Paraffin-Multilayer Graphene Composite for Thermal Management in Electronics.

Multilayer graphene-paraffin composites with different contents of graphene (0-10 wt.%) were prepared using an ultra-high shear mixer. The aim is to improve the heat transfer in paraffin wax, which will lead to more-efficient thermal buffering in electronic applications. The multi-layer graphenes obtained by supercritical fluid exfoliation of graphite in alcohol were investigated by Raman spectroscopy, scanning electron microscopy and atomic force microscopy. Interesting morphological features were found to be related to the intercalation of paraffins between the multilayer graphene flakes. Thermal properties were also investigated in terms of phase change transition temperatures, latent heat by differential scanning calorimetry and thermal conductivity. It was found that the addition of graphene resulted in a slight decrease in energy storage capacity but a 150% improvement in thermal conductivity at the highest graphene loading level. This phase-change material is then used as a thermal heat sink for an embedded electronic processor. The temperature of the processor during the execution of a pre-defined programme was used as a performance indicator. The use of materials with multilayer graphene contents of more than 5 wt.% was found to reduce the processor operating temperature by up to 20%. This indicates that the use of such composite materials can significantly improve the performance of processors.

Carbon-Nanowall Microporous Layers for Proton Exchange Membrane Fuel Cell.

The cathode microporous layer (MPL), as one of the key components of the proton exchange membrane fuel cell (PEM-FC), requires specialized carbon materials to ensure the two-phase flow and interfacial effects. In this respect, we designed a novel MPL based on highly hydrophobic carbon nanowalls (CNW). Employing plasma-assisted chemical vapor deposition techniques directly on carbon paper, we produced high-quality microporous layers at a competitive yield-to-cost ratio with distinctive MPL properties: high porosity, good stability, considerable durability, high hydrophobicity, and substantial conductivity. The specific morphological and structural properties were determined by scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Thermo-gravimetric analysis was employed to study the nanostructures' thermal stability and contact angle measurements were performed on the CNW substrate to study the hydrophobic character. Platinum ink, serving as a fuel cell catalyst, was sprayed directly onto the MPLs and incorporated in the FC assembly by hot-pressing against a polymeric membrane to form the membrane-electrode assembly and gas diffusion layers. Single-fuel-cell testing, at moderate temperature and humidity, revealed improved power performance comparable to industrial quality membrane assemblies (500 mW cm-2 mg-1 of cathodic Pt load at 80 °C and 80% RH), with elevated working potential (0.99 V) and impeccable fuel crossover for a low-cost system.

Heart Transplantation, Either Alone or Combined With Liver and Kidney, a Viable Treatment Option for Selected Patients With Severe Cardiac Amyloidosis.

Heart transplantation in cardiac amyloidosis (CA) patients is possible and generally considered for transplantation if other organs are not affected. In this study, we aimed to describe and assess outcome in patients following heart transplantations at our CA referral center. Methods: We assessed all CA patients that had heart transplantations at our center between 2005 and 2018. Patients with New York Heart Association status 3 out of 4, with poor short-term prognosis due to heart failure, despite treatment, and without multiple myeloma, systemic disease, severe neuropathic/digestive comorbidities, cancer, or worsening infections were eligible for transplantation. Hearts were transplanted by bicaval technique. Standard induction and immunosuppressive therapies were used. Survival outcome of CA patients after transplantation was compared with recipients with nonamyloid pathologies in France. Results: Between 2005 and 2018, 23 CA patients had heart transplants: 17 (74%) had light chain (light chain amyloidosis [AL]) and 6 (26%) had hereditary transthyretin (hereditary transthyretin amyloidosis [ATTRv]) CA. Also, 13 (57%) were male, and the mean age at diagnosis was 56.5 y (range, 47.7-62.8). Among AL patients, 13 had heart-only and 5 had heart-kidney transplantations. Among ATTRv patients, 1 had heart-only and 5 had heart-liver transplantations. The 1-y survival rate after transplantation was 78%, 70% with AL, and 100% with ATTRv. At 2 y, 74% were alive: 65% with AL and 100% with ATTRv. Conclusion: After heart transplantation, French CA and nonamyloid patients have similar survival outcomes. Among CA patients, ATTRv patients have better prognosis than those with AL, possibly due to the combined heart-liver transplantation. Selected CA patients should be considered for heart transplantations.

