Talbot effect in waveforms containing subwavelength multilobe superoscillations.

The self-imaging of periodic light patterns, also known as the Talbot effect, is usually limited to periods that are larger than the wavelength. Here we present, theoretically and experimentally, a method to overcome this limitation by using superoscillating light patterns. The input intensity distribution is a periodic band-limited function with relatively large periods, but it contains regions of multilobe periodic oscillations with periods that are smaller than half of the wavelength. We observe the revival of the input pattern, including the subwavelength superoscillating regions, at large distances of more than 40 times the optical wavelength. Moreover, at fractional Talbot distances, we observe even faster local oscillations, with periods of approximately one-third of the optical wavelength.

Multi-lobe superoscillation and its application to structured illumination microscopy.

Superoscillating function is a band-limited function that is locally oscillating faster than its highest Fourier component. In this work, we study and implement methods to generate multi-lobe optical superoscillating beams, with nearly constant intensity and constant local frequency. We generated superoscillating patterns having up to 12 sub-wavelength oscillations, with local frequency of 20% to 40% above the band-limit. We then test the potential application of these beams to super-resolution structured illumination microscopy. By utilizing the Moiré effect on a fluorescent grating, we have demonstrated experimentally resolution improvement over the conventional sinusoidal illumination. Our simulations show that structured illumination microscopy with super oscillating multi-lobe beams can provide more than twofold improvement in resolution, with respect to the classical diffraction limit and for coherent or incoherent modalities.

Observing the Quantum Wave Nature of Free Electrons through Spontaneous Emission.

We investigate, both experimentally and theoretically, the interpretation of the free-electron wave function using spontaneous emission. We use a transversely wide single-electron wave function to describe the spatial extent of transverse coherence of an electron beam in a standard transmission electron microscope. When the electron beam passes next to a metallic grating, spontaneous Smith-Purcell radiation is emitted. We then examine the effect of the electron wave function transversal size on the emitted radiation. Two interpretations widely used in the literature are considered: (1) radiation by a continuous current density attributed to the quantum probability current, equivalent to the spreading of the electron charge continuously over space; and (2) interpreting the square modulus of the wave function as a probability distribution of finding a point particle at a certain location, wherein the electron charge is always localized in space. We discuss how these two interpretations give contradictory predictions for the radiation pattern in our experiment, comparing the emission from narrow and wide wave functions with respect to the emitted radiation's wavelength. Matching our experiment with a new quantum-electrodynamics derivation, we conclude that the measurements can be explained by the probability distribution approach wherein the electron interacts with the grating as a classical point charge. Our findings clarify the transition between the classical and quantum regimes and shed light on the mechanisms that take part in general light-matter interactions.

Observation of linear plasmonic breathers and adiabatic elimination in a plasmonic multi-level coupled system.

We provide experimental and numerical demonstrations of plasmonic propagation dynamics in a multi-level coupled system, and present the first observation of plasmonic breathers propagating in such systems. The effect is observed both for the simplest symmetric case of a thin metal layer surrounded by two identical dielectrics, and also for a more complex system that includes five and more layers. By a careful choice of the permittivities and thicknesses of the intermediate layers, we can adiabatically eliminate the plasmonic waves in all the intermediate interfaces, thus enabling efficient vertical delivery and extraction of plasmonic signals between the top layer and deeply buried layers. The observation relies on controlling the excited mode by breaking the symmetry of excitation, which is crucial for obtaining the results experimentally. We also observe this breathing effect for transversely shaped plasmonic beams, with Hermite-Gauss, Airy and Weber wavefronts, that despite the oscillatory nature of propagation in such systems, still preserve all their unique wavefront properties. Finally, we show that such approaches can be extended to plasmonic propagation in a general multi-layered system, opening a path for efficient three-dimensional integrated plasmonic circuitry.

Super-Airy beam: self-accelerating beam with intensified main lobe.

We introduce, theoretically and experimentally, the concept of a diffraction-free "super-Airy" beam, in which the main lobe is reduced to nearly half in size with increased intensity in comparison to the main lobe of the optical Airy beam, while maintaining the same transverse acceleration. It is also observed that when the super-Airy main lobe is blocked during propagation, it recovers to the original size faster than the Airy main lobe.

Measurement of acceleration and orbital angular momentum of Airy beam and Airy-vortex beam by astigmatic transformation.

Special beams, including the Airy beam and the vortex-embedded Airy beam, draw much attention due to their unique features and promising applications. Therefore, it is necessary to devise a straightforward method for measuring these peculiar features of the beams with ease. Hence we present the astigmatic transformation of Airy and Airy-vortex beam. The "acceleration" coefficient of the Airy beam is directly determined from a single image by fitting the astigmatically transformed beam to an analytic expression. In addition, the orbital angular momentum of optical vortex in Airy-vortex beam is measured directly using a single image.

