bluuebunny/crossref_metadata_2025 huggingface dataset:
The nucleus of IC 342 as a potential twin of the Galactic center
Authors: Meier David S.
Published: May 2014

The Galactic center (GC), being the closest nucleus, holds a position of privilege in the study of galaxy centers, but because it is edge-on and hidden behind 30 magnitudes of visual extinction it is often difficult to understand the overall structure of the region. Nearby galactic nuclei potentially provide a guide to understanding the large-scale structure of the GC. High resolution maps of molecular line emission along with radio and optical continuum towards the nucleus of the nearby, face-on spiral IC 342 are discussed. Attention is focused on a comparison of the large-scale morphology, gas chemistry, and star formation between the two nuclei. The case is made that IC 342 is one of the best extragalactic templates for the GC. Both have a star formation rate within a factor of two of each other and an ISM morphology characterized by a R 300 pc central molecular zone formed from a pair of arms laced with a collection of dense star forming molecular clouds. IC 342 also exhibits a nuclear cluster and associated circumnuclear disk. Whether the nuclear morphology and chemistry in IC 342 is an extension of the disk bar, a separate nuclear bar, or results from radiative/mechanical feedback remains unsettled.
The warm ISM in the Sgr A region: mid-J CO, atomic carbon, ionized atomic carbon, and ionized nitrogen line observations with the Herschel/HIFI and NANTEN2/SMART Telescopes
Authors: García Pablo , Simon Robert , Stutzki Jürgen , Requena-Torres Miguel , Güsten Rolf , Fukui Yasuo , Yamamoto Hiroaki , Bertoldi Frank , Burton Michael , Bronfman Leonardo , Ogawa Hideo
Published: May 2014

We present Herschel/HIFI sub-mm atomic carbon ([Ci] 3P1 – 3P0 and [Ci] 3P2 – 3P1), ionized carbon ([Cii] 2P3/2 – 2P1/2), and ionized nitrogen ([Nii] 3P1 – 3P0) line observations obtained in the frame of the Herschel Guaranteed Time HEXGAL (Herschel EXtraGALactic) key program (P. I. Rolf Güsten, MPIfR), and NANTEN2/SMART carbon monoxide (CO(J = 4 – 3)) observations of the warm gas around the Sgr A region. The spectrally resolved emission from all lines, and the corresponding line intensity ratios, show a very complex morphology. The determination of spatial and spectral (anti)correlation with known sources in the Sgr A region such as the Arched Filaments, NTF filaments, the Sickle, Quintuplet cluster, CND clouds, is ongoing work.
Study of the molecular gas in the central parsec of the Galaxy through regularized 3D spectroscopy
Authors: Ciurlo A. , Paumard T. , Rouan D. , Clénet Y.
Published: May 2014

The cool gas in the central parsec of the Galaxy is organized in the surrounding circumnuclear disk, made of neutral gas, and the internal minispiral, composed of dust and ionized gas. In order to study the transition between them we have investigated the presence of H2 neutral gas in this area, through NIR spectro-imaging data observed with SPIFFI. To preserve the spatial resolution we implemented a new method consisting of a regularized 3D fit. We concentrated on the supposedly fully ionized central cavity and the very inner edge of the CND. H2 is detected everywhere: at the boundary of the CND and in the central cavity, where it seems to split in two components, one in the background of the minispiral and one inside the Northern arm.
Sgr A West in the light of molecules: cold and dense gas east of the circumnuclear disk
Authors: Moser Lydia , Eckart A. , Borkar A. , García-Marin M. , Kunneriath D. , Jalali B. , Sabha N. , Shahzamanian B. , Valencia-S. M. , Zamaninasab M. , Bronfman L. , Finger R.
Published: May 2014

We present the very first detection of N2H+J = (1 – 0) and CH3OH(2k−1k) line emission on 5″ scales in the circumnuclear disk (CND) around Sgr A*. The emission matches the position and shape of the dark clouds in the near-infrared. Our findings suggest that these molecular clouds in the eastern CND are significantly colder and denser than the rest of the CND, and partially shocked. The research on these dark clouds will contribute to understanding the processes of star formation close to a supermassive black hole.
Regularized OSIRIS 3D spectroscopy at the circumnuclear disk ionization front
Authors: Paumard Thibaut , Morris Mark R. , Do Tuan , Ghez Andrea
Published: May 2014

The Galactic central black hole and the central cluster of young stars are surrounded by a clumpy gas disk (the circumnuclear disk, CND) that rotates about them at a distance of ≃ 1 pc. The gas in this warm, turbulent, magnetized disk is ultimately likely to migrate into the central cavity and fuel future star formation and black hole accretion. We have observed two fields of approximately 20″ × 20″ in the CND at NIR wavelengths with the OSIRIS integral-field spectrometer at Keck Observatory. These two fields are located at the interface between the neutral and the ionized regions. Our data cover two H2 lines as well as the Brγ line of the Hi spectrum. The signal-to-noise ratio per spatial pixel of each line varies considerably across the field and becomes quite low in some regions. In order to avoid degrading the spatial resolution, we have developed a novel three-dimensional method to analyze the data in terms of regularized parameter maps. The method proves very efficient in retrieving all the information contained in the spectral line emission while not degrading the spatial resolution. We present this new method to analyze 3D spectroscopic data and describe our preliminary results on the structure of the ionized-neutral interface.
Interferometric 3mm spectral line and continuum survey of the central molecular zone
Authors: Pound Marc W. , Yusef-Zadeh Farhad
Published: May 2014

