Abstract. Weld residual stresses often approach, or exceed, the yield strength of the material, with serious implications for the integrity of engineering structures. It is not always feasible to measure residual stresses, so integrity assessments often rely heavily on numerical models. In ferritic steels, the credibility of such models depends on their ability to account for solid-state phase transformations that can have a controlling effect on the final residual stress state. Furthermore, a better understanding of weld transformations provides an opportunity to engineer the weld stress state and microstructure for improved life. In this paper the complementary merits of synchrotron X-ray and neutron diffraction are exploited both to verify and refine weld models and to inspire the development of weld filler metals to control weld stresses. In terms of weld filler metal design, Xray diffraction is used to characterize phase transformations in real time during realistic weld cooling cycles, for understanding small-scale behaviour, and identifying features that need to be incorporated into finite-element models. Meanwhile, neutron diffraction is used to elucidate the practical consequences of solid-state phase transformations on the macroscopic scale, thereby providing crucial validatory structural integrity data.

Attosecond science capitalizes on the extreme nonlinearity of strong fields, driven by few-cycle pulses, to attain attosecond temporal resolution and give access to the electron motion dynamics of matter in real-time. Here, we measured the electronic delay response of the dielectric system triggered by a strong field of few-cycle pulses to be in the order of 425 ± 98 as. Moreover, we exploited the electronic response following the strong driver field to demonstrate all-optical light field metrology with attosecond resolution. This field sampling methodology provides a direct connection between the driver field and the induced ultrafast dynamics in matter. Also, we demonstrate the quantum electron motion control in dielectric using synthesized light waveforms. This on-demand electron motion control realizes the long-anticipated ultrafast optical switches and quantum electronics. This advancement promises to increase the limiting speed of data processing and information encoding to rates that exceed 1 petabit/s, opening a new realm of information technology. Main text:Advancements in attosecond pulse generation and spectroscopic measurements by high harmonic generation in gases and solids opened a new window to study the electronic response driven by strong fields in real-time [1][2][3][4][5][6][7][8][9][10][11] . The strong-field-induced electron dynamics and the related phase transition to a semimetal-like state of dielectric systems have been studied theoretically [12][13][14][15] and experimentally by XUV attosecond spectroscopy [16][17][18][19] . Accordingly, the strong-field interaction induces a current in the dielectric nanocircuit as

Mitochondrial nucleoids isolated from mung bean seedlings exhibited a chromatin-like structure associated with a membrane component. A similar structure, which underwent discrete changes during cotyledon development, was identified in situ. Isolated nucleoids consisted of essentially the same phospholipids, including cardiolipin, as whole mitochondria and proteins of inner- and outer-mitochondrial-membrane origin. Actin was consistently found with mitochondrial nucleoids prepared with different detergent concentrations. Formaldehyde cross-linking of cytochalasin B- and proteinase K-treated mitochondria further revealed that actin was associated with DNA in nucleoids. Mitochondrial nucleoids were self-sufficient in directing DNA synthesis in vitro in a pattern mimicking mtDNA synthesis in isolated mitochondria. In pulse-field gel electrophoresis, newly synthesized mtDNA separated into two major components, well-bound and fast-moving forms. Nucleoids DNA synthesis was resistant to aphidicolin but sensitive to N-ethylmaleimide, which indicates that a γ-type DNA polymerase was responsible for this activity. Mitochondrial nucleoids were capable of self-directed RNA transcription in a non-random fashion in vitro. Consistent with and complementary to results from fungi and human cells done mostly in situ, our present work helps to establish the important paradigm that mitochondrial nucleoids in eukaryotes are more than mere mtDNA compaction and segregation entities but are centers of mtDNA maintenance and expression.

The currently accepted model of recombination-dependent replication (RDR) in plant mitochondrial DNA (mtDNA) does not clearly explain how RDR progresses and how highly complex mtDNA develops. This study aimed to investigate the correlation between RDR and mtDNA complexity during mitochondrial development in mung bean (Vigna radiata) seed, and the initiation and processing of RDR in plant mitochondria. Flow cytometry, pulsed-field gel electrophoresis, electron microscopy, real-time PCR and biochemical studies were used in this study. The highly dynamic changes in mtDNA complexity correspond to mtDNA RDR activity throughout mitochondrial development. With in vitro freeze-thaw treatment or prolonged in vivo cold incubation, the mtDNA rosette core disappeared and the rosette structure converted to a much longer linear DNA structure. D-loops, Holliday junctions and putative RDR forks often appeared near the rosette cores. We hypothesize that the rosette core may consist of condensed mtDNA and a replication starting sequence, and play an initial and central role in RDR. The satellite cores in the rosette structure may represent the re-initiation sites of mtDNA RDR in the same parental molecule, thereby forming highly complex and giant mitochondrial molecules, representing the RDR intermediates, in vivo.

No abstract