bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficient Drilling of Ultra-HP/HT Wells in the Gulf of Thailand
Authors: Carpenter Chris
Published: February 2016

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 25392, “Efficient Drilling of Ultra-HP/HT Wells in the Gulf of Thailand,” by Joy Araujo, Schlumberger; Keittipong Kaotun, PTTEP; and Panupun Dumrongthai and A. Adrian, Schlumberger, prepared for the 2014 Offshore Technology Conference, Houston, 5–8 May. The paper has not been peer reviewed.

A new measurement-while-drilling (MWD) tool has been designed that can operate reliably at 200°C and 207 MPa, providing real-time direction and inclination surveys, azimuthal gamma ray, annular and internal pressure while drilling, and shock and vibration measurements. An operator in the Gulf of Thailand used this new MWD technology to drill wells in ultrahigh-pressure/high-temperature (HP/HT) reservoirs without the need to stop operation because of temperature limitations. Savings of ½ day per well have been achieved.

Introduction

Offshore drilling in the Gulf of Thailand increasingly challenges logging operations, with temperatures greater than 200°C. Hundreds of wells need to be drilled per year in this environment to fulfill long-term gas contracts. High efficiency is required in such a high-volume operation.

Existing commercial MWD and logging-while-drilling (LWD) technologies are only capable of operating up to 175°C, with an inherent decrease in reliability at higher temperatures. In the planned ultra-HP/HT projects, the bottomhole assembly (BHA), which includes an MWD tool for directional and inclination measurements in real time, will be pulled out of the hole once the circulating temperature reaches 175°C. Then, a new BHA, without measurement tools, will be used to continue drilling to total depth. This “blind” drilling section could be several hundred meters long, introducing risks associated with well control and well collision.

The main limiting factors in having MWD/LWD tools operating in these ultra-HP/HT environments are the downhole electronic components. Industry research studies show that plastic-encapsulated components have a life expectancy of approximately 1,000 hours at 150°C; this drops to less than 100 hours at 175°C. Ceramic-encapsulated components last longer at 175°C, but they are bigger and heavier than their plastic counterparts. Because space is restricted in these tools, the best compromise yields a mix of both ceramic- and plastic-encapsulated components.

To find a solution to this industrywide problem, significant effort was made over the last decade to develop custom electronics that can withstand high downhole temperatures. The newly developed MWD tool equipped with these novel electronics components was deployed in ultra-HP/HT wells. In these wells, the real-time measurements were necessary to drill the sections with operating temperatures greater than 175°C. It allowed minimization of drilling risks, enabled proper well placement, and improved drilling efficiency by eliminating one run.
Improving Drilling-Operation Efficiency by Use of a Mud Cap
Authors: Carpenter Chris
Published: February 2016

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 167985, “Improving Drilling-Operations Efficiency on an Ultranarrow- Margin HP/HT MPD Well by Use of a Mud Cap,” by Joy Oyovwevotu, SPE, Senergy; Eric Low, SPE, Bowleven; and Steve Nas, SPE, Schlumberger, prepared for the 2014 SPE Drilling Conference and Exhibition, Fort Worth, Texas, USA, 4–6 March. The paper has not been peer reviewed.

This paper describes the planning and execution of use of mud-cap fluid in the drilling of an ultranarrow-margin (0.50-lbm/gal window at the planning stage) high-pressure/ high-temperature (HP/HT) well from a jackup rig. Significant operational efficiency was gained from the use of cap fluids, making it possible to drill a well that otherwise would have been nearly impossible to drill with minimum lost time.

Introduction

The IM field is located in Block MLHP-7 in the Rio Del Rey basin offshore Cameroon in a water depth of 58 m (Fig. 1). At the target reservoir level, Well IM-5 was predicted to be a marginal HP/HT well with an estimated reservoir temperature of 181°C and a reservoir pressure of 9,971 psi (16.80 lbm/gal) at a depth of 3475-m true vertical depth subsea (TVDSS).

The Middle Isongo sand, intersected by Well IM-3, was the primary gas/ condensate target, consisting of deepwater sands with interbedded shales. The Middle Isongo target package consisted of three reservoir sands, the deepest two of which had not been penetrated in any of the earlier offset wells; this was the primary target of Well IM-5. A secondary target for Well IM-5 was the Intra Isongo, occurring between the Upper Isongo and the Middle Isongo main target.

The well design allowed the 12¼-in.-hole section to be drilled conventionally with statically overbalanced mud weight (MW), but it was impossible to drill the 8½-in. hole without using statically underbalanced MW with managed pressure drilling (MPD). Consequently, it was decided that the 12¼-in. hole would be drilled with MPD so that the crew could become familiar with the procedures and practices that would be needed when the 8½-in.-hole section was drilled. Given the uncertainty in the pore-pressure and fracture-gradient forecast, drilling the 8½-in.-hole section with statically underbalanced MW using MPD was seen as the most efficient means of well construction.
Technology Focus: History Matching and Forecasting (April 2015)
Authors: Emerick Alexandre
Published: February 2016

Technology Focus

Production forecasting is one of the main tasks of engineers involved in reservoir management. To perform it, they resort to models, which vary from simple decline curves to complex numerical simulations. Regardless of the model’s level of complexity, uncertainty will always exist in the forecasts. Therefore, reservoir engineers devote significant efforts trying to incorporate data in these models (history matching), aiming to mitigate uncertainty and improve the reliability of the predictions.

