580 research outputs found
Rydberg-London Potential for Diatomic Molecules and Unbonded Atom Pairs
We propose and test a pair potential that is accurate at all relevant
distances and simple enough for use in large-scale computer simulations. A
combination of the Rydberg potential from spectroscopy and the London
inverse-sixth-power energy, the proposed form fits spectroscopically determined
potentials better than the Morse, Varnshi, and Hulburt-Hirschfelder potentials
and much better than the Lennard-Jones and harmonic potentials. At long
distances, it goes smoothly to the correct London force appropriate for gases
and preserves van der Waals's "continuity of the gas and liquid states," which
is routinely violated by coefficients assigned to the Lennard-Jones 6-12 form.Comment: Five pages, 10 figure
Refining pathological evaluation of neoadjuvant therapy for adenocarcinoma of the esophagus
AIM: To assess tumour regression grade (TRG) and lymph node downstaging to help define patients who benefit from neoadjuvant chemotherapy.METHODS: Two hundred and eighteen consecutive patients with adenocarcinoma of the esophagus or gastro-esophageal junction treated with surgery alone or neoadjuvant chemotherapy and surgery between 2005 and 2011 at a single institution were reviewed. Triplet neoadjuvant chemotherapy consisting of platinum, fluoropyrimidine and anthracycline was considered for operable patients (World Health Organization performance status ? 2) with clinical stage T2-4 N0-1. Response to neoadjuvant chemotherapy (NAC) was assessed using TRG, as described by Mandard et al. In addition lymph node downstaging was also assessed. Lymph node downstaging was defined by cN1 at diagnosis: assessed radiologically (computed tomography, positron emission tomography, endoscopic ultrasonography), then pathologically recorded as N0 after surgery; ypN0 if NAC given prior to surgery, or pN0 if surgery alone. Patients were followed up for 5 years post surgery. Recurrence was defined radiologically, with or without pathological confirmation. An association was examined between t TRG and lymph node downstaging with disease free survival (DFS) and a comprehensive range of clinicopathological characteristics.RESULTS: Two hundred and eighteen patients underwent esophageal resection during the study interval with a mean follow up of 3 years (median follow up: 2.552, 95%CI: 2.022-3.081). There was a 1.8% (n = 4) inpatient mortality rate. One hundred and thirty-six (62.4%) patients received NAC, with 74.3% (n = 101) of patients demonstrating some signs of pathological tumour regression (TRG 1-4) and 5.9% (n = 8) having a complete pathological response. Forty four point one percent (n = 60) had downstaging of their nodal disease (cN1 to ypN0), compared to only 15.9% (n = 13) that underwent surgery alone (pre-operatively overstaged: cN1 to pN0), (P < 0.0001). Response to NAC was associated with significantly increased DFS (mean DFS; TRG 1-2: 5.1 years, 95%CI: 4.6-5.6 vs TRG 3-5: 2.8 years, 95%CI: 2.2-3.3, P < 0.0001). Nodal down-staging conferred a significant DFS advantage for those patients with a poor primary tumour response to NAC (median DFS; TRG 3-5 and nodal down-staging: 5.533 years, 95%CI: 3.558-7.531 vs TRG 3-5 and no nodal down-staging: 1.114 years, 95%CI: 0.961-1.267, P < 0.0001).CONCLUSION: Response to NAC in the primary tumour and in the lymph nodes are both independently associated with improved DFS
Dorsal vs. ventral differences in fast Up-state-associated oscillations in the medial prefrontal cortex of the urethane-anesthetized rat.
