Broadband chaos of an interband cascade laser with a 6-GHz bandwidth.

Near-infrared semiconductor lasers subject to optical feedback usually produce chaos with a broad bandwidth of a few GHz. However, the reported mid-infrared interband cascade lasers (ICLs) only show chaos with a limited bandwidth below 1 GHz. Here we show that an ICL with optical feedback is able to generate broadband chaos as well. The mid-infrared chaos exhibits a remarkable bandwidth of about 6 GHz, which is comparable to that of the near-infrared counterpart. In addition, the spectral coverage in the electrical domain reaches as high as 17.7 GHz. It is found that the chaos bandwidth generally broadens with increasing feedback ratio and/or increasing pump current of the laser, while it is insensitive to the feedback length.

Effect of airborne-particle abrasion with a novel spherical abrasive on the zirconia surface.

STATEMENT OF PROBLEM: A novel zirconia-alumina composite (ZAC) particle has yet to be studied for airborne-particle abrasion in a bonding protocol for the zirconia surface. PURPOSE: The purpose of this in vitro study was to evaluate the shear bond force of resin cement to yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) when using spherical ZAC particles to conduct airborne-particle abrasion and modify the topography of Y-TZP. MATERIAL AND METHODS: Spherical 30- to 70-µm ZAC particles were fabricated by using a hybrid gel technique. A total of 160 Ø6.6×4.0-mm zirconia disks were fabricated from 4 commercially available zirconia blanks, e.max ZirCAD zirconia (EM), NexxZr T zirconia (NE), Lava Plus High Translucency zirconia (LP), and Imagine High Translucency Zirconia (IM), by using computer-aided manufacturing technology. As-sintered specimens without further surface treatment were used as controls (ZR0). Surface treatment groups included sharp-edged alumina airborne-particle abrasion (ABC), 50 µm, 0.2 MPa; airborne-particle abrasion with ZAC particle at 0.2 MPa (2ZA); and airborne-particle abrasion with spherical ZAC particle at 0.4 MPa (4ZA). All surface treatment groups were airborne-particle abraded at the specified pressures for 10 seconds at a standardized distance of 10 mm. The surface roughness (Ra) and area roughness (Sa) of specimens from each group were measured. Following the application of an adhesive (Scotchbond Universal), Ø6.6×4.0-mm resin cement (RelyX Ultimate) buttons were fabricated for shear bond testing by using a universal testing machine at a 5-mm/min crosshead speed (n=10). The data were analyzed by using a 2-way ANOVA, Tukey HSD test, and regression analysis (α=0.05). Scanning electron microscopy (SEM) was performed to observe changes of the zirconia surface and the failure modes of each group before and after shear bond testing. RESULTS: The mean ±standard deviation shear bond force values ranged from 272.6 ±41.4 N to 686.7 ±152.8 N. Statistically significant higher force values than those of the controls (P<.05) were obtained by using airborne-particle abrasion. No significant differences were found among any of the airborne-particle abrasion treatment groups (P>.05). The mean of Ra values ranged from 0.27 µm to 0.74 µm, and the mean of Sa values, from 0.48 µm to 1.48 µm. SEM observation revealed that the zirconia surface was made jagged by abrasion with sharp-edged alumina particles. The spherical ZAC particles create microcraters on the zirconia surface. Fractographic observation disclosed that failures were adhesive-cohesive failure modes with residual resin cement attached on the zirconia surface. CONCLUSIONS: The surface treatment of zirconia with sharp-edged alumina or the spherical ZAC abrasives improved the bonding force between the zirconia and resin cement. No statistically significant differences in shear bond force values were found between airborne-particle abrasion surface treatment groups.

Iron overload adversely effects bone marrow haematogenesis via SIRT-SOD2-mROS in a process ameliorated by curcumin.

