Radiobiological Insights of Staged Brachytherapy Using Eye Plaque for Large Uveal Melanoma

PURPOSE/OBJECTIVE(S)

I-125 radioactive seeds embedded in an eye plaque is used to deliver the radiation dose of 85Gy to the apex of the tumor. However, it is challenging to treat a lesion in height (>10 mm) because of a high dose (> 500 Gy) to sclera. A staged radiotherapy (SRT) has been implemented successfully in stereotactic radiosurgery when a single dose is risky for a bigger sized lesion. The hypothesis of this work is that the SRT works for eye plaque brachytherapy of uveal melanoma to break the single fraction into two. To apply the concept of SRT, the following questions need to be answered: What are the two fraction doses? What is the time interval between the two fractions? In this work, the two split fraction doses and time interval are calculated using the "incomplete-repair' model.

MATERIALS/METHODS

Equation (1) is the linear-quadratic (LQ) model. f(x) is the cell survival curve (SC). Equation (2) and (3) are radiobiological model developed dealing with the split doses by considering the incomplete repair. Ln(f(x)) = -αx - βx2 (1) Ln(fn(x, Ɵ)) = nLn(f(x))-nβx2hn(Ɵ) (2) hn(Ɵ) = (2/n)[ Ɵ/(1- Ɵ)][n-(1- Ɵn)/(1- Ɵ)] (3) Ɵ = exp(-µΔt) (4) x represents the fraction dose, Ɵx is the initial segment of the survival curve, Ɵ determines the rate at which repair proceeds. n is fraction number and µ represent repair constant which equals to ln2/T1/2. T1/2 is the half-life of I-125. For continuous dose vt delivered at dose rate v for time t, with repair constant µ, the LQ model is modified as Ln (f(vt, µ)) = -α(vt) -β(vt)2g(µt) (5) g(µt) = 2[µt-1+exp(-µt)]/(µt)2 (6) Assuming biological effective dose (BED) is the same for the single fraction and split two fractions, SC when n = 1 should be same as when n = 2. Therefore, the equation (7) is derived. Ɵ = [(α/β)x1 - 2(α/β)(x2)2 + (x1)2]/2(x2)2 - 1 (7) x1 is single fraction dose of 85Gy, x2 is the split dose to two fractions. α/β ratio of 10 Gy is used. By fitting the equation (7), the ranges of doses and time intervals were determined.

RESULTS

The fraction doses and time interval to get the same BED as single fraction of 85 Gy are determined from 45 Gy to 50 Gy with time interval of 22 days to 76 days for staged brachytherapy eye plaque (SBEP). Our result is matched the treatment protocol for SBEP reported, e.g., 1st fraction dose of 40Gy and 50 Gy of 2nd fraction with 73 days of time interval are used. The max. dose of scleral dose is 328 Gy compared to the single fraction scleral dose of 543Gy.

CONCLUSION

This work could provide guidelines in SBEP in dosage and time interval. The height of tumor matters the most in the SBEP since the taller the tumor, the higher dose to the sclera is. Reference.

Difference in Radiotherapeutic Plan of HyperArc-Based and CyberKnife-Based Stereotactic Radiotherapy (SRT) Techniques for Multiple Brain Metastases

PURPOSE/OBJECTIVE(S)

The purpose of this study is to compare the dosimetric quality and dose to surrounding normal tissue of HyperArc-based stereotactic radiotherapy (SRT) technique with a frameless robotic radiosurgery system for patients with multiple brain metastases.

MATERIALS/METHODS

Nineteen patients with multiple brain metastases (2-5 lesions) treated in our center were enrolled. The prescribed dose was 2100 cGy to 3250 cGy in three to five fractions. In order to determine the dosimetric quality, we compared the conformity index (CI), Gradient radius (GR), homogeneity index (HI), dose distribution in planning target volume, and dose to several organs at risk (OARs). All of the data were compared using pair-T test.

RESULTS

Both planning systems have prescribed dose coverage to GTV and PTV with no significant difference (P = 0.243; P = 0.312). The conformity index (CI), and homogeneity index (HI) were 1.27 ±0.022, and 1.08 ±0.006, respectively, for HyperArc plan and 1.76 ±0.065 and 1.22 ±0.009, respectively, for the CK plan (both, P< 0.001). The Gradient radius (GR) was 0.732 ±0.056 cm for HyperArc plan and 0.847 ±0.762 cm for CK plan (P = 0.002). These indicated that HyperArc plan had better CI, HI, and GR when compared to CK plan. Maximum dose to brainstem for HyperArc and CK plans were 485.1 ±128.65 and 723.6 ±126.93 cGy, respectively (P < 0.001). Moreover, HyperArc plan had less mean dose to optic chiasm, bilateral eyes, bilateral lens, and bilateral optic nerves (all, P < 0.05). Brain V5, V12, V24 were all much smaller in HyperArc plan (all, P < 0.05), indicating that HyperArc plan delivered less dose to normal brain tissue.

CONCLUSION

For patients with two to five brain metastases, HyperArc-based SRT provide excellent dosimetric quality and less dose to normal tissue.

Surface plasmon coupling effects on the photon color conversion behaviors of colloidal quantum dots in a GaN nanoscale hole with a nearby quantum-well structure

To improve color conversion performance for color display application, we study the near-field-induced nanoscale-cavity effects on the emission efficiency and Förster resonance energy transfer (FRET) under the condition of surface plasmon (SP) coupling by inserting colloidal quantum dots (QDs) and synthesized Ag nanoparticles (NPs) into surface nano-holes fabricated on a GaN template and an InGaN/GaN quantum-well (QW) template. In the QW template, the inserted Ag NPs are close to either QWs or QDs for producing three-body SP coupling to enhance color conversion. Time-resolved and continuous-wave photoluminescence (PL) behaviors of the QW- and QD-emitting lights are investigated. The comparison between the nano-hole samples and the reference samples of surface QD/Ag NP shows that the nanoscale-cavity effect of the nano-hole leads to the enhancements of QD emission, FRET between QDs, and FRET from QW into QD. The SP coupling induced by the inserted Ag NPs can enhance the QD emission and FRET from QW into QD. Its result is further enhanced through the nanoscale-cavity effect. The relative continuous-wave PL intensities among different color components also show the similar behaviors. By introducing SP coupling to a color conversion device with the FRET process in a nanoscale cavity structure, we can significantly improve the color conversion efficiency. Simulation results confirm the basic observations in experiment.

Photon color conversion enhancement of colloidal quantum dots inserted into a subsurface laterally-extended GaN nano-porous structure in an InGaN/GaN quantum-well template

To improve the color conversion performance, we study the nanoscale-cavity effects on the emission efficiency of a colloidal quantum dot (QD) and the Förster resonance energy transfer (FRET) from quantum well (QW) into QD in a GaN porous structure (PS). For this study, we insert green-emitting QD (GQD) and red-emitting QD (RQD) into the fabricated PSs in a GaN template and a blue-emitting QW template, and investigate the behaviors of the photoluminescence (PL) decay times and the intensity ratios of blue, green, and red lights. In the PS samples fabricated on the GaN template, we observe the efficiency enhancements of QD emission and the FRET from GQD into RQD, when compared with the samples of surface QDs, which is attributed to the nanoscale-cavity effect. In the PS samples fabricated on the QW template, the FRET from QW into QD is also enhanced. The enhanced FRET and QD emission efficiencies in a PS result in an improved color conversion performance. Because of the anisotropic PS in the sample surface plane, the polarization dependencies of QD emission and FRET are observed.

