Slow light nanocoatings for ultrashort pulse compression

Transparent materials do not absorb light but have profound influence on the phase evolution of transmitted radiation. One consequence is chromatic dispersion, i.e., light of different frequencies travels at different velocities, causing ultrashort laser pulses to elongate in time while propagating. Here we experimentally demonstrate ultrathin nanostructured coatings that resolve this challenge: we tailor the dispersion of silicon nanopillar arrays such that they temporally reshape pulses upon transmission using slow light effects and act as ultrashort laser pulse compressors. The coatings induce anomalous group delay dispersion in the visible to near-infrared spectral region around 800 nm wavelength over an 80 nm bandwidth. We characterize the arrays' performance in the spectral domain via white light interferometry and directly demonstrate the temporal compression of femtosecond laser pulses. Applying these coatings to conventional optics renders them ultrashort pulse compatible and suitable for a wide range of applications.

Unifying Frequency Combs in Active and Passive Cavities: Temporal Solitons in Externally Driven Ring Lasers

Frequency combs have become a prominent research area in optics. Of particular interest as integrated comb technology are chip-scale sources, such as semiconductor lasers and microresonators, which consist of resonators embedding a nonlinear medium either with or without population inversion. Such active and passive cavities were so far treated distinctly. Here we propose a formal unification by introducing a general equation that describes both types of cavities. The equation also captures the physics of a hybrid device-a semiconductor ring laser with an external optical drive-in which we show the existence of temporal solitons, previously identified only in microresonators, thanks to symmetry breaking and self-localization phenomena typical of spatially extended dissipative systems.

School-age dental screening: oral health and eating habits

AIM

the study has the purpose to evaluate the association between clinical data collected from dental screening carried out on children and their eating habits. Materials and methods: The dental screening was carried out on a sample of eight-year-old children attending the third grade of the elementary schools of Gaeta (Latina). Clinical data and periodontal status indexes were recorded. The descriptive statistics (mean, standard deviation, frequency) of all data were calculated and anova analysis and chi square test have been performed.

RESULTS

On the sample of 70 children the results showed an average of 1.4 decayed teeth per child (sd ± 2.3) with a slightly higher average in females. More than 68% of the sample had poor or insufficient oral hygiene conditions with plaque presence in 64% of cases. Moreover, 57% of children had class II malocclusion with increased overjet and oral breathing respectively in 37% and 30% of cases. Only 24% were breastfed in the first months of life and more than 40% maintained a bad habit for over two years of age. About eating habits, more than 80% of the sample consumed sweets or sweet drinks every day. The analysis of the data showed as children consume several snacks throughout the day, and 47% eat them watching TV.

CONCLUSIONS

The results of this study showed how prevention program carried out through the School is more effective on children for learning of content especially when the acquisition of knowledge follows the application and verification of theoretical and practical skills in terms of oral health.

Direct thermo-optical tuning of silicon microresonators for the mid-infrared

We use light from a visible laser diode to directly tune silicon-on-chip microresonators by thermo-optical effect. We show that this direct tuning is local, non invasive and has a much smaller time constant than global temperature tuning methods. Such an approach could prove to be highly effective for Kerr comb generation in microresonators pumped by quantum cascade lasers, which cannot be easily tuned to achieve comb generation and soliton-mode locked states.

Achromatic Metalens over 60 nm Bandwidth in the Visible and Metalens with Reverse Chromatic Dispersion

In this Letter, we experimentally report an achromatic metalens (AML) operating over a continuous bandwidth in the visible. This is accomplished via dispersion engineering of dielectric phase shifters: titanium dioxide nanopillars tiled on a dielectric spacer layer above a metallic mirror. The AML works in reflection mode with a focal length independent of wavelength from λ = 490 to 550 nm. We also design a metalens with reverse chromatic dispersion, where the focal length increases as the wavelength increases, contrary to conventional diffractive lenses. The ability to engineer the chromatic dispersion of metalenses at will enables a wide variety of applications that were not previously possible. In particular, for the AML design, we envision applications such as imaging under LED illumination, fluorescence, and photoluminescence spectroscopy.

Polarization-Insensitive Metalenses at Visible Wavelengths

In this Letter, we demonstrate highly efficient, polarization-insensitive planar lenses (metalenses) at red, green, and blue wavelengths (λ = 660, 532, and 405 nm). Metalenses with numerical apertures (NA) of 0.85 and 0.6 and corresponding efficiencies as high as 60% and 90% are achieved. These metalenses are less than 600 nm-thick and can focus incident light down to diffraction-limited spots as small as ∼0.64λ and provide high-resolution imaging. In addition, the focal spots are very symmetric with high Strehl ratios. The single step lithography and compatibility with large-scale fabrication processes make metalenses highly promising for widespread applications in imaging and spectroscopy.

