Comet Research Articles

Speaking of Comets

Speaking of Comets

Formation mechanism of amorphous silicon nanoparticles with additional counter-flow quenching gas by induction thermal plasma

The fabrication process of amorphous silicon nanoparticles by induction thermal plasma was studied by experiments and numerical simulations. Additional quenching gas was introduced as counter-flow to the plasma tail flame to enhance quenching effect. The flow rate of quenching gas ranged from 0 to 70 L/min. Amorphous silicon nanoparticles were confirmed by electronic diffraction analysis with random shapes and serious agglomerate, while the crystal particles had a totally different morphology of spherical and freestanding. The quenching rate was estimated on the basis of numerical results and increased from 3.2 × 104 to 8.9 × 105 K/s with quenching gas flow rate. The amount of amorphous silicon increased as quenching gas injection and should be attributed to the improved preparation of small nanoparticles (<5 nm). The above results suggested the formation of amorphous silicon in thermal plasma is controllable.

Mutações de resistência a antirretrovirais e diversidade genética do HIV-1 em gestantes atendidas em uma maternidade de referência no Estado do Piauí, Brasil

Objetivo: identificar os subtipos do HIV-1, avaliar a presença de mutações de resistência aos antirretrovirais (DRM) e estimar o nível de resistência das cepas mutantes detectadas em mulheres gestantes atendidas na maternidade de referência no Piauí, nordeste do Brasil. Metodologia: Das 873 mulheres gestantes, 17 infectadas pelo HIV-1 foram selecionadas para participar deste estudo. A genotipagem do HIV-1 foi realizada usando sequenciamento de nucleotídeos seguida de análises filogenéticas para determinar o subtipo viral, incluindo a identificação usando ferramenta on-line COMET. DRM foram definidas usando o programa Calibrated Population Resistance Tool. Análises adicionais também foram realizadas para verificar a resistência aos medicamentos no pré-tratamento usando o Programa Stanford HIVdb. Resultados: O subtipo B foi detectado em todas as gestantes infectadas pelo HIV-1. A prevalência de DRM foi 11.8%. As mutações L90M e K103N foram identificadas, sendo estimada resistência alta (nelfinavir e nevirapine) e intermediária (indinavir e saquinavir) a diferentes antirretrovirais. Conclusão: Este estudo identificou importantes informações genéticas do HIV-1 em gestantes no Piauí, as quais podem auxiliar no direcionamento de medidas de controle e de prevenção dessa infecção viral.

Evaluation of Micronucleus Assay and Genotoxic Effect in Oreochromis mossambicus Exposed to a Fumaronitrile

Chemical contaminants of major concern in a polluted environment include persistent organic chemical, pesticides, oils, nutrients, heavy metals, etc. Some of these chemicals are known genotoxicants and can cause damage to the genetic material of the exposed organism. Apart from the enzymatic biomarkers, other parameters, such as DNA damage, should be evaluated for assessing the consequences of exposure of chemical. Damaged DNA may potentiate subsequent deleterious cellular events such as disease (e.g. cancer) and reduced reproductive competence. DNA damage in a variety of aquatic animals has been associated with reduced growth, abnormal development and reduced survival of embryos, larvae and adults. The DNA damage which is induced by fumaronitrile exposure could be evaluated by using the comet assay. The comet assay [alkaline single-cell gel electrophoresis] is a widely used technique to detect DNA damage due to environmental stress. The toxicological effect of fumaronitrile originates from its oxidizing action. Once entered in to the cell, in the presence of cellular reluctant, it induces DNA fragmentation, which is considered to be premutagenic change. The kind of the nuclear alterations observed in erythrocytes of Oreochromis mossambicus exposed to the fumaronitrile is binucleated cells, cells with bleb bed and lobed nuclei.

Using Stereoscopic Observations of Cometary Plasma Tails to Infer Solar Wind Speed

Abstract Detection of the solar wind speed near the Sun is significant in understanding the heating and acceleration of the solar wind. Cometary plasma tails have long been used as natural probes for solar wind speed; previous solar wind speed estimates via plasma tails, however, were based on comet images from a single viewpoint, and the projection effect may influence the result. Using stereoscopic observations from the Solar Terrestrial Relations Observatory and the Solar and Heliospheric Observatory, we three-dimensionally reconstruct the plasma tails of three comets C/2012 S1 (ISON), C/2010 E6, and C/2011 W3 (Lovejoy) and infer the ambient solar wind speed. The first comet is located between 3.5 and 6 solar radii (Rs) away from the Sun at high latitudes; the estimated solar wind speed is about 300–500 km s−1. The second comet is located within 10 Rs and about 20° away from the ecliptic; the estimated solar wind speed is about 200–320 km s−1. The third comet is also located at low latitudes but farther (&gt;20 Rs) away from the Sun; the estimated solar wind speed is about 100–600 km s−1. For comets near the ecliptic, our results are close to those predicted by MHD models, whereas for the comet at high latitudes, the deviation between our estimate and the model results is notable. This consistency and difference could be used to constrain and improve solar wind models. We will seek opportunities to apply the method to comet 322P, whose tail may sweep the Parker Solar Probe.

