Impact of a Graphene Oxide Reducing Agent on a Semi-Permeable Graphene/Reduced Graphene Oxide Forward Osmosis Membrane Filtration Efficiency.

Graphene has been considered as a material that may overcome the limitations of polymer semi-permeable membranes in water treatment technology. However, monolayer graphene still suffers from defects that cause leakage. Here, we report a method of sealing defects in graphene transferred onto porous polymer substrate via reduced graphene oxide (rGO). The influence of various reducing agents (e.g., vitamin C, hydrazine) on the properties of rGO was investigated by SEM, Raman, FTIR, and XRD. Subsequently, membranes based on graphene/reduced graphene oxide were tested in a forward osmosis system using sodium chloride (NaCl). The effect of the effectiveness of the reduction of graphene oxide, the type and number of attached groups, the change in the distance between the rGO flakes, and the structure of this material were examined in terms of filtration efficiency. As a result, semi-permeable centimetre-scale membranes with ion blocking efficiency of up to 90% and water flux of 20 mL h-1 m-2 bar-1 were proposed.

Emerging Technology for a Green, Sustainable Energy-Promising Materials for Hydrogen Storage, from Nanotubes to Graphene-A Review.

The energetic and climate crises should pose a challenge for scientists in finding solutions in the field of renewable, green energy sources. Throughout more than two decades, the search for new opportunities in the energy industry made it possible to observe the potential use of hydrogen as an energy source. One of the greatest challenges faced by scientists for the sake of its use as an energy source is designing safe, usable, reliable, and effective forms of hydrogen storage. Moreover, the manner in which hydrogen is to be stored is closely dependent on the potential use of this source of green energy. In stationary use, the aim is to achieve high volumetric density of the container. However, from the point of view of mobile applications, an extremely important aspect is the storage of hydrogen, using lightweight tanks of relatively high density. That is why, a focus of scientists has been put on the use of carbon-based materials and graphene as a perspective solution in the field of H2 storage. This review focuses on the comparison of different methods for hydrogen storage, mainly based on the carbon-based materials and focuses on efficiently using graphene and its different forms to serve a purpose in the future H2-based economy.

Optimization of Glutathione Adhesion Process to Modified Graphene Surfaces.

The presented work shows the results of the functionalization of the graphene surface obtained by the growth on the liquid bimetallic matrices method. We used glutathione (GSH) as a peptide model, which allowed us to optimize the procedure to obtain high process efficiency. To establish the amount of GSH attached to the graphene surface, the Folina-Ciocalteu method was used, which allows the assessment of the concentration of colored reaction products with peptide bonds without the disadvantages of most methods based on direct colored reaction of peptide bonds. Samples surface morphology, quality of graphene and chemical structure in the subsequent stages of surface modification were tested-for this purpose Raman spectroscopy, scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) were used.

Quasi-Monocrystalline Graphene Crystallization on Liquid Copper Matrix.

To access the properties of theoretical graphene, it is crucial to manufacture layers with a defect-free structure. The imperfections of the structure are the cause of deterioration in both electrical and mechanical properties. Among the most commonly occurring crystalline defects, there are grain boundaries and overlapping zones. Hence, perfect graphene shall be monocrystalline, which is difficult and expensive to obtain. An alternative to monocrystalline structure is a quasi-monocrystalline graphene with low angle-type boundaries without the local overlapping of neighboring flakes. The purpose of this work was to identify factors that directly affect the structure of graphene grown on a surface of a liquid metal. In the article the growth of graphene on a liquid copper is presented. Nucleating graphene flakes are able to move with three degrees of freedom creating low-angle type boundaries when they attach to one another. The structure of graphene grown with the use of this method is almost free of overlapping zones. In addition, the article presents the influence of impurities on the amount of crystallization nuclei formed, and thus the possibility to order the structure, creating a quasi-monocrystalline layer.

Influence of the Interactions at the Graphene-Substrate Boundary on Graphene Sensitivity to UV Irradiation.