The reservoir-history-matching literature is quite extensive. The first works on automatic history matching were published in the 1960s. Nowadays, there is a wealth of history-matching methods. As a result, we observe that it is becoming a common industrial practice to generate multiple history-matched models, even for fairly complex problems with thousands of uncertainty variables and a large amount of data. However, we are still far from a definitive solution. Actually, it seems that there will be no single best history-matching technique. Instead, what we may have is the best method for the specific problem. Moreover, there are many challenges that are not completely addressed. In particular, most of the approaches seem overly simplistic to handle complex geology and structural uncertainties. Also, the computational demand for uncertainty quantification remains an issue. Therefore, industry and academia still have much work to do.

Another point I want to mention is that, back in 2009, SPE promoted a forum meeting titled “Getting to Robust Production Forecasts.” This meeting became the startup of a Global Integrated Workshop Series on production forecasting. To date, there have been six meetings; the latest was held this year in Malaysia. These workshops have the ambitious goal of developing a production-forecasting guideline. I think we will hear more about this in the coming years.

The papers summarized in this feature and the ones indicated in the additional-reading list are good examples of recent developments and field applications of history matching and forecasting. I hope you enjoy them. JPT

Recommended additional reading at OnePetro: www.onepetro.org.

SPE 163582 An Ensemble-Based Nonlinear Orthogonal Matching Pursuit Algorithm for Sparse History Matching of Reservoir Models by Ahmed H. Elsheikh, The University of Texas at Austin, et al.

SPE 170622 Integrated Subsurface Uncertainty Study and Application—A Case Study of a Chalk Reservoir, Greater Ekofisk Area, North Sea by H.J. Yu, ConocoPhillips, et al.

SPE 170945 Practical Considerations for Forecasting Production Data in Unconventional Reservoirs—Variable- Pressure Drop Case by P.W. Collins, Texas A&M University, et al.
Production From a Fractured Well With Finite Fracture Conductivity in a Closed Reservoir: An Exact Analytical Solution for Pseudosteady-State Flow
Authors: Chen Kang Ping
Published: February 2016

Pseudosteady-state (PSS) flow is a dominant time-dependent flow regime during constant-rate production from a finite closed reservoir. For a vertical well with a fully penetrated vertical fracture in a circular drainage area modeled as bounded by a slightly elliptical boundary, Prats et al. (1962) obtained an exact analytical solution for such a flow for the case of infinite fracture conductivity. For finite fracture conductivity, the current method to achieve a PSS solution is to run numerical simulations to long times. This paper extends the work of Prats et al. (1962), and presents the first exact analytical solution for PSS flow for a fully penetrated fractured vertical well with finite fracture conductivity. The exact analytical solution is expressed in terms of elementary functions, and it provides simple expressions for the PSS constant, dimensionless productivity index (PI), and effective wellbore radius. The present work eliminates the need of performing time-consuming numerical simulation for obtaining PSS solution for fractured wells in such a reservoir, and the new analytical solution can be used to generate approximate solutions for reservoirs of other geometrical shapes. The new solution can also be used for fracture-design optimization and production-rate decline analysis.
Effects of Pilates-Based Core Stability Training in Ambulant People With Multiple Sclerosis: Multicenter, Assessor-Blinded, Randomized Controlled Trial
Authors: Fox Esther E. , Hough Alan D. , Creanor Siobhan , Gear Margaret , Freeman Jennifer A.
Published: February 2016

Background

Pilates exercise is often undertaken by people with multiple sclerosis (MS) who have balance and mobility difficulties.

Objectives

The primary aim of the study was to compare the effects of 12 weeks of Pilates exercises with relaxation on balance and mobility. Secondary aims were: (1) to compare standardized exercises with relaxation and (2) to compare Pilates exercises with standardized exercises.

Methods

A multicenter, assessor-blinded, randomized controlled trial was conducted. Participants with Expanded Disability Status Scale scores of 4.0 to 6.5 were randomly allocated to groups receiving 12 weeks of Pilates exercises, standardized exercises, or relaxation. Assessments were undertaken at baseline and weeks 12 and 16 (primary outcome measure: 10-Meter Timed Walk Test [10MTW]).

Results

One hundred participants (mean age=54 years, 74% female) were randomized to study groups. Six participants relapsed (withdrew from the study), leaving 94 participants for intention-to-treat analysis. There was no significant difference in mean 10MTW measurements between the Pilates and relaxation groups. At 12 weeks, there was a mean reduction of 4.2 seconds for the standardized exercise group compared with the relaxation group (95% confidence interval [relaxation group minus standardized exercise group measurements]=0.0, 8.4) and a mean reduction of 3.7 seconds for the Pilates group compared with the standardized exercise group (95% confidence interval [Pilates group minus standardized exercise group measurements]=−0.4 to 7.8). At 16 weeks, mean 10MTW times for the standardized exercise group remained quicker than those for the Pilates and relaxation groups, although the differences were nonsignificant. There were no significant differences between the Pilates and relaxation groups for any secondary outcome measure.

Limitations

In this study, therapists were limited to a standardized basket of exercises that may have affected the study outcomes. Furthermore, choosing measures such as posturography to assess balance, accelerometry to assess walking, or a specific trunk assessment scale might have been more responsive in detecting changes in outcome.

