Improving Detection Method for Covert Channel in TCP/IP Network

ABSTRACT: Covert channels use stealth communications to compromise the security policies of systems. They constitute an important security threat since they can be used to exfiltrate confidential data from networks. TCP/IP protocols are used every day and are subject to covert channels problems. Covert channels are used for the secret transfer of information. Encryption only protects communication from being decoded by unauthorized parties, whereas covert channels aim to hide the very existence of the communication. Initially, covert channels were identified as a security threat on monolithic systems i.e. mainframes. More recently focus has shifted towards covert channels in computer network protocols. The huge amount of data and vast number of different protocols in the Internet seems ideal as a high-bandwidth vehicle for covert communication. The aim of this paper is to give an overview of covert channels in TCP/IP networks. We briefly describe the TCP and IP protocols, the methods to set them up in TCP/IP networks; then we study the methods to detect covert channels

Chern-Simons Invariants of Torus Links

We compute the vacuum expectation values of torus knot operators in Chern-Simons theory, and we obtain explicit formulae for all classical gauge groups and for arbitrary representations. We reproduce a known formula for the HOMFLY invariants of torus links and we obtain an analogous formula for Kauffman invariants. We also derive a formula for cable knots. We use our results to test a recently proposed conjecture that relates HOMFLY and Kauffman invariants.Comment: 20 pages, 5 figures; v2: minor changes, version submitted to AHP. The final publication is available at http://www.springerlink.com/content/a2614232873l76h6

Formate overflow drives toxic folate trapping in MTHFD1 inhibited cancer cells

Cancer cells fuel their increased need for nucleotide supply by upregulating one-carbon (1C) metabolism, including the enzymes methylenetetrahydrofolate dehydrogenase-cyclohydrolase 1 and 2 (MTHFD1 and MTHFD2). TH9619 is a potent inhibitor of dehydrogenase and cyclohydrolase activities in both MTHFD1 and MTHFD2, and selectively kills cancer cells. Here, we reveal that, in cells, TH9619 targets nuclear MTHFD2 but does not inhibit mitochondrial MTHFD2. Hence, overflow of formate from mitochondria continues in the presence of TH9619. TH9619 inhibits the activity of MTHFD1 occurring downstream of mitochondrial formate release, leading to the accumulation of 10-formyl-tetrahydrofolate, which we term a 'folate trap'. This results in thymidylate depletion and death of MTHFD2-expressing cancer cells. This previously uncharacterized folate trapping mechanism is exacerbated by physiological hypoxanthine levels that block the de novo purine synthesis pathway, and additionally prevent 10-formyl-tetrahydrofolate consumption for purine synthesis. The folate trapping mechanism described here for TH9619 differs from other MTHFD1/2 inhibitors and antifolates. Thus, our findings uncover an approach to attack cancer and reveal a regulatory mechanism in 1C metabolism.In this study, Green, Marttila, Kiweler et al. characterize one-carbon metabolism rewiring in response to a dual MTHFD1 and MTHFD2 inhibitor. This work provides insight into one-carbon fluxes, and reveals a previously uncharacterized vulnerability in cancer cells created by folate trapping

Pharmacological targeting of MTHFD2 suppresses acute myeloid leukemia by inducing thymidine depletion and replication stress

The folate metabolism enzyme MTHFD2 (methylenetetrahydrofolate dehydrogenase/cyclohydrolase) is consistently overexpressed in cancer but its roles are not fully characterized, and current candidate inhibitors have limited potency for clinical development. In the present study, we demonstrate a role for MTHFD2 in DNA replication and genomic stability in cancer cells, and perform a drug screen to identify potent and selective nanomolar MTHFD2 inhibitors; protein cocrystal structures demonstrated binding to the active site of MTHFD2 and target engagement. MTHFD2 inhibitors reduced replication fork speed and induced replication stress followed by S-phase arrest and apoptosis of acute myeloid leukemia cells in vitro and in vivo, with a therapeutic window spanning four orders of magnitude compared with nontumorigenic cells. Mechanistically, MTHFD2 inhibitors prevented thymidine production leading to misincorporation of uracil into DNA and replication stress. Overall, these results demonstrate a functional link between MTHFD2-dependent cancer metabolism and replication stress that can be exploited therapeutically with this new class of inhibitors

Chemical Composition and Characterization of Hemp (Cannabis sativa) Seed oil and essential fatty acids by HPLC Method

ABSTRACT The hemp ( cannabis sativa

Synthesis, crystal structure and characterization of Na_2.02Ag_5.98[GaSiO₄]₆(NO₂)₂and Na_3.12K_4.88[GaSiO₄]₆(NO₂)₂ sodalites

563-567Partially exchanged silver and potassium derivatives of Na8[GaSiO4]6(NO2)2 sodalite, Na2.02Ag5.98[GaSiO4]6(NO2)2 and Na3.12K4.88[GaSiO4]6(NO2)2, have been studied. The nitrite sodalite of the composition, Na8[GaSiO4]6(NO2)2 was prepared at low temperature by hydrothermal technique and the derivatives Na2.02Ag5.98[GaSiO4]6(NO2)2 and Na3.12K4.88[GaSiO4]6(NO2)2, were obtained by cation exchange method at 373 K. These products crystallize with the cubic sodalite structure in the space group P43n and profile refinement of powder X-ray data has been completed. The products obtained were studied by different investigative techniques like IR spectroscopy, X-ray powder diffraction, UV-DRS and SEM. FTIR study shows shift in absorption frequency for the exchange of silver and potassium derivatives. The unit cell parameters (a) are found to be 8.9328, 8.9838 and 9.0409 Å for silver, sodium and potassium sodalites, respectively, while the bond distances and bond angles are modified considerably. UV-DRS study shows shift in bands and change in band gap energy of these sodalite derivatives. SEM shows surface morphology of these sodalites

Synthesis and characterization of gallosilicate halide sodalites using organic solvent

1047-1051The crystallization of gallosilicate sodalite containing halides (Cl, Br and I) in 30% ethanol have been investigated at low temperature (373 K) using one pot synthesis method. X-ray powder diffraction, IR, FAR IR, 29Si and 23Na MAS NMR, SEM and thermogravimetric data are used to characterize these sodalites. The crystal structures show cubic symmetry in a space group P3n. The crystal structures have been refined by Rietveld refinement method. The unit cell parameter, a = 8.9502, 8.9986 and 9.0779 Å and the corresponding Ga-O-Si angle are found to be 134.453, 135.252 and 136.887o for chloro, bromo and iodo sodalite respectively. The MAS NMR data confirm the alternating Ga and Si ordering of sodalite framework. TGA analysis shows stability of guest anions in the sodalite framework

Calcined eggshell as a cost effective material for removal of dyes from aqueous solution

Abstract The removal of Rhodamine B, Eriochrome black T and Murexide dyes from aqueous solutions using calcined eggshell powder were investigated. In this study, calcined eggshell powder was applied for its potential use as an adsorbent for the removal of Rhodamine B, Eriochrome black T and Murexide dyes from their aqueous solutions. The calcined eggshell powder obtained was characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). The various parameters such as initial concentration, pH, adsorbent dose and contact time were studied. Various isotherms including Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models were applied for the equilibrium adsorption data. The kinetic study of Rhodamine B, Eriochrome black T and Murexide dyes on calcined eggshell powder follows pseudo-second order kinetics