Enhancing deep-UV emission at 234 nm by introducing a truncated pyramid AlN/GaN nanostructure with fine-tuned multiple facets

The external quantum efficiency of a high-Al content (>0.6) AlGaN deep-ultraviolet (DUV) light-emitting diode is typically below 1% in the sub-250 nm wavelength range. One of the main reasons for this low efficiency is the fundamental properties of high-Al content AlGaN comprising the transverse-magnetic (TM)-dominant emission and low light extraction due to the total internal reflection (TIR). This work demonstrates a truncated pyramid nanostructure with fine-tuned multiple facets in an (AlN)₈/(GaN)₂ digital alloy to achieve highly efficient DUV emission at 234 nm. By applying nanoimprint lithography, dry and wet etching, a hexagonal truncated pyramid nanohole structure is fabricated featuring multiple crystal facets of (0001), (10-13), and (20-21) planes. These fine-tuned multiple facets act as reflecting mirrors that can effectively modulate the light propagation and extraction patterns to overcome the TIR via multiple reflections and enhanced scattering. Consequently, significant light extraction enhancements of 5.6 times and 1.1 times for TM and transverse-electric emissions are achieved in the truncated pyramid nanohole structure, respectively. The total luminous intensity of this unique nanostructure is greatly increased by 191% compared to that of a conventional planar structure. The truncated pyramid AlN/GaN nanostructure with fine-tuned multiple facets used in this work provides a promising approach for realizing highly efficient sub-250 nm DUV light-emitting devices.

[Role of inducible costimulatory molecules (ICOS) and related cytokines in immune regulation of Echinococcus granulosus infections in mice]

OBJECTIVE

To investigate the roles of inducible costimulatory molecules (ICOS) and related cytokines in the immune regulation of Echinococcus granulosus infections in mice.

METHODS

Eighty BALB/c mice (weight 18-22 g) were divided into the control and infection groups, of 40 animals in each group. E. granulosus infection was modeled in mice by intraperitoneal injection of 10 000 protoscoleces per mouse. Serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) and peripheral interleukin-4 (IL-4) and IL-10 levels were measured 2, 8, 30, 60, 180 days post-infection. Mouse liver specimens were excised for hematoxylin-eosin (HE) staining and immunostaining, and ICOS expression was quantified in mouse liver specimens using quantitative real-time PCR (qPCR) assay.

RESULTS

There were no significant differences in serum ALT (F = 12.082, P < 0.05), AST (F = 6.347, P < 0.05) or ALP levels (F = 52.186, P < 0.05) in mice 2, 8, 30, 60 and 180 days post-infection with E. granulosus. The serum ALT levels were significantly higher in the infection group than in the control group 2 [(61.72 ± 9.89) vs. (50.65 ± 4.67)U/L, P < 0.05] and 30 days post-infection [(80.61 ± 23.71)vs.(67.75 ± 9.79)U/L, P < 0.05], and the serum ALT levels were significantly higher in the infection group than in the control group 2 [(181.06 ± 60.61) vs.(115.58 ± 17.66)U/L, P < 0.05] and 180 days post-infection [(137.84 ± 29.01) vs. (108.05 ± 10.33) U/L, P < 0.05], while greater serum ALP levels were measured in the infection group than in the control group 2 [(162.90 ± 21.04)vs.(64.54 ± 5.99)U/L, P < 0.05], 8[(176.36 ± 24.56) vs. (62.70 ± 9.21)U/L, P < 0.05] and 30 days post-infection [(138.86 ± 13.59) vs. (58.60 ± 5.28) U/L, P < 0.05]. A few inflammatory cells were seen in mouse liver in the infection group 30 days post-infection, and no apparent changes were found in the mouse hepatic structure 60 days post-infection. On day 180 post-infection, a large number of epithelium-like cells presented fibrotic growth in mouse liver in the cyst-infiltrating regions, with cuticula formation seen, and plenty of red cells were present in lesions and hepatocyte space. Positive ICOS expression was detected in mouse liver in the infection group, with ICOS-positive cells predominantly seen in the cytoplasm of the hepatocyte, and the ICOS expression increased over time. The relative ICOS mRNA expression was 2.732 ± 0.094 on day 180 post-infection, which was significantly greater than that on day 2 postinfection (0.746 ± 0.049). There were no significant differences in serum IL-4 or IL-10 levels at different time points after E. granulosus infections, while the serum IL-4 and IL-10 levels peaked in the infection group 180 days and 60 days post-infection, respectively. Higher serum IL-4 levels were measured in the infection group than in the control group 8 [(22.50 ± 3.24) vs. (5.82 ± 0.49) pg/mL, P < 0.05], 30 [(15.49 ± 4.73) vs. (5.10 ± 1.38) pg/mL, P < 0.05], 60 [(36.93 ± 6.14) vs. (4.13 ± 1.19) pg/mL, P < 0.05] and 180 days post-infection [(198.35 ± 0.70) vs. (4.19 ± 0.98) pg/mL, P < 0.05], and higher IL-10 levels were measured in the infection group than in the control group 2 [(4.84 ± 1.91) vs. (2.11 ± 1.03) pg/mL, P < 0.05], 8 [(44.72 ± 14.63) vs. (3.16 ± 0.60) pg/mL, P < 0.05], 30 [(25.47 ± 8.00) vs. (3.83 ± 1.87) pg/mL, P < 0.05], 60 [(187.16 ± 60.44) vs. (3.69 ± 1.05) pg/mL, P < 0.05] and 180 days post-infection [(85.40 ± 7.15) vs. (3.25 ± 0.93) pg/mL, P < 0.05].

CONCLUSIONS

High ICOS expression is present in the liver of mice with E. granulosus infections. The positive ICOS expression and immune activation levels increase with the time of E. granulosus infections, leading to aggravation of hepatocyte injury caused by inflammation.

Mesh size control in forming an Ag/AgO nano-network structure for transparent conducting application

The variation behaviors of the morphology, transmission, and sheet resistance of the surface Ag/AgO nano-network (NNW) structures fabricated under different illumination conditions and with different Ag deposition thicknesses and thermal annealing temperatures in forming initial Ag nanoparticles (NPs) are studied. Generally, an NNW structure with a smaller mesh size or a denser branch distribution has a lower transmission and a lower sheet resistance level. Under the fabrication condition of a broader illumination spectrum, a lower thermal annealing temperature, or a thicker Ag deposition, we can obtain an NNW structure of a smaller mesh size. The mesh size of an NNW structure is basically controlled by the seed density of Brownian tree (BT) at the beginning of light illumination. A BT seed can be formed through a stronger local localized surface plasmon resonance for accelerating Ag oxidation in a certain region. Once an Ag/AgO BT seed is formed, the surrounding Ag NPs are reorganized to form the branches of a BT. Multiple BTs are connected to form a large-area NNW structure, which can serve as a transparent conductor. Under the fabrication conditions of a broader illumination spectrum, 3 nm Ag deposition, and 100 °C thermal annealing, we can implement an NNW structure to achieve ∼1.15μm in mesh size, ∼90 Ω sq^-1in sheet resistance, and 93%-77% in transmittance within the wavelength range between 370 and 700 nm.

Surface plasmon coupling effects on the förster resonance energy transfer from quantum dot into rhodamine 6G

Rhodamine 6G (R6G) molecules linked CdZnSeS/ZnS green-emitting quantum dots (QDs) are self-assembled onto Ag nanoparticles (NPs) for studying the surface plasmon (SP) coupling effect on the Förster resonance energy transfer (FRET) process from QD into R6G. SP coupling can enhance the emission efficiency of QD such that FRET has to compete with QD emission for transferring energy into R6G. It is found that FRET efficiency is reduced under the SP coupling condition. Although R6G emission efficiency can also be enhanced through SP coupling when it is directly linked onto Ag NP, the enhancement decreases when R6G is linked onto QD and then the QD-R6G complex is self-assembled onto Ag NP. In particular, R6G emission efficiency can be reduced through SP coupling when the number of R6G molecules linked onto a QD is high. A rate-equation model is built for resembling the measured photoluminescence decay profiles and providing us with more detailed explanations for the observed FRET and SP coupling behaviors.

