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KLu3F10:Tb crystals were used to realize excitation-dependent multicolor emissions. Green emissions were observed under 254 nm UV excitation, while blue emission peaking at 442 nm appeared in addition to Tb3+ emissions under 365 nm excitation.

The introduction of K+ into a RbNa3(Li3SiO4)4:Eu2+ phosphor to partially or completely replace Rb+ allows the emission spectrum to be modulated from blue (λ = 473 nm, FWHM = 22.5 nm) to a narrow cyan band (λ = 485 nm, FWHM = 21.1 nm).

A series of novel Ba1-xAl2Si3O4N4: xYb2+ yellow-emissive long-afterglow phosphors was successfully synthesized via a high-temperature solid-state reaction with two sintering steps. The phosphors exhibited broad band emission (full width at half maximum, FWHM = 107 nm) with a peak at 518 nm. With an increase in the Yb2+ doping content in Ba1-xAl2Si3O4N4: xYb2+ phosphors, the luminescence intensity reached a maximum at x = 0.15. The long-afterglow phosphor can be activated effectively by 254 nm UV light, and the afterglow can persist for more than 7 h. From the thermoluminescence (TL) spectrum, there are three types of electron traps, with average evaluation depths of 0.485, 0.592, and 0.681 eV. The afterglow is caused by the capture and re-release of free electrons by the three trap energy levels. Finally, the thermal and chemical stability of the phosphor was tested, its luminescence intensity was 78.7% at 150 °C and 99.5% after 5 h soak in water compared to that at room temperature and original, respectively.

A series of Rb

Recycling Pb from lead acid batteries is rather important in environmental protection, but current strategies need a high temperature or produce secondary pollution. Herein, we present a green reactant recycling method to synthesize PbI2 micro-crystals by extracting the Pb from waste lead acid batteries. Systematical characterizations indicate that the as-prepared PbI2 micro-crystals show high purity, high crystal quality with a 2H-hexagonal crystal structure, and excellent optical properties with a bandgap of 2.3 eV. Based on the recycled 2H-PbI2 micro-crystals, a symmetrically structured ITO/PbI2/ITO photodetector is fabricated. Under 10 V bias voltage, the device reveals a distinct photo-response to UV-visible light and superior performance, with a dark current of 1.06 nA, an on-off ratio of 103, a responsivity of 15.5 mA/W, and a detectivity of 4.7 × 1010 Hz1/2 W−1. In addition, the photodetector also exhibits relatively rapid response speeds of 69 ms (rise time) and 64 ms (decay time). Our study provides an innovative and green strategy for producing a UV-visible photodetector based on recycled lead acid batteries, which is significant in environmental protection and the recycling economy.

We present how the interaction between Al dopants and threading dislocations affects dislocation inclinations and then plays an important role in controlling residual strain in GaN-on-Si epitaxial films. When the Al concentration in the GaN epitaxial film is increased to 0.85%, the dislocations extend almost in the growth direction, contributing to a strain-free epitaxial film. We suggest that the Al atoms could substitute for Ga vacancies at the dislocation cores on the growth surface and then inhibit the dislocation inclinations. The suppressed dislocation inclinations lead to a reduced relaxation of compressive strain. The results pave a new way to control dislocation movements and strain in GaN epitaxial films on Si substrates.

Phosphor is an important part of the new generation of light-emitting diodes (LEDs), which requires high luminous intensity and high-temperature resistance. In this study, a series of excellent (Ba1−x−yCax)AlSi5O2N7:yEu2+ phosphors was developed, which were synthesized by a high-temperature solid-state reaction in a reducing atmosphere. In addition, the crystallinity and luminescence intensity of the samples could be enhanced by some amount of Ca2+ substitution. The luminescence intensity was the highest when the Eu2+ concentration reached 0.06. Furthermore, the thermal stability of the luminescence was studied in detail. The results were satisfactory, showing that the luminescence intensity of the (Ba1−xCax)AlSi5O2N7:Eu2+ phosphors exhibited unique negative-thermal-quenching characteristics both at high (273–473 K) and low (4–273 K) temperatures. And the phosphor combined with UV LED chip and red phosphor Sr2Si5N8:Eu2+ can achieve a CRI of 90.4 in white LED application which indicated the (Ba1−xCax)AlSi5O2N7:Eu2+ phosphor has potential in LED applications.

A series of novel SrMg2(PO4)2:Ce3+,Tb3+(SMP:Ce3+,Tb3+) phosphors with tunable emission spectra were produced via high temperature solid phase method. XRD, fluorescence spectrum and fluorescence lifetime for SMP:Ce3+,Tb3+ were studied in detail. Under the excitation at 308 nm, SMP:Ce3+,Tb3+ samples can emit high efficiency tunable blue-green light by controlling the proportion of dopant concentration. Through the spectral overlap and the regular change of fluorescence lifetime, it is proved that there is a significant energy transfer between Ce3+ and Tb3+ in SMP matrix and the energy transfer mechanism is determined to be an electric dipole–dipole interaction with energy transmission efficiency of 55%. In additional, Commission International de L'Eclairage (CIE) color coordinates and thermal stability were studied. All above findings suggest that SMP:Ce3+,Tb3+ can be regarded as the potential bluish green phosphor for LED applications.