Because of its large angular extent, the central molecular zone (CMZ) has to date only been mapped in the mm with single dish telescopes, with resolution about 30″ (1.4 pc). We present the first interferometric maps of a 90 × 50 pc region of the CMZ, with spatial resolution of ∼10″ (0.4 pc). We mapped ∼0.25 square degrees of the CMZ with CARMA in 3mm continuum and the spectral lines SiO J = (2 − 1), HCO+J = (1 − 0), HCN J = (1 − 0), N2H+J = (1 − 0), and CS J = (2 − 1), covering roughly VLSR = −200 to 200 km s−1 with spectral resolution ΔV ∼ 2.5 km s−1. To recover the large scale structure resolved out by the interferometer, the continuum-subtracted spectral line images were combined with the Mopra 22-m telescope survey.
SOFIA/HAWC+: Mapping the Galactic center magnetic field
Authors: Werner Michael W. , Dowell C. Darren , Chuss D. T. , Morris M. R. , Novak G. ,   for the HAWC+ team
Published: May 2014

Polarimetry of the far infrared emission from magnetically-aligned interstellar grains is one of the best ways of studying the magnetic field at the Galactic center. We describe the HAWC+ instrument, under development for flight on SOFIA starting in 2015, which will provide a major advance in capability for these critically important measurements.
Radio continuum and radio recombination line observations of the Galactic center lobe
Authors: Nagoshi Halca , Fujisawa Kenta , Kubose Yuzo
Published: May 2014

Radio continuum (cont) and radio recombination line (RRL) observations with the Yamaguchi 32-m radio telescope toward the lower part of the Galactic center lobe (GCL) in the Galactic center region are presented. While two ridges of the GCL were seen in both continuum and RRL images, the spatial coverage of the ridges of the continuum and RRL is not coincident. We distinguish the continuum emission of the GCL into thermal and non-thermal emission by assuming an electron temperature of the ionized gas of 4370 K, estimated based on the line width (14.1 km s−1). The thermal emission was found to be located inside and surrounded by the non-thermal emission.
Conversion of gas into stars in the Galactic center
Authors: Longmore S. N.
Published: May 2014

The star formation rate in the central 500 pc of the Milky Way is lower by a factor of > 10 than expected for the substantial amount of dense gas it contains, which challenges current star formation theories. I discuss which physical mechanisms could be causing this observation and put forward a self-consistent cycle of star formation in the Galactic center, in which the plausible star formation inhibitors are combined. Their ubiquity suggests that the perception of a lowered central SFR should be a common phenomenon in other galaxies with direct implications for galactic star formation and also potentially supermassive black hole growth. I then describe a scenario to explain the presence of super star clusters in the Galactic center environment, in which their formation is triggered by gas streams passing close to the minimum of the global Galactic gravitational potential at the location of the central supermassive black hole, Sgr A*. If this triggering mechanism can be verified, we can use the known time interval since closest approach to Sgr A* to study the physics of stellar mass assembly in an extreme environment as a function of absolute time. I outline the first results from detailed numerical simulations testing this scenario. Finally, I describe a study showing that in terms of the baryonic composition, kinematics, and densities, the gas in the Galactic center is indistinguishable from high-redshift clouds and galaxies. As such, the Galactic center clouds may be used as a template to understand the evolution (and possibly the life cycle) of high-redshift clouds and galaxies.
Young stellar objects close to Sgr A*
Authors: Jalali B. , Pelupessy F. I. , Eckart A. , Zwart S. Portegies , Sabha N. , Borkar A. , Moultaka J. , Mužić K. , Moser L.
Published: May 2014

We aim at modeling small groups of young stars such as IRS 13N, 0.1 pc away from Sgr A*, which is suggested to contain a few embedded massive young stellar objects. We perform hydrodynamical simulations to follow the evolution of molecular clumps orbiting around a 4 × 106 M⊙ black hole, to constrain the formation and the physical conditions of such groups.

We find that the strong compression due to the black hole along the orbital radius vector of clumps evolving on highly eccentric orbits causes the clumps densities to increase to higher than the tidal density of Sgr A* and required for star formation. This suggests that the tidal compression from the black hole could support star formation.

Additionally, we speculate that the infrared excess source G2/DSO approaching Sgr A* on a highly eccentric orbit could be associated with a dust enshrouded star that may have been formed recently through the mechanism supported by our models.
Satellite infall and mass deposition on the Galactic center
Authors: Gallego S. C. , Cuadra J.
Published: May 2014

We modeled numerically the infall of a small satellite galaxy on to the inner 200 parsec of our Galaxy, to test whether such an event perturbs gas orbiting in the central molecular zone (CMZ), as recently proposed by Lang et al. (2013). This process could have driven a large gas inflow around 10 Myr ago, explaining the past high accretion rate onto the supermassive black hole, and the presence of young stars in the inner parsecs of the Galaxy. Our simulations show a very small inflow of gas, not sufficient to produce the aforementioned effects.
Galactic dynamics feeding the Galactic center
Authors: Renaud Florent , Emsellem Eric , Bournaud Frédéric
Published: May 2014

We present the hierarchical structure of the gas and its rapid evolution in the central region of a simulation of the entire Milky Way, run at subparsec resolution. We emphasize the coupling between the kpc-scale dynamics, the molecular ring and the central 5 pc disk feeding the supermassive black hole.
Young stellar disks formed by the collision of a molecular cloud with a circumnuclear disk at the Galactic center
Authors: Alig C. , Schartmann M. , Burkert A. , Dolag K.
Published: May 2014

