bluuebunny/crossref_metadata_2025 huggingface dataset:
RECONSTRUCTION OF EXPORT SERIES FOR PERU BEFORE THE GREAT DEPRESSION
Authors: Zegarra Luis Felipe
Published: June 2018

This article discusses the available sources of information on the value and volume of Peru’s exports and estimates the current value of exports, the index of export prices and the quantum of exports using a wide variety of sources. By relying on several sources, I estimate the first complete series of the current value of exports for Peru for 1830-1930. Importantly, I adjust other studies’ estimates by taking into account the deficiencies of foreign sources and by distinguishing between exports of specie and of minerals. The estimations show that exports experienced substantial growth in the 1850s and 1860s, during the Guano Era. Exports stagnated in the 1870s and dropped during the War of the Pacific (1879-1883) before recovering in the late 19thand early 20thcenturies, especially during World War I.
Growth in syntactic complexity between four years and adulthood: evidence from a narrative task
Authors: FRIZELLE Pauline , THOMPSON Paul A. , MCDONALD David , BISHOP Dorothy V. M.
Published: June 2018

Studies examining productive syntax have used varying elicitation methods and have tended to focus on either young children or adolescents/adults, so we lack an account of syntactic development throughout middle childhood. We describe here the results of an analysis of clause complexity in narratives produced by 354 speakers aged from four years to adulthood using the Expressive, Receptive, and Recall of Narrative Instrument (ERRNI). We show that the number of clauses per utterance increased steadily through this age range. However, the distribution of clause types depended on which of two stories was narrated, even though both stories were designed to have a similar story structure. In addition, clausal complexity was remarkably similar regardless of whether the speaker described a narrative from pictures, or whether the same narrative was recalled from memory. Finally, our findings with the youngest children showed that the task of generating a narrative from pictures may underestimate syntactic competence in those aged below five years.
Food Production Standards and the Chinese Local State: Exploring New Patterns of Environmental Governance in the Bamboo Shoot Industry in Lin'an
Authors: Chan Kin Wing (Ray) , Flynn Andrew
Published: June 2018

Although current studies into Chinese food supply and quality provide explanations for the causality of food problems, there is limited inquiry into the role of the county government. This is a serious omission for two main reasons: first, because county governments perform a key role in providing support for farmers through agricultural extension services and farmers’ cooperatives, and second, because county-level administrative divisions are central to developing novel instruments to manage supply chain relationships, such as food production standards. We investigate the key players involved in standard making and delivery at the county level. We also analyse how and why the county government engages in standard-setting activities. We use Lin'an's bamboo shoot production industry as a case study to understand how the local state implements “hazard-free,” “green” and “forest food” production standards. The paper concludes that traditional conceptualizations of the local state do not sufficiently address how nature, knowledge of standards and state authority co-produce institutional capacity to control food supply and quality in China. In practice, the local state engages with non-state actors to achieve superficial environmental efforts, such as developing food production standards to throw a “green cloak” over a productivist model.
Autochthonous spread of DENV-3 genotype III in Malaysia mitigated by pre-existing homotypic and heterotypic immunity
Authors: Tan K. K. , Nellis S. , Zulkifle N. I. , Sulaiman S. , AbuBakar S.
Published: June 2018

Dengue virus type 3 genotype III (DENV-3/III) is widely distributed in most dengue-endemic regions. It emerged in Malaysia in 2008 and autochthonously spread in the midst of endemic DENV-3/I circulation. The spread, however, was limited and the virus did not cause any major outbreak. Spatiotemporal distribution study of DENV-3 over the period between 2005 and 2011 revealed that dengue cases involving DENV-3/III occurred mostly in areas without pre-existing circulating DENV-3. Neutralisation assays performed using sera of patients with the respective infection showed that the DENV-3/III viruses can be effectively neutralised by sera of patients with DENV-3 infection (50% foci reduction neutralisation titres (FRNT50) > 1300). Sera of patients with DENV-1 infection (FRNT50⩾ 190), but not sera of patients with DENV-2 infection (FRNT50⩽ 50), were also able to neutralise the virus. These findings highlight the possibility that the pre-existing homotypic DENV-3 and the cross-reacting heterotypic DENV-1 antibody responses could play a role in mitigating a major outbreak involving DENV-3/III in the Klang Valley, Malaysia.
Measles outbreak risk in Pakistan: exploring the potential of combining vaccination coverage and incidence data with novel data-streams to strengthen control
Authors: Wesolowski Amy , Winter Amy , Tatem Andrew J. , Qureshi Taimur , Engø-Monsen Kenth , Buckee Caroline O. , Cummings Derek A. T. , Metcalf C. Jessica E.
Published: June 2018

