365 research outputs found
Coexistence and critical behaviour in a lattice model of competing species
In the present paper we study a lattice model of two species competing for
the same resources. Monte Carlo simulations for d=1, 2, and 3 show that when
resources are easily available both species coexist. However, when the supply
of resources is on an intermediate level, the species with slower metabolism
becomes extinct. On the other hand, when resources are scarce it is the species
with faster metabolism that becomes extinct. The range of coexistence of the
two species increases with dimension. We suggest that our model might describe
some aspects of the competition between normal and tumor cells. With such an
interpretation, examples of tumor remission, recurrence and of different
morphologies are presented. In the d=1 and d=2 models, we analyse the nature of
phase transitions: they are either discontinuous or belong to the
directed-percolation universality class, and in some cases they have an active
subcritical phase. In the d=2 case, one of the transitions seems to be
characterized by critical exponents different than directed-percolation ones,
but this transition could be also weakly discontinuous. In the d=3 version,
Monte Carlo simulations are in a good agreement with the solution of the
mean-field approximation. This approximation predicts that oscillatory
behaviour occurs in the present model, but only for d>2. For d>=2, a steady
state depends on the initial configuration in some cases.Comment: 11 pages, 14 figure
Anomalous asymmetry of magnetoresistance in NbSe single crystals
A pronounced asymmetry of magnetoresistance with respect to the magnetic
field direction is observed for NbSe crystals placed in a magnetic field
perpendicular to their conducting planes. It is shown that the effect persists
in a wide temperature range and manifests itself starting from a certain
magnetic induction value , which at K corresponds to the
transition to the quantum limit, i.to the state where the Landay level
splitting exceeds the temperature.Comment: 4 pages, 6 figures, to be appeared in JETP Let
Loneliness, social support and cardiovascular reactivity to laboratory stress
Self-reported or explicit loneliness and social support have been inconsistently associated with cardiovascular reactivity (CVR) to stress. The present study aimed to adapt an implicit measure of loneliness, and use it alongside the measures of explicit loneliness and social support, to investigate their correlations with CVR to laboratory stress. Twenty-five female volunteers aged between 18 and 39 years completed self-reported measures of loneliness and social support, and an Implicit Association Test (IAT) of loneliness. The systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) reactivity indices were measured in response to psychosocial stress induced in the laboratory. Functional support indices of social support were significantly correlated with CVR reactivity to stress. Interestingly, implicit, but not explicit, loneliness was significantly correlated with DBP reactivity after one of the stressors. No associations were found between structural support and CVR indices. Results are discussed in terms of validity of implicit versus explicit measures and possible factors that affect physiological outcomes
Artificial intelligence for the real-time classification of intrapapillary capillary loop patterns in the endoscopic diagnosis of early oesophageal squamous cell carcinoma: A proof-of-concept study
BACKGROUND:
Intrapapillary capillary loops (IPCLs) represent an endoscopically visible feature of early squamous cell neoplasia (ESCN) which correlate with invasion depth – an important factor in the success of curative endoscopic therapy. IPCLs visualised on magnification endoscopy with Narrow Band Imaging (ME-NBI) can be used to train convolutional neural networks (CNNs) to detect the presence and classify staging of ESCN lesions.
METHODS:
A total of 7046 sequential high-definition ME-NBI images from 17 patients (10 ESCN, 7 normal) were used to train a CNN. IPCL patterns were classified by three expert endoscopists according to the Japanese Endoscopic Society classification. Normal IPCLs were defined as type A, abnormal as B1–3. Matched histology was obtained for all imaged areas.
RESULTS:
This CNN differentiates abnormal from normal IPCL patterns with 93.7% accuracy (86.2% to 98.3%) and sensitivity and specificity for classifying abnormal IPCL patterns of 89.3% (78.1% to 100%) and 98% (92% to 99.7%), respectively. Our CNN operates in real time with diagnostic prediction times between 26.17 ms and 37.48 ms.
