Effect of Preliminary Torsional Strain on Low-Cycle Fatigue of Q345B Structural Steel

Effect of preliminary torsional strain on low-cycle fatigue of Q345B steel was studied. The specimens were first 0, 180, and 360° twisted, then the low-cycle fatigue of Q345B steel was evaluated in the strain range of 0.3–0.8% by the method of axisymmetrical strain. The cycling response, cyclic stress–strain relationship, strain–life relationship, fatigue life prediction model, and seismic stability at different torsion angles were obtained and analyzed. The strain–life curve is shown to slope down as a power function. The fatigue life comes down with preliminary torsional strain at a constant level. The cycling response varied from cyclic hardening to cyclic softening in preliminary torsion, and the cyclic hardening rate increased linearly with the strain amplitude. The parameters of the Coffin–Manson relation are corroborated with experimental data. After heat treatment, the seismic stability of the material is improved, with torsional strain greatly reducing this characteristic. Electron microscope examination of fatigue fracture revealed a fatigue crack initiating on the surface of the specimen. The propagating crack deviated from its direction, and plasticity of the material dropped as a result of preliminary torsional strain.Изучено влияние деформации предварительного кручения на малоцикловую усталость стали Q345B. Вначале образцы скручивали на 0, 180 и 360°, затем методом осесимметричной деформации определяли малоцикловую усталость стали Q345B в диапазоне деформаций 0.3 0.8%. Получены и проанализированы характеристика циклических изменений, зависимость циклического изменения напряжения от деформации, зависимость деформация долговечность, модель прогнозирования усталостной долговечности и сейсмостойкость при различных углах кручения. Показано, что кривая деформация долговечность идет вниз и описывается степенной функцией. Усталостная долговечность снижается с увеличением деформации предварительного кручения при постоянном уровне последней. Характеристика циклических изменений варьировала от циклического упрочнения до циклического разупрочнения при кручении, скорость циклического упрочнения возрастала линейно с повышением амплитуды деформации. Параметры зависимости Коффина Мэнсона подтверждаются экспериментальными данными. После термообработки сейсмостойкость материала улучшается, при этом деформация предварительного кручения существенно снижает ее. Электронно-микроскопическое исследование усталостного разрушения выявило зарождение усталостной трещины на поверхности образца. Растущая трещина отклонялась от своего направления, пластичность материала снижалась в результате деформации предварительного кручения.Вивчено вплив деформації попереднього кручення на малоціклову втому стали Q345B. Спочатку зразки скручували на 0, 180 і 360 °, потім методом вісесиметричної деформації визначали малоціклову втому стали Q345B в діапазоні деформацій 0.3-0.8%. Отримано і проаналізовано характеристику циклічних змін, залежність циклічної зміни напржень від деформації, залежність деформація-довговічність, модель прогнозування втомної довговічності і сейсмостійкості при різних кутах кручення. Показано, що крива деформація - довговічність йде вниз і описується ступеневою функцією. Втомна довговічність знижується зі збільшенням деформації попереднього кручення при постійному рівні останньої. Характеристика циклічних змін варіювала від циклічного зміцнення до циклічного знеміцнення при крученні, швидкість циклічного зміцнення зростала лінійно з підвищенням амплітуди деформації. Параметри залежності Коффина-Менсона підтверджуються експериментальними даними. Після термообробки сейсмостійкість матеріалу поліпшується, при цьому деформація попереднього кручення істотно знижує її. Електронно-мікроскопічне дослідження втомного руйнування виявило зародження втомної тріщини на поверхні зразка. Зростаюча тріщина відхилялася від свого напрямку, пластичність матеріалу знижувалася в результаті деформації попереднього кручення

Cryptic photosynthesis, Extrasolar planetary oxygen without a surface biological signature

On the Earth, photosynthetic organisms are responsible for the production of virtually all of the oxygen in the atmosphere. On the land, vegetation reflects in the visible, leading to a red edge that developed about 450 Myr ago and has been proposed as a biosignature for life on extrasolar planets. However, in many regions of the Earth, and particularly where surface conditions are extreme, for example in hot and cold deserts, photosynthetic organisms can be driven into and under substrates where light is still sufficient for photosynthesis. These communities exhibit no detectable surface spectral signature to indicate life. The same is true of the assemblages of photosynthetic organisms at more than a few metres depth in water bodies. These communities are widespread and dominate local photosynthetic productivity. We review known cryptic photosynthetic communities and their productivity. We link geomicrobiology with observational astronomy by calculating the disk-averaged spectra of cryptic habitats and identifying detectable features on an exoplanet dominated by such a biota. The hypothetical cryptic photosynthesis worlds discussed here are Earth-analogs that show detectable atmospheric biomarkers like our own planet, but do not exhibit a discernable biological surface feature in the disc-averaged spectrum.Comment: 23 pages, 2 figures, Astrobiology (TBP) - updated Table 1, typo in detectable O2 correcte

Therapeutic effect of hydrogen sulfide-releasing L-dopa derivative ACS84 on 6-OHDA-induced Parkinson's disease rat model

Parkinson's disease (PD), characterized by loss of dopaminergic neurons in the substantia nigra, is a neurodegenerative disorder of central nervous system. The present study was designed to investigate the therapeutic effect of ACS84, a hydrogen sulfide-releasing-L-Dopa derivative compound, in a 6-hydroxydopamine (6-OHDA)-induced PD model. ACS84 protected the SH-SY5Y cells against 6-OHDA-induced cell injury and oxidative stress. The protective effect resulted from stimulation of Nrf-2 nuclear translocation and promotion of anti-oxidant enzymes expression. In the 6-OHDA-induced PD rat model, intragastric administration of ACS84 relieved the movement dysfunction of the model animals. Immunofluorescence staining and High-performance liquid chromatography analysis showed that ACS84 alleviated the loss of tyrosine-hydroxylase positive neurons in the substantia nigra and the declined dopamine concentration in the injured striatums of the 6-OHDA-induced PD model. Moreover, ACS84 reversed the elevated malondialdehyde level and the decreased glutathione level in vivo. In conclusion, ACS84 may prevent neurodegeneration via the anti-oxidative mechanism and has potential therapeutic values for Parkinson's disease

