Detecting domain walls of axionlike models using terrestrial experiments.

Stable topological defects of light (pseudo)scalar fields can contribute to the Universe's dark energy and dark matter. Currently, the combination of gravitational and cosmological constraints provides the best limits on such a possibility. We take an example of domain walls generated by an axionlike field with a coupling to the spins of standard-model particles and show that, if the galactic environment contains a network of such walls, terrestrial experiments aimed at the detection of wall-crossing events are realistic. In particular, a geographically separated but time-synchronized network of sensitive atomic magnetometers can detect a wall crossing and probe a range of model parameters currently unconstrained by astrophysical observations and gravitational experiments.

[Photogeneration of the superoxide anion oxygen radical and its role in the inactivation of yeast cells by long-wave UV light]. / Fotogeneratsiia superoksidnogo anion-radikala kisloroda i ego rol' v inaktivatsii kletok drozhzhei dlinnovolnovym UF-svetom.

Long-wave (320-400 nm) UV-induced oxygen superoxide anion radical (O2-) formation was found in yeast cells. This radical plays an important part in initiation of photodestruction reactions in DNA which serves as a main target of UV irradiation in yeast. The observed cell photoinactivation spectrum at the wavelengths 320-400 nm suggests that NADH can serve as an endogenous sensitizer of O2- formation.

[Role of DNA damage in the inactivation of Saccharomyces cerevisiae yeasts by 313-nm ultraviolet light]. / Rol' povrezhdeniia DNK v inaktivatsii drozhzhei Saccharomyces cerevisiae ul'trafioletovym svetom 313 nm.

The relative contribution of respiration photoinhibition and DNA damage in the lethal effect induced by 313 nm ultraviolet light (UV) has been investigated in some strains of the yeast Saccharomyces cerevisiae. It has been shown that cells inactivation is essentially due to photo-induced damage to DNA. By photoreactivation experiments it has been found that dimers of the pyrimidine bases are the main lethal photoproducts induced in the DNA by 313 nm ultraviolet light.

[Concurrent effect of ultraviolet rays of various wave lengths on Saccharomyces cerevisiae survival]. / Konkurentnoe deistvie ul'trafioletovykh luchei raznoi dliny volny na vyzhivaemost' Saccharomyces cerevisiae.

While studying the combined action of different UV wavelengths on Saccharomyces cerevisiae (strains XII and Cl-9), it has been found that preliminary irradiation with UV at 334 nm caused photoprotection of the cells against the lethal action of UV at 254 and 313 nm. Postradiation irradiation of strain XII incapable of photoreactivation with UV at 334 nm increased the lethal action of UV at 254 and 313 nm. The mechanisms of the both effects are based on serotonin synthesis induced by the light at 334 nm, as was shown using p-chlorophenylalanine, a specific inhibitor of serotonin synthesis. In strain CI-9 capable of photoreactivation, the postradiation effect of the light at 334 nm depends on the interaction of two different photobiological reactions induced by it, namely, photoreactivation and induced serotonin synthesis.

[Preliminary and postradiation effect of long-wave ultraviolet rays on cells of different species of Candida irradiated with short-wave ultraviolet rays]. / Predvaritel'noe i postradiatsionnoe deistvie dlinnovolnovykh ul'trafioletovykh luchei na kletki razlichnykh vidov Candida, obluchennykh korotkovolnovym ul'trafioletom.

Certain characteristics of photoprotection induced by near-UV were studied in Candida guilliermondii. Candida tropicalis was also capable of photoprotection from the lethal effect of far-UV. The spectrum of action of photoprotection was recorded. The photoprotective effect was not found in Candida utilis. The postradiation effect of near-UV was studied. The lethal action of far-UV was intensified in C. guilliermondii and C. tropicalis incapable of photoreactivation in contrast to C. utilis capable of photoreactivation.

[Effect of long-wave ultraviolet light (313 nm) on the survivability and respiration of Candida utilis yeasts]. / Vliianie dlinnovolnvogo ul'trafioletovogo sveta 313 nm na vyzhivaemost' i dykhanie drozhzhei Candida utilis.

Irradiation of Candida utilis with near-UV (313 nm) was found to inhibit respiration; the degree of the inhibition correlated with the number of killed cells. Irradiation of the yeast mitochondria inhibited the activity of succinate oxidase; the dependence of the inhibition on the dose of near-UV (313 nm) was close to the dose dependence of the photoinhibition of respiration in whole cells. The action spectrum for the inhibition of the activity of succinate oxidase was recorded; it corresponded to the absorption spectrum of ubiquinone isolated from the yeast cells. The data obtained suggest that ubiquinone is a target molecule in the effects of inhibition of respiration and death of yeast cells induced with near-UV (313 nm).

[Repair of damage caused by 313 nm light and photoprotection in Candida guilliermondii]. / Reparatsiia povrezhdenii, indutsiruemykh svetom 313 nm, i fotozashchita u drozhzhei Candida guilliermondii

The study of the effect of near-UV light (300-380 nm) on the yeast Candida guilliermondii has shown that certain doses of 313 nm light cause inactivation which is reversible after the cells have been kept for some time in a non-nutrient medium. The findings suggest a different nature of the lesions resulting in killing the cells irradiated with light of 313 and 254 nm. The data obtained are interpreted in terms of a new, yet unknown, repair mechanism, other than the classical dark reparation, which is involved in the recovery of cells inactivated by light of 313 nm. Non-lethal doses at 313 nm induce photoprotection of the cells against UV lesions. The effect was compared with the photoprotection described in literature, and was found to be different.

Phytochrome system of the yeast Candida guilliermondii and recovery from ultraviolet injury.

The effect of red (660 nm) and far-red (730 nm) light on the stability of the yeast Candida guilliermondii to lethal u.v. radiation has been studied. Reactivation and protection were exhibited for 30 min after treatment with red light and were abolished by far-red exposure applied within this time period. The temperature dependence of the reactivation effect was also studied. The data obtained showed that the properties of recovery and protection against u.v. exposure are associated with the phytochrome system of the yeast.