1,803,686 research outputs found
Rb-Sr dataset.xlsx
No full textRb-Sr dataset for manuscript entitled `Calibration methods for laser ablation Rb-Sr geochronology: comparisons and recommendation based on NIST glass and natural reference materials`</p
Absolute Absorption and Dispersion in a Thermal Rb Vapour at High Densities and High Magnetic Fields.
Full text linkThis thesis presents a comparative study of the measured and calculated absolute absorption and dispersion properties of the Rb D lines through a dense thermal vapour in the absence and presence of an applied magnetic field. A detailed theoretical model valid in the weak-probe regime is calculated. The model uses a matrix representation of the atomic Hamiltonian including the magnetic field interaction for Rb in the completely uncoupled basis. Numerical diagonalisation allows the frequency detunings and transition strengths to be calculated. The lineshape of each transition is modelled as a Voigt profile, a convolution of the inhomogeneous and homogeneous profiles. The medium’s susceptibility is found by summing over all the electric-dipole-allowed transitions. For dense thermal vapours a modification to the homogeneous linewidth of each transition, which grows linearly with the number density of atoms, arises due to resonant dipole-dipole interactions between identical atoms in superpositions of the ground and excited terms. In the presence of an applied magnetic field we investigate the Stokes parameters of light propagating through a dense thermal vapour. For fields larger than 0.33 T we enter the hyperfine Paschen-Back regime on the Rb D lines. We present a compact optical isolator based on an atomic vapour, exploiting the spectral region of high transmission and large dispersion where we would normally expect absorption on the Rb D lines. Frequency up-conversion is shown in the fluorescence measurements over the visible and near infra-red regions for strong excitation. Low density transfer arises due to the energy-pooling effect between two identical atoms in their first excited terms. At
high densities resonant dipole-dipole interactions give rise to a threshold for the energy transfer. We characterise the threshold behaviour with increasing number density
Feshbach spectroscopy of an ultracold Rb-Cs mixture
Full text linkThis thesis reports the observation of interspecies Feshbach resonances in an ultracold mixture of Rb and Cs atoms. A versatile combined magnetic and optical potential has been designed and constructed which is capable of bringing both and to degeneracy, and reaching high phase-space density in . High phase-space density mixtures are the first step required in the production of ultracold polar molecules, the topic of much current research.
The apparatus capitalises on the efficient capture of atoms by a magnetic trap from a magneto-optical trap, and the efficient sympathetic cooling of Cs by Rb therein. Upon transfer to the crossed optical dipole trap condensates in excess of atoms and approximately atoms are produced after direct evaporation and gravito-magnetic tilting of the potential. The observation of six interspecies - Feshbach resonances are reported, three of which had only been predicted theoretically, allowing testing and development of the theoretical model. Furthermore, the extrapolation of this model has predicted numerous Feshbach resonances between and , none of which have been experimentally observed prior to this work. The versatile nature of this apparatus is discussed, including the application of the current system to cooling of . Initial experiments observed seven interspecies resonances, including a broad s-wave resonance at a magnetic field of G which is in excellent agreement with the theoretical prediction. Further work has revealed that fourteen Feshbach resonances exist in the 0-700 G magnetic field range between and atoms in the and states, respectively. Several of these resonances would be ideal for magneto-association of RbCs molecules, prior to transfer to the rovibrational ground-state
Independent regulation of P53 stabilisation and activation after Rb deletion in primary epithelial cells
No full textWe have previously reported that deletion of the retinoblastoma gene Rb leads to rapid but transient p53 stabilisation. We investigated here the pathways involved. We show that upon Rb-deletion dysregulated E2F activates p19ARF expression that localises in the nucleoli. There it interacts with MDM2, leading to P53 stabilisation. At the same time, ATR is activated, activating CHK1 that may phosphorylate P53 but also contribute to inhibition of MnSOD expression leading to accumulation of ROS (reactive oxygen species) and subsequent DNA injury, which in turn maintains ATR/CHK1 activated. However, from 72 h after Rb deletion, NPM interacts with P19ARF and concomitantly the interaction between p19ARF and MDM2 decreases leading to a return to P53 degradation. This occurs despite the persistence of the DNA damage response pathways. We therefore observe in primary cells not subjected to exogenous gene expression or exogenous DNA damaging treatment, activation of 2 concomitant pathways of activation of P53 that are dealt with in independent manner: an oncogenic pathway with rapid activation of ARF which is 'switched off' downstream of p19ARF activation after 72 h of induction and a DNA damage response pathway keeping a low level of transcriptionally active P53 sufficient to deal with a physiological elevation of oxidative DNA injury. A possible connection between the two pathways is discussed