Although measles incidence has reached historic lows in many parts of the world, the disease still causes substantial morbidity globally. Even where control programs have succeeded in driving measles locally extinct, unless vaccination coverage is maintained at extremely high levels, susceptible numbers may increase sufficiently to spark large outbreaks. Human mobility will drive potentially infectious contacts and interact with the landscape of susceptibility to determine the pattern of measles outbreaks. These interactions have proved difficult to characterise empirically. We explore the degree to which new sources of data combined with existing public health data can be used to evaluate the landscape of immunity and the role of spatial movement for measles introductions by retrospectively evaluating our ability to predict measles outbreaks in vaccinated populations. Using inferred spatial patterns of accumulation of susceptible individuals and travel data, we predicted the timing of epidemics in each district of Pakistan during a large measles outbreak in 2012–2013 with over 30 000 reported cases. We combined these data with mobility data extracted from over 40 million mobile phone subscribers during the same time frame in the country to quantify the role of connectivity in the spread of measles. We investigate how different approaches could contribute to targeting vaccination efforts to reach districts before outbreaks started. While some prediction was possible, accuracy was low and we discuss key uncertainties linked to existing data streams that impede such inference and detail what data might be necessary to robustly infer timing of epidemics.
Models for the two-phase flow of concentrated suspensions
Authors: AHNERT TOBIAS , MÜNCH ANDREAS , WAGNER BARBARA
Published: June 2018

A new two-phase model for concentrated suspensions is derived that incorporates a constitutive law combining the rheology for non-Brownian suspension and granular flow. The resulting model exhibits a yield-stress behaviour for the solid phase depending on the collision pressure. This property is investigated for the simple geometry of plane Poiseuille flow, where an unyielded or jammed zone of finite width arises in the centre of the channel. For the steady states of this problem, the governing equations are reduced to a boundary value problem for a system of ordinary differential equations and the conditions for existence of solutions with jammed regions are investigated using phase-space methods. For the general time-dependent case a new drift-flux model is derived using matched asymptotic expansions that takes into account the boundary layers at the walls and the interface between the yielded and unyielded region. The drift-flux model is used to numerically study the dynamic behaviour of the suspension flow, including the appearance and evolution of an unyielded or jammed regions.
Impulsivity and decision-making in obsessive-compulsive disorder after effective deep brain stimulation or treatment as usual
Authors: Grassi Giacomo , Figee Martijn , Ooms Pieter , Righi Lorenzo , Nakamae Takashi , Pallanti Stefano , Schuurman Rick , Denys Damiaan
Published: June 2018

Objective

Impulsivity and impaired decision-making have been proposed as obsessive-compulsive disorder (OCD) endophenotypes, running in OCD and their healthy relatives independently of symptom severity and medication status. Deep brain stimulation (DBS) targeting the ventral limb of the internal capsule (vALIC) and the nucleus accumbens (Nacc) is an effective treatment strategy for treatment-refractory OCD. The effectiveness of vALIC-DBS for OCD has been linked to its effects on a frontostriatal network that is also implicated in reward, impulse control, and decision-making. While vALIC-DBS has been shown to restore reward dysfunction in OCD patients, little is known about the effects of vALIC-DBS on impulsivity and decision-making. The aim of the study was to compare cognitive impulsivity and decision-making between OCD patients undergoing effective vALIC-DBS or treatment as usual (TAU), and healthy controls.

Methods

We used decision-making performances under ambiguity on the Iowa Gambling Task and reflection impulsivity on the Beads Task to compare 20 OCD patients effectively treated with vALIC-DBS, 40 matched OCD patients undergoing effective TAU (medication and/or cognitive behavioural therapy), and 40 healthy subjects. Effective treatment was defined as at least 35% improvement of OCD symptoms.

Results

OCD patients, irrespective of treatment modality (DBS or TAU), showed increased reflection impulsivity and impaired decision-making compared to healthy controls. No differences were observed between OCD patients treated with DBS or TAU.

Conclusion

OCD patients effectively treated with vALIC-DBS or TAU display increased reflection impulsivity and impaired decision-making independent of the type of treatment.
Does bilingualism really affect social flexibility?
Authors: VIVES MARC LLUÍS , REPKE LYDIA , COSTA ALBERT
Published: June 2018

Ikizer and Ramirez-Esparza (2017) reported a study suggesting that bilingualism may have a positive impact on people's social skills. They found that a) bilinguals scored higher on a scale that is supposed to reveal social flexibility, and that b) they also report having social interactions more frequently than monolinguals. The authors relate this advantage in social flexibility to the need of exercising language switching in bilingual speakers. In this commentary, we argue that their arguments are not theoretically sound and that their observations are not compelling enough to reach this conclusion.
Cognitive control among immersed bilinguals: Considering differences in linguistic and non-linguistic processing
Authors: SABOURIN LAURA , VĪNERTE SANTA
Published: June 2018

While several studies have shown a bilingual advantage in cognitive control, others have refuted such findings, leading to debates regarding the existence of bilingual benefits. The current study conducts two experiments to investigate this issue, focusing on the effect of the age of second language immersion in young adult non-immigrant bilinguals. We use a colour-word Stroop task to assess linguistic cognitive control, and an Attention Network Test to examine non-linguistic cognitive control. Results show significant differences between Simultaneous and Early Sequential bilinguals (typically grouped together as ‘early’) in the Stroop task, but these only become apparent when both languages are mixed. Simultaneous bilinguals also show improved Executive Control efficiency, particularly in the presence of alerting and orienting cues, suggesting enhanced attentional skills for this group. We discuss these findings with respect to participant grouping and task effects, noting the importance of the language environment.
A prosodic bias, not an advantage, in bilinguals' interpretation of emotional prosody
Authors: CHAMPOUX-LARSSON MARIE-FRANCE , DYLMAN ALEXANDRA S.
Published: June 2018

