Cathodic activation of synthesized highly defective monoclinic hydroxyl-functionalized ZrO2 nanoparticles for efficient electrochemical production of hydrogen in alkaline media

The high electrochemical stability of Zirconia (ZrO₂) at high potentials strongly suggested it as an alternative to carbon supports, which experience reduced efficiency due to some corrosion problems particularly during prolonged electrocatalysis activity. However, the use of ZrO₂ was limited by its low electrical conductivity and surface area. In this work, we developed a methodology for synthesizing monoclinic ZrO₂ NPs with increased surface area and improved electrical/electrocatalytic characteristics without using any carbon-based co-support material or any metallic nanoparticles. In this context, for the first time, highly defective hydroxyl-functionalized ZrO₂ NPs (designated here as ZT NPs) were prepared by a hydrothermal route in the presence of sodium tartrate as a mineralizer. XRD analysis demonstrated that the produced zirconia was semicrystalline microspheres, consisting of monoclinic ZrO₂ NPs with high lattice defects. The addition of tartrate ions decreased the crystallite size and increased the defects and microstrain. At the same time, the alkaline hydrogen evolution reaction (HER) catalytic activity of ZrO₂ NPs was significantly increased when using sodium tartrate as mineralizer; the overpotential required to obtain 10 mA cm⁻² (η₁₀) dropped down from 490 to merely 235 mV, while an exchange current density (j_o) increased 12 times to 0.22 mA cm⁻². The presence of structural defects (revealed by XRD) and the increased number of active surface sites contending O-H groups (evidenced from ATR-FTIR and XPS) as well as the enhanced electrochemical active surface area (confirmed from double-layer capacitance measurements) were the main reasons behind the high catalytic performance. The ZrO₂ NPs catalytic activity increased even further during the long-term stability tests under severe cathodic conditions (ZT*, ZrO₂ NPs obtained after the long-term stability, has j_o = 0.47 mA cm⁻² and η₁₀ = 140 mV), approaching the activity of Pt/C catalyst. This process was assisted by mineralizer removal from the catalyst (testified by XPS). Our studies revealed that ZT* are characterized by larger electroactive surface area and more structure defects compared to ZT, where surface area and microstrains resulting from surface hydroxylation open cavities in zirconia structure.     

On optimal trajectory for the multi-period evolution of FTTx networks

Telecommunication Systems - We propose a business/cost model for long-period changes of customer demands in FTTx networks. We show how to exploit this model in the formulation of a MIP optimization...     

Thermopower Study of GaN-Based Materials for Next-Generation Thermoelectric Devices and Applications

III-nitride InGaN-based solar cells have gained importance because their band gap can potentially cover most of the solar spectrum, spanning 0.7 eV to 3.4 eV. However, to use these materials to harvest additional energy, other properties such as their thermoelectric properties should be exploited. In this work, the Seebeck coefficient and the electrical conductivity of three InGaN alloys with various indium concentrations and Gd-doped GaN (GaN:Gd) were measured, and the power factor was calculated. We report a Seebeck value of ∼209 μV/K for Gd-doped GaN.     

Preparation and electrochemical properties of sodium-reduced graphene oxide

Graphite oxide reduction is probably one of the best technique used to obtain large quantities of few-layer graphene. We developed a new method to produce reduced graphene oxide by using sodium metal as a reducing agent with subsequent dehydration in concentrated sulfuric acid. The resulting product was characterized using various analytical techniques with respect to the oxygen content and species of the residual oxygen-containing groups. The reduced graphene oxide prepared by this method was electrochemically tested as electrode in supercapacitors using two-electrode symmetric system and aqueous electrolyte. The product exhibits improved capacitance during cyclic voltammetry measurements. In comparison to parent graphite oxide specific capacity increased from 0.88 to 28 F/g after 10 cycles at scan rate 20 mV/s and dropped to 19.44 F/g after 100 cycles while at scan rate 5 mV/s specific capacity 46.41 F/g was recorded after first cycle and 39.90 F/g after 50 cycles.     

Development and Characterization of the Injection-Molded Polymer Composites Made from Bicomponent Fibers

The results of this study are related to the implementation of the concept of self-reinforced composites. The input materials in preparation process were the bicomponent fibers. The studies were carried out on three types of fibers, HDPE/PP, cPP/PP, LPET/PET. In each case, the matrix material was a low melting polymer, and the core was made of a higher melting point polymer. The research was conducted for the materials shaped by an injection-molding technique. The analyses confirmed the two-component structure. Properties of the resulting composites confirmed the applicability of bicomponent fibers in the preparation of self-reinforced composites.     

Continuous flow thermal cycler microchip for DNA cycle sequencing

We report here on the use of a polymer-based continuous flow thermal cycler (CFTC) microchip for Sanger cycle sequencing using dye terminator chemistry. The CFTC chip consisted of a 20-loop spiral microfluidic channel hot-embossed into polycarbonate (PC) that had three well-defined temperature zones poised at 95, 55, and 60 degrees C for denaturation, renaturation, and DNA extension, respectively. The sequencing cocktail was hydrodynamically pumped through the microreactor channel at different linear velocities ranging from 1 to 12 mm/s. At a linear velocity of 4 mm/s resulting in a 36-s extension time, a read length of >600 bp could be obtained in a total reaction time of 14.6 min. Further increases in the flow rate resulted in a reduction in the total reaction time but also produced a decrease in the sequencing read length. The CFTC chip could be reused for subsequent sequencing runs (>30) with negligible amounts of carryover contamination or degradation in the sequencing read length. The CFTC microchip was subsequently coupled to a solid-phase reversible immobilization (SPRI) microchip made from PC for purification of the DNA sequencing ladders (i.e., removal of excess dye-labeled dideoxynucleotides, DNA template, and salts) prior to gel electrophoresis. Coupling of the CFTC chip to the SPRI microchip showed read lengths similar to that obtained from benchtop instruments but did not require manual manipulation of the cycle sequencing reactions following amplification.     

Merkel Cell Carcinoma from Molecular Pathology to Novel Therapies

Merkel cell carcinoma (MCC) is an uncommon and highly aggressive skin cancer. It develops mostly within chronically sun-exposed areas of the skin. MCPyV is detected in 60–80% of MCC cases as integrated within the genome and is considered a major risk factor for MCC. Viral negative MCCs have a high mutation burden with a UV damage signature. Aberrations occur in RB1, TP53, and NOTCH genes as well as in the PI3K-AKT-mTOR pathway. MCC is highly immunogenic, but MCC cells are known to evade the host’s immune response. Despite the characteristic immunohistological profile of MCC, the diagnosis is challenging, and it should be confirmed by an experienced pathologist. Sentinel lymph node biopsy is considered the most reliable staging tool to identify subclinical nodal disease. Subclinical node metastases are present in about 30–50% of patients with primary MCC. The basis of MCC treatment is surgical excision. MCC is highly radiosensitive. It becomes chemoresistant within a few months. MCC is prone to recurrence. The outcomes in patients with metastatic disease are poor, with a historical 5-year survival of 13.5%. The median progression-free survival is 3–5 months, and the median overall survival is ten months. Currently, immunotherapy has become a standard of care first-line therapy for advanced MCC.