Pulsar observations at millimetre wavelengths

Detecting and studying pulsars above a few GHz in the radio band is challenging due to the typical faintness of pulsar radio emission, their steep spectra, and the lack of observatories with sufficient sensitivity operating at high frequency ranges. Despite the difficulty, the observations of pulsars at high radio frequencies are valuable because they can help us to understand the radio emission process, complete a census of the Galactic pulsar population, and possibly discover the elusive population in the Galactic Centre, where low-frequency observations have problems due to the strong scattering. During the decades of the 1990s and 2000s, the availability of sensitive instrumentation allowed for the detection of a small sample of pulsars above 10$\,$GHz, and for the first time in the millimetre band. Recently, new attempts between 3 and 1$\,$mm ($\approx$86$-$300$\,$GHz) have resulted in the detections of a pulsar and a magnetar up to the highest radio frequencies to date, reaching 291$\,$GHz (1.03$\,$mm). The efforts continue, and the advent of new or upgraded millimetre facilities like the IRAM 30-m, NOEMA, the LMT, and ALMA, warrants a new era of high-sensitivity millimetre pulsar astronomy in the upcoming years.Comment: 4 pages. Published in the Proceedings of the IAU Symposium 337 Pulsar Astrophysics - The Next 50 Year

Asian American Women Leaders in the Pacific Coast: Their Pathway to Presidency in Two-Year Institutions

The field of education continues to see an underrepresentation of women as presidents of colleges and universities especially Asian Americans in general. In comparison with other racial and ethnic groups, Asian Americans are the only group not equally represented in high executive positions such as the presidential. In addition, women, including Asian American women, continue to hold, disproportionately to men, fewer leadership positions in the workplace of today. It was the intent of this qualitative study to gain an understanding the reasons for the slow progress of Asian Americans in obtaining presidential positions in higher education with the focus on women. This study explored the presidential selection process, career and leadership experiences of five Asian American women college presidents. The study utilized the conceptual framework of the glass ceiling. Interviews were transcribed and analyzed and the findings grouped into themes. As being behind the underrepresentation of Asian women in the college presidency, the participants identified multiple factors, as well the general persistence of discrimination and gender influences, gender inequity, and struggles for all women to maintain a work/life balance; and they suggested valuable strategies for aspiring Asian American college presidents to obtain to overcome barriers they face personally and overall to reverse the trend. The study found that conscious intervention is required in order to address the paucity of women, particularly Asian (and minority) college presidents. Institutions must make a concerted effort to identify and recruit future leaders that better reflect the communities that they serve. Pathways to the college presidency must be reexamined and alternative backgrounds considered. In particular, the role of search committee and board members in the selection process needs to be investigated and reworked. The position of college president itself needs reconsideration as does the persistent perception that it is a male leader who best fulfills its responsibilities. This false notion needs to be undone by selecting new leaders (female or male, minority or not) with an emphasis in the search processes instead on the qualities of the best fit with the institution\u27s demographic, on valuing people, on sharing credit, on honing the leader/follower relationship, and on integrating one\u27s personal beliefs and values into the role of being a college president