A bilingual advantage has been found in prosody understanding in pre-school children. To understand this advantage better, we asked 73 children (6-8 years) to identify the emotional valence of spoken words, based on either semantics or emotional prosody (which were either consistent or discrepant with each other). Bilingual experience ranged from no to equal exposure to and use of two languages. Both age and bilingual experience predicted accurate identification of prosody, particularly for trials where the semantics were discrepant with the targeted prosody. Bilingual experience, but not age, predicted a prosodic bias, meaning that participants had more difficulty ignoring the irrelevant discrepant prosody when the task was to identify the semantics of the word. The decline of a semantic bias was predicted by age and bilingual experience together. Our results suggest that previous findings on the bilingual advantage in prosody processing may in fact be driven by a prosodic bias.
From Einstein’s Theory to Gravity’s Chirp
Authors: Taylor Joseph H.
Published: June 2018

The tortuous journey from theoretical suspicions to direct detection of gravitational waves took a hundred years and followed a crooked course. The field equations of general relativity evidently have wave-like solutions, but physical reality of these implied waves was doubted by many — including Einstein himself — for nearly fifty years. The question of physical reality was settled theoretically by the late 1950s, but for several more decades serious questions remained about what types of astrophysical systems might generate gravitational waves, and with what energies. The discovery of binary pulsar PSR B1913+16 led to dedicated development of much more accurate pulsar timing techniques, and results of these experiments motivated further theoretical work to clear up the quantitative questions about energy generation. By the late 1980s the generation of gravitational waves by the Hulse-Taylor binary pulsar was firmly established to be in quantitative agreement with general relativity. This experimental proof was almost surely a prerequisite for the funding of LIGO, the Laser Interferometer Gravitational-Wave Observatory, in 1992, which after nearly another quarter century achieved the first direct detection of gravitational waves.
X-ray Dim Isolated Neutron Stars and phase-dependent absorption features
Authors: Borghese A. , Rea N. , Zelati F. Coti
Published: June 2018

Thanks to a detailed pulse phase spectroscopy of archival XMM–Newton observations, we discovered narrow and strongly phase-dependent absorption features in the X-ray spectra of two X-ray dim isolated neutron stars (XDINSs), RX J0720.4-3125 and RX J1308.6+2127. The spectral lines show similar properties: they are detected in only 20% of the rotational cycle with an energy of ~ 740 eV and appear to be stable over the timespan covered by the observations. The strong dependence on the pulsar rotation and the narrow width suggest that the features are most likely due to proton cyclotron resonant scattering in a confined magnetic structure close to the stellar surface. The inferred magnetic field in such a loop is of the order of ~ 1014 G, higher than the surface dipolar magnetic field (~ 1 – 3.5 × 1013 G for the XDINSs).
Is anomalous scattering typical for pulsars?
Authors: Lewandowski Wojciech , Kijak Jarosław , Błaszkiewicz Leszek , Rożko Karolina , Krankowski Andrzej
Published: June 2018

Recent studies of interstellar scattering frequency evolution indicate, that for a large number of pulsars the measured scatter time to frequency scaling does not follow predictions based upon simple scattering models. The number of such deviations suggests, that what was previously known as “anomalous scattering” is actually quite normal for a large subset of the pulsar population. New observations are needed, especially at low frequencies, to study the scattering of low-DM objects. In this regard even small telescopes, such as single LOFAR stations - like PL-612 in Bałdy, near Olsztyn, Poland - can be extremely helpful.
Polarization study of the pulsars in the globular cluster 47 Tucanae
Authors: Abbate F. , Possenti A. , Tiburzi C. , van Straten W. , Barr E. , Ridolfi A. , Freire P.
Published: June 2018

The linearly polarized component of a pulsar signal at different radio frequencies can help to constrain the parallel component of the magnetic field along the line of sight. In this work we measured the polarimetric properties of the pulsars in the globular cluster 47 Tucanae and we report the Rotation Measure (RM) for 13 of them. A gradient in the RM values of the pulsars across the cluster is detected suggesting the presence of significant variations in the magnetic field across the very small angular scales associated with the lines of sight to the pulsars in 47 Tucanae. Both magnetic fields located in the globular cluster or in the Galactic disk in the direction of the cluster are taken into consideration. However, more detailed modelling of the dynamics of the cluster and deeper observations with the MeerKAT and/or the SKA1 radio telescopes are necessary to discriminate among the models.
Simultaneous Radio and X-Ray observations of Crab Pulsar
Authors: Basu A. K. , Joshi B. C. , Bhattacharya D.
Published: June 2018

Crab Pulsar (PSR B0531+21) is known to emit pulsed emission in all bands of the electromagnetic spectrum. It also emits giant radio pulses (GRPs) frequently, which are roughly a hundred to million times brighter than the normal pulses. We aim to study whether there is a significant X-ray enhancement correlated with the occurrence of GRPs, using simultaneous observations with the ASTROSAT, the Giant Meterwave Radio telescope (1300 MHz) and the Ooty Radio telescope (325 MHz). This required determination of fixed pipeline offsets between different instruments. We find the offset between ASTROSAT and GMRT to be −30.181 ± 0.095 ms and that between ASTROSAT and ORT to be −18.4 ± 0.2 ms. Our preliminary results with 1300 MHz data also show a break in pulse intensity distribution at ~ 33 Jy in the main pulse and ~ 28 Jy in the inter-pulse.
PAFINDER – Searching for FRBs and pulsars using Phased Array Feeds
Authors: Malenta Mateusz , Barr Ewan , Chippendale Aaron , Deng Xinping , George Daniel , Karuppusamy Ramesh , Keith Michael , Kramer Michael , Spitler Laura , Stappers Benjamin , Wieching Gundolf
Published: June 2018