BACKGROUND: Iron overload, which is common in patients with haematological disorders, is known to have a suppressive effect on haematogenesis. However, the mechanism for this effect is still unclear. The antioxidant curcumin has been reported to protect against iron overload-induced bone marrow damage through an as-yet-unknown mechanism. METHODS: We established iron overload cell and mouse models. Mitochondrial reactive oxygen species (mROS) levels, autophagy levels and the SIRT3/SOD2 pathway were examined in the models and in the bone marrow of patients with iron overload. RESULTS: Iron overload was shown to depress haematogenesis and induce mitochondrion-derived superoxide anion-dependent autophagic cell death. Iron loading decreased SIRT3 protein expression, promoted an increase in SOD2, and led to the elevation of mROS. Overexpression of SIRT3 reversed these effects. Curcumin treatment ameliorated peripheral blood cells generation, enhanced SIRT3 activity, decreased SOD2 acetylation, inhibited mROS production, and suppressed iron loading-induced autophagy. CONCLUSIONS: Our results suggest that curcumin exerts a protective effect on bone marrow by reducing mROS-stimulated autophagic cell death in a manner dependent on the SIRT3/SOD2 pathway.

Identification of new IDH2R140Q inhibitors by discriminatory analysis-based molecular docking and biological evaluation.

Isocitrate dehydrogenase 2 (IDH2) is a key enzyme in the regulation of cell metabolism. Its mutated type can lead to the accumulation of 2-hydroxyglutarate, which is often related to malignancies such as acute myeloid leukemia. Therefore, it is necessary to find new inhibitors targeting mutant IDH2. Discriminatory analysis-based molecular docking was employed to screen the ChemDiv compound library, which resulted in the identification of three new IDH2R140Q inhibitors with moderate-to-good IC50 values. Among them, compounds 1 and 3 displayed good selectivity against other mutant or wild-type IDH proteins. The most potent compound 1, bearing the [1,2,4]triazolo[1,5-a]pyrimidin scaffold, was subjected to dynamic simulations to provide more information on the binding mode with IDH2R140Q , providing structural clues to further optimize compound 1 as a new mutant IDH2 inhibitor.

An ssDNA aptamer specific for detection and purification of hexahistidine-tagged proteins.

Aptamers are small-sized RNA or ssDNA ligands with a unique structure, which have high specificity and affinity to their cognate targets. Thus, in addition to the extensive values in various bio-medical fields, aptamers can also be alternatively used as affinity ligands in the bioprocess, such as for protein purification. In the present study, a hexahistidine specific aptamer named AptHis-C, was developed through the SELEX methodology, which has high affinity to hexahistidine, and its dissociation constant was as low as 20.8 nM. The structural prediction revealed that AptHis-C contains two connected stem-loop conformations. AptHis-C can only specifically recognize recombinant proteins with the hexahistidine-tag in simple or complex situations, and not to those with other tags. When immobilized on magnetic beads, AptHis-C can be used as a tool for hexahistidine-tagged recombinant protein purification. Its effectiveness is as good as traditional Ni-based beads. Besides, due to the intrinsic characteristics of nucleic acids, such as high thermal/chemical stability, immobilized aptamer-magnetic beads can be reused many times without an obvious decrease of purification effectiveness. This aptamer may represent a novel method for the detection and purification of hexahistidine-tagged recombinant proteins.

Esthetic appearances of anatomic contour zirconia crowns made by additive wet deposition and subtractive dry milling: A self-controlled clinical trial.