We suggest a new formation mechanism for the inclined, sub-parsec scale and counterrotating stellar disks observed around the central black hole in the Milky Way Galactic center. The simulation of a single molecular cloud crashing into a circumnuclear ring of gas leads to the inflow of multiple streams of gas towards the central parsec region. The time delayed arrival of those streams forms multiple, sub-parsec scale accretion disks, with angular momentum depending on the ratio of cloud and circumnuclear ring material. These accretion disks could then be the progenitors which fragmented into the observed stellar disks. A similar event might have also led to the creation of the so-called minispiral in the Galactic center.
Cloud-cloud collision in the Sgr B2 molecular cloud complex
Authors: Tsuboi Masato , Miyazaki Atsushi , Handa Toshihiro
Published: May 2014

We present results from a high-resolution wide-field imaging observation of the central molecular zone (CMZ) in H13CO+J = (1 − 0) and SiO v=0, J = (2−1) emission lines by using the Nobeyama 45-m telescope in order to depict the high-density molecular gas mass distribution and explore molecular gas affected by interstellar shocks. We found a candidate for ongoing cloud-cloud collision in the Sgr B2 complex. This is identified as a hollow paraboloid-like structure in the l−b−v data cube of both emission lines. The central part of the feature is denser and warmer than the outer envelope and contains a vast amount of shocked molecular gas. These properties are consistent with those expected from simulations of cloud-cloud collisions in the CMZ.
Young stars in the Galactic center
Authors: Lu Jessica R. , Ghez Andrea M. , Morris Mark R. , Clarkson Will , Stolte Andrea , Do Tuan , Yelda Sylvana , Anderson Jay
Published: May 2014

The central parsec of our Galaxy hosts not only a supermassive black hole, but also a large population of young stars (age <6 Myr) whose presence is puzzling given how inhospitable the region is for star formation. The strong tidal forces require gas densities many orders of magnitude higher than is found in typical molecular clouds. Kinematic observations of this young nuclear cluster show complex structures, including a well-defined inner disk, but also a substantial off-disk population. Spectroscopic and photometric measurements indicate the initial mass function (IMF) differs significantly from the canonical IMF found in the solar neighborhood. These observations have led to a number of proposed star formation scenarios, such as an infalling massive star cluster, a single infalling molecular cloud, or cloud-cloud collisions. I will review recent works on the young stars in the central parsec and discuss connections with young nuclear star clusters in other galaxies, such as M31, and with star formation in the larger central molecular zone.
The Milky Way nuclear star cluster beyond 1 pc
Authors: Feldmeier A. , Neumayer N. , Seth A. , de Zeeuw P. T. , Schödel R. , Lützgendorf N. , Kissler-Patig M. , Nishiyama S. , Walcher C. J.
Published: May 2014

Within the central 10 pc of our Galaxy lies a dense cluster of stars, the nuclear star cluster, forming a distinct component of our Galaxy. Nuclear star clusters are common objects and are detected in ∼75% of nearby galaxies. It is, however, not fully understood how nuclear clusters form. Because the Milky Way nuclear star cluster is at a distance of only 8 kpc, we can spatially resolve its stellar populations and kinematics much better than in external galaxies. This makes the Milky Way nuclear star cluster a reference object for understanding the structure and assembly history of all nuclear star clusters.

We have obtained an unparalleled data set using the near-infrared long-slit spectrograph ISAAC (VLT) in a novel drift-scan technique to construct an integral-field spectroscopic map of the central ∼10 × 8 pc of our Galaxy. To complement our data set we also observed fields out to a distance of ∼19 pc along the Galactic plane to disentangle the influence of the nuclear stellar disk.

From this data set we extract a stellar kinematic map using the CO bandheads and an emission line kinematic map using H2 emission lines. Using the stellar kinematics, we set up a kinematic model for the Milky Way nuclear star cluster to derive its mass and constrain the central Galactic potential. Because the black hole mass in the Milky Way is precisely known, this kinematic data set will also serve as a benchmark for testing black hole mass modeling techniques used in external galaxies.
Unveiling the massive stars in the Galactic center
Authors: Dong H. , Mauerhan J. , Morris M. R. , Wang Q. D. , Cotera A.
Published: May 2014

We present our recent efforts to unveil and understand the origin of massive stars outside the three massive star clusters in the Galactic center. From our Hubble/NICMOS survey of the Galactic center, we have identified 180 Paschen-α emitting sources, most of which should be evolved massive stars with strong optically thin stellar winds. Recently, we obtained Gemini GNIRS/NIFS H- and K-band spectra of eight massive stars near the Arches cluster. From their radial velocities, ages and masses, we suggest that in our sample, two stars are previous members of the Arches cluster, while other two stars embedded in the H1/H2 Hii regions formed in-situ.
New orbital analysis of stars at the Galactic center using speckle holography and orbital priors
Authors: Boehle Anna , Schödel Rainer , Meyer Leo , Ghez Andrea M.
Published: May 2014

We present initial results of a study that has more than doubled the time baseline for astrometric measurements of faint stars orbiting the supermassive black hole (SMBH) at the Galactic center. The advent of adaptive optics has enabled stars as faint as K = 19 mag to be tracked at 50 mas resolution for the last decade. While similar resolution images exist from the prior decade, they were obtained from speckle imaging data analyzed with the technique of shift-and-add, which limited detections to stars brighter than K = 16 mag. By improving the speckle data analysis technique with speckle holography and using prior orbital knowledge, we are now able to track stars as faint as ∼18 mag at 50 mas resolution through the early Keck speckle data sets (1995-2005). This methodology has already led to the detection of two short-period stars never previously seen in speckle images, such that our data now spans their full orbits. We can now better constrain the orbital parameters of all stars in the intriguing “S-star cluster,” which will ultimately give us insight into the origin of these stars and be used to probe the curvature of space-time in the unexplored regime near a SMBH.
Observations of NIR polarized light from Sagittarius A*
Authors: Shahzamanian B. , Eckart A. , Zamaninasab M. , Witzel G. , Sabha N.
Published: May 2014

