268 research outputs found
The Portevin-Le Chatelier effect in the Continuous Time Random Walk framework
We present a continuous time random walk model for the Portevin-Le Chatelier
(PLC) effect. From our result it is shown that the dynamics of the PLC band can
be explained in terms of the Levy Walk
Singular perturbation of reduced wave equation and scattering from an embedded obstacle
We consider time-harmonic wave scattering from an inhomogeneous isotropic
medium supported in a bounded domain ().
{In a subregion , the medium is supposed to be lossy and have a
large mass density. We study the asymptotic development of the wave field as
the mass density } and show that the wave field inside
will decay exponentially while the wave filed outside the medium will
converge to the one corresponding to a sound-hard obstacle
buried in the medium supported in . Moreover, the
normal velocity of the wave field on from outside is shown to
be vanishing as . {We derive very accurate estimates
for the wave field inside and outside and on in terms of
, and show that the asymptotic estimates are sharp. The implication of
the obtained results is given for an inverse scattering problem of
reconstructing a complex scatterer.
Radiation exposure of adrenal vein sampling: a German Multicenter Study
Objective: Adrenal vein sampling (AVS) represents the current diagnostic standard for subtype differentiation in primary aldosteronism (PA). However, AVS has its drawbacks. It is invasive, expensive, requires an experienced interventional radiologist and comes with radiation exposure. However, exact radiation exposure of patients undergoing AVS has never been examined. Design and methods: We retrospectively analyzed radiation exposure of 656 AVS performed between 1999 and 2017 at four university hospitals. The primary outcomes were dose area product (DAP) and fluoroscopy time (FT). Consecutively the effective dose (ED) was approximately calculated. Results: Median DAP was found to be 32.5Gy*cm(2) (0.3-3181) and FT 18 min (0.3-184). The calculated ED was 6.4 mSv (0.1-636). Remarkably, values between participating centers highly varied: Median DAP ranged from 16 to 147 Gy*cm(2), FT from 16 to 27 min, and ED from 3.2 to 29 mSv. As main reason for this variation, differences regarding AVS protocols between centers could be identified, such as number of sampling locations, frames per second and the use of digital subtraction angiographies. Conclusion: This first systematic assessment of radiation exposure in AVS not only shows fairly high values for patients, but also states notable differences among the centers. Thus, we not only recommend taking into account the risk of radiation exposure, when referring patients to undergo AVS, but also to establish improved standard operating procedures to prevent unnecessary radiation exposure
Recurrence analysis of the Portevin-Le Chatelier effect
Tensile tests were carried out by deforming polycrystalline samples of
Al-2.5%Mg alloy at room temperature in a wide range of strain rates where the
Portevin-Le Chatelier (PLC) effect was observed. The experimental stress-time
series data have been analyzed using the recurrence analysis technique based on
the Recurrence Plot (RP) and the Recurrence Quantification Analysis (RQA) to
study the change in the dynamical behavior of the PLC effect with the imposed
strain rate. Our study revealed that the RQA is able to detect the unique
crossover phenomenon in the PLC dynamics.Comment: 17 pages, 3 figure
Impact of tumor burden on normal organ distribution in patients imaged with CXCR4-targeted [68Ga]Ga-PentixaFor PET/CT
BACKGROUND: CXCR4-directed positron emission tomography/computed tomography (PET/CT) has been used as a diagnostic tool in patients with solid tumors. We aimed to determine a potential correlation between tumor burden and radiotracer accumulation in normal organs. METHODS: Ninety patients with histologically proven solid cancers underwent CXCR4-targeted [(68)Ga]Ga-PentixaFor PET/CT. Volumes of interest (VOIs) were placed in normal organs (heart, liver, spleen, bone marrow, and kidneys) and tumor lesions. Mean standardized uptake values (SUV(mean)) for normal organs were determined. For CXCR4-positive tumor burden, maximum SUV (SUV(max)), tumor volume (TV), and fractional tumor activity (FTA, defined as SUV(mean) x TV), were calculated. We used a Spearman's rank correlation coefficient (Ï) to derive correlative indices between normal organ uptake and tumor burden. RESULTS: Median SUV(mean) in unaffected organs was 5.2 for the spleen (range, 2.44 â 10.55), 3.27 for the kidneys (range, 1.52 â 17.4), followed by bone marrow (1.76, range, 0.84 â 3.98), heart (1.66, range, 0.88 â 2.89), and liver (1.28, range, 0.73 â 2.45). No significant correlation between SUV(max) in tumor lesions (Ïââ€â0.189, Pââ„â0.07), TV (Ïââ„â-0.204, Pââ„â0.06) or FTA (Ïââ„â-0.142, Pââ„â0.18) with the investigated organs was found. CONCLUSIONS: In patients with solid tumors imaged with [(68)Ga]Ga-PentixaFor PET/CT, no relevant tumor sink effect was noted. This observation may be of relevance for therapies with radioactive and non-radioactive CXCR4-directed drugs, as with increasing tumor burden, the dose to normal organs may remain unchanged
Misogynoir and the public woman: analog and digital sexualization of women in public from the Civil War to the era of Kamala Harris
