Dark Core Research Articles

Evolutionary view through the starless cores in Taurus

Context. The chemical and physical evolution of starless and pre-stellar cores are of paramount importance to understanding the process of star formation. The Taurus Molecular Cloud cores TMC 1-C and TMC 1-CP share similar initial conditions and provide an excellent opportunity to understand the evolution of the pre-stellar core phase. Aims. We investigated the evolutionary stage of starless cores based on observations towards the prototypical dark cores TMC 1-C and TMC 1-CP. Methods. We mapped the prototypical dark cores TMC 1-C and TMC 1-CP in the CS 3 → 2, C34S 3 → 2, 13CS 2 → 1, DCN 1 → 0, DCN 2 → 1, DNC 1 → 0, DNC 2 → 1, DN13C 1 → 0, DN13C 2 → 1, N2H+ 1 → 0, and N2D+ 1 → 0 transitions. We performed a multi-transitional study of CS and its isotopologs, DCN, and DNC lines to characterize the physical and chemical properties of these cores. We studied their chemistry using the state-of-the-art gas-grain chemical code NAUTILUS and pseudo time-dependent models to determine their evolutionary stage. Results. The central nH volume density, the N2H+ column density, and the abundances of deuterated species are higher in TMC 1-C than in TMC 1-CP, yielding a higher N2H+ deuterium fraction in TMC 1-C, thus indicating a later evolutionary stage for TMC 1-C. The chemical modeling with pseudo time-dependent models and their radiative transfer are in agreement with this statement, allowing us to estimate a collapse timescale of ~1 Myr for TMC 1-C. Models with a younger collapse scenario or a collapse slowed down by a magnetic support are found to more closely reproduce the observations towards TMC 1-CP. Conclusions. Observational diagnostics seem to indicate that TMC 1-C is in a later evolutionary stage than TMC 1-CP, with a chemical age ~1 Myr. TMC 1-C shows signs of being an evolved core at the onset of star formation, while TMC 1-CP appears to be in an earlier evolutionary stage due to a more recent formation or, alternatively, a collapse slowed down by a magnetic support.

Mineralization processes involved in the formation of the Jinya Carlin-type Au deposit, northwestern Guangxi, China: Evidence from in situ trace element and S isotope geochemistry of Au-bearing zoned pyrite

The Jinya Au deposit is a representative example of the Carlin-type Au mineralization located within the “Golden Triangle” area of the Yunnan, Guizhou, and Guangxi provinces, China. The deposit is located within a fault zone at the contact between a carbonate platform and contains Au mineralization hosted by arsenopyrite and pyrite, with the latter providing evidence of changes in fluid composition during pyrite growth. Back-scattered electron (BSE) images indicate that this Au-bearing zoned pyrite can be divided into dark cores (Py1), lighter colored central sections (Py2), and dark rims (Py3). Laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) and secondary ion mass spectrometry (SIMS) analyses provide information on compositional and S isotopic variations within this pyrite. These data indicate that each pyrite zone is compositionally homogeneous, showing Co/Ni ratios of <1. Pyrite has δ34S values ranging from –8.54‰ to –4.05‰, with Py1, Py2, and Py3 having average δ34S values of –6.89‰, –5.60‰, and –5.99‰, respectively. These values are indicative of thermochemical sulfate reduction (TSR) processes. Mineralizing fluids that formed the deposit derived from a sedimentary source mixed with variable amounts of meteoric water (Py1 = 3%; Py2 = 32%; Py3 = 23%). The ore-forming fluids within the sedimentary basin metasomatized the Fe-rich dolomitic rocks of the forming the early pyrite cores (Py1). This fluid flow focused along the main fault zone, which at this time was permeable, allowing with an influx of meteoric water. This mixing process lowered the temperature of the system, causing the precipitation of large volumes of Au and As. This caused the formation of the light-colored and As- and Au-enriched central parts of the pyrite within the deposit (i.e., Py2). A subsequent decrease in the amount of meteoric water in the system led the formation of the darker Py3 rims that contain low concentrations of As and Au.