As is well known, a way to obtain a high color resolution and saturation of a liquid crystal display and thereby obtain a higher visual accuracy and comfort in the coming 5G era remains an urgent challenge. In the present study, a new type of phosphor composite material doped with Ln3+ ions provides a promising alternative to the color filters used in White light-emitting diodes (WLEDs), achieving a better performance regarding the realization of a wider color gamut. The advantages of this composite material are illustrated through an abundant phase and morphology analysis along with a discussion regarding the X-ray photoelectron spectroscopy of the valence bond of Ce ions, which maintain the luminescence properties of the phosphor while providing a stable and solid amorphous environment. An improved spectral performance was obtained through color filtering at 580 nm along with the regulating effects of red, green, and blue emissions according to the doped Ln3+ ions. Notably, we fabricated a high-performance WLED based on a Ln3+-doped PiG with a correlated color temperature of 5037 K, color rendering index of 72.8, and high color gamut of 91.97%, providing a new choice for the development of luminescence materials with a high color resolution and saturation.

Being an invasive plant

Phosphor is an important part of the new generation of light-emitting diodes (LEDs), which requires high luminous intensity and high-temperature resistance. In this study, a series of excellent (Ba

The hot stamping technology of aluminum alloy is of great significance for realizing the light weight of the automobile body, and the proper process parameters are important conditions to obtain excellent aluminum alloy parts. In this paper, the thermal deformation behavior of 6016 aluminum alloy at a high temperature is experimentally studied to provide a theoretical basis for a finite element model. With the help of blank stamping finite element software, a numerical model of a 6016 aluminum alloy automobile windshield beam during hot stamping was established. The finite element model was verified by a forming experiment. Then, the effect of the process parameters, including blank holder force, die gap, forming temperature, friction coefficient, and stamping speed on aluminum alloy formability were investigated using Taguchi design, grey relational analysis (GRA), and analysis of variance (ANOVA). Stamping tests were arranged at temperatures between 480 and 570 °C, blank holder force between 20 and 50 kN, stamping speed between 50 and 200 mm/s, die gap between 1.05 t and 1.20 t (t is the thickness of the sheet), and friction coefficient between 0.15 and 0.60. It was found that the significant factors affecting the forming quality of the hot-stamped parts were blank holder force and stamping speed, with influence significance of 28.64% and 34.09%, respectively. The optimal parameters for hot stamping of the automobile windshield beam by the above analysis are that the die gap is 1.05 t, the blank temperature is 540 °C, the coefficient of friction is 0.15, stamping speed is 200 mm/s, and blank holder force is 50 kN. The optimized maximum thickening rate is 4.87% and the maximum thinning rate is 9.00%. The optimization method used in this paper and the results of the process parameter optimization provide reference values for the optimization of hot stamping forming.

Background Accumulating data have established that microRNAs (miRNAs) play significant regulatory roles in the carcinogenesis and progression of ovarian cancer (OC). MiR-425-5p was reported to function in various tumors. However, the roles and underlying mechanism of miR-425-5p involvement in OC development and progression are unclear. Methods A comprehensive strategy of data mining, computational biology, and real-time polymerase chain reaction was employed to identify the involvement of miR-425-5p in OC progression. The effect of miR-425-5p on the proliferation, migration, and invasion of OC cells was determined using Cell Counting Kit-8, wound-healing, and Matrigel invasion assays, respectively. Luciferase assay was performed to evaluate the interactions between miR-425-5p and MAGI2-AS3 or AFF4. Results miR-425-5p was significantly up-regulated in OC tissues and cells. The luciferase reporter assay revealed that miR-425-5p was negatively regulated by MAGI2-AS3. Silencing miR-425-5p inhibited the proliferation, migration, and invasion of OC cells in vitro. Bioinformatics analysis and luciferase reporter assay revealed that AFF4 was the target gene of miR-425-5p. Moreover, AFF4 expression was significantly decreased in OC and was closely related to the good prognosis of patients with OC. AFF4 overexpression inhibited the proliferation, migration, and invasion of OC cells in vitro. By contrast, silencing AFF4 promoted the proliferation, migration, and invasion of OC cells in vitro. Finally, AFF4 suppression rescued the inhibitory effect of silencing miR-425-5p on the proliferation, migration, and invasion of OC cells. Conclusion To the best our knowledge, this is the first study to demonstrate that miR-425-5p overexpression in OC is negatively regulated by MAGI2-AS3. Moreover, miR-425-5p promotes the proliferation, migration, and invasion of OC cells by targeting AFF4, suggesting that miR-425-5p/AFF4 signaling pathway represented a novel therapeutic target for patients with OC.

Given an n-vertex graph G with maximum degree Δ, the mixed graph DG is constructed from G by orienting some of its edges, where G is called the underlying graph of DG. Let rH(DG) be the H-rank of D...