Cortical slow oscillations (0.1–1 Hz), which may play a role in memory consolidation, are a hallmark of non-rapid eye movement (NREM) sleep and also occur under anesthesia. During slow oscillations the neuronal network generates faster oscillations on the active Up-states and these nested oscillations are particularly prominent in the PFC. In rodents the medial prefrontal cortex (mPFC) consists of several subregions: anterior cingulate cortex (ACC), prelimbic (PrL), infralimbic (IL), and dorsal peduncular cortices (DP). Although each region has a distinct anatomy and function, it is not known whether slow or fast network oscillations differ between subregions in vivo. We have simultaneously recorded slow and fast network oscillations in all four subregions of the rodent mPFC under urethane anesthesia. Slow oscillations were synchronous between the mPFC subregions, and across the hemispheres, with no consistent amplitude difference between subregions. Delta (2–4 Hz) activity showed only small differences between subregions. However, oscillations in the spindle (6–15 Hz)-, beta (20–30 Hz), gamma (30–80 Hz)-, and high-gamma (80–150 Hz)-frequency bands were consistently larger in the dorsal regions (ACC and PrL) compared with ventral regions (IL and DP). In dorsal regions the peak power of spindle, beta, and gamma activity occurred early after onset of the Up-state. In the ventral regions, especially the DP, the oscillatory power in the spindle-, beta-, and gamma-frequency ranges peaked later in the Up-state. These results suggest variations in fast network oscillations within the mPFC that may reflect the different functions and connectivity of these subregions. NEW & NOTEWORTHY We demonstrate, in the urethane-anesthetized rat, that within the medial prefrontal cortex (mPFC) there are clear subregional differences in the fast network oscillations associated with the slow oscillation Up-state. These differences, particularly between the dorsal and ventral subregions of the mPFC, may reflect the different functions and connectivity of these subregions
Using the NOAA Advanced Very High Resolution Radiometer to characterise temporal and spatial trends in water temperature of large European lakes
Lakes are major repositories of biodiversity, provide multiple ecosystem services and are widely recognised as key indicators of environmental change. However, studies of lake response to drivers of change at a pan-European scale are exceptionally rare. The need for such studies has been given renewed impetus by concerns over environmental change and because of international policies, such as the EU Water Framework Directive (WFD), which impose legal obligations to monitor the condition of European lakes towards sustainable systems with good ecological status. This has highlighted the need for methods that can be widely applied across large spatial and temporal scales and produce comparable results. Remote sensing promises much in terms of information provision, but the spatial transferability and temporal repeatability of methods and relationships observed at individual or regional case studies remains unproven at the continental scale. This study demonstrates that NOAA Advanced Very High Resolution Radiometer (AVHRR) thermal data are capable of producing highly accurate (R2 > 0.9) lake surface temperature (LST) estimates in lakes with variable hydromorphological characteristics and contrasting thermal regimes. Validation of the approach using archived AVHRR thermal data for Lake Geneva produced observations that were consistent with field data for equivalent time periods. This approach provides the basis for generalizing temporal and spatial trends in European lake surface temperature over several decades and confirms the potential of the full 30 year NOAA AVHRR archive to can provide AVHRR-derived LST estimates to help inform European policies on lake water quality.</p
A biomimetic spiking neural network of the auditory midbrain for mobile robot sound localisation in reverberant environments
This paper proposes a spiking neural network (SNN) of the mammalian auditory midbrain to achieve binaural sound source localisation with a mobile robot. The network is inspired by neurophysiological studies on the organisation of binaural processing in the medial superior olive (MSO), lateral superior olive (LSO) and the inferior colliculus (IC) to achieve a sharp azimuthal localisation of sound source over a wide frequency range in situations where there is auditory clutter and reverberation. Three groups of artificial neurons are constructed to represent the neurons in the MSO, LSO and IC that are sensitive to interaural time difference (ITD), interaural level difference (ILD) and azimuth angle respectively. The ITD and ILD cues are combined in the IC using Bayes's theorem to estimate the azimuthal direction of a sound source. Two of known IC cells, onset and sustained-regular are modelled. The azimuth estimations at different robot positions are then used to calculate the sound source position by a triangulation method using an environment map constructed by a laser scanner. The experimental results show that the addition of ILD information significantly increases sound localisation performance at frequencies above 1 kHz. The mobile robot is able to localise a sound source in an acoustically cluttered and reverberant environment.Engineering & Physical Sciences Research Council, UK (EPSRC
Cosmological Constraints from the Clustering of the Sloan Digital Sky Survey DR7 Luminous Red Galaxies
We present the power spectrum of the reconstructed halo density field derived
from a sample of Luminous Red Galaxies (LRGs) from the Sloan Digital Sky Survey
Seventh Data Release (DR7). The halo power spectrum has a direct connection to
the underlying dark matter power for k <= 0.2 h/Mpc, well into the quasi-linear
regime. This enables us to use a factor of ~8 more modes in the cosmological
analysis than an analysis with kmax = 0.1 h/Mpc, as was adopted in the SDSS
team analysis of the DR4 LRG sample (Tegmark et al. 2006). The observed halo
power spectrum for 0.02 < k < 0.2 h/Mpc is well-fit by our model: chi^2 = 39.6
for 40 degrees of freedom for the best fit LCDM model. We find \Omega_m h^2 *
