Morphological and biochemical responses of a neotropical pest insect to low temperatures.

As traditionally cold areas become warmer due to climate change, temperature could no longer be a barrier to the establishment of non-native insects. This is particularly relevant for pest insects from warm and tropical areas, mainly those with some tolerance to moderately low temperatures, which could expand their range into these new locations. From this perspective, in this work we studied the morphological and biochemical responses of the Neotropical pest Paysandisia archon to low temperatures, as part of a possible strategy to colonize new areas. To that end, wild larvae were exposed for 7 days to either low (1 and 5 °C) or ambient (23 °C) temperatures. We then quantified the inner and outer morphological changes, by X-Ray Computer Tomography and Digital Holographic Microscopy, as well as the accumulation of metabolites acting as potential endogenous cryoprotectants, by Spectrophotometry. We found that Paysandisia archon developed a cold-induced response based on different aspects. On the one hand, morphological changes occurred with a significant reduction both in fluids susceptible to freezing and fat body, together with the thickening, hardening and increased roughness of the integument. On the other hand, we found an increase in the hemolymph concentration of cryoprotective substances such as glucose (6-fold) and glycerol (2-fold), while trehalose remained unchanged. Surprisingly, this species did not show any evidence of cold-induced response unless the environmental temperature was remarkably low (1 °C). These results could be useful to improve models predicting the possible spread of such a pest, which should incorporate parameters related to its resistance to low temperatures.

Toward a personalized closed-loop stimulation of the visual cortex: Advances and challenges.

Current cortical visual prosthesis approaches are primarily unidirectional and do not consider the feed-back circuits that exist in just about every part of the nervous system. Herein, we provide a brief overview of some recent developments for better controlling brain stimulation and present preliminary human data indicating that closed-loop strategies could considerably enhance the effectiveness, safety, and long-term stability of visual cortex stimulation. We propose that the development of improved closed-loop strategies may help to enhance our capacity to communicate with the brain.

Experimental determination of nanocomposite grating structures by light- and neutron-diffraction in the multi-wave-coupling regime.

We experimentally demonstrate how to accurately retrieve the refractive index profile of photonic structures by standard diffraction experiments and use of the rigorous coupled-wave analysis in the multi-wave coupling regime, without the need for taking any auxiliary data. In particular, we show how the phases of the Fourier components of a periodic structure can be fully recovered by deliberately choosing a probe wavelength of the diffracting radiation much smaller than the lattice constant of the structure. In the course of our demonstration, we accurately determine the slight asymmetry of the structure of nanocomposite phase gratings by light and neutron diffraction measurements.

Morphological response of the red palm weevil, Rhynchophorus ferrugineus, to a transient low temperature analyzed by computer tomography and holographic microscopy.

The red palm weevil (RPW), Rhynchophorus ferrugineus, is one of the worst palm pests worldwide. Our study aims to assess its internal and external morphological response to a sudden but transient decrease in the environmental temperature. Wild pre-pupae were subjected for 7 days to either low (5.0 ± 0.5 °C) or ambient temperature (23 ± 1 °C). Such conditions mimic a thermal anomaly happening in the larval stage most exposed to environmental factors. We quantified the changes undergone at: 1) the internal morphology, by X-Ray Computer Tomography (CT); 2) the 3-D integument' architecture, by Digital Holographic Microscopy (DHM); and 3) the glucose in hemolymph as a potential endogenous cryoprotectant. From X-ray CT we found that both pre-pupae subjected to cold and those remaining at ambient temperature follow a development where their fat body content decreases while a thick and dense cuticle is formed. There was no difference between both groups in the rate of change of fat body/dense tissues. Nevertheless, the cold group presents a slight developmental delay at the level of hemolymph content. Through DHM we again obtained that pre-pupae subjected to cold have not experienced a stop in their development. However, a more obvious developmental delay is now observed in this group at the level of the integumental roughness. Finally, regarding glucose, we found similar levels in control and ambient temperature larvae, while it was clearly increased in 51,7% of those subjected to cold. Our whole results provide morphological and biochemical evidence showing that the larval-pupal transition of the RPW continues almost undisturbed even during the quiescent state induced by a sudden and severe cold event. Nevertheless, a certain developmental delay is observed in both internal and external morphology. Additionally, the increased glucose level only found in the cold group suggests that glucose is part of the RPW cold tolerance strategy.

Theoretical and experimental analysis of pulse delay in bacteriorhodopsin films by a saturable absorber theory.

Time-delay of transmitted pulses with respect to the incident pulse in bacteriorhodopsin films has been studied without the use of a pump beam. Based on a modified saturable absorber model, analytical expressions of the transmitted pulse have been obtained. As a result, time delay, distortion and fractional delay have been analyzed for sinusoidal pulses with a low background. A good agreement between theory and experiences has been observed.