The dark core of personality and sexism in sport

Sexism is often discussed in amateur and professional sport but has rarely been the focus of scientific research. This study sought to test whether benevolent and hostile sexism relate to dark personality traits (the dark core of personality [D]) and whether benevolent and hostile sexism and D differ across age, performance levels, and athlete sex. In total, 354 German athletes (177 men, 177 women; mean age = 32.0 ± 12.6 years) completed questionnaires at a single time-point. Results showed that, compared to female athletes, male athletes scored higher on ambivalent sexism and D. No differences were found between different performance levels or age in terms of D or components of sexism. Linear regression models showed that D is a significant predictor of ambivalent sexism. Psychological Entitlement predicted hostile and benevolent sexism in women, whereas Machiavellianism, Egoism, Greed, and Amoralism-Crudality predicted hostile sexism (but not benevolent sexism) in men. These findings provide a foundation for further research into the emergence of sexism in amateur and professional sport.

Sparse Bayesian mass mapping with uncertainties: hypothesis testing of structure

ABSTRACT A crucial aspect of mass mapping, via weak lensing, is quantification of the uncertainty introduced during the reconstruction process. Properly accounting for these errors has been largely ignored to date. We present a new method to reconstruct maximum a posteriori (MAP) convergence maps by formulating an unconstrained Bayesian inference problem with Laplace-type l1-norm sparsity-promoting priors, which we solve via convex optimization. Approaching mass mapping in this manner allows us to exploit recent developments in probability concentration theory to infer theoretically conservative uncertainties for our MAP reconstructions, without relying on assumptions of Gaussianity. For the first time, these methods allow us to perform hypothesis testing of structure, from which it is possible to distinguish between physical objects and artefacts of the reconstruction. Here, we present this new formalism, and demonstrate the method on simulations, before applying the developed formalism to two observational data sets of the Abell 520 cluster. Initial reconstructions of the Abell 520 catalogues reported the detection of an anomalous ‘dark core’ – an overdense region with no optical counterpart – which was taken to be evidence for self-interacting dark matter. In our Bayesian framework, it is found that neither Abell 520 data set can conclusively determine the physicality of such dark cores at $99{{\ \rm per\ cent}}$ confidence. However, in both cases the recovered MAP estimators are consistent with both sets of data.

Flow dynamics of shear-coaxial cryogenic nitrogen jets under supercritical conditions with and without acoustic excitations

The three-dimensional flow structures and dynamics of shear-coaxial nitrogen jets under supercritical conditions are comprehensively investigated using the large-eddy simulation technique. The theoretical framework is based on the full conservation laws and accommodates real-fluid thermodynamics and transport theories over the entire range of fluid states. Cryogenic liquid nitrogen (132 K) is delivered through the inner tube of a shear-coaxial nozzle, and gaseous nitrogen (191 K) is injected through the outer annulus, into a high-pressure environment at 233 K. Particular attention is paid to the influence of operating parameters on the flow evolution of the coaxial jets. Two supercritical pressure conditions, 4.94 and 10.0 MPa, and three outer-to-inner velocity ratios in the range of 2.03–3.75, are considered. Results reveal that the flowfield downstream of the coaxial jets is characterized by two potential cores and three shear layers. Two counter-rotating recirculation zones are formed next to the central post-tip. The characteristic frequencies of flow recirculation and shear-layer instability are analyzed using power spectral analysis. Increasing the pressure and the velocity ratio enhances turbulent mixing, promotes the entrainment of the outer stream into the inner region, and advances the pinching point of vortical motion to the centerline, thereby leading to a decreased length of the inner dark core. The predicted dark core length and outer spreading angle show good agreement with experimental results. The introduction of transverse acoustic excitation induces large sinusoidal oscillations of the inner dense-fluid stream along the direction of acoustic motion and promotes the mixing of the inner and outer streams.