This essay identifies how the very conception of public woman is infused with the opprobrium hurled against a wanton womanâa sexualized figure who has lost claims to moral standing or social worth. Our analysis begins diachronically by using thin description to trace the historical conflation of public woman in general, and Black woman in particular, with prostitute to outline the contours of the trope of public woman that have solidified across time. We document how the public woman became equated with prostitute, and then how the label prostitute was affixed to women in public to situate them as promiscuous or prurient. Our analysis proceeds synchronically as we argue that the toxic archive of memes and hashtags that name Kamala Harris a âhoâ operates as a contemporary iteration of misogynoir that conflates public woman with prostitute. The result of our analysis is an identification of the digital public woman wherein the acceleration and repetition of such tropes ensures a recalcitrant public sentiment toward public women and hides the technological and rhetorical connections that intensify such public feelings
High order amplitude equation for steps on creep curve
We consider a model proposed by one of the authors for a type of plastic
instability found in creep experiments which reproduces a number of
experimentally observed features. The model consists of three coupled
non-linear differential equations describing the evolution of three types of
dislocations. The transition to the instability has been shown to be via Hopf
bifurcation leading to limit cycle solutions with respect to physically
relevant drive parameters. Here we use reductive perturbative method to extract
an amplitude equation of up to seventh order to obtain an approximate analytic
expression for the order parameter. The analysis also enables us to obtain the
bifurcation (phase) diagram of the instability. We find that while
supercritical bifurcation dominates the major part of the instability region,
subcritical bifurcation gradually takes over at one end of the region. These
results are compared with the known experimental results. Approximate analytic
expressions for the limit cycles for different types of bifurcations are shown
to agree with their corresponding numerical solutions of the equations
describing the model. The analysis also shows that high order nonlinearities
are important in the problem. This approach further allows us to map the
theoretical parameters to the experimentally observed macroscopic quantities.Comment: LaTex file and eps figures; Communicated to Phys. Rev.
Distinct Hypothalamic Neurons Mediate Estrogenic Effects on Energy Homeostasis and Reproduction
SummaryEstrogens regulate body weight and reproduction primarily through actions on estrogen receptor-α (ERα). However, ERα-expressing cells mediating these effects are not identified. We demonstrate that brain-specific deletion of ERα in female mice causes abdominal obesity stemming from both hyperphagia and hypometabolism. Hypometabolism and abdominal obesity, but not hyperphagia, are recapitulated in female mice lacking ERα in hypothalamic steroidogenic factor-1 (SF1) neurons. In contrast, deletion of ERα in hypothalamic pro-opiomelanocortin (POMC) neurons leads to hyperphagia, without directly influencing energy expenditure or fat distribution. Further, simultaneous deletion of ERα from both SF1 and POMC neurons causes hypometabolism, hyperphagia, and increased visceral adiposity. Additionally, female mice lacking ERα in SF1 neurons develop anovulation and infertility, while POMC-specific deletion of ERα inhibits negative feedback regulation of estrogens and impairs fertility in females. These results indicate that estrogens act on distinct hypothalamic ERα neurons to regulate different aspects of energy homeostasis and reproduction
Prognostic factors in stage III-IV adrenocortical carcinomas (ACC): an European Network for the Study of Adrenal Tumor (ENSAT) study.
BACKGROUND:
The clinical course of advanced adrenocortical carcinoma (ACC) is heterogeneous. Our study aimed primarily to refine and make headway in the prognostic stratification of advanced ACC.
PATIENTS AND METHODS:
Patients with advanced ENSAT ACC (stage III or stage IV) at diagnosis registered between 2000 and 2009 in the ENSAT database were enrolled. The primary end point was overall survival (OS). Parameters of potential prognostic relevance were selected. Univariate and multivariate analyses were carried out: model 1 'before surgery'; model 2 'post-surgery'.
RESULTS:
Four hundred and forty-four patients with advanced ENSAT ACC (stage III: 210; stage IV: 234) were analyzed. After a median follow-up of 55.2 months, the median OS was 24 months. A modified ENSAT (mENSAT) classification was validated: stage III (invasion of surrounding tissues/organs or the vena renalis/cava) and stage IVa, IVb, IVc (2, 3 or >3 metastatic organs, including N, respectively). Two- or 5-year OS was 73%, 46%, 26% and 15% or 50%, 15%, 14% and 2% for stages III, IVa, IVb and IVc, respectively. In the multivariate analysis, mENSAT stages (stages IVa, IVb, or IVc, respectively) were significantly correlated with OS (P 6 and/or Ki67 â„20%, P = 0.06) in model 2.
CONCLUSION:
The mENSAT classification and GRAS parameters (Grade, R status, Age and Symptoms) were found to best stratify the prognosis of patients with advanced ACC
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