Dust-Deficient Palomar-Green Quasars and the Diversity of AGN Intrinsic IR Emission

To elucidate the intrinsic broadband infrared (IR) emission properties of active galactic nuclei (AGNs), we analyze the spectral energy distributions (SEDs) of 87 z<0.5 Palomar-Green (PG) quasars. While the Elvis AGN template with a moderate far-IR correction can reasonably match the SEDs of the AGN components in ~60% of the sample (and is superior to alternatives such as that by Assef), it fails on two quasar populations: 1) hot-dust-deficient (HDD) quasars that show very weak emission thoroughly from the near-IR to the far-IR, and 2) warm-dust-deficient (WDD) quasars that have similar hot dust emission as normal quasars but are relatively faint in the mid- and far-IR. After building composite AGN templates for these dust-deficient quasars, we successfully fit the 0.3-500 {\mu}m SEDs of the PG sample with the appropriate AGN template, an infrared template of a star-forming galaxy, and a host galaxy stellar template. 20 HDD and 12 WDD quasars are identified from the SED decomposition, including seven ambiguous cases. Compared with normal quasars, the HDD quasars have AGN with relatively low Eddington ratios and the fraction of WDD quasars increases with AGN luminosity. Moreover, both the HDD and WDD quasar populations show relatively stronger mid-IR silicate emission. Virtually identical SED properties are also found in some quasars from z = 0.5 to 6. We propose a conceptual model to demonstrate that the observed dust deficiency of quasars can result from a change of structures of the circumnuclear tori that can occur at any cosmic epoch.Comment: minor corrections to match the published versio

Capitalist Monster and Bottled Passengers: Political Stakes of Embodiment in The Reincarnated Giant and The Last Subway

During the Dublin Worldcon in August 2019, I attended a panel discussion entitled “The Global Perspectives on Chinese Science Fiction,” which I had the privilege of transcribing. At this panel, Professor David Der-wei Wang, the Edward C. Henderson Professor of Chinese Literature at Harvard University, once again reiterated his understanding of Chinese SF as a unique approach to engage in the broader domain of cultural politics in contemporary China. While acknowledging that “our [sf] writers are really motivated to create a lot of new and different themes,” he believes the underpinning question still to be answered urgently is: “how much political stake are we taking at this critical moment of Chinese history?

A Nostalgic Return to the Future: The Utopian Dialectic in Hao Jingfang's Vagabonds

As one of the most representative writers of contemporary Chinese science fiction, Hao Jingfang is well known for her world-building that blends the characteristics of both utopia and dystopia, especially in Vagabonds. In line with the classic utopian dialectic in Le Guin’s The Dispossessed, Hao Jingfang has also set up two opposing worlds: the libertarian Earth that welcomes market competition and individualistic pursuit for capital and the egalitarian Martian Republic built upon scarcity and under the supervision of a central archive system that provides social welfare and protection. However, neither of the two societies is “perfect” enough to be called a true utopia. People in both societies see the other world as the negation of their own, though this, again, simply traps them in an unending cycle of “negating to negation.” Through such a process of negative hermeneutic, Vagabonds provides a dialectical paradigm with which to interrogate China’s postsocialist transition since the 1990s while invoking a utopian hope for a post-postsocialist alternative for China

Flexible Neural Electrode Array Based-on Porous Graphene for Cortical Microstimulation and Sensing.

Neural sensing and stimulation have been the backbone of neuroscience research, brain-machine interfaces and clinical neuromodulation therapies for decades. To-date, most of the neural stimulation systems have relied on sharp metal microelectrodes with poor electrochemical properties that induce extensive damage to the tissue and significantly degrade the long-term stability of implantable systems. Here, we demonstrate a flexible cortical microelectrode array based on porous graphene, which is capable of efficient electrophysiological sensing and stimulation from the brain surface, without penetrating into the tissue. Porous graphene electrodes show superior impedance and charge injection characteristics making them ideal for high efficiency cortical sensing and stimulation. They exhibit no physical delamination or degradation even after 1 million biphasic stimulation cycles, confirming high endurance. In in vivo experiments with rodents, same array is used to sense brain activity patterns with high spatio-temporal resolution and to control leg muscles with high-precision electrical stimulation from the cortical surface. Flexible porous graphene array offers a minimally invasive but high efficiency neuromodulation scheme with potential applications in cortical mapping, brain-computer interfaces, treatment of neurological disorders, where high resolution and simultaneous recording and stimulation of neural activity are crucial

Tunneling magnetoresistance in diluted magnetic semiconductor tunnel junctions

Using the spin-polarized tunneling model and taking into account the basic physics of ferromagnetic semiconductors, we study the temperature dependence of the tunneling magnetoresistance (TMR) in the diluted magnetic semiconductor (DMS) trilayer heterostructure system (Ga,Mn)As/AlAs/(Ga,Mn)As. The experimentally observed TMR ratio is in reasonable agreement with our result based on the typical material parameters. It is also shown that the TMR ratio has a strong dependence on both the itinerant-carrier density and the magnetic ion density in the DMS electrodes. This can provide a potential way to achieve larger TMR ratio by optimally adjusting the material parameters.Comment: 5 pages (RevTex), 3 figures (eps), submitted to PR