The challenges of detecting and localising Fast Radio Bursts in real time can be met with the use of Phased Array Feeds. One such system, capable of creating up to 36 simultaneous beams, is currently being commissioned at the Effelsberg radio telescope in Germany following testing at the 64 m Parkes radio telescope. The PAFINDER (Phased Array Feed FRB Finder) pipeline will be used with this receiver to enable real–time single–pulse detection and localisation.
Magnetospheric Switching in PSR B1828–11
Authors: Stairs I. H. , Lyne A. G. , Kramer M. , Stappers B. W. , van Leeuwen J. , Tung A. , Manchester R. N. , Hobbs G. B. , Lorimer D. R. , Melatos A.
Published: June 2018

PSR B1828–11 is a young pulsar once thought to be undergoing free precession and recently found instead to be switching magnetospheric states in tandem with spin-down changes. Here we show the two extreme states of the mode-changing found for this pulsar and comment briefly on its interpretation.
Neutron star equation of state and uncertainty on the radius determination
Authors: Fortin Morgane
Published: June 2018

Simultaneous measurements of the radius and mass of neutron stars (NSs) are expected from the new generation of X-ray telescopes, potentially constraining the NS equation of state (EoS). However using ‘non-unified’ EoSs with the ones for the core and the crust not based on the same nuclear model can introduce an uncertainty on the radius as large as the precision expected from these instruments. I present two solutions to this problem: a large collection of unified EoSs and an approximate and yet precise approach that, with no need of a crust EoS, provides the relation between the NS mass and radius. I discuss correlations between the NS radius and nuclear parameters, possibly allowing to constrain the NS radius with experiments on Earth. Finally, I show that in spite of the observation of massive NSs, one can not exclude that hyperons appear at high densities in NSs due to the scarcity of the available experimental data.
Thermonuclear burst oscillations and the dense matter equation of state
Authors: Watts Anna L.
Published: June 2018

Matter in neutron star cores reaches extremely high densities, forming states of matter that cannot be generated in the laboratory. The Equation of State (EOS) of the matter links to macroscopic observables, such as mass M and radius R, via the stellar structure equations. A promising technique for measuring M and R exploits hotspots (burst oscillations) that form on the stellar surface when material accreted from a companion star undergoes a thermonuclear explosion. As the star rotates, the hotspot gives rise to a pulsation, and relativistic effects encode information about M and R into the pulse profile. However the burst oscillation mechanism remains unknown, introducing uncertainty when inferring the EOS. I review the progress that we are making towards cracking this long-standing problem, and establishing burst oscillations as a robust tool for measuring M and R. This is a major goal for future large area X-ray telescopes.
Superburst Oscillations: ocean and crustal modes excited by X-Ray bursts
Authors: Chambers Frank R. N. , Watts Anna L.
Published: June 2018

Superburst oscillations are high frequency X-ray variations observed during hours’ long superbursts on accreting neutron stars. We investigate a potential mechanism to explain these observations; a buoyant r-mode, excited in the ocean layers of the star. These modes are affected by ash composition in the ocean so are a good probe of nuclear burning processes. The phenomenon could be used in pulse profile modelling as a way of measuring neutron star mass and radius, and so the dense matter equation of state.
Millisecond pulsars at low frequencies
Authors: Bhat N. D. Ramesh , Tremblay Steven E. , Kirsten Franz
Published: June 2018

Low-frequency pulsar observations are well suited for studying propagation effects caused by the interstellar medium (ISM). This is particularly important for millisecond pulsars (MSPs) that are part of high-precision timing applications such as pulsar timing arrays (PTA), which aim to detect nanoHertz gravitational waves. MSPs in the southern hemisphere will also be the prime targets for PTAs with the South African MeerKAT, and eventually with the SKA. The development of the Murchison Widefield Array (MWA) and the Engineering Development Array (EDA) brings excellent opportunities for low-frequency studies of MSPs in the southern hemisphere. They enable observations at frequencies from 50 MHz to 300 MHz, and can be exploited for a wide range of studies relating to pulsar emission physics and probing the ISM.
Interstellar medium studies below 200 MHz: LOFAR single stations and NenuFAR
Authors: Grießmeier Jean-Mathias , Bondonneau Louis , Serylak Maciej , Theureau Gilles
Published: June 2018

International LOFAR stations, equipped with powerful backends, can be used as individual telescopes, and provide data sets complementary to those obtained with the LOFAR Core. Such “local mode” observations are particularly adapted to monitoring observations, where the advantage of having a high observing cadence (one observation per week) outweighs the reduced sensitivity of a single station when compared to the full array. With such observations, it is possible to monitor the temporal evolution of the pulsars’ behaviour via its dispersion, scattering, intensity, and profile shape. We present recent studies performed in the LOFAR low band (10-90 MHz).
Magnetic field configurations of magnetars
Authors: Fujisawa Kotaro , Yatabe Akihiro , Kisaka Shota
Published: June 2018

