Skin Cancer Prediction Model Based on Multi-Layer Perceptron Network

Melanoma is acknowledged by the World Health Organization as the most severe type of skin cancer, significantly contributing to skin cancer-related deaths worldwide. This type of cancer manifests through noticeable changes in moles, including their size, shape, colour, or texture. In this study, we introduce an innovative and robust method for detecting and classifying melanoma in various image types, including both basic and clinical dermatological images. Our approach employs the HSV (Hue, Saturation, and Value) colour model, along with mathematical morphology and Gaussian filtering techniques. These methods are used to pinpoint the area of interest in an image and compute four key descriptors crucial for melanoma analysis: symmetry, border irregularity, colour variation, and dimension. Despite the prior usage of these descriptors over an extended period, the manner in which they are calculated in this proposal is a key factor contributing to the improvement of the outcomes. Following this, a multilayer perceptron is utilized for the purpose of categorizing malignant and benign melanoma. The study included three datasets consisting of basic and dermatological photographs that are frequently referenced in academic literature. These datasets were applied to both train and assess the effectiveness of the proposed technique. Based on the results obtained from k-fold cross-validation, it is evident that the proposed model surpasses three existing state-of-the-art approaches. In particular, the model demonstrates remarkable precision, with an accuracy rate of 98.5% for basic images and 98.6% for clinical dermatological images. It exhibits a high level of sensitivity, measuring 96.68% for simple images and 98.05% for dermatological images. Additionally, its specificity stands at 98.15% when analyzing basic images and 98.01% for dermatological images, indicating its effectiveness in both types of image analysis. The findings have demonstrated that the utilization of this gadget as an assistive tool for melanoma diagnosis would enhance levels of reliability in comparison to traditional methods

Photoevaporation and close encounters: how the environment around Cygnus OB2 affects the evolution of protoplanetary disks

In our Galaxy, star formation occurs in a variety of environments, with a large fraction of stars formed in clusters hosting massive stars. OB stars have an important feedback on the evolution of protoplanetary disks around nearby young stars and likely on the process of planet formation occurring in them. The nearby massive association Cygnus OB2 is an outstanding laboratory to study this feedback. It is the closest massive association to our Sun, and hosts hundreds of massive stars and thousands of low mass members. In this paper, we analyze the spatial variation of the disk fraction in Cygnus OB2 and we study its correlation with the local values of Far and Extreme ultraviolet radiation fields and the local stellar surface density. We present definitive evidence that disks are more rapidly dissipated in the regions of the association characterized by intense local UV field and large stellar density. In particular, the FUV radiation dominates disks dissipation timescales in the proximity (i.e. within 0.5 pc) of the O stars. In the rest of the association, EUV photons potentially induce a significant mass loss from the irradiated disks across the entire association, but the efficiency of this process is reduced at increasing distances from the massive stars due to absorption by the intervening intracluster material. We find that disk dissipation due to close stellar encounters is negligible in Cygnus OB2, and likely to have affected 1% or fewer of the stellar population. Disk dissipation is instead dominated by photoevaporation. We also compare our results to what has been found in other young clusters with different massive populations, concluding that massive associations like Cygnus OB2 are potentially hostile to protoplanetary disks, but that the environments where disks can safely evolve in planetary systems are likely quite common in our Galaxy.Comment: Accepted for publication in ApJS as part of the special issue on the Chandra Cygnus OB2 Legacy Projec

Detailed diagnostics of an X-ray flare in the single giant HR 9024

We analyze a 96 ks Chandra/HETGS observation of the single G-type giant HR 9024. The high flux allows us to examine spectral line and continuum diagnostics at high temporal resolution, to derive plasma parameters. A time-dependent 1D hydrodynamic model of a loop with half-length $L = 5 \times 10^{11}$ cm ($\sim R_{\star}/2$), cross-section radius $r = 4.3 \times 10^{10}$ cm, with a heat pulse of 15 ks and $2 \times 10^{11}$~erg cm$^{-2}$ s$^{-1}$ deposited at the loop footpoints, satisfactorily reproduces the observed evolution of temperature and emission measure, derived from the analysis of the strong continuum emission. For the first time we can compare predictions from the hydrodynamic model with single spectral features, other than with global spectral properties. We find that the model closely matches the observed line emission, especially for the hot ($\sim 10^8$ K) plasma emission of the FeXXV complex at $\sim 1.85$\AA. The model loop has $L/R_{\star} \sim 1/2$ and aspect ratio $r/L \sim 0.1$ as typically derived for flares observed in active stellar coronae, suggesting that the underlying physics is the same for these very dynamic and extreme phenomena in stellar coronae independently on stellar parameters and evolutionary stage.Comment: 26 pages. Accepted for publication on the Astrophysical Journa

Study experiences and the post-study intentions of female international undergraduate students

The number of female international students is increasing exponentially, and whilst international study may engender many benefits and challenges, little is known about their intentions once they complete their studies. This article reviews the literature on female international students with specific focus on exploring post-study intentions. A scoping review of four electronic databases was completed. After applying criteria to determine suitability, 30 publications were included in the final review. Analysis revealed three key foci: (1) the rationale for studying internationally; (2) the study experience; and (3) post-study intentions. The literature illustrates that an international study experience has the potential to be a powerful transformative opportunity if positive experiences outweigh the negatives. The findings also indicate that the post-study intentions of female international students are under-researched. The article contends that attention should be given to supporting the needs of this group, with a view to maximizing post-study opportunities

Rare events, escape rates and quasistationarity: some exact formulae

We present a common framework to study decay and exchanges rates in a wide class of dynamical systems. Several applications, ranging form the metric theory of continuons fractions and the Shannon capacity of contrained systems to the decay rate of metastable states, are given

X-ray Evidence of the Common Envelope Phase of V471 Tauri

Chandra Low Energy Transmission Grating Spectrograph observations of the pre-cataclysmic binary V471 Tau have been used to estimate the C/N abundance ratio of the K dwarf component for the first time. While the white dwarf component dominates the spectrum longward of 50 AA, at shorter wavelengths the observed X-ray emission is entirely due to coronal emission from the K dwarf. The H-like resonance lines of C and N yield an estimate of their logarithmic abundance ratio relative to the Sun of [C/N]=-0.38+/-0.15 - half of the currently accepted solar value. We interpret this result as the first clear observational evidence for the presumed common envelope phase of this system, during which the surface of the K dwarf was contaminated by CN-cycle processed material dredged up into the red giant envelope. We use the measured C/N ratio to deduce that 0.015-0.04 Msun was accreted by the K dwarf while engulfed, and show that this is consistent with a recent tentative detection of 13C in the K dwarf photosphere, and with the measured Li abundance in the scenario where the red giant companion was Li-rich during the common envelope phase.Comment: 6 pages, 2 figures, ApJL accepte