We present a brief overview of results obtained from near-infrared polarized observations of Sgr A*, which is associated with the supermassive black hole at the center of the Milky Way. The observations have been carried out using the NACO adaptive optics instrument at the VLT UT4 in the infrared Ks-band from 2004 to 2012. Several polarized flares have been observed in this time interval which allow us to determine the statistical properties of NIR linearly polarized light from Sgr A*. Linear polarization at 2.2 μm and its variations can help us to constrain the physical conditions of the accretion process around this supermassive black hole.
Radio emission from the bow shock of G2
Authors: Crumley P. , Kumar P.
Published: May 2014

The radio flux from the synchrotron emission of electrons accelerated in the forward bow shock of G2 is expected to have peaked when the forward shock passes close to the pericenter from the Galactic center, around autumn of 2013. This radio flux is model dependent. We find that if G2 were to be a momentum-supported bow shock of a faint star with a strong wind, the radio synchrotron flux from the forward-shock heated ISM is well below the quiescent radio flux of Sgr A*. By contrast, if G2 is a diffuse cloud, the radio flux is predicted to be much larger than the quiescent radio flux and therefore should have already been detected or will be detected shortly. No such radiation has been observed to date. Radio measurements can reveal the nature of G2 well before G2 completes its periapsis passage.
The Galactic center X-ray transients AX J1745.6–2901 and GRS 1741–2853
Authors: Degenaar N. , Wijnands R. , Reynolds M. T. , Miller J. M. , Kennea J. , Gehrels N.
Published: May 2014

AX J1745.6–2901 and GRS 1741–2853 are two transient neutron star low-mass X-ray binaries that are located within ≃ 10′ from the Galactic center. Multi-year monitoring observations with the Swift/XRT has exposed several accretion outbursts from these objects. We report on their updated X-ray light curves and renewed activity that occurred in 2010–2013.
3D moving mesh simulations of Galactic center cloud G2
Authors: Fragile P. C. , Anninos P. , Murray S. D.
Published: May 2014

Using three-dimensional, moving-mesh simulations, we investigate the future evolution of the recently discovered gas cloud G2 traveling through the galactic center. From our simulations we expect an average feeding rate onto Sgr A* in the range of (5−19) × 10−8M⊙ yr−1 beginning in 2014. This accretion varies by less than a factor of three on timescales ∼ 1 month, and shows no more than a factor of 10 difference between the maximum and minimum observed rates within any given model. These rates are comparable to the current estimated accretion rate in the immediate vicinity of Sgr A*, although they represent only a small (< 10%) increase over the current expected feeding rate at the effective inner boundary of our simulations (racc = 750 RS ∼ 1015 cm). We also explore multiple possible equations of state to describe the gas. In examining the Br-γ light curves produced from our simulations, we find that all of our isothermal models predict significant (factor of 10) enhancements in the luminosity of G2 as it approaches pericenter, in conflict with observations. Models that instead allow the cloud to heat as it is compressed do better at matching observations.
Multiple accretion events as a trigger for Sagittarius A* activity
Authors: Kunneriath D. , Czerny B. , Karas V. , Das T. K.
Published: May 2014

The Galactic center supermassive black hole is surrounded by orbiting clouds of gas. These clumps of gas may collide with each other, losing angular momentum and plunging towards the center. Observations of X-ray reflection from molecular clouds surrounding the Galactic center show evidence for enhanced activity of Sagittarius A* during the past few hundred years. These observations enable us to place constraints on the nature of past accretion events responsible for this enhanced activity. We model the source intrinsic luminosity of Sgr A* using multiple accretion events occurring at various moments in time, characterized by a range of angular momentum We also applied our scheme to the case of G2 cloud in the Galactic center.
Hydrodynamical simulations of G2 interpreted as a diffuse gas cloud
Authors: Schartmann M. , Burkert A. , Ballone A. , Alig C. , Gillessen S. , Genzel R. , Eisenhauer F. , Fritz T.
Published: May 2014

Recently the gas and dust cloud “G2” was discovered on a highly eccentric orbit around the massive black hole in the Galactic center. The orbit will bring the cloud as close as 2400 Schwarzschild radii to Sgr A* beginning of 2014. With the help of hydrodynamical simulations using the PLUTO code, we investigate possible origins and the fate of the cloud in the coming years. In this proceedings article, we concentrate on a scenario where G2 is interpreted as a diffuse gas cloud and show its detailed evolution in the observable position-velocity diagrams. We further elaborate on the problem of the tail emission which might or might not be related to the G2 cloud.
Feeding and feedback in nearby AGN – comparison with the Milky Way center
Authors: Storchi-Bergmann T.
Published: May 2014