Combined effects of surface plasmon coupling and Förster resonance energy transfer on the light color conversion behaviors of colloidal quantum dots on an InGaN/GaN quantum-well nanodisk structure

By forming nanodisk (ND) structures on a blue-emitting InGaN/GaN quantum-well (QW) template, the QWs become close to the red-emitting quantum dots (QDs) and Ag nanoparticles (NPs) attached onto the sidewalls of the NDs such that Förster resonance energy transfer (FRET) and surface plasmon (SP) coupling can occur to enhance the efficiency of blue-to-red color conversion. With a larger ND height, more QWs are exposed to open air on the sidewall for more QD/Ag NP attachment through QD self-assembly and Ag NP drop casting such that the FRET and SP coupling effects, and hence the color conversion efficiency can be enhanced. A stronger FRET process leads to a longer QD photoluminescence (PL) decay time and a shorter QW PL decay time. It is shown that SP coupling can enhance the FRET efficiency.

Förster resonance energy transfer in surface plasmon coupled color conversion processes of colloidal quantum dots

Förster resonance energy transfer (FRET) from a green-emitting quantum dot (GQD) into a red-emitting quantum dot (RQD) is an important mechanism in a multiple-color conversion process, particularly under the surface plasmon (SP) coupling condition for enhancing color conversion efficiency. Here, the dependencies of FRET efficiency on the relative concentrations of GQD and RQD in their mixtures and their surface molecule coatings for controlling surface charges are studied. Also, the SP coupling effects induced by two kinds of Ag nanoparticles on the emission behaviors of GQD and RQD are demonstrated, particularly when FRET is involved in the coupling process. FRET efficiency is reduced under the SP coupling condition. SP coupling can enhance the color conversion efficiency of either GQD or RQD. The combination of SP coupling and FRET can be used for controlling the relative converted light intensities in a multiple-color conversion process.

Spatial range of the plasmonic Dicke effect in an InGaN/GaN multiple quantum well structure

The plasmonic Dicke effect means a cooperative emission mechanism of multiple light emitters when they are simultaneously coupled with the same surface plasmon (SP) mode of a metal nanostructure to achieve a higher collective emission efficiency. Here, we compare the enhancements of emission efficiency among a series of SP-coupled InGaN/GaN quantum-well (QW) structures of different QW period numbers to show an emission behavior consistent with the plasmonic Dicke effect. The relative enhancement of overall emission efficiency increases with QW period number until it reaches a critical value, beyond which the enhancement starts to decrease. This critical QW period number corresponds to the effective depth range of the plasmonic Dicke effect in a multiple-QW system. It also represents an optimized QW structure for maximizing the SP coupling effect. Internal quantum efficiency and time-resolved photoluminescence are measured for comparing the enhanced emission efficiencies of blue and green QW structures with different QW period numbers through SP coupling induced by surface Ag nanoparticles.

Important role of surface plasmon coupling with the quantum wells in a surface plasmon enhanced color-converting structure of colloidal quantum dots on quantum wells

To improve the color-conversion efficiency based on a quantum-well (QW) light-emitting diode (LED), a more energy-saving strategy is needed to increase the energy transfer efficiency from the electrical input power of the LED into the emission of over-coated color-converter, not just from LED emission into converted light. In this regard, the efficiency of energy transfer of any mechanism from LED QW into the color-converter is an important issue. By overlaying blue-emitting QW structures and GaN templates with both deposited metal nanoparticles (DMNPs) and color-converting quantum dot (QD) linked synthesized metal nanoparticles (SMNPs) of different localized surface plasmon (LSP) resonance wavelengths for producing multiple surface plasmon (SP) coupling mechanisms with the QW and QD, we study the enhancement variations of their internal quantum efficiencies and photoluminescence decay times. By comparing the QD emission efficiencies between the samples with and without QW, one can observe the advantageous effect of QW coupling with LSP resonances on QD emission efficiency. Also, with the LSP resonance wavelengths of both DMNPs and SMNPs close to the QW emission wavelength for producing strong SP coupling with the QW and hence QD absorption, a higher QD emission or color-conversion efficiency can be obtained.

Theoretical analysis of a white-light LED array based on a GaN nanorod structure

Based on the experimentally demonstrated In content distribution in the InGaN/GaN quantum wells on a two-section GaN nanorod (NR) sidewall, a white-light light-emitting diode (LED) without phosphor is designed and simulated. Following the dependencies of the In diffusion length and incorporation ratio on NR geometric variables of a theoretical model, the height, radius, and tapering section geometry of the GaN NR are designed for controlling the relative intensities of a blue and a yellow emission component to mix into white light. The higher-In upper section of the NR is first excited to emit a relatively stronger yellow component when injection current is low. As the injection current increases, more current spreads into the lower-In lower section, eventually leading to a stronger blue emission component. The proposed NR LED structure provides an alternative solution for phosphor-free white-light generation.

Emission behaviors of colloidal quantum dots linked onto synthesized metal nanoparticles

With two different residual surfactants, four different metal nanoparticles (NPs), including two Au NPs and two Ag NPs are synthesized for linking with red-emitting CdZnSeS/ZnS colloidal quantum dots (QDs) to enhance QD emission efficiency. Those metal NPs are first connected with amino polyethylene glycol thiol of different molecular weights to avoid aggregation and make them positively charged. They can attract negatively charged QDs for inducing surface plasmon (SP) coupling such that either QD absorption or emission and hence overall color conversion efficiency can be enhanced. The enhancement of QD emission efficiency is evaluated through the comparison of time-resolved photoluminescence behaviors under different QD linkage conditions. Such results are confirmed by the measurement of the emission quantum efficiency of QD. It is found that by linking QDs onto Ag NPs, the QD emission efficiency is more enhanced, when compared with Au NPs. Also, depending on the synthesis process, the residual surfactant of citrate leads to a relatively large increment in QD emission efficiency, when compared to the surfactant of cetrimonium chloride. A more enhanced QD emission efficiency is caused by a higher QD linkage capability and a stronger SP coupling effect.

NiS2 nanoparticles anchored on open carbon nanohelmets as an advanced anode for lithium-ion batteries

Low intrinsic conductivity and large volume expansion seriously restrict the efficient lithium storage performance of metal sulfides. Here, we fabricate a hybrid material of NiS₂ nanoparticles/carbon nanohelmets (NiS₂/CNHs) to address the above issues. As an anode material in lithium-ion batteries, NiS₂/CNHs exhibit excellent cycling stability (490 mA h g^-1 after 3000 cycles at 5 A g^-1) and rate properties (412 mA h g^-1 at 10 A g^-1), outperforming other NiS _x -based anode materials. These remarkable performances originate from the three-dimensional helmet-like integrated architecture of NiS₂/CNHs, which reduces the electrode resistance due to the tight combination between NiS₂ and CNHs, provides efficient diffusion paths for the electrolyte and Li⁺ owing to the amorphous nanoporous carbon structure, and significantly mitigates the aggregation and buffers the large volumetric expansion of NiS₂ nanoparticles upon long-term cycling thanks to the open three-dimensional architecture and well-dispersed NiS₂ nanoparticles on it.