Jaeger, Linial, Payan and Tarsi (JCTB, 1992) introduced the concept of group connectivity as a generalization of nowhere-zero flow for graphs. In this paper, we introduce group connectivity for signed graphs and establish some fundamental properties. For a finite abelian group A , it is proved that an A -connected signed graph is a contractible configuration for A -flow problem of signed graphs. In addition, we give sufficient edge connectivity conditions for signed graphs to be A -connected and study the group connectivity of some families of signed graphs.

The surface plasmon resonance (SPR) of metal nanostructures is known to affect the optical properties of solid luminescent materials. Ag nanoparticles were first used to obtain a wider color gamut in rare-earth-doped phosphor-in-glass for application as color filters for white light emitting diodes. The existence of Ag nanocrystallites at nanometer scale and the independent integrity of the phosphor luminescence center in the amorphous glass environment were demonstrated. Using UV–Vis spectroscopy, the localized SPR absorption band was observed at 480 nm, and the optical properties of the nanostructures were found to be dependent on the annealing temperature. Hence, an expansion of the color gamut from 79.07% to 93.31% was realized by the coefficient effect of N d 3 + active ions and Ag nanoparticles. These results suggest that N d 3 + -ion-co-doped phosphor-in-glass modified by Ag nanoparticles could be potentially applied as a novel optical material with a wide color gamut.

We report a detailed spectroscopic investigation of a series of fluorotellurite glasses with different Er3+ ions concentration in system 50TeO2-27BaF2-9ZnF2-8YF3-3MgF2-3NaF-xErF3-1HoF3(x = 1,2,3 mol%). Intense 2 μm emission and 2.75 μm emission with high absorption and emission cross-section were observed under 980 nm LD pumping, and the maximum gain coefficient around 2750 nm was as high as 2.41 cm−1, suggesting the prepared glasses are a competitive candidate for mid-infrared laser materials. Besides, it was found that the trend of 2 μm and 2.75 μm emission intensity varied with Er3+ ions concentration was different. Energy transfer process was discussed subsequently to explain this phenomenon. Furthermore, we quantitatively investigate the energy transfer efficiency from Er3+: 4I13/2 level to Ho3+: 5I7 level.

The classification of symmetric graphs has always been a hot topic in algebraic graph theory. Here, we give a complete classification of the all connected prime-valent symmetric graphs admitting a transitive alternating automorphism group.

White light-emitting diodes (LEDs), as a fourth-generation green lighting source, have been widely used in various fields. At present, most white LEDs have based on a mixture of silicone with poor heat resistance and phosphors as luminescent components, which prevent them from adapting to high-temperature environments and limit their applications of high-power lighting. To improve the optical properties and reliability of white LEDs, phosphor solid is proposed as a new alternative, which not only has the strong stability of glass, but also completely retains the luminescent properties of phosphor. Therefore, in this study, tellurite glass was used as the matrix of phosphor solids to improve the luminescence performance by optimizing the composition of the matrix glass. In addition, rare earth ions were introduced into the tellurium glass matrix, and the dissolution ability of the matrix to rare earth ions was explored to improve the luminous quality of white LEDs.

A series of β-Sr1.98-yMgySiO4-1.5xNx: 0.02Eu2+ (x = 0, 0.3, 0.6, 0.9, 1.2 and 4/3, 0 ≤ y ≤ 0.5, β-S(M)SON: Eu2+) phosphors were synthesized by a conventional solid state reaction method. The coordination environments of Eu2+ are modified effectively via the introduction of N3- and Mg2+ using different concentration, which is confirmed by XRD refinement results and PL spectra. Both fourier transform infrared (FT-IR) spectra and energy dispersive spectroscopy (EDS) analysis qualitatively confirm that the existence of N3-. The crystal structures of β-Sr2SiO4-1.5xNx (β-SSON): Eu2+ and β-Sr2-yMgySi(O,N)4: Eu2+ (β-SMSON, x = 4/3, y = 0.1) have been determined effectively. Rietveld refinement indicates that N3- dopants most likely partly substitute O22− site. With the increase of N content, the unit cell volume and partial Si O and Sr N bond lengths gradually decrease, which are coincided each other. With the introduction of N3-, the emission of Eu(I) (∼465 nm) hardly change but that of Eu(II) (∼540 nm) splits into two emission bands as Eu(II) (∼540 nm) and Eu(II)′ (∼616 nm). According to the analysis of XRD data, unit cell volume, FT-IR spectra, photoluminescence (PL) and reflectance spectra of β-SMSON: Eu2+, it can be concluded that the incorporation of Mg2+ into the host leads to interstitial sites rather than substitutional ones. Mg2+ doping couldn't change the dominant peak wavelengths (DPWs) of Eu(I), Eu(II) and Eu(II)′ sites but only affects the PL intensity of title phosphors and could offset the nitridation effects. The concentration quenching mechanism and thermal activation energy of β-SSON: Eu2+ phosphors are determined effectively. The β-S(M)SON: 0.02Eu2+ phosphor have the feature that it can achieve color-tunable white light-emitting combined with blue light emitting diodes (LEDs) with single activator doped and single-phase host, which enables these materials to be enormous possibilities used in white light emitting diodes.

