The effect of ultraviolet radiation on water-logging resistance in Tibetan peach

The effect of ultraviolet (UV) radiation on the water-logging resistance of Tibetan peach (Amygdalus mira Koehne) remains unclear. In this study, Tibetan peach seedlings were subjected to 9-days of UV-B (280 - 320 nm) supplementation, water-logging or the combination of both, and the growth indicated by leaf number, net photosynthetic rate and stomatal conductance were monitored. In addition, the activities of protection enzymes SOD and POD, as well as the concentrations of hormones ABA, ZR, GAs and ZR in leaves were examined. The results show that UV-B or water-logging or the combination of both factors restrained the growth trend, net photosynthetic rate and stomatal conductance. Both UV-B and water-logging increased SOD activity, and synergistically led to a drastic increase in POD activity. Furthermore, UV-B and water-logging condition increased the concentrations of ABA, ZR and GAs, while it decreased ZR. The results suggest that the changes of hormone concentrations in Tibetan peach leaves may explain the increased activities of protection enzymes and decreased photosynthesisunder water-logging condition

Reasons for the Premature Decline in \u3ci\u3eAstragalus adsurgens\u3c/i\u3e Stands in Kerqin Sandy Land

Diseases partly account for reductions in Astragalus adsurgens, stand longevity. The effect of some cultural practices on the control of pests and diseases have been reported (Hou, 1986; Nan, 1996), but few reports have detailed the relationship among soil fertiliser status, diseases and premature stand decline. This study was conducted to investigate these relationships in order to extend the longevity of Astragalus adsurgens stands

Facile Synthesis of High Quality Graphene Nanoribbons

Graphene nanoribbons have attracted attention for their novel electronic and spin transport properties1-6, and because nanoribbons less than 10 nm wide have a band gap that can be used to make field effect transistors. However, producing nanoribbons of very high quality, or in high volumes, remains a challenge. Here, we show that pristine few-layer nanoribbons can be produced by unzipping mildly gas-phase oxidized multiwalled carbon nanotube using mechanical sonication in an organic solvent. The nanoribbons exhibit very high quality, with smooth edges (as seen by high-resolution transmission electron microscopy), low ratios of disorder to graphitic Raman bands, and the highest electrical conductance and mobility reported to date (up to 5e2/h and 1500 cm2/Vs for ribbons 10-20 nm in width). Further, at low temperature, the nanoribbons exhibit phase coherent transport and Fabry-Perot interference, suggesting minimal defects and edge roughness. The yield of nanoribbons was ~2% of the starting raw nanotube soot material, which was significantly higher than previous methods capable of producing high quality narrow nanoribbons1. The relatively high yield synthesis of pristine graphene nanoribbons will make these materials easily accessible for a wide range of fundamental and practical applications.Comment: Nature Nanotechnology in pres

Effect of a Rho Kinase Inhibitor on Cognitive Impairment Induced by Chronic Cerebral Hypoperfusion in Rats

We examined the efficacy of a Rho kinase inhibitor, Fasudil, on cognitive impairment induced by chronic cerebral hypoperfusion in rats. Thirty-two male adult Sprague-Dawley rats were randomly divided into three groups; treated (T), control (C), and sham-operated (Sh); severe stenosis of the carotid arteries was modeled in the former two groups. During two weeks, 8.35 mg/kg Fasudil and physiological saline were i.p. applied twice per day in the T and C groups, respectively. The Morris water maze test was performed in each group to detect changes in the cognitive function and to observe pathological shifts in hippocampal morphology in rats after eight weeks. The mean escape latency was distinctly shorter (P < 0.01), and the percentage of swimming distance within the platform quadrant was significantly greater (P < 0.01) in the T group, compared to those in the C group at the corresponding time points. The rate of carotid artery stenosis in rats demonstrated no statistical difference between the T and C groups (P > 0.05). Fasudil injections effectively normalized hippocampal pathomorphology in the T group. Thus, the Rho kinase inhibitor obviously ameliorated cognitive impairment induced by chronic cerebral hypoperfusion in rats.Ми досліджували вплив інгібітора Rho-кінази фасудилу на когнітивні ураження, індуковані у щурів хронічною недостатністю перфузії мозку. 32 дорослі самці щурів СпрейгДоулі були рандомізовано поділені на три групи – “ліковану” (Т), контрольну (С) та псевдооперовану (Sh); у двох перших групах був модельований важкий стеноз сонних артерій. Протягом двох тижнів щурам груп Т і С внутрішньоочеревинно уводили двічі на день відповідно фасудил у дозі 8.35 мг/кг та фізіологічний розчин. Тварини всіх груп піддавали тесту Морріса у водному лабіринті, щоб виявити зміни когнітивної функції; у цих щурів спостерігали також патологічні зрушення морфології гіпокампа через вісім тижнів. У групі Т середній латентний період початку рухів уникання ставав істотно коротшим (P < 0.01), а нормована відстань переміщень у квадранті з платформою була вірогідно більшою (P < 0.01), ніж аналогічні показники у відповідних часових інтервалах у групі С. Ступінь стенозу сонних артерій у щурів груп Т та С не демонстрував істотних відмінностей. Ін’єкції фасудилу призводили до істотної нормалізації патоморфологічних зрушень у гіпокампі тварин групи Т. Отже, інгібітор Rho-кінази забезпечував явне зменшення уражень когнітивної сфери, індукованих у щурів хронічною гіпоперфузією мозку