Color conversion efficiency enhancement of colloidal quantum dot through its linkage with synthesized metal nanoparticle on a blue light-emitting diode

Four surface-modified and, hence, positively charged metal nanoparticles (NPs) of different localized surface plasmon (LSP) resonance wavelengths are synthesized for linking with negatively charged, red-emitting colloidal CdZnSeS/ZnS quantum dots (QDs) on the top surface of a blue-emitting InGaN/GaN quantum well (QW) light-emitting diode (LED) through electro-static force. The metal NP-QD linkage leads to a short distance between them for producing their strong surface plasmon (SP) coupling, such that QD absorption and emission can be enhanced. Meanwhile, the small p-GaN thickness in the LED results in strong SP coupling between the LSP resonance of metal NP and the QWs of the LED, leading to enhanced QW emission and, hence, stronger QD excitation. All those factors together result in the increase of the color conversion efficiency of the QD.

A prospective randomized trial examining the use of a closed suction drain shows no influence on strength or function in primary total knee arthroplasty

Aims

The aim of this study was to determine whether closed suction drain (CSD) use influences recovery of quadriceps strength and to examine the effects of drain use on secondary outcomes: quadriceps activation, intra-articular effusion, bioelectrical measure of swelling, range of movement (ROM), pain, and wound healing complications.

Patients and Methods

A total of 29 patients undergoing simultaneous bilateral total knee arthroplasty (TKA) were enrolled in a prospective, randomized blinded study. Patients were randomized to receive a CSD in one limb while the contralateral limb had the use of a subcutaneous drain (SCDRN) without the use of suction (‘sham drain’). Isometric quadriceps strength was collected as the primary outcome. Secondary outcomes consisted of quadriceps activation, intra-articular effusion measured via ultrasound, lower limb swelling measured with bioelectrical impendence and limb girth, knee ROM, and pain. Outcomes were assessed preoperatively and postoperatively at day two, two and six weeks, and three months. Differences between limbs were determined using paired Student’s t-tests or Wilcoxon’s signed-rank tests.

Results

No significant differences were identified between limbs prior to surgery for the primary or secondary outcomes. No significant differences in quadriceps strength were seen between CSD and SCDRN limbs at postoperative day two (p = 0.09), two weeks (primary endpoint) (p = 0.7), six weeks (p = 0.3), or three months (p = 0.5). The secondary outcome of knee extension ROM was significantly greater in the CSD limb compared with the SCDRN (p = 0.01) at two weeks following surgery, but this difference was absent at all other intervals. Secondary outcomes of quadriceps activation, intra-articular effusion, lower limb swelling, and pain were not found to differ significantly at any timepoint following surgery.

Conclusion

The use of CSD during TKA did not influence quadriceps strength, quadriceps activation, intra-articular effusion, lower limb swelling, ROM, or pain. These results have limited drain use by the authors in primary uncomplicated TKA. Cite this article: Bone Joint J 2019;101-B (7 Supple C):84–90

Simulation study on light color conversion enhancement through surface plasmon coupling

A theoretical model together with a numerical algorithm of surface plasmon (SP) coupling are built for simulating SP-enhanced light color conversion from a shorter-wavelength radiating dipole (representing a quantum well - QW) into a longer-wavelength one (representing a quantum dot - QD) through QD absorption at the shorter wavelength. An Ag nanoparticle (NP) located between the two dipoles is designed for producing strong SP couplings simultaneously at the two wavelengths. At the QW emission wavelength, SP couplings with the QW and QD dipoles lead to the energy transfer from the QW into the QD and hence the absorption enhancement of the QD. At the QD emission wavelength, SP coupling with the excited QD dipole results in the enhancement of QD emission efficiency. The combination of the SP-induced effects at the two wavelengths leads to the increase of overall color conversion efficiency. The color conversion efficiencies in using Ag NPs of different geometries or SP resonance behaviors for producing different QD absorption and emission enhancement levels are compared.

[Regulation mechanism of E2F1 transcription factor on M2 macrophages in full-thickness skin defect wounds of mice]

Objective: To explore the regulatory mechanism of E2F1 transcription factor on M2 macrophages in full-thickness skin defect wounds of mice. Methods: E2F1 gene knockout heterozygotes C57BL/6 mice and wild-type C57BL/6 mice were introduced and self-reproduced. Two weeks after birth, E2F1 gene knockout homozygotes mice and wild-type mice were identified by polymerase chain reaction (PCR). Twelve identified 6-8 weeks old male E2F1 gene knockout homozygotes C57BL/6 mice and wild-type C57BL/6 mice were selected respectively according to the random number table and set as E2F1 gene knockout group and wild-type group. A full-thickness skin defect wound was made on the back of each mouse. On post injury day (PID) 2 and 7, 6 mice in each group were selected according to the random number table and sacrificed, and the wound tissue was excised. The expression of CD68 and CD206 double positive M2 macrophages was observed by immunofluorescence method, and the percentage of CD206 positive cells was calculated. The protein expression of CD206 was detected by Western blotting. The mRNA expression of arginase 1 was detected by real-time fluorescent quantitative reverse transcription PCR (RT-PCR). Wound tissue specimens of the two groups on PID 7 were obtained, and the protein and mRNA expressions of peroxisome proliferator-activated receptor gamma (PPAR-γ) were detected by Western blotting and real-time fluorescent quantitative RT-PCR respectively. The above-mentioned experiments were repeated four times. Three specimens of wound tissue of mice in wild-type group on PID 7 were obtained to detect the relationship between E2F1 and PPAR-γ by co-immunoprecipitation and Western blotting, and this experiment was repeated two times. Data were processed with unpaired t test. Results: The size of PCR products of E2F1 gene knockout homozygotes C57BL/6 mice and wild-type C57BL/6 mice were 227 and 172 bp respectively, which were the same as those of the designed DNA fragments. On PID 2 and 7, the number of CD68 and CD206 double positive M2 macrophages in the wound tissue of mice in E2F1 gene knockout group was more than that of wild-type group, and the percentages of CD206 positive cells in the wound tissue of mice in E2F1 gene knockout group were (0.234±0.032)% and (0.584±0.023)% respectively, which were significantly higher than (0.129±0.017)% and (0.282±0.071)% of wild-type group (t=3.29, 3.54, P<0.05). On PID 2 and 7, the protein expression of CD206 in the wound tissue of mice in E2F1 gene knockout group were 1.00±0.23 and 1.63±0.26 respectively, which were significantly higher than 0.43±0.06 and 0.97±0.08 of wild-type group (t=2.41, 2.45, P<0.05). On PID 2 and 7, the mRNA expressions of arginase 1 in the wound tissue of mice in E2F1 gene knockout group were 0.482±0.105 and 0.195±0.031 respectively, which were significantly higher than 0.163±0.026 and 0.108±0.017 of wild-type group (t=3.04, 2.86, P<0.05). On PID 7, the protein and mRNA expressions of PPAR-γ in the wound tissue of mice in E2F1 gene knockout group were 0.61±0.12 and 0.51±0.13 respectively, which were significantly higher than 0.20±0.04 and 0.20±0.04 of wild-type group (t=3.36, 2.86, P<0.05). On PID 7, detection of the wound tissue of mice in wild-type group showed that PPAR-γ had unidirectional effect on E2F1. Conclusions: E2F1 transcription factor affects the polarization of M2 macrophages by inhibiting the expression of PPAR-γ, thereby inhibiting the healing process of full-thickness skin defect wounds in mice.