The aim of the present study was to investigate the expression of fibulin-2 and β-catenin in gastric cancer tissues and the association to mutual regulation. Forty-nine cases of gastric cancer specimens obtained via surgical resection in the Pathology Department of Heping Hospital Affiliated to Changzhi Medical College from March 2013 to August 2017 were collected. The expression levels of fibulin-2 and β-catenin in 49 cases of gastric cancer and para-carcinoma tissues were detected via quantitative polymerase chain reaction and immunohistochemistry. The correlation of expression of fibulin-2 and β-catenin proteins in gastric cancer was detected via Spearman's analysis. The correlation of fibulin-2 and β-catenin protein expression with clinicopathological indexes of patients was also analyzed. Moreover, the fibulin-2 overexpression plasmid was constructed and transfected into human gastric cancer AGS and SGC-790 cell lines, so as to observe changes in β-catenin and its downstream indexes. Fibulin-2 messenger ribonucleic acid (mRNA) level in gastric cancer tissues was significantly lower than that in para-carcinoma tissues, while β-catenin mRNA level was significantly increased (P

A series of novel blue-emitting Ba1-xAl2Si3O4N4: xEu2+ phosphors were successfully prepared by two-steps high temperature solid state reaction. The results of XRD and SEM showed that the two-steps method obtain less impurities than the traditional one-step method. The electronic band structure of BaAl2Si3O4N4 (BASON) host was calculated as a direct band gap of 3.662eV by the DFT method. The PLE spectrum of B1-xASON: xEu2+ showed a wide band excitation in the wavelength range of 250–450 nm, which can be well matched with n-UV chips. Based on crystal structural and fluorescence lifetime analysis, three emission peaks were obtained by gaussian fitting to explain the asymmetry of Eu2+ emission in the BASON phosphor. The optimal doping concentration of Eu2+ was x = 0.04. According to calculated critical distance (3.24 A) and a little overlap between PLE and PL spectra, the concentration quenching mechanism was confirmed as both of dipole-dipole interaction and radiation reabsorption. In addition, with the incorporation of Eu2+, the diffuse reflection spectrum of B1-xASON: xEu2+ presented a wide absorption peak in the range of 200–500 nm. The PL intensity of Ba0.96-ySryAl2Si3O4N4: 0.04Eu2+ tended to rise first and then fall with the increase of Sr2+ concentration. Impressively, the relative emission intensity at 473K still maintained 95.7% compared with room temperature (293K), which indicated the excellent thermal stability of BASON phosphor. Finally, the density of state (DOS) of Ba1-ySryAl2Si3O4N4 (y = 0, 0.5, 1) were calculated and analyzed to explain the deterioration of thermal stability with the increase of Sr2+ substitution.

The energy of a graph is defined as the sum of the absolute values of all eigenvalues of the graph. Let T n , p , T n , d be the set of all trees of order n with p pendent vertices, diameter d, respectively. In this paper, we completely characterize the trees with second-minimal and third-minimal energy in T n , p ( T n , d , respectively) for 4 ? p ? n - 9 ( 10 ? d ? n - 3 , respectively), which solves the problems left in Ma (2014).

A series of novel Ce3+ and/or Sm3+ activated Y4SiAlO8N (YSAON) phosphors are successfully synthesized by a conventional solid-state reaction method. The formation of monophasic YSAON is confirmed by X-ray powder diffraction (XRD) analysis. The crystal structure of YSAON is solved by XRD refinement data. DFT calculations indicate that Y4SiAlO8N has an indirect band gap of 3.819 eV. Based on the analysis of crystal structure and lifetime curves, four emission sites of YSAON:0.02Ce3+ are identified, which are Y1 (413 nm, 448 nm), Y2 (428 nm, 469 nm), Y3 (619 nm, 698 nm) and Y4 (512 nm, 569 nm), respectively. The concentration quenching of Ce3+ in YSAON is investigated in detail and it is confirmed to be due to dipole–dipole interactions. Photoluminescence excitation (PLE) and photoluminescence (PL) spectral measurements showed that the Ce3+ and Sm3+ co-doped phosphor could be efficiently excited by near-UV light, and exhibited four emission bands peaked at 485 nm, 565 nm, 605 nm and 650 nm, respectively. The CIE chromaticity coordinates of the obtained white light can be tuned by adjusting the content of Ce3+ and Sm3+ ions. Therefore, we anticipate that these materials can be used in near-UV chip pumped white LEDs.

