5,072 research outputs found
Quantifying cellular dynamics in mice using a novel fluorescent division reporter system
The dynamics of cell populations are frequently studied in vivo using pulse-chase DNA labeling techniques. When combined with mathematical models, the kinetic of label uptake and loss within a population of interest then allows one to estimate rates of cell production and turnover through death or onward differentiation. Here we explore an alternative method of quantifying cellular dynamics, using a cell fate-mapping mouse model in which dividing cells can be induced to constitutively express a fluorescent protein, using a Ki67 reporter construct. We use a pulse-chase approach with this reporter mouse system to measure the lifespans and division rates of naive CD4 and CD8 T cells using a variety of modeling approaches, and show that they are all consistent with estimates derived from other published methods. However we propose that to obtain unbiased parameter estimates and full measures of their uncertainty one should simultaneously model the timecourses of the frequencies of labeled cells within both the population of interest and its precursor. We conclude that Ki67 reporter mice provide a promising system for modeling cellular dynamics
Flersporede samtaler og hvordan de skabes
It is a well-known phenomenon that participants orient to several things, people or topics within conversations. Sometimes, this can develop into what Maria Egbert (1993) calls schisming, namely when a single conversation diverges into several conversations that are not necessarily dependent on each other. This paper takes a conversation analytic approach to showing how some participants in a conversation (three members of a study group in this case) can create and take part in two different conversations, which are both dependent on the main conversation. Furthermore, it shows that participants create these subordinate conversations through intersubjective processes and contextualization of their roles and relationships. Lastly, it suggests and discusses a new phenomenon similar to the notion of schisming that we call primary and secondary conversational tracks/sequences, and how it can be further investigated in talk in interaction
Quantifying cellular dynamics in mice using a novel fluorescent division reporter system
The dynamics of cell populations are frequently studied in vivo using pulse-chase DNA labeling techniques. When combined with mathematical models, the kinetic of label uptake and loss within a population of interest then allows one to estimate rates of cell production and turnover through death or onward differentiation. Here we explore an alternative method of quantifying cellular dynamics, using a cell fate-mapping mouse model in which dividing cells can be induced to constitutively express a fluorescent protein, using a Ki67 reporter construct. We use a pulse-chase approach with this reporter mouse system to measure the lifespans and division rates of naive CD4 and CD8 T cells using a variety of modeling approaches, and show that they are all consistent with estimates derived from other published methods. However we propose that to obtain unbiased parameter estimates and full measures of their uncertainty one should simultaneously model the timecourses of the frequencies of labeled cells within both the population of interest and its precursor. We conclude that Ki67 reporter mice provide a promising system for modeling cellular dynamics
Serenity: An ATCA prototyping platform for CMS Phase-2
Serenity is an ATCA prototyping platform designed to explore alternative, novel design choices
for CMS Phase-2. It uses a newly available interconnect technology from Samtec (Z-RAY) to
mount a removable processing unit (FPGA) that should mitigate risk and provides significant
flexibility in processing unit choice and connectivity. We explore the pros and cons of using an
industry-standard Computer-On-Module running standard Centos Linux and a small service
FPGA for low level control. Specially designed Kapton heaters have been used to validate the
thermal design of the card and broader considerations of ATCA systems
A Spitzer Survey for Dust in Type IIn Supernovae
Recent observations suggest that Type IIn supernovae (SNe IIn) may exhibit
late-time (>100 days) infrared (IR) emission from warm dust more than other
types of core-collapse SNe. Mid-IR observations, which span the peak of the
thermal spectral energy distribution, provide useful constraints on the
properties of the dust and, ultimately, the circumstellar environment,
explosion mechanism, and progenitor system. Due to the low SN IIn rate (<10% of
all core-collapse SNe), few IR observations exist for this subclass. The
handful of isolated studies, however, show late-time IR emission from warm dust
that, in some cases, extends for five or six years post-discovery. While
previous Spitzer/IRAC surveys have searched for dust in SNe, none have targeted
the Type IIn subclass. This article presents results from a warm Spitzer/IRAC
survey of the positions of all 68 known SNe IIn within a distance of 250 Mpc
between 1999 and 2008 that have remained unobserved by Spitzer more than 100
days post-discovery. The detection of late-time emission from ten targets
(~15%) nearly doubles the database of existing mid-IR observations of SNe IIn.