Control of pore structure in a porous gold nanoparticle for effective cancer cell damage

For tumor treatment, compared with gold nanoparticles (NPs) of other geometries, a porous gold NP (PGNP) has the advantages of stronger localized surface plasmon resonance (LSPR) due to the pore nanostructures and a larger surface area to link with more drug or photosensitizer (PS) molecules for more effective delivery into cancer cells. Different from the chemical synthesis methods, in this paper we demonstrate the fabrication procedures of PGNP based on shaped Au/Ag deposition on a Si substrate and elucidate the advantageous features. PGNPs fabricated under different conditions, including different deposited Au/Ag content ratios and different alloying annealing temperatures, are compared for optimizing the fabrication condition in terms of LSPR wavelength, PS linkage capability, and cancer cell damage efficiency. It is found that within the feasible fabrication parameter ranges, the Au/Ag content ratio of 3:7 and alloying annealing temperature at 600 °C are the optimized conditions. In comparing with widely used gold NPs of other geometries, PGNP fabricated under the optimized conditions can be used for achieving a significantly higher linked PS molecule number per unit gold weight.

Polarity Control in Growing Highly Ga-Doped ZnO Nanowires with the Vapor-Liquid-Solid Process

Surface behavior modification by forming surface-transparent conductive nanowires (NWs) is an important technique for many applications, particularly when the polarities of the NWs can be controlled. The polarities of Ga-doped ZnO (GaZnO) NWs grown on templates of different polarities under different growth conditions are studied for exploring a polarity control growth technique. The NWs are formed on Ga- and N-face GaN through the vapor-liquid-solid (VLS) process using Ag nanoparticles as growth catalyst. The NWs grown on templates of different polarities under the Zn- (O-) rich conditions are always Zn (O) polar. During the early stage of NW growth, because the lattice sizes among different nucleation islands formed at the triple-phase line are quite different, high-density planar defects are produced when lateral growths from multiple nucleation islands form a GaZnO double bilayer. In this situation, frequent domain inversions occur, and GaZnO polarity is unstable. Under the Zn- (O-) rich conditions, because the lateral growth rate of GaZnO in the Zn- (O-) polar structure is higher due to more available dangling bonds, the growth of the Zn- (O-) polar structure dominates NW formation such that the NW eventually becomes Zn (O) polar irrespective of the polarity of the growth template. Therefore, the polarity of a doped-ZnO NW can be controlled simply by the relative supply rates of Zn and O during VLS growth.

Further emission efficiency improvement of a commercial-quality light-emitting diode through surface plasmon coupling

It is usually believed that surface plasmon (SP) coupling is practically useful only for improving the performance of a light-emitting diode (LED) with a low intrinsic internal quantum efficiency (IQE). In this Letter, we demonstrate that the performance of a commercial-quality blue LED with a high IQE (>80%) can still be significantly improved through SP coupling based on a surface Ag nanoparticle (NP) structure. The performance improvement of such an LED is achieved by increasing the Mg doping concentration in its p-AlGaN electron blocking layer to enhance the hole injection efficiency such that the p-GaN layer thickness can be significantly reduced without sacrificing its electrical property. In this situation, the distance between surface Ag NPs and quantum wells is decreased and hence SP coupling strength is increased. By reducing the distance between the surface Ag NPs and the top quantum well to 66 nm, the IQE can be increased to almost 90% (an ∼11% enhancement) and the electroluminescence intensity can be enhanced by ∼24%.

Efficiency enhancement of light color conversion through surface plasmon coupling

The efficiency enhancement of light color conversion from blue quantum well (QW) emission into red quantum dot (QD) emission through surface plasmon (SP) coupling by coating CdSe/ZnS QDs on the top of an InGaN/GaN QW light-emitting diode (LED) is demonstrated. Ag nanoparticles (NPs) are fabricated within a transparent conductive Ga-doped ZnO interlayer to induce localized surface plasmon (LSP) resonance for simultaneously coupling with the QWs and QDs. Such a coupling process generates three enhancement effects, including QW emission, QD absorption at the QW emission wavelength, and QD emission, leading to an overall enhancement effect of QD emission intensity. An Ag NP geometry for inducing an LSP resonance peak around the middle between the QW and QD emission wavelengths results in the optimized condition for maximizing QD emission enhancement. Internal quantum efficiency and photoluminescence (PL) decay time measurements are performed to show consistent results with LED performance characterizations, even though the QD absorption of PL excitation laser may mix with the SP-induced QD absorption enhancement effect in PL measurement.

Exocytosis of gold nanoparticle and photosensitizer from cancer cells and their effects on photodynamic and photothermal processes

We first illustrate the faster decrease of the photothermal (PT) effect with the delay time of laser treatment, in which the illumination of a 1064 nm laser effectively excites the localized surface plasmon (LSP) resonance of cell-up-taken gold nanoring (NRI) linked with a photosensitizer (PS), when compared with the photodynamic (PD) effect produced by the illumination of a 660 nm laser for effective PS excitation. The measurement results of the metal contents of Au NRI and PS based on inductively coupled plasma mass spectroscopy and the PS fluorescence intensity based on flow cytometry show that the linkage of NRI and PS is rapidly broken for releasing PS through the effect of glutathione in lysosome after cell uptake. Meanwhile, NRI escapes from a cell with a high rate such that the PT effect decays fast while the released PS can stay inside a cell longer for producing a prolonged PD effect. The effective delivery of PS through the linkage with Au NRI for cell uptake and the advantageous effect of LSP resonance at a PS absorption wavelength on the PD process are also demonstrated.

Coupling of a light-emitting diode with surface plasmon polariton or localized surface plasmon induced on surface silver gratings of different geometries

A metal grating on top of a light-emitting diode (LED) with a designed grating period for compensating the momentum mismatch can enhance the surface plasmon polariton (SPP) coupling effect with the quantum wells (QWs) to improve LED performance. Here, we demonstrate the experimental results showing that the induced localized surface plasmon (LSP) resonance on such a metal grating can dominate the QW coupling effect for improving LED performance, particularly when grating ridge height is large. The finding is illustrated by fabricating Ag gratings on single-QW, green-emitting LEDs of different p-type thicknesses with varied grating ridge height and width such that the distance between the grating ridge tip and the QW can be controlled. Reflection spectra of the Ag grating structures are measured and simulated to identify the SPP or LSP resonance behaviors at the QW emission wavelength. The measured results of LED performances show that in the LED samples under study, both SPP and LSP couplings can lead to significant enhancements of internal quantum efficiency and electroluminescence intensity. At the designated QW emission wavelength, with a grating period theoretically designed for momentum matching, the LSP coupling effect is stronger, when compared with SPP coupling.

Different surface plasmon coupling behaviors of a surface Al nanoparticle between TE and TM polarizations in a deep-UV light-emitting diode

The formulations and numerical algorithms of a three-level model for studying the Purcell effect produced by the scattering of an air/AlGaN interface and the surface plasmon (SP) coupling effect induced by a surface Al nanoparticle in a two-polarization emission system to simulate the transverse-electric- (TE-) and transverse-magnetic- (TM-) polarized emissions in an Al_xGa_1-xN/Al_yGa_1-yN (y > x) quantum well (QW) are built. In reasonably selected ranges of Al content for an AlGaN QW to emit deep-ultraviolet (UV) light, the enhancement (suppression) of TE- (TM-) polarized emission is mainly caused by the SP-coupling (interface-scattering) effect. Different from a two two-level model, in the three-level model the TE- and TM-polarized emissions compete for electron in the shared upper state, which is used for simulating the conduction band, such that either interface-scattering or SP-coupling effect becomes weaker. In a quite large range of emission wavelength, in which the intrinsic emission is dominated by TM polarization, with the interface-scattering and SP-coupling effects, the TE-polarized emission becomes dominant for enhancing the light extraction efficiency of a deep-UV light-emitting diode.