The role of the retinoblastoma protein (Rb) in the nuclear localization of BAG-1: implications for colorectal tumour cell survival
No full textAlthough the retinoblastoma susceptibility gene RB1 is inactivated in a wide variety of human cancers, the retinoblastoma protein (Rb) has been shown to be overexpressed in colon cancers, which is linked to the anti-apoptotic function of the protein. However, the mechanisms by which Rb regulates apoptosis are yet to be fully elucidated. We have established that Rb interacts with the anti-apoptotic BAG-1 (Bcl-2 associated athanogene-1) protein, and that a decrease in nuclear localization of BAG-1 is detectable when the interaction between Rb and BAG-1 is disrupted by expression of the E7 viral oncoprotein. Interestingly, although reported as deregulated in colorectal cancers, we have found that BAG-1 expression is also altered in small adenomas, where its localization was found to be predominantly nuclear. In addition, we have established that maintenance of high nuclear BAG-1 in vitro increases the resistance of adenoma-derived cells to g-radiation-induced apoptosis. Our work suggests a novel function for Rb, involving modulation of the subcellular localization of BAG-1. We have found predominant nuclear BAG-1 localization in small adenomas, and suggest that BAG-1 may promote colorectal tumour cell survival by making colonic epithelial cells less sensitive to DNA damage.<br/
RB-TnSeq data analysis of <i>Caulobacter crescentus</i>.
No full textList of essential, conditionally essential, conditionally beneficial, and conditionally detrimental genes found in the RB-TnSeq data of Caulobacter crescentus by measures of the total and unique counts. (XLSX)</p
RB-TnSeq data analysis of <i>Pseudomonas fluorescens</i>.
No full textList of essential, conditionally essential, conditionally beneficial, and conditionally detrimental genes found in the RB-TnSeq data of Pseudomonas fluorescens by measures of the total and unique counts. (XLSX)</p
RB-TnSeq data for the phage resistance landscape in Escherichia coli
No full textTransposon mutagenesis data (RB-TnSeq) for two strains of Escherichia coli exposed to diverse bacteriophage<br
RB-TnSeq of rhizosphere bacteria exposed to <i>T</i>. <i>atroviride</i> exudates.
No full textA) Overview of the strategy for RB-TnSeq profiling of rhizosphere bacteria in response to T. atroviride-spent media. Step 1. RB-TnSeq mutant libraries were grown in LB with kanamycin from archived glycerol stocks. 2. To obtain spent medium, T. atroviride was grown in Vogel’s Minimal Medium [64] for 72 hrs, then both control and inoculated media were passed through a 0.22 μm filter to remove fungal material. 3. Each bacterial RB-TnSeq library was grown in the presence of T. atroviride spent media or uninoculated media control. After the bacteria grew for 24 hrs samples were collected for genomic DNA extraction and BarSeq using primers to conserved sequences that flank the unique barcodes. 4. Gene fitness was calculated by comparing the barcode counts in each gene before (Time 0) and after growth in the experimental condition (Condition). B) For each bacterium, a heatmap of the main functions of genes with negative fitness when exposed to T. atroviride exudates (Fitness S1 Dataset and Fig 2A was constructed via BioRender (https://www.biorender.com), agreement number DV25LBKS04.</p
RB and Cdc2 expression in brain: correlations with 3H-thymidine incorporation and neurogenesis
No full textExpression of the cell cycle regulatory proteins RB and p34cdc2 was examined in the adult rat brain, with special emphasis on proliferation and neuronal differentiation in the hippocampal formation and olfactory bulb. RB-like immunoreactivity (RB-IR) was detected throughout the brain, with particularly intense staining observed in hippocampal pyramidal cells, pyriform cortex, and cerebellar Purkinje cells. Intense RB-IR and cdc2-IR were also detected in proliferating neuronal precursor cells in the subgranular region of the dentate gyrus and in the subependymal region extending from the anterior lateral ventricle into the olfactory bulb. Many of these cells developed into neurons as assessed by the expression of neuron-specific enolase (NSE) and, in the hippocampal formation, the expression of Fos-IR following pentylenetetrazol-induced seizure activity. A good correlation was observed between the number of proliferating cells expressing intense nuclear RB-IR staining and the number of thymidine-labeled cells that had differentiated into functional hippocampal neurons. A substantial decrease in RB-IR during differentiation was also observed and occurred prior to the expression of NSE. The possibility that the loss of RB may be necessary for neuronal differentiation to proceed is discussed.</jats:p
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