Nonlinear optical components for all-optical probabilistic graphical model.

The probabilistic graphical models (PGMs) are tools that are used to compute probability distributions over large and complex interacting variables. They have applications in social networks, speech recognition, artificial intelligence, machine learning, and many more areas. Here, we present an all-optical implementation of a PGM through the sum-product message passing algorithm (SPMPA) governed by a wavelength multiplexing architecture. As a proof-of-concept, we demonstrate the use of optics to solve a two node graphical model governed by SPMPA and successfully map the message passing algorithm onto photonics operations. The essential mathematical functions required for this algorithm, including multiplication and division, are implemented using nonlinear optics in thin film materials. The multiplication and division are demonstrated through a logarithm-summation-exponentiation operation and a pump-probe saturation process, respectively. The fundamental bottlenecks for the scalability of the presented scheme are discussed as well.

Remplissage Versus Modified Latarjet for Off-Track Hill-Sachs Lesions With Subcritical Glenoid Bone Loss.

BACKGROUND: Off-track Hill-Sachs lesions have been associated with high rates of recurrent shoulder instability. Both arthroscopic Bankart with remplissage and modified Latarjet have been described to treat off-track Hill-Sachs lesions. However, few comparative studies exist between the 2 techniques in heterogeneous populations. HYPOTHESIS: Remplissage would have similar recurrence rates and clinical outcomes to modified Latarjet for off-track Hill-Sachs lesions with subcritical glenoid bone loss. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Between 2005 and 2015, 189 patients with recurrent anterior shoulder instability, off-track Hill-Sachs lesion, and less than 25% glenoid bone loss were identified. Arthroscopic Bankart with remplissage (group A) was performed in 98 patients, and modified Latarjet (group B) was performed in 91 patients. Surgeries were performed by multiple fellowship-trained surgeons at 2 centers. The mean follow-up time was 3.2 years. Patients were assessed for their risk of recurrence using the Instability Severity Index Score and had preoperative 3-dimensional imaging to assess humeral and glenoid bone loss, along with measurement of the glenoid track. Single Assessment Numeric Evaluation (SANE), Western Ontario Shoulder Instability Index (WOSI), visual analog scale (VAS) for pain, range of motion, recurrence rate, subsequent procedures, and complications were analyzed. RESULTS: When comparing the remplissage and Latarjet groups, the remplissage group had a higher VAS pain score (2.2 vs 1.55, P = .041) and less internal rotation motion in abduction (40.9° vs 53.2°, P = .006). The complication rate was higher in the Latarjet group (12.1% vs 1%, P = .002). There was no difference between the 2 groups in patient-reported outcomes, such as WOSI and SANE. In addition, there was no difference between the 2 groups in revision rate and episodes of recurrent instability. In subgroup univariate analysis of revision patients, the remplissage group had higher VAS pain score (3.6 vs 2.2, P = .001), higher recurrence rate (34.8% vs 10.3%, P = .042), higher revision rate (43.5% vs 15.4%, P = .019), and lower complication rate (4.35% vs 28.2%, P = .024). For patients with >15% glenoid bone loss, Latarjet had lower recurrence rate (6.06% vs 28.6%, P = .034) and lower revision rate (3.03% vs 21.4%, P = .041). In collision and contact athletes, Latarjet had better WOSI scores (138 vs 231, P = .019) and lower recurrence rate (30% vs 0%, P = .005). In multivariate analysis, the odds of recurrence in the remplissage group were higher than in the Latarjet group in patients with previous instability surgery (3.56, P = .006), collision and contact athletes (2.37, P = .02), those with 10% to 15% glenoid bone loss (1.28, P = .04), and those with >15% glenoid bone loss (6.48, P = .001). CONCLUSION: For off-track Hill-Sachs lesions with subcritical glenoid bone loss, both the remplissage and modified Latarjet can achieve satisfactory results with the initial surgical intervention in the general population, but a higher complication rate was observed in the Latarjet group. However, Latarjet appears to be a better choice in patients with revision instability surgery, collision and contact athletes, and those with >10% glenoid bone loss.

Adhesion Enhancements and Surface-Enhanced Raman Scattering Activity of Ag and Ag@SiO2 Nanoparticle Decorated Ragweed Pollen Microparticle Sensor.

