The set of all
-ary strings that do not contain repeated substrings of length
(i.e., that do not contain substrings of the form
,
, and
) constitutes a code correcting an arbitrary number of ...tandem-duplication mutations of length
. In other words, any two such strings are non-confusable in the sense that they cannot produce the same string while evolving under tandem duplications of length
. We demonstrate that this code is asymptotically optimal in terms of rate, meaning that it represents the largest set of non-confusable strings up to subexponential factors. This result settles the zero-error capacity problem for the last remaining case of tandem-duplication channels satisfying the “root-uniqueness” property.
ABSTRACT
Machine learning is an automatic technique that is revolutionizing scientific research, with innovative applications and wide use in astrophysics. The aim of this study was to develop an ...optimized version of an Artificial Neural Network machine learning method for classifying blazar candidates of uncertain type detected by the Fermi Large Area Telescope γ-ray instrument. The final result of this study increased the classification performance by about 80 ${{\ \rm per\ cent}}$ with respect to previous method, leaving only 15 unclassified blazars out of 573 blazar candidates of uncertain type listed in the LAT 4-year Source Catalog.
A communication scenario is described involving a series of events triggered by a transmitter and observed by a receiver experiencing relativistic time dilation. The message selected by the ...transmitter is assumed to be encoded in the events’ timings and is required to be perfectly recovered by the receiver, regardless of the difference in clock rates in the two frames of reference. It is shown that the largest proportion of the space of all
k
-event signals that can be selected as a code ensuring error-free information transfer in this setting equals
ζ
(
k
)
−1
, where
ζ
is the Riemann zeta function.
Context. XMM-Newton
provides unprecedented insight into the X-ray Universe, recording variability information for hundreds of thousands of sources. Manually searching for interesting patterns in ...light curves is impractical, requiring an automated data-mining approach for the characterization of sources.
Aims.
Straightforward fitting of temporal models to light curves is not a sure way to identify them, especially with noisy data. We used unsupervised machine learning to distill a large data set of light-curve parameters, revealing its clustering structure in preparation for anomaly detection and subsequent searches for specific source behaviors (e.g., flares, eclipses).
Methods.
Self-organizing maps (SOMs) achieve dimensionality reduction and clustering within a single framework. They are a type of artificial neural network trained to approximate the data with a two-dimensional grid of discrete interconnected units, which can later be visualized on the plane. We trained our SOM on temporal-only parameters computed from ⪆10
5
detections from the Exploring the X-ray Transient and variable Sky catalog.
Results.
The resulting map reveals that the ≈2500 most variable sources are clustered based on temporal characteristics. We find distinctive regions of the SOM map associated with flares, eclipses, dips, linear light curves, and others. Each group contains sources that appear similar by eye. We single out a handful of interesting sources for further study.
Conclusions.
The condensed view of our dataset provided by SOMs allowed us to identify groups of similar sources, speeding up manual characterization by orders of magnitude. Our method also highlights problems with fitting simple temporal models to light curves and can be used to mitigate them to an extent. This will be crucial for fully exploiting the high data volume expected from upcoming X-ray surveys, and may also help with interpreting supervised classification models.
Purpose: The aim of this study is to measure retinal vessel density and flow rate area by optical coherence tomography angiography (OCTA) in patients with autoimmune diseases taking ...hydroxychloroquine (HCQ). Methods: The cross-sectional study included 98 patients divided into three groups. Group I included patients with the diagnosis of an autoimmune disease, for whom the introduction of HCQ was planned. Group II implied low-risk patients for retinal toxicity (≤5 years of HCQ use), whereas Group III implied patients that were at high-risk (>5 years of drug use). All patients underwent a computerized visual field, central macular thickness by optical coherence tomography, and OCTA measurements. Results: The vascular density was found to be statistically significantly decreased in the high-risk group compared to the control group in the superficial parafoveal zone (P = 0.030), whereas it was decreased compared to the low-risk and control groups in the deep layers whole (P = 0.006, P = 0.010, respectively) and perifoveal zones (P = 0.003, P = 0.010, respectively). The foveal avascular zone was significantly enlarged in the high-risk group compared to the control (P < 0.018). Retinal flow rates did not show statistically significant differences between the groups (P > 0.05). Conclusion: Patients treated with HCQ for more than 5 appear have a significant loss of vascular density in the parafoveal and perifoveal regions, and FAZ area is significantly increased compared to low-risk patients and controls. These findings indicate that OCTA may be beneficial for monitoring high-risk patients and may stratify their risk of further retinal damage.
In this paper, for the first time type and texture of northern Serbian soils were examined using DRIFT spectroscopy. It was investigated whether it is possible to use the specular reflection of the ...quartz band for the purpose of the preliminary quantitative determination of texture properties. Investigation is conducted on the five most common soil types in Vojvodina: Arenosols, Fluvisols, Chernozems, Vertisols and Solonetz. Spectra were obtained using diffuse reflectance (DRIFT) technique in mid-IR. Spectral characteristics for five characteristic soil types in this region were determined. Certain regularities were observed regarding inorganic bands and main relations between these inorganic components and the texture parameters were determined. The empirical equation for the rough preliminary estimation of the soil texture was determined based on the absorbance values on the 2228 and 1211 cm−1.