Effects of Transduction of the bcl-2 Gene and of Nerve Growth Factor on Apoptosis of Cultured PC12 Cells

We examined what effects are exerted by expression of the bcl-2 gene and by treatment with nerve growth factor (NGF) on the intensity of apoptosis in cultured pheochromocytoma cells (PC12 cells). Half of these cells were transduced with the bcl-2 gene using lentiviral plasmids, and the respective two groups were denoted as bcl-2-PC12 and control (c) PC12. Then the cells were incubated in a serum-free medium in six different modes. One group of c-PC12 cells was incubated in this medium with no additional agents added, another group was incubated with 1.0 mM H₂O₂ , and the third group was incubated with both 1 mM H₂O₂ and 20 ng/ml NGF (groups 1-3). Cells of the another triad were incubated under the same conditions, respectively, but these were bcl-2-PC12 cells (groups 4-6). The apoptosis rate in each group after 1-h-long incubation was measured using a flow cytometry method. A bicinchoninic acid (BCA) technique was used for estimation of expression of Bcl-2 protein in the cultures. As was observed, the action of H₂O₂ significantly increased the apoptosis rate in both c-PC12 and bcl-2-PC12 samplings, while simultaneous action of NGF considerably attenuated such increases. At the same time, values of the apoptosis rate for bcl-2-PC12 cells were much smaller than the respective values for c-PC12 cells under all the three modes of incubation. In H₂O₂ -treated cultures, the amount of Bcl-2 protein dropped, while the treatment with NGF counteracted such shifts. The content of this protein in the bcl-2-PC12 groups was much higher than in the c-PC12 groups. Thus, transduction with the bcl-2 gene significantly inhibits apoptosis in cultured PC12 cells, and a combined influence of expression of this gene and treatment with NGF produces a synergistic effect.Ми досліджували впливи експресії гена bcl-2 та дії нервового фактора росту (NGF) на інтенсивність апоптозу культивованих клітин феохромоцитоми (PC12). У половину таких клітин був трансдукований ген bcl-2; відповідні дві групи зразків були позначені як bcl-2-PC12 та контрольні (с-PC12). Потім шість груп клітин інкубували в безсироватковому середовищі в різних умовах. Перша група клітин с-PC12 інкубувалася без дії будь-яких додаткових агентів, друга група – з додаванням 1 мМ H₂O₂ , а третя – в присутності як 1 мМ H₂O₂ , так і 20 нг/мл NGF. Клітини трьох інших груп (4–6) інкубували в тих самих умовах, але це були клітини bcl-2-PC12. Ступінь апоптозу в кожній групі після одногодинної інкубації вимірювали з використанням методу флоуцитометрії. Методику з використанням біцинхонінової кислоти застосовували для оцінки експресії білка Bcl-2 в культурах. Як було виявлено, дія H₂O₂ істотно збільшувала ступінь апоптозу в зразках як c-PC12, так і bcl-2-PC12, але одночасна дія NGF помітно зменшувала таке зростання. В той же час інтенсивності апоптозу клітин bcl-2-PC12 були значно меншими, ніж відповідні значення у клітин c-PC12 при всіх трьох режимах інкубації. В культурах, підданих впливу H₂O₂ , кількість протеїну Bcl-2 була зменшеною, тоді як вплив NGF протидіяв таким зрушенням. Вміст згаданого протеїну в групах bcl-2-PC12 був значно вищим, ніж у групах c-PC12. Отже, трансдукція гена bcl2 істотно гальмує апоптоз культивованих клітин PC12, а комбінований вплив експресії цього гена та аплікації NGF забезпечує сінергічні ефекти

