47 research outputs found

    Ruling out Strongly Interacting Dark Matter-Dark Radiation Models from Joint Cosmic Microwave Background-Quasar Observations

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    The cold dark matter (CDM) paradigm provides a remarkably good description of the Universe's large-scale structure. However, some discrepancies exist between its predictions and observations at very small sub-galactic scales. To address these issues, the consideration of a strong interaction between dark matter particles and dark radiation emerges as an intriguing alternative. In this study, we explore the constraints on those models using joint observations of Cosmic Microwave Background (CMB) and Quasars with our previously built parameter estimation package CosmoReionMC. At 2-σ\sigma confidence limits, this analysis rules out all strongly interacting Dark Matter - Dark Radiation models proposed to date, representing the most stringent constraint on those models to the best of our knowledge. Future research using a 21-cm experiment holds the potential to reveal stronger constraints or uncover hidden interactions within the dark sector.Comment: Submitted to MNRAS Letter

    Magnetodielectric effect in nickel nanosheet-Na-4 mica composites

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    Nickel nanosheets of thickness 0.6 nm were grown within the nanochannels of Na-4 mica template. The specimens show magnetodielectric effect at room temperature with a change of dielectric constant as a function of magnetic field, the electric field frequency varying from 100 to 700 kHz. A decrease of 5% in the value of dielectric constant was observed up to a field of 1.2 Tesla. This is explained by an inhomogeneous two-component composite model as theoretically proposed recently. The present approach will open up synthesis of various nanocomposites for sensor applications.Comment: 11 pages, 7 figure

    Sensing behaviour of some nanocomposite systems

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    Silver nanoparticles of diameters 3.4 to 13.2 nm grown at the interfaces between silicate glass and some oxide crystallites exhibited about six orders of magnitude reduction in resistivity for a relative humidity change from 25% to 80%. Sn-SnO2 nano core-shell structure prepared within a gel-derived silica glass film by electrodeposition technique followed by heat treatment showed large change in resistivity as a function of humidity. The resistivity also changed due to gas flow of CO2, C2H5OH and NO2, respectively. The latter arose because of reduction/oxidation of Sn4+/Sn2+ species present at the shell layer of the nanostructures. Nickel nanosheets of thickness ~0.6 nm grown within the interlayer spaces of Na-4 mica crystallites showed a change of dielectric permittivity (5%) for an applied magnetic field of 1.2 Tesla. An inhomogeneous model was used to explain this behavior. Two dimensional CuO phase was grown within the channels of diameter ~5 nm of mesoporous SiO2 structure. A magnetodielectric (MD) parameter M.D. of 4.4% was obtained in this case. BaTiO3 nanoparticles of diameter ~25 nm having pores with diameter 10 nm showed multiferroic behavior which arose due to the presence of oxygen vacancies as a result of large surface area present. An M.D. parameter of 11% was found. Similarly mesoporous LiNbO3 of 10 nm diameter showed an M.D. parameter of ~4.5% at a magnetic field 1 Tesla. A giant magnetocapacitance effect with a value of 44% at 1.5 T was observed in nickel zinc ferrite (NZF) impregnated mesoporous silica. A magnetocapacitance of 51% at magnetic field 1.7 T was found in the case of nanocomposites comprising of iron ion containing silica based nanoglass and mesoporous silica. In the last two examples the behavior was explained on the basis of Catalan model of space-charge polarization with extracted values of magnetoresistance of the NZF and nanoglass phases being 58%

    Enhanced magnetic anisotropy of Nickel nanosheet prepared in Na-4 mica

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    Nanosheets of nickel with thickness equal to 0.6 nm have been grown within the interlayer spaces of Na-4 mica. The sheets are made up of percolative clusters of nanodisks. Magnetization characteristics indicate a superparamagnetic behavior with a blocking temperature of 428 K.The magnetic anisotropy constant as extracted from the coercivity data has been found to be higher than that of bulk nickel by two orders of magnitude. This is ascribed to a large aspect ratio of the nickel nanophase. The Bloch exponent is also found to be considerably different from that of bulk nickel because of a size effect. The Bloch Equation is still found to be valid for the two dimensional structures.Comment: 14 pages, 9 figure