STATEMENT OF PROBLEM: Anatomic contour zirconia crowns are widely used in clinical dental practice because of their mechanical reliability and improved appearance. However, few studies have performed clinical evaluations of the esthetics of these crowns in terms of color and translucency gradient. PURPOSE: The purpose of this clinical trial was to compare the esthetic effect and color-matching behaviors of anatomic contour zirconia crowns manufactured with 3-dimensional (3D) gel deposition and dry milling methods. MATERIAL AND METHODS: Twenty-seven premolar teeth of 27 participants received 2 identical anatomic contour zirconia crowns fabricated by additive 3D gel deposition or dry milling. Color differences (ΔE) between the crown and natural control teeth were measured by a dental shade-matching device. Subjective color matching was rated by professionals using an extended visual rating scale for appearance match (EVRSAM) and by participants using a visual analog scale (VAS). Data were analyzed by using repeated measures ANOVA, the Bonferroni test, paired Student t test, Pearson chi-square test, and Wilcoxon test (α=.05). RESULTS: Significant differences were found in ΔE between zirconia crown and core types (P<.05); however, there was no significant interaction between these factors (P>.05). The average ΔE of crowns made by wet deposition and dry milling were 2.45 ±1.60 and 4.55 ±1.54 (P<.05). The mean crown ΔE was significantly higher if a gold cast post-and-core was placed rather than a prefabricated fiber post and composite core (P<.05). Consistent with these findings, subjective color matching was significantly higher in the wet deposition group than in the dry milling group as rated by EVRSAM and VAS (P<.05). CONCLUSIONS: Anatomic contour zirconia crowns fabricated by additive wet deposition were better matched to adjacent teeth and had excellent esthetics in terms of color and translucency gradient.

Mean platelet volume predicts prognosis in patients with diffuse large B-cell lymphoma.

To determine the prognostic value of baseline mean platelet volume (MPV) in diffuse large B-cell lymphoma (DLBCL) patients. We retrospectively analyzed 161 DLBCL patients who received R-CHOP chemotherapy. The associations between MPV and clinicopathological factors were assessed. A low MPV (MPV ≤ 9.1 fl, cut-off was calculated by receiver operating characteristics) was not associated with any other clinicopathological factors. Patients with MPV ≤ 9.1 fl experienced a shorter progression-free survival (PFS) (2-year PFS rate, 60.6% vs 84.0%, P = 0.003) and overall survival (OS) (2-year OS rate, 70.4% vs 87.9%, P = 0.030), compared with those with MPV > 9.1 fl. The multivariate analysis demonstrated that MPV ≤ 9.1 fl was an independent prognostic factor of OS (Hazard Ratio [HR] = 0.588, P = 0.045) and PFS (HR = 0.456, P = 0.010). Therefore, we demonstrated that low baseline MPV is an independent prognostic marker of poor outcome in patients with DLBCL.

Down-regulation of CD19 expression inhibits proliferation, adhesion, migration and invasion and promotes apoptosis and the efficacy of chemotherapeutic agents and imatinib in SUP-B15 cells.

The survival rate of childhood acute lymphoblastic leukemia (ALL) has increased while that of Philadelphia-positive (Ph+) ALL remains low. CD19 is a B-cell specific molecule related to the survival and proliferation of normal B cells. However, there is little information available on the effects of CD19 on the biological behavior of Ph+ ALL cells. In this study, we explored a lentiviral vector-mediated short hairpin RNA (shRNA) expression vector to stably reduce CD19 expression in Ph+ ALL cell line SUP-B15 cells and investigated the effects of CD19 downregulation on cell proliferation, apoptosis, drug sensitivity, cell adhesion, cell migration and cell invasion in vitro. CD19 mRNA and protein expression levels were inhibited significantly by CD19 shRNA. Down-regulation of CD19 could inhibit cell proliferation, adhesion, migration and invasion, and increase cell apoptosis and the efficacy of chemotherapeutic agents and imatinib in SUP-B15 cells. Moreover, we found that down-regulation of CD19 expression inhibits cell proliferation and induces apoptosis in SUP-B15 cells in a p53-dependent manner. Taken together, our results suggest that lentiviral vector-mediated RNA interference of CD19 gene may be a promising strategy in the treatment of Ph+ ALL.

Rapid sintering of silicon nitride foams decorated with one-dimensional nanostructures by intense thermal radiation.

