975 research outputs found
On the masses and evolutionary status of the black hole binary GX 339-4: a twin system of XTE J1550-564?
No full textWe apply the K-correction to the black hole low-mass X-ray binary (LMXB) GX 339-4 which implies MX? 6 M? by only assuming that the companion is more massive than ?0.17 M?, the lower limit allowed by applying a ‘stripped-giant’ model. This evolutionary model successfully reproduces the observed properties of the system. We obtain a maximum mass for the companion of M2? 1.1 M? and an upper limit to the mass ratio of q(=M2/MX) ? 0.125. The high X-ray activity displayed by the source suggests a relatively large mass transfer rate which, according to the model, results in M2? 0.3 M? and MX? 7 M?. We have also applied this scenario to the black hole binary XTE J1550-564, which has a similar orbital period but the donor is detected spectroscopically. The model successfully reproduces the observed stellar parameter
An ultraviolet laser microprobe for the in situ analysis of multisulfur isotopes and its use in measuring Archean sulfur isotope mass-independent anomalies
No full text
On the dimension of the global attractor for the damped Sine-Gordon equation
No full textThis article gives a more precise estimate on the dimension of the global attractor for the damped Sine-Gordon equation. The gained Hausdorff dimension remains small for large damping, which conforms to physics. (C) 1997 American Institute of Physics.Physics, MathematicalSCI(E)9ARTICLE63137-31413
Optical spectroscopy of the low-mass X-ray binary GX 9+9
No full textPhase-resolved medium-resolution VLT spectroscopy of the low-mass X-ray binary GX 9+9 has revealed narrow C ill emission lines that move in phase relative to our new estimate of the ephemeris, and show a velocity amplitude of 230 +/not superset of 35 km s(-1). We identify the origin of these lines as coming from the surface of the donor star, thereby providing the first estimate of the mass function of f(M-1) >= 0.22 M-circle dot. Rotational broadening estimates together with assumptions for the mass donor give 0.07 <= q <= 0.35 and 182 <= K-2 <= 406 km s(-1). Despite a low-mass ratio, there is no evidence for a superhump in our data set. Doppler maps of GX 9+9 show the presence of a stream overflow, either in the form of material flowing downward along the accretion disc rim or in a similar fashion as occurs in high mass transfer rate cataclysmic variables known as the SW Sex stars. Finally, we note that the Bowen region in GX 9+9 is dominated by C in instead of N III emission as has been the case for most other X-ray binaries
Short-term state forecasting-aided method for detection of smart grid general false data injection attacks
No full textSuccessful detection of false data injection attacks (FDIAs) is essential for ensuring secure power grids operation and control. First, this paper extends the approximate dc model to a more general linear model that can handle both supervisory control and data acquisition and phasor measurement unit measurements. Then, a general FDIA based on this model is derived and the error tolerance of such attacks is discussed. To detect such attacks, a method based on short-term state forecasting considering temporal correlation is proposed. Furthermore, a statistics-based measurement consistency test method is presented to check the consistency between the forecasted measurements and the received measurements. This measurement consistency test is further integrated with ∞-norm and L2-norm-based measurement residual analysis to construct the proposed detection metric. The proposed detector addresses the shortcoming of previous detectors in terms of handling critical measurements. Besides, the removal problem of attacked measurements, which may cause the system to become unobservable, is addressed effectively by the proposed method through forecasted measurements. Numerical tests on IEEE 14-bus and 118-bus test systems verify the effectiveness and performance of the proposed method
Petechiae: Reproducible Pattern of Distribution and Increased Appearance After Bed Rest
No full textExposure to acceleration can cause petechial hemorrhages,
called G measles. Petechiae usually start to develop between
5 and 9 G with a high interindividual variance. Centrifuge training
delays the onset to higher G levels. One might expect onset at lower
G levels after bed rest; however, there is no evidence in the literature. A
case of petechiae formation after bed rest is presented here. Case report:
Orthostatic tolerance was tested using a tilt table and lower body negative
pressure before and after bed rest in both campaigns of a 2 3 21-d
bed rest study with 6° head-down tilt. A 42-yr-old male Caucasian without
any history of thrombosis, venous disease, hemorrhage, or petechiae,
and with a negative thrombophilia screening, took part in the bed
rest study as 1 out of 10 subjects. He was the only one to develop petechiae
during the orthostatic tests after, but not before, bed rest in both
campaigns. Petechiae were distributed throughout the lower legs and
most pronounced at the shin in a stocking-like fashion, surprisingly reoccurring
in an identical pattern of distribution. Petechiae appeared slowly
over minutes during hyperemia. Discussion: This case indicates that
prolonged bed rest decreases the threshold for petechiae formation.
A reproducible distribution pattern suggests that factors predisposing to
petechiae formation keep their local distribution over time (possibly due
to local vessel structures). Mechanisms of adaptation and interindividual
variance are unclear. Findings are of clinical relevance as such cases
might occur after prolonged bed rest in patients without need of expensive
testing
A Two-stage Kick Scenario for the Peculiar Low-mass X-Ray Binary GX 1+4
No full textThe low-mass X-ray binary (LMXB) GX 1+4 stands out with its unique properties. Despite being an old system, it hosts a strongly magnetized neutron star (NS), a trait usually linked to younger systems. Its exceptionally long orbital period (1160 days) and low eccentricity (0.101) imply that the NS formed with minimal mass loss and a weak natal kick. These features collectively point toward the NS having formed through the accretion-induced collapse (AIC) of a white dwarf. However, GX 1+4’s unusually high peculiar velocity (∼189.36 km s ^−1 ) defies standard AIC explanations. To address this discrepancy, we propose a two-stage kick scenario within the AIC framework: an initial natal kick followed by a delayed electromagnetic “rocket effect” kick. Our Monte Carlo simulations indicate that while the natal kick (≲100 km s ^−1 ) can generate a wide range of orbital eccentricities, the subsequent rocket kick (∼240–480 km s ^−1 ) explains both the high systemic velocity and low eccentricity. This two-stage kick mechanism naturally reproduces the observed characteristics of GX 1+4, provided that the NS’s initially buried magnetic field reemerges after the acceleration process ends. Our study represents the first attempt to quantitatively constrain the kick velocities in GX 1+4 and underscores the importance of possible rocket kicks in forming such peculiar LMXB systems
SURFACE-CHEMICAL PROPERTIES OF ALKYLMETHYLSULFOXIDE IONIC SURFACTANT SYSTEMS
No full textThe surface adsorption and micelle formation of the aqueous solutions of alkyl (C8 and C10) methylsulfoxide [A]-ionic surfactant (C7F15COONa (I), C10H21SO4Na (II) or C10H21N(CH3)3Br (III) mixtures were investigated by the surface tension method. It was found that there is significant synergism in the surface activity of the A-I and -II systems, but not in that of the A-III system. This is shown by the fact that we can obtain the ??CMC and CMC minima in the A-I system and the CMC minimum in the A-II system, but neither of these in the A-III system; furthermore, the negative values of ??-m are much larger in the A-I and -II systems than in the A-III system.Chemistry, PhysicalSCI(E)EI7ARTICLE3-4289-3003
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