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Recently, the red giant V723 Mon is reported to have an unseen companion with a mass of $3.04\pm0.06M_{\odot}$, but question remains about whether it is a single (thus the so-called mass-gap) black hole or an inner binary of two more ordinary compact objects (neutron stars or white dwarfs). In this work, we estimate the X-ray emission by considering the wind-fed accretion from V723 Mon onto the compact companion. We analyze three different scenarios of the dark companion, i.e., a single black hole, binary neutron stars and binary of a neutron star and a white dwarf. We show that the single black hole is the most favored scenario. We also calculate the synchrotron emission from the bow shock caused by the interaction of the compact companion with the wind. We find this emission peaks at $\sim$ 0.1-1 GHz, with a flux density $\sim$ 1 mJy, which is expected to be detected by observations with higher angular resolution in the future., 8 pages, 2 figures, 1 table, submitted to MNRAS

We have developed a companion-planted grow seedlings technique,based on the plastic hole plate method used for large-scale crop seedling production,for growing gramineous crops in combination with target crops such as cotton,rape,tomato,and peanut in the same planting hole.This new grow seedlings method takes advantage of the fibrous root system of gramineous crops to keep the root system of growing seedlings tightly bound together,thus preventing damage to seedling root systems during removal from plastic hole trays and mechanical transplantation into the field.Because of its superior suitability for mechanical transplantation,the technique increases the survival percentage of transplanted seedlings,shortens the post-transplantation convalescence period,and improves target crop quality.To elucidate the mechanisms responsible for enhancing crop seedling quality when two crops are grown in the same hole,we studied the eco-physiological effects of the new technique on soil microorganism quantity,enzyme activity,and root secretion,as well as target crop root vigor and soluble sugar and adenosine triphosphate leaf content.Wheat,maize,millet,and sorghum were used to promote seedling growth of target crops such as cotton,rape,tomato,peanut,peony,and tobacco.Seeds were sown in 532×280 mm2 plastic trays containing 200 square holes with soil as a substrate,and the resulting seedlings were grown under natural light conditions at 20—30℃ in plastic sheds.When crop seedlings were companion-grown in this fashion,the number of bacteria and actinomycetes in the matrix soil increased significantly—by 52.80%—102.76% and 34.11%—76.48%,respectively—and the number of fungi in the soil decreased by 44.33%—56.14%.Soil enzyme activity also increased significantly;for example,increased activity was observed for dehydrogenase(30.57%—66.37%),neutral phosphatase(38.17%—54.37%),invertase(23.74%—35.04%),and urease(60.25%—85.47%).At the same time,significant decreases were detected in root exudates,including 2,4-di-tert-butylphenol(32.80%—51.65%),2,6-di-tert-butylphenol(36.60%—56.59%),dibutyl phthalate(10.42%—49.99%),and methyl palmitoleate(25.62%—55.59%).Root vigor and soluble sugar and adenosine triphosphate content in leaves of target crops increased significantly.As a consequence,root weight,seedling weight,and lateral roots of target crops increased;these results revealed robust growth,strong photosynthetic capacity,and greater reserve power,which laid the material and energy foundation for quick regrowth and enhanced survival of transplanted seedlings.Among treatments,the most favorable results were obtained for cotton-wheat,cotton-millet,rape-millet,tomato-wheat,tomato-millet,peanut-wheat,peanut-millet,peony-millet,and tobacco-millet combinations.In conclusion,the quantity and colony composition of soil microorganisms was improved when two seedlings of two crops were companion-planted in the same hole.This soil microorganism enhancement may have been the primary cause of increased soil enzyme activity and decreased accumulation of detrimental root exudates;it would help reduce crop auto-toxicity and improve soil nutritional conditions,thus boosting target crop seedling quality.Soil microorganisms play an important role in soil nutrition transformation,organic matter decomposition,detrimental material degradation,and soil fertility recovery.In addition,they can produce growth stimulants and antibiotics,which stimulate crop growth and suppress growth of harmful microorganisms,respectively.The improved soil microorganism composition and increased soil enzyme activity observed when seedlings of two crops were companion-planted may be related to additive effects of root system exudates from the two crops;both crop type and nutritional situation may affect the quantity and type of these secretions,which enhance soil microbe quantity and soil enzyme activity.

The polarization errors of optical circuit limit the accuracy of the quasi-reciprocal reflective optical voltage sensor.The transmission models of discrete optical components and the splice points were developed based on the theory of Jones matrix.Also,a comprehensive transmission model of optical system was derived.The influences of polarization errors on the system performance were analyzed and simulated theoretically.The theoretical and experimental results show that the sensitivity is dependent on factors including the degree of polarization of the light source,the extinction ratio of the polarizer and the azimuth angle between the principle axes of the polarizer and the modulator,the polarization errors induced by which exhibit no influences on the accuracy when the gain of the electrical circuit is large enough.The polarization errors induced by the rotation angle of Faraday rotator,the azimuth angle of the collimator-Faraday rotator with respect to the BGO crystal can mainly result in measurement error,which is sensitive to the environmental changes and brings on the output drift.According to the standard of IEC 60044-7 0.2S,the rotation angle of Faraday rotator and the azimuth angle between collimator-Faraday rotator and BGO crystal should be less than 1.6° and 1.85°,respectively.It is also useful to the design of the optical circuit and the errors compensation of the quasi-reciprocal reflective optical voltage sensor.