Hybrid Proton-Exchange Membrane Based on Perfluorosulfonated Polymers and Resorcinol-Formaldehyde Hydrogel.

Organic resorcinol-formaldehyde (RF) hydrogels were introduced into a hybrid cation-exchange membrane in order to enhance its following properties: water uptake, thermal stability, and ionic conductivity. This study was aimed to investigate the modifications induced by the RF organic clusters that form a uniform distributed network within the perflourosulfonated acid (PFSA) matrix. RF concentration was controlled by resorcinol and formaldehyde impregnation time using water or ethanol solvents. The specific morphological and structural properties were characterized by atomic force microscopy, UV-Vis, and Fourier transform infrared spectroscopy. Thermo-gravimetric analysis was employed to study the thermal stability and degradation processes of the composite membranes. Proton conductivity, as a function of relative humidity (RH) at 80 °C, was measured using in-plane four-point characterization technique. Compared to the pristine membrane, the PFSA-RF hybrid membranes showed improved thermal stability at up to 46 °C and higher ionic conductivity for low RF content, especially at low relative humidity, when using ethanol-based solvents. Single fuel cell testing on RF-based membrane-electrode assembly revealed impeccable fuel crossover and power performance at 80 °C and 40% relative humidity, delivering a 76% increase in power density compared to a reference assembled with a pristine membrane and the same catalyst loadings.

Stainless Steel Surface Nitriding in Open Atmosphere Cold Plasma: Improved Mechanical, Corrosion and Wear Resistance Properties.

This work presents preliminary results regarding improving the mechanical, wear and protective properties (hardness, coefficient of friction, corrosion resistance) of AISI 304 stainless steel surfaces by open atmosphere cold plasma surface treatment method. Comparative evaluations of the morphological, corrosion resistance, mechanical and tribological properties for different periods of treatment (using N2 gas for cold plasma generation in an open atmosphere) were performed. AFM surface analyses have shown significant surface morphology modifications (average roughness, FWHM, surface skewness and kurtosis coefficient) of the treated samples. An improved corrosion resistance of the N2 treated surfaces in open atmosphere cold plasma could be observed using electrochemical corrosion tests. The mechanical tests have shown that the surface hardness (obtained by instrumented indentation) is higher for the 304 stainless steel samples than it is for the un-treated surface, and it decreases gradually for higher penetration depths. The kinetic coefficient of friction (obtained by ball-on-disk wear tests) is significantly lower for the treated samples and increases gradually to the value of the un-treated surface. The low friction regime length is dependent on the surface treatment period, with a longer cold plasma nitriding process leading to a significantly better wear behavior.

Preparation and Characterization of Silica Nanoparticles and of Silica-Gentamicin Nanostructured Solution Obtained by Microwave-Assisted Synthesis.

In this research work, silica nanoparticles and silica-gentamicin nanostructured solution were synthesized by using the microwave-assisted synthesis, in basic medium, using two silane precursors (tetraethylorthosilicate and octyltriethoxysilane) and the antibiotic (gentamicin sulfate). The prepared materials were characterized through Fourier transform infrared (FTIR) spectroscopy, TGA analysis, transmission electron microscopy (TEM), and atomic force microscopy (AFM) to investigate the morphology and structure. Antimicrobial studies of the silica-gentamicin nanostructured solution versus silica nanoparticles were performed against Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli. FTIR spectra showed that the gentamicin has been loaded to the silica nanoparticles. AFM analysis showed that the morphology of the silica-gentamicin nanostructured solution has changed, and agglomerations of particles are present at the surface. Antimicrobial testing, performed using the diffusion method through spot inoculation, indicates that the silica-gentamicin nanostructured solution exhibited activity against the resistant strain. The obtained silica-gentamicin solution can be used as biochemical agent for the prevention and treatment of microorganisms which are deposited on different surfaces (e.g., glass, plastic, ceramic).

Exploring the Conformation and Thermal Stability of Human Serum Albumin Corona of Ferrihydrite Nanoparticles.