We evaluated ambipolar diffusion velocity in a magnetar. Previous studies concerning ambipolar diffusion ignored the presence of the crust, although a magnetar has both core and crust. We considered both core and crust and examined the influence of the crust in this study. We found that the crustal magnetic field can accelerate the ambipolar diffusion in its core.
A window into the neutron star: Modelling the cooling of accretion heated neutron star crusts
Authors: Wijngaarden Marcella J.P. , Wijnands Rudy , Ootes Laura S. , Parikh Aastha S. , Page Dany
Published: June 2018

In accreting neutron star X-ray transients, the neutron star crust can be substantially heated out of thermal equilibrium with the core during an accretion outburst. The observed subsequent cooling in quiescence (when accretion has halted) offers a unique opportunity to study the structure and thermal properties of the crust. Initially crust cooling modelling studies focussed on transient X-ray binaries with prolonged accretion outbursts (> 1 year) such that the crust would be significantly heated for the cooling to be detectable. Here we present the results of applying a theoretical model to the observed cooling curve after a short accretion outburst of only ~10 weeks. In our study we use the 2010 outburst of the transiently accreting 11 Hz X-ray pulsar in the globular cluster Terzan 5. Observationally it was found that the crust in this source was still hot more than 4 years after the end of its short accretion outburst. From our modelling we found that such a long-lived hot crust implies some unusual crustal properties such as a very low thermal conductivity (> 10 times lower than determined for the other crust cooling sources). In addition, we present our preliminary results of the modelling of the ongoing cooling of the neutron star in MXB 1659-298. This transient X-ray source went back into quiescence in March 2017 after an accretion phase of ~1.8 years. We compare our predictions for the cooling curve after this outburst with the cooling curve of the same source obtained after its previous outburst which ended in 2001.
Kinematic effects on high order spin frequency derivatives
Authors: Liu Xiao-Jin , Stappers Benjamin , Bassa Cees
Published: June 2018

The radial velocity of a pulsar induces the Doppler effect on its intrinsic spin properties. In particular, it can generate a contribution to the frequency second derivative. We estimated this effect for each of the International Pulsar Timing Array pulsars. We also assessed the possibility of measuring the frequency second derivative in the observational data.
Hard Spectral Tails in Magnetars
Authors: Wadiasingh Zorawar , Baring Matthew G. , Gonthier Peter L. , Harding Alice K.
Published: June 2018

Pulsed non-thermal quiescent emission between 10 keV and around 150 keV has been observed in ~10 magnetars. For inner magnetospheric models of such hard X-ray signals, resonant Compton upscattering of soft thermal photons from the neutron star surface is the most efficient radiative process. We present angle-dependent hard X-ray upscattering model spectra for uncooled monoenergetic relativistic electrons. The spectral cut-off energies are critically dependent on the observer viewing angles and electron Lorentz factor. We find that electrons with energies less than around 15 MeV will emit most of their radiation below 250 keV, consistent with the observed turnovers in magnetar hard X-ray tails. Moreover, electrons of higher energy still emit most of the radiation below around 1 MeV, except for quasi-equatorial emission locales for select pulses phases. Our spectral computations use new state-of-the-art, spin-dependent formalism for the QED Compton scattering cross section in strong magnetic fields.
Pulsar science at the Sardinia Radio Telescope
Authors: Perrodin D. , Burgay M. , Corongiu A. , Pilia M. , Possenti A. , Iacolina M. N. , Egron E. , Ridolfi A. , Tiburzi C. , Casu S. , Concu R. , Melis A. , Pellizzoni A. , Trois A.
Published: June 2018

The Sardinia Radio Telescope (SRT) is a modern, fully-steerable 64-m dish located in San Basilio, Sardinia (Italy). It is characterized by an active surface that allows it to cover a wide range of radio frequencies (300 MHz to 100 GHz). During SRT’s commissioning phase, we installed the hardware and software needed for pulsar observations. Since then, SRT has taken part in Large European Array for Pulsars and European Pulsar Timing Array observations for the purpose of gravitational wave detection. We have installed a new S-band receiver that will allow us to search for pulsars in the Galactic Center. We also plan to combine our efforts to search for Extraterrestrial Intelligence (SETI) with the search for pulsars and Fast Radio Bursts.
The eclipses of the black widow pulsar J1810+1744 at low radio frequencies
Authors: Polzin Elliott J. , Breton Rene P. , Stappers Ben W. ,   the LOFAR PWG
Published: June 2018

Here we present a study of the radio frequency eclipses of the black widow pulsar J1810+1744 at low frequencies, where we are most sensitive to small deviations in the effects of material along the line of sight. Utilising the simultaneous dual beamforming and interferometric (imaging) mode of LOFAR High Band Antenna, pulsar flux variations throughout the orbit are compared for the two observing techniques to test for the presence of scattering and absorption at eclipse orbital phases. Dispersion measure and scattering variations are used as a sensitive probe into outermost edges of the eclipsing material surrounding the companion star. We find the eclipsing medium to be variable on timescales shorter than the 3.6 hr orbital period, and propose cyclotron-synchrotron absorption as the most likely primary eclipse mechanism.
PSR J1913+1102: a pulsar in a highly asymmetric and relativistic double neutron star system
Authors: Ferdman Robert D. ,   the PALFA collaboration
Published: June 2018

