Power scaling, vascular branching patterns, and the golden ratio

The Golden Ratio (a ratio of ~1.618:1) appears repeatedly in nature including structural and functional traits of organisms (e.g. Fibonacci spirals of snail shells and certain seed heads), the spiraled shape of galaxies and hurricanes, and even in much cultural architecture and art. In the mid-19th century, branching structures in plant and animal vascular systems were found to follow the Golden Ratio; that is, successive branches in the vascular systems of plants and animals tend to follow a length ratio of about 1.618:1. Here we present a model that uses this empirical evidence as a branching ratio in theoretical vascular systems. We then use a defined mass of the model system as a predictor of log-log scaling of terminal units. In this model, log terminal units and log mass scale similarly with that of other models as well as empirical evidence, but with more parsimony and a perspective not yet offered among all available models of allometric scaling. This model invites novel and broad hypotheses on the influence of the Golden Ratio on power scaling in organisms

Radio Polarization of the Young High-Magnetic-Field Pulsar PSR J1119-6127

We have investigated the radio polarization properties of PSR J1119-6127, a recently discovered young radio pulsar with a large magnetic field. Using pulsar-gated radio imaging data taken at a center frequency of 2496 MHz with the Australia Telescope Compact Array, we have determined a rotation measure for the pulsar of +842 +/- 23 rad m^-2. These data, combined with archival polarimetry data taken at a center frequency of 1366 MHz with the Parkes telescope, were used to determine the polarization characteristics of PSR J1119-6127 at both frequencies. The pulsar has a fractional linear polarization of ~75% and ~55% at 1366 and 2496 MHz, respectively, and the profile consists of a single, wide component. This pulse morphology and high degree of linear polarization are in agreement with previously noticed trends for young pulsars (e.g., PSR J1513-5908). A rotating-vector (RV) model fit of the position angle (PA) of linear polarization over pulse phase using the Parkes data suggests that the radio emission comes from the leading edge of a conal beam. We discuss PSR J1119-6127 in the context of a recent theoretical model of pulsar spin-down which can in principle be tested with polarization and timing data from this pulsar. Geometric constraints from the RV fit are currently insufficient to test this model with statistical significance, but additional data may allow such a test in the future.Comment: 9 pages, including 6 figures and 1 table. Accepted for publication in Ap

The Complex Wind Torus and Jets of PSR B1706-44

We report on Chandra ACIS imaging of the pulsar wind nebula (PWN) of the young Vela-like PSR B1706-44, which shows the now common pattern of an equatorial wind and polar jets. The structure is particularly rich, showing a relativistically boosted termination shock, jets with strong confinement, a surrounding radio/X-ray PWN and evidence for a quasi-static `bubble nebula'. The structures trace the pulsar spin geometry and illuminate its possible relation to SNR G343.1-2.3. We also obtain improved estimates of the pulsar flux and nebular spectrum, constraining the system age and energetics.Comment: To appear in the Astrophysical Journal. 15pp, 4 figures in 7 file

Discovery of circularly polarised radio emission from SS 433

We report the discovery of circularly polarised radio emission from the radio-jet X-ray binary SS 433 with the Australia Telescope Compact Array. The flux density spectrum of the circular polarization, clearly detected at four frequencies between 1 - 9 GHz, has a spectral index of (-0.9 +/- 0.1). Multiple components in the source and a lack of very high spatial resolution do not allow a unique determination of the origin of the circular polarization, nor of the spectrum of fractional polarization. However, we argue that the emission is likely to arise in the inner regions of the binary, possibly via propagation-induced conversion of linear to circular polarization, and the fractional circular polarization of these regions may be as high as 10%. Observations such as these have the potential to investigate the composition, whether pairs or baryonic, of the ejecta from X-ray binaries.Comment: Accepted for publication in ApJ Letter