Multispectral Chiral Imaging with a Metalens

The vast majority of biologically active compounds, ranging from amino acids to essential nutrients such as glucose, possess intrinsic handedness. This in turn gives rise to chiral optical properties that provide a basis for detecting and quantifying enantio-specific concentrations of these molecules. However, traditional chiroptical spectroscopy and imaging techniques require cascading of multiple optical components in sophisticated setups. Here, we present a planar lens with an engineered dispersive response, which simultaneously forms two images with opposite helicity of an object within the same field-of-view. In this way, chiroptical properties can be probed across the visible spectrum using only the lens and a camera without the addition of polarizers or dispersive optical devices. We map the circular dichroism of the exoskeleton of a chiral beetle, Chrysina gloriosa, which is known to exhibit high reflectivity of left-circularly polarized light, with high spatial resolution limited by the numerical aperture of the planar lens. Our results demonstrate the potential of metasurfaces in realizing a compact and multifunctional device with unprecedented imaging capabilities.

Super-Dispersive Off-Axis Meta-Lenses for Compact High Resolution Spectroscopy

Metasurfaces have opened a new frontier in the miniaturization of optical technology by allowing exceptional control over the wavefront. Here, we demonstrate off-axis meta-lenses that simultaneously focus and disperse light of different wavelengths with unprecedented spectral resolution. They are designed based on the geometric phase via rotated silicon nanofins and can focus light at angles as large as 80°. Due to the large angle focusing, these meta-lenses have superdispersive characteristics (0.27 nm/mrad) that make them capable of resolving wavelength differences as small as 200 pm in the telecom region. In addition, by stitching several meta-lenses together, we maintain a high spectral resolution for a wider wavelength range. The meta-lenses have measured efficiencies as high as 90% in the wavelength range of 1.1 to 1.6 μm. The planar and compact configuration together with high spectral resolution of these meta-lenses has significant potential for emerging portable/wearable optics technology.

Prokinetic effect of a standardized yarrow (Achillea millefolium) extract and its constituent choline: studies in the mouse and human stomach

BACKGROUND

Functional dyspepsia (FD) is a highly prevalent gastrointestinal disorder characterized by alterations in gastric motility. Yarrow (Achillea millefolium L., Fam Asteraceae) preparations are traditional remedies used to treat dyspeptic complaints. Herein, we investigated the effect of a standardized dry water extract obtained from A. millefolium flowering tops (AME) on gastric motility.

METHODS

The effect of AME on motility was evaluated on the resting tone of the isolated gastric antrum and on gastric emptying in vivo (phenol red meal method) both in control mice and in the model of cancer chemotherapy (cisplatin)-induced gastric abnormalities.

KEY RESULTS

The AME contracted mouse and human gastric strips and this action was unaffected by hexamethonium and tetrodotoxin, but strongly reduced by atropine. Among various chemical ingredients in yarrow, choline, but not the flavonoids rutin and apigenin, mimicked the action of AME. Furthermore, AME deprived of choline did not exert a contractile effect. In vivo, AME stimulated gastric emptying both in control and in cisplatin-treated mice, being more active in pathological states.

CONCLUSIONS & INFERENCES

It is concluded that (i) AME exerts a direct spasmogenic effect on gastric antrum; (ii) choline is the chemical ingredient responsible of such effect; (iii) the prokinetic effect of AME observed in vivo could provide the pharmacological basis underlying its traditional use in the treatment of dyspepsia.

Early childhood caries underweight or overweight, that is the question

AIM

The purpose of this retrospective case study is to describe the body mass index in a group of children, from 3 to 6 years old with ECC and a similar group of caries-free children.

MATERIALS AND METHODS

This case-control analysis involves two groups of children: the first was of 244 healthy children, 3 to 6 year-old and caries-free; the second was of 586 otherwise healthy children, same age, with Early Childhood Caries divided into three subgroups according the AAPD definition. Demographics, dmft, number teeth with pulpal involvement, BMI percentile, weight at birth, weight and height of both parents were measured during the clinical evaluation. Statistical analyses were performed using standard statistical software (SPSS Version 13). BMI distribution of the subjects with caries was graphically compared with the use of confidence intervals to a similar caries-free sample.

