803 research outputs found
Experimental evaluation of long term evolution-based NC OFDM secondary-to-secondary interference
No full textScarcity of spectrum resources, inefficient spectrum usage and the inflexibility of the current spectrum assignment are few of the major roadblocks in the development of new wireless communication standards. Secondary spectrum sharing has become a viable solution to alleviate this problem. Secondary users are unlicensed devices that use opportunistic spectrum access to identify vacant frequency bins and thereby utilize the spectrum. For advanced wireless communication standards like the Long Term Evolution (LTE) which primarily calls for higher data rates, evaluation of design parameters for ensuring efficient coexistence of heterogeneous secondary users and guaranteeing acceptable minimum level of performance becomes essential. Additionally, the understanding of the interference between secondary users occupying adjacent frequency bands for their transmission is imperative. This thesis focuses on the coexistence of secondary users in the same band assuming that the primary spectrum is found available. By Implementing two Non Contiguous Orthogonal Frequency Division Multiplexing ( NC-OFDM) based secondary transmitters on a real time platform, the design parameters that need to be considered to ensure efficient coexistence have been identified and investigated. The performance degradations observed at a particular secondary link due to presence of another interfering secondary link occupying adjacent frequency bands for its transmission have also been studied. This thesis also focuses on implementation of algorithms to modify the existing NC-OFDM transmission at the secondary transmitter end to reduce its Interference effects on the other secondary links operating within the same band. The focus is on an LTE-based Secondary Non Contiguous Orthogonal Frequency Division Multiplexing Transceiver on a Real Time Platform developed by National Instruments. The various blocks needed to design a real time LTE based communications links are discussed. An experimental LTE-to-LTE interference analysis based on the Real Time Platform and the designed system is presented.M.S.Includes bibliographical referencesby Ajay Ramkumar Iye
Crystal structure of 2,4-bis(2-chlorophenyl)-7-tert-pentyl-3-azabicyclo[3.3.1]nonan-9-one
No full textThe title compound, C25H29Cl2NO, which is a chloro analog of 2,4-bis(2-bromophenyl)-7-(tert-pentyl)-3-azabicyclo[3.3.1]nonan-9-one [Park, Ramkumar & Parthiban (2012). Acta Cryst. E68, o2946], exists in a twin-chair conformation with an equatorial orientation of the 2-chlorophenyl groups. The tert-pentyl group on the cyclohexanone adopts an exocyclic equatorial position and is disordered between two orientations in a ratio 0.520 (8):0.480 (8). The crystal packing shows no directional contacts beyond van der Waals contacts
Regulation of senescence in cancer and aging
No full textCo-author Charusheila Ramkumar is a student in the Cell Biology program in the Graduate School of Biomedical Sciences (GSBS) at UMass Medical School.Senescence is regarded as a physiological response of cells to stress, including telomere dysfunction, aberrant oncogenic activation, DNA damage, and oxidative stress. This stress response has an antagonistically pleiotropic effect to organisms: beneficial as a tumor suppressor, but detrimental by contributing to aging. The emergence of senescence as an effective tumor suppression mechanism is highlighted by recent demonstration that senescence prevents proliferation of cells at risk of neoplastic transformation. Consequently, induction of senescence is recognized as a potential treatment of cancer. Substantial evidence also suggests that senescence plays an important role in aging, particularly in aging of stem cells. In this paper, we will discuss the molecular regulation of senescence its role in cancer and aging. The potential utility of senescence in cancer therapeutics will also be discussed
2,4-Bis(4-ethoxyphenyl)-7-methyl-3-azabicyclo[3.3.1]nonan-9-one
No full textThe molecule of the title compound, C25H31NO3, exists in a twin-chair conformation with an equatorial orientation of the 4-ethoxyphenyl groups, as observed for its ortho isomer [Parthiban, Ramkumar, Park & Jeong (2011b), Acta Cryst. E67, o1475–o1476]. The methyl and 4-ethoxyphenyl groups are also equatorially oriented on the bicycle, as in the ortho analogue. In particular, although the cyclohexanone ring deviates from an ideal chair, the piperidone ring is closer to an ideal chair, whereas in the ortho isomer both rings are significantly puckered and deviate from ideal chairs. The 4-ethoxyphenyl groups on both sides of the secondary amine group are oriented at an angle of 26.11 (3)° with respect to each other, but the 2-ethoxyphenyl groups in the ortho isomer are oriented by less than half this [12.41 (4)°]. In contrast to the absence of any significant interactions in the crystal packing of the ortho isomer, the title compound features N—H...O interactions, linking the molecules along the b axis
