Two essential categories of LDPC codes that are more preferable to other types are quasi-cyclic LDPC (QC-LDPC) codes and spatially coupled LDPC convolutional codes (SC-LDPC-CCs) because of their ...excellent performance curves in waterfall and error floor regions. An efficient approach to construct these codes is protograph-based method that is categorized into two classes: single-edge (SE) and multiple-edge (ME) protographs. We, for the first time, provide a necessary and sufficient condition for exponent matrices of these codes with girth-8 and based on the ME-protographs. As a result, a lower bound on the lifting degree of girth-8 ME-QC-LDPC codes and a lower bound on the syndrome former memory order of girth-8 ME-SC-LDPC-CCs are obtained, which are tighter than the existing bounds in the literature.
The industrial activities of the last century have caused massive increases in human exposure to heavy metals. Mercury, lead, chromium, cadmium, and arsenic have been the most common heavy metals ...that induced human poisonings. Here, we reviewed the mechanistic action of these heavy metals according to the available animal and human studies. Acute or chronic poisonings may occur following exposure through water, air, and food. Bioaccumulation of these heavy metals leads to a diversity of toxic effects on a variety of body tissues and organs. Heavy metals disrupt cellular events including growth, proliferation, differentiation, damage-repairing processes, and apoptosis. Comparison of the mechanisms of action reveals similar pathways for these metals to induce toxicity including ROS generation, weakening of the antioxidant defense, enzyme inactivation, and oxidative stress. On the other hand, some of them have selective binding to specific macromolecules. The interaction of lead with aminolevulinic acid dehydratase and ferrochelatase is within this context. Reactions of other heavy metals with certain proteins were discussed as well. Some toxic metals including chromium, cadmium, and arsenic cause genomic instability. Defects in DNA repair following the induction of oxidative stress and DNA damage by the three metals have been considered as the cause of their carcinogenicity. Even with the current knowledge of hazards of heavy metals, the incidence of poisoning remains considerable and requires preventive and effective treatment. The application of chelation therapy for the management of metal poisoning could be another aspect of heavy metals to be reviewed in the future.
Low density parity check (LDPC) lattices were the first family of lattices equipped with iterative decoding algorithms. We introduce quasi-cyclic LDPC (QC LDPC) lattices as a special case of LDPC ...lattices with one binary QC-LDPC code as their underlying code. These lattices are obtained from the Construction A of lattices providing us to encode them efficiently using shift registers. To benefit from an encoder with linear complexity in the lattice dimension, we obtain the generator matrix of these lattices in quasi-cyclic form. We generalize the proposed quasi-cyclic form of the generator matrix for other Construction A lattices, namely the LDA lattices, with a non-binary QC-LDPC code as their underlying code. We provide a low-complexity decoding algorithm of QC LDPC-lattices based on the sum product algorithm. To design lattice codes, QC LDPC-lattices are combined with the nested lattice shaping that uses the Voronoi region of a sublattice for shaping. The shaping gain and the shaping loss of our lattice codes with dimensions 40, 50, and 60 using an optimal quantizer, are presented. The guidelines for applying efficient shaping methods, like hypercube shaping, for QC LDPC-lattices are also given. Consequently, we establish a family of lattice codes that perform practically close to the sphere bound.
This article reviews the use of case study research for both practical and theoretical issues especially in management field with the emphasis on management of technology and innovation. Many ...researchers commented on the methodological issues of the case study research from their point of view thus, presenting a comprehensive framework was missing. We try representing a general framework with methodological and analytical perspective to design, develop, and conduct case study research. To test the coverage of our framework, we have analyzed articles in three major journals related to the management of technology and innovation to approve our framework. This study represents a general structure to guide, design, and fulfill a case study research with levels and steps necessary for researchers to use in their research.
Aim
Several lines of evidence implicate glutamatergic dysfunction in the pathophysiology of obsessive–compulsive disorder (OCD), presenting this neurotransmitter as a target for the development of ...novel pharmacotherapy. The objective of this study was to assess the efficacy of minocycline as an augmentative agent to fluvoxamine in the treatment of patients with OCD.
Methods
One hundred and two patients with the diagnosis of moderate‐to‐severe OCD were recruited to this study. A randomized double‐blind trial was designed and patients received either L‐carnosine or placebo as adjuvant to fluvoxamine for 10 weeks. The patients randomly received either minocycline 100 mg twice per day or placebo for 10 weeks. All patients received fluvoxamine (100 mg/day) for the first 4 weeks, followed by 200 mg/day for the rest of the trial, regardless of their treatment groups. Participants were evaluated using the Yale–Brown Obsessive Compulsive Scale (Y‐BOCS). The main outcome measure was to assess the efficacy of minocycline in improving the OCD symptoms.