Silicon nitride foams were prepared by direct foaming and subsequent rapid sintering at 1600 °C. The intense thermal radiation generated under the pressureless spark plasma sintering condition facilitated necking of Si3N4 grains. The prepared foams possessed a porosity of ∼80 vol% and a compressive strength of ∼10 MPa, which required only ∼30 min for the entire sintering processes. Rapid growth of one-dimensional SiC nanowires from the cell walls was also observed. Thermodynamic calculations indicated that the vapor-liquid-solid model is applicable to the formation of SiC nanowires under vacuum.

Inorganic polymers: morphogenic inorganic biopolymers for rapid prototyping chain.

In recent years, considerable progress has been achieved towards the development of customized scaffold materials, in particular for bone tissue engineering and repair, by the introduction of rapid prototyping or solid freeform fabrication techniques. These new fabrication techniques allow to overcome many problems associated with conventional bone implants, such as inadequate external morphology and internal architecture, porosity and interconnectivity, and low reproducibility. However, the applicability of these new techniques is still hampered by the fact that high processing temperature or a postsintering is often required to increase the mechanical stability of the generated scaffold, as well as a post-processing, i.e., surface modification/functionalization to enhance the biocompatibility of the scaffold or to bind some bioactive component. A solution might be provided by the introduction of novel inorganic biopolymers, biosilica and polyphosphate, which resist harsh conditions applied in the RP chain and are morphogenetically active and do not need supplementation by growth factors/cytokines to stimulate the growth and the differentiation of bone-forming cells.

Effect of resin cement selection on the microtensile bond strength of adhesively veneered 3Y-TZP.

OBJECTIVE: The aim of this study was to investigate the effect of resin cement selection on the microtensile bond strength (µTBS) of adhesively veneered 3Y-TZP. MATERIALS AND METHODS: 3Y-TZP discs were fabricated from commercial powders and treated by sandblasting and zirconia primer. Porcelain discs were sectioned from a feldspathic block and conditioned with 5% HF and silane agent. Pre-treated surfaces of zirconia and porcelain discs were bonded together using one of the three following resin cements: Multilink N (MN), Panavia F (PA) or RelyX Unicem (RU), respectively. After light-curing the joined discs were cut into microbars where 15 microbars per group were randomly chosen for µTBS test until failure occurred (24 h storage in water in advance, crosshead speed of 0.5 mm/min). The data were analysed by one-way ANOVA and Tukey's test (p < 0.05). Fractured zirconia surfaces were examined using both a stereomicroscope and scanning electron microscope to identify the failure mode. RESULTS: Significant differences in the µTBS values among three groups were found (p < 0.001) and the descending order was PA, RU and MN. No zirconia or feldspathic failure occurred, but the zirconia/cement interfaces suffered from fracture for all samples. Cement cohesive failure and/or feldspathic/cement interfacial failure sometimes were involved. Failures were mainly adhesive for RU, while they were mixed for MN and PA. CONCLUSION: When using the adhesive veneering method, Panavia F offers better bond strength than Multilink N or RelyX Unicem, which is probably due to the content of the 10-methacryloyloxydecyl dihydrogenphosphate (10-MDP) monomer.

Can the use of pulsed direct current induce oscillation in the applied pressure during spark plasma sintering?

The spark plasma sintering (SPS) process is known for its rapid densification of metals and ceramics. The mechanism behind this rapid densification has been discussed during the last few decades and is yet uncertain. During our SPS experiments we noticed oscillations in the applied pressure, related to a change in electric current. In this study, we investigated the effect of pulsed electrical current on the applied mechanical pressure and related changes in temperature. We eliminated the effect of sample shrinkage in the SPS setup and used a transparent quartz die allowing direct observation of the sample. We found that the use of pulsed direct electric current in our apparatus induces pressure oscillations with the amplitude depending on the current density. While sintering Ti samples we observed temperature oscillations resulting from pressure oscillations, which we attribute to magnetic forces generated within the SPS apparatus. The described current-pressure-temperature relations might increase understanding of the SPS process.

Surface Effect of Nano-Roughened Yttria-Doped Zirconia on Salivary Protein Adhesion.