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•For the first time, DRIFT spectroscopic study of soils from Serbia was performed.•Significant correlations between textural and spectral parameters were observed.•Inverted quartz band was used for semi-quantitative determination.•Empirical equation for preliminary estimation of soil texture was determined.
We analyze GRB 151027A within the binary-driven hypernova approach, with a progenitor of a carbon-oxygen core on the verge of a supernova (SN) explosion and a binary companion neutron star (NS). The ...hypercritical accretion of the SN ejecta onto the NS leads to its gravitational collapse into a black hole (BH), to the emission of the gamma-ray burst (GRB), and to a copious e+e− plasma. The impact of this e+e− plasma on the SN ejecta explains the early soft X-ray flare observed in long GRBs. Here, we apply this approach to the ultra-relativistic prompt emission (UPE) and to the hard X-ray flares. We use GRB 151027A as a prototype. From the time-integrated and the time-resolved analysis, we identify a double component in the UPE and confirm its ultra-relativistic nature. We confirm the mildly relativistic nature of the soft X-ray flare, of the hard X-ray flare, and of the extended thermal emission (ETE). We show that the ETE identifies the transition from an SN to a hypernova (HN). We then address the theoretical justification of these observations by integrating the hydrodynamical propagation equations of the e+e− into the SN ejecta, with the latter independently obtained from 3D smoothed particle hydrodynamics simulations. We conclude that the UPE, the hard X-ray flare, and the soft X-ray flare do not form a causally connected sequence. Within our model, they are the manifestation of the same physical process of the BH formation as seen through different viewing angles, implied by the morphology and the ∼300 s rotation period of the HN ejecta.
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•Spray drying enables production of s-SMEDDS with high SMEDDS loading (up to 67% w/w).•Mixing time of dispersion before spray drying has impact on process yield.•Carrier type has ...impact on process yield, drug content and s-SMEDDS characteristics.•Carvedilol forms amides with fatty acids from the oily components of SMEDDS.
In this study, various formulations of solidified carvedilol-loaded SMEDDS with high SMEDDS loading (up to 67% w/w) were produced with the spray drying process using various porous silica-based carriers. The process yield was improved with higher atomization gas flow rate during the spray drying process and with prolonged mixing time of dispersion of liquid SMEDDS and solid porous carriers prior to the spray drying process. Depending on the choice of the carrier and the SMEDDS:carrier ratio in solid SMEDDS, different drug loading, self-microemulsifying properties, drug release rates, and released drug fractions were obtained. The products exhibited fast drug release due to preserved self-microemulsifying properties and the absence of crystalline carvedilol, which was confirmed with XRD and Raman mapping. A decrease in drug content during the stability study was observed and investigated. This was at least partially attributed to the chemical degradation of the drug. Key degradation products determined by the LC-MS method were amides formed by in situ reaction of carvedilol with fatty acids present in the oily phase of SMEDDS.
: The aim of the study was to evaluate vision-related quality of life (VR-QOL) and treatment satisfaction (TS) in patients with diabetic retinopathy treated with panretinal photocoagulation (PRP).
: ...The panel study included 95 patients who underwent PRP for diabetic retinopathy. Eligible patients with no history of previous PRP were interviewer-administered the National Eye Institute Visual Function Questionnaire (NEI VFQ-25) and Retinopathy Treatment Satisfaction Questionnaire (RetTSQ) beforehandand one month after the last session of laser application. The study was conducted between June 2017 and June 2019 at tertiary care center in Serbia, Belgrade. We assessed pre- to post-PRP values of the composite score and subscale scores of VFQ-25 and RetTSQ, using a paired samples
-test. Univariate logistic regression was used to analyze the relationship between binary outcomes and potential predictors. Multivariate regression included predictors from univariate analyses that were statistically significant.
: The mean VFQ-25 composite score was 65.4 ± 17.4 before and 63.3 ± 19.5 after PRP (
= 0.045). Subscale analysis showed that two of the 11 items achieved a significant decrease after laser application (general vision and dependency). The mean RetTSQ score at baseline was 60.0 ± 11.8 and at the exit visit was 60.3 ± 12.3 (
= 0.858). Sub-scale analysis showed significant deterioration for five of the 13 items. Multivariate logistic regression found that significant predictor of VFQ-25 composite score reduction was fewer laser burns (
= 0.002) while significant predictor of RetTSQ total score reduction was presence of hyperlipidaemia (
= 0.021).
: The use of vision-related quality of life and treatment satisfaction questionnaires in conjunction with clinical examination, appears to provide a more comprehensive overview of an individual's daily well-being following PRP. Laser treatment for diabetic retinopathy leads to deterioration of some of the patients' perceived VR-QOL and TS. Health-care providers should inform patients about their treatment options and together decide which therapeutic method is best for them.
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