Exploring Radio Pulsars With New Technologies

Pulsars are rapidly-rotating, highly-magnetized compact neutron stars. Their strong gravitational and magnetic fields, together with the stability of their rotations and the precision with which we can measure them using radio telescopes make pulsars unique laboratories for a wide variety of physical experiments. This thesis presents an investigation of the application of new receiver technologies and observing techniques at different radio wavelengths to the search for and study of pulsars. Discovering new pulsars always expands our capabilities to do new science. In general, the most exciting pulsars are those in binary systems because of their potential in high-precision tests of General Relativity and other gravity theories, and for constraining the Equation-of-State of ultra-dense matter. I present a search for pulsars in the Galactic Centre, where the probabilities of finding pulsar binaries, including the long-sought pulsar-black hole system, are high. The data were taken with the Effelsberg 100-m radio telescope and used high radio frequencies between 4.85 and 18.95 GHz to partially overcome the strong scattering in the direction to the centre of the Galaxy. With approximately 50 per cent of the results reviewed, no new pulsars have been discovered. We carried out a study of the sensitivity limits of the survey, finding that our sensitivity to Galactic Centre pulsars is highly reduced by the contributions to the total system noise of the Galactic Centre background and the atmosphere. We conclude that the paucity of detections in this and perhaps also previous similar surveys is likely due to insufficient sensitivity, and not a lack of pulsars in the region. In March 2013, a radio magnetar, one of the rarest types of pulsars, became suddenly visible from the Galactic Centre. I led two multifrequency observing campaigns on this source, SGR J1745-2900, in order to study its radio emission properties. Four different observatories were involved (including simultaneous observations): the Nançay 94-m equivalent, the Effelsberg 100-m, the IRAM 30-m, and the APEX 12-m radio telescopes, allowing us to cover a frequency range from 2.54 to 472 GHz. The observations at the short millimetre range made use of new broad-band instrumentation never before used for pulsar observations. These observations resulted in the detection of SGR J1745-2900 from 2.54 to 291 GHz, providing measurements of its variable flux density, its also-varying spectrum, and evidence for polarized millimetre emission. The detections above 144 GHz are the highest radio frequency detections of pulsed emission from neutron stars to date, results that set new constraints on the still poorly-understood radio emission mechanism of pulsars. Since the study of the properties of pulsar emission at very high radio frequencies is relevant for understanding the radio emission process, further observations of a sample of six normal pulsars between 87 and 154 GHz were carried out using the IRAM 30-m. The initial results of this ongoing project include the detections of PSR B0355+54 up to 138 GHz, together with flux density measurements. For the other five pulsars, no obvious detections were achieved. Above 87 GHz, our detections of PSR B0355+54 are the highest-frequency detections of emission from a normal pulsar in the radio band, showing that normal pulsars continue emitting in the short millimetre regime. We found no evidence of a flattening or turn-up in the spectrum, a feature that could provide information about the emission mechanism. The intensity of this pulsar apparently decreases at and above 87 GHz, but our results suffer from uncertainties in the calibration and the possible intrinsic intensity variability of the pulsar. Forthcoming precise calibration information about the instrument will allow us to revisit the data providing stronger conclusions on the the nature of PSR B0355+54's apparent varying intensity at the millimetre wavelengths. In addition to the scientific exploitation of the these four telescopes, I investigated technical aspects of two next-generation radio receivers planned for the the Effelsberg 100-m: the new Ultra-Broad-Band receiver (UBB), and the future Phased Array Feed (PAF). The tests for the UBB included the investigation of its optimum focusing set-up and its frequency-dependent system noise. We found the optimum focus to be that which optimized the gain at the highest frequencies of its operating band. We have also shown that the sensitivity of the UBB was significantly lower when the receiver is installed at the telescope (by a factor ~3) in comparison to measurements taken in the laboratory. Our investigation points to strong Radio Frequency Interference (RFI) as the cause of this sensitivity deficit. I also designed and carried out the first scientific experiment with the UBB during its commissioning: a search for pulsars in detected gamma-ray sources with the Fermi Large Area Telescope (LAT) with no associated counterparts. No new radio pulsars were discovered in this survey, but the data analysis demonstrated that large parts of the observing frequency range (~50-80 per cent) were unusable due to persistent RFI. We also showed that the strong RFI in the local environment made the receiver enter often into saturation. For the PAF, our tests at Effelsberg on a sample element of the future Checkerboard PAF MkII array confirmed that the front-end should be able to operate at Effelsberg without a persistent saturation by RFI. Overall, the results confirm that these new receivers can be used in electromagnetically-polluted areas, but require careful designs of the electronics in order to strongly suppress those frequency ranges particularly polluted by man-made radio signals

Re-estructuración de los sistemas metropolitanos hacia modelos policéntricos?: bipolaridad o sistema policéntrico equipotencial: un análisis para la Región Metropolitana de Barcelona

Esta comunicación forma parte del trabajo de investigación pre-doctoral realizado, cuyo objetivo era poner las bases para la actual investigación doctoral. Dicha investigación realizada se resume en: el funcionamiento actual de los sistemes urbanos en los últimos decenios se ha ido alejando de forma progresiva de la estructura urbana monocéntrica desarrollada a partir de los trabajos de Von Thünen , Christaller, Alonso, Mills y Muth entre otros, hacia un nuevo paradigma de estructura urbana basado en una progresiva aparición y consolidación de sistemas complejos, en parte dispersos y en parte policéntricos; donde este último, el policéntrico, se ha ido erigiendo como el modelo urbano más deseado en la medida que se propugna como objetivo normativo por la Pespectiva de Desarrollo Espacial Europea por ser considerado como el modelo de estructura urbana que afavorece más claramente el refuerzo de la competividad y de la cohesión territorial, es decir sistemas metropolitanos más eficientes y sostenibles.Peer Reviewe

Modelling the evolution of the Guadalquivir foreland basin (South Spain).

Previous quantitative studies dealing with the origin of foreland basins have focused primarily either on the rheological basis of the lithosphere mechanical response or on the relationship between orogenic loading and sediment geometry. To link the evolution of the Guadalquivir foreland basin (South Iberia) with the thermomechanical stratification of the Iberian lithosphere, we combine quantitative approaches to deep and shallow processes: thrust loading, lithospheric flexure, thickness changes of the crust and the lithospheric mantle, and surface mass transport. A planform flexural analysis of the present-day load distribution shows that basement subsidence is related not only to upper crustal thrusting but also to a deep-seated additional load. On the basis of the observed gravity and geoid fields, we propose this additional load to be related to a lithospheric mantle thickening larger than the coeval crustal thickening. Further modeling of the evolution of a basin cross section reveals that the architecture of the sedimentary basin is additionally related to the lithosphere rheological response. The quantitative study of the evolution of basement faulting and the forebulge uplift of Sierra Morena leads us to conclude that viscous stress relaxation and/or plastic yielding within the lithosphere are key processes to explain the flexural evolution of the basin