The Good, the Bad, and the Ugly? A Triarchic Perspective on Psychopathy at Work

Does psychopathy have an upside in vocational contexts? Applying the triarchic model of psychopathy, we propose that the dimensions of boldness, disinhibition, and meanness have different relations to workplace outcomes. Focusing on boldness and in line with socioanalytic personality theory, we propose that political skill moderates the relation between boldness and job performance. Using a sample of 477 target-coworker pairings, we found interaction effects of boldness and political skill on contextual and task performance, and the buffering of counterproductive work behavior. Furthermore, political skill moderated the relation between boldness and adaptive performance. Disinhibition and meanness were positively correlated with counterproductive work behaviors, thereby reflecting the dark core of psychopathy. In sum, boldness is a trait linked to career success in the absence of the other traits that make up psychopathy as a whole. Furthermore, we encourage the use of the triarchic model as an overarching framework in vocational contexts.

Light Confinement with Structured Beams in Gold Nanoparticle Suspensions

We carry out an experimental campaign to investigate the nonlinear self-defocusing propagation of singular light beams with various complex structures of phase and intensity in a colloidal suspension of gold nanoparticles with a plasmonic resonance near the laser wavelength (532nm). Studying optical vortices embedded in Gaussian beams, Bessel vortices and Bessel-cosine (necklace) beams, we gather evidence that while intense vortices turn into two-dimensional dark solitons, all structured wavepackets are able to guide a weak Gaussian probe of different wavelength (632.8 nm) along the dark core. The probe confinement also depends on the topological charge of the singular pump.

Optical vortex lattice: an exploitation of orbital angular momentum

Abstract Generally, an optical vortex lattice (OVL) is generated via the superposition of two specific vortex beams. Thus far, OVL has been successfully employed to trap atoms via the dark cores. The topological charge (TC) on each optical vortex (OV) in the lattice is only ±1. Consequently, the orbital angular momentum (OAM) on the lattice is ignored. To expand the potential applications, it is necessary to rediscover and exploit OAM. Here we propose a novel high-order OVL (HO-OVL) that combines the phase multiplication and the arbitrary mode-controllable techniques. TC on each OV in the lattice is up to 51, which generates sufficient OAM to manipulate microparticles. Thereafter, the entire lattice can be modulated to desirable arbitrary modes. Finally, yeast cells are trapped and rotated by the proposed HO-OVL. To the best of our knowledge, this is the first realization of the complex motion of microparticles via OVL. Thus, this work successfully exploits OAM on OVL, thereby revealing potential applications in particle manipulation and optical tweezers.

Imprints of dark matter on black hole shadows using spherical accretions

We study the possibility of identifying dark matter in the galactic center from the physical properties of the electromagnetic radiation emitted from an optically-thin disk region around a static and spherically symmetric black hole. In particular, we consider two specific models for the optical-thin disk region: a gas at rest and a gas in a radial free fall. Due to the effect of dark matter on the spacetime geometry, we find that the dark matter can increase or decrease the intensity of the electromagnetic flux radiation depending on the dark matter model. To this end, we analyze two simple dark matter models having different mass functions {mathcal {M}}(r), with a matter mass M, thickness Delta r_s along with a dark matter core radius surrounding the black hole. In addition to that, we explore the scenario of a perfect fluid dark matter surrounding the black hole. We show that in order to have significant effect of dark matter on the intensity of the electromagnetic flux radiation, a high energy density of dark matter near the black hole is needed. We also find that the surrounding dark matter distribution plays a key role on the shadow radius and the intensity of the electromagnetic flux radiation, respectively. Finally we have used the relation between the shadow radius and the quasinormal modes (QNMs) to compute the real part of QNM frequencies.

Themes of the dark core of personality.