I discuss feeding and feedback processes observed in the inner few hundred parsecs of nearby active galaxies using integral field spectroscopy at spatial resolutions of a few to tens of parsecs. Signatures of feedback include outflows from the nucleus with velocities ranging from 200 to 1000 km s−1, with mass outflow rates between 0.5 and a few M⊙ yr−1. Signatures of feeding include the observation of gas inflows along nuclear spirals and filaments, with velocities ranging from 50 to 100 km s−1 and mass flow rates from 0.1 to ∼1 M⊙ yr−1. These rates are 2–3 orders of magnitude larger than the mass accretion rate to the supermassive black hole (SMBH). These inflows can thus lead, during less than one activity cycle, to the accumulation of enough gas in the inner few hundred parsecs, to trigger the formation of new stars, leading to the growth of the galaxy bulge. Young to intermediate age stars have indeed been found in circumnuclear rings around a number of Active Galactic Nuclei (AGN). In particular, one of these rings, with radius of ≈ 100 pc is observed in the Seyfert 2 galaxy NGC 1068, and is associated to an off-centered molecular ring, very similar to that observed in the Milky Way (MW). On the basis of an evolutionary scenario in which gas falling into the nuclear region triggers star formation followed by the triggering of nuclear activity, we speculate that, in the case of the MW, molecular gas has already accumulated within the inner ≈ 100 pc to trigger the formation of new stars, as supported by the presence of blue stars close to the galactic center. A possible increase in the star-formation rate in the nuclear region will then be followed, probably tens of millions of years later, by the triggering of nuclear activity in Sgr A*.
Daily monitor of Sagittarius A* at 22 GHz with the Japanese VLBI Network
Authors: Tsuboi M. , Asaki Y. , Yonekura Y. , Miyamoto Y. , Kaneko H. , Seta M. , Nakai N. , Kameya O. , Miyoshi M. , Takaba H. , Wakamatsu K. , Fukuzaki Y. , Morimitsu T. , Uehara K. , Sekido M. , Oka T. , Takekawa S. , Omodaka T. , Handa T. , Takumi A.
Published: May 2014

We have been monitoring the flux density of Sagittarius A* (Sgr A*) at 22 GHz since DOY=42 (11 Feb. 2013) with a sub-array of the Japanese VLBI Network in order to search the increase of 22-GHz emission from Sgr A* induced by the interaction of the G2 cloud with the accretion disk. The flux densities observed until DOY=322 (18 Nov. 2013) are consistent with the previously observed values before the approaching of the cloud. We have detected no large flare during this period.
Sturm und Drang: The turbulent, magnetic tempest in the Galactic center
Authors: Lacki Brian C.
Published: May 2014

The Galactic center central molecular zone (GCCMZ) bears similarities with extragalactic starburst regions, including a high supernova (SN) rate density. As in other starbursts like M82, the frequent SNe can heat the ISM until it is filled with a hot (∼ 4 × 107 K) superwind. Furthermore, the random forcing from SNe stirs up the wind, powering Mach 1 turbulence. I argue that a turbulent dynamo explains the strong magnetic fields in starbursts, and I predict an average B ∼70 μG in the GCCMZ. I demonstrate how the SN driving of the ISM leads to equipartition between various pressure components in the ISM. The SN-heated wind escapes the center, but I show that it may be stopped in the Galactic halo. I propose that the Fermi bubbles are the wind's termination shock.
Detecting gravitational waves from the Galactic center with pulsar timing
Authors: Ray Alak , Kocsis Bence , Zwart Simon Portegies
Published: May 2014

Black holes orbiting the supermassive black hole (SMBH) Sgr A* in the Galactic center (GC) of the Milky Way generate gravitational waves (GW). The resulting spectrum, due to stars and black holes (BHs), is continuous below 40 nHz while individual BHs within about 200 AU of the central SMBH stick out in the spectrum at higher frequencies. The GWs can be detected by timing radio pulsars within a few parsecs of this region. Future observations with the Square Kilometer Array of such pulsars with sufficient timing accuracy may be sensitive to signals from intermediate mass BHs (IMBH) in a 3 year observation baseline. The recent detection of radio pulsations from the magnetar SGR J1745–29 very near the GC opens up the possibilities of detecting millisecond pulsars (which can be used as probes of the GWs) through lines of sight with only moderate pulse and angular broadening due to scattering.
Tidal disruption events in galactic centers
Authors: Parajuli Resha , Hartmann Dieter H.
Published: May 2014

Supermassive black holes (106–109 M⊙) are now known to be present at the centers of most galaxies, but they are also found to have a close correlation with the host galaxy they live in. The masses of the supermasssive black holes (SMBHs) have been rigorously calculated using stellar dynamics (e.g., Gillessen et al. 2009) for the Milky Way, gas dynamics (e.g., Davis et al. 2013) for NGC 4526, water maser emissions, reverberation mapping, etc. In comparison, the mass of the SMBH seems to be tightly correlated with the galactic bulge it resides in. The tight correlation between the mass of the BH and the velocity dispersion of the stars in the bulge, known as the M-σ relation, (Ferrarese & Merritt, 2000; Tremaine et al. 2002), and the 2:1000 mass of BH - mass of bulge ratio suggests some sort of co-evolution process. A feedback driven coevolution process would suggest that the BH directly controls galaxy properties via energy and momentum feedback (Kormendy & Ho, 2013). However, since correlation does not necessarily imply causation, the evolution may be a non-causal process that occurs in tandem, where the BH and bulge grow independently. In such a process, star formation in the bulge and growth of SMBH occur in separate periods and are self regulating (Cen, 2012).
First results from the NuSTAR “mini-survey” of the Galactic center region
Authors: Hailey Charles J. ,   the NuSTAR Team
Published: May 2014

One of the major science objectives of the Nuclear Spectroscopic Telescope Array (NuSTAR) observatory is to perform the first sub-arcminute, hard X-ray survey of several square degrees of the Galactic plane, centered on a region near the Galactic center. As a prelude to the full survey, which began in July 2013, NuSTAR conducted a ∼500 ks, 0.3 × 0.4° “mini-survey” focused on Sgr A* and its environs. We present analysis of several candidate pulsar wind nebulae and filaments, which are revealed to be intense sources of X-ray emission at >10 keV.
The origin of the Galactic center diffuse X-ray emission investigated by near-infrared imaging and polarimetric observations
Authors: Nishiyama Shogo , Yasui Kazuki , Nagata Tetsuya , Yoshikawa Tatsuhito , Uchiyama Hideki , Tamura Motohide
Published: May 2014