Phosphors Ca 4 (PO 4 ) 2 O:Ce 3+ /Li + , Eu 2+ were prepared by solid state reaction successfully, and characterized by X-ray diffraction, UV-Vis spectrometer and photoluminescence spectrometry. The as-prepared phosphors exhibited strong absorption in the UV-visible region and dual-emission bands centered at approximately 460 and 630 nm. Energy transfer from Ce 3+ to Eu 2+ was also observed. By varying the excitation wavelength, these new phosphors exhibited tunable emissions from blue to white and then to yellow, making them potential candidates as UV-convertible phosphors for white light emitting diodes.

A series of novel green Y4−xSiAlO8N:xTb3+ phosphors have been prepared by a high temperature solid state reaction. The phase formation and structural properties were analyzed by X-ray powder diffraction. The XRD results and SEM images show that the Y3+ can be substituted by Tb3+ for the max content of x = 1.5 and the most suitable sintering temperature is about 1500 °C. The PLE spectra of Y4−xSiAlO8N:xTb3+ phosphors exhibit a wide excitation band ranging from 200 to 500 nm, which matches well with the characteristic emission of n-UV chips. Under excitation of 380 nm, the phosphor shows four intense emission bands with emission peaks at 488 nm, 543 nm, 585 nm and 624 nm, respectively. These emissions were attributed to the characteristic 5D4 → 7FJ (J = 6, 5, 4, 3) transitions of Tb3+ ions. The optimum doping concentration of Tb3+ was found to be x = 2.0 which indicated that the concentration quenching effect in the Y4−xSiAlO8N:xTb3+ phosphor is very weak. The critical distance for the Tb3+ ions calculated by the concentration quenching is 3.64 A. The detailed nonradiative energy transfer mechanism between Tb3+ ions is confirmed to be via a dipole–dipole interaction by the fluorescence decay analysis. Furthermore, with the introduction of Tb3+ ions, the reflectance spectra shows an obvious increment of reflectance in the region of 200–250 nm, which is due to the variation of electronic structure in the conductance band derived from Y3+ ions. Finally, the excellent thermal stability of the phosphors was demonstrated by the temperature dependence of the PL spectra. Compared to the initial intensity at room temperature (293.0 K), the relative PL intensity maintains high value of 96.5% at 475.2 K. The detailed thermal quenching behavior has also been interpreted.

Transparent Cr 4+ doped SiO 2 -Al 2 O 3 -ZnO-Li 2 O-K 2 O glass ceramics were prepared by conventional melting method. X-ray diffraction analysis revealed that dual nanocrystals of Zn 1.7 SiO 4 and Li 1.14 Zn 1.43 SiO 4 were precipitated in the glass matrix after 700 °C heating treatment. Broad infrared luminescence centered at 1261 nm and 1304 nm with a full width at half maximum (FWHM) of more than 250 nm was observed excited by an 808 nm excitation laser diode. And the lifetime was about 145.85 μs at 1261 nm and 179.56 μs at 1304 nm. Compared with Cr 4+ doped SiO 2 -Al 2 O 3 -ZnO-Li 2 O-K 2 O glass ceramics containing single phase of Zn 1.7 SiO 4 or Li 1.14 Zn 1.43 SiO 4 , this novel glass ceramics had wider FWHM and longer lifetime.

Vacuolar-type H+-ATPase (V-ATPase), a multisubunit proton pump located on the endomembrane, plays an important role in plant growth. The Arabidopsis thaliana V-ATPase d subunit (VHA-d) consists of two isoforms, AtVHA-d1 and AtVHA-d2. In this study, the function of AtVHA-d2 was investigated. Histochemical analysis revealed that the expression of AtVHA-d1 and AtVHA-d2 was generally highly overlapping in multiple tissues at different developmental stages of Arabidopsis. Subcellular localization revealed that AtVHA-d2 was mainly localized to the vacuole. AtVHA-d2 expression was significantly induced by oxidative stress. Analysis of phenotypic and H2O2 content showed that the atvha-d2 mutant was sensitive to oxidative stress. The noninvasive microtest monitoring demonstrated that the net H+ influx in the atvha-d2 roots was weaker than that in the wild-type under normal conditions. However, oxidative stress resulted in the H+ efflux in atvha-d2 roots, which was significantly different from that in the wild-type. RNA-seq combined with qPCR analysis showed that the expression of several members of the plasma membrane H+-ATPase gene (AtAHA) family in atvha-d2 was significantly different from that in the wild-type. Overall, our results indicate that AtVHA-d2 plays a role in Arabidopsis in response to oxidative stress by affecting H+ flux and AtAHA gene expression.

Plant SWEETs (Sugars Will Eventually be Exported Transporters) affect the growth of plants by regulating the transport of sugar from source to sink and its intracellular transport between different organelles. In this study, DsSWEET17 from Dianthus spiculifolius was identified and characterized. Real-time quantitative PCR analysis revealed that the expression of DsSWEET17 was affected by exogenous application of fructose and glucose as well as under salt, osmotic, and oxidation stress. Colocalization experiments showed that the DsSWEET17-GFP (green fluorescent protein) fusion protein was localized to the FM4-64-labeled tonoplasts in Arabidopsis. Compared to the wild type, the transgenic Arabidopsis seedlings overexpressing DsSWEET17 had longer roots, greater fresh weight, and a faster root growth upon exogenous application of fructose. Furthermore, transgenic Arabidopsis seedlings had significantly higher fructose accumulation than was observed for the wild-type seedlings. The analysis of root length revealed that transgenic Arabidopsis had higher tolerance to salt, osmotic, and oxidative stresses. Taken together, our results suggest that DsSWEET17 may be a tonoplast sugar transporter, and its overexpression affects sugar metabolism and confers multiple stress tolerance in Arabidopsis.

