Generation of short hard X-ray pulses of tailored duration using a M\"ossbauer source

We theoretically investigate a scheme for generations of single hard X-ray pulses of controllable duration in the range of 1 ns - 100 ns from a radioactive M\"ossbauer source. The scheme uses a magnetically perturbed $^{57}$FeBO$_3$ crystal illuminated with recoilless 14.4 keV photons from a radioisotope $^{57}$Co nuclide. Such compact X-ray source is useful for the extension of quantum optics to 10 keV energy scale which has been spotlighted in recent years. So far, experimental achievements are mostly performed in synchrotron radiation facilities. However, tabletop and portable hard X-ray sources are still limited for time-resolved measurements and for implementing coherent controls over nuclear quantum optics systems. The availability of compact hard X-ray sources may become the engine to apply schemes of quantum information down to the subatomic scale. We demonstrate that the present method is versatile and provides an economic solution utilizing a M\"ossbauer source to perform time-resolved nuclear scattering, to produce suitable pulses for photon storage and to flexibly generate X-ray single-photon entanglement.Comment: 8 pages, 6 figure

Al-Mg systematics of hibonite-bearing Ca,Al-rich inclusions from Ningqiang

Hibonite-bearing Ca,Al-rich inclusions (CAIs) usually occur in CM and CH chondrites and possess petrographic and isotopic characteristics distinctive from other typical CAIs. Despite their highly refractory nature, most hibonite-bearing CAIs have little or no ^(26)Mg excess (the decay product of ^(26)Al), but do show wide variations of Ca and Ti isotopic anomalies. A few spinel-hibonite spherules preserve evidence of live ^(26)Al with an inferred ^(26)Al/^(27)Al close to the canonical value. The bimodal distribution of ^(26)Al abundances in hibonite-bearing CAIs has inspired several interpretations regarding the origin of short-lived nuclides and the evolution of the solar nebula. Herein we show that hibonite-bearing CAIs from Ningqiang, an ungrouped carbonaceous chondrite, also provide evidence for a bimodal distribution of ^(26)Al. Two hibonite aggregates and two hibonite-pyroxene spherules show no ^(26)Mg excesses, corresponding to inferred ^(26)Al/^(27)Al < 8 × 10^(−6). Two hibonite-melilite spherules are indistinguishable from each other in terms of chemistry and mineralogy but have different Mg isotopic compositions. Hibonite and melilite in one of them display positive ^(26)Mg excesses (up to 25‰) that are correlated with Al/Mg with an inferred ^(26)Al/^(27)Al of (5.5 ± 0.6) × 10^(−5). The other one contains normal Mg isotopes with an inferred ^(26)Al/^(27)Al < 3.4 × 10^(−6). Hibonite in a hibonite-spinel fragment displays large ^(26)Mg excesses (up to 38‰) that correlate with Al/Mg, with an inferred ^(26)Al/^(27)Al of (4.5 ± 0.8) × 10^(−5). Prolonged formation duration and thermal alteration of hibonite-bearing CAIs seem to be inconsistent with petrological and isotopic observations of Ningqiang. Our results support the theory of formation of ^(26)Al-free/poor hibonite-bearing CAIs prior to the injection of ^(26)Al into the solar nebula from a nearby stellar source

The Role of Polyamines in Osmotic Stress Tolerance in Gulf Killifish Fundulus Grandis

