Nanoparticle-based receptors mimic protein-ligand recognition

The self-assembly of a monolayer of ligands on the surface of noble metal nanoparticles dictates the fundamental nanoparticle\u2019s behavior and its functionality. In this combined computational\u2013experimental study, we analyze the structure, organization, and dynamics of functionalized coating thiols in monolayer-protected gold nanoparticles (AuNPs). We explain how functionalized coating thiols self-organize through a delicate and somehow counterintuitive balance of interactions within the monolayer itself and with the solvent. We further describe how the nature and plasticity of these interactions modulate nanoparticle-based chemosensing. Importantly, we found that self-organization of coating thiols can induce the formation of binding pockets in AuNPs. These transient cavities can accommodate small molecules, mimicking protein-ligand recognition, which may explain the selectivity and sensitivity observed for different organic analytes in NMR chemosensing experiments. Thus, our findings advocate for the rational design of tailored coating groups to form specific recognition binding sites on monolayer-protected AuNPs

The Actuator Design and the Experimental Tests of a New Technology Large Deformable Mirror for Visible Wavelengths Adaptive Optics

Recently, Adaptive Secondary Mirrors showed excellent on-sky results in the Near Infrared wavelengths. They currently provide 30mm inter-actuator spacing and about 1 kHz bandwidth. Pushing these devices to be operated at visible wavelengths is a challenging task. Compared to the current systems, working in the infrared, the more demanding requirements are the higher spatial resolution and the greater correction bandwidth. In fact, the turbulence scale is shorter and the parameter variation is faster. Typically, the former is not larger than 25 mm (projected on the secondary mirror) and the latter is 2 kHz, therefore the actuator has to be more slender and faster than the current ones. With a soft magnetic composite core, a dual-stator and a single-mover, VRALA, the actuator discussed in this paper, attains unprecedented performances with a negligible thermal impact. Pre-shaping the current required to deliver a given stroke greatly simplifies the control system, whose output supplies the current generator. As the inductance depends on the mover position, the electronics of this generator, provided with an inductance measure circuit, works also as a displacement sensor, supplying the control system with an accurate feed-back signal. A preliminary prototype, built according to the several FEA thermo-magnetic analyses, has undergone some preliminary laboratory tests. The results of these checks, matching the design results in terms of power and force, show that the the magnetic design addresses the severe specifications

Numerical control matrix rotation for the LINC-NIRVANA Multi-Conjugate Adaptive Optics system

LINC-NIRVANA will realize the interferometric imaging focal station of the Large Binocular Telescope. A double Layer Oriented multi-conjugate adaptive optics system assists the two arms of the interferometer, supplying high order wave-front correction. In order to counterbalance the field rotation, mechanical derotation for the two ground wave-front sensors, and optical derotators for the mid-high layers sensors fix the positions of the focal planes with respect to the pyramids aboard the wave-front sensors. The derotation introduces pupil images rotation on the wavefront sensors: the projection of the deformable mirrors on the sensor consequently change. The proper adjustment of the control matrix will be applied in real-time through numerical computation of the new matrix. In this paper we investigate the temporal and computational aspects related to the pupils rotation, explicitly computing the wave-front errors that may be generated.Comment: 6 pages, 2 figures, presented at SPIE Symposium "Astronomical Telescopes and Instrumentation'' conference "Adaptive Optics Systems II'',Sunday 27 June 2010, San Diego, California, US

Scheduling of space to ground quantum key distribution

Satellite-based platforms are currently the only feasible way of achieving intercontinental range for quantum communication, enabling thus the future global quantum internet. Recent demonstrations by the Chinese spacecraft Micius have spurred an international space race and enormous interest in the development of both scientific and commercial systems. Research efforts so far have concentrated upon in-orbit demonstrations involving a single satellite and one or two ground stations. Ultimately satellite quantum key distribution should enable secure network communication between multiple nodes, which requires efficient scheduling of communication with the set of ground stations. Here we present a study of how satellite quantum key distribution can service many ground stations taking into account realistic constraints such as geography, operational hours, and most importantly, weather conditions. The objective is to maximise the number of keys a set of ground stations located in the United Kingdom could share while simultaneously reflecting the communication needs of each node and its relevance in the network. The problem is formulated as a mixed-integer linear optimisation program and solved to a desired optimality gap using a state of the art solver. The approach is presented using a simulation run throughout six years to investigate the total number of keys that can be sent to ground stations

A Smart IoT-Aware System For Crisis Scenario Management

In most dangerous events, involving many people in large buildings, rescue workers need to intervene in a timely and targeted manner in order to help most number of people and secure the environments without wasting resources. This work presents an Internet of Things(IoT)-based framework, aiming at monitoring environmental parameters in order to alert rescuers when they exceed some alarm thresholds. A hardware infrastructure driven by a software layer adds flexibility and adaptability to the Complex Event Processing engine and to a rule engine-based reflective middleware that manages and analyzes raw data in conjunction with a knowledge base modeling the application domain