RESULTS

Results are expressed as mean ± SD and frequencies (percentages), depending on the data type. The distribution of BMI percentiles of the ECC group was: underweight = 10%; normal weight = 55.90%; at risk of overweight = 22.22 %; overweight = 11.11%. Significantly, more children in the case group were underweight than in the control group (10% vs. 4.94%).

CONCLUSION

The ECC population does not have a typical weight distribution, and the underweight finding in a significant number of Severe ECC (S-ECC) children may be due to the chewing alteration related to the dental pain due to caries and to missing teeth after hard tissues breakdown.

Inhibitory effects of bromelain, a cysteine protease derived from pineapple stem (Ananas comosus), on intestinal motility in mice

BACKGROUND

Bromelain (BR) is a cysteine protease with inhibitory effects on intestinal secretion and inflammation. However, its effects on intestinal motility are largely unexplored. Thus, we investigated the effect of this plant-derived compound on intestinal contractility and transit in mice.

METHODS

Contractility in vitro was evaluated by stimulating the mouse isolated ileum, in an organ bath, with acetylcholine, barium chloride, or electrical field stimulation. Motility in vivo was measured by evaluating the distribution of an orally administered fluorescent marker along the small intestine. Transit was also evaluated in pathophysiologic states induced by the pro-inflammatory compound croton oil or by the diabetogenic agent streptozotocin.

KEY RESULTS

Bromelain inhibited the contractions induced by different spasmogenic compounds in the mouse ileum with similar potency. The antispasmodic effect was reduced or counteracted by the proteolytic enzyme inhibitor, gabexate (15 × 10(-6)  mol L(-1) ), protease-activated receptor-2 (PAR-2) antagonist, N(1) -3-methylbutyryl-N(4) -6-aminohexanoyl-piperazine (10(-4) mol L(-1) ), phospholipase C (PLC) inhibitor, neomycin (3 × 10(-3) mol L(-1) ), and phosphodiesterase 4 (PDE4) inhibitor, rolipram (10(-6)  mol L(-1) ). In vivo, BR preferentially inhibited motility in pathophysiologic states in a PAR-2-antagonist-sensitive manner.

CONCLUSIONS & INFERENCES

Our data suggest that BR inhibits intestinal motility - preferentially in pathophysiologic conditions - with a mechanism possibly involving membrane PAR-2 and PLC and PDE4 as intracellular signals. Bromelain could be a lead compound for the development of new drugs, able to normalize the intestinal motility in inflammation and diabetes.

PAF formation by human gastrointestinal mucosa/submucosa in-vitro: release by ricinoleic acid, and inhibition by 5-aminosalicylic acid

Human isolated gastrointestinal mucosa/submucosa incubated with ricinoleic acid (12·5–100 μg mL−1) or the calcium ionophore A23187 (10 μg mL−1) released platelet-activating factor (PAF) as determined by a scintillation proximity assay after extraction and purification. 5-Aminosalicylic acid (25–100 μg mL−1) inhibited PAF release by ricinoleic acid in a concentration-dependent manner, and 50 μg mL−1 reduced the effect of A23187. We suggest that PAF may play a role in the taxation and mucosal damage by ricinoleic acid released from castor oil.

Time Course of PAF Formation by Gastrointestinal Tissue in Rats After Castor Oil Challenge

When castor oil was administered by gavage to rats, the duodenum and jejunum, but not the stomach, produced large amounts of platelet activating factor 3–7 h after oil challenge with a peak at 3 h. Intraluminal release of acid phosphatase was also markedly increased in the duodenum and jejunum of castor oil-treated rats, especially 3–5 h after oil challenge. No increase was observed in the stomach. There was a correlation between elevated release of acid phosphatase and intestinal hyperaemia.

Effects of senna and its active compounds rhein and rhein-anthrone on PAF formation by rat colon

A single or a prolonged oral administration of senna (60 mg kg−1) to rats did not increase either colonic PAF (platelet activating factor) content or intraluminal release of acid phosphatase. A similar result was observed in the colonic tissue of rats perfused in-vitro with rhein (1–300 μg mL−1) or rhein-anthrone (1–300 μg mL−1). A single or prolonged administration of castor oil (2 mL) to rats increased both colonic PAF content and intraluminal release of acid phosphatase. Colonic tissue of rats perfused in-vitro with calcium ionophore A23187 (1 and 10 μg mL−1) formed large amounts of PAF and acid phosphatase. Since PAF can mediate intestinal damage and acid phosphatase is a marker of cellular injury, we conclude that senna and its derivatives, rhein and rheinanthrone, are well tolerated in rats.