Method for enhancing the favored transverse-electric-polarized emission of an AlGaN deep-ultraviolet quantum well

An AlGaN quantum well (QW) structure of a deep-ultraviolet (UV) light-emitting diode (LED) needs to be well designed for controlling its band structure such that the heavy-hole (HH) band edge becomes lower than the split-off (SO) band edge and hence the transverse-electric (TE) polarization dominates the emission for achieving a higher light extraction efficiency. Here, we report the discovery of un-intentionally formed high-Al AlGaN nano-layers right above and below such a QW and their effects on the QW for changing the relative energy levels of the HH and SO bands. The comparison between the results of simulation study and polarization-resolved photoluminescence measurement confirms that the high-Al layers (HALs) represent the key to the observation of the dominating TE-polarized emission. By applying a stress onto a sample along its c-axis to produce a tensile strain in the c-plane for counteracting the HAL effects in changing the band structure, we can further understand the effectiveness of the HALs. The formation of the HALs is attributed to the hydrogen back-etching of Ga atoms during the temperature transition from quantum barrier growth into QW growth and vice versa. The Al filling in the etched vacancies results in the formation of an HAL. This discovery brings us with a simple method for enhancing the favored TE-polarized emission in an AlGaN deep-UV QW LED.

Dependencies of surface plasmon coupling effects on the p-GaN thickness of a thin-p-type light-emitting diode

The high performance of a light-emitting diode (LED) with the total p-type thickness as small as 38 nm is demonstrated. By increasing the Mg doping concentration in the p-AlGaN electron blocking layer through an Mg pre-flow process, the hole injection efficiency can be significantly enhanced. Based on this technique, the high LED performance can be maintained when the p-type layer thickness is significantly reduced. Then, the surface plasmon coupling effects, including the enhancement of internal quantum efficiency, increase in output intensity, reduction of efficiency droop, and increase of modulation bandwidth, among the thin p-type LED samples of different p-type thicknesses that are compared. These advantageous effects are stronger as the p-type layer becomes thinner. However, the dependencies of these effects on p-type layer thickness are different. With a circular mesa size of 10 μm in radius, through surface plasmon coupling, we achieve the record-high modulation bandwidth of 625.6 MHz among c-plane GaN-based LEDs.

Cancer cell death pathways caused by photothermal and photodynamic effects through gold nanoring induced surface plasmon resonance

The different death pathways of cancer cells under the conditions of the photothermal (PT), effect, photodynamic (PD) effect, and their combination are evaluated. By incubating cells with Au nanoring (NRI) either linked with the photosensitizer, AlPcS, or not, the illumination of a visible continuous laser for exciting the photosensitizer or an infrared femtosecond laser for exciting the localized surface plasmon resonance of Au NRI, leads to various PT and PD conditions for study. Three different staining dyes are used for identifying the cell areas of different damage conditions at different temporal points of observation. The cell death pathways and apoptotic evolution speeds under different cell treatment conditions are evaluated based on the calibration of the threshold laser fluences for causing early-apoptosis (EA) and necrosis (NE) or late-apoptosis (LA). It is found that with the PT effect only, strong cell NE is generated and the transition from EA into LA is faster than that caused by the PD effect when the EA stage is reached within 0.5 h after laser illumination. By combining the PT and PD effects, in the first few hours, the transition speed becomes lower, compared to the case of the PT effect only, when both Au NRIs internalized into cells and adsorbed on cell membrane exist. When the Au NRIs on cell membrane is removed, in the first few hours, the transition speed becomes higher, compared to the case of the PD effect only.

Strategic Motives Drive Proposers to Offer Fairly in Ultimatum Games: An fMRI Study

The hypothesis of strategic motives postulates that offering fairly in the Ultimatum Game (UG) is to avoid rejection and receive money. In this fMRI study, we used a modified UG to elucidate how proposers reached decisions of offering fairly and to what extent they considered offering selfishly with different stakes. We had proposers choose between a fair and a selfish offer with different degrees of selfishness and stake sizes. Proposers were less likely and spent more time choosing the fair offer over a slightly-selfish offer than a very selfish offer independent of stakes. Such choices evoked greater activation in the dorsal anterior cingulate cortices that typically involve in allocation of cognitive control for cost/benefit decision making. Choosing a fair offer in higher stakes evoked greater activation in the anterior cingulate gyrus (ACCg) and the areas that previously have been implicated in reward and theory of mind. Furthermore, choosing a slightly selfish offer over a fair offer evoked greater activation in the anterior cingulate sulcus, ACCg, ventral tegmental area (or substantia nigra) and anterior insular cortex signalling the higher gain and implying higher rejection risk. In conclusion, our findings favoured the hypothesis that proposers offer fairly based on the strategic motives.

Structure variation of a sidewall quantum well on a GaN nanorod

A theoretical model for evaluating the height-dependent variations of quantum well (QW) thickness and In concentration in a sidewall QW of a single- or two-section GaN nanorod (NR) is proposed. By reasonably choosing modeling parameter values, the obtained numerical results are quite consistent with the available experimental data. In particular, the model clearly demonstrates the increasing trends of QW thickness and In concentration with height on a sidewall of a single-section NR. Also, it successfully explains the larger QW thickness and higher In concentration in the upper uniform section, when compared with the lower uniform section, in a two-section NR. In this model, three III-group adatom supply sources are considered for sidewall deposition on a single-section NR, including the downward diffusion of adatoms collected on the slant facets at the NR top, the upward diffusion of adatoms collected on the NR base, and the direct adsorption of atoms on the sidewall from the vapor phase. For a two-section NR, the upward and downward diffusions of adatoms collected on the slant facets of the tapering section between the two uniform sections serve as extra adatom supply sources.

Design of Hydrogen Storage Alloys/Nanoporous Metals Hybrid Electrodes for Nickel-Metal Hydride Batteries

Nickel metal hydride (Ni-MH) batteries have demonstrated key technology advantages for applications in new-energy vehicles, which play an important role in reducing greenhouse gas emissions and the world's dependence on fossil fuels. However, the poor high-rate dischargeability of the negative electrode materials-hydrogen storage alloys (HSAs) limits applications of Ni-MH batteries in high-power fields due to large polarization. Here we design a hybrid electrode by integrating HSAs with a current collector of three-dimensional bicontinuous nanoporous Ni. The electrode shows enhanced high-rate dischargeability with the capacity retention rate reaching 44.6% at a discharge current density of 3000 mA g(-1), which is 2.4 times that of bare HSAs (18.8%). Such a unique hybrid architecture not only enhances charge transfer between nanoporous Ni and HSAs, but also facilitates rapid diffusion of hydrogen atoms in HSAs. The developed HSAs/nanoporous metals hybrid structures exhibit great potential to be candidates as electrodes in high-performance Ni-MH batteries towards applications in new-energy vehicles.

[Effect of bariatric surgery on obstructive sleep apnea hypopnea syndrome with obesity in China]

Obesity has become one of the greatest public health concerns especially in China and obstructive sleep apnea-hypopnea syndrome (OSAHS) is prevalent among morbidly obese patients. Metabolic and bariatric surgery has been proved to be a typical multidisciplinary strategy for obese patients with OSAHS but no related bariatric surgical guideline for OSAHS was found by now. In this paper, we extend to share our preliminary single-center experiences in the multidisciplinary treatment of severe obese with OSAHS.

Combination of photothermal and photodynamic inactivation of cancer cells through surface plasmon resonance of a gold nanoring

We demonstrate effective inactivation of oral cancer cells SAS through a combination of photothermal therapy (PTT) and photodynamic therapy (PDT) effects based on localized surface plasmon resonance (LSPR) around 1064 nm in wavelength of a Au nanoring (NRI) under femtosecond (fs) laser illumination. The PTT effect is caused by the LSPR-enhanced absorption of the Au NRI. The PDT effect is generated by linking the Au NRI with the photosensitizer of sulfonated aluminum phthalocyanines (AlPcS) for producing singlet oxygen through the LSPR-enhanced two-photon absorption (TPA) excitation of AlPcS. The laser threshold intensity for cancer cell inactivation with the applied Au NRI linked with AlPcS is significantly lower when compared to that with the Au NRI not linked with AlPcS. The comparison of inactivation threshold intensity between the cases of fs and continuous laser illuminations at the same wavelength and with the same average power confirms the crucial factor of TPA under fs laser illumination for producing the PDT effect.

