Kinetics of Length Scale Dependent Deformation of Gold Microspheres and Micropillars

In this thesis length and time scale dependence of the operative plastic deformation mechanisms in Au is studied. Uniaxial compression tests were performed at various loading rates on FIB-milled Au micropillars and single-crystalline Au microspheres of diameter ranging from 0.8 to 6.0 µm to investigate the incipient and bulk plasticity events. Constant-load ambient-temperature creep tests were performed on the micropillars to study the time-dependent plasticity at very slow strain rates. Uniaxial compression tests were also performed on coated Au microspheres to study the effect of extrinsic constraint on the deformation mechanisms. During uniaxial compression, both the Au micropillars and microspheres displayed strain jumps, the frequency of which decreased with increasing sample diameter and increasing resolved shear stress. The bulk flow stress, corresponding to 5% – 20% average compressive strain, was dependent upon both the strain rate and the specimen diameter. Analysis of the apparent activation volume, V*, and energy, Q*, of the deformation process indicated that the operative deformation mechanism for the small 0.8 µm diameter pillars and spheres was characteristic of a mechanism limited by surface nucleation of dislocations while larger diameter samples displayed values indicative of the more common dislocation-obstacle interaction limited deformation mechanism. The deformation-rate dependence of incipient plastic deformation of the Au micropillars and microspheres was also dependent upon the strain rate and sample diameter. For the smallest, sub-micrometer size, samples the incipient plasticity was controlled by heterogeneous dislocation nucleation events, while a dislocation-obstacle interaction limited glide process was found to be operative in the larger specimens. In the extrinsic constraint study, Au microspheres that were coated with a 40 – 80 nm thick Ni layer displayed a slightly increased flow stress compared to similar size uncoated microspheres. The estimated V* and Q* values for the coated microspheres suggest that the mechanism responsible for the initiation of first dislocation motion is essentially the same regardless of the presence of a constraining coating

Critical Role of Artificially Intelligent Conversational Chatbot

Artificially intelligent chatbot, such as ChatGPT, represents a recent and powerful advancement in the AI domain. Users prefer them for obtaining quick and precise answers, avoiding the usual hassle of clicking through multiple links in traditional searches. ChatGPT's conversational approach makes it comfortable and accessible for finding answers quickly and in an organized manner. However, it is important to note that these chatbots have limitations, especially in terms of providing accurate answers as well as ethical concerns. In this study, we explore various scenarios involving ChatGPT's ethical implications within academic contexts, its limitations, and the potential misuse by specific user groups. To address these challenges, we propose architectural solutions aimed at preventing inappropriate use and promoting responsible AI interactions.Comment: Extended version of Conversation 2023 position pape

Agrobacterium mediated genetic transformation and regeneration in elite rice (Oryza sativa L.) cultivar BRRI dhan56

Agrobacterium-mediated genetic transformation of rice (Oryza sativa L.) cultivar BRRI dhan56 was  carried out in this study. Agrobacterium tumefaciens strain LBA 4404, which harbors the plasmid pIG121  that carries the genes for ß-glucuronidase gene, served as a reporter gene in the histochemical assay and  the neomycin phosphotransferase ΙΙ (NPT ΙΙ) gene for the identification of resistance to kanamycin was  used for genetic transformation. Twenty days old embryogenic calli from mature embryos of highly  regenerating rice cultivar BRRI dhan56 were used to co-cultivate with 0.8 to 0.9 OD600 Agrobacterium  for 25 min and the cultured was continued on agar medium for this study. The transformed colonies were selected by using 50 mg/L kanamycin and 50 mg/L rifampicin and confirmed by colony PCR. The PCR  positive colonies were isolated to transform by using calli of indica rice cultivar BRRI dhan56. Putative  leaf and root segments from  plantlets obtained from transformation experiment with the plasmid pIG121  were GUS positive. Integration of the introduced gene into the genome was  demonstrated by PCR. The  maximum transformation efficiency of 32% was obtained by using 500 mg/L cefotaxime as a  bacteriostatic agent to inhibit growth of Agrobacterium. In this study, 100 µM acetosyringone in  co-cultivation medium and co-cultivation for 3 days were the optimum conditions for maximum  transformation. The expression of GUS gene revealed that the calli were successfully transformed. The  results of this study would be an effective tool for crop improvement and gene-function studies on the  model monocot plant rice. Key words: Agrobacterium, Oryza sativa L., acetosyringone, β-glucuronidase, cefotaxime, plasmid, phosphotransferase, rice, transformation. Abbreviation: GUS, β-Glucuronidase; PCR, polymerase chain reaction; MS, Murashige and Skoog; 2,4-D, 2,4-dichlorophenoxyacetic acid; MCI, callus induction medium; OD, optical density; NAA, 1-naphthaleneacetic acid; BAP, 6-benzylaminopurine. 

Peak to average power ratio analysis for LTE systems

The 3rd generation partnership project (3GPP) long term evolution (LTE) standard uses single carrier frequency division multiple access (SCFDMA) scheme for the uplink transmissions and orthogonal frequency division multiplexing access (OFDMA) in downlink. SCFDMA uses DFT spreading prior to OFDMA modulation to map the signal from each user to a subset of the available subcarriers i.e., single carrier modulation. The efficiency of a power amplifier is determined by the peak to average power ratio (PAPR) of the modulated signal. In this paper, we analyze the PAPR in 3GPP LTE systems using root raised cosine based filter. Simulation results show that the SCFDMA subcarrier mapping has a significantly lower PAPR compared to OFDMA. Also comparing the three forms of SCFDMA subcarrier mapping, results show that interleave FDMA (IFDMA) subcarrier mapping with proposed root raised cosine filter reduced PAPR significantly than localized FDMA (LFDMA) and distributed (DFDMA) mapping. This improves its radio frequency (RF) power amplifier efficiency and also the mean power output from a battery driven mobile terminal.<br /