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Our ongoing investigation of how ‘Pillars’ and other structure form in molecular clouds irradiated by ultraviolet (UV) stars has revealed that the Rayleigh-Taylor instability is strongly suppressed by recombination in the photoevaporated outflow, that clumps and filaments may be key, that the evolution of structure is well-modeled by compressible hydrodynamics, and that directionality of the UV radiation may have significant effects. We discuss a generic, flexible set of laboratory experiments that can test these results.

The thermal pressure inside molecular clouds is insufficient for maintaining the pressure balance at an ablation front at the cloud surface illuminated by nearby UV stars. Most probably, the required stiffness is provided by the magnetic pressure. After surveying existing models of this type, we concentrate on two of them: the model of a quasi-homogeneous magnetic field and the recently proposed model of a “magnetostatic turbulence”. We discuss observational consequences of the two models, in particular, the structure and the strength of the magnetic field inside the cloud and in the ionized outflow. We comment on the possible role of reconnection events and their observational signatures. We mention laboratory experiments where the most significant features of the models can be tested.

Over the past few years, our group has been developing hydrodynamic models to simulate formation of the Eagle Nebula pillars. The true test of any model is, of course, how well it can reproduce the observations. Here, we discuss how we go about testing our models against observations. We describe the process by which we “observe” the model data to create synthetic maps. We show an example of this technique using one of our model runs and compare the resultant synthetic map to the real one.

We investigate hydrodynamic instability of accelerating ionization fronts using two dimensional hydrodynamic simulations that include detailed energy deposition and release due to the absorption of UV radiation, recombination of hydrogen, radiative molecular cooling, and magnetic pressure. We consider linear perturbation growth and find that the stabilization mechanism associated with non-accelerated fronts remains a significant factor even when acceleration is present. Conversely, if recombination in the ionized region is turned off,Rayleigh-Taylor (RT) instability becomes effective, and the classical RT growth rate recovered., 13 pages, 4 figures

We study both analytically and numerically hydrodynamical effects of two colliding shells, the simplified models of the internal shock in various relativistic outflows such as gamma-ray bursts and blazars. We pay particular attention to three interesting cases: a pair of shells with the same rest mass density (``{\it equal rest mass density}''), a pair of shells with the same rest mass (``{\it equal mass}''), and a pair of shells with the same bulk kinetic energy (``{\it equal energy}'') measured in the intersteller medium (ISM) frame. We find that the density profiles are significantly affected by the propagation of rarefaction waves. A split-feature appears at the contact discontinuity of two shells for the ``equal mass'' case, while no significant split appears for the ``equal energy'' and ``equal rest mass density'' cases. The shell spreading with a few ten percent of the speed of light is also shown as a notable aspect caused by rarefaction waves. The conversion efficiency of the bulk kinetic energy to internal one is numerically evaluated. The time evolutions of the efficiency show deviations from the widely-used inellastic two-point-mass-collision model., 29 pages, 16 figures, accepted by ApJ

The event related potential P300 is useful as an index of the fall of the cognitive function attends by aging and the diagnosis of dementia. If the generator of P300 is assumed to be equivalent current dipole (ECD), the negative wave should be recorded at other sites which polarity differs from the positive wave on the scalp. This study is to determine the most suitable reference electrode site for P300 recording and to improve S/N of P300. In order to record the P300 or N300 potential which spread on the scalp, earlobe (A1), oral (X1) and under site of the nose(X2) was used as a reference electrode. Auditory oddball paradigm which consists of the acoustic sound of 2000 Hz (targets) and 1000 Hz (standards) was used for the measurement of P300. In this results, P300 or N300 was measured by using earlobe(A1) site as a reference electrode. P300 wave was detected by Cz-A1 derivation and also the negative wave of N300 was detected by X1-A1 and X2-A1 derivation. These results demonstrate that there is an ECD which goes to the parietal region from internal focal area as a source of P300, and also suggest that P300 amplitude with Cz-X1 or Cz-X2 derivation is higher than that with Cz-A1 derivation. Therefore, it was speculated that the most suitable reference electrode sites for the improvement of the S/N in the P300 are oral (X1) or under the nose (X2) that show the negative potentials (N300).

