The Formaldehyde Masers in Sgr B2: Very Long Baseline Array and Very Large Array Observations

Observations of two of the formaldehyde (H2CO) masers (A and D) in Sgr B2 using the VLBA+Y27 (resolution ~0.01") and the VLA (resolution ~9") are presented. The VLBA observations show compact sources (<10 milliarcseconds, <80 AU) with brightness temperatures >10^8 K. The maser sources are partially resolved in the VLBA observations. The flux densities in the VLBA observations are about 1/2 those of the VLA; and, the linewidths are about 2/3 of the VLA values. The applicability of a core-halo model for the emission distribution is demonstrated. Comparison with earlier H2CO absorption observations and with ammonia (NH3) observations suggests that H2CO masers form in shocked gas. Comparison of the integrated flux densities in current VLA observations with those in previous observations indicates that (1) most of the masers have varied in the past 20 years, and (2) intensity variations are typically less than a factor of two compared to the 20-year mean. No significant linear or circular polarization is detected with either instrument.Comment: 20 pages, 3 figures, 5 tables, accepted to Ap

Segregation of Fat Factors in Milk Production

The need of an investigation into the problem of inheritance of fat in milk, has long been recognized by the practical milk producer and the physiologist. For the former, a solution of the problem would simplify, very markedly, his breeding operations, as well as increase the certainty of his results. For the latter, a knowledge of the fat producing possibilities of the animal genetically would give an index to the physiological limits of fat formation, and its relation to metabolism

Noise induced oscillations in non-equilibrium steady state systems

We consider effect of stochastic sources upon self-organization process being initiated with creation of the limit cycle. General expressions obtained are applied to the stochastic Lorenz system to show that departure from equilibrium steady state can destroy the limit cycle at certain relation between characteristic scales of temporal variation of principle variables. Noise induced resonance related to the limit cycle is found to appear if the fastest variations displays a principle variable, which is coupled with two different degrees of freedom or more.Comment: 11 pages, 4 figures. Submitted to Physica Script

Persistence, extinction and spatio-temporal synchronization of SIRS cellular automata models

Spatially explicit models have been widely used in today's mathematical ecology and epidemiology to study persistence and extinction of populations as well as their spatial patterns. Here we extend the earlier work--static dispersal between neighbouring individuals to mobility of individuals as well as multi-patches environment. As is commonly found, the basic reproductive ratio is maximized for the evolutionary stable strategy (ESS) on diseases' persistence in mean-field theory. This has important implications, as it implies that for a wide range of parameters that infection rate will tend maximum. This is opposite with present results obtained in spatial explicit models that infection rate is limited by upper bound. We observe the emergence of trade-offs of extinction and persistence on the parameters of the infection period and infection rate and show the extinction time having a linear relationship with respect to system size. We further find that the higher mobility can pronouncedly promote the persistence of spread of epidemics, i.e., the phase transition occurs from extinction domain to persistence domain, and the spirals' wavelength increases as the mobility increasing and ultimately, it will saturate at a certain value. Furthermore, for multi-patches case, we find that the lower coupling strength leads to anti-phase oscillation of infected fraction, while higher coupling strength corresponds to in-phase oscillation.Comment: 12page

Rendering an Account: An Open-State Archive in Postgraduate Supervision

The paper begins with a brief account of the transformation of research degree studies under the pressures of global capitalism and neo-liberal governmentality. A parallel transformation is occurring in the conduct of research through the use of information and communication technologies. Yet the potential of ICTs to shape practices of surveillance or to produce new student-supervisor relations and enhance the processes of developing the dissertation has received almost no critical attention. As doctoral supervisor and student, we then describe the features and uses of a web-based open state archive of the student's work-in-progress, developed by the student and accessible to his supervisor. Our intention was to encourage more open conversations between data and theorising, student and supervisor, and ultimately between the student and professional community. However, we recognise that relations of accountability, as these have developed within a contemporary "audit revolution" (Power, 1994, 1997) in universities, create particular "lines of visibility" (Munro, 1996). Thus while the open-state archive may help to redefine in less managerial terms notions of quality, transparency, flexibility and accountability, it might also make possible greater supervisory surveillance. How should we think about the panoptical potential of this archive? We argue that the diverse kinds of interactional patterns and pedagogical intervention it encourages help to create shifting subjectivities. Moreover, the archive itself is multiple, in bringing together an array of diverse materials that can be read in various ways, by following multiple paths. It therefore constitutes a collage, which we identify as a mode of cognition and of accounting distinct from but related to argument and narrative. As a more "open" text (Iser, 1978) it has an indeterminacy which may render it less open to abuse for the technologies of managerial accountability

A parallelizable augmented Lagrangian method applied to large-scale non-convex-constrained optimization problems