Templated self-assembly of nanoporous alumina : pore formation and ordering mechanisms, methodologies, and applications
No full textThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.MIT Institute Archives copy: p. 301-324 bound in reverse order.Includes bibliographical references (p. 309-324).Porous anodic aluminum oxide (AAO), also known as porous alumina, is a self-ordered nanostructured material well-suited for use in electronic, magnetic, optical and biological applications due to its small pore size (4-200nm) and spacing (10-500nm). Under slightly acidic conditions, both oxidation and dissolution of aluminum leads to the formation of pores. AAO pores form a self-assembled honey-comb structure with short range order over certain ranges of anodic potential and pH. In this work, three key results related to porous AAO science and technology are presented. First, a new theory based on strain-induced instability has been developed from the analysis of results obtained from kinetic studies and stress measurements to explain the formation of AAO pores. Experiments show that excess vacancies of aluminum, created by the dissolution process, generate a large tensile stress and an associated strain energy, which destabilizes the initially flat A1/AAO interface and leads to pore formation. Other factors affecting stability of the Al/AAO interface and the self-assembly process are also presented.(cont.) Second, templated self-assembly (TSA) of AAO pores, ordered over wafer-scale areas and with controlled spacing and symmetry, have been achieved by pre-patterning the substrate using interference lithography. TSA of AAO pores led to control of pore spacing and order symmetry in ranges not achievable without templating. Independent control of pore spacing and diameter were successfully demonstrated, allowing formation of novel 3-D nanostructures such as nanofunnels, fabricated using periodic variations in the anions and/or electrolyte pH. Using the TSA approach, AAO with ordered pores 50:1 were fabricated on Si substrates. A 1-D array of ordered pores, either in or out of plane with the substrate, was fabricated by confining the growth of AAO pores using silicon oxide masks patterned by lithography techniques. Finally, AAO templates were used to fabricate ordered nanostructures including carbon nanotubes, magnetic nanotubes and antidots, and metallic nanowires and nanoparticles, all of which display properties very different from their bulk counterparts.(cont.) These results, and other proposed methodologies, provide new techniques for controlled in-plane and out-of-plane growth and organization of nanotubes and nanowires on Si substrates.by Ramkumar Krishnan.Ph.D
Nasolacrimal duct obstruction: Does it really increase the risk of amblyopia in children?
No full textPurpose: To report the prevalence of amblyopia risk factors in children with congenital nasolacrimal duct obstruction. Methods: A retrospective review of records of children with the diagnosis of congenital nasolacrimal duct obstruction (NLDO), who underwent probing from January 2009 to October 2011, was done. All of them underwent a complete ophthalmic evaluation including cycloplegic refraction and strabismus evaluation before probing. Results: A total of 142 children were included in this study. The mean age at presentation was 22.38 months (sample standard deviation (SSD) - 15.88). Amblyopia risk factors were defined according to two sets of guidelines: The American Association for Pediatric Ophthalmology and Strabismus (AAPOS) referral criteria guidelines and the new AAPOS Vision Screening Committee guidelines. Twenty-eight (20%) children were found to have some form of amblyopia risk factor based on the referral criteria prescribed by AAPOS. However, on applying modified guidelines described by Donahue et al., to analyze the same cohort, 21 children were found to have amblyogenic risk factors. Of these 28 children, 13 had significant astigmatism (>1.50 D), 8 children had hypermetropia (>3.50 D), and six children had anisometropia (>1.50 D). One child had significant cataract (media opacity >1 mm). None of the children in this series had either myopia or strabismus. Conclusion: Prevalence of amblyopia risk factor was found to be 20% in our study based on the older guidelines; however, it reduces to 14.78% by applying the modified guidelines. Despite this reduction, importance of a comprehensive ophthalmic examination including cycloplegic refraction in all children presenting with NLDO cannot be overstated. A close follow-up of these children is also essential to prevent the development of amblyopia
Locally Recoverable Streaming Codes for Packet-Erasure Recovery
