721 research outputs found
Degradation of a quantum directional reference frame as a random walk
We investigate if the degradation of a quantum directional reference frame
through repeated use can be modeled as a classical direction undergoing a
random walk on a sphere. We demonstrate that the behaviour of the fidelity for
a degrading quantum directional reference frame, defined as the average
probability of correctly determining the orientation of a test system, can be
fit precisely using such a model. Physically, the mechanism for the random walk
is the uncontrollable back-action on the reference frame due to its use in a
measurement of the direction of another system. However, we find that the
magnitude of the step size of this random walk is not given by our classical
model and must be determined from the full quantum description.Comment: 5 pages, no figures. Comments are welcome. v2: several changes to
clarify the key results. v3: journal reference added, acknowledgements and
references update
Interactions between fibroblast growth factors and Notch regulate neuronal differentiation
The differentiation of precursor cells into neurons has been shown to be influenced by both the Notch signaling pathway and growth factor stimulation. In this study, the regulation of neuronal differentiation by these mechanisms was examined in the embryonic day 10 neuroepithelial precursor (NEP) population. By downregulating Notch1 expression and by the addition of a Delta1 fusion protein (Delta Fc), it was shown that signaling via the Notch pathway inhibited neuron differentiation in the NEP cells, in vitro. The expression of two of the Notch receptor homologs, Notch1 and Notch3, and the ligand Delta1 in these NEP cells was found to be influenced by a number of different growth factors, indicating a potential interaction between growth factors and Notch signaling. Interestingly, none of the growth factors examined promoted neuron differentiation; however, the fibroblast growth factors (FGFs) 1 and 2 potently inhibited differentiation. FGF1 and FGF2 upregulated the expression of Notch and decreased expression of Delta1 in the NEP cells. In addition, the inhibitory response of the cells to the FGFs could be overcome by downregulating Notch1 expression and by disrupting Notch cleavage and signaling by the ablation of the Presenilin1 gene. These results indicate that FGF1 and FGF2 act via the Notch pathway, either directly or indirectly, to inhibit differentiation. Thus, signaling through the Notch receptor may be a common regulator of neuronal differentiation within the developing forebrain
Equivalent efficiency of a simulated photon-number detector
Homodyne detection is considered as a way to improve the efficiency of
communication near the single-photon level. The current lack of commercially
available {\it infrared} photon-number detectors significantly reduces the
mutual information accessible in such a communication channel. We consider
simulating direct detection via homodyne detection. We find that our particular
simulated direct detection strategy could provide limited improvement in the
classical information transfer. However, we argue that homodyne detectors (and
a polynomial number of linear optical elements) cannot simulate photocounters
arbitrarily well, since otherwise the exponential gap between quantum and
classical computers would vanish.Comment: 4 pages, 4 figure
Perturbations of the local gravity field due to mass distribution on precise measuring instruments: a numerical method applied to a cold atom gravimeter
We present a numerical method, based on a FEM simulation, for the
determination of the gravitational field generated by massive objects, whatever
geometry and space mass density they have. The method was applied for the
determination of the self gravity effect of an absolute cold atom gravimeter
which aims at a relative uncertainty of 10-9. The deduced bias, calculated with
a perturbative treatment, is finally presented. The perturbation reaches (1.3
\pm 0.1) \times 10-9 of the Earth's gravitational field.Comment: 12 pages, 7 figure
Circulating Tumor DNA Markers for Early Progression on Fulvestrant With or Without Palbociclib in ER+ Advanced Breast Cancer.
Background There are no established molecular biomarkers for patients with breast cancer receiving combination endocrine and CDK4/6 inhibitor (CDK4/6i). We aimed to determine whether genomic markers in circulating tumor DNA (ctDNA) can identify patients at higher risk of early progression on fulvestrant therapy with or without palbociclib, a CDK4/6i.Methods PALOMA-3 was a phase III, multicenter, double-blind randomized controlled trial of palbociclib plus fulvestrant (nâ=â347) vs placebo plus fulvestrant (nâ=â174) in patients with endocrine-pretreated estrogen receptor-positive (ER+) breast cancer. Pretreatment plasma samples from 459 patients were analyzed for mutations in 17 genes, copy number in 14 genes, and circulating tumor fraction. Progression-free survival (PFS) was compared in patients with circulating tumor fraction above or below a prespecified cutoff of 10% and with or without a specific genomic alteration. All statistical tests were 2-sided.Results Patients with high ctDNA fraction had worse PFS on both palbociclib plus fulvestrant (hazard ratio [HR] = 1.62, 95% confidence interval [CI] = 1.17 to 2.24; P = .004) and placebo plus fulvestrant (HR = 1.77, 95% CI = 1.21 to 2.59; P = .004). In multivariable analysis, high-circulating tumor fraction was associated with worse PFS (HR = 1.20 per 10% increase in tumor fraction, 95% CI = 1.09 to 1.32; P < .001), as was TP53 mutation (HR = 1.84, 95% CI = 1.27 to 2.65; P = .001) and FGFR1 amplification (HR = 2.91, 95% CI = 1.61 to 5.25; P < .001). No interaction with treatment randomization was observed.Conclusions Pretreatment ctDNA identified a group of high-risk patients with poor clinical outcome despite the addition of CDK4/6 inhibition. These patients might benefit from inclusion in future trials of escalating treatment, with therapies that may be active in these genomic contexts
