One Dimensional Inverse Dielectric Profiling of Embedded Slabs by a Quadratic Approximation

In this paper the inverse problem of the determination of the dielectric profile of a slab embedded into a homogeneous half space starting from the knowledge of the scattered field for different illumination angles is considered. A comparison between the features of a linear and a quadratic distorted approximation of the scattering problem is carried out, in order to determine the kind of profiles that can be reconstructed. In particular, the investigation of the direct problem reveals that, under the linear approximation, only a limited number of Fourier harmonics of the profile give contribution to the scattered field. The use of the quadratic approximation allows to change the number and order of the harmonic that can be imaged. The dependence of the results on the dielectric permittivity of the host medium is also highlighted. Numerical examples support the theoretical considerations.     

A Switched Opamp-Based Bandpass Filter: Design and Implementation in a 0.35 μm CMOS Technology

A fully differential SC bandpass filter (central frequency, 58 kHz; Q = 15; and voltage gain, 8) based on the switched-opamp approach is designed and implemented in this work. The filter operates from a single 1 V supply voltage and is realized in a 0.35 m CMOS technology. It has been characterized with a sampling frequency of 1 MHz and its power consumption is about 230 W. As a main internal filter component, an appropiate switched opamp was also designed. Its common-mode feedback circuit was implemented by using an error amplifier and sampling of the output common-mode voltage is carried out by applying a DC offset to level shift the common-mode sample. It provides an accurate common-mode output for a wide temperature and supply voltage ranges.     

PbS/CdS/ZnS Quantum Dots: A Multifunctional Platform for In Vivo Near‐Infrared Low‐Dose Fluorescence Imaging

Over the past decade, near‐infrared (NIR)‐emitting nanoparticles have increasingly been investigated in biomedical research for use as fluorescent imaging probes. Here, high‐quality water‐dispersible core/shell/shell PbS/CdS/ZnS quantum dots (hereafter QDs) as NIR imaging probes fabricated through a rapid, cost‐effective microwave‐assisted cation exchange procedure are reported. These QDs have proven to be water dispersible, stable, and are expected to be nontoxic, resulting from the growth of an outer ZnS shell and the simultaneous surface functionalization with mercaptopropionic acid ligands. Care is taken to design the emission wavelength of the QDs probe lying within the second biological window (1000–1350 nm), which leads to higher penetration depths because of the low extinction coefficient of biological tissues in this spectral range. Furthermore, their intense fluorescence emission enables to follow the real‐time evolution of QD biodistribution among different organs of living mice, after low‐dose intravenous administration. In this paper, QD platform has proven to be capable (ex vivo and in vitro) of high‐resolution thermal sensing in the physiological temperature range. The investigation, together with the lack of noticeable toxicity from these PbS/CdS/ZnS QDs after preliminary studies, paves the way for their use as outstanding multifunctional probes both for in vitro and in vivo applications in biomedicine.     

Autonomous and teleoperation control of a mobile robot

The present work proposes an autonomous tracking control system and a control structure to combine autonomous and teleoperation commands in a bicycle-type mobile robot. This compounded operation renders great flexibility to the control system of the mobile robot. For autonomous operation, a simple tracking controller that includes compensation of the robot dynamics is developed. This tracking control system is proved to be stable in the sense that it asymptotically reaches the tracking objective. Teleoperation with visual access to the robot’s workspace is integrated via a joystick with the autonomous operation of the robot. Simulations and experimental results on a prototype robot show the feasibility and performance of the proposed control system.     

Detection of Channel Variations to Improve Channel Estimation Methods

In current digital communication systems, channel information is typically acquired by supervised approaches that use pilot symbols included in the transmit frames. Given that pilot symbols do not convey user data, they penalize throughput spectral efficiency, and transmit energy consumption of the system. Unsupervised channel estimation algorithms could be used to mitigate the aforementioned drawbacks although they present higher computational complexity than that offered by supervised ones. This paper proposes a simple decision method suitable for slowly varying channels to determine whether the channel has suffered a significant variation, which requires to estimate the matrix of the recently changed channel. Otherwise, a previous estimate is used to recover the transmitted symbols. The main advantage of this method is that the decision criterion is only based on information acquired during the time frame synchronization, which is carried out at the receiver. We show that the proposed criterion provides a considerable improvement of computational complexity for both supervised and unsupervised methods, without incurring in a penalization in terms of symbol error ratio. Specifically, we consider systems that make use of the popular Alamouti code. Performance evaluation is accomplished by means of simulated channels as well as making use of indoor wireless channels measured using a testbed.     

