Operational maps between molecular properties and environmental stress cracking resistance (ESCR)

This is the peer reviewed version of the following article: Sardashti, P., Stewart, K. M. E., Polak, M., Tzoganakis, C., & Penlidis, A. (2019). Operational maps between molecular properties and environmental stress cracking resistance. Journal of Applied Polymer Science, 136(4), 47006. https://doi.org/10.1002/app.47006, which has been published in final form at https://doi.org/10.1002/app.47006. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.Environmental stress cracking (ESC) is one of the main failure mechanisms involved in polymer fractures. This paper focusses on the environmental stress cracking resistance (ESCR) of polyethylene (PE) in which ESC occurs through a slow crack growth mechanism. In order to predict the ESCR of PE, it is necessary to fully understand the molecular structure of the resin. This paper demonstrates the relationships between molecular structure characteristics and material responses based on experimental characterization and published literature trends. Relationships between ESCR, molecular weight (MW), percentage crystallinity, and density were used to create ESCR and molecular structure maps, which can be used to improve the development of PE resins with a desirable (better/higher) ESCR. These maps along with a logical flow chart offer practical prescriptions and describe pathways towards the development of PE with a desirable ESCR. In addition, this paper presents case studies that demonstrate the effectiveness of this approach.The authors gratefully acknowledge financial support from the Natural Sciences and Engineering Research Council (NSERC) of Canada, the Canada Research Chair (CRC) program, and the Ontario Graduate Scholarship (OGS) program. Many thanks also go to Imperial Oil Limited, Sarnia, ON, Canada, for financial support and for providing resins for the study over many years

Touch\'e: Towards Ideal and Efficient Cache Compression By Mitigating Tag Area Overheads

Compression is seen as a simple technique to increase the effective cache capacity. Unfortunately, compression techniques either incur tag area overheads or restrict data placement to only include neighboring compressed cache blocks to mitigate tag area overheads. Ideally, we should be able to place arbitrary compressed cache blocks without any placement restrictions and tag area overheads. This paper proposes Touch\'e, a framework that enables storing multiple arbitrary compressed cache blocks within a physical cacheline without any tag area overheads. The Touch\'e framework consists of three components. The first component, called the ``Signature'' (SIGN) engine, creates shortened signatures from the tag addresses of compressed blocks. Due to this, the SIGN engine can store multiple signatures in each tag entry. On a cache access, the physical cacheline is accessed only if there is a signature match (which has a negligible probability of false positive). The second component, called the ``Tag Appended Data'' (TADA) mechanism, stores the full tag addresses with data. TADA enables Touch\'e to detect false positive signature matches by ensuring that the actual tag address is available for comparison. The third component, called the ``Superblock Marker'' (SMARK) mechanism, uses a unique marker in the tag entry to indicate the occurrence of compressed cache blocks from neighboring physical addresses in the same cacheline. Touch\'e is completely hardware-based and achieves an average speedup of 12\% (ideal 13\%) when compared to an uncompressed baseline.Comment: Keywords: Compression, Caches, Tag Array, Data Array, Hashin

Early stages of oxide growth in H-terminated silicon nanowires: determination of kinetic behavior and activation energy

Silicon nanowires (Si NWs) terminated with hydrogen atoms exhibit higher activation energy under ambient conditions than equivalent planar Si(100). The kinetics of sub-oxide formation in hydrogen-terminated Si NWs derived from the complementary XPS surface analysis attribute this difference to the Si-Si backbond and Si-H bond propagation which controls the process at lower temperatures (T = 200 degrees C), the activation energy was similar due to self-retarded oxidation. This finding offers the understanding of early-stage oxide growth that affects the conductance of the near-gap channels leading towards more efficient Si NW electronic devices

Oxide-free hybrid silicon nanowires: From fundamentals to applied nanotechnology

The ability to control physical properties of silicon nanowires (Si NWs) by designing their surface bonds is important for their applicability in devices in the areas of nano-electronics, nano-photonics, including photovoltaics and sensing. In principle a wealth of different molecules can be attached to the bare Si NW surface atoms to create e.g. Si-O, Si-C, Si-N, etc. to mention just the most prominent ones. Si-O bond formation, i.e. oxidation usually takes place automatically as soon as Si NWs are exposed to ambient conditions and this is undesired is since a defective oxide layer (i.e. native silicon dioxide - SiO2) can cause uncontrolled trap states in the band gap of silicon. Surface functionalization of Si NW surfaces with the aim to avoid oxidation can be carried out by permitting e.g. Si-C bond formation when alkyl chains are covalently attached to the Si NW surfaces by employing a versatile two-step chlorination/alkylation process that does not affect the original length and diameter of the NWs. Termination of Si NWs with alkyl molecules through covalent Si-C bonds can provide long term stability against oxidation of the Si NW surfaces. The alkyl chain length determines the molecular coverage of Si NW surfaces and thus the surface energy and next to simple Si-C bonds even bond types such as C=C and C=C can be realized. When integrating differently functionalized Si NWs in functional devices such as field effect transistors (FETs) and solar cells, the physical properties of the resultant devices vary. (C) 2013 Elsevier Ltd. All rights reserved

Antiretroviral drug resistance mutations among HIV treatment failure patients in Tehran, Iran

Background: This study aimed to determine drug resistance mutations in patients with virological failure and find correlation between HIV drug resistance test and viral load. Methods: Blood sample was collected from 51 patients who suspicious treatment failure in the center of Imam Khomeini Hospital, Tehran, Iran in 2015. Viral voluntary counseling and testing load test was done and the patients with viral load above 1000 copies choose for detection of drug resistance mutations by genotyping method (29 patients). Results: The majority of patients (82.75) harbored the HIV subtype CRF 35 A-D. The 86.2 patients compromised at least one resistance mutation. The analysis of reverse transcriptase showed M184V (68.9), T215YISF (44.8), K103N (27.6) and the analysis results of protease revealed G73SC (13.8) and I47VA (6.9). Eventually, the significant correlation between viral load and drug resistance was found. Conclusion: The result of our research stress the significance of recognizing drug resistant on time that prohibits the accumulation of drug resistance mutation and circulates the resistance strain of HIV-1 virus and the importance of national study according to the reliable findings for treatment guidelines. © 2017, Iranian Journal of Public Health. All rights reserved