Martian bow shocks, the solar wind interacting with an unmagnetized planet,
are studied. We theoretically investigated how solar parameters, such as the
solar wind dynamic pressure and the solar ...extreme ultraviolet (EUV) flux,
influence the bow shock location, which is still currently not well understood.
We present the formula for the location of the bow shock nose of the
unmagnetized planet. The bow shock location, the sum of the ionopause location
and bow shock standoff distance, is calculated in the gasdynamics approach. The
ionopause location is determined using thermal pressure continuity, i.e., the
solar wind thermal pressure equal to the ionospheric pressure, according to
tangential discontinuity. The analytical formula of the ionopause nose location
and the ionopause profile around the nose are obtained. The standoff distance
is calculated using the empirical model. Our derived formula shows that the
shock nose location is a function of the scale height of ionosphere, the
dynamic pressure of the solar wind and the peak ionospheric pressure. The
theoretical model implies that the shock nose location is more sensitive to the
solar EUV flux than solar wind dynamics pressure. Further, we theoretically
show that the bow shock location is proportional to the solar wind dynamic
pressure to the power of negative C, where C is about the ratio of the
ionospheric scale height to the distance between bow shock nose and the planet
center. This theory matches the gasdynamics simulation and is consistent with
the spacecraft measurement result by Mars Express Hall, et al. (2016) J.
Geophys. Res. Space Physics, 121, 11,474-11,494.
Swarming motility is a multicellular phenomenon comprising population migration across surfaces by specially differentiated cells. In Serratia marcescens, a network exists in which the flhDC ...flagellar regulatory master operon, temperature, nutrient status, and quorum sensing all contribute to the regulation of swarming motility. In this study, the rsmA (repressor of secondary metabolites) gene (hereafter rsmASm) was cloned from S. marcescens. The presence of multicopy, plasmid-encoded rsmASm expressed from its native promoter in S. marcescens inhibits swarming. Synthesis of N-acylhomoserine lactones, presumably by the product of smaI (a luxI homolog isolated from S. marcescens), was also inhibited. Knockout of rsmASm on the S. marcescens chromosome shortens the time before swarming motility begins after inoculation to an agar surface. A single copy of the chromosomal PrsmASm::luxAB reporter of rsmASmtranscription was constructed. Using this reporter, the roles of the flhDC flagellar regulatory master operon, temperature and autoregulation in the control of rsmASm expression were determined. Our findings indicate that RsmASm is a component of the complex regulatory network that controls swarming.
Wilms' tumour (nephroblastoma) is the most common renal tumour in children. Wilms' tumour in adults is extremely rare and has a poorer prognosis than paediatric Wilms' tumour. It is difficult to ...differentiate adult Wilms' tumour from renal cell carcinoma based on radiological findings alone. The diagnosis in adults is often serendipitous following nephrectomy for presumed renal cell carcinoma. Because of the paucity of literature, there are no standard protocols for the management of adult Wilms' tumour, and therefore, it is managed as per paediatric Wilms' tumour. Herein, we report the case of adult Wilms' tumour in a 43-year-old man, which was diagnosed unexpectedly following nephrectomy for presumed renal cell carcinoma.
We investigated in Serratia marcescens the functions of the flhDC operon, which controls motility and cell division in enteric bacteria. Included in our evaluations were investigation of cell ...division, flagellar synthesis and regulation of the expression of nuclease (encoded by the nucASm gene, one of the virulence factors). Interruption of the chromosomal flhDC operon in S. marcescens CH-1 resulted in aberrant cell division and loss of nuclease and flagella. Expression of nucASm and other mutated phenotypes was restored in the flhDC mutant by the induction of overexpression of flhDC in a multicopy plasmid. Multicopied flhDC also induced the formation of differentiated cells (polyploid aseptate cells with oversynthesis of peritrichous flagella) in broth culture using minimal growth medium. Expression of the flhDC operon showed positive autoregulation, and was growth phase dependent (upregulated in early log phase). In addition, flhDC expression was inhibited when the temperature increased from 30 to 37°C, and when osmolarity was increased, but was not influenced by glucose catabolite repression. These results show that FlhD/FlhC is a multifunctional transcriptional activator involved in the process of cell differentiation, swarming and virulence factor expression.
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