Conclusion

Participants did not improve significantly, either in the short term or at the 4-week follow-up, on the 10MTW after 12 weeks of Pilates exercises compared with 12 weeks of relaxation.
Overviews in Education Research
Authors: Polanin Joshua R. , Maynard Brandy R. , Dell Nathaniel A.
Published: February 2016

Overviews, or syntheses of research syntheses, have become a popular approach to synthesizing the rapidly expanding body of research and systematic reviews. Despite their popularity, few guidelines exist and the state of the field in education is unclear. The purpose of this study is to describe the prevalence and current state of overviews of education research and to provide further guidance for conducting overviews and advance the evolution of overview methods. A comprehensive search across multiple online databases and gray literature repositories yielded 25 total education–related overviews. Our analysis revealed that many commonly reported aspects of systematic reviews, such as the search, screen, and coding procedures, were regularly unreported. Only a handful of overview authors discussed the synthesis technique and few authors acknowledged the overlap of included systematic reviews. Suggestions and preliminary guidelines for improving the rigor and utility of overviews are provided.
Can Cognitive Behavioral Therapy for Insomnia also treat fatigue, pain, and mood symptoms in individuals with traumatic brain injury? – A multiple case report
Authors: Lu William , Krellman Jason W. , Dijkers Marcel P.
Published: February 2016

BACKGROUND:

Individuals with traumatic brain injury (TBI) often develop sleep disorders post-injury. The most common one is insomnia, which can exacerbate other post-injury symptoms, including fatigue, impaired cognition, depression, anxiety, and pain. Cognitive Behavioral Therapy for Insomnia (CBT-I) is a manualized treatment that effectively treats insomnia with secondary effects on cognition, mood, and pain in various populations.

OBJECTIVE:

This paper reviews the use of CBT-I for three participants with TBI of different severities.

METHODS:

Pre- and post-treatment assessments of insomnia, fatigue, depression, anxiety, and pain were conducted. Mood was further assessed at follow-up. Minimal clinically important difference (MCID) scores derived from the research literature were used to establish clinically meaningful symptom improvement on self-report questionnaires.

RESULTS:

The reduction in insomnia severity scores for all three participants were not large enough to be considered a clinically significant improvement following CBT-I, although trends toward improvement were observed. However, all participants showed clinically significant reductions in anxiety at post-treatment; the effects persisted for 2 participants at follow-up. Reductions in depression symptoms were observed for 2 participants at post-treatment, and treatment effects persisted for 1 participant at follow-up. One participant endorsed clinically significant improvements in fatigue and pain severity.

CONCLUSIONS:

We conclude that CBT-I may provide secondary benefits for symptoms commonly experienced by individuals with TBI, especially mood disturbances.
Cognitive functioning following traumatic brain injury: A five-year follow-up
Authors: Marsh Nigel V. , Ludbrook Maria R. , Gaffaney Lauren C.
Published: February 2016

OBJECTIVE:

To describe the long-term prevalence and severity of cognitive deficits following significant (i.e., ventilation required for >24 hours) traumatic brain injury. To assess a comprehensive range of cognitive functions using psychometric measures with established normative, reliability, and validity data.

METHODS:

A group of 71 adults was assessed at approximately five years (mean = 66 months) following injury. Assessment of cognitive functioning covered the domains of intelligence, attention, verbal and visual memory, visual-spatial construction, and executive functions.

RESULTS:

Impairment was evident across all domains but prevalence varied both within and between domains. Across aspects of intelligence clinical impairment ranged from 8–25% , attention 39–62% , verbal memory 16–46% , visual memory 23–51% , visual-spatial construction 38% , and executive functions (verbal fluency) 13% . In addition, 3–23% of performances across the measures were in the borderline range, suggesting a high prevalence of subclinical deficit.

CONCLUSIONS:

Although the prevalence of impairment may vary across cognitive domains, long-term follow-up documented deficits in all six domains. These findings provide further evidence that while improvement of cognitive functioning following significant traumatic brain injury may be possible, recovery of function is unlikely.
The impact of comorbidity on cancer and its treatment
Authors: Sarfati Diana , Koczwara Bogda , Jackson Christopher
Published: February 2016

Answer questions and earn CME/CNE

Comorbidity is common among cancer patients and, with an aging population, is becoming more so. Comorbidity potentially affects the development, stage at diagnosis, treatment, and outcomes of people with cancer. Despite the intimate relationship between comorbidity and cancer, there is limited consensus on how to record, interpret, or manage comorbidity in the context of cancer, with the result that patients who have comorbidity are less likely to receive treatment with curative intent. Evidence in this area is lacking because of the frequent exclusion of patients with comorbidity from randomized controlled trials. There is evidence that some patients with comorbidity have potentially curative treatment unnecessarily modified, compromising optimal care. Patients with comorbidity have poorer survival, poorer quality of life, and higher health care costs. Strategies to address these issues include improving the evidence base for patients with comorbidity, further development of clinical tools to assist decision making, improved integration and coordination of care, and skill development for clinicians. CA Cancer J Clin 2016;66:337‐350. © 2016 American Cancer Society.
A COMPARATIVE STUDY OF KNOTS OF STAR FORMATION IN INTERACTING VERSUS SPIRAL GALAXIES
Authors: Smith Beverly J. , Zaragoza-Cardiel Javier , Struck Curtis , Olmsted Susan , Jones Keith
Published: February 2016