A radio supernova remnant associated with the young pulsar J1119-6127

We report on Australia Telescope Compact Array observations in the direction of the young high magnetic-field pulsar J1119-6127. In the resulting images we identify a non-thermal radio shell of diameter 15', which we classify as a previously uncatalogued young supernova remnant, G292.2-0.5. This supernova remnant is positionally coincident with PSR J1119-6127, and we conclude that the two objects are physically associated. No radio emission is detected from any pulsar wind nebula (PWN) associated with the pulsar; our observed upper limits are consistent with the expectation that high magnetic-field pulsars produce radio nebulae which fade rapidly. This system suggests a possible explanation for the lack of an associated radio pulsar and/or PWN in many supernova remnants.Comment: 13 pages, 6 embedded eps figures. Accepted to Ap

Controlling the quality factor of a tuning-fork resonance between 9 K and 300 K for scanning-probe microscopy

We study the dynamic response of a mechanical quartz tuning fork in the temperature range from 9 K to 300 K. Since the quality factor Q of the resonance strongly depends on temperature, we implement a procedure to control the quality factor of the resonance. We show that we are able to dynamically change the quality factor and keep it constant over the whole temperature range. This procedure is suitable for applications in scanning probe microscopy.Comment: 5 pages, 6 figure

Acute EBV infection masquerading as "In-situ Follicular Lymphoma": a pitfall in the differential diagnosis of this entity

We present the case of a 30 year-old man who was referred for evaluation of diffuse lymphadenopathy. Six weeks prior, he noticed darkening of his urine associated with pale stools, nausea and an eventual 30 lb weight loss within a month. The initial laboratory findings showed elevation of the liver enzymes. A CT scan showed mesenteric and periaortic lymphadenopathy with the largest lymph node measuring 2.8 cm. Other laboratory results were otherwise unremarkable (including a normal LDH) with the exception of positive serum antibodies against Epstein-Barr virus (EBV) associated antigens (IgM+ and IgG+). An excisional biopsy of 4 of the small neck lymph nodes showed a normal architecture with prominent follicles and an intact capsule. But, by immunohistochemistry two of the follicles showed aberrant coexpression of BCL-2, in addition to CD10 and BCL-6. In-situ hybridization for early Epstein-Barr virus mRNA (EBER) and immunohistochemistry for latent membrane protein-1 (LMP-1) stained both scattered positive cells, as well as BCL-2 positive B-cells. Although an original diagnosis of in-situ follicular lymphoma was favored at an outside facility, additional interphase fluorescence in situ hybridization (FISH) studies for t(14;18);(IGH-BCL2) rearrangement (performed on the BCL-2 + follicles microdissected from the tissue block; Abott probe dual colour fusion) and molecular studies (IGH gene rearrangement by PCR, also performed on the microdissected follicles) were negative. Serologic studies (positive EBV antibodies) and immunostains in conjunction with the molecular studies confirmed the reactive nature of the changes. Our case also shows direct immunopathogenic evidence of BCL-2 expression among the EBV-infected cells, which has to our knowledge not been previously documented in vivo. A diagnosis of EBV infection should, therefore, be considered when confronted with BCL-2 expression in germinal centers, particularly in younger individuals, as the diagnosis of FLIS may lead to extensive and invasive haematologic work-ups. VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/132365631894006

Polarization observations in a low synchrotron emission field at 1.4 GHz

We present the first observation of the diffuse polarized synchrotron radiation of a patch ($\sim 3^\circ \times 3^\circ$) in the BOOMERanG field, one of the areas with the lowest CMB foreground emission. The work has been carried out with the Australia Telescope Compact Array at 1.4 GHz with 3.4 arcmin resolution and sensitivity of $\sim 0.18$ mJy beam$^{-1}$. The mean polarized signal has been found to be $P_{rms} = \sqrt{(Q_{rms}^2 + U_{rms}^2)} = 11.6 \pm 0.6$ mK, nearly one order of magnitude below than in the Galactic Plane. Extrapolations to frequencies of interest for cosmological investigations suggest that polarized synchrotron foreground noise should allow the detection of the CMB Polarization $E$--mode already at 32 GHz and make us confident that, at 90 GHz, it is accessible with no relevant foreground contamination. Last but not least, even the $B$--mode detection for $T/S > 0.01$ is not ruled out in such a low emission patch.Comment: Uses emulateapj.sty, onecolfloat.sty, 5 pages 4 fig., accepted for publication in ApJ