SpxA1 and SpxA2 act coordinately to fine-tune stress responses and virulence in Streptococcus pyogenes

SpxA is a unique transcriptional regulator highly conserved among members of the phylum Firmicutes that binds RNA polymerase and can act as an antiactivator. Why some Firmicutes members have two highly similar SpxA paralogs is not understood. Here, we show that the SpxA paralogs of the pathogen Streptococcus pyogenes, SpxA1 and SpxA2, act coordinately to regulate virulence by fine-tuning toxin expression and stress resistance. Construction and analysis of mutants revealed that SpxA1− mutants were defective for growth under aerobic conditions, while SpxA2− mutants had severely attenuated responses to multiple stresses, including thermal and oxidative stresses. SpxA1− mutants had enhanced resistance to the cationic antimicrobial molecule polymyxin B, while SpxA2− mutants were more sensitive. In a murine model of soft tissue infection, a SpxA1− mutant was highly attenuated. In contrast, the highly stress-sensitive SpxA2− mutant was hypervirulent, exhibiting more extensive tissue damage and a greater bacterial burden than the wild-type strain. SpxA1− attenuation was associated with reduced expression of several toxins, including the SpeB cysteine protease. In contrast, SpxA2− hypervirulence correlated with toxin overexpression and could be suppressed to wild-type levels by deletion of speB. These data show that SpxA1 and SpxA2 have opposing roles in virulence and stress resistance, suggesting that they act coordinately to fine-tune toxin expression in response to stress. SpxA2− hypervirulence also shows that stress resistance is not always essential for S. pyogenes pathogenesis in soft tissue

Theory of imaging a photonic crystal with transmission near-field optical microscopy

While near-field scanning optical microscopy (NSOM) can provide optical images with resolution much better than the diffraction limit, analysis and interpretation of these images is often difficult. We present a theory of imaging with transmission NSOM that includes the effects of tip field, tip/sample coupling, light propagation through the sample and light collection. We apply this theory to analyze experimental NSOM images of a nanochannel glass (NCG) array obtained in transmission mode. The NCG is a triangular array of dielectric rods in a dielectric glass matrix with a two-dimensional photonic band structure. We determine the modes for the NCG photonic crystal and simulate the observed data. The calculations show large contrast at low numerical aperture (NA) of the collection optics and detailed structure at high NA consistent with the observed images. We present calculations as a function of NA to identify how the NCG photonic modes contribute to and determine the spatial structure in these images. Calculations are presented as a function of tip/sample position, sample index contrast and geometry, and aperture size to identify the factors that determine image formation with transmission NSOM in this experiment.Comment: 28 pages of ReVTex, 14 ps figures, submitted to Phys. Rev.

Fuel cycles in nuclear reactors

Series numbering from publisher's list"61"--stamped on cover"Unclassified. NYO-2131."Originally issued by the first author as an Sc. D. thesis, Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1959Contract AT(30-1)-207

Velocity Visualization in Gaseous Flows

Techniques yielding simultaneous, multiple point measurements of velocity in reacting or nonreacting flow fields have the potential to significantly impact basic and applied studies of fluid mechanics. Several candidate schemes which could provide such measurement capability were investigated. The concepts utilize laser sources which lead to scattered light which can be monitored by a film based camera or a multielement solid state camera. Velocity measurements in supersonic flows using a novel Doppler modulated fluorescence concept are presented

Experiments with a Slow Neutron Velocity Spectrometer II

The apparatus previously used for the determination of neutron energy by time of flight method has been completely rebuilt with a view to increasing the accuracy of measurement as well as the high energy limit. The repetition frequency is obtained from a series of relaxation oscillators and a 50-kc oscillator and frequencies of 100, 200, 500, 1000, and 2500 c.p.s. are available. Four detector channels have been built so that neutrons in four different time of flight groups can be counted simultaneously. When used with the highest repetition frequency, this decreases the time to obtain data by a factor of 24 and has thus made the present experiments feasible with the small Cornell cyclotron. The study of the transmission of Ag with a 1.35-g/cm^2 absorber shows a single strong resonance at 5.8 ev. A re-examination of In with considerably higher resolution than was previously used shows a single resonance at about 1.35 ev. The effective mean life of neutrons in several different sources was examined and a thin paraffin source with Cd backing devised for measurements in the thermal region. The absorption of B has been examined and found to be proportional to 1/v within the limits of error of the experiment, from 0.028 to 50 ev. An experiment to determine the B cross section of the Cd stopped neutrons gave 540×10^(−24) cm^2. The B absorption curve shows that the cross section of thermal neutrons (0.025 ev) is 708×10^(−24) cm^2. It is concluded that the effective energy of the Cd stopped neutrons is not that of kT at thermal energy, for the geometry used, but is 0.041 ev. This conclusion is confirmed by the measured resonances in Ag and In which are higher than the values obtained by the boron absorption method. Correction of these values, as measured by Horvath and Salant (reference 4) for the effective energy of the Cd stopped neutrons, leads to 1.32 ev for In and 5.2 ev for Ag, in agreement with the present results. It is concluded that resonances measured by the boron absorption method are in error by an amount which depends upon the geometry of the experiment, and are probably too low by a factor of 0.041/0.025 = 1.64

Correlated defects, metal-insulator transition, and magnetic order in ferromagnetic semiconductors

The effect of disorder on transport and magnetization in ferromagnetic III-V semiconductors, in particular (Ga,Mn)As, is studied theoretically. We show that Coulomb-induced correlations of the defect positions are crucial for the transport and magnetic properties of these highly compensated materials. We employ Monte Carlo simulations to obtain the correlated defect distributions. Exact diagonalization gives reasonable results for the spectrum of valence-band holes and the metal-insulator transition only for correlated disorder. Finally, we show that the mean-field magnetization also depends crucially on defect correlations.Comment: 4 pages RevTeX4, 5 figures include

Understanding the role of shame and its consequences in female hypersexual behaviours: A pilot study

Background and aims: Hypersexuality and sexual addiction among females is a little understudied phenomenon. Shame is thought to be intrinsic to hypersexual behaviours, especially in women. Therefore, the aim of this study was to understand both hypersexual behaviours and consequences of hypersexual behaviours and their respective contributions to shame in a British sample of females (n = 102). Methods: Data were collected online via Survey Monkey. Results: Results showed the Sexual Behaviour History (SBH) and the Hypersexual Disorder Questionnaire (HDQ) had significant positive correlation with scores on the Shame Inventory. The results indicated that hypersexual behaviours (HBI and HDQ) were able to predict a small percentage of the variability in shame once sexual orientation (heterosexual vs. non-heterosexual) and religious beliefs (belief vs. no belief) were controlled for. Results also showed there was no evidence that religious affiliation and/or religious beliefs had an influence on the levels of hypersexuality and consequences of sexual behaviours as predictors of shame. Conclusions: While women in the UK are rapidly shifting to a feminist way of thinking with or without technology, hypersexual disorder may often be misdiagnosed and misunderstood because of the lack of understanding and how it is conceptualised. The implications of these findings are discussed

Mesoscopic molecular ions in Bose-Einstein condensates

We study the possible formation of large (mesoscopic) molecular ions in an ultracold degenerate bosonic gas doped with charged particles (ions). We show that the polarization potentials produced by the ionic impurities are capable of capturing hundreds of atoms into loosely bound states. We describe the spontaneous formation of these hollow molecular ions via phonon emission and suggest an optical technique for coherent stimulated transitions of free atoms into a specific bound state. These results open up new interesting possibilities for manipulating tightly confined ensembles.Comment: 4 pages (two-columns), 2 figure