Optimizing the Dice Score and Jaccard Index for Medical Image Segmentation: Theory & Practice
The Dice score and Jaccard index are commonly used metrics for the evaluation
of segmentation tasks in medical imaging. Convolutional neural networks trained
for image segmentation tasks are usually optimized for (weighted)
cross-entropy. This introduces an adverse discrepancy between the learning
optimization objective (the loss) and the end target metric. Recent works in
computer vision have proposed soft surrogates to alleviate this discrepancy and
directly optimize the desired metric, either through relaxations (soft-Dice,
soft-Jaccard) or submodular optimization (Lov\'asz-softmax). The aim of this
study is two-fold. First, we investigate the theoretical differences in a risk
minimization framework and question the existence of a weighted cross-entropy
loss with weights theoretically optimized to surrogate Dice or Jaccard. Second,
we empirically investigate the behavior of the aforementioned loss functions
w.r.t. evaluation with Dice score and Jaccard index on five medical
segmentation tasks. Through the application of relative approximation bounds,
we show that all surrogates are equivalent up to a multiplicative factor, and
that no optimal weighting of cross-entropy exists to approximate Dice or
Jaccard measures. We validate these findings empirically and show that, while
it is important to opt for one of the target metric surrogates rather than a
cross-entropy-based loss, the choice of the surrogate does not make a
statistical difference on a wide range of medical segmentation tasks.Comment: MICCAI 201
Characterisation of feline renal cortical fibroblast cultures and their transcriptional response to transforming growth factor beta 1
Chronic kidney disease (CKD) is common in geriatric cats, and the most prevalent pathology is chronic tubulointerstitial inflammation and fibrosis. The cell type predominantly responsible for the production of extra-cellular matrix in renal fibrosis is the myofibroblast, and fibroblast to myofibroblast differentiation is probably a crucial event. The cytokine TGF-ÎČ1 is reportedly the most important regulator of myofibroblastic differentiation in other species. The aim of this study was to isolate and characterise renal fibroblasts from cadaverous kidney tissue of cats with and without CKD, and to investigate the transcriptional response to TGF-ÎČ1
First Detection of Polarization of the Submillimetre Diffuse Galactic Dust Emission by Archeops
We present the first determination of the Galactic polarized emission at 353
GHz by Archeops. The data were taken during the Arctic night of February 7,
2002 after the balloon--borne instrument was launched by CNES from the Swedish
Esrange base near Kiruna. In addition to the 143 GHz and 217 GHz frequency
bands dedicated to CMB studies, Archeops had one 545 GHz and six 353 GHz
bolometers mounted in three polarization sensitive pairs that were used for
Galactic foreground studies. We present maps of the I, Q, U Stokes parameters
over 17% of the sky and with a 13 arcmin resolution at 353 GHz (850 microns).
They show a significant Galactic large scale polarized emission coherent on the
longitude ranges [100, 120] and [180, 200] deg. with a degree of polarization
at the level of 4-5%, in agreement with expectations from starlight
polarization measurements. Some regions in the Galactic plane (Gem OB1,
Cassiopeia) show an even stronger degree of polarization in the range 10-20%.
Those findings provide strong evidence for a powerful grain alignment mechanism
throughout the interstellar medium and a coherent magnetic field coplanar to
the Galactic plane. This magnetic field pervades even some dense clouds.
Extrapolated to high Galactic latitude, these results indicate that
interstellar dust polarized emission is the major foreground for PLANCK-HFI CMB
polarization measurement.Comment: Submitted to Astron. & Astrophys., 14 pages, 12 Fig., 2 Table
Abscesso pulmonar de aspiração: anålise de 252 casos consecutivos estudados de 1968 a 2004
The availability of novelty sweets within the high school fringe
Background Reducing sugar consumption is a primary focus of current global public health policy. Achieving 5% of total energy from free sugars will be difficult acknowledging the concentration of free sugars in sugar sweetened beverages, confectionery and as hidden sugars in many savoury items. The expansion of the novelty sweet market in the UK has significant implications for children and young adults as they contribute to dental caries, dental erosion and obesity.
Objective To identify the most available types of novelty sweets within the high school fringe in Cardiff, UK and to assess their price range and where and how they were displayed in shops.
Subjects and methods Shops within a ten minute walking distance around five purposively selected high schools in the Cardiff aea representing different levels of deprivation were visited. Shops in Cardiff city centre and three supermarkets were also visited to identify the most commonly available novelty sweets.
Results The ten most popular novelty sweets identified in these scoping visits were (in descending order): Brain Licker, Push Pop, Juicy Drop, Lickedy Lips, Big Baby Pop, Vimto candy spray, Toxic Waste, Tango candy spray, Brain Blasterz Bitz and Mega Mouth candy spray. Novelty sweets were located on low shelves which were accessible to all age-groups in 73% (14 out of 19) of the shops. Novelty sweets were displayed in the checkout area in 37% (seven out of 19) shops. The price of the top ten novelty sweets ranged from 39p to ÂŁ1.
Conclusion A wide range of acidic and sugary novelty sweets were easily accessible and priced within pocket money range. Those personnel involved in delivering dental and wider health education or health promotion need to be aware of recent developments in children's confectionery. The potential effects of these novelty sweets on both general and dental health require further investigation
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