Interactions of acylated methylglucoside derivatives with CO2: simulation and calculations

Carbohydrates have drawn considerable interest from researchers recently due to their affinity for CO2. However, most of the research in this field has focused on peracetylated derivatives. Compared with acetylated carbohydrates, which have already been studied in depth, methyl D-glucopyranoside derivatives are more stable and could have additional applications. Thus, in the present work, ab initio calculations were performed to elucidate the characteristics of the interactions of methylglucoside derivatives with CO2, and to investigate how the binding energy (ΔE) is affected by isomerization or the introduction of various acyl groups. Four methyl D-glucopyranosides (each with two anomers) bearing acetyl, propionyl, butyryl, and isobutyryl moieties, respectively, were designed as substrates, and the 1:1 complexes of a CO2 molecule with each of these sugar substrates were modeled. The results indicate that ΔE is mainly influenced by interaction distance and the number of negatively charged donors or interacting pairs in the complex; the structure of the acyl group present in the substrate is a secondary influence. Except in the case of methyl 2-O-acetyl-D-glucopyranose, the ΔE values of the α- and β-anomers of each methylglucoside were found to be almost the same. Therefore, we would expect the CO2 affinities of the four derivatives studied here to be as strong as or even stronger than that of peracetylated D-glucopyranose. Graphical Abstract The binding energy between methyl D-glucopyranoside derivatives with various substituted acyl groups and CO2 are evaluated by ab initio calculations. The strong interaction between these methyl dglucopyranoside derivatives and CO2 showed the potential of their application for CO2 capture.

Regularly patterned multi-section GaN nanorod arrays grown with a pulsed growth technique

The growth of regularly patterned multi-section GaN nanorod (NR) arrays based on a pulsed growth technique with metalorganic chemical vapor deposition is demonstrated. Such an NR with multiple sections of different cross-sectional sizes is formed by tapering a uniform cross section to another through stepwise decreasing of the Ga supply duration to reduce the size of the catalytic Ga droplet. Contrast line structures are observed in either a scanning electron microscopy or transmission electron microscopy image of an NR. Such a contrast line-marker corresponds to a thin Ga-rich layer formed at the beginning of GaN precipitation of a pulsed growth cycle and illustrates the boundary between two successive growth cycles in pulsed growth. By analyzing the geometry variation of the contrast line-markers, the morphology evolution in the growth of a multi-section NR, including a tapering process, can be traced. Such a morphology variation is controlled by the size of the catalytic Ga droplet and its coverage range on the slant facets at the top of an NR. The comparison of emission spectra between single-, two-, and three-section GaN NRs with sidewall InGaN/GaN quantum wells indicates that a multi-section NR can lead to a significantly broader sidewall emission spectrum.

Multi-mechanism efficiency enhancement in growing Ga-doped ZnO as the transparent conductor on a light-emitting diode

The combined effects of a few mechanisms for emission efficiency enhancement produced in the overgrowth of the transparent conductor layer of Ga-doped ZnO (GaZnO) on a surface Ag-nanoparticle (NP) coated light-emitting diode (LED), including surface plasmon (SP) coupling, current spreading, light extraction, and contact resistivity reduction, are demonstrated. With a relatively higher GaZnO growth temperature (350 °C), melted Ag NPs can be used as catalyst for forming GaZnO nanoneedles (NNs) through the vapor-liquid-solid growth mode such that light extraction efficiency can be increased. Meanwhile, residual Ag NPs are buried in a simultaneously grown GaZnO layer for inducing SP coupling. With a relatively lower GaZnO growth temperature (250 °C), all the Ag NPs are preserved for generating a stronger SP coupling effect. By using a thin annealed GaZnO interlayer on p-GaN before Ag NP fabrication, the contact resistivity at the GaZnO/p-GaN interface and hence the overall device resistance can be reduced. Although the use of this interlayer blue-shifts the localized surface plasmon resonance peak of the fabricated Ag NPs from the quantum well emission wavelength of the current study (535 nm) such that the SP coupling effect becomes weaker, it is useful for enhancing the SP coupling effect in an LED with a shorter emission wavelength.

Evaluating the blue-shift behaviors of the surface plasmon coupling of an embedded light emitter with a surface Ag nanoparticle by adding a dielectric interlayer or coating

The surface plasmon (SP) coupling behaviors of an embedded light emitter or radiating dipole in GaN with a surface Ag nanoparticle (NP) in four structures of different added dielectric geometries, including an extended dielectric interlayer (DI) and a DI of a finite width between the Ag NP and GaN, a dielectric coating on the Ag NP, and no dielectric addition, are numerically compared. Either an added DI or dielectric coating can lead to the blue shift of localized surface plasmon (LSP) dipole resonance peak or the spectral peak of radiated power enhancement ratio with respect to that of the structure without dielectric addition. A smaller dielectric refractive-index or a larger dielectric thickness results in a larger blue-shift range. Under the condition of the same dielectric refractive-index and thickness, the structure of a DI with a finite width leads to the largest blue-shift range, followed by the structure of an extended DI and then the structure of a dielectric coating. In a practical application, for a given emission wavelength of a blue-emitting quantum well, the emission enhancement effect through SP coupling depends on the LSP resonance strength at this wavelength. Our study also shows that although the LSP resonance peak can be blue-shifted by reducing the size of a surface Ag NP, its SP coupling strength is dramatically reduced. Adding a DI or dielectric coating is a more practical approach for shifting the major LSP resonance mode of a surface Ag NP from the green into blue range.

Surface plasmon coupling for suppressing p-GaN absorption and TM-polarized emission in a deep-UV light-emitting diode

The radiated power enhancement (suppression) of an in- (out-of-) plane-oriented radiating dipole at a desired emission wavelength in the deep-ultraviolet (UV) range when it is coupled with a surface plasmon (SP) resonance mode induced on a nearby Al nanoparticle (NP) is demonstrated. Also, it is found that the enhanced radiated power propagates mainly in the direction from the Al NP toward the dipole. Such SP coupling behaviors can be used for suppressing the transverse-magnetic (TM)-polarized emission, enhancing the transverse-electric-polarized emission, and reducing the UV absorption of the p-GaN layer in an AlGaN-based deep-UV light-emitting diode by embedding a sphere-like Al NP in its p-AlGaN layer.

Multi-section core-shell InGaN/GaN quantum-well nanorod light-emitting diode array

The growth of a two-section, core-shell, InGaN/GaN quantum-well (QW) nanorod- (NR-) array light-emitting diode device based on a pulsed growth technique with metalorganic chemical vapor deposition is demonstrated. A two-section n-GaN NR is grown through a tapering process for forming two uniform NR sections of different cross-sectional sizes. The cathodoluminescence (CL), photoluminescence (PL), and electrolumines-cence (EL) characterization results of the two-section NR structure are compared with those of a single-section NR sample, which is prepared under the similar condition to that for the first uniform NR section of the two-section sample. All the CL, PL, and EL spectra of the two-section sample (peaked between 520 and 525 nm) are red-shifted from those of the single-section sample (peaked around 490 nm) by >30 nm in wavelength. Also, the emitted spectral widths of the two-section sample become significantly larger than their counterparts of the single-section sample. The PL spectral full-width at half-maximum increases from ~37 to ~61 nm. Such variations are attributed to the higher indium incorporation in the sidewall QWs of the two-section sample due to the stronger strain relaxation in an NR section of a smaller cross-sectional size and the more constituent atom supply from the larger gap volume between neighboring NRs.