Unconventional method used in synthesis of polyphosphoesters

Polyphosphonates, polyphosphates, polyarylazophosphonates and polyarylazophosphates were synthesized by a new alternative to the classical phase transfer catalysis, respectively, the modified inverse phase transfer catalysis (IPTC) polycondensation of various phenylphosphonic (phosphoric) dichlorides (phenylphosphonic dichloride, phenylphosphoric dichloride, p-chlorophenylphosphoric dichloride) with bisphenols: bisphenol A, tetrabromobisphenol A, bis-(4-hydroxyphenyl)methane (bisphenol F), 4,4′-dihydroxyazobenzene. The polymers were characterized by infrared spectroscopy and magnetic resonance (¹H-NMR, ³¹P-NMR, ¹³C-NMR) spectroscopy. Yields in the range of 63.5–85% and molecular weights (M _w) of ~2,000–8,200 g mol^?1 were obtained. Polyphosphonates were stable up 210–270 °C and polyphosphates up 190–220 °C in air atmosphere. For a correct estimation of the thermal behavior of similar compounds, a kinetic analysis using a modified version of Non Parametric Kinetic method for representative polyphosphonate and polyphosphate was realized. The studies made on the hydrolytic degradation of the synthesized polyphosphates show that the most stable polymer under alkali-catalyzed degradation is the polyphosphate obtained by IPTC of phenylphosphoric dichloride and bisphenol A.     

Evaluation of Oxidative Stress Biomarkers,Pro-Inflammatory Cytokines,and Histological Changes in Experimental Hypertension,Dyslipidemia, and Type 1 Diabetes Mellitus

The present study aims to compare the oxidative stress biomarkers, pro-inflammatory cytokines, and histological changes induced by three cardiovascular risk factors, namely, hypertension, dyslipidemia, and type 1 diabetes mellitus. Hypertension was induced with 40 mg/kg body weight (b.w.) of N omega-nitro-L-arginine-methyl (L-NAME) administered orally. Dyslipidemia was induced by the administration of a diet with a high cholesterol (2%) content. Diabetes mellitus was induced by intraperitoneal administration of a single dose of streptozocin (65 mg/kg). Malondialdehyde (MDA) and total oxidative status (TOS) are increased by all three cardiovascular risk factors (up to 207%). The indirect assessment of NO synthesis (NOx) is observed to be reduced after L-NAME administration (43%), and dyslipidemia induction (16%), while type 1 diabetes mellitus is associated with the highest levels of NOx (increased 112%). Hypertension, dyslipidemia, and type 1 diabetes reduced the total antioxidative capacity (TAC) and total thiol (SH) levels (up to 57%). The values of evaluated pro-inflammatory cytokines, tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β), assessed from the ascending aorta were elevated by all three cardiovascular risk factors, with the highest levels induced by type 1 diabetes mellitus (up to 259%). The histopathological examination of the ascending and descending aorta revealed reversible pro-atherogenic changes consisting of the accumulation of lipid droplets in the subendothelial connective tissue on rats with hypertension and dyslipidemia. Irreversible pro-atherogenic changes consisting of a reduction of the specific elasticity of the arteries were observed in rats with type 1 diabetes mellitus. Type 1 diabetes mellitus demonstrates an alteration of the oxidative stress parameters, the elevation of tissue levels of the pro-inflammatory cytokines and causing irreversible pro-atherogenic changes on the aortic wall.     

Photocatalytic Degradation of 4,4′-Isopropylidenebis(2,6-dibromophenol) on Magnetite Catalysts vs. Ozonolysis Method: Process Efficiency and Toxicity Assessment of Disinfection By-Products

Flame retardants have attracted growing environmental concern. Recently, an increasing number of studies have been conducted worldwide to investigate flame-retardant sources, environmental distribution, living organisms’ exposure, and toxicity. The presented studies include the degradation of 4,4′-isopropylidenebis(2,6-dibromophenol) (TBBPA) by ozonolysis and photocatalysis. In the photocatalytic process, nano- and micro-magnetite (n-Fe₃O₄ and μ-Fe₃O₄) are used as a catalyst. Monitoring of TBBPA decay in the photocatalysis and ozonolysis showed photocatalysis to be more effective. Significant removal of TBBPA was achieved within 10 min in photocatalysis (ca. 90%), while for ozonation, a comparable effect was observed within 70 min. To determine the best method of TBBPA degradation concentration on COD and TOC, the removals were examined. The highest oxidation state was obtained for photocatalysis on μ-Fe₃O₄, whereas for n-Fe₃O₄ and ozonolysis, the COD/TOC ratio was lower. Acute toxicity results show noticeable differences in the toxicity of TBBPA and its degradation products to Artemia franciscana and Thamnocephalus platyurus. The EC₅₀ values indicate that TBBPA degradation products were toxic to harmful, whereas the TBPPA and post-reaction mixtures were toxic to the invertebrate species tested. The best efficiency in the removal and degradation of TBBPA was in the photocatalysis process on μ-Fe₃O₄ (reaction system 1). The examined crustaceans can be used as a sensitive test for acute toxicity evaluation.