Interacting galaxies are known to have higher global rates of star formation on average than normal galaxies, relative to their stellar masses. Using UV and IR photometry combined with new and published Hα images, we have compared the star formation rates (SFRs) of ∼700 star forming complexes in 46 nearby interacting galaxy pairs with those of regions in 39 normal spiral galaxies. The interacting galaxies have proportionally more regions with high SFRs than the spirals. The most extreme regions in the interacting systems lie at the intersections of spiral/tidal structures, where gas is expected to pile up and trigger star formation. Published Hubble Space Telescope images show unusually large and luminous star clusters in the highest luminosity regions. The SFRs of the clumps correlate with measures of the dust attenuation, consistent with the idea that regions with more interstellar gas have more star formation. For the clumps with the highest SFRs, the apparent dust attenuation is consistent with the Calzetti starburst dust attenuation law. This suggests that the high luminosity regions are dominated by a central group of young stars surrounded by a shell of clumpy interstellar gas. In contrast, the lower luminosity clumps are bright in the UV relative to Hα, suggesting either a high differential attenuation between the ionized gas and the stars, or a post-starburst population bright in the UV but faded in Hα. The fraction of the global light of the galaxies in the clumps is higher on average for the interacting galaxies than for the spirals. Thus either star formation in interacting galaxies is “clumpier” on average, or the star forming regions in interacting galaxies are more luminous, dustier, or younger on average.
EXPLORING THE OVERABUNDANCE OF ULXs IN METAL- AND DUST-POOR LOCAL LYMAN BREAK ANALOGS
Authors: Basu-Zych Antara R. , Lehmer Bret , Fragos Tassos , Hornschemeier Ann , Yukita Mihoko , Zezas Andreas , Ptak Andy
Published: February 2016

We have studied high-mass X-ray binary (HMXB) populations within two low-metallicity, starburst galaxies, Haro 11 and VV 114. These galaxies serve as analogs to high-redshift (

) Lyman break galaxies and, within the larger sample of Lyman break analogs (LBAs), they are sufficiently nearby (<87 Mpc) to be spatially resolved by Chandra. Previous studies of the X-ray emission in LBAs have found that the 2–10 keV luminosity per star formation rate (SFR) in these galaxies is elevated, potentially because of their low metallicities (

). Theoretically, the progenitors of XRBs forming in lower metallicity environments lose less mass from stellar winds over their lifetimes, producing more massive compact objects (i.e., neutron stars and black holes), and thus resulting in more numerous and luminous HMXBs per SFR. In this paper, we have performed an in-depth study of the only two LBAs that have spatially resolved 2–10 keV emission with Chandra to present the bright end of the X-ray luminosity distribution of HMXBs (

≳ 1039 erg s−1; ultraluminous X-ray sources, ULXs) in these low-metallicity galaxies, based on eight detected ULXs. Compared with the star-forming galaxy X-ray luminosity function (XLF) presented by Mineo et al., Haro 11 and VV 114 host

times more

erg s−1 sources than expected given their SFRs. We simulate the effects of source blending from crowded lower-luminosity HMXBs using the star-forming galaxy XLF and then vary the XLF normalizations and bright-end slopes until we reproduce the observed point source luminosity distributions. We find that these LBAs have a shallower bright-end slope (

) than the standard XLF (

). If we conservatively assume that the brightest X-ray source from each galaxy is powered by an accreting supermassive black hole rather than an HMXB and eliminate these sources from consideration, the luminosity distribution becomes poorly constrained but does appear to be consistent with a standard XLF.
THE COMPACT STAR-FORMING COMPLEX AT THE HEART OF NGC 253*

†

‡
Authors: Davidge T. J.
Published: February 2016

We discuss integral field spectra of the compact star-forming complex that is the brightest near-infrared (NIR) source in the central regions of the starburst galaxy NGC 253. The spectra cover the H and K passbands and were recorded with the Gemini NIR Spectrograph during subarcsecond seeing conditions. Absorption features in the spectrum of the star-forming complex are weaker than in the surroundings. An absorption feature is found near 1.78 μm that coincides with the location of a C2 bandhead. If this feature is due to C2 then the star-forming complex has been in place for at least a few hundred Myr. Emission lines of Brγ, [Fe ii], and He i 2.06 μm do not track the NIR continuum light. Pockets of star-forming activity that do not have associated concentrations of red supergiants, and so likely have ages <8 Myr, are found along the western edge of the complex, and there is evidence that one such pocket contains a rich population of Wolf–Rayet stars. Unless the star-forming complex is significantly more metal-poor than the surroundings, then a significant fraction of its total mass is in stars with ages <8 Myr. If the present-day star formation rate is maintained then the timescale to double its stellar mass ranges from a few Myr to a few tens of Myr, depending on the contribution made by stars older than ∼8 Myr. If—as suggested by some studies—the star-forming complex is centered on the galaxy’s nucleus, which presumably contains a large population of old and intermediate-age stars, then the nucleus of NGC 253 is currently experiencing a phase of rapid growth in its stellar mass.
DISTRIBUTION AND MASS OF DIFFUSE AND DENSE CO GAS IN THE MILKY WAY
Authors: Roman-Duval Julia , Heyer Mark , Brunt Christopher M. , Clark Paul , Klessen Ralf , Shetty Rahul
Published: February 2016