Multifunctional hybrid materials for combined photo and chemotherapy of cancer.

Combined chemo and photothermal therapy in in vitro testing has been achieved by means of multifunctional nanoparticles formed by plasmonic gold nanoclusters with a protecting shell of porous silica that contains an antitumor drug. We propose a therapeutic nanoplatform that associates the optical activity of small gold nanoparticles aggregates with the cytotoxic activity of 20(S)-camptothecin simultaneously released for the efficient destruction of cancer cells. For this purpose, a method was used for the controlled assembly of gold nanoparticles into stable clusters with a tailored absorption cross-section in the vis/NIR spectrum, which involves aggregation in alkaline medium of 15 nm diameter gold colloids protected with a thin silica layer. Clusters were further encapsulated in an ordered homogeneous mesoporous silica coating that provides biocompatibility and stability in physiological fluids. After internalization in 42-MG-BA human glioma cells, these protected gold nanoclusters were able to produce effective photothermolysis under femtosecond pulse laser irradiation of 790 nm. Cell death occurred by combination of a thermal mechanism and mechanical disruption of the membrane cell due to induced generation of micrometer-scale bubbles by vaporizing the water inside the channels of the mesoporous silica coating. Moreover, the incorporation of 20(S)-camptothecin within the pores of the external shell, which was released during the process, provoked significant cell death increase. This therapeutic model could be of interest for application in the treatment and suppression of non-solid tumors.

Coupled wave analysis of holographically induced transparency (HIT) generated by two multiplexed volume gratings.

We present a holographic system that can be used to manipulate the group velocity of light pulses. The proposed structure is based on the multiplexing of two sequential holographic volume gratings, one in transmission and the other in reflection geometry, where one of the recording beams must be the same for both structures. As in other systems such as grating induced transparency (GIT) or coupled-resonator-induced transparency (CRIT), by using the coupled wave theory it is shown that this holographic structure represents a classical analogue of the electromagnetically induced transparency (EIT). Analytical expressions were obtained for the transmittance induced at the forbidden band (spectral hole) and conditions where the group velocity was slowed down were analyzed. Moreover, the propagation of Gaussian pulses is analyzed for this system by obtaining, after further approximations, analytical expressions for the distortion of the transmitted field. As a result, we demonstrate the conditions where the transmitted pulse is slowed down and its shape is only slightly distorted. Finally, by comparing with the exact solutions obtained, the range of validity of all the analytical formulae was verified, demonstrating that the error is very low.

Double-pass system analysis of the visual outcomes and optical performance of an apodized diffractive multifocal intraocular lens.

PURPOSE: To evaluate the postoperative ocular optical quality using a double-pass method and assess visual outcomes in eyes with an apodized multifocal intraocular lens (IOL) and to correlate the findings with IOL power. SETTING: Vissum Corporation, Alicante, Spain. DESIGN: Case series. METHODS: This study evaluated eyes that had cataract surgery with implantation of an AcrySof ReSTOR SN6AD3 multifocal IOL. Near and far visual acuities were measured postoperatively at 1 month and 6 months. Ocular optical quality was assessed at 1 month using a double-pass system (Optical Quality Analysis System), and the point-spread function (PSF) and modulation transfer function (MTF) were characterized. RESULTS: The study included 38 eyes of 19 patients with a mean age of 63.4 years ± 8.4 (SD). The improvements in uncorrected distance visual acuity (from 0.57 ± 0.31 logMAR preoperatively to 0.11 ± 0.13 logMAR 1 month postoperatively and 0.11 ± 0.12 logMAR at 6 months) were statistically significant (P<.00001), as were the improvements in uncorrected near visual acuity (0.76 ± 0.40 logMAR preoperatively to 0.21 ± 0.11 logMAR and 0.12 ± 0.09 logMAR, respectively) (P<.00001). The IOL power correlated significantly with PSF width (r = 0.57, P = .017) and the MTF cutoff frequency (r = -0.36, P = .05). Furthermore, the lower the IOL power, the better the near and distance visual acuities, especially 1 month postoperatively. CONCLUSION: The apodized multifocal IOL restored distance and near visual function, although IOL power was a limiting factor to the final visual outcomes and optical quality.

Nonparaxial diffraction analysis of Airy and SAiry beams.

We theoretically analyze Airy beams by solving the exact vectorial Helmholtz equation using boundary conditions at a diffraction aperture. As result, the diffracted beams are obtained in the whole space; thus, we demonstrate that the parabolic trajectories are larger than those previously reported, showing that the Airy beams start to form before the Fourier plane. We also demonstrate the possibility of using a new type of Airy beams (SAiry beams) with finite energy that can be generated at the focal plane of the lens due to diffraction by a circular aperture of a spherical wave modified by a cubic phase. The finite energy ensured by the principle of conservation of energy of a diffracted beam.