Enduring patterns of socially aversive behavior are ascribed to stable personality disorders (such as narcissistic or antisocial tendencies) in clinical psychology or to so called "dark" traits in personality psychology. As recently shown, the substantial overlap among the latter constructs is attributable to a single underlying disposition, called the Dark Factor of Personality (D). Whereas evidence supports the conceptualization of D as the core of aversive traits, the structure of the specific factors of D received less empirical attention so far. To this end, this study further scrutinizes the internal structure of D with items stemming from 12 different aversive traits assessed in three large and heterogeneous samples (total N > 160,000). Specifically, we (a) explored the bifactor structure of D using a modified "bass-ackwards" approach, (b) cross-validated the identified factor solutions via confirmatory factor analyses, and (c) examined the empirical relation of D and the specific factors to five criterion measures. Results indicate that a bifactor structure modeling D along with five specific factors-or themes-labeled Callousness, Deceitfulness, Narcissistic Entitlement, Sadism, and Vindictiveness, best describes the internal structure of D. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Synthesis of Fe3O4@MIL-101(Fe) for a Novel Electrochemistry Detection of Citric Acid

Introduction Urolithiasis is one of the most common diseases in the urinary system with very high incidence worldwide. In recent studies, citric acid (CA) has been considered as a biomarker of urolithiasis due to its vital suppression role in urinary stone formation. The detection of CA in urine is of great significance for early screening and prognostic monitoring of urolithiasis. However, most analytical methods for detecting CA are complicated and require expensive equipment.In the present study[1, 2], MIL-101(Fe) and Fe3O4 were used for electrochemical detection of CA, based on the reaction of Fe(Ⅲ) and CA. Following these ideas, the electrodes modified with Fe3O4@MIL-101(Fe) nanoparticles were fabricated and investigated for whether they were able to detect CA and improve the sensitivity. Method Synthesis of Fe3O4@MIL-101(Fe) nanoparticles(Figure1. A): The Fe3O4@MIL-101(Fe) core-shell nanoparticles were synthesized according to previous literatures[3, 4]. Specifically, 3.6 g NaAC and 0.87 g FeCl3 were dissolved in 75 mL ethylene glycol under ultrasound for 30 minutes. The mixture was transferred to a Teflon-lined autoclave chamber and heated at 200 °C for 16 h, then naturally cooled to room temperature. The obtained magnetic nanoparticles were collected with a magnet and washed with ethanol for three times. 350 mg above nanoparticles was dissolved to 75mL ethanol with 0.58mM Mercapto acetic acid (MAA), and gently stirred for 24h under nitrogen protection. The steps of self-assembly cycle were as follows. Firstly, 100 mg Fe3O4-MAA was dispersed in 10mM FeCl3, shaked for 1 minute and left for 15 minutes, then washed with ethanol for three times. Next, the nanoparticles was re-dispersed in 10 mM benzene-1,3,5-tricarboxylic acid, kept for 30 min at 70 °C with stripping, and then washed with ethanol for three times. After repeating this cycle 31 times, the synthesized core-shell nanoparticles were dried at 75 °C. Fabrication of the Fe3O4@MIL-101(Fe) /GCE: The GCE working electrode was polished with 1.0, 0.3, and 0.05 μm Al2O3 substance and sonicated with an ethyl alcohol and water solution for 5 min respectively then dried under a N2 stream. For the modification, the synthesized Fe3O4@MIL-101(Fe) core-shell nanoparticles was dissolved in ultrapure water and the final concentration was 1.0 mg/mL. After sonicating for 1 hour, 7 µL of the suspension was dripped onto the surface of the GCE and dried at room temperature. Detection of CA: Electrochemical analyses were carried out using differential pulse voltammetry (DPV) measurements in 0.01M KCl solution with different concentration of CA at pH 7.0. All experiments were performed at room temperature with a three-electrode system: Ag/AgCl (3 M KCl) electrode and platinum wire were used as a reference electrode and counter electrode, respectively, and applying in a potential range of 0 to 0.60 V, with an amplitude of 0.025 V and pulse period of 0.5 s. Results and Conclusions Characterization of Fe3O4@MIL-101(Fe): TEM images of as-prepared nanoparticles is shown in Figure 1. B. The Fe3O4@MIL-101(Fe) had spherical morphology and the core–shell structures which indicated the formation of MIL-101(Fe) layer on the Fe3O4 nanoparticles.. The dark core was the Fe3O4 with a diameter of about 348 nm, and the relatively bright outer layer was the MIL-101(Fe) with the thickness of 246 nm. The detection of CA: The DPVs of Fe3O4@MIL-101(Fe) /GCE in the 0.1M KCl with or without 100 mg/L CA are shown in Figure 1. C. In the presence of CA, a current peak was obtained in 0.324V. This could be explained due to the reaction of Fe3+ ions in Fe3O4@MIL-101(Fe) with CA. The performance of the Fe3O4@MIL-101(Fe) /GCE in different concentrations of CA solutions were monitored by DPV, and the corresponding ΔCurrent( ) are shown in Figure 1.D. The resulting calibration is presented in the Figure 1. E, which was linear over the concentration range of 40 to 100 mg/L and 100-500 mg/L CA, with the linear regression equations of Y = 0.0004*X +0.004 (R2 = 0.9956) and Y = 0.00016*X + 0.03773 (R2 = 0.9766), respectively. Based on three times the background noise, the modified electrode provided a limit of detection of 31 mg/L. References Valizadeh, H., J. Tashkhourian, and A.J.M.A. Abbaspour, A carbon paste electrode modified with a metal-organic framework of type MIL-101 (Fe) for voltammetric determination of citric acid. 2019. 186(7): p. 455. Guivar, J.A.R., et al., Preparation and characterization of cetyltrimethylammonium bromide (CTAB)-stabilized Fe3O4 nanoparticles for electrochemistry detection of citric acid. 2015. 755: p. 158-166. Chen, Y., et al., Facile preparation of core–shell magnetic metal–organic framework nanoparticles for the selective capture of phosphopeptides. 2015. 7(30): p. 16338-16347. Salman, F., A. Zengin, and H.Ç.J.I. Kazici, Synthesis and characterization of Fe 3 O 4-supported metal–organic framework MIL-101 (Fe) for a highly selective and sensitive hydrogen peroxide electrochemical sensor. 2020. 26(10): p. 5221-5232. Figure 1