PSR J1913+1102 is a double neutron star system (DNS) discovered in the Pulsar Arecibo L-band Feed Array survey. We have now very precisely measured the rate of advance of periastron for the system and the Einstein delay. From general relativity, this results in precise mass measurements: 1.65 ± 0.05 and 1.24 ± 0.05 M⊙ for the pulsar and neutron-star companion, respectively. This makes PSR J1913+1102 both the most massive double neutron star system known, and the most asymmetric in mass among compact DNS binaries. This asymmetry will allow for stringent limits on the effects of dipolar gravitational-wave radiation, predicted by alternative theories of gravity, as well as insight into heavy-element production from the eventual merger of this system and others like it. Further observations will also tighten constraints on formation and evolution models; this is crucial for understanding the DNS population, for which there are relatively few mass measurements.
Intermittency and Anisotropy in the Ionized Interstellar Medium
Authors: Rickett Barney
Published: June 2018

The discovery of pulsars was closely followed by the discovery of dispersion and scattering in the interstellar plasma (ionized interstellar medium - IISM). The rich phenomena of scattering and scintillation have since been successfully modelled as propagation through a statistically uniform plasma turbulence with an isotropic Kolmogorov spectrum of density. However, this enticingly simple model fails to explain the many recent observations, that show anisotropic scattering from highly localized regions of the IISM often referred to as phase screens. I summarize the recent evidence from pulsars and also from very compact AGN sources, which can exhibit rapid scintillation and occasionally ESEs. The unknown astrophysical origin of these phenomena includes thin current sheets, the diffuse remnants of old supernova shells, and plasma filaments surrounding ubiquitous molecular clumps near young hot stars.
The Einstein@Home Survey for Gamma-ray Pulsars
Authors: Clark Colin J. , Wu Jason , Pletsch Holger J. , Guillemot Lucas
Published: June 2018

Since the launch of the Fermi Gamma-ray Space Telescope in 2008, the onboard Large Area Telescope (LAT) has detected gamma-ray pulsations from more than 200 pulsars. A large fraction of these remain undetected in radio observations, and could only be found by directly searching the LAT data for pulsations. However, the sensitivity of such “blind” searches is limited by the sparse photon data and vast computational requirements. In this contribution we present the latest large-scale blind-search survey for gamma-ray pulsars, which ran on the distributed volunteer computing system, Einstein@Home, and discovered 19 new gamma-ray pulsars. We explain how recent improvements to search techniques and LAT data reconstruction have boosted the sensitivity of blind searches, and present highlights from the survey’s discoveries. These include: two glitching pulsars; the youngest known radio-quiet gamma-ray pulsar; and two isolated millisecond pulsars (MSPs), one of which is the only known radio-quiet rotationally powered MSP.
Gravity Tests with Pulsars
Authors: Kramer Michael
Published: June 2018

Fifty years of pulsars also mean fifty years of using them as tools to probe other phenomena and physics. One prominent example is the usage of pulsars to test theories of gravity. Probing the quasi-stationary strong-field regime, pulsars allow high precision tests that will maintain their importance even in the era of gravitation wave observations with ground-based detectors. This contribution summarise the methods and status of the field and provides a brief outlook into the future.
Tilted Pulsar Beams
Authors: Wright Geoff , Weltevrede Patrick
Published: June 2018

In 1975 the carousel model was proposed by Ruderman & Sutherland to explain the beautiful phenomenon of drifting subpulses. However the simultaneous appearance of subpulse bands which drift in opposing directions - a feature now found in two pulsars - is difficult to reconcile with this model, both geometrically and physically. Here we propose a geometric resolution of this problem which also may shed light on a range of previously baffling phenomena. The model places significant constraints on the underlying physics of pulsar emission.
Long-term observations of pulsars in the globular clusters 47 Tucanae and M15
Authors: Ridolfi A. , Freire P. C. C. , Kramer M. , Bassa C. G. , Camilo F. , D’Amico N. , Desvignes G. , Heinke C. O. , Jordan C. , Lorimer D. R. , Lyne A. , Manchester R. N. , Pan Z. , Sarkissian J. , Torne P. , van den Berg M. , Venkataraman A. , Wex N.
Published: June 2018

Multi-decade observing campaigns of the globular clusters 47 Tucanae and M15 have led to an outstanding number of discoveries. Here, we report on the latest results of the long-term observations of the pulsars in these two clusters. For most of the pulsars in 47 Tucanae we have measured, among other things, their higher-order spin period derivatives, which have in turn provided stringent constraints on the physical parameters of the cluster, such as its distance and gravitational potential. For M15, we have studied the relativistic spin precession effect in PSR B2127+11C. We have used full-Stokes observations to model the precession effect, and to constrain the system geometry. We find that the visible beam of the pulsar is swiftly moving away from our line of sight and may very soon become undetectable. On the other hand, we expect to see the opposite emission beam sometime between 2041 and 2053.
Evidence for an intermediate-mass black hole in NGC 6624
Authors: Perera B. B. P. , Stappers B. W. , Lyne A. G. , Bassa C. G. , Cognard I. , Guillemot L. , Kramer M. , Theureau G. , Desvignes G.
Published: June 2018

