2,566 research outputs found
Activity Dependent Branching Ratios in Stocks, Solar X-ray Flux, and the Bak-Tang-Wiesenfeld Sandpile Model
We define an activity dependent branching ratio that allows comparison of
different time series . The branching ratio is defined as . The random variable is the value of the next signal given
that the previous one is equal to , so . If
, the process is on average supercritical when the signal is equal to
, while if , it is subcritical. For stock prices we find
within statistical uncertainty, for all , consistent with an ``efficient
market hypothesis''. For stock volumes, solar X-ray flux intensities, and the
Bak-Tang-Wiesenfeld (BTW) sandpile model, is supercritical for small
values of activity and subcritical for the largest ones, indicating a tendency
to return to a typical value. For stock volumes this tendency has an
approximate power law behavior. For solar X-ray flux and the BTW model, there
is a broad regime of activity where , which we interpret as an
indicator of critical behavior. This is true despite different underlying
probability distributions for , and for . For the BTW model the
distribution of is Gaussian, for sufficiently larger than one, and
its variance grows linearly with . Hence, the activity in the BTW model
obeys a central limit theorem when sampling over past histories. The broad
region of activity where is close to one disappears once bulk dissipation
is introduced in the BTW model -- supporting our hypothesis that it is an
indicator of criticality.Comment: 7 pages, 11 figure
The physics and kinematics of the evolved, interacting planetary nebula PN G342.0-01.7
Here we aim to study the physical and kinematical characteristics of the
unstudied old planetary nebula (PN) PN G342.0-01.7, which shows evidence of
interaction with its surrounding interstellar medium. We used Integral Field
Spectra from the Wide Field Spectrograph on the ANU 2.3 m telescope to provide
spectroscopy across the whole object covering the spectral range 3400-7000
{\AA}. We formed narrow-band images to investigate the excitation structure.
The spectral analysis shows that the object is a distant Peimbert Type I PN of
low excitation, formally of excitation class of 0.5. The low electron density,
high dynamical age, and low surface brightness of the object confirm that it is
observed fairly late in its evolution. It shows clear evidence for dredge-up of
CN-processed material characteristic of its class. In addition, the low
peculiar velocity of 7 km s shows it to be a member of the young disk
component of our Galaxy. We built a self-consistent photoionisation model for
the PNe matching the observed spectrum, the H luminosity, and the
diameter. On the basis of this we derive an effective temperature and luminosity . The temperature is much
higher than might have been expected using the excitation class, proving that
this can be misleading in classifying evolved PNe. PN G342.0-01.7 is in
interaction with its surrounding interstellar medium through which the object
is moving in the south-west direction. This interaction drives a slow shock
into the outer PN ejecta. A shock model suggests that it only accounts for
about 10\% of the total luminosity, but has an important effect on the global
spectrum of the PN.Comment: 15 pages, 6 figures, A&A accepted 201
Coulomb interaction from the interplay between Confinement and Screening
It has been noticed that confinement effects can be described by the addition
of a term in the Lagrangian density.
We now study the combined effect of such "confinement term" and that of a mass
term. The surprising result is that the interplay between these two terms gives
rise to a Coulomb interaction. Our picture has a certain correspondence with
the quasiconfinement picture described by Giles, Jaffe and de Rujula for QCD
with symmetry breaking.Comment: 9 page
Galaxy emission line classification using 3D line ratio diagrams
Two-dimensional (2D) line ratio diagnostic diagrams have become a key tool in
understanding the excitation mechanisms of galaxies. The curves used to
separate the different regions - HII-like or else excited by an active galactic
nucleus (AGN) - have been refined over time but the core technique has not
evolved significantly. However, the classification of galaxies based on their
emission line ratios really is a multi-dimensional problem. Here we exploit
recent software developments to explore the potential of three-dimensional (3D)
line ratio diagnostic diagrams. We introduce a specific set of 3D diagrams, the
ZQE diagrams, which separate the oxygen abundance and the ionisation parameter
of HII region-like spectra, and which also enable us to probe the excitation
mechanism of the gas. By examining these new 3D spaces interactively, we define
a new set of 2D diagnostics, the ZE diagnostics, which can provide the
metallicity of objects excited by hot young stars, and which cleanly separate
HII region-like objects from the different classes of AGNs. We show that these
ZE diagnostics are consistent with the key log[NII]/H vs.
log[OIII]/H diagnostic currently used by the community. They also have
the advantage of attaching a probability that a given object belongs to one
class or to the other. Finally, we discuss briefly why ZQE diagrams can provide
a new way to differentiate and study the different classes of AGNs in
anticipation of a dedicated follow-up study.Comment: 21 pages, 15 figures, accepted for publication in ApJ. Due to size
limitations, the supplementary STL file for the 3D-printable diagram is
available here: http://www.mso.anu.edu.au/~fvogt/online_material.htm
Myeloid lineage skewing due to exacerbated NF-κB signaling facilitates osteopenia in Scurfy mice
Immune surveillance through Foxp3+ regulatory T cells plays a crucial role in bone homeostasis. Scurfy, the mouse model of autoimmune IPEX syndrome, bears a loss-of-function mutation in Foxp3 that leads to multi-organ inflammation. Herein, we report that scurfy mice exhibit severe bone loss mediated by accelerated osteoclastogenesis. Mechanistically, Foxp3 deficiency results in the upregulation of NF-κB in T helper cells through the loss of repressive Foxp3/NEMO interaction, thereby unleashing NF-κB-mediated over-production of pro-osteoclastogenic cytokines. Flow cytometry analysis shows marked increase in lin(-)Sca-1(+)c-kit(+) hematopoietic stem cells (LSK HSCs) and granulocyte/macrophage progenitors (GMPs) in bone marrow of scurfy mice with corresponding exacerbated osteoclastogenic potential, implying that osteoclast progenitors are affected at a very primitive stage in this disorder. Scurfy LSK HSCs exhibit greater sensitivity to M-CSF and contain abundant PU.1+ Sf LSK HSCs compared with WT. Accordingly, genetic or pharmacological inhibition of M-CSF or mTOR signaling, but not IL-17 signaling, attenuates osteoclastogenesis and osteopenia in scurfy. Thus, our study suggests that Foxp3 deficiency leads to osteopenia owing to dysregulated NF-κB activity and subsequent cytokine-mediated hyper-proliferation of myeloid precursors, and positions the NF-κB pathway as a potential target for therapeutic intervention for this disorder
Double-blind randomized controlled trial of letrozole versus clomiphene citrate in subfertile women with polycystic ovarian syndrome
STUDY QUESTION: Would letrozole as a primary ovulation induction agent generate better pregnancy rates than clomiphene citrate (CC) in subfertile women with anovulatory polycystic ovarian syndrome (PCOS)?