Graphene is a very promising material for electronics applications. In recent years, its sensitivity to ultraviolet (UV) irradiation has been studied extensively. However, there is no clear answer to the question, which factor has a key influence on the sensitivity of graphene to UV. In order to check the influence of the final substrate on the electrical response, graphene transferred on polymeric and non-polymeric substrate was investigated. To achieve this goal three polymeric and three non-polymeric substrates were tested. The results of the preliminary tests indicated the different character of the reaction on UV irradiation in each of group. To explain the reason of the difference, the complementary studies were done. The samples that were resistant to high temperature were annealed in a vacuum at 500 °C to get rid of water trapped between graphene and the substratum. The samples after annealing reacted less dynamically to UV irradiation. Moreover, the progress of changes in electrical response of the annealed samples had a similar character to the polymeric substrates, with the hydrophobic nature of the surface. These studies clearly prove that the sensitivity of graphene to UV irradiation is influenced by water trapped under the graphene.

A Fully Transparent Flexible Sensor for Cryogenic Temperatures Based on High Strength Metallurgical Graphene.

Low-temperature electronics operating in below zero temperatures or even below the lower limit of the common -65 to 125 °C temperature range are essential in medical diagnostics, in space exploration and aviation, in processing and storage of food and mainly in scientific research, like superconducting materials engineering and their applications-superconducting magnets, superconducting energy storage, and magnetic levitation systems. Such electronic devices demand special approach to the materials used in passive elements and sensors. The main goal of this work was the implementation of a fully transparent, flexible cryogenic temperature sensor with graphene structures as sensing element. Electrodes were made of transparent ITO (Indium Tin Oxide) or ITO/Ag/ITO conductive layers by laser ablation and finally encapsulated in a polymer coating. A helium closed-cycle cryostat has been used in measurements of the electrical properties of these graphene-based temperature sensors under cryogenic conditions. The sensors were repeatedly cooled from room temperature to cryogenic temperature. Graphene structures were characterized using Raman spectroscopy. The observation of the resistance changes as a function of temperature indicates the potential use of graphene layers in the construction of temperature sensors. The temperature characteristics of the analyzed graphene sensors exhibit no clear anomalies or strong non-linearity in the entire studied temperature range (as compared to the typical carbon sensor).

Free and bioavailable fractions of sex steroids may influence bones in young men, depending on age and oestradiol level.

INTRODUCTION: Longitudinal bone growth ceases by the end of puberty, and it is thought to be a result, in both sexes, of increased pubertal oestrogen serum concentrations. Since peak bone mass is achieved by the third decade of life or later, the aim of this study was to relate sex steroid hormones and sex hormone binding globulin (SHBG) levels to bone quality in men during their third and fourth decades of life. MATERIAL AND METHODS: Eighty men, healthy volunteers aged between 18 and 39 years, were subjected to an interviewer-administered questionnaire, body mass index (BMI) measurement, blood sample and calcaneal quantitative ultrasound (QUS) (Hologic-SAHARA). Blood was assessed for testosterone (T), oestradiol (E2), dehydroepiandrosterone sulfate (DHEAS), SHBG, luteinising hormone (LH) and follicle stimulating hormone (FSH). Free and bioavailable T and E2 levels were calculated knowing SHBG and albumin levels. RESULTS: While T, E2, DHEAS, LH and FSH levels were not related, free and bioavailable fractions of T and E2 were positively associated with QUS readings. SHBG level was associated negatively. After dichotomisation for age, the associations remained significant only for younger subjects (18-30 years, n = 47). After adjustment for other co-variants, only SHBG in younger subjects retained its negative association with QUS. Older subjects (31-39 years, n = 33) revealed higher BMI and lower serum concentrations of total (-17 %), free (-18.5%) and bioavailable (-22.5%) levels of E2 than younger subjects. CONCLUSION: Free and bioavailable fractions of sex steroids may influence bones in young men, depending on age and E2 level.

Endogenous Estradiol and Testosterone may Predispose toward Atherogenic Lipid Profile, but Higher Blood Level of Testosterone is Associated with Lower Number of Stenoses in the Coronary Arteries of Men with Coronary Disease.