A simple solution processed layer-by-layer approach was used to immobilize metal nanoparticles (NPs) on the surface of ragweed pollen exine to obtain multifunctional particles with significant surface-enhanced Raman scattering (SERS), two-photon excited fluorescence, and enhanced adhesion properties. The rugged pollen exine was functionalized with an amine terminated silane and then treated with Ag or Ag@SiO2 NPs that were electrostatically attached to the exterior of the pollen by incubation in an NP solution of the appropriate pH. Nanoparticle agglomeration on the pollen gives rise to broadband near infrared (NIR) (785-1064 nm) plasmonic activity, and strong SERS signals from benzenedithiol deposited on NP-pollen composite particles were observed. In addition to SERS activity, the AgNP coating provides a twofold increase in the adhesive properties of the RW pollen exine on a silicon substrate, leading to a robust, adhesive, broadband NIR excitable SERS microparticle.

A Visible-Light-Active Heterojunction with Enhanced Photocatalytic Hydrogen Generation.

A visible-light-active carbon nitride (CN)/strontium pyroniobate (SNO) heterojunction photocatalyst was fabricated by deposition of CN over hydrothermally synthesized SNO nanoplates by a simple thermal decomposition process. The microscopic study revealed that nanosheets of CN were anchored to the surface of SNO resulting in an intimate contact between the two semiconductors. Diffuse reflectance UV/Vis spectra show that the resulting CN/SNO heterojunction possesses intense absorption in the visible region. The structural and spectral properties endowed the CN/SNO heterojunction with remarkably enhanced photocatalytic activity. Specifically, the photocatalytic hydrogen evolution rate per mole of CN was found to be 11 times higher for the CN/SNO composite compared to pristine CN. The results clearly show that the composite photocatalyst not only extends the light absorption range of SNO but also restricts photogenerated charge-carrier recombination, resulting in significant enhancement in photocatalytic activity compared to pristine CN. The relative band positions of the composite allow the photogenerated electrons in the conduction band of CN to migrate to that of SNO. This kind of charge migration and separation leads to the reduction in the overall recombination rate of photogenerated charge carriers, which is regarded as one of the key factors for the enhanced activity. A plausible mechanism for the enhanced photocatalytic activity of the heterostructured composite is proposed based on observed activity, photoluminescence, time-resolved fluorescence emission decay, electrochemical impedance spectroscopy, and band position calculations.

Three-dimensional organic microlasers with low lasing thresholds fabricated by multiphoton and UV lithography.

Cuboid-shaped organic microcavities containing a pyrromethene laser dye and supported upon a photonic crystal have been investigated as an approach to reducing the lasing threshold of the cavities. Multiphoton lithography facilitated fabrication of the cuboid cavities directly on the substrate or on the decoupling structure, while similar structures were fabricated on the substrate by UV lithography for comparison. Significant reduction of the lasing threshold by a factor of ~30 has been observed for cavities supported by the photonic crystal relative to those fabricated on the substrate. The lasing mode spectra of the cuboid microresonators provide strong evidence showing that the lasing modes are localized in the horizontal plane, with the shape of an inscribed diamond.

65 nm feature sizes using visible wavelength 3-D multiphoton lithography.

Nanoscale features as small as 65 +/- 5 nm have been formed reproducibly by using 520 nm femtosecond pulsed excitation of a 4,4'-bis(di-n-butylamino)biphenyl chromophore to initiate crosslinking in a triacrylate blend. Dosimetry studies of the photoinduced polymerization were performed on chromophores with sizable two-photon absorption cross-sections at 520 and 730 nm. These studies show that sub-diffraction limited line widths are obtained in both cases with the lines written at 520 nm being smaller. Three-dimensional multiphoton lithography at 520 nm has been used to fabricate polymeric woodpile photonic crystal structures that show stop bands in the near-infrared spectral region.

Highly efficient multiphoton-absorption-induced luminescence from gold nanoparticles.

We demonstrate that highly efficient photoluminescence is generated from gold nanoparticles as small as a few nanometers in diameter upon irradiation with sub-100-fs pulses of 790-nm light. Strong emission is observed at excitation intensities comparable to or less than those typically used for multiphoton imaging of fluorescently labeled biological samples. The particles have polarized emission, can radiate more efficiently than single molecules, do not exhibit significant blinking, and are photostable under hours of continuous excitation. These observations suggest that metal nanoparticles are a viable alternative to fluorophores or semiconductor nanoparticles for biological labeling and imaging.