External modulation method for generating accurate linear optical FMCW

Frequency modulation continuous wave (FMCW) lasers are key components in modern optical imaging. However, current intracavity modulation lasers do not exhibit low-frequency jitter rate and high linearity due to the inherent relaxation oscillations. Although this may be compensated in a direct modulation laser diode using an optoelectronic feedback loop, the available sweep speed is moderately small. In this letter, a special external modulation method is developed to improve the performance of FMCW. Since only the first sideband optical field is used during the entire generation process, phase noise is kept to a minimum and is also independent of the sweep speed. We demonstrate that the linearity and jitter rates do not deteriorate appreciably when the sweep speed is changed over three orders of magnitude, even up to the highest sweep speed of 2.5 GHz/ μs

Petrogenesis and geological significance of migmatitic gneiss in Mulantou area, Hainan Island

In the coastal area of Pujian to Mulantou on Hainan Island, a set of medium to deep metamorphic rocks (Mulantou complex) has been discovered, composed of migmatite, dolomite, shale, and amphibolite, with migmatite being the predominant lithology. This study selected well-developed and typical migmatitic gneisses as the research focus and conducted systematic zircon U-Pb isotope dating and petrological and geochemical studies. The results indicate that the protolith of the Mulantou migmatitic gneisses was intermediate basic volcanic rock formed around 276 Ma. These rocks exhibit geochemical characteristics of island-arc calc-alkaline basalt, suggesting a tectonic setting related to the subduction of the Paleo-Tethys Ocean. Early anatectic metamorphism occurred around 261 Ma, indicating a tectonic environment related to the collision between the South China Block and the Indochina Block. Later metamorphism took place around 248 Ma, signifying a tectonic environment associated with extension following the collision between the South China Block and the Indochina Block. Therefore, the Mulantou migmatitic gneisses preserve a comprehensive record of the tectonic evolution in Hainan Island from the Early Permian to the Early Triassic. They represent the geological consequences of events such as the closure of the Paleo-Tethys Ocean, the collision between the South China Block and the Indochina Block, and the subsequent extension. The discovery of these rocks provides new insights into the eastern extension of the Song Ma suture zone

Unraveling the Mode of Action of <i>Cordyceps fumosorosea</i>: Potential Biocontrol Agent against <i>Plutella xylostella</i> (Lepidoptera: Plutellidae)

The entomopathogenic fungus, Cordyceps fumosorosea is a potential eco-friendly biocontrol agent. The present study revealed the entire course of infection of P. xylostella by C. fumosorosea with particular reference to cuticular penetration. Comparative studies on the infection of Plutella xylostella larvae by two strains of C. fumosorosea with different pathogenicity were carried out using light, scanning, and transmission electron microscopy. We found that C. fumosorosea tended to adhere to the cuticle surfaces containing protrusions. Although conidia of the lower pathogenic strain IFCF-D58 germinated, they failed to penetrate and complete the development cycle. In contrast, the higher pathogenic strain IFCF01 began to germinate within 4 h and attached to the cuticle by a thin mucilaginous matrix within 8 h post-inoculation. After 24 h post-inoculation, germ tubes and penetrating hyphae reached the cuticular epidermis and began to enter the haemocoel. Within 36 h post-inoculation, the hyphal bodies colonized the body cavity. Hyphae penetrated from inside to outside of the body after 48 h and sporulated the cadavers. After 72 h post-inoculation, numerous conidia emerged and the mycelial covered the entire cuticular surface. The two strains showed similarities in terms of conidial size and germination rate. However, IFCF-D58 exhibited significantly fewer appressoria and longer penetrating hyphae compared to the more infective IFCF01 on all surface topographies. The current pathogen invasion sequence of events suggested that the aggressive growth and propagation along with rapid and massive in vivo production of blastospores facilitate the conidia of IFCF01 to quickly overcome the diamondback moth’s defense mechanism