Unraveling the drift behaviour of the remarkable pulsar PSR B0826-34

We present new results from high sensitivity GMRT observations of PSR B0826-34. We provide a model to explain the observed subpulse drift properties of this pulsar, including the apparent reversals of the drift direction. In this model, PSR B0826-34 is close to being an aligned rotator. We solve for the emission geometry of this pulsar and show that the angle between the rotation and the magnetic axes is less than 5 deg. We see evidence for as many as 6 to 7 drifting bands in the main pulse at 318 MHz, which are part of a circulating system of about 15 spark-associated subpulse emission beams. We provide quantitative treatments of the aliasing problem and various effects of geometry. The observed drift rate is an aliased version of the true drift rate, such that a subpulse drifts to the location of the adjacent subpulse (or a multiple thereof) in about one pulsar period. We show that small variations, of the order of 3-8%, in the mean drift rate are then enough to explain the apparent reversals of drift direction. We find the mean circulation time of the drift pattern to be significantly longer than the predictions of the original RS75 model and propose an explanation for this, based on modified models with temperature regulated partial ion flow in the polar vacuum gap. From the variation of the mean subpulse separation across the main pulse window, we show that the spark pattern is not centred around the dipole axis, but around a point much closer (within a degree or so) to the rotation axis -- we discuss the implication of this.Comment: 23 pages (including 9 figure). Submitted to Astronomy and Astrophysics on November 11, 200

Energy harvesting from transverse galloping

Some elastic bluff bodies under the action of a fluid flow can experience transverse galloping and lose stability if the flow velocity exceeds a critical value. For flow velocities higher than this critical value, there is an energy transfer from the flow to the body and the body develops an oscillatory motion. Usually, it is considered as an undesirable effect for civil or marine structures but here we will show that if the vibration is substantial, it can be used to extract useful energy from the surrounding flow. This paper explores analytically the potential use of transverse galloping in order to obtain energy. To this end, transverse galloping is described by a one-degree-of-freedom model where fluid forces obey the quasi-steady hypothesis. The influence of cross-section geometry and mechanical properties in the energy conversion factor is investigated

Investment rigidity and policy measures

This paper assesses the impacts of decoupled government transfers on production decisions of a sample of Kansas farms observed from 1996 to 2001. Our model allows for risk, risk attitudes and the intertemporal investment decisions. We also allow for different adjustments of the decision variables depending on the predominant economic conditions. The theoretical model is estimated using the threshold regression methods proposed by Hansen (1999). Threshold effects are allowed to characterize the behavior of output supply and quasi-fixed and variable input demand.. The econometric results support the existence of three regimes characterized by different economic behavior. Our analysis suggests that in a dynamic setting with risk and non-risk neutral economic agents, decoupled transfers can have a powerful influence on decisions taken by economic agents. The dynamics of the stock of capital cause this influence to grow over time.Investment, Decoupling, Threshold Behaviour, Farm Management, Risk and Uncertainty,

Design of an oximeter based on LED-LED configuration and FPGA technology

sensor

The volume densities of giant molecular clouds in M83

Using observed GALEX far-ultraviolet (FUV) fluxes and VLA images of the 21-cm HI column densities, along with estimates of the local dust abundances, we measure the volume densities of a sample of actively star-forming giant molecular clouds (GMCs) in the nearby spiral galaxy M83 on a typical resolution scale of 170 pc. Our approach is based on an equilibrium model for the cycle of molecular hydrogen formation on dust grains and photodissociation under the influence of the FUV radiation on the cloud surfaces of GMCs. We find a range of total volume densities on the surface of GMCs in M83, namely 0.1 - 400 cm-3 inside R25, 0.5 - 50 cm-3 outside R25 . Our data include a number of GMCs in the HI ring surrounding this galaxy. Finally, we discuss the effects of observational selection, which may bias our results.Comment: 9 pages, 11 figure

Analysis and Prediction of Energy Production in Concentrating Photovoltaic (CPV) Installations

A method for the prediction of Energy Production (EP) in Concentrating Photovoltaic (CPV) installations is examined in this study. It presents a new method that predicts EP by using Global Horizontal Irradiation (GHI) and the Photovoltaic Geographical Information System (PVGIS) database, instead of Direct Normal Irradiation (DNI) data, which are rarely recorded at most locations. EP at four Spanish CPV installations is analyzed: two are based on silicon solar cells and the other two on multi-junction III-V solar cells. The real EP is compared with the predicted EP. Two methods for EP prediction are presented. In the first preliminary method, a monthly Performance Ratio (PR) is used as an arbitrary constant value (75%) and an estimation of the DNI. The DNI estimation is obtained from GHI measurements and the PVGIS database. In the second method, a lineal model is proposed for the first time in this paper to obtain the predicted EP from the estimated DNI. This lineal model is the regression line that correlates the real monthly EP and the estimated DNI in 2009. This new method implies that the monthly PR is variable. Using the new method, the difference between the predicted and the real EP values is less than 2% for the annual EP and is in the range of 5.6%–16.1% for the monthly EP. The method that uses the variable monthly PR allows the prediction of the EP with reasonable accuracy. It is therefore possible to predict the CPV EP for any location, using only widely available GHI data and the PVGIS database

