The applicability of islet transplantation as treatment for type 1 diabetes is limited by renal and islet toxicities of currently available immunosuppressants. We describe a novel immunosuppressive ...regimen using the antileukocyte functional antigen‐1 antibody efalizumab which permits long‐term islet allograft survival while reducing the need for corticosteroids and calcineurin inhibitors (CNI). Eight patients with type 1 diabetes and hypoglycemic unawareness received intraportal allogeneic islet transplants. Immunosuppression consisted of antithymocyte globulin induction followed by maintenance with efalizumab and sirolimus or mycophenolate. When efalizumab was withdrawn from the market in mid 2009, all patients were transitioned to regimens consisting of mycophenolate and sirolimus or mycophenolate and tacrolimus. All patients achieved insulin independence and four out of eight patients became independent after single‐islet transplants. Insulin independent patients had no further hypoglycemic events, hemoglobin A1c levels decreased and renal function remained stable. Efalizumab was well tolerated and no serious adverse events were encountered. Although long‐term follow‐up is limited by discontinuation of efalizumab and transition to conventional imunnosuppression (including CNI in four cases), these results demonstrate that insulin independence after islet transplantation can be achieved with a CNI and steroid‐free regimen. Such an approach may minimize renal and islet toxicity and thus further improve long‐term islet allograft survival.
An immunosuppressive regimen based on the anti‐LFA‐1 antibody efalizumab showed some promising results in eight islet transplant recipients. See Editorial by Oberholzer et al 1725.
We investigate graphene-based optical absorbers that exploit guided mode resonances (GMRs) attaining theoretically perfect absorption over a bandwidth of few nanometers (over the visible and ...near-infrared ranges) with a 40-fold increase of the monolayer graphene absorption. We analyze the influence of the geometrical parameters on the absorption rate and the angular response for oblique incidence. Finally, we experimentally verify the theoretical predictions in a one-dimensional, dielectric grating by placing it near either a metallic or a dielectric mirror, thus achieving very good agreement between numerical predictions and experimental results.
We propose an innovative approach for the realization of a microwave absorber fully transparent in the optical regime. This device is based on the Salisbury screen configuration, which consists of a ...lossless spacer, sandwiched between two graphene sheets whose sheet resistances are different and properly engineered. Experimental results show that it is possible to achieve near-perfect electromagnetic absorption in the microwave X-band. These findings are fully supported by an analytical approach based on an equivalent circuital model. Engineering and integration of graphene sheets could facilitate the realization of innovative microwave absorbers with additional electromagnetic and optical functionalities that could circumvent some of the major limitations of opaque microwave absorbers.
Double-nanotextured black diamond films with different geometries were fabricated by double-step femtosecond laser treatments at different split ratios of accumulated laser fluence. A “2D-like” ...pseudo-periodic nanostructure was obtained for the first time when the split ratio was slightly unbalanced in favour of the first step of the treatment, as inferred by scanning electron microscopy. Raman analysis showed that a residual biaxial stress, composed by a superposition of a tensile and a compressive component, is always present after the laser writing process, and that the two components tend to balance each other in the 2D pseudo-periodic case. Spectrophotometric measurements in the 200–2000 nm wavelength range returned outstanding solar absorptance values for all the fabricated films (reaching the unprecedented value of 99.1% in the “2D-like” structure), launching double-nanotextured black diamond as a possible alternative to black silicon as absorbing layer for high-efficiency solar cells.
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Abstract
We show that an appropriately designed chalcogenide metasurface allows the enhancement of harmonic generation in the UV range, a regime that conventional wisdom deems inaccessible because of ...absorption. Here we exploit a combination of the photonic band structure that forms when stacking As
2
S
3
metasurfaces, phase-locking, nonlinear dispersion, and improved field localization to enhance third harmonic conversion efficiency. We demonstrate an improvement of two orders of magnitude with respect to the single layer counterpart notwithstanding the fact that the harmonic signal is tuned deep in the absorption range at 285 nm.
A one-dimensional dielectric grating, based on a simple geometry, is proposed and investigated to enhance light absorption in a monolayer graphene exploiting guided mode resonances. Numerical ...findings reveal that the optimized configuration is able to absorb up to 60% of the impinging light at normal incidence for both TE and TM polarizations resulting in a theoretical enhancement factor of about 26 with respect to the monolayer graphene absorption (≈2.3%). Experimental results confirm this behavior showing CVD graphene absorbance peaks up to about 40% over narrow bands of a few nanometers. The simple and flexible design points to a way to realize innovative, scalable and easy-to-fabricate graphene-based optical absorbers.
Epsilon-near-zero materials are exceptional candidates for studying electrodynamics and nonlinear optical processes at the nanoscale. We demonstrate that by alternating a metal and a highly doped ...conducting-oxide, the epsilon-near-zero regime may be accessed resulting in an anisotropic, composite nanostructure that significantly improves nonlinear interactions. The investigation of the multilayer nanostructure reveals the actual role of the anisotropy, showing that high degrees of anisotropy might be necessary to effectively boost nonlinear processes. Moreover, using a microscopic, hydrodynamic approach we shed light on the roles of two competing contributions that are for the most part overlooked but that can significantly modify linear and nonlinear responses of the structure: nonlocal effects, which blueshift the resulting resonance, and the hot electrons nonlinearity, which redshifts the plasma frequency as the effective mass of free electrons increases as a function of incident power density and enhances the nonlinear signal by several orders of magnitude. Finally, we show that, even in the absence of second order bulk nonlinearity, second order nonlinear processes are also significantly enhanced by the layered structure.
Epsilon-near-zero (ENZ) materials are excellent platforms for nonlinear optical interactions. We demonstrate that the linear interference of two non-collinear, counter-propagating beams impinging at ...oblique angle can either enhance or suppress nonlinear optical processes depending on their initial phase difference. Our results validate the idea that using ENZ materials allows one to circumvent both phase-matching conditions and the use of resonant structures, thus providing a path for efficient and effective control of nonlinear processes.
Passive solid-state radiation detectors, based on the visible photoluminescence (PL) of radiation-induced colour centres in optically transparent lithium fluoride (LiF), polycrystalline thin films ...are under investigation for proton beam advanced diagnostics. After proton exposure, the latent images stored in LiF as local formations of stable F
and F
aggregate defects, are directly read with a fluorescence microscope under illumination in the blue spectral range. Adopting a suitable irradiation geometry, the energy density that protons deposit in the material can be recorded as a spatial distribution of these light-emitting defects, from which a luminous replica of the proton Bragg curve can be thereafter extracted and analysed to reconstruct the proton beam energy spectrum. Their peculiar properties, such as wide dynamic range and linearity of the spectrally-integrated PL response vs. dose, make the investigation of two-dimensional LiF film radiation detectors grown on several types of substrate highly attractive. Here, the case of a LiF thin film thermally evaporated on a silica substrate, irradiated at grazing incidence with a 35 MeV proton beam, is investigated and reported for the first time. A comparison of the measured photoluminescent Bragg curve with Monte Carlo simulations demonstrates that the Bragg peak in the film is located at the very same position that would be expected in the underlying silica substrate rather than in LiF. The film packing density is shown not to have a significant effect on the peak depth, while even small nonzero grazing angle of the impinging proton beam is able to significantly modify the shape of the Bragg curve. These findings are ascribed to the effects of multiple Coulomb scattering in both the film and the substrate and are interesting for proton beam diagnostics and dosimetry.
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