A Preliminary Investigation into the Design of an Implantable Optical Blood Glucose Sensor

Abstract A preliminary investigation into the design of a near-infrared (NIR) optical bio-implant for accurate measurement of blood glucose level is reported. The use of an array of electrically pumped vertical-cavity surface-emitting laser (VCSEL) diodes at specific wavelengths for high-power narrow single-frequency emission leads to a high signal-to-noise ratio in the measured NIR absorption spectrum while maximizing the sensor's sensitivity to small absorption changes. The emission wavelengths lie within the combination and first-overtone spectral bands known to be dominated by glucose absorption information. A Quantum well infrared (QWI) photodiode transducer senses the received optical power after passing through the blood sample, followed by an artificial neural network (ANN) for the measurement of glucose in a whole blood matrix. For an independent test set made with fresh bovine blood, the optimal ANN topology for processing the two selected spectral bands yielded a standard error of prediction of 0.42 mM (i.e., 7.56 mg/dl) over the glucose level range of 4−20 mM. The empirical results obtained with a prototype mounted on PCB for blood glucose monitoring are closely correlated with the absorption spectra collected on a Vertex 70 Bruker spectrometer

Kinetics and Equilibrium Study for the Adsorption of Maxilon Blue Dye on Prosopis juliflora Fruit Seeds as a Low-Cost Adsorbent

The aim of this work was to investigate the adsorption capacity of Maxilon Blue dye using Prosopis juliflora fruit seeds as an adsorbent. The seeds of P. Juliflora were utilized as a low-cost adsorbent to remove the cationic dye, Maxilon Blue, from an aqueous solution in batch experiments, examining the effects of mass, pH, and contact time. Three error functions —coefficient of determination, Chi-square, and the sum of error squares — were employed to assess the adsorption data. The adsorption equilibrium was characterized using Langmuir, Freundlich, and Temkin isotherm models. The equilibrium data closely followed the Langmuir model, indicating a maximum adsorption capacity of 85.54 mg/g on a monolayer. To elucidate the adsorption mechanisms, pseudo-first-order and pseudo-second-order kinetic models were applied. The kinetic analysis revealed that the adsorption process conformed best to the pseudo-second-order model. Consequently, this study demonstrates that P. juliflora fruit seeds are an effective, economical, and eco-friendly adsorbent for the removal of Maxilon Blue dye from aqueous solutions

Evaluation of 1,4-Benzothiazines in Steel Corrosion Inhibition in 15% HCl: Experimental and Theoretical Perspectives

Corrosion inhibitors are essential for metal protection. In this study, the efficacy of 1,4-Benzothiazine derivatives, particularly ethyl 3-hydroxy-2-(p-tolyl)-3,4-dihydro-2H-benzo[b][1,4]thiazine-3-carboxylate (EHBT) and 2-(4-chlorophenyl)-1,4-benzothiazin-3-one (CBT), was examined for carbon steel corrosion inhibition in 15 wt.% HCl. Techniques such as Electrochemical Impedance Spectroscopy (EIS), Potentiodynamic Polarization (PDP), weight loss measurement, and Scanning Electron Microscopy assessed the inhibitors' performance. Results showed inhibitor efficiency increased with concentration, with CBT and EHBT achieving up to 97% and 98% effectiveness respectively. Both acted as mixed inhibitors, reducing anodic and cathodic reactions. Adsorption of these molecules onto the steel surface was consistent with the Langmuir isotherm model, suggesting physical and chemical interaction. SEM analysis confirmed the protective layer formation by 1,4-Benzothiazine derivatives. Additionally, Quantum Chemical Calculations and Molecular Dynamics simulations provided insights into their interaction mechanisms on the Fe(110) surface. This research highlights the potential of 1,4-Benzothiazine derivatives in corrosion protection and paves the way for their further development

Nanocellulose fibers: A Review of Preparation Methods, Characterization Techniques, and Reinforcement Applications

Cellulose, which occurs naturally in abundance, has the benefit of being the most widely used biomass material on a global scale. It is generated from natural fibers and can be processed to produce various types of nanocellulose fibers, each with its hierarchical configuration. This review summarizes current advances in the production of nanocellulose particles, focusing on the analytical techniques most widely used for their preparation, extraction, and characterization. These techniques include FT-IR, TGA, FESEM, and XRD. The review also demonstrates that research into nanocellulose fibers has progressed exponentially over the last decade (over 400 references). Many manufacturing techniques have been developed to use nanofibers in multiple applications as advanced sustainable materials. The presented data will reinforce the applications of nanocellulose fibers for various purposes

Orbital Interaction Mechanisms of Conductance Enhancement and Rectification by Dithiocarboxylate Anchoring Group

We study computationally the electron transport properties of dithiocarboxylate terminated molecular junctions. Transport properties are computed self-consistently within density functional theory and nonequilibrium Green's functions formalism. A microscopic origin of the experimentally observed current amplification by dithiocarboxylate anchoring groups is established. For the 4,4'-biphenyl bis(dithiocarboxylate) junction, we find that the interaction of the lowest unoccupied molecular orbital (LUMO) of the dithiocarboxylate anchoring group with LUMO and highest occupied molecular orbital (HOMO) of the biphenyl part results in bonding and antibonding resonances in the transmission spectrum in the vicinity of the electrode Fermi energy. A new microscopic mechanism of rectification is predicted based on the electronic structure of asymmetrical anchoring groups. We show that the peaks in the transmission spectra of 4'-thiolato-biphenyl-4-dithiocarboxylate junction respond differently to the applied voltage. Depending upon the origin of a transmission resonance in the orbital interaction picture, its energy can be shifted along with the chemical potential of the electrode to which the molecule is more strongly or more weakly coupled

Large magnetoresistance by Pauli blockade in hydrogenated graphene

We report the observation of a giant positive magnetoresistance in millimetre scale hydrogenated graphene with magnetic field oriented in the plane of the graphene sheet. A positive magnetoresistance in excess of 200\% at a temperature of 300 mK was observed in this configuration, reverting to negative magnetoresistance with the magnetic field oriented normal to the graphene plane. We attribute the observed positive, in-plane, magnetoresistance to Pauli-blockade of hopping conduction induced by spin polarization. Our work shows that spin polarization in concert with electron-electron interaction can play a dominant role in magnetotransport within an atomic monolayer.Comment: 6 pages, 3 figures, and supplemental informatio