255 research outputs found
Fault-tolerant parallel scheduling of arbitrary length jobs on a shared channel
We study the problem of scheduling jobs on fault-prone machines communicating via a shared channel, also known as multiple-access channel. We have arbitrary length jobs to be scheduled on identical machines, of which are prone to crashes by an adversary. A machine can inform other machines when a job is completed via the channel without collision detection. Performance is measured by the total number of available machine steps during the whole execution. Our goal is to study the impact of preemption (i.e., interrupting the execution of a job and resuming later in the same or different machine) and failures on the work performance of job processing. The novelty is the ability to identify the features that determine the complexity (difficulty) of the problem. We show that the problem becomes difficult when preemption is not allowed, by showing corresponding lower and upper bounds, the latter with algorithms reaching them. We also prove that randomization helps even more, but only against a non-adaptive adversary; in the presence of more severe adaptive adversary, randomization does not help in any setting. Our work has extended from previous work that focused on settings including: scheduling on multiple-access channel without machine failures, complete information about failures, or incomplete information about failures (like in this work) but with unit length jobs and, hence, without considering preemption
Spin polarization of exciton-polariton condensate in a photonic synthetic effective magnetic field
We investigate the spin polarization of localized exciton-polariton
condensates. We demonstrate the presence of an effective magnetic field leading
to the formation of elliptically polarized condensates. We show that this
synthetic field has an entirely photonic origin, which we believe is unique for
the CdTe-based microcavities. Moreover, the degree of spin polarization of
localized polariton condensates in samples with magnetic ions depends on the
excitation power or polarization of the non-resonant excitation laser. In an
external magnetic field, the semimagnetic condensate spontaneously builds up
strong spin polarization. Based on the magnetic field behavior of the
condensate in the presence of magnetic ions, we apply a model that allows us to
estimate the polariton-polariton interaction strength in a CdTe-system to
approx. 0.8
2s exciton-polariton revealed in an external magnetic field
We demonstrate the existence of the excited state of an exciton-polariton in
a semiconductor microcavity. The strong coupling of the quantum well heavy-hole
exciton in an excited 2s state to the cavity photon is observed in non-zero
magnetic field due to surprisingly fast increase of Rabi energy of the 2s
exciton-polariton in magnetic field. This effect is explained by a strong
modification of the wave-function of the relative electron-hole motion for the
2s exciton state.Comment: 5 pages, 5 figure
Dietary Methionine Restriction Regulates Liver Protein Synthesis and Gene Expression Independently of Eukaryotic Initiation Factor 2 Phosphorylation in Mice
Background: The phosphorylation of eukaryotic initiation factor 2 (p-eIF2) during dietary amino acid insufficiency reduces protein synthesis and alters gene expression via the integrated stress response (ISR).Objective: We explored whether a Met-restricted (MR) diet activates the ISR to reduce body fat and regulate protein balance.Methods: Male and female mice aged 3-6 mo with either whole-body deletion of general control nonderepressible 2 (Gcn2) or liver-specific deletion of protein kinase R-like endoplasmic reticulum kinase (Perk) alongside wild-type or floxed control mice were fed an obesogenic diet sufficient in Met (0.86%) or an MR (0.12% Met) diet for ≤5 wk. Ala enrichment with deuterium was measured to calculate protein synthesis rates. The guanine nucleotide exchange factor activity of eIF2B was measured alongside p-eIF2 and hepatic mRNA expression levels at 2 d and 5 wk. Metabolic phenotyping was conducted at 4 wk, and body composition was measured throughout. Results were evaluated with the use of ANOVA (P < 0.05).Results: Feeding an MR diet for 2 d did not increase hepatic p-eIF2 or reduce eIF2B activity in wild-type or Gcn2-/- mice, yet many genes transcriptionally regulated by the ISR were altered in both strains in the same direction and amplitude. Feeding an MR diet for 5 wk increased p-eIF2 and reduced eIF2B activity in wild-type but not Gcn2-/- mice, yet ISR-regulated genes altered in both strains similarly. Furthermore, the MR diet reduced mixed and cytosolic but not mitochondrial protein synthesis in both the liver and skeletal muscle regardless of Gcn2 status. Despite the similarities between strains, the MR diet did not increase energy expenditure or reduce body fat in Gcn2-/- mice. Finally, feeding the MR diet to mice with Perk deleted in the liver increased hepatic p-eIF2 and altered body composition similar to floxed controls.Conclusions: Hepatic activation of the ISR resulting from an MR diet does not require p-eIF2. Gcn2 status influences body fat loss but not protein balance when Met is restricted
AlH lines in the blue spectrum of Proxima Centauri
The recently-computed ExoMol line lists for isotopologues of AlH are used to
analyse the blue spectrum (4000-4500 {\AA}) of Proxima Cen (M5.5 V). Comparison
of the observed and computed spectra enables the identification of a large
number of 27AlH lines of the A1{\Pi} - X1{\Sigma}+ band system: the spectral
range covering 1-0, 0-0 and 1-1 bands is dominated by clearly resolved AlH
lines. We reveal the diffuse nature of transitions close to the dissociation
limit which appears in the form of increasingly wider(up to 5 {\AA}) and
shallower (up to the continuum confusion limit) AlH line profiles. The
predicted wavelengths of AlH diffuse lines are systematically displaced. The
effect broadening by pre-dissociation states on the line profiles is included
by increasing the radiative damping rate by up to 5 orders of magnitude. We
determine empirical values of damping rates for a number of the clean 0-0
Q-branch transitions by comparing the observed and synthetic stellar spectra.
We find excellent agreement between our damping rates and lifetimes available
in the literature. A comparison of 27Al1H ExoMol and REALH spectra shows that
the observed spectrum is better described by the ExoMol line list. A search for
26Al1H lines in the Proxima Cen spectrum does not reveal any notable features;
giving an upper limit of 27Al1H/26Al1H {>} 100.Comment: 22 pages, 6 tables, 10 figs, accepted by MNRA
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