Transition from snowplow to deflagration mode in a gas-prefilled parallel-plate plasma accelerator

The transition from snowplow mode to deflagration mode of a parallel-plate plasma accelerator under gas-prefilled conditions is studied. The accelerator is powered by a sinusoidal-wave power supply with a first half-period current of 24.3 μs. The current distribution of the current conduction channel is measured by magnetic probes, the optical emission spectrum by a spectroscopic system, and the plasma optical intensity by photodiodes. The parallel-plate plasma accelerator does not form a thin current sheet, but a wide and diffuse current conduction region when the capacitors are charged to 8 kV and 13 kV. The discharge mode is a transition from snowplow mode to deflagration mode, from the current leading edge to the trailing edge. The plasma front region continuously sweeps and ionizes the neutral gas within a certain thickness, which is characteristic of snowplow mode, whereas the plasma tail region is a stationary current conducting channel maintained by ablating the copper electrodes, which is characteristic of deflagration mode. The transition mechanism from snowplow mode to deflagration mode might be breakdown caused by rail electrode overvoltage.

La legitimación de los saberes científicos en el siglo XVII novohispano. Sobre la controversia astronómica entre Carlos de Sigüenza y Góngora y Eusebio Kino

La controversia astronómica entre Carlos de Sigüenza y Góngora y Eusebio Francisco Kino sobre el cometa observado desde el hemisferio norte en 1680 y 1681 fue leída por la crítica a través de categorías dicotómicas, silenciando el complejo mapa de actores involucrados en la producción, publicación y circulación de sus tratados científicos. En este artículo proponemos realizar un análisis que integre los campos de los estudios literarios latinoamericanos y de los Estudios de Ciencia, Tecnología y Sociedad con el objetivo de comparar las redes de mecenazgo e institucionales y las estrategias retóricas que a través del tiempo otorgaron legitimidad a las obras de los contendientes.

KEKERASAN VERBAL DALAM VIDEO MONOLOG AKUN INSTAGRAM @ismaillishtkroo

This research was conducted to describe (1) the types of speech acts, (2) the speech act functions; (3) the types of verbal violence in the monologue video account @ismaillishtkroo. This type of research is a qualitative study using descriptive method. The object of this study is a speech containing verbal violence in monologue and comet video on the Instagram account @ismaillishtkroo. The data taken was analyzed with the following steps: (1) transcribing spoken language in the video into written language, (2) identifying data in accordance with the aspects studied, (3) classifying research data by creating tables based on aspects that are researched, (4) interpreting data, (5) inferring data based on research results. In this study, found the following 3 things. First, the types of speech acts that found are expressive, directive, assertive and commissive. Second, the speech act function found is a contradictory and competitive function. Third, the types of verbal violence found are curse, ridicule, accusations, intimidation, insults, coercion, threats, harassment, curses, and rebuke.

Some Features of Comet Hale–Bopp (According to the Observations of 1995–1998)

Some Features of Comet Hale–Bopp (According to the Observations of 1995–1998)

Progress in occupational injury and protection of nurses against anti-cancer drug

This paper summarized the injury mechanism and protection status of anticancer drug exposure to nurses in recent years from the aspects of reproductive toxicity, genetic damage, environmental monitoring, and occupational protection compliance of nurses, aiming to provide guidance for anticancer drug protection and guarantee for nurses' occupational safety. Key words: Anti-cancer drugs; Reproductive toxicity; Cytotoxicity; Comet test; Protective equipment

The in vivo genotoxicity of isotretinoin assessed by comet assay.

The in vivo genotoxicity of isotretinoin assessed by comet assay.

Allusive Prodigia: Caesar's Comets in Neronian Rome (Tac. Ann. 15.47)

Allusive Prodigia: Caesar's Comets in Neronian Rome (Tac. Ann. 15.47)

Preventive Effect of Opuntiol, Isolated from Opuntia ficus indica (L. Mill), Extract Against Ultraviolet A Radiation-Induced Oxidative Damages in NIH/3T3 Cells