Microscale solute flow probed with rotating microbead trapped in optical vortex

The dynamics of solute flow in the microscopic chamber can be studied with optical tweezers. A method based on the metallic microbeads trapped in the focused optical vortex beam is proposed. This annular beam of a twisted wavefront exerts torque on a reflective object placed inside the dark core of the vortex. The induced rotational movement of the bead is sensitive to local viscosity changes in the surrounding medium, for example, during the ongoing dissolution process. Two experimental configurations are described, both relying on tracing the angular velocity of the bead in time. In one-bead configuration, the dynamics of local solute concentration can be studied. In two-bead case, the direction and speed of solute flow can be probed with a spatial resolution of single micrometers. We approach the elementary problem of sucrose dissolution and diffusion in water. The surprising impression of the reverse solute flow was observed. Further experimental investigation led to the discovery that this phenomenon originates from the sucrose stream-like diffusion in the mid-depth of the measurement chamber. The rotating microbead method applies for various solid and liquid substances and may become a useful technique for microfluidics research.Graphic abstract

All-optical shaping non-conventional beams based on spatial cross-phase modulation

All-optical shaping non-conventional beams are demonstrated experimentally by means of spatial cross-phase modulation in the solution of azo-containing material. We report here that an annular beam is able to be generated and manipulated through a light-control-light system, including a focused controlling beam and a parallel controlled beam. As the intensity of controlling light is enhanced above the threshold, the circular dark core turns to a triangular shape gradually. The formation of the polygonal dark core is mainly attributed to the nonaxis-symmetrical thermal convection in the solution sample induced by the heat of controlling light, which breaks the symmetry in vertical direction of the refractive index distribution. In addition, when the controlled light is convergent, a series of concentric rings instead of annular beam is obtained. The formation of two kinds of non-conventional beams is discussed in terms of the conical distribution of the changed reflective index. This all-optical beam shaping reveals potential applications in optical limiting, all-optical modulation, optical trapping, etc.