Although optical spectra show evidence for new dust formation in some cases,
the data show that in most cases the likely origin of the mid-IR emission is
pre-existing dust, which is continuously heated by optical emission generated
by ongoing circumstellar interaction between the forward shock and
circumstellar medium. Furthermore, an emerging trend suggests that these SNe
decline at ~1000--2000 days post-discovery once the forward shock overruns the
dust shell. The mass-loss rates associated with these dust shells are
consistent with luminous blue variable (LBV) progenitors.Comment: Accepted for publication to ApJ, 17 pages, 10 figures, 10 table
Run 2 Upgrades to the CMS Level-1 Calorimeter Trigger
The CMS Level-1 calorimeter trigger is being upgraded in two stages to
maintain performance as the LHC increases pile-up and instantaneous luminosity
in its second run. In the first stage, improved algorithms including
event-by-event pile-up corrections are used. New algorithms for heavy ion
running have also been developed. In the second stage, higher granularity
inputs and a time-multiplexed approach allow for improved position and energy
resolution. Data processing in both stages of the upgrade is performed with
new, Xilinx Virtex-7 based AMC cards.Comment: 10 pages, 7 figure
Triggering on electrons, jets and tau leptons with the CMS upgraded calorimeter trigger for the LHC RUN II
The Compact Muon Solenoid (CMS) experiment has implemented a sophisticated two-level online selection system that achieves a rejection factor of nearly 10e5. During Run II, the LHC will increase its centre-of-mass energy up to 13 TeV and progressively reach an instantaneous luminosity of 2e34cm-2s-1. In order to guarantee a successful and ambitious physics programme under this intense environment, the CMS Trigger and Data acquisition (DAQ) system has been upgraded. A novel concept for the L1 calorimeter trigger is introduced the Time Multiplexed Trigger (TMT). In this design, nine main receive each all of the calorimeter data from an entire event provided by 18 preprocessors. This design is not different from that of the CMS DAQ and HLT systems. The advantage of the TMT architecture is that a global view and full granularity of the calorimeters can be exploited by sophisticated algortihms. The goal is to maintain the current thresholds for calorimeter objects and improve the performance for their selection. The performance of these algorithms will be demonstrated, both in terms of efficiency and rate reduction. The callenging aspects of the pile-up mitigation and firmware design will be presented
Utilising light-emitting diodes of specific narrow wavelengths for the optimization and co-production of multiple high-value compounds in Porphyridium purpureum
The effect of specific narrow light-emitting diode (LED) wavelengths (red, green, blue) and a combination of LED wavelengths (red, green and blue - RGB) on biomass composition produced by Porphyridium purpureum is studied. Phycobiliprotein, fatty acids, exopolysaccharides, pigment content, and the main macromolecules composition were analysed to determine the effect of wavelength on multiple compounds of commercial interest. The results demonstrate that green light plays a significant role in the growth of rhodophyta, due to phycobiliproteins being able to harvest green wavelengths where chlorophyll pigments absorb poorly. However, under multi-chromatic LED wavelengths, P. purpureum biomass accumulated the highest yield of valuable products such as eicosapentaenoic acid (~2.9 %DW), zeaxanthin (~586 Îźg gâ 1 DW), β-carotene (397 Îźg gâ 1 DW), exopolysaccharides (2.05 g/L-1), and phycobiliproteins (~ 4.8 % DW). This increased accumulation is likely to be the combination of both photo-adaption and photo-protection, under the combined specific wavelengths employed
Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV
The performance of muon reconstruction, identification, and triggering in CMS
has been studied using 40 inverse picobarns of data collected in pp collisions
at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection
criteria covering a wide range of physics analysis needs have been examined.
For all considered selections, the efficiency to reconstruct and identify a
muon with a transverse momentum pT larger than a few GeV is above 95% over the
whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4,
while the probability to misidentify a hadron as a muon is well below 1%. The
efficiency to trigger on single muons with pT above a few GeV is higher than
90% over the full eta range, and typically substantially better. The overall
momentum scale is measured to a precision of 0.2% with muons from Z decays. The
transverse momentum resolution varies from 1% to 6% depending on pseudorapidity
for muons with pT below 100 GeV and, using cosmic rays, it is shown to be
better than 10% in the central region up to pT = 1 TeV. Observed distributions
of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO
Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV
The performance of muon reconstruction, identification, and triggering in CMS
has been studied using 40 inverse picobarns of data collected in pp collisions
at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection
criteria covering a wide range of physics analysis needs have been examined.
For all considered selections, the efficiency to reconstruct and identify a
muon with a transverse momentum pT larger than a few GeV is above 95% over the
whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4,
while the probability to misidentify a hadron as a muon is well below 1%. The
efficiency to trigger on single muons with pT above a few GeV is higher than
90% over the full eta range, and typically substantially better. The overall
momentum scale is measured to a precision of 0.2% with muons from Z decays. The
transverse momentum resolution varies from 1% to 6% depending on pseudorapidity
for muons with pT below 100 GeV and, using cosmic rays, it is shown to be
better than 10% in the central region up to pT = 1 TeV. Observed distributions
of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO
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