Excitation Intensity-Dependent Quantum Yield of Semiconductor Nanocrystals.

One of the key phenomena that determine the fluorescence of nanocrystals is the nonradiative Auger-Meitner recombination of excitons. This nonradiative rate affects the nanocrystals' fluorescence intensity, excited state lifetime, and quantum yield. Whereas most of the above properties can be directly measured, the quantum yield is the most difficult to assess. Here we place semiconductor nanocrystals inside a tunable plasmonic nanocavity with subwavelength spacing and modulate their radiative de-excitation rate by changing the cavity size. This allows us to determine absolute values of their fluorescence quantum yield under specific excitation conditions. Moreover, as expected considering the enhanced Auger-Meitner rate for higher multiple excited states, increasing the excitation rate reduces the quantum yield of the nanocrystals.

Excited state lifetime modulation in semiconductor nanocrystals for super-resolution imaging.

We report on proof of principle measurements of a concept for a super-resolution imaging method that is based on excitation field density-dependent lifetime modulation of semiconductor nanocrystals. The prerequisite of the technique is access to semiconductor nanocrystals with emission lifetimes that depend on the excitation intensity. Experimentally, the method requires a confocal microscope with fluorescence-lifetime measurement capability that makes it easily accessible to a broad optical imaging community. We demonstrate with single particle imaging that the method allows one to achieve a spatial resolution of the order of several tens of nanometers at moderate fluorescence excitation intensity.

Cervical lymph node metastasis in squamous cell carcinoma of the buccal mucosa: a retrospective study on pattern of involvement and clinical analysis

BACKGROUND: The study was performed with an aim to map the pattern of metastasis of squamous cell carcinomas of buccal mucosa to various cervical lymph node levels and analyze its correlation with primary tumor size and histo-pathological grading. MATERIAL AND METHODS: 254 patients with squamous cell carcinoma of the buccal mucosa treated with surgery first approach were analyzed retrospectively. The tumor size was noted from pre-operative CT Scans and were divided into early and advanced tumors. The resected specimen was studied to note the histo-pathological grading of the squamous cell carcinoma and the metastatic deposits at various lymph node levels. RESULTS: Out of 254 patients (149 females, 105 males), 145 patients showed histo-pathologically proven metastatic deposits in one or more lymph nodes out of which there were 56 patients showing occult metastasis. 78/145 patients showed metastatic involvement of level IB and/or IA lymph nodes, 31 showed involvement of level II and/or I lymph nodes, 27 showed involvement of level III with or without involvement of level I and II and 9 showed metastasis to level IV and V lymph nodes with or without level I, II or III dymph nodes. Cervical lymph node metastasis had statistically significant association with tumor size with advanced tumors showing worse pattern of metastatic spread beyond level I and II lymph nodes. As the degree of differentiation of squamous cell carcinoma reduced, they were more prone for cervical metastasis with moderately and poorly differentiated squamous cell carcinoma showing higher involvement of level III, IV and V lymph nodes. CONCLUSIONS: The majority of buccal mucosa cases showed metastasis to level I, II and III lymph nodes out of which level IB and/or IA was most frequently involved. Metastasis to level IV and V lymph nodes was rare and was seen especially in patients with advanced primary tumor and poor histo-pathologic differentiation

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Everlasting rhodamine dyes and true deciding factors in their STED microscopy performance.

The authors took an independent and closer look at the family of red-emitting rhodamine dyes known for a decade due to their excellent performance in STED microscopy. After the family was further extended, the true grounds of this performance became clear. Small-molecule protective agents and/or auxiliary groups were attached at two different sites of the dye's scaffold. Thus, a rhodamine core, which is already quite photostable as it is, and an intramolecular stabilizer - a 4-nitrobenzyl or a 4-nitrobenzylthio group were combined to give potentially "everlasting dyes". The fluorescence quantum yields (Φf) and the fluorescence lifetimes (τ) of the modified dyes were thoroughly measured with comparison to those of the parent dyes. The correlation of their STED performance with photostability and fluorescence color stability under illumination in water were explored. Unexpectedly, the anaerobic GSDIM (GOC) buffer proved unhelpful with respect to STED performance. It was demonstrated that, even dyes with a Φf of only 14-17% allow STED imaging with a sufficient photon budget and good signal-to-noise ratio. For the dyes with photostabilizing groups (PSG) the Φf values are 4-5 times lower than in the reference dyes, and lifetimes τ are also strongly reduced. Noteworthy are very high fluorescence color stability and constant or even increasing fluorescence signal under photobleaching in bulk aqueous solutions, which suggests a sacrificing role of the 4-nitrobenzyl-containing moieties. Straightforward and improved recipes for "last-minute" modifications and preparations of "self-healing" red-emitting fluorescent tags are described.