No full textStreaming codes are a class of packet-level erasure codes that are designed with the goal of ensuring recovery in low-latency fashion, of erased packets over a communication network. It is well-known in the streaming code literature, that diagonally embedding codewords of a [τ+1,τ+1-a] Maximum Distance Separable (MDS) code within the packet stream, leads to rate-optimal streaming codes capable of recovering from a arbitrary packet erasures, under a strict decoding delay constraint τ. Thus MDS codes are geared towards the efficient handling of the worst-case scenario corresponding to the occurrence of a erasures. In the present paper, we have an increased focus on the efficient handling of the most-frequent erasure patterns. We study streaming codes which in addition to recovering from a>1 arbitrary packet erasures under a decoding delay τ, have the ability to handle the more common occurrence of a single-packet erasure, while incurring smaller delay r<τ. We term these codes as (a,τ,r) locally recoverable streaming codes (LRSCs), since our single-erasure recovery requirement is similar to the requirement of locality in a coded distributed storage system. We characterize the maximum possible rate of an LRSC by presenting rate-optimal constructions for all possible parameters {a,τ,r}. Although the rate-optimal LRSC construction provided in this paper requires large field size, the construction is explicit. It is also shown that our (a,τ=a(r+1)-1,r) LRSC construction provides the additional guarantee of recovery from the erasure of h, 1 ≤ h ≤ a, packets, with delay h(r+1)-1. The construction thus offers graceful degradation in decoding delay with increasing number of erasures
RAMKUMAR MUKHAPADHYAYER ‘DHANAPATIR SINHALYATRA’ : NABARUPE CHANDIMANGAL/ রামকুমার মুখোপাধ্যায়ের ‘ধনপতির সিংহলযাত্রা’ : নবরূপে চন্ডীমঙ্গল
No full textoai:ojs2.tirj.org.in:article/2Ramkumar Mukherjee\u27s novel \u27Dhanpati\u27s Sinhala Yatra\u27 is also medieval in terms of language. The novel has been reimagined by Chandimangal. Ramkumar Mukherjee has adopted the first part of the narrative of the merchant section in his novel. From Dhanpati\u27s Sinhala Yatra to captivity. Here, the novelist has looked back at medieval Bengal and Bengalis from a distance of several centuries, keeping Mukund\u27s poetry in front of him. He has made no attempt to drag the past into the present. Nor has he taken the present into the past and placed it there. In this book, the past cannot be seen in the present and the present in the past. A pure historical setting has been created where there is no shadow of the twenty-first century. Chapters such as the lifting of the Saptadinga, Dhanpati\u27s journey to the Dingaghata, Ajay Yatra, Muktabeni, and the journey of rivers and streams describe extinct rivers, towns, etc. The novel contains themes such as mythological consciousness, religious ideals, and a reevaluation of divine consciousness. Dhanpati traveled to the southern country in the hope of prosperity. However, his fate and destiny were determined by the hideous plots and cruelty of two goddesses. Ignoring many ominous signs and the desperate pleas of Khulna, Dhanpati has to travel helplessly towards the inevitable end. This is his destiny. Ramkumar Mukherjee has presented the novel \u27Dhanpati\u27s Singhal Yatra\u27 in a magical bond of intense fascination with the tradition of Bengali cultural heritage. The novel has a unique and modern reconstruction of the well-known Afghan poem of the medieval \u27Chandimangal\u27. The novelist has kept the basic structure of the story intact here, but has analyzed the psychological depth of the characters and the socio-economic context of the time from a modern perspective. As a result, it emerges as a picture of the conflict between man and time instead of the story of the greatness of the Goddess. In the novel, Dhanpati is a prosperous merchant of Ujjainnagar, but he has endless questions and doubts about the social system of the time. He wants to magnify the efforts and logic of man instead of the miracles of the conventional gods and goddesses. This rational mind has taken him against the conventional beliefs and conventional customs. And later it has become the main reason for the conflict in his life. On the king\u27s orders, Dhanpati has to undertake a journey to Sinhala despite his reluctance. Before the journey, the wish of his husband for his well-being did not open, so when the puja of Goddess Chandi was organized, the rational, confident, and realistic leader trampled the auspicious place of the Goddess with contempt. To him, the greatness of the Goddess is irrational and miraculous. However, the author portrays this insult not only as an insult, but as a clash between traditional beliefs and modern logic. The novel is not just a religious story, but also a story of human survival in the face of adversity. Overall, the novel has become a reinterpretation of the medieval \u27Chandimangal\u27 poem
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