Unveiling the orbital angular momentum and acceleration of electron beams.

New forms of electron beams have been intensively investigated recently, including vortex beams carrying orbital angular momentum, as well as Airy beams propagating along a parabolic trajectory. Their traits may be harnessed for applications in materials science, electron microscopy, and interferometry, and so it is important to measure their properties with ease. Here, we show how one may immediately quantify these beams' parameters without need for additional fabrication or nonstandard microscopic tools. Our experimental results are backed by numerical simulations and analytic derivation.

Predictors of Suicidal Behaviors during Hospitalization among Adolescents Admitted Due to Suicidal Behaviors: A 10-Year Retrospective Naturalistic Study.

Objectives: Suicidality during hospitalization is a common phenomenon with potential devastating consequences. We attempted to identify risk factors for in-hospital suicidality in a high risk group of adolescent inpatients hospitalized for suicidal behaviors (SB). Methods: The database of a tertiary adolescent psychiatric ward was screened for patients hospitalized consecutively for SB during 2001-2010. Data on documented demographic, clinical, and behavioral risk factors were collected. Suicidal events during hospitalization were classified according to the Columbia Classification Algorithm of Suicide Assessment. Results: The sample included 122 inpatients (53% female) aged 10-19 (Mean=15.77, Standard Deviation=2.89) years admitted for SB. Thirty-seven youth (30%) exhibited SB during the hospitalization period (the "suicidal group"), ten of which attempted suicide while hospitalized. There were no significant differences in demographic and clinical parameters between the suicidal and the non-suicidal groups. Younger age, history of drug use and a history of non-suicidal self-injury (NSSI) were independent predictors of a SA during hospitalization. A previous SA added significant risk to SA during hospitalization only in the group that had a history of NSSI. Conclusions: A high risk of SB exists among adolescents hospitalized for suicidality. The risk assessment for SA during hospitalization should include age, history of drug use and previous SA combined with a history of NSSI. Future studies should expand the efforts to identify potential risk factors of SB during hospitalization in this unique high-risk group.

Spherical aberration correction in a scanning transmission electron microscope using a sculpted thin film.

Nearly eighty years ago, Scherzer showed that rotationally symmetric, charge-free, static electron lenses are limited by an unavoidable, positive spherical aberration. Following a long struggle, a major breakthrough in the spatial resolution of electron microscopes was reached two decades ago by abandoning the first of these conditions, with the successful development of multipole aberration correctors. Here, we use a refractive silicon nitride thin film to tackle the second of Scherzer's constraints and demonstrate an alternative method for correcting spherical aberration in a scanning transmission electron microscope. We reveal features in Si and Cu samples that cannot be resolved in an uncorrected microscope. Our thin film corrector can be implemented as an immediate low cost upgrade to existing electron microscopes without re-engineering of the electron column or complicated operation protocols and can be extended to the correction of additional aberrations.

Prospects for electron beam aberration correction using sculpted phase masks.

Technological advances in fabrication methods allowed the microscopy community to take incremental steps towards perfecting the electron microscope, and magnetic lens design in particular. Still, state of the art aberration-corrected microscopes are yet 20-30 times shy of the theoretical electron diffraction limit. Moreover, these microscopes consume significant physical space and are very expensive. Here, we show how a thin, sculpted membrane is used as a phase-mask to induce specific aberrations into an electron beam probe in a standard high resolution TEM. In particular, we experimentally demonstrate beam splitting, two-fold astigmatism, three-fold astigmatism, and spherical aberration.

Effects of long-term valproic acid treatment on hematological and biochemical parameters in adolescent psychiatric inpatients: a retrospective naturalistic study.

The objective of this study was to determine the long-term hematological and biochemical side effects of valproic acid (VPA) in psychiatric adolescent inpatients. A retrospective naturalistic study design was used. Participants were psychiatric inpatients treated with VPA, alone or in combination with other medications. Electronic medical files were reviewed for changes in hematological and biochemical parameters following a course of VPA treatment. One hundred and four adolescents aged 12-18 (mean 15.76±1.58) years fulfilled the study criteria. The mean blood level and duration of VPA treatment were 65.81±22.18 mcg/ml and 98.57±135.94 days, respectively. The mean levels of thyroid-stimulating hormones and triglyceride levels increased significantly from the first to the last measurement. Platelet count decreased significantly following VPA treatment. No correlation was observed between these parameters and age, duration of treatment, or VPA levels. No serious adverse events were reported. Long-term VPA treatment in adolescents with psychiatric disorders is associated with significant increases in triglyceride levels. Moreover, VPA-treated adolescent psychiatric inpatients may be at risk of developing pituitary-thyroid axis dysregulation and decreased platelet count. Therefore, baseline measurement of thyroid functions and metabolic and hematological parameters and monitoring throughout the treatment are recommended.