    Ferromagnetic behavior of ultrathin manganese nanosheets

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    Ferromagnetic behaviour has been observed experimentally for the first time in nanostructured Manganese. Ultrathin (\sim 0.6 nm) Manganese nanosheets have been synthesized inside the two dimensional channels of sol-gel derived Na-4 mica. The magnetic properties of the confined system are measured within 2K-300K temperature range. The confined structure is found to show a ferromagnetic behaviour with a nonzero coercivity value. The coercivity value remains positive throughout the entire temperature range of measurement. The experimental variation of susceptibility as a function of temperature has been satisfactorily explained on the basis of a two dimensional system with a Heisenberg Hamiltonian involving direct exchange interaction.Comment: 13 pages, 9 figure

    Carriage and within-host diversity of mcr-1.1-harboring Escherichia coli from pregnant mothers: inter- and intra-mother transmission dynamics of mcr-1.1

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    Exchange of antimicrobial resistance genes via mobile genetic elements occur in the gut which can be transferred from mother to neonate during birth. This study is the first to analyze transmissible colistin resistance gene, mcr, in pregnant mothers and neonates. Samples were collected from pregnant mothers (rectal) and septicaemic neonates (rectal & blood) and analyzed for presence of mcr, its transmissibility, genome diversity, and exchange of mcr between isolates within an individualand across different individuals (not necessarily mother-baby pairs). mcr-1.1 was detected in rectal samples of pregnant mothers (n=10, 0.9%), but not in neonates. All mcr-positive mothers gave birth to healthy neonates from whom rectal specimen were not collected. Hence, transmission of mcr between these mother-neonate pairs could not be studied. mcr-1.1 was noted only in Escherichia coli (phylogroup A & B1), and carried few resistance and virulence genes. Isolates belonged to diverse sequence types (n=11) with two novel STs (ST12452, ST12455). mcr-1.1 was borne on conjugative IncHI2 bracketed between ISApl1 on Tn6630, and the plasmids exhibited similarities in sequences across the study isolates. Phylogenetic comparison showed that study isolates were related to mcr-positive isolates of animal origin from Southeast Asian countries. Spread of mcr-1.1 within this study occurred either via similar mcr-positive clones or similar mcr-bearing plasmids in mothers. Though this study could not build evidence for mother-baby transmission, but presence of such genes in the maternal specimen may enhance the chances of transmission to neonates

    The human checkpoint sensor Rad9–Rad1–Hus1 interacts with and stimulates DNA repair enzyme TDG glycosylase

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    Human (h) DNA repair enzyme thymine DNA glycosylase (hTDG) is a key DNA glycosylase in the base excision repair (BER) pathway that repairs deaminated cytosines and 5-methyl-cytosines. The cell cycle checkpoint protein Rad9–Rad1–Hus1 (the 9-1-1 complex) is the surveillance machinery involved in the preservation of genome stability. In this study, we show that hTDG interacts with hRad9, hRad1 and hHus1 as individual proteins and as a complex. The hHus1 interacting domain is mapped to residues 67–110 of hTDG, and Val74 of hTDG plays an important role in the TDG–Hus1 interaction. In contrast to the core domain of hTDG (residues 110–308), hTDG(67–308) removes U and T from U/G and T/G mispairs, respectively, with similar rates as native hTDG. Human TDG activity is significantly stimulated by hHus1, hRad1, hRad9 separately, and by the 9-1-1 complex. Interestingly, the interaction between hRad9 and hTDG, as detected by co-immunoprecipitation (Co-IP), is enhanced following N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) treatment. A significant fraction of the hTDG nuclear foci co-localize with hRad9 foci in cells treated with methylating agents. Thus, the 9-1-1 complex at the lesion sites serves as both a damage sensor to activate checkpoint control and a component of the BER

    A scoping review and thematic analysis of social and behavioural research among HIV-serodiscordant couples in high-income settings.