(n_s/0.96)^0.13 = 0.141^{+0.009}_{-0.012} for a power law primordial power
spectrum with spectral index n_s and \Omega_b h^2 = 0.02265 fixed, consistent
with CMB measurements. The halo power spectrum also constrains the ratio of the
comoving sound horizon at the baryon-drag epoch to an effective distance to
z=0.35: r_s/D_V(0.35) = 0.1097^{+0.0039}_{-0.0042}. Combining the halo power
spectrum measurement with the WMAP 5 year results, for the flat LCDM model we
find \Omega_m = 0.289 +/- 0.019 and H_0 = 69.4 +/- 1.6 km/s/Mpc. Allowing for
massive neutrinos in LCDM, we find \sum m_{\nu} < 0.62 eV at the 95% confidence
level. If we instead consider the effective number of relativistic species Neff
as a free parameter, we find Neff = 4.8^{+1.8}_{-1.7}. Combining also with the
Kowalski et al. (2008) supernova sample, we find \Omega_{tot} = 1.011 +/- 0.009
and w = -0.99 +/- 0.11 for an open cosmology with constant dark energy equation
of state w.Comment: 26 pages, 19 figures, submitted to MNRAS. The power spectrum and a
module to calculate the likelihoods is publicly available at
http://lambda.gsfc.nasa.gov/toolbox/lrgdr/ . v2 fixes abstract formatting
issu
Temporal pattern of neuronal responses (PSTH) to pure tone in the inferior Colliculus
باتوجه به اینکه بین طرح زمانی پاسخ (Post-stimulus time histogram=PSTH) نورون ها و عملکرد فیزیولوژیک آنها ارتباط تنگاتنگی وجود دارد و طرح پاسخ نورون ها در کالیکولوس تحتانی (هسته بزرگ شنوایی در مغز میانی) بطور کامل مشخص نبود، این مطالعه در جهت شناسایی و تقسیم بندی دقیق طرح های پاسخ به صورت خالص ورودی از گوش مقابل انجام گرفت. مطالعه بر روی خوکچه هندی و با روش ثبت پتانسیل عمل خارج سلولی انجام پذیرفت. تعداد 216 نورون مورد مطالعه قرار گرفت، که 80 آنان در هسته مرکزی کالیکولوس تحتانی قرار داشتند. طرح های پاسخ اصلی شامل این موارد بودند: Chopper (که دارای یک وقفه در پاسخ اند)، On-sustained (که به شروع و دوام تحریک پاسخ می دهند)، Sustained (که فقط به دوام تحریک پاسخ می دهند)، Onset (که فقط به شروع تحریک پاسخ می دهند) و Off (که پاسخ مهاری کامل به تحریک صوتی می دهند). این گروه های اصلی خود به زیر گروه های متعددی تقسیم شده اند. همچنین مکانیسم پاسخ ها و نقش فیزیولوژیک محتمل آنان باتوجه به مطالعات دیگر مورد کنکاش قرار گرفت
Unifying the Midbrain: The Commissure of the Inferior Colliculus
Commissural fibres that interconnect the two sides of the brain are found at severalpoints along the auditory pathway, thus suggesting their fundamental importance for theanalysis of sound. This chapter presents an overview of what is currently known aboutthe anatomy, physiology, and behavioral influences of the commissure of the inferiorcolliculus (CoIC)—the most prominent brainstem auditory commissure—that reciprocallyinterconnects the principal nuclei of the auditory midbrain, the inferior colliculi (IC). Theprimary contribution to the CoIC originates from neurons projecting from one inferiorcolliculus to the other, with the dorsal cortex and central nucleus providing the mostextensive connections. In addition, many ascending and descending auditory centers sendprojections to IC via the CoIC, together with a diverse range of sources located outsidethe classically defined auditory pathway. The degree of interconnection between the twoICs suggests they function as a single entity. Recent in vivo evidence has established thatCoIC projections modulate the neural representation of sound frequency, level, andlocation in IC, thus indicating an important role for the CoIC in auditory processing. However, there is limited evidence for the influence of the CoIC on auditory behavior. This, together with the diversity of sources projecting via CoIC, suggest unknown rolesthat warrant further exploration
The Astropy Problem
The Astropy Project (http://astropy.org) is, in its own words, "a community
effort to develop a single core package for Astronomy in Python and foster
interoperability between Python astronomy packages." For five years this
project has been managed, written, and operated as a grassroots,
self-organized, almost entirely volunteer effort while the software is used by
the majority of the astronomical community. Despite this, the project has
always been and remains to this day effectively unfunded. Further, contributors
receive little or no formal recognition for creating and supporting what is now
critical software. This paper explores the problem in detail, outlines possible
solutions to correct this, and presents a few suggestions on how to address the
sustainability of general purpose astronomical software
Open access data in polar and cryospheric remote sensing
This paper aims to introduce the main types and sources of remotely sensed data that are freely available and have cryospheric applications. We describe aerial and satellite photography, satellite-borne visible, near-infrared and thermal infrared sensors, synthetic aperture radar, passive microwave imagers and active microwave scatterometers. We consider the availability and practical utility of archival data, dating back in some cases to the 1920s for aerial photography and the 1960s for satellite imagery, the data that are being collected today and the prospects for future data collection; in all cases, with a focus on data that are openly accessible. Derived data products are increasingly available, and we give examples of such products of particular value in polar and cryospheric research. We also discuss the availability and applicability of free and, where possible, open-source software tools for reading and processing remotely sensed data. The paper concludes with a discussion of open data access within polar and cryospheric sciences, considering trends in data discoverability, access, sharing and use.A. Pope would like to acknowledge support from the Earth Observation Technology Cluster, a
knowledge exchange project, funded by the Natural Environment Research Council (NERC) under its
Technology Clusters Programme, the U.S. National Science Foundation Graduate Research Fellowship
Program, Trinity College (Cambridge) and the Dartmouth Visiting Young Scientist program sponsored
by the NASA New Hampshire Space Grant.This is the final published version. It's also available from MDPI at http://www.mdpi.com/2072-4292/6/7/6183
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