Emission from carbon monoxide (CO) is ubiquitously used as a tracer of dense star-forming molecular clouds. There is, however, growing evidence that a significant fraction of CO emission originates from diffuse molecular gas. Quantifying the contribution of diffuse CO-emitting gas is vital for understanding the relation between molecular gas and star formation. We examine the Galactic distribution of two CO-emitting gas components, a high column density component detected in 13CO and 12CO, and a low column density component detected in 12CO, but not in 13CO. The “diffuse” and “dense” components are identified using a combination of smoothing, masking, and erosion/dilation procedures, making use of three large-scale 12CO and 13CO surveys of the inner and outer Milky Way. The diffuse component, which globally represents 25% (1.5 × 108
M
⊙) of the total molecular gas mass (6.5

M
⊙), is more extended perpendicular to the Galactic plane. The fraction of diffuse gas increases from ∼10%–20% at a galactocentric radius of 3–4 kpc to 50% at 15 kpc, and increases with decreasing surface density. In the inner Galaxy, a yet denser component traced by CS emission represents 14% of the total molecular gas mass traced by 12CO emission. Only 14% of the molecular gas mass traced by 12CO emission is identified as part of molecular clouds in 13CO surveys by cloud identification algorithms. This study indicates that CO emission not only traces star-forming clouds, but also a significant diffuse molecular ISM component.
A SIMPLE SCHEME TO IMPLEMENT A NONLOCAL TURBULENT CONVECTION MODEL FOR CONVECTIVE OVERSHOOT MIXING
Authors: Zhang Q. S.
Published: February 2016

Classical “ballistic” overshoot models show some contradictions and are not consistent with numerical simulations and asteroseismic studies. Asteroseismic studies imply that overshoot is a weak mixing process. A diffusion model is suitable to deal with it. The form of diffusion coefficient in a diffusion model is crucial. Because overshoot mixing is related to convective heat transport (i.e., entropy mixing), there should be some similarity between them. A recent overshoot mixing model shows consistency between composition mixing and entropy mixing in the overshoot region. A prerequisite to apply the model is to know the dissipation rate of turbulent kinetic energy. The dissipation rate can be worked out by solving turbulent convection models (TCMs). But it is difficult to apply TCMs because of some numerical problems and the enormous time cost. In order to find a convenient way, we have used the asymptotic solution and simplified the TCM to a single linear equation for turbulent kinetic energy. This linear model is easy to implement in calculations of stellar evolution with negligible extra time cost. We have tested the linear model in stellar evolution, and have found that it can well reproduce the turbulent kinetic energy profile of the full TCM, as well as the diffusion coefficient, abundance profile, and stellar evolutionary tracks. We have also studied the effects of different values of the model parameters and have found that the effect due to the modification of temperature gradient in the overshoot region is slight.
HELIOSHEATH MAGNETIC FIELD AND PLASMA OBSERVED BY VOYAGER 2 DURING 2012 IN THE RISING PHASE OF SOLAR CYCLE 24
Authors: Burlaga L. F. , Ness N. F. , Richardson J. D. , Decker R. B. , Krimigis S. M.
Published: February 2016

We discuss magnetic field and plasma observations of the heliosheath made by Voyager 2 (V2) during 2012, when V2 was observing the effects of increasing solar activity following the solar minimum in 2009. The average magnetic field strength B was 0.14 nT and B reached 0.29 nT on day 249. V2 was in a unipolar region in which the magnetic polarity was directed away from the Sun along the Parker spiral 88% of the time, indicating that V2 was poleward of the heliospheric current sheet throughout most of 2012. The magnetic flux at V2 during 2012 was constant. A merged interaction region (MIR) was observed, and the flow speed increased as the MIR moved past V2. The MIR caused a decrease in the >70 MeV nuc−1 cosmic-ray intensity. The increments of B can be described by a q-Gaussian distribution with q = 1.2 ± 0.1 for daily averages and q = 1.82 ± 0.03 for hour averages. Eight isolated current sheets (“PBLs”) and four closely spaced pairs of current sheets were observed. The average change of B across the current sheets was a factor of ≈2, and B increased or decreased with equal probability. Magnetic holes and magnetic humps were also observed. The characteristic size of the PBLs was ≈6 R
L, where R
L is the Larmor radius of protons, and the characteristic sizes of the magnetic holes and humps were ≈38 R
L and ≈11 R
L, respectively.
INNER-SHELL PHOTOIONIZATION STUDIES OF NEUTRAL ATOMIC NITROGEN
Authors: Stolte W. C. , Jonauskas V. , Lindle D. W. , Sant’Anna M. M. , Savin D. W.
Published: February 2016

Inner-shell ionization of a 1s electron by either photons or electrons is important for X-ray photoionized objects such as active galactic nuclei and electron-ionized sources such as supernova remnants. Modeling and interpreting observations of such objects requires accurate predictions for the charge state distribution (CSD), which results as the 1s-hole system stabilizes. Due to the complexity of the complete stabilization process, few modern calculations exist and the community currently relies on 40-year-old atomic data. Here, we present a combined experimental and theoretical study for inner-shell photoionization of neutral atomic nitrogen for photon energies of 403–475 eV. Results are reported for the total ion yield cross section, for the branching ratios for formation of N+,