Emission States Variation of Single Graphene Quantum Dots.

Graphene quantum dots (GQDs) are nanoparticles that consist of a nanometer-sized core of graphene with diverse chemical groups on its boundary. Due to their advantageous properties, they are considered to be a promising material for optoelectronics, bioimaging, or photovoltaics. Despite considerable efforts that have been focused on unraveling the mechanism of their photoluminescence, many fundamental details are still unclear. Here, we report on a single-particle multimodal study that provides new insight into the photoluminescence properties of emission centers of GQDs in various local chemical environments. In particular, we show that the properties that are associated with emission centers of GQDs are significantly more sensitive to the structure of the particle itself than to a nonuniform local chemical environment. A better understanding of the dependence of GQDs' emission states on the complex local chemical environment is an important step toward finding new ways of controlling the optical properties of GQDs and of optimizing their use in various applications.

Incidence and risk factors for postoperative nausea and vomiting in orthognathic surgery: a 10-year retrospective study.

OBJECTIVES: Postoperative nausea and vomiting (PONV) is considered as one of the most incessant and anguishing factors for patients who have surgery under general anesthesia. The occurrence of PONV after orthognathic surgery can lead to dehydration, infection, bleeding at the surgical site, and patient discomfort, all of which leave a patient with a negative impression of anesthesia and surgery. The purpose of this study is to assess the incidence of PONV after orthognathic surgery and to correlate it with factors related to patient, anesthesia, and surgery. MATERIALS AND METHODS: A 10-year retrospective survey was done for patients who underwent orthognathic surgery between January 2008 and March 2018. The incidence of PONV was evaluated, correlations with factors related to patient, anesthesia, and surgery were studied, and the duration between the end of surgery and the occurrence of the first episode of PONV was tabulated. RESULTS: The medical records of 109 patients were screened, out of which 101 satisfied the inclusion criteria. Amongst these patients, 60 patients (59.4%) suffered from PONV. Patient's sex, induction agent used, intravenous fluids administered intraoperatively, duration and type of surgery, and the presence of a nasogastric tube were seen to have a significant influence on precipitating PONV. It was noted that among the patients who suffered from PONV, 61.7% of them experienced it 48-96 hours after the end of surgery. CONCLUSION: Despite the improved anesthetic equipments, drugs, and surgical techniques currently used, the incidence of PONV was high in our study. Certain factors that were seen to influence PONV in this study need to be considered in order to develop an efficacious protocol to reduce PONV in orthognathic surgeries.

Excitation and Emission Transition Dipoles of Type-II Semiconductor Nanorods.

The mechanisms of exciton generation and recombination in semiconductor nanocrystals are crucial to the understanding of their photophysics and for their application in nearly all fields. While many studies have been focused on type-I heterojunction nanocrystals, the photophysics of type-II nanorods, where the hole is located in the core and the electron is located in the shell of the nanorod, remain largely unexplored. In this work, by scanning single nanorods through the focal spot of radially and azimuthally polarized laser beams and by comparing the measured excitation patterns with a theoretical model, we determine the dimensionality of the excitation transition dipole of single type-II nanorods. Additionally, by recording defocused patterns of the emission of the same particles, we measure their emission transition dipoles. The combination of these techniques allows us to unambiguously deduce the dimensionality and orientation of both excitation and emission transition dipoles of single type-II semiconductor nanorods. The results show that in contrast to previously studied quantum emitters, the particles possess a 3D degenerate excitation and a fixed linear emission transition dipole.

Effect of structural evolution of ZnO/HfO2 nanocrystals on Eu2+/Eu3+ emission in glass-ceramic waveguides for photonic applications.

Eu-doped 70SiO2-23HfO2-7ZnO (mol%) glass-ceramic waveguides have been fabricated by sol-gel method as a function of heat-treatment temperatures for on-chip blue-light emitting source applications. Structural evolution of spherical ZnO and spherical as well as rod-like HfO2 nanocrystalline structures have been observed with heat-treatments at different temperatures. Initially, in the as-prepared samples at 900 ◦C, both, Eu2+ as well as Eu3+ ions are found to be present in the ternary matrix. With controlled heat-treatments of up to 1000 ◦C for 2 h, local environment of Eu-ions become more crystalline in nature and the reduction of Eu3+ to Eu2+ takes place in such ZnO/HfO2 crystalline environments. In these ternary glass-ceramic waveguides, heat-treated at higher temperatures, the blue-light emission characteristic, which is the signature of 4f 65d [Formula: see text] 4f 7 energy level transition of Eu2+ ions is found to be greatly enhanced. The as-prepared glass-ceramic waveguides exhibit a propagation loss of 0.4 ± 0.2 dB cm-1 at 632.8 nm. Though the propagation losses increase with the growth of nanocrystals, the added functionalities achieved in the optimally heat-treated Eu-doped 70SiO2-23HfO2-7ZnO (mol%) waveguides, make them a viable functional optical material for the fabrication of on-chip blue-light emitting sources for integrated optic applications.