Full characterization of holographic reflection gratings recorded on BB640 emulsions.

A complete characterization of unslanted holographic reflection gratings with high diffraction efficiency recorded on ultrafine grain emulsion BB640 has been achieved. By use of a wavelength-dependent absorption coefficient, the diffraction efficiency, the replay wavelength, and the spectral bandwidth of each recording has been obtained. Corresponding index modulation, absorption, and effective thickness have been obtained with high accuracy by fitting the experimental data with Kogelnik's theory.

One-dimensional photonic crystals with an amplitude-modulated dielectric constant in the unit cell.

Photonic band structures of one-dimensional photonic crystals with an amplitude-modulated dielectric constant in the unit cell were studied. With this structure two bandgaps in the visible and one in the IR region were predicted. Experimental measurements of the two photonic bandgaps in the visible spectrum were made in a photonic crystal recorded in a holographic emulsion. Good agreement between experimental and theoretical results was obtained.

Nonlinear effects on holographic reflection gratings recorded with BB640 emulsions.

Nonlinear recording effects on holographic re ection gratings recorded on BB640 emulsions have been studied. Using an analytical approach to the characteristic curve of this emulsions, the density profiles recorded in the developed emulsions that correspond to the original light pattern generated by the holographic setup have been obtained. The final spatial profiles of the refraction index resulting from different exposure levels and different bleaching processes have been evaluated studying the experimental diffraction efficiency and comparing it with Kogelnik's theory. The quality of the fittings of this model with the experimental spectral responses of the final gratings has been used as a measure of the accordance between the original sinusoidal and periodical light distribution and the obtained modulation profile of the processed hologram. The range of applicability of the theoretical model to the experimental results has been evaluated using different bleaching processes.

Multiple band holographic reflection gratings recorded in new ultra-fine grain emulsion BBVPan.

We present the results obtained using the new panchromatic ultra-fine grain emulsion BBVPan, manufactured by Colourholographics Ltd., to produce multiple band holographic reflection gratings, multiplexed on a single layer of material. Three different laser systems were used: He-Cd, frequency-doubled Nd-YAG and He-Ne. High diffraction efficiencies, of over 52%, were obtained for each of the three bands, with little wavelength shifting. The holographic response of the multiplexed hologram was compared with the theoretical response to demonstrate that there is negligible contribution of the crosstalk between recordings in the visible range of the spectrum for this specific configuration.

Purple membrane-polyacrilamide films as holographic recording materials.

The holographic parameters of purple membrane-polyacrylamide films obtained from a mutant form of Halobacterium salinarum (originally Halobacterium halobium) were measured. The synthesized films have an absorption of around 2.5 at 532 nm and a pH of 8.65. The results show that diffraction efficiencies of about 1.2 % (measured at 633 nm) can be achieved with writing intensities in the range of 200-400 mW/cm2 (532 nm), and these values remain constant after saturation. Pump-probe experiments were also used to measure the M state lifetime and our PM films were found to have the lowest M state lifetime described at this pH.

Comparison of direct, rehalogenating, and solvent bleaching processes with BB-640 plates.

Bleaching is one of the key processes in the production of phase holograms with fine grain silver halide emulsions. This step was widely studied for discontinued Kodak, Agfa, and Ilford emulsions, and most of those results have been optimized with small changes for presently available holographic emulsions. A study of the different bleaching techniques with BB-640 holographic emulsions is presented. Some interesting new features found are the high-diffraction efficiencies achieved with direct rehalogenating bleaching and with reversal bleaching, with higher values and better sensitivities than those of classical fixation-free rehalogenating bleaching. In particular, we have found that the highest diffraction efficiency and the lowest scattering is obtained with AAC developer and reversal bleach R-9, with diffraction efficiency values of 82%.

Hologram recording in polyvinyl alcohol/acrylamide photopolymers by means of pulsed laser exposure.

The variation in transmittance produced when a photopolymer is irradiated with a pulsed laser is analyzed and experimental results obtained when diffraction gratings are stored using pulsed exposure are presented. In either case, the influence of the energy of the irradiation pulse, the number of pulses, and the pulse repetition rate were studied. The photopolymer used was an acrylamide/polyvinyl alcohol dry film with a yellow eosin-thiethanol-amine mixture as a photoinitiator system. The recording of the gratings was performed by use of a holographic copying process. The samples were exposed and holograms recorded with a collimated beam from a frequency-doubled Nd:YAG (532 nm) Q-switched laser. Our initial results show that it is possible to obtain diffraction gratings with a diffraction efficiency of 60% and a refractive index modulation up to 2.8 x 10(-3). The energetic sensitivities achieved are close to those obtained with the same material and continuous irradiation without a preprocessing of the gratings.