, and

, and for the average charge state. We find significant differences when comparing to the data currently available to the astrophysics community. For example, while the branching ratio to

is somewhat reduced, that for N+ is greatly increased, and that to

, which was predicted to be zero, grows to

at the higher photon energies studied. This work demonstrates some of the shortcomings in the theoretical CSD data base for inner-shell ionization and points the way for the improvements needed to more reliably model the role of inner-shell ionization of cosmic plasmas.
THE ELM SURVEY. VII. ORBITAL PROPERTIES OF LOW-MASS WHITE DWARF BINARIES*
Authors: Brown Warren R. , Gianninas A. , Kilic Mukremin , Kenyon Scott J. , Prieto Carlos Allende
Published: February 2016

We present the discovery of 15 extremely low-mass (

) white dwarf (WD) candidates, 9 of which are in ultra-compact double-degenerate binaries. Our targeted extremely low-mass Survey sample now includes 76 binaries. The sample has a lognormal distribution of orbital periods with a median period of 5.4 hr. The velocity amplitudes imply that the binary companions have a normal distribution of mass with 0.76 M
⊙ mean and 0.25 M
⊙ dispersion. Thus extremely low-mass WDs are found in binaries with a typical mass ratio of 1:4. Statistically speaking, 95% of the WD binaries have a total mass below the Chandrasekhar mass, and thus are not type Ia supernova progenitors. Yet half of the observed binaries will merge in less than 6 Gyr due to gravitational wave radiation; probable outcomes include single massive WDs and stable mass transfer AM CVn binaries.
PLANETARY SYSTEM FORMATION IN THE PROTOPLANETARY DISK AROUND HL TAURI
Authors: Akiyama Eiji , Hasegawa Yasuhiro , Hayashi Masahiko , Iguchi Satoru
Published: February 2016

We reprocess the Atacama Large Millimeter/Submillimeter Array (ALMA) long-baseline science verification data taken toward HL Tauri. Assuming the observed gaps are opened up by currently forming, unseen bodies, we estimate the mass of such hypothetical bodies based on the following two approaches: the Hill radius analysis and a more elaborate approach developed from the angular momentum transfer analysis in gas disks. For the former, the measured gap widths are used for estimating the mass of the bodies, while for the latter, the measured gap depths are utilized. We show that their masses are comparable to or less than the mass of Jovian planets. By evaluating Toomre’s gravitational instability (GI) condition and cooling effect, we find that the GI might be a mechanism to form the bodies in the outer region of the disk. As the disk might be gravitationally unstable only in the outer region of the disk, inward planetary migration would be needed to construct the current architecture of the observed disk. We estimate the gap-opening mass and show that type II migration might be able to play such a role. Combining GIs with inward migration, we conjecture that all of the observed gaps may be a consequence of bodies that might have originally formed at the outer part of the disk, and have subsequently migrated to the current locations. While ALMA’s unprecedented high spatial resolution observations can revolutionize our picture of planet formation, more dedicated observational and theoretical studies are needed to fully understand the HL Tauri images.
DETECTION AND CHARACTERIZATION OF EXTRASOLAR PLANETS THROUGH MEAN-MOTION RESONANCES. I. SIMULATIONS OF HYPOTHETICAL DEBRIS DISKS
Authors: Tabeshian Maryam , Wiegert Paul A.
Published: February 2016

The gravitational influence of a planet on a nearby disk provides a powerful tool for detecting and studying extrasolar planetary systems. Here we demonstrate that gaps can be opened in dynamically cold debris disks at the mean-motion resonances of an orbiting planet. The gaps are opened away from the orbit of the planet itself, revealing that not all disk gaps need contain a planetary body. These gaps are large and deep enough to be detectable in resolved disk images for a wide range of reasonable disk-planet parameters, though we are not aware of any such gaps detected to date. The gap shape and size are diagnostic of the planet location, eccentricity and mass, and allow one to infer the existence of unseen planets, as well as many important parameters of both seen and unseen planets in these systems. We present expressions to allow the planetary mass and semimajor axis to be calculated from observed gap width and location.
SPECTRAL LINE SURVEY TOWARD MOLECULAR CLOUDS IN THE LARGE MAGELLANIC CLOUD
Authors: Nishimura Yuri , Shimonishi Takashi , Watanabe Yoshimasa , Sakai Nami , Aikawa Yuri , Kawamura Akiko , Yamamoto Satoshi
Published: February 2016

Spectral line survey observations of seven molecular clouds in the Large Magellanic Cloud (LMC) have been conducted in the 3 mm band with the Mopra 22 m telescope to reveal chemical compositions in low metallicity conditions. Spectral lines of fundamental species such as CS, SO, CCH, HCN, HCO+, and HNC are detected in addition to those of CO and 13CO, while CH3OH is not detected in any source and N2H+ is marginally detected in two sources. The molecular-cloud scale (10 pc scale) chemical composition is found to be similar among the seven sources regardless of different star formation activities, and hence, it represents the chemical composition characteristic of the LMC without influences by star formation activities. In comparison with chemical compositions of Galactic sources, the characteristic features are (1) deficient N-bearing molecules, (2) abundant CCH, and (3) deficient CH3OH. Feature (1) is due to a lower elemental abundance of nitrogen in the LMC, whereas features (2) and (3) seem to originate from extended photodissociation regions and warmer temperature in cloud peripheries due to a lower abundance of dust grains in the low metallicity condition. In spite of general resemblance of chemical abundances among the seven sources, the CS/HCO+ and SO/HCO+ ratios are found to be slightly higher in a quiescent molecular cloud. An origin of this trend is discussed in relation to possible depletion of sulfur along the molecular cloud formation.
ON THE LATE-TIME SPECTRAL SOFTENING FOUND IN X-RAY AFTERGLOWS OF GAMMA-RAY BURSTS
Authors: Wang Yuan-Zhu , Zhao Yinan , Shao Lang , Liang En-Wei , Lu Zu-Jia
Published: February 2016

