preference L-CA exhibits for interactions with K156, we assayed the potency of several hybrid inhibitors containing combinations of DCTA and STI pharmacophores against recombinant IN K156A or K159A. Although K156A conferred resistance to diketo acid-branched bis-catechol hybrid inhibitors, neither K156A nor K159A conferred resistance to their monocatechol counterparts, suggesting that bis-catechol moieties direct DCTAs toward K156. In contrast, STI were more promiscuous in their interaction with K156 and K159. Taken together, the results of this study indicate that DCTAs interact with IN in a manner different than that of STI and suggest that DCTAs are an attractive candidate chemotype for development into drugs potent against STI-resistant IN.

trans-Chlorido(phenanthren-9-yl)bis-(triphenyl-phosphane)nickel(II).

The title compound, [Ni(C(14)H(9))Cl(C(18)H(15)P)(2)], was synthesized from the reaction between 9-chloro-phenanthrene, NiCl(2)·6H(2)O and triphenyl-phosphane in ethanol. The bond angles around the Ni(II) atom indicate that it exists in a slightly distorted square-planar geometry.

(4,4',6,6'-Tetra-tert-butyl-2,2'-{[2-(di-methyl-amino)-ethyl]-nitrilo-bis-(methyl-ene)}diphenolato)dioxidomolyb-denum(VI) chloro-form monosolvate.

In the title compound, [Mo(C(34)H(54)N(2)O(2))O(2)]·CHCl(3), the molybdenum(VI) ion exhibits a cis-dioxide distorted octa-hedral geometry. Two anionic phenolate O-atom donors and two neutral N-atom donors of the ligand are trans and cis, respectively. The Mo=O bond lengths and the O=Mo=O bond angle are typical for six-coordinated dioxomolyb-denum(VI) complexes. The Mo-N bond lengths are longer than 2.30 Å, as expected for a trans O=Mo-N structure.

Design, synthesis, and biological evaluation of novel hybrid dicaffeoyltartaric/diketo acid and tetrazole-substituted L-chicoric acid analogue inhibitors of human immunodeficiency virus type 1 integrase.

Fourteen analogues of the anti-HIV-1 integrase (IN) inhibitor L-chicoric acid (L-CA) were prepared. Their IC(50) values for 3'-end processing and strand transfer against recombinant HIV-1 IN were determined in vitro, and their cell toxicities and EC(50) against HIV-1 were measured in cells (ex vivo). Compounds 1-6 are catechol/ß-diketoacid hybrids, the majority of which exhibit submicromolar potency against 3'-end processing and strand transfer, though only with modest antiviral activities. Compounds 7-10 are L-CA/p-fluorobenzylpyrroloyl hybrids, several of which were more potent against strand transfer than 3'-end processing, a phenomenon previously attributed to the ß-diketo acid pharmacophore. Compounds 11-14 are tetrazole bioisosteres of L-CA and its analogues, whose in vitro potencies were comparable to L-CA but with enhanced antiviral potency. The trihydroxyphenyl analogue 14 was 30-fold more potent than L-CA at relatively nontoxic concentrations. These data indicate that L-CA analogues are attractive candidates for development into clinically relevant inhibitors of HIV-1 IN.

L-chicoric acid inhibits human immunodeficiency virus type 1 integration in vivo and is a noncompetitive but reversible inhibitor of HIV-1 integrase in vitro.

The human immunodeficiency virus (HIV) integrase (IN) must covalently join the viral cDNA into a host chromosome for productive HIV infection. l-Chicoric acid (l-CA) enters cells poorly but is a potent inhibitor of IN in vitro. Using quantitative real-time polymerase chain reaction (PCR), l-CA inhibits integration at concentrations from 500 nM to 10 microM but also inhibits entry at concentrations above 1 microM. Using recombinant HIV IN, steady-state kinetic analyses with l-CA were consistent with a noncompetitive or irreversible mechanism of inhibition. IN, in the presence or absence of l-CA, was successively washed. Inhibition of IN diminished, demonstrating that l-CA was reversibly bound to the protein. These data demonstrate that l-CA is a noncompetitive but reversible inhibitor of IN in vitro and of HIV integration in vivo. Thus, l-CA likely interacts with amino acids other than those which bind substrate.