Results
General linear model repeated measures demonstrated significant effect for time × treatment interaction on the Y‐BOCS total scores, F(1.49, 137.93) = 7.1,
P
= 0.003, and Y‐BOCS Obsession subscale score, F(1.54, 141.94) = 9.72, P = 0.001, and near significant effect for the Y‐BOCS Compulsion subscale score, F(1.27, 117.47) = 2.92,
P
= 0.08. A significantly greater rate of partial and complete response was observed in the minocycline group (P < 0.001). The frequency of side‐effects was not significantly different between the treatment arms.
Conclusion
The results of this study suggest that minocycline could be a tolerable and effective adjuvant in the management of patients with OCD.
There is a concept in graph theory known as a chord which has not been considered before in relation to trapping sets of Tanner graphs. A chord of a cycle is an edge outside the cycle which connects ...two vertices of that cycle. It is proved that short cycles with a chord are the root of several trapping sets and eliminating them increases the minimum distance d min of a code. We provide new analytic lower bounds on d min of LDPC codes with girths 6 and 8 and column weight γ in which the short cycles are all chordless. We prove, analytically, that d min ≥ 2γ for girth 6 and d min ≥ 3(γ-1) 2 /γ ln γ-γ+1 for girth 8. Comparing these bounds with the existing bound γ + 1 for girth-6 LDPC codes shows the positive and significant influence of eliminating these cycles. A method to construct protograph-based LDPC codes with different girths and free of short cycles with a chord is given which is applicable to any type of protographs, simple and multi-edge, regular and irregular. The conditions to remove small trapping sets from the Tanner graph of a multi-edge QC-LDPC code are given. Numerical results indicate that the application of our method to QC-LDPC codes improves existing results.
The Internet of Things (IoT) is an emerging technology that can benefit from cloud infrastructure. In a cloud-based IoT network, a variety of data is collected by smart devices and transmitted to a ...cloud server. However, since the data may contain sensitive information about individuals, providing confidentiality and access control is essential to protect the users' privacy. Attribute-based encryption (ABE) is a promising tool to provide these requirements. However, most of ABE schemes neither provide efficient encryption and decryption mechanisms nor offer flexible and efficient key delegation and user revocation approaches. In this paper, to address these issues, we propose a lightweight revocable hierarchical ABE (LW-RHABE) scheme. In our scheme, computation overhead on the user side is very efficient, and most of the computational operations are performed by the cloud server. Also, using the hierarchical model, our scheme offers flexible and scalable key delegation and user revocation mechanisms. Indeed, in our scheme, key delegation and user revocation associated with each attribute can be handled by several key authorities. We provide the security definition for LW-RHABE, and we prove its security in the standard model and under the hardness assumption of the decisional bilinear Diffie-Hellman (DBDH) problem.
An approach to improve the performance of QC-LDPC codes is the removal of harmful trapping sets by increasing the girth. However, constructing these LDPC codes with large column weights and girth ...more than 8 is not easy. We are concerned with protograph-based LDPC codes with large column weights and free of small size trapping sets. We use the edge-coloring technique and some concepts from graph theory such as rainbow cycles to show that for large column weights the removal of all 8-cycles but the ones we call <inline-formula> <tex-math notation="LaTeX">\textit {rainbow 8-cycle} </tex-math></inline-formula> causes the elimination of several small size trapping sets. We provide a detailed theoretical analysis of these harmful trapping sets. Then, we apply them to array-based LDPC codes to significantly simplify and optimize the necessary and sufficient conditions to eliminate those 8-cycles from the Tanner graph. The given exponent matrices and simulation results show the impact of this simplification and the removal of the above mentioned 8-cycles.
In this paper, we propose new constructions for regular girth-8 quasi-cyclic low-density parity-check (QC-LDPC) codes based on circulant permutation matrices (CPM). The constructions assume ...symmetries in the structure of the parity-check matrix and employ a greedy exhaustive search algorithm to find the permutation shifts of the CPMs. As a result of symmetries, the new codes have a more compact representation compared with their counterparts. In majority of cases, also, they achieve the girth 8 at a shorter block length for the same degree distribution (code rate). Deterministic (explicit) constructions are also presented to expand the proposed parity-check matrices to larger block lengths and higher rates. The proposed long high-rate codes are often substantially shorter than regular girth-8 QC-LDPC codes of similar rate in the literature. Simulation results demonstrate that the proposed symmetric codes have competitive performance in comparison with similar existing QC-LDPC codes that lack symmetry.
In this letter, for the first time, an edge-coloring technique is proposed to characterize a certain elementary trapping set (ETS) and to obtain sufficient conditions to avoid small ETSs from ...occurrence in the Tanner graph of SC-LDPC convolutional codes. This technique is applicable to all protograph-based LDPC codes with different girths whose protographs are single-edge, that is, the entries of their base matrices are 0, 1. To further demonstrate the effectiveness of our proposed technique, we apply it to Time-Invariant SC-LDPC-CCs with girths 6 and 8 and column weights up to 5.
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