Strong spectral softening has been revealed in the late X-ray afterglows of some gamma-ray bursts (GRBs). The scenario of X-ray scattering around the circumburst dusty medium has been supported by previous works due to its overall successful prediction of both the temporal and spectral evolution of some X-ray afterglows. To further investigate the observed feature of spectral softening we now systematically search the X-ray afterglows detected by the X-ray telescope aboard Swift and collect 12 GRBs with significant late-time spectral softening. We find that dust scattering could be the dominant radiative mechanism for these X-ray afterglows regarding their temporal and spectral features. For some well-observed bursts with high-quality data, the time-resolved spectra could be well-produced within the scattering scenario by taking into account the X-ray absorption from the circumburst medium. We also find that during spectral softening the power-law index in the high-energy end of the spectra does not vary much. The spectral softening is mainly manifested by the spectral peak energy continually moving to the soft end.
ARE THERE TWO DISTINCT SOLAR ENERGETIC PARTICLE RELEASES IN THE 2012 MAY 17 GROUND LEVEL ENHANCEMENT EVENT?
Authors: Ding Liu-Guan , Jiang Yong , Li Gang
Published: February 2016

We examine ion release times in the solar vicinity for the 2012 May 17 Ground Level Enhancement event using the velocity dispersion analysis method. In situ energetic proton data from Solar and Heliospheric Observatory (SOHO)/Energetic and Relativistic Nuclei and Electron and Geostationary Operational Environmental Satellite are used. We find two distinct releases of Solar Energetic Particles (SEPs) near the Sun, separated by ∼40 minutes. From soft X-ray observations, we find that the first release coincides with the solar flare eruption: the release starts from the flare onset and ends near the peak of the soft X-ray; type-III radio bursts also occur when the release starts. A type II radio burst may also start at the begining of the release. However, the associated Coronal Mass Ejection (CME) only has a height of 0.08R

s
from extrapolation of SOHO/LASCO data. At the start of the second release, the CME propagates to more than 8.4R

s
in height, and there are signatures of an enhanced type II radio burst. The time-integrated spectra for the two releases differ. The spectrum for the second release shows the common double-power-law feature of gradual SEP events. The spectrum for the first release does not resemble power laws because there is considerable modulation at lower energies. Based on our analysis, we suggest that SEPs of the first release were dominated by particles accelerated at the flare, and those of the second release were dominated by particles accelerated at the associated CME-driven shock. Our study may be important to understand certain extreme SEP events.
HECTOMAP AND HORIZON RUN 4: DENSE STRUCTURES AND VOIDS IN THE REAL AND SIMULATED UNIVERSE
Authors: Hwang Ho Seong , Geller Margaret J. , Park Changbom , Fabricant Daniel G. , Kurtz Michael J. , Rines Kenneth J. , Kim Juhan , Diaferio Antonaldo , Zahid H. Jabran , Berlind Perry , Calkins Michael , Tokarz Susan , Moran Sean
Published: February 2016

HectoMAP is a dense redshift survey of red galaxies covering a 53 deg2 strip of the northern sky. HectoMAP is 97% complete for galaxies with r < 20.5, (g− r) > 1.0, and (r − i) > 0.5. The survey enables tests of the physical properties of large-scale structure at intermediate redshift against cosmological models. We use the Horizon Run 4, one of the densest and largest cosmological simulations based on the standard Λ Cold Dark Matter (ΛCDM) model, to compare the physical properties of observed large-scale structures with simulated ones in a volume-limited sample covering 8 × 106
h
−3 Mpc3 in the redshift range 0.22 < z < 0.44. We apply the same criteria to the observations and simulations to identify over- and under-dense large-scale features of the galaxy distribution. The richness and size distributions of observed over-dense structures agree well with the simulated ones. Observations and simulations also agree for the volume and size distributions of under-dense structures, voids. The properties of the largest over-dense structure and the largest void in HectoMAP are well within the distributions for the largest structures drawn from 300 Horizon Run 4 mock surveys. Overall the size, richness and volume distributions of observed large-scale structures in the redshift range 0.22 < z < 0.44 are remarkably consistent with predictions of the standard ΛCDM model.
THE ALHAMBRA SURVEY: EVOLUTION OF GALAXY SPECTRAL SEGREGATION
Authors: Hurtado-Gil Ll. , Arnalte-Mur P. , Martínez V. J. , Fernández-Soto A. , Stefanon M. , Ascaso B. , López-Sanjuán C. , Márquez I. , Pović M. , Viironen K. , Aguerri J. A. L. , Alfaro E. , Aparicio-Villegas T. , Benítez N. , Broadhurst T. , Cabrera-Caño J. , Castander F. J. , Cepa J. , Cerviño M. , Cristóbal-Hornillos D. , Delgado R. M. González , Husillos C. , Infante L. , Masegosa J. , Moles M. , Molino A. , Olmo A. del , Paredes S. , Perea J. , Prada F. , Quintana J. M.
Published: February 2016