Testing the transferability of a coarse-grained model to intrinsically disordered proteins

The intermediate-resolution coarse-grained protein model PLUM [T. Bereau and M. Deserno, J. Chem. Phys., 2009, 130, 235106] is used to simulate small systems of intrinsically disordered proteins involved in biomineralisation. With minor adjustments to reduce bias toward stable secondary structure, the model generates conformational ensembles conforming to structural predictions from atomistic simulation. Without additional structural information as input, the model distinguishes regions of the chain by predicted degree of disorder, manifestation of structure, and involvement in chain dimerisation. The model is also able to distinguish dimerisation behaviour between one intrinsically disordered peptide and a closely related mutant. We contrast this against the poor ability of PLUM to model the S1 quartz-binding peptide

Exploring the Role of Cities in Electrifying Passenger Transportation

Key Takeaways1. The electrification of passenger vehicles should be one part of a city’s transportation plan. Shifting from internal combustion engine vehicles to plug-in electric vehicles (PEVs) can improve urban air quality, reduce greenhouse gas emissions, and reduce energy consumption.2. Recent studies show that electric vehicle awareness is low even in mature markets; cities should promote electric vehicles to residents by leveraging existing promotional campaigns.3. Various financial and non-financial incentives can effectively encourage electric vehicle uptake, including: free, discounted, or preferential-location parking; free or reduced road and bridge tolls; and allowing electric vehicles to drive in bus or carpool lanes.4. Several cities are restricting or planning to restrict the access that internal combustion engine vehicles (ICEVs) have to certain areas. If these restrictions apply to most (or all) passenger ICEVs, they can promote PEV purchase and use in cities.5. Infrastructure development in cities should follow the same fundamental approach as that used outside of cities. The priority should be ensuring that PEV owners and prospective PEV buyers have access to charging at or near home. Workplace and public charging should be developed for those who cannot access charging at or near home.6. Cities should be strategic in their approach, first identifying the goals they want to achieve, and then exploring what steps they can take to meet these goals. The steps available will likely differ between cities due to the different ways in which roads, parking, and any other vehicle infrastructure is governed

Near-infrared spectroscopy of the Blue Compact Dwarf galaxy Markarian 59

We present near-infrared (NIR) spectroscopic observations of the blue compact dwarf (BCD) galaxy Mrk 59, obtained with the TripleSpec spectrograph mounted on the 3.5m APO telescope. The NIR spectrum of Mrk 59, which covers the 0.90 - 2.40 micron wavelength range, shows atomic hydrogen, molecular hydrogen, helium, sulfur and iron emission lines. The NIR data have been supplemented by a SDSS optical spectrum. We found extinction in the BCD to be low [A(V)=0.24 mag] and to be the same in both the optical and NIR ranges. The NIR light does not reveal hidden star formation. The H2 emission comes from dense clumps and the H2 vibrational emission line intensities can be accounted for by photon excitation. No shock excitation is needed. A CLOUDY photoinization model of Mrk 59 reproduces well the observed optical and NIR emission line fluxes. There is no need to invoke sources of ionization other than stellar radiation.The [FeII] 1.257 and 1.643 micron emission lines, often used as supernova shock indicators in low-excitation high-metallicity starburst galaxies, cannot play such a role in high-excitation low-metallicity HII regions such as Mrk 59.Comment: 23 pages, 3 figures, accepted for publication in the Astrophysical Journa

Atomic Hydrogen produced in M33 Photodissociation Regions

We derive total (atomic + molecular) hydrogen densities in giant molecular clouds (GMCs) in the nearby spiral galaxy M33 using a method that views the atomic hydrogen near regions of recent star formation as the product of photodissociation. Far-UV photons emanating from a nearby OB association produce a layer of atomic hydrogen on the surfaces of nearby GMCs. Our approach provides an estimate of the total hydrogen density in these GMCs from observations of the excess far-UV emission that reaches the GMC from the OB association, and the excess 21-cm radio HI emission produced after these far-UV photons convert H2 into HI on the GMC surface. The method provides an alternative approach to the use of CO emission as a tracer of H2 in GMCs, and is especially sensitive to a range of density well below the critical density for CO(1-0) emission. We describe our "PDR method" in more detail and apply it using GALEX far-UV and VLA 21-cm radio data to obtain volume densities in a selection of GMCs in the nearby spiral galaxy M33. We have also examined the sensitivity of the method to the linear resolution of the observations used; the results obtained at 20 pc are similar to those for the larger set of data at 80 pc resolution. The cloud densities we derive range from 1 to 500 cm-3, with no clear dependence on galactocentric radius; these results are generally similar to those obtained earlier in M81, M83, and M101 using the same method.Comment: Accepted for publication in MNRAS. 25 figures, 16 tables, including online-only material