In the last few years, a great amount of attention has been given to nanoparticles research due to their physicochemical properties that allow their use in analytical instruments or in promising imaging applications on biological systems. The use of ferrihydrite nanoparticles (Fh-NPs) in practical applications implies a particular control of their magnetic properties, stability, biocompatibility, interaction with the surface of the target, and low toxicity. In this study, the formation and organization of human serum albumin (HSA) molecules around the simple Fh-NPs and Fh-NPs doped with Co and Cu were examined by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) in terms of morphology and particle size. The topology of all Fh-NPs shows an organized area of HSA around each type of Fh-NP. Molecular docking studies were used in order to determine the probable location of the ferrihydrite in the HSA structure. The thermal stability of these nanohybrids was further investigated by fluorimetry, using 214-Trp residue from HSA as a spectral sensor. The denaturation temperature (Tm) was determined, and stabilization of the HSA structure in the presence of Fh-NPs was discussed. This study could be a starting point for the development of different applications targeting the structure and stability of Fh-NPs complexes with proteins.

X-ray Structure Elucidation of a Pt-Metalloporphyrin and Its Application for Obtaining Sensitive AuNPs-Plasmonic Hybrids Capable of Detecting Triiodide Anions.

The development of UV⁻vis spectrophotometric methods based on metalloporphyrins for fast, highly sensitive and selective anion detection, which avoids several of the practical challenges associated with other detection methods, is of tremendous importance in analytical chemistry. In this study, we focused on achieving a selective optical sensor for triiodide ion detection in traces based on a novel hybrid material comprised of Pt(II) 5,10,15,20-tetra(4-methoxy-phenyl)-porphyrin (PtTMeOPP) and gold nanoparticles (AuNPs). This sensor has high relevance in medical physiological tests. The structure of PtTMeOPP was investigated by single crystal X-ray diffraction in order to understand the metal surroundings and the molecule conformation and to assess if it qualifies as a potential sensitive material. It was proven that the Pt-porphyrin generated 1D H-bond supramolecular chains due to the weak C-H···O intermolecular hydrogen bonding. The presence of ordered voids in the crystal encouraged us to use PtTMeOPP as the sensing material for triiodide ion and to enhance its potential in a novel AuNPs/PtTMeOPP hybrid by the synergistic effects provided by the plasmonic gold nanoparticles. The spectrophotometric sensor is characterized by a detection limit of 1.5 × 10-9 M triiodide ion concentration and a remarkable confidence coefficient of 99.98%.

Morphological and Structural Analysis of Polyaniline and Poly(o-anisidine) Layers Generated in a DC Glow Discharge Plasma by Using an Oblique Angle Electrode Deposition Configuration.

This work is focused on the structural and morphological investigations of polyaniline and poly(o-anisidine) polymers generated in a direct current glow discharge plasma, in the vapors of the monomers, without a buffer gas, using an oblique angle-positioned substrate configuration. By atomic force microscopy and scanning electron microscopy we identified the formation of worm-like interlinked structures on the surface of the polyaniline layers, the layers being compact in the bulk. The poly(o-anisidine) layers are flat with no kind of structures on their surfaces. By Fourier transform infrared spectroscopy we identified the main IR bands characteristic of polyaniline and poly(o-anisidine), confirming that the polyaniline chemical structure is in the emeraldine form. The IR band from 1070 cm-1 was attributed to the emeraldine salt form of polyaniline as an indication of its doping with H⁺. The appearance of the IR band at 1155 cm-1 also indicates the conducting protonated of polyaniline. The X-ray diffraction revealed the formation of crystalline domains embedded in an amorphous matrix within the polyaniline layers. The interchain separation length of 3.59 Šis also an indicator of the conductive character of the polymers. The X-ray diffraction pattern of poly(o-anisidine) highlights the semi-crystalline nature of the layers. The electrical conductivities of polyaniline and poly(o-anisidine) layers and their dependence with temperature are also investigated.

A PRELIMINARY EVALUATION OF RESIDENTS' PERCEPTION OF THEIR TRAINING AND KNOWLEDGE ON THREE-DIMENSIONAL IMAGING.

