The Large Hadron Collider (LHC) in the High Luminosity (HL-LHC) era will be upgraded to deliver instantaneous luminosities up to 5×1034cm−2s−1, five times more than the original design value. In ...order to maintain performance of the Compact Muon Solenoid (CMS) Experiment under these conditions, ME0 is one of the new muon detectors to be added, along with GE1/1, GE2/1, RE3/1 and RE4/1. ME0 uses the triple Gas Electron Multiplier (GEM) technology and is designed to cover the far-forward region of 2.0<|η|<2.8. The readout electronics for ME0 must be designed to deal with high data rates and be sufficiently radiation hard to operate very close to the beamline. The design and development status of the readout electronics for ME0 are presented, along with recent results from integration tests performed using the latest electronics prototypes with GEM chambers.
The Kepler satellite has provided photometric timeseries data of unprecedented length, duty cycle and precision. To fully analyse these data for the tens of thousands of stars observed by Kepler, ...automated methods are a prerequisite. Here, we present an automated procedure to determine the period spacing of gravity modes in red giant stars ascending the red giant branch. The gravity modes reside in a cavity in the deep interior of the stars and provide information on the conditions in the stellar core. However, for red giants the gravity modes are not directly observable on the surface, hence this method is based on the pressure-gravity mixed modes that present observable features in the Fourier power spectrum. The method presented here is based on the vertical alignment and symmetry of these mixed modes in a period echelle diagram. We find that we can obtain reliable results for both model frequencies and observed frequencies. Additionally, we carried out Monte Carlo tests to obtain realistic uncertainties on the period spacings with different set of oscillation modes (for the models) and uncertainties on the frequencies. Furthermore, this method has been used to improve mode detection and identification of the observed frequencies in an iterative manner.
Associated production of the Higgs boson with a top quark-antiquark pair (ttH) provides the best direct probe of the top-Higgs Yukawa coupling at tree-level, and increasingly precise measurements of ...its production cross section are a major ongoing thrust at the CMS experiment. They are being performed in several decay channels for the Higgs boson. The H to bb decay channel is particularly interesting and promising, as it has the largest branching fraction. Optimization of data inputs and estimation of backgrounds for measurements of ttH production with H to bb are the topics of this thesis. In 2019, the CMS collaboration presented evidence of ttH, H to bb using 2016 (35.9 1/fb) and 2017 (41.5 1/fb) data. Contributions to this measurement in terms of development of new triggers are described. A more precise measurement using the full Run-2 data (2016–2018 : 137.2 1/fb) is underway. One particularly challenging background limiting the precision of this important measurement arises from direct tt + bb production. A novel estimation method for this background and the resulting improvement expected in the ttH, H to bb measurement are presented. Finally, improvements and optimization of operation and data acquisition of the CMS pixel detector will be described, which enhance the b-tagging capability, crucial for ttH, H to bb measurements.
The Kepler satellite has provided photometric timeseries data of unprecedented length, duty cycle and precision. To fully analyse these data for the tens of thousands of stars observed by Kepler, ...automated methods are a prerequisite. Here we present an automated procedure to determine the period spacing of gravity modes in red-giant stars ascending the red-giant branch. The gravity modes reside in a cavity in the deep interior of the stars and provide information on the conditions in the stellar core. However, for red giants the gravity modes are not directly observable on the surface, hence this method is based on the pressure-gravity mixed modes that present observable features in the Fourier power spectrum. The method presented here is based on the vertical alignment and symmetry of these mixed modes in a period echelle diagram. We find that we can obtain reliable results for both model frequencies and observed frequencies. Additionally, we carried out Monte Carlo tests to obtain realistic uncertainties on the period spacings with different set of oscillation modes (for the models) and uncertainties on the frequencies. Furthermore, this method has been used to improve mode detection and identification of the observed frequencies in an iterative manner.
Quantum Hall effect provides a simple way to study the competition between single particle physics and electronic interaction. However, electronic interaction becomes important only in very clean ...graphene samples and so far the trilayer graphene experiments are understood within non-interacting electron picture. Here, we report evidence of strong electronic interactions and quantum Hall ferromagnetism seen in Bernal-stacked trilayer graphene. Due to high mobility ∼500,000 cm
V
s
in our device compared to previous studies, we find all symmetry broken states and that Landau-level gaps are enhanced by interactions; an aspect explained by our self-consistent Hartree-Fock calculations. Moreover, we observe hysteresis as a function of filling factor and spikes in the longitudinal resistance which, together, signal the formation of quantum Hall ferromagnetic states at low magnetic field.
The sequence of the zeroth Landau levels (LLs) between filling factors ν=-6 to 6 in ABA-stacked trilayer graphene (TLG) is unknown because it depends sensitively on the nonuniform charge distribution ...on the three layers of ABA-stacked TLG. Using the sensitivity of quantum Hall data on the electric field and magnetic field, in an ultraclean ABA-stacked TLG sample, we quantitatively estimate the nonuniformity of the electric field and determine the sequence of the zeroth LLs. We also observe anticrossings between some LLs differing by 3 in LL index, which result from the breaking of the continuous rotational to C_{3} symmetry by the trigonal warping.