Partial wave analysis of J/\psi \to \gamma \phi \phi

Using $5.8 \times 10^7 J/\psi$ events collected in the BESII detector, the radiative decay $J/\psi \to \gamma \phi \phi \to \gamma K^+ K^- K^0_S K^0_L$ is studied. The $\phi\phi$ invariant mass distribution exhibits a near-threshold enhancement that peaks around 2.24 GeV/$c^{2}$. A partial wave analysis shows that the structure is dominated by a $0^{-+}$ state ($\eta(2225)$) with a mass of $2.24^{+0.03}_{-0.02}{}^{+0.03}_{-0.02}$ GeV/$c^{2}$ and a width of $0.19 \pm 0.03^{+0.06}_{-0.04}$ GeV/$c^{2}$. The product branching fraction is: $Br(J/\psi \to \gamma \eta(2225))\cdot Br(\eta(2225)\to \phi\phi) = (4.4 \pm 0.4 \pm 0.8)\times 10^{-4}$.Comment: 11 pages, 4 figures. corrected proof for journa

Measurements of the observed cross sections for e+e−→e^+e^-\to exclusive light hadrons containing π0π0\pi^0\pi^0 at s=3.773\sqrt s= 3.773, 3.650 and 3.6648 GeV

By analyzing the data sets of 17.3, 6.5 and 1.0 pb$^{-1}$ taken, respectively, at $\sqrt s= 3.773$, 3.650 and 3.6648 GeV with the BES-II detector at the BEPC collider, we measure the observed cross sections for $e^+e^-\to \pi^+\pi^-\pi^0\pi^0$, $K^+K^-\pi^0\pi^0$, $2(\pi^+\pi^-\pi^0)$, $K^+K^-\pi^+\pi^-\pi^0\pi^0$ and $3(\pi^+\pi^-)\pi^0\pi^0$ at the three energy points. Based on these cross sections we set the upper limits on the observed cross sections and the branching fractions for $\psi(3770)$ decay into these final states at 90% C.L..Comment: 7 pages, 2 figure

Direct Measurements of Absolute Branching Fractions for D0 and D+ Inclusive Semimuonic Decays

By analyzing about 33 $\rm pb^{-1}$ data sample collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, we directly measure the branching fractions for the neutral and charged $D$ inclusive semimuonic decays to be $BF(D^0 \to \mu^+ X) =(6.8\pm 1.5\pm 0.7)$ and $BF(D^+ \to \mu^+ X) =(17.6 \pm 2.7 \pm 1.8)$, and determine the ratio of the two branching fractions to be $\frac{BF(D^+ \to \mu^+ X)}{BF(D^0 \to \mu^+ X)}=2.59\pm 0.70 \pm 0.25$

A study of charged kappa in J/ψ→K±Ksπ∓π0J/\psi \to K^{\pm} K_s \pi^{\mp} \pi^0

Based on $58 \times 10^6$ $J/\psi$ events collected by BESII, the decay $J/\psi \to K^{\pm} K_s \pi^{\mp} \pi^0$ is studied. In the invariant mass spectrum recoiling against the charged $K^*(892)^{\pm}$, the charged $\kappa$ particle is found as a low mass enhancement. If a Breit-Wigner function of constant width is used to parameterize the kappa, its pole locates at $(849 \pm 77 ^{+18}_{-14}) -i (256 \pm 40 ^{+46}_{-22})$ MeV/$c^2$. Also in this channel, the decay $J/\psi \to K^*(892)^+ K^*(892)^-$ is observed for the first time. Its branching ratio is $(1.00 \pm 0.19 ^{+0.11}_{-0.32}) \times 10^{-3}$.Comment: 14 pages, 4 figure

Partial Wave Analysis of J/ψ→γ(K+K−π+π−)J/\psi \to \gamma (K^+K^-\pi^+\pi^-)

BES data on $J/\psi \to \gamma (K^+K^-\pi^+\pi^-)$ are presented. The $K^*\bar K^*$ contribution peaks strongly near threshold. It is fitted with a broad $0^{-+}$ resonance with mass $M = 1800 \pm 100$ MeV, width $\Gamma = 500 \pm 200$ MeV. A broad $2^{++}$ resonance peaking at 2020 MeV is also required with width $\sim 500$ MeV. There is further evidence for a $2^{-+}$ component peaking at 2.55 GeV. The non-$K^*\bar K^*$ contribution is close to phase space; it peaks at 2.6 GeV and is very different from $K^{*}\bar{K^{*}}$.Comment: 15 pages, 6 figures, 1 table, Submitted to PL

Measurements of the observed cross sections for exclusive light hadron production in e^+e^- annihilation at \sqrt{s}= 3.773 and 3.650 GeV

By analyzing the data sets of 17.3 pb$^{-1}$ taken at $\sqrt{s}=3.773$ GeV and 6.5 pb$^{-1}$ taken at $\sqrt{s}=3.650$ GeV with the BESII detector at the BEPC collider, we have measured the observed cross sections for 12 exclusive light hadron final states produced in $e^+e^-$ annihilation at the two energy points. We have also set the upper limits on the observed cross sections and the branching fractions for $\psi(3770)$ decay to these final states at 90% C.L.Comment: 8 pages, 5 figur