Eu-doped ZnO-HfO2 hybrid nanocrystal-embedded low-loss glass-ceramic waveguides.

We report on the sol-gel fabrication, using a dip-coating technique, of low-loss Eu-doped 70SiO2 -[Formula: see text] HfO2-xZnO (x = 2, 5, 7 and 10 mol%) ternary glass-ceramic planar waveguides. Transmission electron microscopy and grazing incident x-ray diffraction experiments confirm the controlled growth of hybrid nanocrystals with an average size of 3 nm-25 nm, composed of ZnO encapsulated by a thin layer of nanocrystalline HfO2, with an increase of ZnO concentration from x = 2 mol% to 10 mol%  in the SiO2-HfO2 composite matrix. The effect of crystallization on the local environment of Eu ions, doped in the ZnO-HfO2 hybrid nanocrystal-embedded glass-ceramic matrix, is studied using photoluminescence spectra, wherein an intense mixed-valence state (divalent as well as trivalent) emission of Eu ions is observed. The existence of Eu(2+) and Eu(3+) in the SiO2-HfO2-ZnO ternary matrix is confirmed by x-ray photoelectron spectroscopy. Importantly, the Eu[Formula: see text]-doped ternary waveguides exhibit low propagation losses (0.3 ± 0.2 dB cm(-1) at 632.8 nm) and optical transparency in the visible region of the electromagnetic spectrum, which makes ZnO-HfO2 nanocrystal-embedded SiO2-HfO2-ZnO waveguides a viable candidate for the development of on-chip, active, integrated optical devices.

SNP in Chalcone Synthase gene is associated with variation of 6-gingerol content in contrasting landraces of Zingiber officinale.Roscoe.

Zingiber officinale, medicinally the most important species within Zingiber genus, contains 6-gingerol as the active principle. This compound obtained from rhizomes of Z.officinale, has immense medicinal importance and is used in various herbal drug formulations. Our record of variation in content of this active principle, viz. 6-gingerol, in land races of this drug plant collected from different locations correlated with our Gene expression studies exhibiting high Chalcone Synthase gene (Chalcone Synthase is the rate limiting enzyme of 6-gingerol biosynthesis pathway) expression in high 6-gingerol containing landraces than in the low 6-gingerol containing landraces. Sequencing of Chalcone Synthase cDNA and subsequent multiple sequence alignment revealed seven SNPs between these contrasting genotypes. Converting this nucleotide sequence to amino acid sequence, alteration of two amino acids becomes evident; one amino acid change (asparagine to serine at position 336) is associated with base change (A→G) and another change (serine to leucine at position 142) is associated with the base change (C→T). Since asparagine at position 336 is one of the critical amino acids of the catalytic triad of Chalcone Synthase enzyme, responsible for substrate binding, our study suggests that landraces with a specific amino acid change viz. Asparagine (found in high 6-gingerol containing landraces) to serine causes low 6-gingerol content. This is probably due to a weak enzyme substrate association caused by the absence of asparagine in the catalytic triad. Detailed study of this finding could also help to understand molecular mechanism associated with variation in 6-gingerol content in Z.officinale genotypes and thereby strategies for developing elite genotypes containing high 6-gingerol content.

Palonosetron and palonosetron plus dexamethasone to prevent postoperative nausea and vomiting in patients undergoing laparoscopic cholecystectomy: A prospective, randomized, double-blind comparative study.

BACKGROUND: Laparoscopic cholecystectomy (LC) is associated with a high risk of postoperative nausea and vomiting (PONV). Palonosetron is a newer 5HT3 receptor antagonist, which is routinely used in our institution to prevent PONV in patients scheduled for LC, under general anesthesia (GA). We formulated this study to find out whether the palonosetron and dexamethasone combination will be a better choice than palonosetron alone in the prevention of PONV. MATERIALS AND METHODS: Sixty American Society of Anesthesiologists (ASA) physical status I and II patients, scheduled for LC under GA, were randomized to receive either palonosetron or a combination of palonosetron and dexamethasone. The number of complete responders (no emesis, no requirement of rescue anti-emetic medication) and the four-point nausea score was recorded at 2, 6, 24, 48 h postoperatively and the data was analyzed statistically. RESULTS: The number of complete responders, as well as the nausea score, did not vary significantly (P=0.718) between the two groups over the 48-h postoperative period. CONCLUSIONS: The palonosetron and dexamethasone combination was not more effective than palonosetron alone in the prevention of PONV, in patients undergoing LC under GA.