Biocompatibility of yttria (3 mol%) stabilized zirconia ceramics, 3Y-TZP, was affected to a large degree as a result of protein adsorption from human saliva that in turn depends on materials surface properties. Variable nano-roughness levels in 3Y-TZP discs were characterized and tested for specificity and selectivity with respect to size and uptake for human salivary protein.

Influence of Powder Bed Temperature on the Microstructure and Mechanical Properties of Ti-6Al-4V Alloy Fabricated via Laser Powder Bed Fusion.

Laser powder bed fusion (LPBF) is being increasingly used in the fabrication of complex-shaped structure parts with high precision. It is easy to form martensitic microstructure in Ti-6Al-4V alloy during manufacturing. Pre-heating the powder bed can enhance the thermal field produced by cyclic laser heating during LPBF, which can tailor the microstructure and further improve the mechanical properties. In the present study, all the Ti-6Al-4V alloy samples manufactured by LPBF at different powder bed temperatures exhibit a near-full densification state, with the densification ratio of above 99.4%. When the powder bed temperature is lower than 400 °C, the specimens are composed of a single α' martensite. As the temperature elevates to higher than 400 °C, the α and ß phase precipitate at the α' martensite boundaries by the diffusion and redistribution of V element. In addition, the α/α' lath coarsening is presented with the increasing powder bed temperature. The specimens manufactured at the temperature lower than 400 °C exhibit high strength but bad ductility. Moreover, the ultimate tensile strength and yield strength reduce slightly, whereas the ductility is improved dramatically with the increasing temperature, when it is higher than 400 °C.

Microstructural Characterization and Mechanical Properties of L-PBF Processed 316 L at Cryogenic Temperature.

Laser powder bed fusion (L-PBF) has attracted great interest in the aerospace and medical sectors because it can produce complex and lightweight parts with high accuracy. Austenitic stainless steel alloy 316 L is widely used in many applications due to its good mechanical properties and high corrosion resistance over a wide temperature range. In this study, L-PBF-processed 316 L was investigated for its suitability in aerospace applications at cryogenic service temperatures and the behavior at cryogenic temperature was compared with room temperature to understand the properties and microstructural changes within this temperature range. Tensile tests were performed at room temperature and at -196 °C to study the mechanical performance and phase changes. The microstructure and fracture surfaces were characterized using scanning electron microscopy, and the phases were analyzed by X-ray diffraction. The results showed a significant increase in the strength of 316 L at -196 °C, while its ductility remained at an acceptable level. The results indicated the formation of ε and α martensite during cryogenic testing, which explained the increase in strength. Nanoindentation revealed different hardness values, indicating the different mechanical properties of austenite (γ), strained austenite, body-centered cubic martensite (α), and hexagonal close-packed martensite (ε) formed during the tensile tests due to mechanical deformation.

Terahertz Reading of Ferroelectric Domain Wall Dielectric Switching.

Ferroelectric domain walls (DWs) are important nanoscale interfaces between two domains. It is widely accepted that ferroelectric domain walls work idly at terahertz (THz) frequencies, consequently discouraging efforts to engineer the domain walls to create new applications that utilize THz radiation. However, the present work clearly demonstrates the activity of domain walls at THz frequencies in a lead-free Aurivillius phase ferroelectric ceramic, Ca0.99Rb0.005Ce0.005Bi2Nb2O9, examined using THz-time-domain spectroscopy (THz-TDS). The dynamics of domain walls are different at kHz and THz frequencies. At low frequencies, domain walls work as a group to increase dielectric permittivity. At THz frequencies, the defective nature of domain walls serves to lower the overall dielectric permittivity. This is evidenced by higher dielectric permittivity in the THz band after poling, reflecting decreased domain wall density. An elastic vibrational model has also been used to verify that a single frustrated dipole in a domain wall represents a weaker contribution to the permittivity than its counterpart within a domain. The work represents a fundamental breakthrough in understanding the dielectric contributions of domain walls at THz frequencies. It also demonstrates that THz probing can be used to read domain wall dielectric switching.