Aim: We investigated the role of opuntiol, isolated from Opuntia ficus indica, against ultraviolet A waveband-mediated oxidative damages in the mouse embryonic fibroblast cell lines (NIH‐3T3). Materials and Methods: The antioxidant potential of opuntiol was carried out by hydroxyl radical, superoxide anion and DPPH radical scavenging assays. The preventive effect of opuntiol against UV-mediated cytotoxicity was revealed by MTT assay. Further, the oxidative end points during UV-exposure, in the presence and absence of opuntiol, was analyzed by DCFH-DA staining, rhodamine-123 staining and alkaline comet assay. Results: Opuntiol significantly neutralizes hydroxyl (OH•), superoxide anion (O2•–), hydrogen peroxide (H2O2), and 2,2-diphenyl-2-picrylhydrazyl (DPPH•) radicals in a concentration-dependent manner. In this study, the NIH-3T3 cells were treated with UVA-waveband in the presence and absence of opuntiol and oxidative damage markers were analyzed. We observed that opuntiol pretreatment (5 μM-20 μM) prevented 10 mJ/cm2UVA radiation-induced cytotoxicity in NIH-3T3 cells. Further, single UVA-radiation induces reactive oxygen species (ROS) through intracellular photosensitizers. Conversely, opuntiol pretreatment prevented UVA-mediated ROS generation and subsequent lipid peroxidation and loss of enzymatic antioxidants (superoxide dismutase [SOD], catalase, and glutathione peroxidase) in the NIH-3T3 cells. It has also been observed that the UVA-mediated ROS subsequently induces DNA damage and alters mitochondrial transmembrane potential (MMP). We noticed that opuntiol prevents UVA-radiation-mediated DNA single-strand breaks. Further, it prevents loss of MMPs and apoptotic morphological changes in the NIH-3T3 cells. Conclusion: Thus, these findings illustrate that opuntiol prevents UVA-radiation-mediated oxidative stress-related biochemical changes in the cellular system.

DNA damage in human skin fibroblasts from patients with dermatitis herpetiformis.

Dermatitis herpetiformis (DH) and celiac disease (CD) are considered to be autoimmune diseases that share a specific trigger (gluten) and a common genetic background (HLA-DQ2/DQ8). However, the pathogenesis of DH is not yet fully understood and no data are available regarding a possible role of fibroblasts in this disease. The aim of this study was to assess baseline DNA damage in fibroblasts in DH-diagnosed patients vs. fibroblasts of controls without DH or CD. Primary fibroblast cultures were derived from dermal biopsies from DH patients and controls (without DH or CD). In vitro genotoxic damage was investigated using the comet assay and ɣH2AX test after different treatments (with 33mer peptide and digested gliadin [DG]) in order to investigate a correlation between oxidative stress (evaluated by reactive oxygen species formation) and glutathione content. Our results demonstrate a difference in baseline DNA damage between cutaneous fibroblasts of controls and DH patients, moreover, DNA damage significantly increased after exposure to gluten (DG and 33mer peptide) in fibroblasts from DH patients. DNA damage in fibroblasts from patients under dapsone treatment was similar to that of the control group. Our data indicate that oxidative stress and DNA damage may be characteristics of fibroblasts from DH patients who are not treated with dapsone, particularly after exposure to gliadin peptides.

The Flow of Triboplasma

Previously triboplasma was discovered in the rear gap of the sliding contact. Recently, the temperature of the triboplasma was successfully measured and demonstrated that the triboplasma is the non-equilibrium low-temperature plasma. During the course of the temperature rise distribution measurement of the triboplasma, flow of the triboplasma was observed. In this article, the triboplasma flow behaviors were investigated by measuring the triboplasma temperature rise distribution using a highly sensitive microscopic infrared camera. The measurement was performed in the tribosystem while a diamond pin with a tip radius of 4 mm slides on a sapphire disk with the wear track diameter of 40 mm in dry sliding in the ambient air under the normal forces of FN = 1 N and 2 N and the disk rotational velocities of ω = 10, 20, 50, 100, and 155 rpm, which correspond to the sliding velocities of V = 0.021, 0.042, 0.105, 0.21, and 0.324 m/s, respectively. In the experiments, the pin and disk specimens were warmed to raise the negligibly small temperature rise of the rear plasma tail region to the infrared camera imaging detection level by transferring the specimen’s heat to the plasma. Two types of plasma flows have been observed. One of them is a lamellar flow under the rotational velocity region of ω ≦ 10 rpm (V ≦ 0.021 m/s). This laminar flow transits to the turbulent one under ω ≧ 20 rpm (V ≧ 0.042 m/s). At the lamellar flow region, the triboplasma flows in the direction of sliding. However, at the turbulent flow region, the plasma flow direction shifts clockwise from the sliding line to the direction of disk rotation. The flow angle between the sliding line and the plasma flow one increases with the rotational velocity due to the centrifugal forces by disk rotation.

