An Observational Diagnostic for Distinguishing Between Clouds and Haze in Hot Exoplanet Atmospheres

The nature of aerosols in hot exoplanet atmospheres is one of the primary vexing questions facing the exoplanet field. The complex chemistry, multiple formation pathways, and lack of easily identifiable spectral features associated with aerosols make it especially challenging to constrain their key properties. We propose a transmission spectroscopy technique to identify the primary aerosol formation mechanism for the most highly irradiated hot Jupiters (HIHJs). The technique is based on the expectation that the two key types of aerosols -- photochemically generated hazes and equilibrium condensate clouds -- are expected to form and persist in different regions of a highly irradiated planet's atmosphere. Haze can only be produced on the permanent daysides of tidally-locked hot Jupiters, and will be carried downwind by atmospheric dynamics to the evening terminator (seen as the trailing limb during transit). Clouds can only form in cooler regions on the night side and morning terminator of HIHJs (seen as the leading limb during transit). Because opposite limbs are expected to be impacted by different types of aerosols, ingress and egress spectra, which primarily probe opposing sides of the planet, will reveal the dominant aerosol formation mechanism. We show that the benchmark HIHJ, WASP-121b, has a transmission spectrum consistent with partial aerosol coverage and that ingress-egress spectroscopy would constrain the location and formation mechanism of those aerosols. In general, using this diagnostic we find that observations with JWST and potentially with HST should be able to distinguish between clouds and haze for currently known HIHJs.Comment: 10 pages, 4 figures, accepted to ApJ Letter

Photon-assisted shot noise in graphene in the Terahertz range

When subjected to electromagnetic radiation, the fluctuation of the electronic current across a quantum conductor increases. This additional noise, called photon-assisted shot noise, arises from the generation and subsequent partition of electron-hole pairs in the conductor. The physics of photon-assisted shot noise has been thoroughly investigated at microwave frequencies up to 20 GHz, and its robustness suggests that it could be extended to the Terahertz (THz) range. Here, we present measurements of the quantum shot noise generated in a graphene nanoribbon subjected to a THz radiation. Our results show signatures of photon-assisted shot noise, further demonstrating that hallmark time-dependant quantum transport phenomena can be transposed to the THz range.Comment: includes supplemental materia

High prevalence of Sarcocystis calchasi in racing pigeon flocks in Germany

The apicomplexan parasite Sarcocystis calchasi (Coccidia: Eimeriorina: Sarcocystidae) is the causative agent of Pigeon Protozoal Encephalitis (PPE) and infects birds of the orders Columbiformes, Piciformes and Psittaciformes. Accipiter hawks (Aves: Accipitriformes) are the definitive hosts of this parasite. Infections of S. calchasi have been detected in Germany, the United States and Japan. However, the prevalence of the parasite in racing pigeon flocks has not yet been determined. Here, the first cross-sectional prevalence study to investigate S. calchasi in pigeon racing flocks was accomplished including 245 pigeon flocks across Germany. A total of 1,225 muscle biopsies, were taken between 2012 and 2016 and examined by semi-nested PCR for S. calchasi DNA targeting the ITS gene. Additionally, a questionnaire on construction of the aviary as well as management and health status of the flock was conducted. In 27.8% (95% C.I. = 22.3–33.8%) of the flocks, S. calchasi DNA was detected in at least one pigeon. Positive flocks were located in 15 out of 16 federal states. A significant increase of infected racing pigeons was seen in spring. Half-covered or open aviary constructions showed a trend of increase of the prevalence rate, while anti-coccidian treatment and acidified drinking water had no effects. The high prevalence and the geographical distribution of S. calchasi suggest a long-standing occurrence of the parasite in the German racing pigeon population. For pigeons presented with neurological signs or other symptoms possibly related to PPE, S. calchasi should be considered as a potential cause throughout Germany

Message handling system concepts and services in a land mobile satellite system

A network architecture containing the capabilities offered by the Message Handling System (MHS) to the PRODAT Land Mobile Satellite System (LMSS) is described taking into account the constraints of a preexisting satellite system which is going to become operational. The mapping between MHS services and PRODAT requirements is also reported and shows that the supplied performance can be significantly enhanced to both fixed and mobile users. The impact of the insertion of additional features on the system structure, especially on the centralized control unit, are also addressed

Nonlinear ac conductivity of one-dimensional Mott insulators

We discuss a semiclassical calculation of low energy charge transport in one-dimensional (1d) insulators with a focus on Mott insulators, whose charge degrees of freedom are gapped due to the combination of short range interactions and a periodic lattice potential. Combining RG and instanton methods, we calculate the nonlinear ac conductivity and interpret the result in terms of multi-photon absorption. We compare the result of the semiclassical calculation for interacting systems to a perturbative, fully quantum mechanical calculation of multi-photon absorption in a 1d band insulator and find good agreement when the number of simultaneously absorbed photons is large.Comment: Dedicated to Thomas Nattermann on the occasion of his 60th birthday. To appear in JSTAT. 5 pages, 2 figure

Sound production and mechanism in <i>Heniochus chrysostomus</i> (Chaetodontidae)