HapR is designated as a high cell density quorum sensing master regulatory protein of
Vibrio cholerae
. It is a member of the TetR family protein and functions both as an activator and a repressor by ...directly communicating with cognate promoters, thus controlling the expression of a plethora of genes in a density-dependent manner. Molecular insights reveal the domain architecture and further unveil the significance of a cross talk between the DNA binding domain and the dimerization domain for the functionality of the wild-type protein. The DNA binding domain is made up of three α-helices, where a helix-turn-helix motif spans between the helices α2 and α3. The essentiality of the glycine-rich linker linking helices α1 and α2 came into prominence while unraveling the molecular basis of a natural non-functional variant of HapR. Subsequently, the importance of linker length was demonstrated. The present study, involving a series of biochemical analyses coupled with molecular dynamics simulation, has illustrated the indispensability of a critical arginine within the linker at position 37 contributing to HapR–DNA binding activity.
Phosphopantetheine adenylyltransferase (PPAT) is a rate limiting enzyme which catalyzes the conversion of ATP and pantetheine to dephosphocoenzyme and pyrophosphate. The enzyme is allosteric in ...nature and regulated by Coenzyme A (CoA) through feedback inhibition. So far, several structures have been solved to decipher the catalytic mechanism of this enzyme.
To address catalytic and inhibitory mechanisms of PPAT, structural insights from single crystal X-ray diffraction method were primarily used, followed by biophysical and biochemical analysis.
We have solved the structures of PPAT from Pseudomonas aeruginosa with its substrate analogue AMP-PNP and inhibitor CoA. For the first time, a co-crystal structure of PPAT with Acetyl‐CoA (AcCoA) was determined. Enzymatic analysis was performed to decipher the catalytic, allosteric and inhibitory mechanisms involved in regulation of PPAT. Binding affinities of PPAT with its substrates and inhibitors were determined by SPR.
Previous studies from Escherichia coli and Arabidopsis indicated the inhibitory activity of AcCoA. PPAT‐AcCoA structure along with some biochemical methods established AcCoA as an inhibitor to PPAT and illustrated its inhibitory mechanism. Transition from catalytic to allosteric state involves formation of ternary complex. We have studied the structural features of the ternary complex of PPAT along with its product pyrophosphate and inhibitor CoA and validated it with other biophysical and biochemical methods. Extensive analysis of all these 3D structures indicates that changes in side chains R90 and D94 are responsible for transition between catalytic and allosteric inhibitory states.
These enzymatic studies provide new insights into the allosteric mechanism of PPAT.
•PPAT is an allosteric enzyme catalyzing the rate limiting step in CoA biosynthesis.•It is regulated by CoA and AcCoA which is inhibited by feedback inhibition.•Allosteric to catalytic states are characterized by a ternary complex.•Ca2+ ion has an influence in the inhibition of the enzyme.•R90 and D94 play a crucial role during such process.
Gram-negative bacteria like
Yersinia
,
Pseudomonas
, and
Aeromonas
need type III secretion system (T3SS) for their pathogenicity. V-antigen and its regulator are essential for functioning of T3SS. ...There is significant functional conservation amongst V-antigen and its regulator belonging to the Ysc family. In this study, we have structurally characterized the inter-genus complexes of V-antigen and its regulator. ConSurf analysis demonstrates that V-antigens belonging to the Ysc family show high structural identity predominantly confined to the two long helical regions. The regulator of V-antigen shows high conservation in its first intramolecular coiled-coil domain, responsible for interaction with V-antigen. ∆LcrG
(1–70)
localizes within the groove formed by long helices of LcrV, as observed in PcrV-∆PcrG
(13–72)
interaction. Inter-genus complexes of LcrV-PcrG and PcrV-LcrG exhibited elongated conformation and 1:1 heterodimeric state like the native complex of PcrV-PcrG and LcrV-LcrG. Both native and inter-genus complexes showed rigid tertiary structure, solvent-exposed hydrophobic patches, and cooperative melting behavior with high melting temperature. LcrV-PcrG and PcrV-LcrG showed nanomolar affinity of interaction, identical to PcrV-PcrG interaction, but stronger than LcrV-LcrG interaction. Calcium (a secretion blocker of T3SS) propels all the complexes towards a highly monodisperse form. Calcium and magnesium increase the helicity of the native and inter-genus complexes, and causes helix–helix stabilization. Stabilization of helices leads to a slight increase in the melting temperature by 1.5–2.0 °C. However, calcium does not alter the affinity of interaction of V-antigen and its regulator, emphasizing the effect of divalent of cations at the structural level without any regulatory implications. Therefore, the structural conservation of these inter-genus complexes could be the basis for their functional complementation.
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