Thermally induced variations of strain condition and emission behavior in flat and bendable light-emitting diodes on different substrates

The emission behaviors of four light-emitting diodes (LEDs) of different substrate structures, including a lateral LED grown on sapphire, a vertical LED wafer-bonded onto Si (111), a bendable LED Ag-epoxied onto a flat metal, and another bendable LED Ag-epoxied onto a metal of a curved surface, under different duty cycles of current injection are compared. Their different variation trends of emission behavior with injection duty cycle are attributed to the different thermally-induced strain conditions in the epitaxial layers, which are controlled by their substrate structures, in increasing injection duty cycle or current level. The results of Raman scattering measurements during LED operation show that a stronger tensile strain is generated under heating for reducing the quantum-confined Stark effect and hence increasing emission efficiency when the epitaxial layer is not tightly bonded onto a hard substrate. Such a behavior is particularly stronger when the epitaxial layer is bent.

Comparison of Axxent-Xoft, (192)Ir and (60)Co high-dose-rate brachytherapy sources for image-guided brachytherapy treatment planning for cervical cancer

OBJECTIVE

To evaluate the dosimetric differences and similarities between treatment plans generated with Axxent-Xoft electronic brachytherapy source (Xoft-EBS), (192)Ir and (60)Co for tandem and ovoids (T&O) applicators.

METHODS

In this retrospective study, we replanned 10 patients previously treated with (192)Ir high-dose-rate brachytherapy. Prescription was 7 Gy × 4 fractions to Point A. For each original plan, we created two additional plans with Xoft-EBS and (60)Co. The dose to each organ at risk (OAR) was evaluated in terms of V(35%) and V(50%), the percentage volume receiving 35% and 50% of the prescription dose, respectively, and D(2cc), highest dose to a 2 cm(3) volume of an OAR.

RESULTS

There was no difference between plans generated by (192)Ir and (60)Co, but the plans generated using Xoft-EBS showed a reduction of up to 50% in V(35%), V(50%) and D(2cc). The volumes of the 200% and 150% isodose lines, however, were 74% and 34% greater than the comparable volumes generated with the (192)Ir source. Point B dose was on average only 16% of the Point A dose for plans generated with Xoft-EBS compared with 30% for plans generated with (192)Ir or (60)Co.

CONCLUSION

The Xoft-EBS can potentially replace either (192)Ir or (60)Co in T&O treatments. Xoft-EBS offers either better sparing of the OARs compared with (192)Ir or (60)Co or at least similar sparing. Xoft-EBS-generated plans had higher doses within the target volume than (192)Ir- or (60)Co-generated ones.

ADVANCES IN KNOWLEDGE

This work presents newer knowledge in dosimetric comparison between Xoft-EBS, (192)Ir or (60)Co sources for T&O implants.

Growth of Highly Conductive Ga-Doped ZnO Nanoneedles

The molecular beam epitaxy growth of highly degenerate Ga-doped ZnO (GaZnO) nanoneedles (NNs) based on the vapor-liquid-solid (VLS) growth mode using Ag nanoparticles (NPs) as the growth catalyst is demonstrated. It is shown that when the growth substrate temperature is sufficiently high, a portion of a Ag NP can be melted for serving as the catalyst to precipitate GaZnO on the residual Ag NP and form a GaZnO NN. Record-low turn-on and threshold electric fields in the field emission test of the grown GaZnO NNs are observed. Also, a record-high field enhancement factor in field emission is calibrated. Such superior field emission performances are attributed to a few factors, including (1) the low work function and high conductivity of the grown GaZnO NNs due to highly degenerate Ga doping, (2) the sharp-pointed geometry of the vertically aligned GaZnO NNs, (3) the Ag doping in VLS precipitation of GaZnO for further reducing NN resistivity, and (4) the residual small Ag NP at the NN tip for making the tip even sharper and tip conductivity even higher.

Modulation behaviors of surface plasmon coupled light-emitting diode

The modulation bandwidths of the light-emitting diodes (LEDs) of different mesa sizes with and without surface plasmon (SP) coupling effect are compared. Due to the significant increase of carrier decay rate, within the size range of LED square-mesa from 60 through 300 micron and the injected current-density range from 139 through 1667 A/cm², the SP coupling can lead to the enhancement of modulation bandwidth by 44-48%, independent of the variations of LED mesa size or injected current level. The enhancement ratios of modulation bandwidth of the samples with SP coupling with respect to those of the samples without SP coupling are lower than the corresponding ratios of the square-root of photoluminescence decay rate due to the increases of their RC time constants (the product of device resistance and capacitance). The increases of the RC time constants in the samples with SP coupling are attributed to the increases of their device resistance levels when the Ag nanoparticles and GaZnO dielectric interlayer are added to the LED surface for effectively inducing SP coupling.

A new approach to construct bulk and size-dependent continuous binary solution phase diagrams of alloys

In this work, we report a new approach to construct both bulk and size-dependent continuous binary solution phase diagrams (e.g. the Au–Ag system) by combining ab initio molecular dynamics simulation and nanothermodynamics modeling.

Regularly patterned non-polar InGaN/GaN quantum-well nanorod light-emitting diode array

The growth and process of a regularly patterned nanorod (NR)- light-emitting diode (LED) array with its emission from sidewall non-polar quantum wells (QWs) are demonstrated. A pyramidal un-doped GaN structure is intentionally formed at the NR top for minimizing the current flow through this portion of the NR such that the injection current can be effectively guided to the sidewall m-plane InGaN/GaN QWs for emission excitation by a conformal transparent conductor (GaZnO). The injected current density at a given applied voltage of the NR LED device is similar to that of a planar c-plane or m-plane LED. The blue-shift trend of NR LED output spectrum with increasing injection current is caused by the non-uniform distributions of QW width and indium content along the height on a sidewall. The photoluminescence spectral shift under reversed bias confirms that the emission of the fabricated NR LED comes from non-polar QWs.

Extraordinary N atom tunneling in formation of InN shell layer on GaN nanorod m-plane sidewall

We report the extraordinary tunneling process that finds the lower cohesive energy route for stablizing InN shell layer on m-plane sidewall of GaN nanorod. The [0001] orientated GaN nanorod array is grown on sapphire substrate patterned with Ga nanoparticle by metal-organic vapor deposition method, based on which the simulation structures of c-plane top surface and m-plane sidewall surface is constructed for the first-principles calculations. The results show that the introduction of In wetting monolayer could effectively lower the cohesive energy of adalayers on non-polar GaN surfaces. Most importantly, it is revealed that there exists an extraordinary tunneling process in which the N atoms will drag out the In wetting atoms and tunnel through to form stable InN shell layer on the nanorod sidewall.

Phosphor-free, white-light LED under alternating-current operation

A light-emitting diode structure, consisting of a p-GaN layer, a CdZnO/ZnO quantum-well (QW) structure, a high-temperature-grown ZnO layer, and a GaZnO layer, is fabricated. Under forward bias, the device effectively emits green-yellow light, from the QW structure, at the rim of device mesa. Under reverse bias, electrons in the valence band of the p-GaN layer move into the conduction band of the GaZnO layer, through a QW-state-assisted tunneling process, to recombine with the injected holes in the GaZnO layer, for emitting yellow-red and shallow ultraviolet light over the entire mesa area. Also, carrier recombination in the p-GaN layer produces blue light. By properly designing the thickness of the high-temperature grown ZnO layer, the emission intensity under forward bias can be controlled such that, under alternating-current operation at 60 Hz, the spatial and spectral mixtures of the emitted lights of complementary colors, under forward and reverse biases, result in white light generation based on persistence of vision.