Multi-wavelength, Multi-Messenger Pulsar Science in the SKA Era

The Square Kilometre Array (SKA) is an integral part of the next-generation observatories that will survey the Universe across the electromagnetic spectrum, and beyond, revolutionizing our view of fundamental physics, astrophysics and cosmology. Owing to their extreme nature and clock-like properties, pulsars discovered and monitored by SKA will enable a broad range of scientific endeavour and play a key role in this quest. This chapter summarizes the pulsar-related science goals that will be reached with coordinated efforts among SKA and other next-generation astronomical facilities.Comment: 14 pages, 1 figure, to be published in: "Advancing Astrophysics with the Square Kilometre Array", Proceedings of Science, PoS(AASKA14)15

RANITIDINE CONTROLLED RELEASE ANTI-REFLUX SUSPENSION FOR GASTRO-OESOPHAGEAL REFLUX DISEASE AND IT’S IN VITRO EVALUATION

Objective: The aim of this work was to develop triple action controlled release anti-reflux suspension of ranitidine and its in-vitro evaluation of anti-reflux and controlled release properties. Methods: The formulation was optimized using sodium alginate as a gelling agent along with calcium carbonate, sodium bicarbonate, magnesium hydroxide, aluminium hydroxide as alkalizing agents and colloidal microcrystalline cellulose (MCC) as a suspending agent at various concentrations and arrived at an optimized formulation for its best quality attributes. To avoid initial release in water before administration, ranitidine coated MCC sphere was incorporated into powder formulation and subjected to in vitro characteristics like raft strength, acid neutralizing capacity, pH, viscosity and dissolution study. The obtained results were assessed using Minitab 17 statistical software to conclude the study design. Results: Formulation containing 300 mg of ranitidine along with 750 mg alginate has shown better anti-reflux characteristics like raft strength 18±2g, acid neutralizing capacity 17±1 mEq compared to other formulations. This formulation has also shows zero-order controlled release in the simulated gastric fluid (SGF) up to 10 h compared to the formulation without alginate. Further, to this optimized formulation has shown negligible change in the assay of ranitidine even after 3 mo at 40 °C temperature and 75% RH. Conclusion: The developed stable sustained release powder for suspension has the combined therapeutic efficacy as an antacid and anti-reflux drug suitable for the management and treatment of gastro-oesophageal reflux disease (GERD) unlike the existing drugs possessing only reflux resistance action

A Review of the current knowledge of the crustal and lithospheric structure of the Valencia Trough Basin

In this paper, we review the current geophysical knowledge of the Valencia Trough Basin, and the surrounding areas. For this purpose, we summarize the most significant regional geophysical datasets acquired since the seventies to investigate the trough (seismic, gravity, geoid and heat flow data). We then focus on the discussion regarding the geometry and physical properties of the present day crustal and lithospheric structure derived from seismic images, as well as combined potential field modelling and their relationships with the Alpine geodynamic evolution of the Valencia Trough. Finally, we discuss the differences in the results regarding the geometry of the lithosphere-asthenosphere boundary obtained by different modelling approaches and the features that, in our view, require further investigation to unravel the true nature of the Valencia Trough, including what could have caused the differences between the crustal structure observed in the SW region compared to the NE region, the asymmetric style of thinning across the trough; the origin of the changes in the lower crustal reflectivity across the basin; the fabric of the uppermost mantle, characterized by anomalously low P-wave velocities; and the physical properties of the lithosphere mantle (density, Pwaves velocity, thermal conductivity, temperature distribution, mineralogical composition, etc.)

Long-Term Observations Of The Pulsars In 47 Tucanae – I. A Study Of Four Elusive Binary Systems

For the past couple of decades, the Parkes radio telescope has been regularly observing the millisecond pulsars in 47 Tucanae (47 Tuc). This long-term timing program was designed to address a wide range of scientific issues related to these pulsars and the globular cluster where they are located. In this paper, the first of a series, we address one of these objectives: the characterization of four previously known binary pulsars for which no precise orbital parameters were known, namely 47 Tuc P, V, W and X (pulsars 47 Tuc R and Y are discussed elsewhere). We determined the previously unknown orbital parameters of 47 Tuc V and X and greatly improved those of 47 Tuc P and W. For pulsars W and X we obtained, for the first time, full coherent timing solutions across the whole data span, which allowed a much more detailed characterization of these systems. 47 Tuc W, a well-known tight eclipsing binary pulsar, exhibits a large orbital period variability, as expected for a system of its class. 47 Tuc X turns out to be in a wide, extremely circular, 10.9-day long binary orbit and its position is ~3.8 arcmin away from the cluster center, more than three times the distance of any other pulsar in 47 Tuc. These characteristics make 47 Tuc X a very different object with respect to the other pulsars of the cluster