PSR B1820–30A is located in the globular cluster NGC 6624 and has the smallest projected distance to the centre of any globular cluster in the sky plane. We observe this millisecond pulsar over more than 25 years and obtain higher-order rotational frequency time derivative measurements through high-precision timing. Modelling these higher-order derivatives as being due to orbital motion, we find that the pulsar is in either a low-eccentricity smaller orbit with a low mass companion or a high-eccentricity larger orbit with a massive companion. The cluster mass properties and the observed properties of other nearby sources indicate that the high-eccentricity solution is more probably. This reveals that the pulsar is orbiting around an intermediate-mass black hole (IMBH) of mass >7500 M⊙ located at the cluster centre. This contribution is based on previous work published in MNRAS 471, 1258 (2017).
The Multiple Outputs of Energetic Pulsars
Authors: Romani Roger W.
Published: June 2018

This talk commented on our progress in understanding high Ė pulsar output, with the photon power dominated by GeV radiation and the total power dominated by the e±/B wind. We are increasingly appreciating the anisotropy in these outflows, with high energy pulsar beaming probed by the distribution of γ-ray pulse profiles and wind anisotropy mapped by synchrotron images of PWNe. Possible hemispheric asymmetry and the prospects for additional probes of pulsar spindown, particularly from compact binaries in the black widow class, are briefly mentioned.
Pulsar Glitches
Authors: Manchester R. N.
Published: June 2018

The first known pulsar glitch was discovered in the Vela pulsar at both Parkes and Goldstone in March 1969. Since then the number of known glitches has grown enormously, with more than 520 glitches now known in more than 180 pulsars. Details of glitch parameters and post-glitch recoveries are described and some implications for the physics of neutron stars are discussed.
The first binary pulsars and what they told us about binary evolution
Authors: Bhattacharya Dipankar
Published: June 2018

The first few binary pulsars revealed the richness of evolution possible in binary systems containing neutron stars. Products of different evolutionary routes, in high and low mass binaries, as well as examples of evolution affected by the pulsar wind were among the first ten objects discovered. This article presents a historical review of the impact of binary pulsars on the early development of ideas regarding the evolution of neutron stars in binary systems.
The effect of the Solar wind on low-frequency observations of pulsars
Authors: Tiburzi C. , Verbiest J. P. W.
Published: June 2018

We operate the six German stations of the LOw Frequency ARray as standalone telescopes to observe more than 100 pulsars every week. To date, we have collected almost four years of high-quality data at an unprecedented weekly cadence. This allows us to perform a wide variety of analyses aimed at characterising the magnetoionic plasma crossed by pulsar radiation. In particular, our studies are focused on electron density variations in the interstellar and interplanetary media, the Galactic and interplanetary magnetic field, scintillation, and extreme scattering events. Here we report the first results from our Solar wind monitoring campaign.
On sub-pulse drift related profile mode-changes studied with a new technique
Authors: Joshi Bhal Chandra
Published: June 2018

Sub-pulse drift related profile mode-changes provide a useful probe of pulsar radio emission. Measurements on modal profiles of PSRs B0031–07, J1822–2256 and B2319+60 are presented for different drift modes in this communication. The width of profile increases with the drift rate, while no such trend is seen for the pulsed flux density for all these pulsars. A brief discussion of implications for models is presented.
The Noisy Ageing of Slow Pulsars: New Thoughts on the Evolution of the Pulsar Population
Authors: Karastergiou Aris , Johnston Simon
Published: June 2018

Over the last decade or so, it has become clear that pulsars exhibit sudden and significant changes in their spin properties. At the same time, a better understanding of the geometry of young and older pulsars, is providing clues about the long-term evolution of the magnetic inclination angle. In this talk, we present a simple simulation of the pulsar population that takes into account current observational facts. We show how, with very few assumptions, the observed P-Ṗ diagram can be reproduced for a synthesized population. The implications are interesting and testable.
Verifying the low frequency pulsar polarimetry of the MWA
Authors: Tremblay Steven E. , Xue Mengyao , Bhat N. D. Ramesh , Tiburzi Caterina
Published: June 2018

Studying the polarised properties of pulsars has a rich history giving unique geometric information about pulsars as well as testing the theories of pulsar emission physics. Performing such studies with the MWA has the attraction that the percentage of linear polarisation of many pulsars increases as the observing frequency decreases. Here we discuss the strategies being employed to verify the polarimetric response of the MWA’s high time resolution data.
Single Pulses and the Plasma-physical Processes of Pulsar Radio Emission
Authors: Rankin Joanna M.
Published: June 2018

Pulsars were discovered on the basis of their individual pulses, first by Jocelyn Bell and then by many others. This was chart-recorder science as computers were not yet in routine use. Single pulses carry direct information about the emission process as revealed in the detailed properties of their polarization characteristics. Early analyses of single pulses proved so dizzyingly complex that attention shifted to study of average profiles. This is turn led to models of pulsar emission beams—in particular the core/double-cone model—which now provides a foundation for understanding single-pulse sequences. We mention some of the 21stC single-pulse surveys and conclude with a brief discussion of our own recent analyses leading to the identification of the pulsar radio-emission mechanism of both slow and millsecond pulsars.
LOFT-e: Localisation Of Fast Transients with e-MERLIN
Authors: Walker C. R. H. , Breton R. P. , Harrison P. A. , Holloway A. , Keith M. J. , Kramer M. , Malenta M. , Mickaliger M. B. , Roy J. , Scragg T. W. , Stappers B. W.
Published: June 2018