UNLABELLED: The aim of this preliminary study was to assess the residents' perception on their training program and on their knowledge regarding the use and interpretation of three-dimensional imaging techniques in their clinical practice. MATERIAL AND METHODS: A multi-item questionnaire was distributed among 104 residents training in four medical specialties at the University of Medicine and Pharmacy "Grigore T. Popa" in Iasi. RESULTS: Fifty-five residents agreed to fill in the questionnaire, achieving a participating rate of 52.88%. The majority of the respondents (74.5%) declared to indicate classic CT scans to their patients. A significantly lower fraction of the participating residents (32.7%) affirmed to indicate CBCT scans. Electronic literature was the most common information source on the use of three-dimensional imaging (52.7%). Most of the residents declared that they cannot interpret correctly CT and CBCT scans (78.2%, respectively 83.6%). A significant percentage of the respondents considered that the level of training provided on the interpretation of CT and CBCT results is very low (49.1%, respectively 60.0%). CONCLUSIONS: The residents' perception of the quality of their education regarding 3D imaging modalities, along with their perception of their knowledge in this area, indicates the necessity to improve their didactic and practical training. A further extended survey will be conducted to evaluate the educational experience of residents from all medical specialties that use 3D imaging techniques in neck and head imaging.

Assessment of the consequences in premature loss of the temporary lower molars.

The consequences of premature loss of temporary teeth are complex, both of functional and morphological order and the clinical presentation depends on multiple factors: the temporary tooth loss rate as compared with permanent tooth eruption sequence and the number and topography of teeth extracted, so the clinical form of edentulous, which can be frontal or lateral, symmetric or asymmetric, isolated or continuous.

Considerations on the epidemiology, etiology and profile of periodontal--dental injuries in preschool population in Iasi county.

UNLABELLED: In recent years there has been a considerable increase in the number of temporary teeth injuries, this variability being determined by multiple etiologic factors, which we need to be aware of, as well as by predisposing conditions. AIM: To characterize the epidemiology, etiology and pathology of specific types of periodontal-dental trauma in a series of preschool children from Iasi County. MATERIAL AND METHODS: The study included a total of 672 subjects aged 3 to 7 years old, from both urban and rural areas of Iasi County. Statistical analysis was performed using STATISTICA software used in medical research. RESULTS: Prevalence of periodontal-dental trauma in the study group was 19.64%. Gender distribution in the study group showed a preponderance of males (62.12%). The risk of periodontal-dental trauma in deciduous teeth was 1.63 times higher in boys compared to girls. Fall accidents (41.67%) closely followed by playground accidents (31.82%) were the most common causes of periodontal-dental trauma in the study group. CONCLUSIONS: The prevalence of temporary dental trauma in the study group was relatively high, requiring the implementation of oral health promotion strategies and prevention programs, primarily addressed to parents and educators.

Preventive attitudes towards infection transmission in dental offices in North-East Romania.

AIM: The aim of this study was to evaluate the level of knowledge and the current attitudes towards infection control in the dental offices in the Northeast Romania. MATERIAL AND METHODS: Questionnaire-based study conducted on 152 dentists aged between 25-65 years practicing in 6 Northeast Romania counties. The questionnaire included questions related to current infection control procedures and attitudes. Data were statistically analyzed using SPSS 14.0 and chi-square test (p<0.05). RESULTS: The majority of the dentists (83.6%) consider that universities should provide a substantial education regarding infection control through postgraduate courses, but 7.2% of the respondents are not sure about their usefulness. The clinical decision related to patient's treatment is influenced by his infectious status for 67.8% of the dentists. Of these, 19.1% have over 20 years of practice and 48.0% are females. Almost all dentists (93.4%), regardless of gender (96.4% females and 87.8% males) undergo periodic testing for blood-borne viral infections (hepatitis B, C and HIV). Full protective equipment is used for all the patients by 86.2% of the dentists, while 12.5% use it only for the infectious ones. 65.2% of the dentists use steam sterilization equipment (autoclave), and 80,8% use dry heat. The majority of the dentists (82.6%) believe that the patient must always be informed about the adopted infection control measures, but 21.7% declare to do so only in some particular cases. CONCLUSIONS: Dentists knowledge and attitudes towards infection control must be improved by educational interventions in order to adhere to the European standards.