We have isolated a clonal line reversed (rev) of homozygous Japanese flounder through gynogenesis. The homozygous offspring gynogenetically produced from rev exhibited reversal of organization of the metamorphic L/R asymmetry such as the direction of eye-migration at a high frequency (20-30%). The molecular analysis using a left-specific marker pitx2 revealed that the embryonic L/R axis was ambiguously established: in more than half of rev embryos, pitx2 was expressed bilaterally in the lateral plate mesoderm (LPM). Previous studies in other animals demonstrated that ectopic pitx2 expression in the LPM could cause laterality defects of the visceral organs. Likewise, our results using rev imply that bilateral pitx2 expression could lead to randomization of the visceral organs. Coincidence of ectopic pitx2 expression and reversal of the direction of eye-migration in the population of rev offspring suggests that the rev locus is critical in specification of both the metamorphic and the visceral L/R asymmetries. However, reversal of the sidedness of the orientation of the visceral organs was not always accompanied by reversal of the direction of metamorphic eye-migration, suggesting that different mechanisms should be involved downstream of the rev locus in directing these two phases of asymmetric morphogenesis in the Japanese flounder.

We explore the spectral and polarization properties of photospheric emissions from stratified jets in which multiple components, separated by a sharp velocity shear regions, are distributed in lateral direction. Propagation of thermal photons injected at high optical depth region are calculated until they escape from the photosphere. It is found that presence of the lateral structure within the jet leads to non-thermal feature of the spectra and significant polarization signal in the resulting emission. The deviation from thermal spectra as well as the polarization degree tends to be enhanced as the velocity gradient in the shear region increases. In particular, we show that emissions from multi-component jet can reproduce the typical observed spectra of gamma-ray bursts (GRBs) irrespective to the position of the observer when a velocity shear region is closely spaced in various lateral ($\theta$) positions. The degree of polarization associated in the emission is significant (> few%) at wide range of observer angles and can be higher than 30%., Comment: 21 pages, 12 figures, accepted for publication in ApJ

In this paper we present a numerical study of plasma jets produced by intense laser matter interactions. Through this study we hope to better understand astrophysical jets and their recent experimental simulations in the laboratory. We paid special attention to radiation cooling and the interaction of the jet with ambient gas. Four cases are presented in this paper; two of them deal with the propagation of jets in vacuum, while in the other two the propagation takes place in the ambient gas. Available experimental results are reproduced to good accuracy in the vacuum case. For jets in ambient gas, we find that the existence of the surrounding gas confines the jet into a narrow cylindrical shape so that both the density and temperature of the jet remain high enough for effective radiation cooling. As a result, a collimated plasma jet is formed in these cases. The dimensionless parameters characterizing the laboratory jets and protostellar jets have overlapping domains. We also discuss the cooling lengths for our model and compare them with the corresponding values in the astrophysical jets. A plasma jet in the ambient gas experiment is proposed which is within the reach of present day technology, and can be relevant to astrophysical phenomena., Comment: Accepted for publication in ApJ