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    CAPRISA, 2015.Abstract available in pdf

    Essays on Resilience in the Face of Adversity

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    Organizations often experience adversity, which can be “an unfortunate event or circumstance or the state of serious and continued difficulty” (Tian and Fan 2014, p. 252); yet few successfully overcome such adversity. This dissertation focuses on identifying the factors that help organizations overcome adversity and become resilient. In Essay 1, I consider multilateral co-branding alliances (MCAs)—three or more independent firms operating under a single alliance brand while retaining their own individual brands. Although firms can gain significant value from participating in MCAs, disruptive events can undermine this value and make it unattractive for the alliance members to continue their participation. I investigate one such alliance disruption undermining the value of the common brand, and whether rebranding an MCA after a brand harm crisis can increase member firm extendedness—their continued participation in the alliance. I also evaluate the how the individual members’ “shadow of the past” i.e. their idiosyncratic experience with the alliance brand—explains the variation their extendedness. In Essay 2, I focus on multinational enterprises’ international expansion aspirations. MNEs often depend on physical locations owned and operated by host country local partners. Both parties have a vested interest in outlets shedding their early-stage vulnerability and transitioning to maturity. Maturity, however, does not confer immunity from sudden dips in sales that all outlets experience. The most severe of these—what I term a setback—might even pose an existential threat to the outlet. I identify the factors driving outlets’ resilience⸺ the likelihood and speed of their recovery from setback. I posit that the firm and its local partners’ ability and motivation to leverage the resources conferred by incubation (time spent in each phase of the lifecycle), imprinting (the outlets’ performance in their early days), learning (specifically from other outlets worldwide that have gone concurrently into setback), and incentives (elicited by the royalty regime) determine setback-experiencing outlets’ resilience. My research thus helps augment our understanding of organizational resilience, which is not just advantageous, but crucial for the organizations to ensure their long-term success, and the ability to thrive amidst adversity

    Memory, Trauma and Partition: Reading Sunanda Sikdar’s Dayamoyeer Katha

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    In recent years the scholastic emphasis on the refugee narratives, which conventionally focused on the loss of lives, homes and resources, is now reimagined as stories of survival and resurrection of people deprived of their homes. Nostalgia for a lost homeland often takes centre stage in refugee narratives. To be physically severed from a space internalised as the safest eternal abode and start afresh is a daunting task. Anchita Ghatak’s translation of Sunanda Sikdar’s Dayamoyeer Katha, A Life Long Ago narrates the life events of Dayamoyee, who chooses to revisit her past, deciding to write about the first ten years of her life in the East Pakistan village of Dighpait following the death of Majamda, a Muslim brotherly figure who sells his cows to come and meet her in India. The return to her childhood’s blissful land unearthed several hidden memories that brought the politics of religion, caste, class, and gender to the forefront. Without paying attention to her aunt’s continuous warnings not to mingle with the Muslim neighbours, Daya found it possible to eat, touch, and have fun with them in her childlike innocence. As the refugees arrive at Dighpait, her aunt remains unwilling to equate them with the native Muslim folk, the ‘bhoomiputra, the “sons of the soil”. Besides the narrator, we also have Snehalata, Daya’s aunt, her foster mother and a child widow. As she narrates how she grieved over the withdrawal of fish and other materialistic pleasures from her daily life rather than her young husband’s demise, we are reminded of the unfair austerity imposed on them in contrast to the elderly widowers who had no restrictions and even remarried occasionally. Characters like Modi bhabi, the woman who lost her mind as her childhood companion Suresh Lahiri left for Hindustan; Mejobhabi, wife of Khalek, who had to be ‘modernised’ to join her husband, now a senior army officer in Pakistan; Sudhirdada, the effeminate male whose murder portrays a show of power in the village, and Gouri, an instance of widow-remarriage needs scholarly attention. The novel further mentions Daya’s mother, the headmistress of a school in Hindustan, and Anita, a leading actress opposite Kishore Kumar, thus representing the educated, empowered women. The very moment of Daya deciding to write about her past is auspicious; it is the moment of finding one’s voice, of illuminating the horrors of the past, and the moment of triumph and healing. Dipesh Chakraborty mentions two aspects of memory: “the sentiment of nostalgia” and the “sense of trauma”, which pervades Dayamoyee’s narrative, but for her, it is equally therapeutic. The proposed paper looks forward to understanding Daya’s notion of her lost motherland and childhood and how the marginalised gender conceptualises home and rootedness. It proposes to analyse the politics of remembering, forgetting and retelling the stories from the point of the female subaltern who consciously buried her past and later chose to speak up, and in the process, portrayed a realistic picture of women during partition
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