OBJECTIVES: To assess the correlations between blood levels of sex steroid hormones and blood lipid profile or the degree of coronary artery stenosis in men with coronary artery disease (CAD). METHODS: 111 men with stable CAD, aged 36-73 yrs, unselected for the coexisting clinical coronary risk factors were prospectively studied. Degree of coronary stenosis was assessed angiographically using different indices. Total cholesterol (T-Ch), high density lipoproteins cholesterol (HDL-Ch), low density lipoproteins cholesterol (LDL-Ch), triglicerydes (TG), testosterone, estradiol, dehydroepiandrosterone sulfate (DHEA-S), and sex hormone binding globulin (SHBG) were measured in the blood. Free testosterone index (FTI) was calculated. RESULTS: A positive, significant correlations were found between blood concentrations of estradiol and T-Ch (r=0.29, p<0.01) or LDL-Ch (r=0.34, p<0.005) as well as between FTI and blood LDL-Ch (r=0.23, p<0.05). Blood level of estradiol negatively correlated with HDL-Ch/T-Ch ratio (r=-0.21, p<0.05). While blood levels of T-Ch correlated positively with 3 out of 5 applied here indices of coronary stenosis, blood LDL-Ch with two of them. In turn, blood level of testosterone negatively correlated with one index of coronary stenosis (r=-0.26, p<0.05). CONCLUSION: In men with CAD, plasma estradiol concentrations are predictive for T-Ch, LDL-Ch and HDL-Ch/TCh ratio, and FTI for LDL-Ch. Regression analyses indicated that while sex steroid hormones may predispose toward atherogenic lipid profile and are predictive for the number and degree of coronary artery stenosis, higher blood level of total testosterone was associated with the lower number of stenosis in the coronary arteries. Hence, endogenous testosterone may have beneficial effect on coronary arteries.

[Physiological significance of estrogens in men--breakthrough in endocrinology]. / Znaczenie fizjologiczne estrogenów u mezczyzn--przelom w endokrynologii.

Estradiol (E2) is traditionally recognised as the female sex hormone. It has been believed for 40 years, that E2 didn't exert any influence or caused impairment of the gonadal function in men. The main source of E2 in men is adipose tissue and the brain. E2 is also produced in adrenals, liver, mammary glands, hair and in male gonad. Daily production and the level of E2 in the blood in men are higher than those in postmenopausal women. At the end of the 80-ties we were first reporting that during sexual maturation E2 can be the important hormonal signal for the initiation of spermatogenesis. The traditional view about unimportant or inhibitory role of E2 in male physiology was finally refuted thanks to discovering estrogen receptors in males. In the 90-ties, transgenic mice with the lack of estrogen receptor (ER) or gene encoding enzyme aromatase, that enable the conversion of testosterone into E2, were also produced. Observations of men with inherited mutations of these genes, considerably extended our knowledge about E2 in men in stroma bones formation, inhibition of their growing, lipids metabolism and sexual maturation, the effects that were attributed to testosterone action until today. New data also points at important role of estrogens and ER in the function of the cardio-vascular system and in counteracting coronary disease in men.

The relationship between sex hormones and lipid profile in men with coronary artery disease.

BACKGROUND: Men are more prone to develop coronary artery disease (CAD) than women and the mechanism of this different susceptibility is not well elucidated. The aim of this study was to evaluate the relationship between serum levels of several sex hormones and serum levels of lipoproteins, as well as the association between sex hormones and clinical covariates in men with stable coronary artery disease. METHODS: Study population consisted of 111 men (mean age 55 years) with stable coronary artery disease. In all patients levels of testosterone, dehydroepiandrosterone sulfate (DHEA-S), estradiol, sex hormone binding globuline (SHBG), luteinizing hormone (LH) and follicle stimulating hormone (FSH) were measured and free testosterone index (FTI) was calculated knowing SHBG. Standard lipid analysis included total cholesterol, HDL-cholesterol, LDL-cholesterol, and triglycerides. The extent of coronary artery disease was defined using semiquantitative coronary angiography score. RESULTS: Significant positive correlations were found between estradiol levels and levels of total cholesterol (r = 0.31; p = 0.005), LDL-cholesterol (r = 0.32; p=0.004), total cholesterol/HDL ratio (r = 0.26; p = 0.020), and triglycerides (r = 0.24; p = 0.030), whereas no significant association was found between levels of these lipids and testosterone or DHEA levels. HDL cholesterol showed a significant association with levels of FSH (r = 0.23; p = 0.03) and LH (r = 0.25; p = 0.02). CONCLUSIONS: Our results indicate a possible role of estradiol in promoting the development of atherogenic lipid milieu in men with CAD. Simultaneously, the observed association between increased FSH and LH levels with increased levels of HDL cholesterol might suggest a protective effect of these hormones.

[Important functions of estrogens in men--breakthrough in contemporary medicine]. / Wazne funkcje estrogenów u mezczyzn--przelom we wspóczesnej medycynie.

