JPEG steganography: A performance evaluation of quantization tables

The two most important aspects of any image based steganographic system are the imperceptibility and the capacity of the stego image. This paper evaluates the performance and efficiency of using optimized quantization tables instead of default JPEG tables within JPEG steganography. We found that using optimized tables significantly improves the quality of stego-images. Moreover, we used this optimization strategy to generate a 16x16 quantization table to be used instead of that suggested. The quality of stego-images was greatly improved when these optimized tables were used. This led us to suggest a new hybrid steganographic method in order to increase the embedding capacity. This new method is based on both and Jpeg-Jsteg methods. In this method, for each 16x16 quantized DCT block, the least two significant bits (2-LSBs) of each middle frequency coefficient are modified to embed two secret bits. Additionally, the Jpeg-Jsteg embedding technique is used for the low frequency DCT coefficients without modifying the DC coefficient. Our experimental results show that the proposed approach can provide a higher information-hiding capacity than the other methods tested. Furthermore, the quality of the produced stego-images is better than that of other methods which use the default tables

High capacity steganographic method based upon JPEG

The two most important aspects of any image-based steganographic system are the quality of the stegoimage and the capacity of the cover image. This paper proposes a novel and high capacity steganographic approach based on Discrete Cosine Transformation (DCT) and JPEG compression. JPEG technique divides the input image into non-overlapping blocks of 8x8 pixels and uses the DCT transformation. However, our proposed method divides the cover image into nonoverlapping blocks of 16x16 pixels. For each quantized DCT block, the least two-significant bits (2-LSBs) of each middle frequency coefficient are modified to embed two secret bits. Our aim is to investigate the data hiding efficiency using larger blocks for JPEG compression. Our experiment result shows that the proposed approach can provide a higher information hiding capacity than Jpeg-Jsteg and Chang et al. methods based on the conventional blocks of 8x8 pixels. Furthermore, the produced stego-images are almost identical to the original cover images

Quantum probes for the cutoff frequency of Ohmic environments

Quantum probing consists of suitably exploiting a simple, small, and controllable quantum system to characterize a larger and more complex system. Here, we address the estimation of the cutoff frequency of the Ohmic spectral density of a harmonic reservoir by quantum probes. To this aim, we address the use of single-qubit and two-qubit systems and different kinds of coupling with the bath of oscillators. We assess the estimation precision by the quantum Fisher information of the sole quantum probe as well as the corresponding quantum signal-to-noise ratio. We prove that, for most of the values of the Ohmicity parameter, a simple probe such as a single qubit is already optimal for the precise estimation of the cutoff frequency. Indeed for those values, upon considering a two-qubit probe either in a Bell or in separable state, we do not find improvement to the estimation precision. However, we also showed that there exist few conditions where employing two qubits in a Bell state interacting with a common bath is more suitable for precisely estimating the cutoff frequency.Comment: 8 pages, 5 figures, 1 tabl

Resistance to Drought in Shore Elurope (\u3ci\u3eAeluropus litoralis\u3c/i\u3e) and Weeping Alkaligrass (\u3ci\u3ePuccinellia distans\u3c/i\u3e)

Two rangeland grass species, Shore Elurope (Aeluropus litoralis) and Weeping Alkaligrass (Puccinellia distans) were studied. The research was done under a split plot experiment and completely randomized design. Plants were grown under two irrigation treatments (seven and fourteen day periods of irrigation treatments). Morphological response included determination of wilting percentage, leaf water potential, production of yield, root dry weight, weight ratio of root/stem and finally total dry weight of species. Anatomical studies included leaf descriptive structure such as comparison of stomata and their density in area unit, study of vascular structure, mesophyl tissues and epiderm. Results showed increment of wilting percentage with increased of drought periods. This percentage was higher in Shore Elurope in comparison with Weeping Alkaligrass. Increment of stress reduced stem dry weight and total dry weight in species such that the decrease was higher in Weeping Alkaligrass. It was determined that Weeping Alkaligrass was more resistant to drought than Shore Elurope

Bayesian blind component separation for Cosmic Microwave Background observations

We present a technique for the blind separation of components in CMB data. The method uses a spectral EM algorithm which recovers simultaneously component templates, their emission law as a function of wavelength, and noise levels. We test the method on Planck HFI simulated observations featuring 3 astrophysical components.Comment: 15 pages, 5 figures, to appear in the Proceedings of the MAXENT 2001 international worksho

Laparoscopic versus open appendectomy in children with complicated appendicitis

Introduction: Acute appendicitis represents one of the most common causes of urgent surgical interventions in pediatric age group. With the advances in minimal invasive surgery laparoscopic appendectomy (LA) has been introduced as a suitable line of treatment. We compare between laparoscopic and conventional open appendectomy in the treatment of complicated appendicitis in children.Patients and methods: During the period from October 2012 to March 2016, 390 children with acute complicated appendicitis diagnosed clinically and with laboratory and available imaging studies were operated. LA performed for 200 cases and open conventional appendectomy for 190 cases. Three ports technique was used in laparoscopic cases. The operating table is shifted in Trendelenburg position and towards the left side. The surgeon stands on the left side of the patient. The appendicular mesoappendix was secured using electro cautery. The base was secured by extracorporeal ties and the appendix was retrieval within the umbilical port. The wounds were closed. Open appendectomy was done through McBurny incision as the traditional approach.Results: A total of 390 children diagnosed with acute complicated appendicitis were operated. The mean age was 12.04 years in group A and 12.2 in group B. There were 260 were boys and 130 were girls. The mean operative time in the laparoscopic group was 56.4 min; while in the conventional group was 63.42 min.Conclusion: LA was a suitable, effective and safe procedure in complicated cases that did not involve the base. It was associated with lower complications rate withall the advances of minimal invasive surgery when compared to the conventional open appendectomy.Keywords: appendectomy, children, complicated, laparoscopi

Group-galaxy correlations in redshift space as a probe of the growth of structure

We investigate the use of the cross-correlation between galaxies and galaxy groups to measure redshift-space distortions (RSD) and thus probe the growth rate of cosmological structure. This is compared to the classical approach based on using galaxy auto-correlation. We make use of realistic simulated galaxy catalogues that have been constructed by populating simulated dark matter haloes with galaxies through halo occupation prescriptions. We adapt the classical RSD dispersion model to the case of the group-galaxy cross-correlation function and estimate the RSD parameter $\beta$ by fitting both the full anisotropic correlation function $\xi(r_p,\pi)$ and its multipole moments. In addition, we define a modified version of the latter statistics by truncating the multipole moments to exclude strongly non-linear distortions at small transverse scales. We fit these three observable quantities in our set of simulated galaxy catalogues and estimate statistical and systematic errors on $\beta$ for the case of galaxy-galaxy, group-group, and group-galaxy correlation functions. When ignoring off-diagonal elements of the covariance matrix in the fitting, the truncated multipole moments of the group-galaxy cross-correlation function provide the most accurate estimate, with systematic errors below 3% when fitting transverse scales larger than $10Mpc/h$. Including the full data covariance enlarges statistical errors but keep unchanged the level of systematic error. Although statistical errors are generally larger for groups, the use of group-galaxy cross-correlation can potentially allow the reduction of systematics while using simple linear or dispersion models.Comment: 18 pages, 16 figure