Data Bit-Rate Instability in Wireless Multi-Rate Ad Hoc Networks

Wireless Ad-hoc single-rate environments typically use a Distance Vector routing with a metric based on the minimization of the hop-count. In practice, the technique of minimizing the distance does not reward in the case of multi-rate, therefore it may be prefereable touse protocols privileging the link's transmission speed instead of the minimum distance. Our study aims toward the stability of the link in a wireless high mobility environment; we explore and hypothesize how to privilege, in the choice of routes, the stablest link.Ad Hoc Networks; Routing; Stability.

Link Stability inWireless Multi-Rate Ad Hoc Networks

Wireless ad hoc single-rate environments typically use a Distance Vector routing with a metric based on hop-count minimization. In practice, the technique of minimizing the distance does not reward in the case of multirate, therefore it may be prefereable to use protocols privileging link stability instead of speed and minimum distance. We study link stability in a wireless high mobility environment and propose a Route Discovery mechanism privileging the stablest link.VPN; Network; Protocol.

Data Warehouse Design and Management: Theory and Practice

The need to store data and information permanently, for their reuse in later stages, is a very relevant problem in the modern world and now affects a large number of people and economic agents. The storage and subsequent use of data can indeed be a valuable source for decision making or to increase commercial activity. The next step to data storage is the efficient and effective use of information, particularly through the Business Intelligence, at whose base is just the implementation of a Data Warehouse. In the present paper we will analyze Data Warehouses with their theoretical models, and illustrate a practical implementation in a specific case study on a pharmaceutical distribution companyData warehouse, database, data model.

An Analisys of Business VPN Case Studies

A VPN (Virtual Private Network) simulates a secure private network through a shared public insecure infrastructure like the Internet. The VPN protocol provides a secure and reliable access from home/office on any networking technology transporting IP packets. In this article we study the standards for VPN implementation and analyze two case studies regarding a VPN between two routers and two firewalls.VPN; Network; Protocol.

ADP-ribose polymers localized on Ctcf–Parp1–Dnmt1 complex prevent methylation of Ctcf target sites

PARylation [poly(ADP-ribosyl)ation] is involved in the maintenance of genomic methylation patterns through its control of Dnmt1 [DNA (cytosine-5)-methyltransferase 1] activity. Our previous findings indicated that Ctcf (CCCTC-binding factor) may be an important player in key events whereby PARylation controls the unmethylated status of some CpG-rich regions. Ctcf is able to activate Parp1 [poly(ADP-ribose) polymerase 1], which ADP-ribosylates itself and, in turn, inhibits DNA methylation via non-covalent interaction between its ADP-ribose polymers and Dnmt1. By such a mechanism, Ctcf may preserve the epigenetic pattern at promoters of important housekeeping genes. The results of the present study showed Dnmt1 as a new protein partner of Ctcf. Moreover, we show that Ctcf forms a complex with Dnmt1 and PARylated Parp1 at specific Ctcf target sequences and that PARylation is responsible for the maintenance of the unmethylated status of some Ctcf-bound CpGs. We suggest a mechanism by which Parp1, tethered and activated at specific DNA target sites by Ctcf, preserves their methylation-free status

Parp1 Localizes within the Dnmt1 Promoter and Protects Its Unmethylated State by Its Enzymatic Activity