The present issue of Discourse realizes one of the objectives of the current editorial board, which is to balance special issues that focus on specific themes and subjects with general issues that represent a broad range of contemporary examinations of vanguard culture, representation, critical theory, and media. One value of a general issue featuring a diversity of subjects, styles, and methodologies is that it offers the reader a horizon of critical analyses that nonetheless produce in the mix the distinct sensibilities that continue to define Discourse. This issue represents, in our opinion, the best traditions of Discourse , while opening onto new frontiers in the critical investigation of media, culture, and world representation. The articles that appear in this issue move through critical historiographies of Indonesian, Japanese, and Arab visual cultures; they look at the cinemas of exploration and queer temporalities, while addressing the figures of Bazin, Warhol, Pasolini, and Godard, among others; and they intervene in the ethics of trance, cannibalism, and narratives of the underclass. They feature proper names and historical moments both prominent and distant, forging a line of communication between various regions of the world, artistic and critical communities, and forms of expression. Each with a distinct voice, unique protocols and politics, and modes of analysis, the articles that constitute this volume reflect the force of Discourse as a critical forum for the rigorous analysis of representation and culture, one that demands a sustained scholarly focus but that still allows for creative experimentation. Many of the editorial changes (of personnel, institutional base and infrastructure, and editorial format) are now complete. We apologize for the sustained hiatus that rendered Discourse largely

We investigate the jet propagation and breakout from the stellar progenitor for gamma-ray burst (GRB) collapsars by performing two-dimensional relativistic hydrodynamic simulations and analytical modeling. We find that the jet opening angle is given by $\theta_j \sim 1/5 \Gamma_{0}$, and infer the initial Lorentz factor of the jet at the central engine, $\Gamma_0$, is a few for existing observations of $\theta_j$. The jet keeps the Lorentz factor low inside the star by converging cylindrically via collimation shocks under the cocoon pressure, and accelerates at jet breakout before the free expansion to a hollow-cone structure. In this new picture the GRB duration is determined by the sound crossing time of the cocoon, after which the opening angle widens, reducing the apparent luminosity. Some bursts violating the maximum opening angle $\theta_{j,\max}\sim 1/5 \sim 12^{\circ}$ imply the existence of a baryon-rich sheath or a long-acting jet. We can explain the slopes in both Amati and Yonetoku spectral relations using an off-centered photosphere model, if we make only one assumption that the total jet luminosity is proportional to the initial Lorentz factor of the jet. We also numerically calibrate the pre-breakout model (Bromberg et al.) for later use., Comment: 20 pages, 16 figures

We explore photospheric emissions from stratified two-component jets, wherein a highly relativistic spine outflow is surrounded by a wider and less relativistic sheath outflow. Thermal photons are injected in regions of high optical depth and propagated until they escape at the photosphere. Due to the presence of shear in velocity (Lorentz factor) at the boundary of the spine and sheath region, a fraction of the injected photons are accelerated via a Fermi-like acceleration mechanism such that a high energy power-law tail is formed in the resultant spectrum. We show, in particular, that if a velocity shear with a considerable variance in the bulk Lorentz factor is present, the high energy part of observed Gamma-ray Bursts (GRBs) photon spectrum can be explained by this photon acceleration mechanism. We also show that the accelerated photons may also account for the origin of the extra hard power-law component above the bump of the thermal-like peak seen in some peculiar bursts (e.g., GRB 090510, 090902B, 090926A). It is demonstrated that time-integrated spectra can also reproduce the low energy spectrum of GRBs consistently due to a multi-temperature effect when time evolution of the outflow is considered. Finally, we show that the empirical Ep-Lp relation can be explained by differences in the outflow properties of individual sources., Comment: 18 pages, 14 figures, accepted for publication in ApJ