The origin of the Galactic center diffuse X-ray emission (GCDX) is still under intense investigation. We have found a clear excess in a longitudinal GCDX profile over a stellar number density profile in the nuclear bulge region, suggesting a significant contribution of diffuse, interstellar hot plasma to the GCDX. We have estimated that contributions of an old stellar population to the GCDX are ∼50% and ∼20% in the nuclear stellar disk and nuclear star cluster, respectively. Our near-infrared polarimetric observations show that the GCDX region is permeated by a large scale, toroidal magnetic field. Together with observed magnetic field strengths in nearly energy equipartition, the interstellar hot plasma could be confined by the toroidal magnetic field.
Mixed lineage kinases activate MEK independently of RAF to mediate resistance to RAF inhibitors
Authors: Marusiak Anna A. , Edwards Zoe C. , Hugo Willy , Trotter Eleanor W. , Girotti Maria R. , Stephenson Natalie L. , Kong Xiangju , Gartside Michael G. , Fawdar Shameem , Hudson Andrew , Breitwieser Wolfgang , Hayward Nicholas K. , Marais Richard , Lo Roger S. , Brognard John
Published: May 2014

RAF inhibitor therapy yields significant reductions in tumour burden in the majority of V600E-positive melanoma patients; however, resistance occurs within 2–18 months. Here we demonstrate that the mixed lineage kinases (MLK1–4) are MEK kinases that reactivate the MEK/ERK pathway in the presence of RAF inhibitors. Expression of MLK1–4 mediates resistance to RAF inhibitors and promotes survival in V600E-positive melanoma cell lines. Furthermore, we observe upregulation of the MLKs in 9 of 21 melanoma patients with acquired drug resistance. Consistent with this observation, MLKs promote resistance to RAF inhibitors in mouse models and contribute to acquired resistance in a cell line model. Lastly, we observe that a majority of MLK1 mutations identified in patients are gain-of-function mutations. In summary, our data demonstrate a role for MLKs as direct activators of the MEK/ERK pathway with implications for melanomagenesis and resistance to RAF inhibitors.
Relativistic Quantum Metrology: Exploiting relativity to improve quantum measurement technologies
Authors: Ahmadi Mehdi , Bruschi David Edward , Sabín Carlos , Adesso Gerardo , Fuentes Ivette
Published: May 2014

We present a framework for relativistic quantum metrology that is useful for both Earth-based and space-based technologies. Quantum metrology has been so far successfully applied to design precision instruments such as clocks and sensors which outperform classical devices by exploiting quantum properties. There are advanced plans to implement these and other quantum technologies in space, for instance Space-QUEST and Space Optical Clock projects intend to implement quantum communications and quantum clocks at regimes where relativity starts to kick in. However, typical setups do not take into account the effects of relativity on quantum properties. To include and exploit these effects, we introduce techniques for the application of metrology to quantum field theory. Quantum field theory properly incorporates quantum theory and relativity, in particular, at regimes where space-based experiments take place. This framework allows for high precision estimation of parameters that appear in quantum field theory including proper times and accelerations. Indeed, the techniques can be applied to develop a novel generation of relativistic quantum technologies for gravimeters, clocks and sensors. As an example, we present a high precision device which in principle improves the state-of-the-art in quantum accelerometers by exploiting relativistic effects.
Developments toward a low-cost approach for long-term, unattended vapor intrusion monitoring
Authors: Patel Sanjay V. , Tolley William K.
Published: May 2014

We describe progress towards development of a low-cost gas chromatograph for unattended vapor intrusion monitoring.
Targeted highly sensitive detection/eradication of multi-drug resistant Salmonella DT104 through gold nanoparticle–SWCNT bioconjugated nanohybrids
Authors: Lin Yunfeng , Hamme II Ashton T.
Published: May 2014

Monoclonal antibody-conjugated sphere-shaped gold nanoparticles were combined with single-walled carbon nanotubes (SWCNTs) to create a nanohybrid system to selectively detect and eradicate multiple drug resistant Salmonella (MDRS) typhimurium DT104 bacteria.
Porous molecular networks formed by the self-assembly of positively-charged trigonal building blocks at the liquid/solid interfaces
Authors: Tahara Kazukuni , Abraham Maria L. , Igawa Kosuke , Katayama Keisuke , Oppel Iris M. , Tobe Yoshito
Published: May 2014

Tris-(2-hydroxybenzylidene)triaminoguanidinium salts having six alkyl chains with proper spacing served as new molecular building blocks for the formation of porous honeycomb networks by van der Waals interaction between interdigitated alkyl chains at the liquid/graphite interfaces.
Molecular self-assembly of arene-Ru based interlocked catenane metalla-cages
Authors: Mishra Anurag , Dubey Abhishek , Min Jin Wook , Kim Hyunuk , Stang Peter J. , Chi Ki-Whan
Published: May 2014

Two interlocked and two simple trigonal prisms are formed through the coordination self-assembly of arene-Ru acceptors with a new tridentate donor.
Diastereomeric control of enantioselectivity: evidence for metal cluster catalysis
Authors: Abdel-Magied Ahmed F. , Singh Amrendra K. , Haukka Matti , Richmond Michael G. , Nordlander Ebbe
Published: May 2014