RADICAL FORMATION ON CTMP FIBERS BY ARGON PLASMA TREATMENTS AND RELATED LIGNIN CHEMICAL CHANGES

The changes at molecular level induced by cold argon plasma treat-ments on fibers obtained from chemi-thermo-mechanical pulp (CTMP) fibers were investigated. The radicals formed on CTMP fibers after treatments were identified and quantified by Electron Paramagnetic Resonance (EPR) spectroscopy. The plasma conditions which maximize the formation of radicals on fibers were assessed: after treatment with 0.4 mbar Ar pressure and 75 W radiofrequency power, phenoxy radicals triple their concentration in only 60 s and reach a value 4 times higher than that reported for laccase-catalyzed lignin oxidation. It was found that in plasma-treated fibers, the formation of radicals competes with their coupling. This latter result leads to cross-linkages of the lignin mono-meric units and formation of new intermonomeric C-C and C-O bonds, for the first time assigned to specific molecular interactions through Heteronuclear Single Quantum Coherence (2D-HSQC) spectroscopy and Nuclear Magnetic Resonance spectroscopy of carbon (13C-NMR). These results were confirmed by Nuclear Magnetic Resonance spectros-copy of phosphorous (31P-NMR). The lack of evidences of inter-fiber bond interactions, deduced from Gel Permeation Chromatography (GPC) data, suggests the possible application of plasma treatments for the production of wood fiber-based composites

Sulfur hexafluoride (SF₆) plasma treatment of medical grade poly(methyl methacrylate)

Medical-grade poly(methyl methacrylate) (PMMA) is widely employed in the fabrication of intraocular lenses (IOLs), but suffers from opacification, a postoperative complication that leads to the failure of the implanted intraocular lenses. The opacification occurs when inorganic-based deposits accumulate on the surface of the IOL and are prevalent in hydrophilic materials. Here, the surface of medical-grade PMMA has been fluorinated by sulphur hexafluoride (SF₆) plasma treatment to increase surface hydrophobicity thus improving the material lifetime in optical applications. Hydrophobic properties of the treated PMMA were investigated by means of contact angle measurements, while chemical modification was assessed by X-ray Photoelectron Spectroscopy (XPS) and Attenuated Total Reflectance Fourier Transform Infrared (ATR/FTIR) spectroscopy. Surface morphological changes due to possible etching effects were investigated by Atomic Force Microscopy (AFM). The transparency of the treated PMMA was assessed by UV/VIS spectroscopy. Finally, the influence of the plasma treatment on the inorganic salts deposition was investigated by immersion in Simulated Aqueous Humour (SAH), followed by XPS analysis. The modified samples showed less deposition on the surface than the unmodified sample, moreover, a decrease of the transmittance in the UV-violet range (300–430 nm) was detected, open the possibility of interesting applications of this treatment for the creation of a UV filter in ophthalmic optical devices

Photogrammetric 3D model via smartphone GNSS sensor. Workflow, error estimate, and best practices

Geotagged smartphone photos can be employed to build digital terrain models using structure from motion-multiview stereo (SfM-MVS) photogrammetry. Accelerometer, magnetometer, and gyroscope sensors integrated within consumer-grade smartphones can be used to record the orientation of images, which can be combined with location information provided by inbuilt global navigation satellite system (GNSS) sensors to geo-register the SfM-MVS model. The accuracy of these sensors is, however, highly variable. In this work, we use a 200 m-wide natural rocky cliff as a test case to evaluate the impact of consumer-grade smartphone GNSS sensor accuracy on the registration of SfM-MVS models. We built a high-resolution 3D model of the cliff, using an unmanned aerial vehicle (UAV) for image acquisition and ground control points (GCPs) located using a differential GNSS survey for georeferencing. This 3D model provides the benchmark against which terrestrial SfM-MVS photogrammetry models, built using smartphone images and registered using built-in accelerometer/gyroscope and GNSS sensors, are compared. Results show that satisfactory post-processing registrations of the smartphone models can be attained, requiring: (1) wide acquisition areas (scaling with GNSS error) and (2) the progressive removal of misaligned images, via an iterative process of model building and error estimation

Analysis of land cover dynamics in Mozambique (2001–2016)

Land cover change (LCC) is a complex and dynamic process influenced by social, economic, and biophysical factors that can cause significant impacts on ecological processes and biodiversity conservation. The assessment of LCC is particularly relevant in a country like Mozambique where livelihood strongly depends on natural resources. In this study, LCC was assessed using a point-based sampling approach through Open Foris Collect Earth (CE), a free and open-source software for land assessment developed by the Food and Agriculture Organization of the United Nations. This study aimed to conduct an LCC assessment using CE for the entire Mozambique, and according to three different land classifications: administrative boundaries (provinces), ecoregions, and protected vs unprotected areas. A set of 23,938 randomly selected plots, with an area of 0.5 hectares, placed on a 4 × 4 km regular grid over the entire country, was assessed using CE. The analysis showed that Mozambique has gone through significant loss of forest (− 1.3 Mha) mainly to the conversion to cropland. Deforestation is not occurring evenly throughout the country with some provinces, such as Nampula and Zambezia, characterized by higher rates than others, such as Gaza and Niassa. This result can be explained considering a combination of ecological and socio-economic factors, as well as the conservative role played by the protected areas. Our study confirmed that LCC is a complex phenomenon, and the augmented visual interpretation methodology can effectively complement and integrate the LCC analyses conducted using the traditional wall-to-wall mapping to support national land assessment and forest inventories and provide training data for environmental modeling