The majority of fast radio bursts (FRBs) are poorly localised, hindering their potential scientific yield as galactic, intergalactic, and cosmological probes. LOFT-e, a digital backend for the U.K.’s e-MERLIN seven-telescope interferometer will provide commensal search and real-time detection of FRBs, taking full advantage of its field of view (FoV), sensitivity, and observation time. Upon burst detection, LOFT-e will store raw data offline, enabling the sub-arcsecond localisation provided by e-MERLIN and expanding the pool of localised FRBs. The high-time resolution backend will additionally introduce pulsar observing capabilities to e-MERLIN.
Pulsar polarization: the view from the southern hemisphere
Authors: Johnston Simon
Published: June 2018

Pulsar polarization has been a fruitful area of study since the first discovery of pulsars 50 years ago. Polarization gives information on the geometry of the star, the location of the radio emission in the magnetosphere, the physics behind the radio emission mechanism and a plethora of phenomenology. Here, I will restrict myself to a brief outline of recent work in pulsar polarization using observations taken with the Parkes radio telescope over the past decade.
High Time Resolution Astronomical Polarimetry with GASP
Authors: O’Connor Eoin G.P. , Shearer Andrew , Gouiffes Christian , Laurent Philippe
Published: June 2018

The Galway Astronomical Stokes Polarimeter (GASP) is a high time resolution, full-Stokes imaging polarimeter which utilises a Fresnel rhomb prism as a beam-splitter and quarter wave retarder. The ability to perform optical photometry and polarimetry at high frame rates enables more detailed studies of a multitude of compact objects including; optical pulsars, magnetars and Active Galactic Nuclei (AGN). We present a brief discussion of the instruments’ current capabilities and hardware design. GASP is currently configured with two Electron Multiplying Charge-Coupled Devices (EMCCDs), which offer sub-millisecond frame readout speeds over a defined region of interest on the sensor. We will report results from an observational campaign at the William Herschel Telescope (WHT) in December, 2015. During this campaign GASP was used to study the Crab Pulsar, V404 Cygni and polarisation standards. As a subset of our analysis we have identified a significant contribution from the Interstellar Medium (ISM) and the interaction of a varying polarised source with the ISM, the subsequent conversion of linearly polarised light to circular, and its dependence on the angle of the source emission electric field orientation. Further to the presentation of results we will discuss future observational work, which is planned for September 2017 and subsequent improvements to increase the temporal resolution of the detectors.
Pulsar science with the CHIME telescope
Authors: Ng Cherry
Published: June 2018

The CHIME telescope (the Canadian Hydrogen Intensity Mapping Experiment) recently built in Penticton, Canada, is currently being commissioned. Originally designed as a cosmology experiment, it was soon recognized that CHIME has the potential to simultaneously serve as an incredibly useful radio telescope for pulsar science. CHIME operates across a wide bandwidth of 400–800 MHz and will have a collecting area and sensitivity comparable to that of the 100-m class radio telescopes. CHIME has a huge field of view of ~250 square degrees. It will be capable of observing 10 pulsars simultaneously, 24-hours per day, every day, while still accomplishing its missions to study Baryon Acoustic Oscillations and Fast Radio Bursts. It will carry out daily monitoring of roughly half of all pulsars in the northern hemisphere, including all NANOGrav pulsars employed in the Pulsar Timing Array project. It will cycle through all pulsars in the northern hemisphere with a range of cadence of no more than 10 days.
Core/Double-Cone Emission-Beam Structure in a Millisecond Pulsar
Authors: Rankin Joanna M.
Published: June 2018

Slow pulsars show a great deal of qualitative and quantitative regularity in the structure of their radio emission beams as described by the core/double-cone model; however, millisecond pulsars (MSPs) have shown little. It is thus arresting to encounter a 2.7-s MSP with what appears to be a double-cone/core profile—and even more so to find that the arrangement of the cones around the core suggest aberration/retardation emission heights that are very reasonable. This and several other pulsars then represent rare opportunities for analysis and raise questions about why a few MSPs show such orderly beam structure while so many do not.
Strong field tests of gravity with PSR J1141–6545
Authors: Krishnan V. Venkatraman , van Straten W. , Rosado P. A. , Bailes M. , Keane E. F. , Bhat R. , Flynn C.
Published: June 2018

The initial results from timing observations of PSR J1141–6545, a relativistic pulsar-white dwarf binary system, are presented. Predictions from the timing baseline hint at the most stringent test of gravity by an asymmetric binary yet. The timing precision has been hindered by the dramatic variations of the pulse profile due to geodetic precession, a pulsar glitch and red timing noise. Methods to overcome such timing irregularities are briefly presented along with preliminary results from the test of the General Theory of Relativity (GR) from this pulsar.
Probing neutron star interiors with pulsar glitches
Authors: Haskell Brynmor
Published: June 2018

Pulsar glitches are thought to be probes of the superfluid interior of neutron stars. These sudden jumps in frequency observed in many pulsars are generally assumed to be the macroscopic manifestation of superfluid vortex motion on a microscopic scale. Resolving and modelling such phenomena on the scale of a neutron star is, however, a challenging problem which still remains open, fifty years after the discovery of pulsars. In this article I will review recent theoretical progress, both on the microscopic level and on the macroscopic level, and discuss which constraints on the models can be provided by observations.