The energy of a graph $G$, denoted by $E(G)$, is defined as the sum of the absolute values of all eigenvalues of $G$. Let $n$ be an even number and $\mathbb{U}_{n}$ be the set of all conjugated unicyclic graphs of order $n$ with maximum degree at most $3$. Let $S_n^{\frac{n}{2}}$ be the radialene graph obtained by attaching a pendant edge to each vertex of the cycle $C_{\frac{n}{2}}$. In [Y. Cao et al., On the minimal energy of unicyclic H\"{u}ckel molecular graphs possessing Kekul\'{e} structures, Discrete Appl. Math. 157 (5) (2009), 913--919], Cao et al. showed that if $n\geq 8$, $S_n^{\frac{n}{2}}\ncong G\in \mathbb{U}_{n}$ and the girth of $G$ is not divisible by $4$, then $E(G)>E(S_n^{\frac{n}{2}})$. Let $A_n$ be the unicyclic graph obtained by attaching a $4$-cycle to one of the two leaf vertices of the path $P_{\frac{n}{2}-1}$ and a pendent edge to each other vertices of $P_{\frac{n}{2}-1}$. In this paper, we prove that $A_n$ is the unique unicyclic graph in $\mathbb{U}_{n}$ with minimal energy., Comment: 20 pages

A series of disordered α′-Sr2Si3x/4O2Nx:Eu2+ (1.333 ≤ x ≤ 2.4) phosphors were synthesized by the conventional solid state reaction method. The disordered α′-Sr2Si3x/4O2Nx:Eu2+ (α′-SSON:Eu2+) phosphors have two distinct activation centers: Eu(I) and Eu(II). With the increase of N concentration, both the luminescence intensity and the dominant peak wavelength (DPWs, which is about 490 nm) of the Eu(I) site were extraordinarily unchanged. In comparison with the yellow emissions (∼580 nm) of the Eu(II) site of the disordered α′-Sr2SiO4:Eu2+, the DPWs of Eu(II) emissions were at red spectral regions (609–618 nm), which depends on the amount of N3−. The PL intensity of the Eu(II) emission band increased first and then decreased, and reached a maximum at x = 2. The disordered α′-SSON is a substitutional solid solution. Compared with the disordered α′-Sr2SiO4, all the lattice constants of disordered α′-SSON became smaller which led to the decrease of the cell volume. The peaks of the Si–N and Sr–N bond could be observed in FT-IR spectra. The Si–(N/O)4 tetrahedrons transformed from Si–O4, Si–NO3, and Si–N2O2 into Si–N3O with the increase of N content. The bond lengths of Si–N and Sr–(N/O) were within the normal ranges compared with other silicon-based oxynitrides. The Si–O bond lengths became shorter due to the extrusion effects of longer Si–N bonds. Both of the average bond lengths of Sr1–(N/O) and Sr2–(N/O) in disordered α′-SSON became longer than that of disordered α′-Sr2SiO4. Due to the red emission and high photoluminescence intensity of the disordered α′-Sr2Si3x/4O2Nx:Eu2+ (1.333 ≤ x ≤ 2.4), we anticipate that these materials can be used as red phosphors in white light emitting diodes.

A series of Sr1.98−xBaxSi(O,N)4: 0.02Eu2+ (0 ≤ x ≤ 0.5) phosphors were synthesized by a conventional solid state reaction method. The Sr–N and Si–N bonds could be observed in FT-IR spectra. The XRD refinement results indicated that N3− would substitute for O22− and form Si–NO3 tetrahedrons during the process of forming the Sr1.98Si(O,N)4: Eu2+ (SSON: Eu2+) substitutional solid solution. The lattice constants of Sr1.98−xBaxSi(O,N)4: 0.02Eu2+ (SBSON) were increased due to the longer bond length of Ba–O. Compared with Sr2SiO4: Eu2+, the SSON: Eu2+ showed a remarkable red-shift, which is due to the nephelauxetic effect and the strong crystal field splitting originating from the stronger covalent bonding effect of the Eu–N bond. The SSON: Eu2+ presented a β phase structure before the introduction of Ba2+, whereas the α′-SBSON phase was obtained by the substitution of Ba2+ for Sr2+. Ba2+ doping led to an obvious blue-shift under 375 nm and 460 nm excitation. The 5d orbital of Ba2+ is coupled with the 5d orbital of Eu2+ on the higher energy level position in the host crystal. Under 375 nm excitation, the PL intensity gradually increased with the increase of the Ba2+ content. Under 460 nm excitation, the PL intensity gradually declined with the increase of Ba2+ content. The thermostability of α′-SBSON: Eu2+ was significantly improved compared with β-SSO: Eu2+ and β-SSON: Eu2+. On the basis of their adjustable emission wavelength, enhanced PL intensity and excellent thermostability in SBSON: Eu2+, we anticipate that these materials can be used as green or red phosphors in white light emitting diodes.