We contribute improvements to a Lagrangian dual solution approach applied to large-scale optimization problems whose objective functions are convex, continuously differentiable and possibly nonlinear, while the non-relaxed constraint set is compact but not necessarily convex. Such problems arise, for example, in the split-variable deterministic reformulation of stochastic mixed-integer optimization problems. We adapt the augmented Lagrangian method framework to address the presence of nonconvexity in the non-relaxed constraint set and to enable efficient parallelization. The development of our approach is most naturally compared with the development of proximal bundle methods and especially with their use of serious step conditions. However, deviations from these developments allow for an improvement in efficiency with which parallelization can be utilized. Pivotal in our modification to the augmented Lagrangian method is an integration of the simplicial decomposition method and the nonlinear block Gauss-Seidel method. An adaptation of a serious step condition associated with proximal bundle methods allows for the approximation tolerance to be automatically adjusted. Under mild conditions optimal dual convergence is proven, and we report computational results on test instances from the stochastic optimization literature. We demonstrate improvement in parallel speedup over a baseline parallel approach

A Search for H2CO 6cm Emission toward Young Stellar Objects III: VLA Observations

We report the results of our third survey for formaldehyde (H2CO) 6cm maser emission in the Galaxy. Using the Very Large Array, we detected two new H2CO maser sources (G23.01-0.41 and G25.83-0.18), thus increasing the sample of known H2CO maser regions in the Galaxy to seven. We review the characteristics of the G23.01-0.41 and G25.83-0.18 star forming regions. The H2CO masers in G23.01-0.41 and G25.83-0.18 share several properties with the other known H2CO masers, in particular, emission from rich maser environments and close proximity to very young massive stellar objects.Comment: Accepted for publication in the Astrophysical Journal Supplement Serie

Excitations in the Halo Nucleus He-6 Following The Li-7(gamma,p)He-6 Reaction

A broad excited state was observed in 6-He with energy E_x = 5 +/- 1 MeV and width Gamma = 3 +/- 1 MeV, following the reaction Li-7(gamma,p)He-6. The state is consistent with a number of broad resonances predicted by recent cluster model calculations. The well-established reaction mechanism, combined with a simple and transparent analysis procedure confers considerable validity to this observation.Comment: 3 pages of LaTeX, 3 figures in PostScript, approved for publication in Phys. Rev. C, August, 200

The Formaldehyde Masers in NGC 7538 and G29.96-0.02: VLBA, MERLIN, and VLA Observations

The 6 cm formaldehyde (H2CO) maser sources in the compact HII regions NGC 7538-IRS1 and G29.96-0.02 have been imaged at high resolution (beams < 50 mas). Using the VLBA and MERLIN, we find the angular sizes of the NGC 7538 masers to be ~10 mas (30 AU) corresponding to brightness temperatures ~10^8 K. The angular sizes of the G29.96-0.02 masers are ~20 mas (130 AU) corresponding to brightness temperatures ~10^7 K. Using the VLA, we detect 2 cm formaldehyde absorption from the maser regions. We detect no emission in the 2 cm line, indicating the lack of a 2 cm maser and placing limits on the 6 cm excitation process. We find that both NGC 7538 maser components show an increase in intensity on 5-10 year timescales while the G29.96-0.02 masers show no variability over 2 years. A search for polarization provides 3-sigma upper limits of 1% circularly polarized and 10% linearly polarized emission in NGC 7538 and of 15% circularly polarized emission in G29.96-0.02. A pronounced velocity gradient of 28 km/s/arcsecond (1900 km/s/pc) is detected in the NGC 7538 maser gas.Comment: accepted to ApJ, 15 figures, 11 table

Compton Scattering from the Deuteron and Extracted Neutron Polarizabilities

Differential cross sections for Compton scattering from the deuteron were measured at MAX-lab for incident photon energies of 55 MeV and 66 MeV at nominal laboratory angles of $45^\circ$, $125^\circ$, and $135^\circ$. Tagged photons were scattered from liquid deuterium and detected in three NaI spectrometers. By comparing the data with theoretical calculations in the framework of a one-boson-exchange potential model, the sum and difference of the isospin-averaged nucleon polarizabilities, $\alpha_N + \beta_N = 17.4 \pm 3.7$ and $\alpha_N - \beta_N = 6.4 \pm 2.4$ (in units of $10^{-4}$ fm$^3$), have been determined. By combining the latter with the global-averaged value for $\alpha_p - \beta_p$ and using the predictions of the Baldin sum rule for the sum of the nucleon polarizabilities, we have obtained values for the neutron electric and magnetic polarizabilities of $\alpha_n= 8.8 \pm 2.4$(total) $\pm 3.0$(model) and $\beta_n = 6.5 \mp 2.4$(total) $\mp 3.0$(model), respectively.Comment: 4 pages, 2 figures, revtex. The text is substantially revised. The cross sections are slightly different due to improvements in the analysi