"WITH A VIEW TO SPEECH" The Beast & the Sovereign, by Jacques Derrida, 2 volumes, translated by Geoffrey Bennington, edited by Geoffrey Bennington and Peggy Kamuf. The Seminars of Jacques Derrida. Chicago: University of Chicago Press, 2009 and 2011. Volume 1, 349 pp. $22.50 paper, $38.00 cloth. Volume 2, 293 pp. $30.00 e-book, $35.00 cloth.The first two volumes of an ambitious project to publish Jacques Derrida's complete "teaching lectures" or seminars, delivered between 1968 and 2003 in French and in English, begin at the end with Derrida's last, unfinished seminar "The Beast & the Sovereign," which he presented during 2001-3 in France and the United States. Geoffrey Bennington and Peggy Kamuf, who supervise the English edition of "The Seminars of Jacques Derrida," and are also involved in the French project published by Galilee, explain the process by which Derrida's lectures, which he called "seminars" and which were in most cases written out in their entirety beforehand, originally by hand, then by typewriter, and eventually electronically, were transcribed, and with minimal editing, published first in French and then in English translation. "In all cases," write Bennington and Kamuf, along with their cosignatories of the "General Introduction to the French Edition" (Marc Crepon, Marguerite Derrida, Thomas Dutoit, Michel Lise, Marie-Louise Mallet, and Ginette Michaud), "our primary goal is to present the text of the seminar, as written by Jacques Derrida with a view to speech, to reading aloud, and thus with some marks of anticipated orality and some familiar turns of phrase" (2009, xi, original emphases).Already at work in this complex project is an irreducible ambiguity regarding the phenomenality of the object, its objectivity (and objecthood) as such, but also its authority, specifically its authorship. These signatories, all of who worked closely with Derrida (including Marguerite), and whom Derrida trusted deeply, are also involved in an expanded economy of authorship that is not unrelated to Derrida's work. As they write in the general introduction, "It is not certain that Jacques Derrida would have published the seminars as they stand; probably he would have reorganized or rewritten them" (2009, xi). These supplementary texts, written and spoken by Derrida, bear the marks then of a quasi authorship, a virtual authorship he shares with his colleagues posthumously. This precarious authorship bears significantly upon the continued understanding of Derrida's oeuvre as a singularly important event in the history of twentiethcentury thought since it is precisely one of the themes to which Derrida turns and returns consistently, here and elsewhere: Who or what writes? Is writing written or spoken by a subject or does it arrive, return, take place ipso facto with or without an author? In his or her absence? And what constitutes writing, what are its genres, its genders even? Who or what is sovereign in writing, an author, he or she?Among the notable phrases in the editors' introduction is the claim that these seminars, to be distinguished from Derrida's published work, which he authorized as their author, which he authored in a more conventional sense of the term, are texts written by Derrida but "with a view to speech." That is, their authorship is performed as it were live, in full view, perhaps, a spectacle of speech and thought. What might such a view be, and how to view or review the visuality implicit in speech, inherent in the two volumes that signal the arrival of a writing genre with a view to and perhaps of speech? What mode of speech is made visible in these publications? What does this thought look like? As the editors suggest, it is Derrida himself, the dynamic temporality of his thought, what Jean-Claude Lebensztejn once referred to as Derrida's "extravagant patience," and the rhythms with which his thought unfolds that become visible.1 Not simply the thought made text, made flesh, transposed from and to a body fixed in space, but a movement in time, changing in time, over time and through space from one session to the next. …

In this study, the light curves and spectrum of the photospheric thermal radiation from ultrarelativistic gamma-ray burst (GRB) jets are calculated using two-dimensional relativistic hydrodynamic simulations of jets from a collapsar. As the jet advances, the density around the head of the jet decreases, and its Lorentz factor reaches as high as 200 at the photosphere and 400 inside the photosphere. For an on-axis observer, the photosphere appears concave due to the low density and high beaming factor of the jet. The luminosity varies because of the abrupt change in the position of the photosphere due to the internal structure of the jet. Comparing our results with GRB 090902B, the flux level of the thermal-like component is similar to our model, although the peak energy appears slightly higher (but still within a factor of two). From the comparison, we estimate that the bulk Lorentz factor of GRB 090902B is {Gamma} {approx} 2.4 x 10{sup 2}(r/10{sup 12} cm), where r is the radius of the photosphere. The spectrum for an on-axis observer is harder than that for an off-axis observer. There is a time lag of a few seconds for high energy bands in the light curve. This may be themore » reason for the delayed onset of GeV emission seen in GRB 080916C. The spectrum below the peak energy is a power law and the index is 2.3-2.6, which is softer than that of a single temperature Planck distribution but still harder than that of the typical value of the observed spectrum.« less