Ca(Mg 0.92 Al 0.08 )(Si 0.96 Al 0.04 ) 2 O 6 ceramics with different amounts of TiO 2 /CaTiO 3 additions were prepared by the solid-state reaction method. The sintering behavior, microstructure and microwave dielectric properties of TiO 2 /CaTiO 3 -added ceramics were investigated. The control of the temperature coefficient of resonant frequency ( τ f ) could be achieved by varying the content of TiO 2 or CaTiO 3 . Particularly, TiO 2 reacted with the main ceramic phase of Ca(Mg,Al)(Si,Al) 2 O 6 and produced secondary phases of MgTi 2 O 5 and CaTiSiO 4 O, which lowered the Q × f values of the ceramics. TiO 2 -added ceramics sintered at 1225 °C with 22 wt% TiO 2 additions showed dielectric properties of e r =12.06, Q × f =5940 GHz and τ f =2.24 ppm/ o C. Comparing with the TiO 2 -added ceramics, CaTiO 3 just existed as a separate component, and the Ca(Mg 0.92 Al 0.08 )(Si 0.96 Al 0.04 ) 2 O 6 ceramic sintered at 1250 °C with 10 wt% CaTiO 3 additions showed a good combination of dielectric properties: e r =9.6, Q × f =32,590 GHz and τ f =−1.53 ppm/ o C.

The influence of coating thickness on laser-induced damage (LID) characteristics of anti-reflection (AR) coatings irradiated by 1064 nm nanosecond laser pulses was investigated. Two HfOsub2/sub/SiOsub2/subAR coatings with different physical thicknesses, 0.7 and 2.7 μm, were prepared and tested. To study the effect of coating thickness on a laser-induced damage threshold (LIDT) in isolation, electric field intensities (EFIs) at the substrate-coating interface were kept the same by using proper AR designs. Moreover, 2 nm artificial gold particles with a density of 10 mmsup-2/supwere implanted into the substrate-coating interface to achieve reliable experimental results. An optical microscope (OM) and a scanning electron microscope (SEM) were used for an online LIDT test and offline LID morphology observation, respectively. The typical LID morphology of thicker AR coatings was flat bottom craters with diameters of 20-50 μm, which can be easily observed by an online OM. For thinner AR coatings, hemispherical craters with diameters down to 1 μm were found as typical LID morphology by a SEM. However, these tiny craters could not be observed by an online OM. Moreover, such tiny craters did not grow with subsequent pulses, so they did not degrade the functional laser damage resistance of the thin AR coatings. When identified with an online OM, the LIDT of thinner AR coatings is found to be about two times higher than the thicker ones, and large delamination was mainly found as the LID morphology of AR coatings with high fluence. When observed with a SEM, the LIDT of thin AR coatings with tiny craters was over 60% lower than the LIDT of thick AR coatings, which agrees with the model that less energy is required to form smaller LID craters of thinner coatings.

A series of Ce 3 + /Sm 3 + doped glasses were prepared in this study and their luminescence properties were analyzed. A combination of blue and orange-red emission band was observed from these glasses, and tunable white light emission could be observed by adjusting concentration ratio of Ce 3 + to Sm 3 + under UV light excitation. Energy transfer (ET) from Ce 3 + to Sm 3 + is discovered by directly observing significant overlap of the excitation spectrum of Sm 3 + and the emission spectrum of Ce 3 + ions. The energy transfer from Ce 3 + to Sm 3 + via a dipole–dipole mechanism was confirmed by the luminescence spectra, the decay lifetime and the calculation of energy transfer efficiency of the glasses. Based on the results in this study, the Ce 3 + /Sm 3 + doped glasses could be used as a potential matrix material for ultraviolet light emitting diode (LED) chip based white LEDs.

The effects of Al2O3 content on the densification, phase compositions, microstructure and microwave dielectric properties of CaMgSi2O6–Al2O3 ceramics were investigated. The Al2O3 addition in CaMgSi2O6 ceramics resulted in the presence of a new phase, e.g. Ca(Mg,Al)(Si,Al)2O6, and caused the emergence of Ca vacancies and O vacancies. The solubility limit of Al2O3 in Ca(Mg,Al)(Si,Al)2O6 was found to be 4–8 wt%, and second phases of CaAl2Si2O8 and (Mg,Al)8(Si,Al)6O20 were observed when the Al2O3 addition exceeded 8 wt%. Appropriate Al2O3 addition promoted the sintering process and lowered the densification temperature due to the vacancies defects caused by the Al3+ substitution for Mg2+ and Si4+ and the liquid phase originated from the second phases. Typically, good microwave dielectric properties of ϵr = 7.99, Q × f = 60,132 GHz and τf = −48.21 ppm/°C were obtained when the Al2O3 addition was 12 wt% and the as-prepared composite ceramic was sintered at 1250 °C.