CONCLUSION:
Our novel and proof-of-concept application of computer-aided endoscopic diagnosis shows that a CNN can accurately classify IPCL patterns as normal or abnormal. This system could be used as an in vivo, real-time clinical decision support tool for endoscopists assessing and directing local therapy of ESCN
The Weddell Gyre, Southern Ocean: present knowledge and future challenges
The Weddell Gyre (WG) is one of the main oceanographic features of the Southern Ocean south of the Antarctic Circumpolar Current which plays an influential role in global ocean circulation as well as gas exchange with the atmosphere. We review the state‐of‐the art knowledge concerning the WG from an interdisciplinary perspective, uncovering critical aspects needed to understand this system's role in shaping the future evolution of oceanic heat and carbon uptake over the next decades. The main limitations in our knowledge are related to the conditions in this extreme and remote environment, where the polar night, very low air temperatures and presence of sea ice year‐round hamper field and remotely sensed measurements. We highlight the importance of winter and under‐ice conditions in the southern WG, the role that new technology will play to overcome present‐day sampling limitations, the importance of the WG connectivity to the low‐latitude oceans and atmosphere, and the expected intensification of the WG circulation as the westerly winds intensify. Greater international cooperation is needed to define key sampling locations that can be visited by any research vessel in the region. Existing transects sampled since the 1980s along the Prime Meridian and along an East‐West section at ~62°S should be maintained with regularity to provide answers to the relevant questions. This approach will provide long‐term data to determine trends and will improve representation of processes for regional, Antarctic‐wide and global modeling efforts – thereby enhancing predictions of the WG in global ocean circulation and climate
Islands and despots
This paper challenges a conventional wisdom: that when discussing
political systems, small is democratic. And yet, can there be paradises
without serpents? The presumed manageability of small island spaces
promotes and nurtures dispositions for domination and control over
nature and society. In such dark circumstances, authoritarian rule is a
more natural fit than democracy. By adopting an inter-disciplinary
perspective, this paper argues that small island societies may be
wonderful places to live in, as long as one conforms to a dominant
cultural code. Should one deviate from expected and established
practices, the threat of ostracism is immense. Formal democratic
institutions may and often do exist, and a semblance of pluralism may
be manifest, but these are likely to be overshadowed by a set of
unitarist and homogenous values and practices to which many
significant social players, in politics and civil society, subscribe (at
least in public).peer-reviewe
High Effectiveness of Broad Access Direct-Acting Antiviral Therapy for Hepatitis C in an Australian Real-World Cohort: The REACH-C Study
Australia was one of the first countries with unrestricted access to government subsidized direct-acting antiviral (DAA) therapy for adults with chronic hepatitis C virus. This study assessed real-world DAA treatment outcomes across a diverse range of Australian clinical services and evaluated factors associated with successful treatment and loss to follow-up. Real-world Effectiveness of Antiviral therapy in Chronic Hepatitis C (REACH-C) consisted a national observational cohort of 96 clinical services including specialist clinics and less traditional settings such as general practice. Data were obtained on consecutive individuals who commenced DAAs from March 2016 to June 2019. Effectiveness was assessed by sustained virological response ≥12 weeks following treatment (SVR) using intention-to-treat (ITT) and per-protocol (PP) analyses. Within REACH-C, 10,843 individuals initiated DAAs (male 69%; ≥50 years 52%; cirrhosis 22%). SVR data were available in 85% (9,174 of 10,843). SVR was 81% (8,750 of 10,843) by ITT and 95% (8,750 of 9,174) by PP. High SVR (≥92%) was observed across all service types and participant characteristics. Male gender (adjusted odds ratio [aOR] 0.56, 95% confidence interval [CI] 0.43-0.72), cirrhosis (aOR 0.52, 95% CI 0.41-0.64), recent injecting drug use (IDU; aOR 0.64, 95% CI 0.46-0.91) and previous DAA treatment (aOR 0.50, 95% CI 0.28-0.90) decreased the likelihood of achieving SVR. Multiple factors modified the likelihood of loss to follow-up including IDU ± opioid agonist therapy (OAT; IDU only: aOR 1.75, 95% CI 1.44-2.11; IDU + OAT: aOR 1.39, 95% CI 1.11-1.74; OAT only, aOR 1.36; 95% CI 1.13-1.68) and age (aOR 0.97, 95% CI 0.97-0.98). Conclusion: Treatment response was high in a diverse population and through a broad range of services following universal access to DAA therapy. Loss to follow-up presents a real-world challenge. Younger people who inject drugs were more likely to disengage from care, requiring innovative strategies to retain them in follow-up
Replacing Conventional Carbon Nucleophiles with Electrophiles: Nickel-Catalyzed Reductive Alkylation of Aryl Bromides and Chlorides
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