Hinting a dark matter nature of Sgr A* via the S-stars

ABSTRACT The motion data of the S-stars around the Galactic Centre gathered in the last 28 yr imply that Sgr A* hosts a supermassive compact object of about $4 \times 10^6\, {\rm M}_{\odot }$, a result awarded with the Nobel Prize in Physics 2020. A non-rotating black hole (BH) nature of Sgr A* has been uncritically adopted since the S-star orbits agree with Schwarzschild geometry geodesics. The orbit of S2 has served as a test of general relativity predictions such as the gravitational redshift and the relativistic precession. The central BH model is, however, challenged by the G2 post-peripassage motion and by the lack of observations on event-horizon-scale distances robustly pointing to its univocal presence. We have recently shown that the S2 and G2 astrometry data are better fitted by geodesics in the spacetime of a self-gravitating dark matter core–halo distribution of 56 keV-fermions, ‘darkinos’, which also explains the outer halo Galactic rotation curves. This letter confirms and extends this conclusion using the astrometry data of the 17 best-resolved S-stars, thereby strengthening the alternative nature of Sgr A* as a dense core of darkinos.

The good, the bad, and the ugly: Revisiting the Dark Core

The aim of this research (N = 268) was to explore several compelling candidates for the Dark Core of the broader set of dark and light traits by using network analysis and analyses of shared variance. Several previously proposed cores were tested: primary psychopathy, narcissistic rivalry, Honesty-Humility, Aggressiveness, Selfishness, Antagonism and its callousness facet as well as emotional competency, including its emotionality facet as negative aspect of callousness. The results showed that central elements in this network are primary psychopathy, callousness, pathological selfishness, Machiavellianism, and narcissistic rivalry. Furthermore, among basic traits, Antagonism shared the highest percentage with the dark traits, especially its facet callousness, which is the best candidate for the Dark Core. The combination of callousness, deceitfulness, and grandiosity shared 92% of the total common variance with dark traits and it could be seen as the Antagonistic Triad or alternative Dark Triad.

OH, PAH, and sooting imaging in piloted liquid-spray flames of diesel and diesel surrogate

Comparison of the flame structure, polycyclic aromatic hydrocarbons (PAH), and soot formation characteristics of commercial diesel and a diesel surrogate is investigated using planar laser-induced fluorescence (PLIF) of OH and PAH at 283 nm, and laser-induced incandescence (LII) of soot at 1064 nm. The diesel and diesel surrogate flames present a similar overall appearance, with a “dark core” region of fine droplets exiting the injector and a light blue outer flame near the base. Hot soot regions appear downstream, indicated by bright yellowish flame luminosity. Comparison of simultaneously acquired single-laser-shot PLIF images of OH and PAH indicates that smaller PAH reside mostly in the central regime in the ~20–60% height of the flame, sandwiched between the flame fronts. In contrast, larger PAH and soot particles are formed further downstream. Soot-LII signals are present only in the upper ~40% height of the flame for both the fuels. The distribution of mean PAH-PLIF and soot-LII signals along the flame height is also found to be similar for both fuels, except diesel is shown to produce approximately 1.5× more soot than the diesel surrogate. Based on the analysis of probability distributions, the maximum OH-PLIF signals in both fuels have similar radial and axial spatial distributions, while maximum PAH-PLIF signals occur at a higher axial location for the diesel surrogate. However, for the diesel surrogate, maximum soot-LII signals are frequently appeared at lower heights. Therefore, exploration of more appropriate diesel surrogates may be necessary to closely mimic the PAH and soot formation behaviors of diesel fuel. The present study shows that the combined optical diagnostic techniques and the statistical analysis can be used for studying commercial diesel and diesel surrogates, and thus establish a robust framework for detailed studies of chemical kinetics, combustion dynamics, and soot formation in liquid hydrocarbon spray combustion.

