Liquid—gas transition for hard spheres with attractive Yukawa tail interactions

We describe the liquid-gas transition in the hard sphere system with Yukawa tail interactions in the mean spherical approximation. The dependence of critical temperature and density on the range of the interaction is shown and the spinodal curve for a short-ranged potential and a long—ranged potential is presented. The compressibility, energy and virial pressures are presented for a long-ranged potential. Liquid phase pressures are calculated by integrating round the coexistence region, rather than through it.     

Raman spectrum and cross sections of n-C3F7I. Implications for a large-scale atomic iodine laser

The Raman spectrum of gaseous n-C₃F₇I has been recorded.Raman cross sections, depolarization ratios, and line widths were measured for the four strongest Raman-active modes. Using the measured values for the 280 cm^-1 mode, the stimulated-Raman gain for a large-scale iodine laser was calculated. The results indicate that losses due to stimulated-Raman scattering will be negligible for a fusion-driver iodine laser.     

Genome sequence and comparative analysis of the model rodent malaria parasite Plasmodium yoelii yoelii

Species of malaria parasite that infect rodents have long been used as models for malaria disease research. Here we report the whole-genome shotgun sequence of one species, Plasmodium yoelii yoelii, and comparative studies with the genome of the human malaria parasite Plasmodium falciparum clone 3D7. A synteny map of 2,212 P. y. yoelii contiguous DNA sequences (contigs) aligned to 14 P. falciparum chromosomes reveals marked conservation of gene synteny within the body of each chromosome. Of about 5,300 P. falciparum genes, more than 3,300 P. y. yoelii orthologues of predominantly metabolic function were identified. Over 800 copies of a variant antigen gene located in subtelomeric regions were found. This is the first genome sequence of a model eukaryotic parasite, and it provides insight into the use of such systems in the modelling of Plasmodium biology and disease.     

Surface interactions of molecular C60 and impact on Ni(100) and Co(0001) film growth: A scanning tunneling microscopy study

Here, the interactions of C₆₀ at the surface of pseudomorphic Ni/Cu(100) and Co/Ru(0001) thin films and its effect on film growth and morphology were determined using in-situ scanning tunneling microscopy (STM) and Auger electron spectroscopy (AES). The novel development of C₆₀-metallic based nanosystems, such as C₆₀ molecular junction transistors, hinges on our ability to understand the factors governing structural stability in these nanosystems and the nature of the bond interactions at the C₆₀–metal interface. In this study, C₆₀ deposited onto the Ni(100) film surface is observed to be fairly immobile and uniformly distributed across the Ni surface. On the Co(0001) film surface however, C₆₀ mobility is observed to be severely limited in some regions and highly mobile in others dependent upon Co film surface reconstruction, resulting in a non-uniform distribution of C₆₀ across the Co film surface. Despite the presence of C₆₀ on the Ni surface, there is no obvious influence of the C₆₀ on further Ni film growth. In contrast, during Co film growth, islands only nucleate and grow from step edges or locally around C₆₀ molecules. The strength of the Co–C₆₀ bond interaction appears stronger than the Co–Co bond on Co film terrace. Generally, the Ni and Co films both continue epitaxial film growth in the presence of molecular C₆₀. AES results indicate the C₆₀ molecules maintain their chemical integrity during growth.     

Relativistic jet activity from the tidal disruption of a star by a massive black hole

Supermassive black holes have powerful gravitational fields with strong gradients that can destroy stars that get too close, producing a bright flare in ultraviolet and X-ray spectral regions from stellar debris that forms an accretion disk around the black hole. The aftermath of this process may have been seen several times over the past two decades in the form of sparsely sampled, slowly fading emission from distant galaxies, but the onset of the stellar disruption event has not hitherto been observed. Here we report observations of a bright X-ray flare from the extragalactic transient Swift J164449.3+573451. This source increased in brightness in the X-ray band by a factor of at least 10,000 since 1990 and by a factor of at least 100 since early 2010. We conclude that we have captured the onset of relativistic jet activity from a supermassive black hole. A companion paper comes to similar conclusions on the basis of radio observations. This event is probably due to the tidal disruption of a star falling into a supermassive black hole, but the detailed behaviour differs from current theoretical models of such events.     