Aberrant hypermethylation of CpG islands in housekeeping gene promoters and widespread genome hypomethylation are typical events occurring in cancer cells. The molecular mechanisms behind these cancer-related changes in DNA methylation patterns are not well understood. Two questions are particularly important: (i) how are CpG islands protected from methylation in normal cells, and how is this protection compromised in cancer cells, and (ii) how does the genome-wide demethylation in cancer cells occur. The latter question is especially intriguing since so far no DNA demethylase enzyme has been found.Our data show that the absence of ADP-ribose polymers (PARs), caused by ectopic over-expression of poly(ADP-ribose) glycohydrolase (PARG) in L929 mouse fibroblast cells leads to aberrant methylation of the CpG island in the promoter of the Dnmt1 gene, which in turn shuts down its transcription. The transcriptional silencing of Dnmt1 may be responsible for the widespread passive hypomethylation of genomic DNA which we detect on the example of pericentromeric repeat sequences. Chromatin immunoprecipitation results show that in normal cells the Dnmt1 promoter is occupied by poly(ADP-ribosyl)ated Parp1, suggesting that PARylated Parp1 plays a role in protecting the promoter from methylation.In conclusion, the genome methylation pattern following PARG over-expression mirrors the pattern characteristic of cancer cells, supporting our idea that the right balance between Parp/Parg activities maintains the DNA methylation patterns in normal cells. The finding that in normal cells Parp1 and ADP-ribose polymers localize on the Dnmt1 promoter raises the possibility that PARylated Parp1 marks those sequences in the genome that must remain unmethylated and protects them from methylation, thus playing a role in the epigenetic regulation of gene expression

The impact of chest CT body composition parameters on clinical outcomes in COVID-19 patients

We assessed the impact of chest CT body composition parameters on outcomes and disease severity at hospital presentation of COVID-19 patients, focusing also on the possible mediation of body composition in the relationship between age and death in these patients. Chest CT scans performed at hospital presentation by consecutive COVID-19 patients (02/27/2020-03/13/2020) were retrospectively reviewed to obtain pectoralis muscle density and total, visceral, and intermuscular adipose tissue areas (TAT, VAT, IMAT) at the level of T7-T8 vertebrae. Primary outcomes were: hospitalization, mechanical ventilation (MV) and/or death, death alone. Secondary outcomes were: C-reactive protein (CRP), oxygen saturation (SO2), CT disease extension at hospital presentation. The mediation of body composition in the effect of age on death was explored. Of the 318 patients included in the study (median age 65.7 years, females 37.7%), 205 (64.5%) were hospitalized, 68 (21.4%) needed MV, and 58 (18.2%) died. Increased muscle density was a protective factor while increased TAT, VAT, and IMAT were risk factors for hospitalization and MV/death. All these parameters except TAT had borderline effects on death alone. All parameters were associated with SO2 and extension of lung parenchymal involvement at CT; VAT was associated with CRP. Approximately 3% of the effect of age on death was mediated by decreased muscle density. In conclusion, low muscle quality and ectopic fat accumulation were associated with COVID-19 outcomes, VAT was associated with baseline inflammation. Low muscle quality partly mediated the effect of age on mortality.We assessed the impact of chest CT body composition parameters on outcomes and disease severity at hospital presentation of COVID-19 patients, focusing also on the possible mediation of body composition in the relationship between age and death in these patients. Chest CT scans performed at hospital presentation by consecutive COVID-19 patients (02/ 27/2020-03/13/2020) were retrospectively reviewed to obtain pectoralis muscle density and total, visceral, and intermuscular adipose tissue areas (TAT, VAT, IMAT) at the level of T7-T8 vertebrae. Primary outcomes were: hospitalization, mechanical ventilation (MV) and/or death, death alone. Secondary outcomes were: C-reactive protein (CRP), oxygen saturation (SO2), CT disease extension at hospital presentation. The mediation of body composition in the effect of age on death was explored. Of the 318 patients included in the study (median age 65.7 years, females 37.7%), 205 (64.5%) were hospitalized, 68 (21.4%) needed MV, and 58 (18.2%) died. Increased muscle density was a protective factor while increased TAT, VAT, and IMAT were risk factors for hospitalization and MV/death. All these parameters except TAT had borderline effects on death alone. All parameters were associated with SO2 and extension of lung parenchymal involvement at CT; VAT was associated with CRP. Approximately 3% of the effect of age on death was mediated by decreased muscle density. In conclusion, low muscle quality and ectopic fat accumulation were associated with COVID-19 outcomes, VAT was associated with baseline inflammation. Low muscle quality partly mediated the effect of age on mortality