Enantioselective hydrogenation of tiglic acid effected by diastereomers of the general formula [(μ-H)2Ru3(μ3-S)(CO)7(μ-P–P*)] (P–P* = chiral Walphos diphosphine ligand) strongly supports catalysis by intact Ru3 clusters.
Synthesis of soft colloids with well-controlled softness
Authors: Luo Fuhua , Cheng Zhifeng , Wang Man , Chen Gaojian , Zhang Zexin
Published: May 2014

Synthesis of soft colloids with well-controlled softness by emulsion polymerisation of silicon oil droplets, using different amounts of an initiator.
Convenient detection of HPV virus in a clinical sample using concurrent rolling circle and junction probe amplifications
Authors: Yan Lei , Liu Kailong , Sintim Herman O.
Published: May 2014

Concurrent cleavage of genomic duplex DNA using a cocktail of restriction endonucleases, ligation, rolling circle amplification and junction probe amplification and detection facilitated the detection of HPV virus in a clinical swab under isothermal conditions in a single tube.
A quick, simple, robust method to measure the acidity of ionic liquids
Authors: Gräsvik John , Hallett Jason P. , To Trang Quynh , Welton Tom
Published: May 2014

Introduced here is a quick, simple, robust method to measure acidity in ionic liquid (IL) systems by the use of the NMR-probe mesityl oxide.
Design, synthesis and biological evaluation of mitochondria targeting theranostic agents
Authors: Wu Song , Cao Qizhen , Wang Xiaolin , Cheng Kai , Cheng Zhen
Published: May 2014

Dual mitochondria targeting fluorescent F16–TPP analogues were designed and synthesized.
A specific fluorescent probe for NO based on a new NO-binding group
Authors: Lv Xin , Wang Yue , Zhang Song , Liu Yawei , Zhang Jian , Guo Wei
Published: May 2014

A highly selective fluorescent probe for NO was exploited based on a specific NO-binding group, 2-amino-3′-dimethylaminobiphenyl.
Optimization of absorption bands of dye-sensitized and perovskite tandem solar cells based on loss-in-potential values
Authors: Sobuś Jan , Ziółek Marcin
Published: May 2014

The dependence of best sunlight conversion efficiency and optimum absorption onset of the first sub-cell on the loss-in-potential (VL) and the number of sub-cells in tandem solar cells.
A truncated [MnIII12] tetrahedron from oxime-based [MnIII3O] building blocks
Authors: Frost J. M. , Sanz S. , Rajeshkumar T. , Pitak M. B. , Coles S. J. , Rajaraman G. , Wernsdorfer W. , Schnack J. , Lusby P. J. , Brechin E. K.
Published: May 2014

The use of the novel pro-ligand H4L combining the complimentary phenolic oxime and diethanolamine moieties in one organic framework, results in the formation of the first example of a [MnIII12] truncated tetrahedron.
Detection of HIV-1 p24 antigen using streptavidin–biotin and gold nanoparticles based immunoassay by inductively coupled plasma mass spectrometry
Authors: He Qian , Zhu Zhenli , Jin Lanlan , Peng Lu , Guo Wei , Hu Shenghong
Published: May 2014

A sensitive assay for detection of HIV-1 p24 antigen by ICP-MS was developed using a streptavidin–biotin system and Au nanoparticles based immunoassay.
A specific and rapid “on-off” acenaphthenequinone-based probe for HOCl detection and imaging in living cells
Authors: Zhao Jie , Li Hongjuan , Yang Kui , Sun Shiguo , Lu Aiping , Xu Yongqian
Published: May 2014

A facile sensor for monitoring hypochlorite both on test papers and living cells has been proposed.
Sol–gel chemistry for graphene–silica nanocomposite films
Authors: Innocenzi Plinio , Malfatti Luca , Lasio Barbara , Pinna Alessandra , Loche Danilo , Casula Maria F. , Alzari Valeria , Mariani Alberto
Published: May 2014

Graphene–silica films with high optical transparency have been obtained by adding a dispersion of exfoliated graphene into a silica sol.
Deterministic temperature shaping using plasmonic nanoparticle assemblies
Authors: Baffou Guillaume , Ureña Esteban Bermúdez , Berto Pascal , Monneret Serge , Quidant Romain , Rigneault Hervé
Published: May 2014

We developed a technique based on the use of smart patterns of gold nanoparticles under illumination to generate any temperature field on the microscale.
Phase transition of a perovskite strongly coupled to the vacuum field
Authors: Wang Shaojun , Mika Arkadiusz , Hutchison James A. , Genet Cyriaque , Jouaiti Abdelaziz , Hosseini Mir Wais , Ebbesen Thomas W.
Published: May 2014

Hysteresis and energy barrier of a phase transition are shown to be significantly modified by strong coupling (red curves).
Carbon nanospheres grown on graphene as anodes for Li-ion batteries
Authors: Zou Youlan , Zhou Xiangyang , Yang Juan
Published: May 2014

An electrode composed of graphene/carbon nanospheres is synthesized via in situ polymerization and carbonization, for Li-ion batteries.
Insitu X-ray reflectivity studies of molecular and molecular-cluster intercalation within purple membrane films
Authors: Mohd Kaus Noor Haida , Collins Andrew M. , Bikondoa Oier , Cresswell Philip T. , Bulpett Jennifer M. , Briscoe Wuge H. , Mann Stephen
Published: May 2014

In situ synchrotron XRR reveals the mechanism for intercalation of guest materials into the lamellar structure of the purple membrane film.
Cellular signalling pathways in immune aging and regeneration
Authors: Aspinall Richard , Lapenna Antonio , B-Lynch Christopher , Lang Pierre O.
Published: May 2014