Polyamines are a diverse class of aliphatic molecules that are highly polycationic at physiological intracellular pH. Polyamine levels are regulated by the coordinated actions of arginase (Arg), ornithine decarboxylase (Odc), and polyamine oxidase (Pao). Although little is known of their functions in fish, polyamines have been implicated in diverse physiological processes, including RNA transcription, cell growth, cell proliferation, and cell apoptosis. The main objective of this study was to describe the transcription and enzymatic activities of key enzymes for polyamine metabolism, to measure polyamine levels, and to assess putative roles of polyamines in the gills of the Gulf killifish (Fundulus grandis) during hypoosmotic challenge. In addition, the influence of irreversible inhibition of Odc by alpha-DL-difluoromethylornithine (DFMO) was assessed in the gills. Furthermore, the transcription and enzymatic activities of Arg, Odc and Pao was assessed in other tissues such as intestine and liver during hypoosmoitc challenges. Adult F. grandis were reared in 5 ppt and acutely transferred to 5, 2, 1, 0.5, and 0.1 ppt water, and gills were sampled at 6 h, 1 d, 3 d, and 7 d post-transfer. Results showed that arg II and odc mRNA levels were highly upregulated in the gills during the first few days post-transfer to hypoosmotic water. Hypoosmotic exposure also produced increases in gill Odc activity and in the concentrations of putrescine, spermidine, and spermine. DFMO application inhibited Odc activity and reduced polyamine levels after hypoosmotic exposure (0.1 ppt). Although gill putrescine levels remained elevated throughout the first 7 d post transfer to 0.1 ppt, the concentrations of spermidine and spermine decreased over time. The ratio of putrescine level over the sum levels of spermidine and spermine increased after 0.1 ppt exposure at 1 d and beyond. Concomitant with freshwater acclimation, an increase in Pao activity suggested that polyamine catabolism was upregulated in the gills. The phenotype of mitochondrion-rich cells (MRCs) in the gill epithelium shifted from a seawater type to a freshwater type following transfer to 0.1 ppt water in correlation with the increase in mRNA levels of arg II and odc in MRCs. In addition, the isolated opercular epithelium pretreated with spermidine had a lower active Cl- secretion rate and membrane conductance following symmetrical hypotonic exposure. Transcription and enzymatic activities of Arg II, Odc, and Pao were upregulated in the intestine and liver during hypoosmotic exposure, suggesting that polyamine levels are regulated in multiple tissues of the killifish. The putative roles of polyamines include inducing cell apoptosis by increasing caspase-3 activity, stimulating cell proliferation by increasing the levels of c-fos and c-myc mRNA levels, and inducing cell swelling via the modulation of Cl- secretion in the gills following hypoosmotic challenges. In summary, fish gill and intestine of killifish transferred to fresh water underwent dramatic physiological and morphological alterations, and had significantly altered polyamine metabolism. Highly cationic polyamines mediate early phase compensatory responses in the euryhaline killifish when faced with osmotic challenges. Although gill spermidine and spermine increased transiently in killifish with freshwater exposure, putrescine remained elevated over time, suggesting a possible role of this polyamine in acclimation of killifish to fresh water. The putative role of polyamines may be involved in gill remodeling by regulating cell proliferation and apoptosis

Glucocorticoids Inhibit Sodium Depletion-induced Salt Appetite in Rat

Glucocorticoids, produced in adrenal cortex, exert potent natriuretic and diuretic actions in the kidney. Recently, it has been found that glucocorticoids could upregulate the expression of natriuretic peptide receptor A (NPR-A), the primary receptor of atrial natriuretic peptide, in the hypothalamus of the rat. Consequently, systemic administration of glucocorticoid could block dehydration-induced water intake by activation hypothalamic NPR-A. We describe here glucocorticoids could inhibit sodium intake when administrated systemically in conscious, salt-depleted rats; an effect which was strong and long-lasting. The study provided further evidence for the actions of glucocorticoids on central nervous system, which together with their established renal actions coordinated to normalize extracellular fluid volume

Cycle-resistant credit systems: learning from Hong Kong’s experience

Hong Kong’s home mortgage market has remained among the world’s most stable. Supervisory authorities point to the 70 percent loan-to-value policy.Mortgage loans ; Housing - Prices ; Hong Kong

The possible members of the 51S05^1S_0 meson nonet

The strong decays of the $5^1S_0$ $q\bar{q}$ states are evaluated in the $^3P_0$ model with two types of space wave functions. Comparing the model expectations with the experimental data for the $\pi(2360)$, $\eta(2320)$, $X(2370)$, and $X(2500)$, we suggest that the $\pi(2360)$, $\eta(2320)$, and $X(2500)$ can be assigned as the members of the $5^1S_0$ meson nonet, while the $5^1S_0$ assignment for the $X(2370)$ is not favored by its width. The $5^1S_0$ kaon is predicted to have a mass of about 2418 MeV and a width of about 163 MeV or 225 MeV.Comment: 10 pages, 5 figures, version accepted by Eur. Phys. J.