提高植树造林树木成活率技术措施探析——以双辽为例

植树造林是林业发展的基础。目前,在实际的植树造林工作中,普遍出现了植物选择不合理、灌溉施肥不到位以及后期管理不科学等问题。为了保证林木行业健康发展,文章分析了影响植树造林树木成活率的因素,总结了提高植树造林树木成活率的技术措施,希望对广大同行有所帮助。

In-situ TEM observation of the evolution of helium bubbles in Mo during He^(+)irradiation and post-irradiation annealing

The evolution of helium bubbles in purity Mo was investigated by in-situ transmission electron microscopy(TEM)during 30 keV He^(+)irradiation(at 673 K and 1173 K)and post-irradiation annealing(after 30 keV He^(+)irradiation with the fluence of 5.74×10^(16)He^(+)/cm^(2)at 673 K).Both He^(+)irradiation and subsequently annealing induced the initiation,aggregation,and growth of helium bubbles.Temperature had a significant effect on the initiation and evolution of helium bubbles.The higher the irradiation temperature was,the larger the bubble size at the same irradiation fluence would be.At 1173 K irradiation,helium bubbles nucleated and grew preferentially at grain boundaries and showed super large size,which would induce the formation of microcracks.At the same time,the geometry of helium bubbles changed from sphericity to polyhedron.The polyhedral bubbles preferred to grow in the shape bounded by{100}planes.After statistical analysis of the characteristic parameters of helium bubbles,the functions between the average size,number density of helium bubbles,swelling rate and irradiation damage were obtained.Meanwhile,an empirical formula for calculating the size of helium bubbles during the annealing was also provided.

Unconventional energetics of small vacancy clusters in BCC high-entropy alloy Nb_(0.75)ZrTiV_(0.5)

The stability of small vacancy clusters including divacancy,trivacancy and tetravacancy has been studied in body-centered cubic high-entropy alloy Nb_(0.75)ZrTiV_(0.5) in structures of random solid solution and short-range order by first-principles calculations and molecular dynamics simulations.Different from conventional body-centered cubic metals,the tightly bound configurations have a lower structural stability and are not preferred energetically in the studied high-entropy alloy.Instability of vacancy configurations leads to vacancy-atom exchanges that favor less compact configurations.The formation energy of small vacancy clusters is much smaller than its constituent elements of Nb and V due to the large structural adjustment induced by severe local lattice distortion.The difference in local lattice distortion and elemental arrangement in the vacancy neighborhood leads to significant site-to-site variation in vacancy cluster energy and configuration.The formation energy has a strong correlation with the local energy state of the vacancy configuration and the extent of structural relaxation.Compared to random solid solution,the structure of short-range order has a higher stability for the most compact cluster configurations and tends to have higher vacancy cluster formation energy.According to classical molecular dynamics simulations of cluster diffusion at high temperature,the studied high-entropy alloy has a higher probability of cluster dissociation compared to Nb and V.The unconventional energetics of small vacancy clusters is expected to have a profound impact on their generation,diffusion,dissociation,coalescence,as well as the defect microstructure evolution during irradiation.

Berbamine inhibits proliferation and induces apoptosis of KU812 cells by increasing Smad3 activity

Objective: The cytotoxic effect of berbamine on chronic myeloid leukemia (CML) cell line KU812 was evaluated,and the mechanisms of its action were explored.Methods: The effect of berbamine on the KU812 cell growth was determined by methyl thiazolyl tetrazolium (MTT) assay.Flow cytometry was used to profile cell cycle alteration upon berbamine treatment.Reverse transcription polymerase chain reaction (RT-PCR) was carried out to determine the transcripts of transforming growth factor-β (TGF-β) receptors (TβRs),Smad3,c-Myc,cyclin D1,p21Cip1(p21),and p27Kip1(p27).Changes in the protein levels of total Smad3,phosphorylated Smad3,the downstream targets of Smad3,and specific apoptosis-related factors were evaluated by Western blotting.Results: Berbamine inhibited KU812 cell proliferation in a doseand time-dependent manner,and the half maximal inhibitory concentration (IC50) values for treatments of 24,48,and 72 h were 5.83,3.43,and 0.75 μg/ml,respectively.Berbamine induced G1 arrest as well as apoptosis in KU812 cells.Transcriptions of Smad3 and p21 were up-regulated,while those of TβRI,TβRII,c-Myc,cyclin D1 and p27 were not changed significantly.The protein levels of both total Smad3 and phosphorylated Smad3 were both up-regulated after berbamine treatment,together with decreased c-Myc and cyclin D1 and increased p21.Meanwhile,the levels of the anti-apoptotic proteins,such as Bcl-2 and Bcl-xL,were decreased,whereas pro-apoptotic Bax was increased.Conclusions: Berbamine suppresses KU812 cell proliferation through induction of cell cycle arrest in G1 and apoptosis.It activates Smad3 without additional stimulation of TGF-β,and alters the levels of the Smad3 downstream targets,including c-Myc,cyclin D1 and p21.Our findings suggest that berbamine is a promising drug in the treatment of advanced stage patients with CML.

Authors' response

For the Letter to the Editor "Emerging role of berbamine as an anti-cancer agent in systemic malignancies besides chronic myeloid leukemia",we are pleased with the interest in our article (Liang et al.,2011),and appreciate the insightful comments made by Dr.Kapoor (2012).He systemically reviewed application of berbamine as an anti-cancer agent during the past few years and found that berbamine also shows anti-cancer activity for other systemic malignancies besides chronic myeloid leukemia.Extensive scrutiny of its molecular targets and mechanism of action in the past few decades has provided important insights.

In-situ TEM study of the effect of hydrogen-helium ratio on defect characteristics in Fe9Cr1.5W0.4Si F/M steel during H_(2)^(+)&He^(+)simultaneous irradiation

The effect of hydrogen and helium interaction,especially H-He ratio,on the irradiation behavior of nuclear materials has not yet been resolved.However,this is an important basis for evaluating the irradiation properties of nuclear materials and developing high irradiation resistant materials.Here,30 keV H_(2)^(+)and He^(+)dual beams with four H-He ratios of 0:10,3:10,15:10,and 30:10 were used to irradiate the newly developed Fe9Cr1.5W0.4Si F/M steel in TEM to in-situ study the interaction and ratio effect of hydrogen and helium.The addition of H atoms significantly promoted the nucleation of dislocation loops and bubbles.In the early stage of irradiation,the average size and density of dislocation loops increased with the increase of H-He ratio.Meanwhile,the larger the H-He ratio,the easier it was to form a complex dislocation network.Furthermore,the final saturation size of bubbles increased with the increase of H-He ratio.It was first found that the swelling was affected by H concentrations,with high H concentrations slowing down the increase in swelling.For a certain irradiation dose,a specific H-He ratio would lead to a swelling peak of Fe9Cr1.5W0.4Si F/M steel.The super-sized bubbles at grain boundaries(GBs)were found after H addition,resulting in a bigger swelling of GBs than the matrix.Both the swelling of the GBs and the matrix show a dependence on the H-He ratio.The current work is of great significance for understanding the interaction between hydrogen and helium in nuclear materials.