The unusual γ-ray burst GRB 101225A from a helium star/neutron star merger at redshift 0.33

Long γ-ray bursts (GRBs) are the most dramatic examples of massive stellar deaths, often associated with supernovae. They release ultra-relativistic jets, which produce non-thermal emission through synchrotron radiation as they interact with the surrounding medium. Here we report observations of the unusual GRB 101225A. Its γ-ray emission was exceptionally long-lived and was followed by a bright X-ray transient with a hot thermal component and an unusual optical counterpart. During the first 10 days, the optical emission evolved as an expanding, cooling black body, after which an additional component, consistent with a faint supernova, emerged. We estimate its redshift to be z = 0.33 by fitting the spectral-energy distribution and light curve of the optical emission with a GRB-supernova template. Deep optical observations may have revealed a faint, unresolved host galaxy. Our proposed progenitor is a merger of a helium star with a neutron star that underwent a common envelope phase, expelling its hydrogen envelope. The resulting explosion created a GRB-like jet which became thermalized by interacting with the dense, previously ejected material, thus creating the observed black body, until finally the emission from the supernova dominated. An alternative explanation is a minor body falling onto a neutron star in the Galaxy.     

Method for the determination of gamma-L-glutamyl-L-dihydroxyphenylalanine and its major metabolites L-dihydroxyphenylalanine, dopamine and 3,4-dihydroxyphenylacetic acid by high-performance liquid chromatography with electrochemical detection

A high-performance liquid chromatographic method for the analysis of gamma-L-glutamyl-L-dihydroxyphenylalanine (gludopa) and its major metabolites L-dihydroxyphenylalanine (L-DOPA), dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) is described. High sensitivity is achieved with a multi-cell coulometric detector utilising the specific electrochemical properties of gludopa (limit of detection 10 pg on-column). The retention time of gludopa was both pH-dependent and sensitive to negatively charged ion-pairing agents. An alumina-based solid-phase sample preparation technique with dihydroxybenzylamine as internal standard is described for plasma and urine (limit of detection 40 pg/ml) and an ultrafiltration technique is described for tissues (limit of detection 1-10 ng/g). After treatment with 50 mg/kg gludopa, in excess of twenty separate catecholic metabolic peaks can be detected in rat urine, whereas in humans after 9 mg/kg the only catechols detected were L-DOPA, dopamine and DOPAC.     

Sounds, source levels, and associated behavior of humpback whales, southeast Alaska

Humpback whales in Southeast Alaskan waters produced five categories of sounds: moans, grunts, pulse trains, blowhole-associated sounds, and surface impacts. Frequencies (Hz) of moans and grunts were 20-1900. Major energy in low-frequency pulse trains was in a band of 25-80 Hz with pulse duration of 300-400 ms. Blowhole-associated sounds, recorded as transiting whales encountered one another, were of two types: shrieks, 555-2000 Hz, and trumpetlike horn blasts with fundamental at 414 Hz (median). Pulses and spread spectrum noise were associated with gas bubble formation and explosive bursts, respectively, in connection with spiral feeding maneuvers. Surface impacts resulted from fluke or flipper slaps in sequences of 3-21 sounds. Source levels ranged from 162 (low-frequency pulse trains) to 192 dB (surface impacts), re: 1 microPa, 1 m. Songs, commonly heard on winter breeding grounds, were absent from our recordings. Feeding and perhaps certain other whale activities can be monitored based on sound production.     

The structure of liquid deuterium bromide by slow-neutron scattering

Neutron diffraction measurements at 0·7 Å are reported for coexisting liquid deuterium bromide at -40°C. The results show that the deuterium bromide molecule in the liquid is little distorted as compared with the free molecule. The presence of a peak in the intermolecular pair distribution function at 3·1 Å is thought to be evidence of the formation of weak, rather long, intermolecular hydrogen bonds. As expected, both these effects are much weaker than for deuterium chloride reported in an earlier paper [2] and liquid deuterium bromide is therefore a simpler polar liquid.