The diversity in calls and sonic mechanisms appears to be important in Chaetodontidae. Calls in Chaetodon multicinctus seem to include tail slap, jump, pelvic fin flick and dorsal–anal fin erection behaviors. Pulsatile sounds are associated with dorsal elevation of the head, anterior extension of the ventral pectoral girdle and dorsal elevation of the caudal skeleton in Forcipiger flavissiumus. In Hemitaurichthys polylepis, extrinsic swimbladder muscles could be involved in sounds originating from the swimbladder and correspond to the inward buckling of tissues situated dorsally in front of the swimbladder. These examples suggest that this mode of communication could be present in other members of the family. Sounds made by the pennant bannerfish (Heniochus chrysostomus) were recorded for the first time on coral reefs and when fish were hand held. In hand-held fishes, three types of calls were recorded: isolated pulses (51%), trains of four to 11 pulses (19%) and trains preceded by an isolated pulse (29%). Call frequencies were harmonic and had a fundamental frequency between 130 and 180 Hz. The fundamental frequency, sound amplitude and sound duration were not related to fish size. Data from morphology, sound analysis and electromyography recordings highlight that the calls are made by extrinsic sonic drumming muscles in association with the articulated bones of the ribcage. The pennant bannerfish system differs from other Chaetodontidae in terms of sound characteristics, associated body movements and, consequently, mechanism

Hearing capacities and otolith size in two ophidiiform species (<i>Ophidion rochei</i> and <i>Carapus acus</i>)

Numerous studies have highlighted the diversity of fish inner ear morphology. However, the function of the shape, size and orientation of the different structures remains poorly understood. The saccule (otolithic endorgan) is considered to be the principal hearing organ in fishes and it has been hypothesized that sagitta (saccular otolith) shape and size affect hearing capacities: large sagittae are thought to increase sensitivity. The sagittae of many ophidiids and carapids occupy a large volume inside the neurocranium. Hence they are a good structure with which to test the size hypothesis. The main aim of this study was to investigate hearing capacities and inner ear morphology in two ophidiiform species: Ophidion rochei and Carapus acus. We used a multidisciplinary approach that combines dissections, µCT-scan examinations and auditory evoked potential techniques. Carapus acus and O. rochei sagittae have similar maximal diameters; both species have larger otoliths than many non-ophidiiform species, especially compared with the intra-neurocranium volume. Both species are sensitive to sounds up to 2100 Hz. Relative to the skull, O. rochei has smaller sagittae than the carapid, but better hearing capacities from 300 to 900 Hz and similar sensitivities at 150 Hz and from 1200 to 2100 Hz. Results show that hearing capacities of a fish species cannot be predicted only based on sagitta size. Larger otoliths (in size relative to the skull) may have evolved mainly for performing vestibular functions in fishes, especially those species that need to execute precise and complex movements

An Intermediate in the evolution of superfast sonic muscles.

Background Intermediate forms in the evolution of new adaptations such as transitions from water to land and the evolution of flight are often poorly understood. Similarly, the evolution of superfast sonic muscles in fishes, often considered the fastest muscles in vertebrates, has been a mystery because slow bladder movement does not generate sound. Slow muscles that stretch the swimbladder and then produce sound during recoil have recently been discovered in ophidiiform fishes. Here we describe the disturbance call (produced when fish are held) and sonic mechanism in an unrelated perciform pearl perch (Glaucosomatidae) that represents an intermediate condition in the evolution of super-fast sonic muscles. Results The pearl perch disturbance call is a two-part sound produced by a fast sonic muscle that rapidly stretches the bladder and an antagonistic tendon-smooth muscle combination (part 1) causing the tendon and bladder to snap back (part 2) generating a higher-frequency and greater-amplitude pulse. The smooth muscle is confirmed by electron microscopy and protein analysis. To our knowledge smooth muscle attachment to a tendon is unknown in animals. Conclusion The pearl perch, an advanced perciform teleost unrelated to ophidiiform fishes, uses a slow type mechanism to produce the major portion of the sound pulse during recoil, but the swimbladder is stretched by a fast muscle. Similarities between the two unrelated lineages, suggest independent and convergent evolution of sonic muscles and indicate intermediate forms in the evolution of superfast muscles

The initial mass distribution of the M82 star cluster system

We explore whether we can constrain the shape of the INITIAL mass distribution of the star cluster population in M82's ~1 Gyr-old post-starburst region "B", in which the present-day cluster mass function (CMF) is closely approximated by a log-normal distribution. We conclude that the M82 B initial CMF must have had a mean mass very close to that of the "equilibrium" CMF of Vesperini (1998). Consequently, if the presently observed M82 B CMF has remained approximately constant since its formation, as predicted, then the INITIAL CMF must have been characterized by a mean mass that was only slightly larger than the present mean mass. From our detailed analysis of the expected evolution of CMFs, we conclude that our observations of the M82 B CMF are inconsistent with a scenario in which the 1 Gyr-old cluster population originated from an initial power-law mass distribution. Our conclusion is supported by arguments related to the initial density in M82 B, which would have been unphysically high if the present cluster population were the remains of an initial power-law distribution.Comment: 10 pages, 4 figures, accepted for publication in MNRA