We study the clustering of galaxies as a function of spectral type and redshift in the range 0.35 < z < 1.1 using data from the Advanced Large Homogeneous Area Medium Band Redshift Astronomical (ALHAMBRA) survey. The data cover 2.381 deg2 in 7 fields, after applying a detailed angular selection mask, with accurate photometric redshifts

down to I

AB
 < 24. From this catalog we draw five fixed number density redshift-limited bins. We estimate the clustering evolution for two different spectral populations selected using the ALHAMBRA-based photometric templates: quiescent and star-forming galaxies. For each sample we measure the real-space clustering using the projected correlation function. Our calculations are performed over the range [0.03, 10.0] h
−1 Mpc, allowing us to find a steeper trend for

Mpc, which is especially clear for star-forming galaxies. Our analysis also shows a clear early differentiation in the clustering properties of both populations: star-forming galaxies show weaker clustering with evolution in the correlation length over the analyzed redshift range, while quiescent galaxies show stronger clustering already at high redshifts and no appreciable evolution. We also perform the bias calculation where similar segregation is found, but now it is among the quiescent galaxies where a growing evolution with redshift is clearer (abrigatted). These findings clearly corroborate the well-known color–density relation, confirming that quiescent galaxies are mainly located in dark matter halos that are more massive than those typically populated by star-forming galaxies.
DISCOVERY OF ROTATIONAL MODULATIONS IN THE PLANETARY-MASS COMPANION 2M1207b: INTERMEDIATE ROTATION PERIOD AND HETEROGENEOUS CLOUDS IN A LOW GRAVITY ATMOSPHERE
Authors: Zhou Yifan , Apai Dániel , Schneider Glenn H , Marley Mark S. , Showman Adam P.
Published: February 2016

Rotational modulations of brown dwarfs have recently provided powerful constraints on the properties of ultra-cool atmospheres, including longitudinal and vertical cloud structures and cloud evolution. Furthermore, periodic light curves directly probe the rotational periods of ultra-cool objects. We present here, for the first time, time-resolved high-precision photometric measurements of a planetary-mass companion, 2M1207b. We observed the binary system with Hubble Space Telescope/Wide Field Camera 3 in two bands and with two spacecraft roll angles. Using point-spread function-based photometry, we reach a nearly photon-noise limited accuracy for both the primary and the secondary. While the primary is consistent with a flat light curve, the secondary shows modulations that are clearly detected in the combined light curve as well as in different subsets of the data. The amplitudes are 1.36% in the F125W and 0.78% in the F160W filters, respectively. By fitting sine waves to the light curves, we find a consistent period of

hr and similar phases in both bands. The J- and H-band amplitude ratio of 2M1207b is very similar to a field brown dwarf that has identical spectral type but different J–H color. Importantly, our study also measures, for the first time, the rotation period for a directly imaged extra-solar planetary-mass companion.
TRANSIT TIMING TO FIRST ORDER IN ECCENTRICITY
Authors: Agol Eric , Deck Katherine
Published: February 2016

Characterization of transiting planets with transit timing variations (TTVs) requires understanding how to translate the observed TTVs into masses and orbital elements of the planets. This can be challenging in multi-planet transiting systems, but fortunately these systems tend to be nearly plane-parallel and low eccentricity. Here we present a novel derivation of analytic formulae for TTVs that are accurate to first order in the planet–star mass ratios and in the orbital eccentricities. These formulae are accurate in proximity to first-order resonances, as well as away from resonance, and compare well with more computationally expensive N-body integrations in the low-eccentricity, low mass-ratio regime when applied to simulated and to actual multi-transiting Kepler planet systems. We make code available for implementing these formulae.
SPECTRUM AND ANISOTROPY OF TURBULENCE FROM MULTI-FREQUENCY MEASUREMENT OF SYNCHROTRON POLARIZATION
Authors: Lazarian A. , Pogosyan D.
Published: February 2016

We consider turbulent synchrotron-emitting media that also exhibit Faraday rotation and provide a statistical description of synchrotron polarization fluctuations. In particular, we consider these fluctuations as a function of the spatial separation of the direction of the measurements and as a function of wavelength for the same line of sight. On the basis of our general analytical approach, we introduce several measures that can be used to obtain the spectral slopes and correlation scales of both the underlying magnetic turbulence responsible for emission and the spectrum of the Faraday rotation fluctuations. We show the synergetic nature of these measures and discuss how the study can be performed using sparsely sampled interferometric data. We also discuss how additional characteristics of turbulence can be obtained, including the turbulence anisotropy and the three-dimensional direction of the mean magnetic field. In addition, we consider the cases when the synchrotron emission and Faraday rotation regions are spatially separated. Appealing to our earlier study, we explain that our new results are applicable to a wide range of spectral indexes of relativistic electrons responsible for synchrotron emission. We expect wide application of our techniques, both with existing synchrotron data sets and with big forthcoming data sets from LOFAR and SKA.