Graphene Prepared via the Dry Ice in Flames Method and its Purification Using Different Routes: A Comparative Study

Although the dry ice method used to synthesize exfoliated graphite/graphene is little known and used, it has significant advantages over others: it is low cost, simple, and a large quantity of material can be obtained using some inorganic and highly available acids (which can be reused). Despite the above advantages, the main reason for its incipient development is the resulting presence of magnesium oxide in the final product. In the present work, three different treat-ments were tested to remove this remnant using some acid chemical leaching processes, making use of hydrochloric acid, aqua regia, and piranha solution. Based on the experimental evidence, it was found that using aqua regia and combining the leaching process with mechanical milling was the most efficient way of removing such a remnant, the residue being only 0.9 wt.%. This value is low when compared to that obtained with the other acid leaching solutions and purifi-cation process (2.8 - 29.6 wt.%). A mandatory high-energy mechanical milling stage was neces-sary during this treatment, in order to expose and dissolve the highly insoluble oxide without secondary chemical reactions on the graphenes. High-energy mechanical milling is an effective route to exfoliate graphite/graphene, which allows the magnesium oxide to be more susceptible to acid treatment. The obtained surface area was 504 m2g-1; this high value resulting from the in-tense exfoliation can potentiate the use of this material for a wide variety of applications.

Graphene Prepared via the Dry Ice in Flames Method and Its Purification Using Different Routes: A Comparative Study

Although the dry ice method used to synthesize exfoliated graphite/graphene is little known and used, it has significant advantages over others: it is low cost, simple, and a large quantity of material can be obtained using some inorganic and highly available acids (which can be reused). Despite the above advantages, the main reason for its incipient development is the resulting presence of magnesium oxide in the final product. In the present work, three different treatments were tested to remove this remnant using some acid chemical leaching processes. Based on the experimental evidence, it was found that using aqua regia, among other chemical mixtures, was the most efficient way of removing such as remnant, the residue being only 0.9 wt.%. A mandatory high-energy mechanical milling stage was necessary during this treatment, in order to expose and dissolve the highly insoluble oxide without secondary chemical reactions on the graphenes. The obtained surface area was 504 m2g-1; this high value resulted from the intense exfoliation can potentiate the use of this material for a wide variety of applications.

Penggunaan Pestisida Nabati Ekstrak Daun Pepaya (Carica Papaya L.) pada Tanaman Kacang Panjang (Vigna Sinensis L.) untuk Mengurangi Dampak Pencemaran Lingkungan di Desa Gunung Selamat, Kec. Bilah Hulu, Kab. Labuhanbatu

Vegetable pesticides are pesticides whose active ingredients come from plants and other organic materials that control pest attacks on plants, containing many bioactive compounds such as phenolic, alkaloid compounds and also other secondary chemical substances. Papayas are plants originating from Central America. Papaya can grow well in areas that are in tropical climates. Some of the ingredients contained in papaya leaves include papain enzymes, flavonoids, alkaloids, saponins, and tannis. All of the content contained in papaya leaves, the papain enzyme is the most abundant chemical content in papaya leaves because it comes from papaya sap.

The impact of inhomogeneous emissions and topography on ozone photochemistry in the vicinity of Hong Kong Island

Global and regional chemical transport models of the atmosphere are based on the assumption that chemical species are completely mixed within each model grid box. However, in reality, these species are often segregated due to localized sources and the influence of topography. In order to investigate the degree to which the rates of chemical reactions between two reactive species are reduced due to the possible segregation of species within the convective boundary layer, we perform large-eddy simulations (LESs) in the mountainous region of Hong Kong Island. We adopt a simple chemical scheme with 15 primary and secondary chemical species, including ozone and its precursors. We calculate the segregation intensity due to inhomogeneity in the surface emissions of primary pollutants and due to turbulent motions related to topography. We show that the inhomogeneity in the emissions increases the segregation intensity by a factor of 2–5 relative to a case in which the emissions are assumed to be uniformly distributed. Topography has an important effect on the segregation locally, but this influence is relatively limited when considering the spatial domain as a whole. In the particular setting of our model, segregation reduces the ozone formation by 8 %–12 % compared to the case with complete mixing, implying that the coarse-resolution models may overestimate the surface ozone when ignoring the segregation effect.

Preference, performance, and chemical defense in an endangered butterfly using novel and ancestral host plants

Adoption of novel host plants by herbivorous insects can require new adaptations and may entail loss of adaptation to ancestral hosts. We examined relationships between an endangered subspecies of the butterfly Euphydryas editha (Taylor’s checkerspot) and three host plant species. Two of the hosts (Castilleja hispida, Castilleja levisecta) were used ancestrally while the other, Plantago lanceolata, is exotic and was adopted more recently. We measured oviposition preference, neonate preference, larval growth, and secondary chemical uptake on all three hosts. Adult females readily laid eggs on all hosts but favored Plantago and tended to avoid C. levisecta. Oviposition preference changed over time. Neonates had no preference among host species, but consistently chose bracts over leaves within both Castilleja species. Larvae developed successfully on all species and grew to similar size on all of them unless they ate only Castilleja leaves (rather than bracts) which limited their growth. Diet strongly influenced secondary chemical uptake by larvae. Larvae that ate Plantago or C. hispida leaves contained the highest concentrations of iridoid glycosides, and iridoid glycoside composition varied with host species and tissue type. Despite having largely switched to a novel exotic host and generally performing better on it, this population has retained breadth in preference and ability to use other hosts.

Why probiotics yogurt is beneficial to HIV/AIDS patients?

AIDS patients often display symptom of diarrhea, an indication of hydrogen bonding mediated by viral proteins with amino acids capable of secondary chemical bonding. With hydrogen bonding to protons, local strong acids such as HCl could build up, giving rise to proton stress which may damage cells or trigger tumorigenesis. Weak organic acids counteract strong acids and attenuate proton stress. The integration of antiviral medicine with probiotics could yield favorable outcomes to AIDS patients and meanwhile reduce cancer incidences.