Visible and infrared transparency in lead-free bulk BaTiO(3) and SrTiO(3) nanoceramics.

Multifunctional transparent ferroelectric ceramics have widespread applications in electro-optical devices. Unfortunately, almost all currently used electro-optical ceramics contain a high lead concentration. In this work, via coupling of spark plasma sintering with high pressure, we have successfully synthesized bulk lead-free transparent nanostructured BaTiO(3) (abbreviated as BTO) and SrTiO(3) (STO) ceramics with excellent optical transparency in both visible and infrared wavelength ranges. This success highlights potential ingenious avenues to search for lead-free electro-optical ceramics.

Ordered coalescence of nanocrystals: a path to strong macroporous nanoceramics.

A versatile approach for integrating two apparently conflicting physical properties, high porosity and high mechanical strength, in polycrystalline bulks is established and demonstrated for the case of alumina ceramics. Macroporous alumina nanoceramics are synthesized by stimulating coalescence-mediated necking, which enables the formation of strong crystallographically coherent necks between adjacent grains. The work places a general emphasis on manipulating crystal growth on the nanoscale and on preparing highly porous polycrystalline bulk ceramics with improved mechanical rigidity.

[Fatigue damage analysis of porcelain in all-ceramic crowns].

OBJECTIVE: To investigate the fatigue damage mechanism of porcelain, and its relation with the microscopic defects in clinically failed all-ceramic crowns. METHODS: Collecting the bilayered all-ceramic crowns failed in vivo. The fractured surfaces and occlusial surfaces of failed crowns were examined by an optical microscope followed by detailed fractography investigations using a field emission scanning electron microscope. When chemical impurities were of concern, energy-dispersive X-ray spectroscopy analysis was performed to examine chemical composition. A standard practice for fractography failure analysis of advanced ceramics is applied to disclose the fracture mode, and damage character. RESULTS: Three types of fracture features are defined as breakdown of the entire crown, and porcelain chipping-off/delamination. Alumina crowns were usually characterized by breakdown of the entire crown, while zirconia crowns by porcelain chipping-off and delamination. The fatigue damage of porcelain was classified into surface wear, cone crack, and porcelain delamination. The observed microscopic defects in this study included air bubbles and impurity particles. CONCLUSION: The multi-point occlusial contacts were recommended in all-ceramic restorations clinically. The thickness of porcelain is important for the anti-fatigue ability of porcelain. Cautions have to be taken to avoid contaminations during the veneering processes.

Three-dimensional trueness and margin quality of monolithic zirconia restorations fabricated by additive 3D gel deposition.

PURPOSE: The aim of this in vitro study was to evaluate the three-dimensional trueness and margin quality of monolithic zirconia restorations fabricated by additive 3D gel deposition, compared with those by subtractive milling. METHODS: Ten single crowns and ten 4-unit FPDs of different occlusal geometries and margin thickness were fabricated by additive 3D gel deposition (additive group) and subtractive milling (subtractive group). An intraoral scanner was used to digitalize the restorations. 3D deviation analysis was applied and root mean square (RMS) was used to assess the trueness. Margin quality was characterized using optical stereomicroscopy and 3D laser scanning microscopy. RESULTS: For single crowns with shallow fossae and grooves and normal margin, RMS value of additive group and subtractive group showed no significant difference in external surface, while additive group showed higher RMS value in intaglio surface. As for 4-unit FPDs with deep fossae and grooves and thin margin, RMS value of additive group in external surface was significantly lower than that of subtractive group and in intaglio surface there was no significant difference between two groups. With a 0.5 mm chamfer design, single crowns in additive group showed flawless margin with a smooth contour line, whereas minor flaws could be observed in 4-unit FPDs with thin margin. In subtractive group, restorations showed minor flaws or defects of various number and severity. CONCLUSIONS: Monolithic zirconia restorations fabricated by additive 3D gel deposition have comparable trueness and better margin quality than those fabricated by subtractive milling. Besides it is more capable of enabling complex geometry.