Habitability impacts of molecular clouds

Astrobiology The Sun is currently located in a low-density region of interstellar space, but conditions would be very different if it were inside a giant molecular cloud (GMC). These vast assemblages of relatively dense gas and dust are concentrated within the Milky Way's spiral arms. Passing through a GMC would block visible light from other stars, owing to dust absorption, and reduce the habitability of Earth by scattering comets onto impact orbits. Kokaia and Davies calculated the expected encounter rate between the Sun and GMCs: 1.6 ± 1.3 per billion years, lasting a few million years each time. Fortunately for life on Earth, these disruptive encounters are rare. Mon. Not. R. Astron. Soc. , in press, arXiv:1903.08026 (2019).

Evidences of the charge fundamental asymmetry

Abstract There is an infinitesimal small non polarizable electric inertial charge in the individual atoms or in a number neutral matter included to equal number of the electrons and protons. We refer to the pure calculations verified by the experimental laboratorial results, also planetary phenomena and cosmic observations. This inertial electric charge is origin of a part of the measurable magnetic field in addition to self-consistent dynamo, together as complementary origins to generate very complex magnetism of the celestial bodies. Ultimately we refer to the null results of the test experiments for the spinning bodies magnetic field and we see that neither used bodies in the experiments have been number neutral (no equal number of the electrons and protons), nor the simple formula of the Patrick Blackett is accurate in detail. But we have extracted a new formula in agreement for all spinning bodies magnetic fields, in agreement with both terrestrial and cosmic bodies. We verify the effect of electric charge asymmetry in expanding universe and acceleration of the universe expansion and anisotropy of cosmic microwave background and singularity paradox and solar wind and acceleration of solar wind and corona high temperature puzzle as an equilibrium between the gravity and antigravity and mysterious heat generation of the Sun and planets interiors and missing neutrino and the comets plasma tail outward direction and pendulums mysterious precessions and some other mysteries phenomena too.

Ameliorative role of quercetin in iron overload induced heart and brain toxicity in adult male albino rats

Although iron is an essential element for life, its excess is linked to many disorders. The aim of this study is to investigate the effect of quercetin on iron induced toxicity on the heart and brain in adult male albino rats. 50 adult male albino rats were equally divided into groups; Group I (negative control), Group II (positive control) received normal saline 0.9%. Group III (Quercetin group) was treated with quercetin (2 g/kg daily) for 8 weeks and Group IV (Iron group) was injected intraperitoneal daily with iron dextran (300 mg/kg) for 4 weeks. Group V (Iron and quercetin group) was injected intraperitoneal daily with iron dextran (300 mg/kg) for 4 weeks, and then gavaged orally with quercetin (2 g/kg once a day) for another 4 weeks. At the end of the study, blood samples were taken to estimate the serum levels of iron, malondialdehyde (MDA), and total antioxidant capacity (TAC). Heart and brain specimens were dissected from scarified rats to estimate tissue level of iron, histopathological examination, immunohistochemical staining for tumor necrosis factor (TNFα) and comet assay. Iron overload caused increases in serum, heart and brain iron levels; increase in serum MDA and decrease in serum TAC with degenerative changes in the examined tissues and increasing expression of TNFα and DNA degradation. After administration of quercetin, a significant improvement in all these parameters was observed. Quercetin acts as iron chelator decreasing serum and tissue iron levels, ameliorating oxidative stress, inflammatory effects and DNA damage induced by iron overload. More studies are recommended to evaluate the beneficial effects of quercetin with iron excess. Key words: Iron, quercetin, heart toxicity, brain toxicity.

Stress in the neck of bilobate comets

Stress in the neck of bilobate comets

Effect of Olaparib on proliferation activity and radiosensitization of human non-small cell lung cancer cells

Objective To investigate the effects of Olaparib on cell proliferation and radiosensitization of human non-small cell lung cancer cells. Methods Non-small cell lung H460 and H1299 cell lines were cultured in vitro and the cells in logarithmic growth phase were selected for experiments. MTT and colony formation assays were used to determine cell proliferation and radiosensitization, respectively. Single cell gel electrophoresis assay (comet assay) was used to detect irradiation-induced DNA damage. Results The results of MTT assay showed that Olaparib inhibited the proliferation of H460 and H1299 cells in a dose-dependent pattern (all P<0.05). H1299 cell line was more sensitive to Olaparib than H460 cells. The results of colony formation assay showed that Olaparib enhanced the radiosensitizition of H460 and H1299 cells (all P<0.05). The results of comet assay showed that Olaparib increased γ ray-induced DNA damage. Conclusions Olapani can enhance the radiosensitization of human non-small cell lung cancer cells, and the radiosensitization effect of Olaparib may be associated with the inhibition of cell proliferation and induction of irradiation-induced DNA damage. Key words: Olaparib; Non-small cell lung cancer cells; Radiosensitization; Proliferation; DNA damage