SUMMARY ANSWER: Participants receiving letrozole as a primary treatment achieved a significantly (P = 0.022) higher clinical pregnancy rate per patient (61.2%) compared to CC (43.0%).
WHAT IS KNOWN ALREADY: According to a recent Cochrane systematic review (2014), letrozole appears to improve live-birth (LB) and pregnancy rates in anovulatory women with PCOS, compared to CC. However, the review concluded that the quality of evidence was low due to poor reporting of study methods and possible publication bias.
STUDY DESIGN, SIZE, DURATION: This double-blind randomized controlled trial (RCT) included 159 participants between April 2007 and June 2014. Subjects were randomly allocated to either CC (n = 79) or letrozole (n = 80) in a 1:1 ratio. Both drugs were encapsulated to look identical. Randomization was performed in mixed blocks and stratified by patients’ BMI (<30 and 30–35 kg/m2).
PARTICIPANTS/MATERIALS, SETTING, METHODS: The trial included subfertile women diagnosed with PCOS. Treatment started with one tablet (CC 50 mg, letrozole 2.5 mg) increasing to two in non-responders and continuing until pregnancy or for up to six ovulatory cycles. Non-responders were crossed over to the other treatment after a 6-week break. Cycles were initially monitored with ultrasound follicle tracking then mid-luteal serum progesterone measurement in subsequent cycles.
MAIN RESULTS AND THE ROLE OF CHANCE: Amongst the 159 participants included in the intention-to-treat analysis, four women conceived before treatment and six were lost-to-follow-up. The remaining 149 participants (74 on CC and 75 on letrozole) completed at least the first treatment. Women receiving letrozole achieved a significantly (P = 0.022; absolute difference [95% confidence interval] 18% [3–33%]) higher pregnancy rate (61.%) than those on CC (43%). The median number of treatment cycles received until pregnancy was significantly (log rank P = 0.038) smaller with letrozole (4[3–5] cycles) compared to CC (6[4–7] cycles). LB rates were not statistically (P = 0.089) different between the two groups, although there was a trend towards higher rates on letrozole (48.8%) compared to CC (35.4%). After the crossover, pregnancy and LB rates on letrozole (n = 45; 28.9 and 24.4%, respectively) were not statistically (P = 0.539 and P = 0.601) different from CC (n = 31; 22.6 and 19.4%).
LIMITATIONS, REASONS FOR CAUTION: One possible limitation of this trial may be the exclusion of PCOS women with BMI > 35 kg/m2, which would limit the applicability of the results in this subgroup of PCOS. However, this group of women are generally excluded from treatment in the majority of fertility centres, especially in Europe, due to the associated challenges and risks.
WIDER IMPLICATIONS OF THE FINDINGS: The results of this trial are consistent with the recent Cochrane systematic review. However, with its robust design, the current RCT provides more valid and compelling evidence for the superiority of letrozole over CC as a primary ovulation induction agent in PCOS women with 40% increase in pregnancy rates and with a shorter time-to-pregnancy. Furthermore, the participants in this RCT are a good representation of subfertile PCOS population receiving fertility treatment in Europe and worldwide. The results are therefore globally generalizable for clinical practice.
STUDY FUNDING/COMPETING INTEREST(S): This RCT was mainly funded by the R&D Funding Scheme of Derby Hospitals NHS Foundation Trust. The study also received funds from School of Medicine, University of Nottingham. The Trust R&D department was involved in the development of the protocol and the running of the trial. The trial was sponsored and monitored by the University of Nottingham. The authors have no conflicts of interest.
TRIAL REGISTRATION NUMBER: www.Clinicaltrials.gov: NCT00478504.
TRIAL REGISTRATION DATE: Registration was verified on 23/05/2007.
DATE OF FIRST PATIENT’S ENROLMENT: 25/04/2007
f [N pi N]: from quarks to the pion derivative coupling
We study the N pi N coupling, in the framework of a QCD-inspired confining
Nambu-Jona-Lasinio model. A simple relativistic confining and instantaneous
quark model is reviewed. The Salpeter equation for the nucleon and the boosted
pion is solved. The f [n pi n] and f[n pi Delta] couplings are calculated and
they turn out to be reasonably good. The sensibility of f[n pi n] and f[n pi
Delta] to confinement, chiral symmetry breaking and Lorentz invariance is
briefly discussed.Comment: 30 pages in LaTex RevTex, 6 postscript figure
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