On type Ia supernovae and the formation of single low-mass white dwarfs

There is still considerable debate over the progenitors of type Ia supernovae (SNe Ia). Likewise, it is not agreed how single white dwarfs with masses less than ~0.5 Msun can be formed in the field, even though they are known to exist. We consider whether single low-mass white dwarfs (LMWDs) could have been formed in binary systems where their companions have exploded as a SN Ia. In this model, the observed single LMWDs are the remnants of giant-branch donor stars whose envelopes have been stripped off by the supernova explosion. We investigate the likely remnants of SNe Ia, including the effects of the explosion on the envelope of the donor star. We also use evolutionary arguments to examine alternative formation channels for single LMWDs. In addition, we calculate the expected kinematics of the potential remnants of SNe Ia. SN Ia in systems with giant-branch donor stars can naturally explain the production of single LMWDs. It seems difficult for any other formation mechanism to account for the observations, especially for those single LMWDs with masses less than ~0.4 Msun. Independent of those results, we find that the kinematics of one potentially useful population containing single LMWDs is consistent with our model. Studying remnant white-dwarf kinematics seems to be a promising way to investigate SN Ia progenitors. The existence of single LMWDs appears to constitute evidence for the production of SNe Ia in binary systems with a red-giant donor star. Other single white dwarfs with higher space velocities support a second, probably dominant, population of SN Ia progenitors which contained main-sequence or subgiant donor stars at the time of explosion. The runaway stars LP400-22 and US 708 suggest the possibility of a third formation channnel for some SNe Ia in systems where the donor stars are hot subdwarfs.Comment: Accepted for publication in Astronomy & Astrophysic

The shear mode of multilayer graphene

The quest for materials capable of realizing the next generation of electronic and photonic devices continues to fuel research on the electronic, optical and vibrational properties of graphene. Few-layer graphene (FLG) flakes with less than ten layers each show a distinctive band structure. Thus, there is an increasing interest in the physics and applications of FLGs. Raman spectroscopy is one of the most useful and versatile tools to probe graphene samples. Here, we uncover the interlayer shear mode of FLGs, ranging from bilayer graphene (BLG) to bulk graphite, and suggest that the corresponding Raman peak measures the interlayer coupling. This peak scales from ~43 cm−1 in bulk graphite to ~31 cm−1 in BLG. Its low energy makes it sensitive to near-Dirac point quasiparticles. Similar shear modes are expected in all layered materials, providing a direct probe of interlayer interactions

Laser-induced etching of few-layer graphene synthesized by Rapid-Chemical Vapour Deposition on Cu thin films

The outstanding electrical and mechanical properties of graphene make it very attractive for several applications, Nanoelectronics above all. However a reproducible and non destructive way to produce high quality, large-scale area, single layer graphene sheets is still lacking. Chemical Vapour Deposition of graphene on Cu catalytic thin films represents a promising method to reach this goal, because of the low temperatures (T < 900 Celsius degrees) involved during the process and of the theoretically expected monolayer self-limiting growth. On the contrary such self-limiting growth is not commonly observed in experiments, thus making the development of techniques allowing for a better control of graphene growth highly desirable. Here we report about the local ablation effect, arising in Raman analysis, due to the heat transfer induced by the laser incident beam onto the graphene sample.Comment: v1:9 pages, 8 figures, submitted to SpringerPlus; v2: 11 pages, PDFLaTeX, 9 figures, revised peer-reviewed version resubmitted to SpringerPlus; 1 figure added, figure 1 and 4 replaced,typos corrected, "Results and discussion" section significantly extended to better explain etching mechanism and features of Raman spectra, references adde

The Evolution of Cool Algols

We apply a model of dynamo-driven mass loss, magnetic braking and tidal friction to the evolution of stars with cool convective envelopes; in particular we apply it to binary stars where the combination of magnetic braking and tidal friction can cause angular-momentum loss from the {\it orbit}. For the present we consider the simplification that only one component of a binary is subject to these non-conservative effects, but we emphasise the need in some circumstances to permit such effects in {\it both} components. The model is applied to examples of (i) the Sun, (ii) BY Dra binaries, (iii) Am binaries, (iv) RS CVn binaries, (v) Algols, (vi) post-Algols. A number of problems regarding some of these systems appear to find a natural explanation in our model. There are indications from other systems that some coefficients in our model may vary by a factor of 2 or so from system to system; this may be a result of the chaotic nature of dynamo activity