Estradiol (E2) is traditionally recognised as the female sex hormone. Since discovery of estrogens in the early forties of XX century it has been believed, that these hormones caused impairment of the gonadal function in men or didn't exert any influence. New studies are contradictory, but indicate also a possible involvement of estrogens in the pathogenesis of some systemic diseases of men. The main source of E2 in men is adipose tissue and the brain. E2 is also produced in adrenals, liver, mammary glands, hair and in male gonads. Daily production and blood level of E2 in men are higher than those in postmenopausal women. In 1988 we were the first to demonstrate that E2 is an important hormonal signal for initiation of spermatogenesis. The traditional view about unimportant or inhibitory role of E2 in male physiology was finally refuted thanks to discovery of the estrogen receptors in males. In the middle 90ties transgenic mice with the lack of estrogen receptor (ER knockout) or enzyme aromatase, that enable the conversion of testosterone into E2, were produced. Observations of men with inherited mutations of these genes, considerably extended our knowledge about stimulatory role of E2 in men in the formation of bone stroma, inhibition of their linear growth, lipids metabolism and sexual maturation, the effects that were attributed to testosterone action until today. New data indicate role of estrogens and ER in the function of the cardio-vascular system. Their link with development of arteriosclerosis seems, however, to be bipolar. In single reported cases of men with the inactivating mutations of ERalpha or aromatase genes, a precocious arteriosclerosis is noted. From the other site, men homozygous for the most common variant of ERalpha gene (ESR1c.454-397cc) have a significantly increased risk of myocardial infraction. Estrogens are the risk factors in prostatic cancer and their local tissue increase in autoimmune diseases is connected with aggravation of the proliferative complications of these disorders.

Sex steroids and heart rate variability in patients after myocardial infarction.

BACKGROUND: Although the relationship between sex steroid levels and coronary artery disease (CAD) has been the subject of many studies there are still controversies concerning the role of sex steroids in CAD. In patients with CAD, especially after a myocardial infarction, there is evidence for autonomic nervous system dysfunction. However, there is no data detailing the relationship between sex steroids and cicardian autonomic activity in patients with CAD. The aim of the study was to evaluate the association between sex steroids and heart rate variability (HRV) parameters in postinfarction patients. METHODS: In 88 postinfarction men (aged 36-73, average 53 years), 24-hour Holter monitoring was performed to assess HRV parameters: SDNN, SDNNI, SDANN, rMSSD, pNN50, and levels of the following hormones were measured: testosterone, estradiol, free testosterone index, and estradiol/testosterone ratio. Univariate and multivariate regression analyses were used to investigate the relationship between HRV parameters and levels of tested hormones. RESULTS: Increased testosterone levels were associated with increased SDNN (r = 0.38, P = 0.03), increased rMSSD (r = 0.51, P = 0.002), and increased pNN50 (r = 0.45, P = 0.007). These associations remained significance after adjustment for age, ejection fraction, and other relevant clinical covariates. There was no significant association between estradiol and HRV parameters. CONCLUSION: In men with a history of myocardial infarction, higher levels of testosterone are associated with higher HRV measures of parasympathetic activity. These findings suggest that testosterone beneficially influences autonomic regulation of the heart.

[Sex steroids and heart rate variability in men with coronary artery disease after myocardial infarction]. / Steroidy plciowe a zmiennosc rytmu serca u mezczyzn z choroba wiencowa po zawale serca.

The role of sex steroids in coronary artery disease (CAD) has been studied for years. In patients after myocardial infarction autonomic nervous system dysfunction has been described. Heart rate variability (HRV) analysis is one of the method of autonomic nervous system evaluation. The aim of the study was to evaluate correlations between sex steroids and HRV in 88 men (aged 36-73, av. 53 yrs), with the history of MI, with angiographically documented CAD. In all the patients 24-hour Holter monitoring was performed to assess HRV time domain parameters: SDNN, SDNNI, SDANN, rMSSD, pNN50. Levels of testosterone and estradiol were measured in two subsequent blood samples, taken with 30 min interval. Free testosterone index as well as estradiol/testosterone ratio were assessed. For statistics r-Spearman test was used. Positive correlations were found between testosterone and SDNN (r = 0.38, p = 0.03), testosterone and rMSSD (r = 0.51, p = 0.002) and between testosterone and pNN50 (r = 0.45, p = 0.007). Since rMSSD and pNN50 are parameters describing parasympathetic activity, our results suggest that in CAD men with the history of myocardial infarction, testosterone may influences the function of autonomic nervous system promoting parasympathetic dominance. It can be favorable for the circulatory system function.