Low Mass Black Holes from Dark Core Collapse.

Unusual masses of black holes being discovered by gravitational wave experiments pose fundamental questions about the origin of these black holes. Black holes with masses smaller than the Chandrasekhar limit ≈1.4 M_{⊙} are essentially impossible to produce through stellar evolution. We propose a new channel for production of low mass black holes: stellar objects catastrophically accrete nonannihilating dark matter, and the small dark core subsequently collapses, eating up the host star and transmuting it into a black hole. The wide range of allowed dark matter masses allows a smaller effective Chandrasekhar limit and thus smaller mass black holes. We point out several avenues to test our proposal, focusing on the redshift dependence of the merger rate. We show that redshift dependence of the merger rate can be used as a probe of the transmuted origin of low mass black holes.

Medea

Why does Medea’s act of killing her children stand out as one of the most horrific crimes/taboos in our collective memory? Why are we repulsed and why do we shudder as we hear her story, as well as other accounts of infanticide? Medea’s rageful act goes deep to a dark core of the psyche that we all possess. It horrifies us when we realize that we too have a similar potential for rage, hatred, and violence. It frightens us and pulls us inward; it is indeed awe-ful. The intent of this paper is to look at what happens symbolically when one is faced with and threatened with possession by dark forces that are part of our nature and our deeper Selves. I will attempt to illustrate from a depth-oriented, Jungian lens how Medea was possessed and ruled by the gods and goddesses; how hatred, the rage of being betrayed and separated from husband, homeland (and Self) ultimately leads her back to her essential nature of the sorceress, the dark side of the feminine.

Guiding light with singular beams in nanoplasmonic colloids

We investigate the nonlinear propagation of light beams with complex phase and intensity structures, including a Gaussian-embedded vortex, a Bessel vortex, and a Bessel-cosine necklace. We employ a colloidal suspension of bio-synthesized plasmonic gold nanoparticles, where a self-defocusing response is mediated by absorption at the laser wavelength (532 nm). We show that, by means of nonlocal nonlinearity, these structured two-dimensional beams with on-axis singularity can counteract the diffraction of the dark core and guide therein a coaxial Gaussian probe of different wavelengths (633 nm) and lower intensities. Angular steering of the confined probe is also demonstrated by tilting the propagation direction of the pump.

Performance Optimization of Many-Core Systems by Exploiting Task Migration and Dark Core Allocation

As an effective scheme often adopted for performance tuning in many-core processors, task migration provides an opportunity for “hot” tasks to be migrated to run on a “cool” core that has a lower temperature. When a task needs to migrate from one processor core to another, the migration can embark on numerous modes defined by the migration paths undertaken and/or the destinations of the migration. Selecting the right migration mode that a task shall follow has always been difficult, and it can be more challenging with the existence of dark cores that can be called back to service (reactivated), which ushers in additional task migration modes. Previous works have demonstrated that dark cores can be placed near the active cores to reduce power density so that the active cores can run at higher voltage/frequency levels for higher performance. However, the existing task migration schemes neither consider the impact of dark cores on each application's performance, nor exploit performance trade-off under different migration modes. Unlike the existing task migration schemes, in this article, a runtime task migration algorithm that simultaneously takes both migration modes and dark cores into consideration is proposed, and it essentially has two major steps. In the first step, for a specific migration mode that is tied to an application whose tasks need to be migrated, the number of dark cores is determined so that the overall performance is maximized. The second step is to find an appropriate core region and its location for each application to optimize the communication latency and computation performance; during this step, focus is placed on reducing the fragmentation of the free core regions resulting from the task migration. Experimental results have confirmed that our approach achieves over 50 percent reduction in total response time when compared to recently proposed thermal-aware runtime task migration approachess.