Orange emitting Sr2.96−xBaxSiO5: Eu2+ phosphors have been synthesized by a method using Sr2SiO4 instead of simple oxides and carbonate as precursor. The photoluminescence properties, radiative lifetime and formation process were investigated by PL spectra, lifetime decay and XRD analysis, respectively. X-ray diffraction analysis indicates that the phosphor has a single phase of Sr3SiO5 without residual Sr2SiO4 and BaSi4O9 phases. Under 460 nm excitation, the emission band of Sr2.96−xBaxSiO5: Eu2+ has a red-shift from 580–598 nm due to varied Ba2+ concentration. Particularly, the emission intensity of Sr2.56Ba0.4SiO5: 0.02Eu2+ sample increased significantly in comparison with the commercial SSE phosphor. The radiative lifetime τ0 are estimated to be 1.999, 2.316, 2.716 and 2.932 μs for samples of x=0, 0.2, 0.4 and 0.6, respectively. It indicates that Eu2+ ions are in different surroundings and the Sr2+ sites were substituted by Ba2+ completely. Compare with the conventional solid-state reaction method, the Sr2.96−xBaxSiO5: Eu2+ phosphors synthesized by this method show higher crystallinity and more efficient orange emission.

Growth behaviors of initial damage sites are important in investigating laser-induced damage mechanisms of optical materials and in evaluating the lifetime of optical components. The characteristics of the initial damage sites initiated by different fluences were investigated to determine the effects of the initial conditions on damage growth. Two kinds of experiments, fixed and ramp-up fluences, were conducted under a 355 nm small laser beam to obtain the growth behaviors in terms of morphology, lateral size, as well as crater and crack depth. Preliminary statistical results revealed the relationship between the growth trends and initiating and subsequent laser fluences. As the main features of damage growth, visible cracks are categorized into three main types, which are associated with the laser irradiation.

A green-emitting phosphor, Eu 2+ -activated Ba 3 Si 6 O 9 N 4 phosphor, was synthesized by a conventional solid state reaction method. X-ray diffraction patterns showed that the synthesized phosphor sintered at 1300 °C for 6 h was a Ba 3 Si 6 O 9 N 4 pure phase. It could be efficiently excited by UV–blue light (280–500 nm) and showed a single intense broad emission band (470–625 nm). Suitable excitation range makes it match well with the emission of near-UV or blue LEDs. Concentration quenching of the doped-Eu 2+ ions occurred at x =0.15, and the critical distance is calculated to be about 1.807 nm by theory of energy transfer. The result indicates that Ba 3 Si 6 O 9 N 4 :Eu 2+ is a promising green-emitting phosphor for white LEDs.

The diopside ceramics with a formula of Ca(Mg1−xAlx)(Si1−x/2Alx/2)2O6 (x=0.01–0.3) were synthesized via a traditional solid-state reaction method, and their solid solubility, sintering behavior and microwave dielectric properties were investigated. The results revealed that the solubility limit of Al2O3 in Ca(Mg1−xAlx)(Si1−x/2Alx/2)2O6, which is defined as x, was between 0.15 and 0.2, and a second phase of CaAl2SiO6 presented when the x value reached 0.2. Appropriate Al3+ substitution for Mg2+ and Si4+ could promote the sintering process and lower the densification temperature, and a broadened densification temperature range of 1250–1300 °C was obtained for the compositions of x=0.08–0.15. With the increase of the x value, the dielectric constant (er) increased roughly linearly, and the temperature coefficient of frequency (τf) showed a rising trend. The Q×f values increased from 57,322 GHz to 59,772 GHz as the x value increased from 0.01 to 0.08, and then they were saturated in the range of x=0.08–0.2. Further increase of the x value (x≥0.25) deteriorated the microwave dielectric properties. Good microwave dielectric properties of er=7.89, Q×f=59,772 GHz and τf=−42.12 ppm/°C were obtained for the ceramics with the composition of x=0.08 sintered at 1275 °C.

Ba 3 Si 6 O 9 N 4 phosphors co-doped with Ce 3+ and Eu 2+ were synthesized via the solid-state reaction method. The samples could display varied color emission from blue and ultimately to green under the excitation of ultraviolet (UV) light or blue light with the appropriate adjustment of the relative proportion of Ce 3+ /Eu 2+ . The luminescence intensity of Ba 3 Si 6 O 9 N 4 :Eu 2+ can be efficiently enhanced by codoping with Ce 3+ . The energy transfer mechanism from Ce 3+ to Eu 2+ in Ba 3 Si 6 O 9 N 4 :Ce 3+ , Eu 2+ is electric dipole–dipole interaction, and the critical distance is calculated to be about 24.86 A by the spectra overlap method.