The thymus is one of the cornerstones of an effective immune system. It produces new T-cells for the naïve T-cell pool, thus refreshing the peripheral repertoire. As we age, the thymus atrophies and there is a decrease in the area of active T-cell production. A decline in the output of the thymus eventually leads to changes in the peripheral T-cell pool which includes increases in the number of cells at or near their replicative limit and contraction of the repertoire. Debate about the age-associated changes in the thymus leading to functional decline centres on whether this is due to problems with the environment provided by the thymus or with defects in the progenitor cell compartment. In mice, the evidence points towards problems in the epithelial component of the thymus and the production of IL-7 (interleukin 7). But there are discussions about how appropriate mouse models are for human aging. We have developed a simple system that utilizes both human keratinocyte and fibroblast cell lines arrayed on a synthetic tantalum-coated matrix to provide a permissive environment for the maturation of human CD34+ haemopoietic progenitor cells into mature CD4+ or CD8+ T-lymphocytes. We have characterized the requirements for differentiation within these cultures and used this system to compare the ability of CD34+ cells derived from different sources to produce mature thymocytes. The TREC (T-cell receptor excision circle) assay was used as a means of identifying newly produced thymocytes.
Using embryonic stem cells to understand how glycosaminoglycans regulate differentiation
Authors: Holley Rebecca J. , Meade Kate A. , Merry Catherine L.R.
Published: May 2014

Differentiation and subsequent specialization of every cell within an organism is an intricate interwoven process. A complex network of signalling pathways eventually leads to the specification of a multitude of different cell types able to function co-operatively. HS (heparan sulfate) is a highly sulfated linear polysaccharide that resides at the pericellular cell–matrix interface where it dictates the binding and activity of a large number of proteins, including growth factors and morphogens such as members of the FGF (fibroblast growth factor) and BMP (bone morphogenetic protein) families. Embryonic stem cells derived from mice with mutations in components of the HS biosynthetic pathway provide an opportunity to dissect the contribution of HS to signalling pathways critical for regulating stem cell maintenance and differentiation. In addition to improving our understanding of signalling mechanisms, this knowledge enables the selection of exogenous HS saccharides to improve the efficiency and selectivity of directed differentiation protocols, offering a cost-effective alternative to high concentrations of expensive growth factors to drive differentiation towards a particular therapeutically relevant cell type.
Construction and analysis of microRNA‐transcription factor regulation network in arabidopsis
Authors: Tang Lie , Zhang Zhao , Gu Peizhen , Chen Ming
Published: May 2014

Transcription factors (TFs) and microRNAs (miRNAs) are two major types of regulators of gene expression, at transcriptional and post‐transcriptional levels, respectively. By gathering their gene regulatory relationships, gene regulatory networks (GRNs) could be formed. A network motif is a type of connection pattern among a set of nodes which appears significantly more frequently than in random networks. Investigations of the network motifs often yield biological insights into the nature of the network. The previous study on miRNA–TF regulation networks concentrated on animals, and relied heavily on computational predictions. The authors collected data concerning miRNA regulation and transcriptional regulation relationships in Arabidopsis from publicly available databases, and further incorporated them with the protein–protein interaction data. All the data in the author's collection are supported by experiments. They screened the network motifs, whose size ranges between 1 and 4. The biological implications of the motifs were further analysed, and a flower development related network was constructed as an example. In this example, they illustrated the relevance of the network with the given process, and proposed the association of several genes with flowers by a network cluster identification. In this study, they analysed the properties of the GRN in Arabidopsis, and discussed their biological implications, as well as their potential applications.
Construction and investigation of breast‐cancer‐specific ceRNA network based on the mRNA and miRNA expression data
Authors: Zhou Xionghui , Liu Juan , Wang Wei
Published: May 2014

It has been proved and widely acknowledged that messenger RNAs can talk to each other by competing for a limited pool of miRNAs. The competing endogenous RNAs are called as ceRNAs. Although some researchers have recently used ceRNAs to do biological function annotations, few of them have investigated the ceRNA network on specific disease systematically. In this work, using both miRNA expression data and mRNA expression data of breast cancer patient as well as the miRNA target relations, the authors proposed a computational method to construct a breast‐cancer‐specific ceRNA network by checking whether the shared miRNA sponges between the gene pairs are significant. The ceRNA network is shown to be scale‐free, thus the topological characters such as hub nodes and communities may provide important clues for the biological mechanism. Through investigation on the communities (the dense clusters) in the network, it was found that they are related to cancer hallmarks. In addition, through function annotation of the hub genes in the network, it was found that they are related to breast cancer. Moreover, classifiers based on the discriminative hubs can significantly distinguish breast cancer patients’ risks of distant metastasis in all the three independent data sets.
Foix-Alajouanine Syndrome Presenting as Acute Cauda Equina Syndrome: A Case Report
Authors: Menon K. Venugopal , Sorour Tamer M. M. , Raniga Sameer B.
Published: May 2014

Study Design

Case report.

Objective

Present a case of Foix-Alajouanine syndrome that presented as acute cauda equina syndrome and discuss the pathophysiology and management.

Methods

An adult male patient developed sudden onset of back pain and leg pain with weakness of the lower limbs and bladder/bowel dysfunction typical of cauda equina syndrome. Emergency magnetic resonance imaging revealed no compressive lesion in the spine but showed tortuous flow voids and end-on blood vessels in the peridural region suggesting spinal arteriovenous malformation resulting in Foix-Alajouanine syndrome.

Results

The case was managed by endovascular embolization with excellent results. The pathophysiology, imaging features, management, and literature review of the syndrome is discussed.

Conclusion

The authors conclude that this condition may be an important differential diagnosis for cauda equina syndrome.