[Oral health and pregnancy: promotion of oral health during the pre-natal training in the Latina province]

The aim of this study, conducted in the Province of Latina, was to verify knowledge, attitudes, and lifestyles in relation to oral health in a sample of pregnant women, assessing their subjective perception of oral health, and highlight prenatal dental prevention need specialist in the area and provide adequate information on the importance of good oral hygiene in order to achieve a better health level both of the mother and the child. The study was conducted on a sample of pregnant women between the 26th and 39th gestational week, in the period from June to October 2009, during the childbirth training courses in the Province of Latina. Each patient was administered a questionnaire for the assessment of oral habits during pregnancy and for the definition of specific knowledge on and perception of themselves and their own oral condition. The survey shows that more than one third of the sample reported visiting a dentist only in case of pain, over half (56.9%) did not undergo any dental visit during the gestational period, only 24 subjects (33.3%) having applied to a dental hygienist for professional oral hygiene and that only 7 out of 72 women had been prescribed a dental checkup by a gynecologist. The study showed that knowledge about dental problems that may arise during pregnancy is insufficient to guarantee a good threshold to oral health care for the mother hence the need to promote information programs, oral health and pregnancy prevention and training in the territory mainly directed to health-care specialists (gynecologists and obstetricians) and to pregnant women.

Band-gap engineering: from physics and materials to new semiconductor devices

Band-gap engineering is a powerful technique for the design of new semiconductor materials and devices. Heterojunctions and modern growth techniques, such as molecular beam epitaxy, allow band diagrams with nearly arbitrary and continuous band-gap variations to be made. The transport properties of electrons and holes can be independently and continuously tuned for a given application. A new generation of devices with unique capabilities, ranging from solid-state photomultipliers to resonant tunneling transistors, is emerging from this approach.

Quantum cascade laser

A semiconductor injection laser that differs in a fundamental way from diode lasers has been demonstrated. It is built out of quantum semiconductor structures that were grown by molecular beam epitaxy and designed by band structure engineering. Electrons streaming down a potential staircase sequentially emit photons at the steps. The steps consist of coupled quantum wells in which population inversion between discrete conduction band excited states is achieved by control of tunneling. A strong narrowing of the emission spectrum, above threshold, provides direct evidence of laser action at a wavelength of 4.2 micrometers with peak powers in excess of 8 milliwatts in pulsed operation. In quantum cascade lasers, the wavelength, entirely determined by quantum confinement, can be tailored from the mid-infrared to the submillimeter wave region in the same heterostructure material.

Dynamics of actively mode-locked Quantum Cascade Lasers

The impact of upper state lifetime and spatial hole burning on pulse shape and stability in actively mode locked QCLs is investigated by numerical simulations. It is shown that an extended upper state lifetime is necessary to achieve stable isolated pulse formation per roundtrip. Spatial hole burning helps to reduce the pulse duration by supporting broadband multimode lasing, but introduces pulse instabilities which eventually lead to strongly structured pulse shapes that further degrade with increased pumping. At high pumping levels gain saturation and recovery between pulses leads to suppression of mode locking. In the absence of spatial hole burning the laser approaches single-mode lasing, while in the presence of spatial hole burning the mode locking becomes unstable and the laser dynamics does not reach a steady state anymore.

Klinefelter syndrome: Case report

OBJECTIVES.: The aim of this work is to describe the problems of child dentistry affected by Klinefelter's syndrome. METHODOS.: Through the presentation of a clinical case that was followed by a Pediatric Dentistry, University Sapienza of Rome. RESULT.: Interceptive therapy aims to eliminate the functional interference that occurs during growth. CONCLUSION.: For this reason it's a must for the dentist to carefully monitor the oral health of the small patient immediately.

Epitaxial Catalyst-Free Growth of InN Nanorods on c-Plane Sapphire

We report observation of catalyst-free hydride vapor phase epitaxy growth of InN nanorods. Characterization of the nanorods with transmission electron microscopy, and X-ray diffraction show that the nanorods are stoichiometric 2H-InN single crystals growing in the [0001] orientation. The InN rods are uniform, showing very little variation in both diameter and length. Surprisingly, the rods show clear epitaxial relations with the c-plane sapphire substrate, despite about 29% of lattice mismatch. Comparing catalyst-free with Ni-catalyzed growth, the only difference observed is in the density of nucleation sites, suggesting that Ni does not work like the typical vapor-liquid-solid catalyst, but rather functions as a nucleation promoter by catalyzing the decomposition of ammonia. No conclusive photoluminescence was observed from single nanorods, while integrating over a large area showed weak wide emissions centered at 0.78 and at 1.9 eV.