1,923 research outputs found
An evaluation of model potential and pseudopotential methods for the calculation of interatomic potentials
This thesis presents an evaluation of the model potential and pseudopotential methods for
the calculation of atom-atom interaction curves.
At University College London, Peach has computed interatomic potential curves for
several alkali-rare gas pairs using both the model potential and pseudopotential methods
in a completely self-consistent manner. The value of these calculations is that any
differences between the interatomic potential curves obtained from the model potential
and pseudopotential methods can be attributed unambiguously to the theoretical
representations of the Pauli exclusion principle which differentiate the two methods. The
work of Peach thus allows the utility of these two representations to be compared directly
and their effect on the quality of the resulting interatomic potentials to be assessed.
The present study has developed a suite of computer programs designed to calculate
observable quantities which are sensitive to the interatomic potentials. Calculations of the
profiles, widths and shifts of the alkali resonance line when perturbed by rare gases,
together with cross sections for fine structure state changing transitions within the alkali
excited state multiplet, are reported and comparisons are made with experimental
measurements of these observables.
It is demonstrated that the theoretical representation of the Pauli exclusion principle has a
significant effect on the quality of the resulting interatomic potentials. Observables
calculated on the basis of interatomic potentials obtained via the model potential method
are in better agreement with the available experimental data than those calculated on the
basis of pseudopotential interaction curves. From this it may be inferred that the
interatomic potentials obtained by the model potential method represent the actual
interaction between alkali and rare gas atoms more accurately than do interatomic
potentials obtained by the pseudopotential method.
The results of this study provide strong evidence for the superiority of the model potential
method for the calculation of interatomic potentials
Multiplicity in the experience of voice-hearing: A phenomenological inquiry
Although it is recognized that voice-hearers often report a large number and variety of voices there have been few investigations of this multiplicity. Understanding the phenomenology of voice-hearing can provide a firm foundation for theorizing about its causes. In this international online survey of voice-hearers, details were elicited of the content of up to five utterances associated with up to five voices from each respondent. The contents were independently rated and associated with characteristics of each voice such as its perceived age, whether it had changed over time, and whether it was of a familiar person. We investigated predictors (e.g., diagnoses, voice gender, age first heard) of utterance negativity, length, and whether voices referred to themselves. The average number of voices reported was approximately four. The majority were perceived as male and had negative content. Child-aged voices were significantly less negative than all other voices except those perceived as being elderly. Multi-level analyses indicated that there was significant variability at the level of different utterances within voices but variability was more prominent at the level of different voices within an individual. The data were inconsistent with general cognitive models for hearing voices such as the misattribution of inner speech and were more congruent with a dissociation model of voice-hearing. Our findings support approaches based on subtype or dimensional methods of classifying voices, and additionally indicate that research and clinical assessment may benefit from more systematic assessment of multiplicity
PLIN5 deletion remodels intracellular lipid composition and causes insulin resistance in muscle
Defective control of lipid metabolism leading to lipotoxicity causes insulin resistance in skeletal muscle, a major factor leading to diabetes. Here, we demonstrate that perilipin (PLIN) 5 is required to couple intramyocellular triacylglycerol lipolysis with the metabolic demand for fatty acids. PLIN5 ablation depleted triacylglycerol stores but increased sphingolipids including ceramide, hydroxylceramides and sphingomyelin. We generated perilipin 5 (Plin5)-/- mice to determine the functional significance of PLIN5 in metabolic control and insulin action. Loss of PLIN5 had no effect on body weight, feeding or adiposity but increased whole-body carbohydrate oxidation. Plin5-/- mice developed skeletal muscle insulin resistance, which was associated with ceramide accumulation. Liver insulin sensitivity was improved in Plin5-/- mice, indicating tissue-specific effects of PLIN5 on insulin action. We conclude that PLIN5 plays a critical role in coordinating skeletal muscle triacylglycerol metabolism, which impacts sphingolipid metabolism, and is requisite for the maintenance of skeletal muscle insulin action. © 2014 The Authors
One-loop SYM-supergravity relation for five-point amplitudes
We derive a linear relation between the one-loop five-point amplitude of N=8
supergravity and the one-loop five-point subleading-color amplitudes of N=4
supersymmetric Yang-Mills theory.Comment: 17 pages, 2 figures; v2: very minor correction
Author Correction: Dynamic regulation of canonical TGFβ signalling by endothelial transcription factor ERG protects from liver fibrogenesis.
An amendment to this paper has been published and can be accessed via a link at the top of the paper
The Thermal Design, Characterization, and Performance of the SPIDER Long-Duration Balloon Cryostat
We describe the SPIDER flight cryostat, which is designed to cool six
millimeter-wavelength telescopes during an Antarctic long-duration balloon
flight. The cryostat, one of the largest to have flown on a stratospheric
payload, uses liquid helium-4 to deliver cooling power to stages at 4.2 and 1.6
K. Stainless steel capillaries facilitate a high flow impedance connection
between the main liquid helium tank and a smaller superfluid tank, allowing the
latter to operate at 1.6 K as long as there is liquid in the 4.2 K main tank.
Each telescope houses a closed cycle helium-3 adsorption refrigerator that
further cools the focal planes down to 300 mK. Liquid helium vapor from the
main tank is routed through heat exchangers that cool radiation shields,
providing negative thermal feedback. The system performed successfully during a
17 day flight in the 2014-2015 Antarctic summer. The cryostat had a total hold
time of 16.8 days, with 15.9 days occurring during flight.Comment: 15 pgs, 17 fig
Neural processing of criticism and positive comments from relatives in individuals with schizotypal personality traits
Objectives. High negative expressed emotion by family members towards schizophrenia patients increases the risk of subsequent relapse. The study aimed to determine whether individuals with high schizotypy (HS) and low schizotypy (LS) would differ in activation of brain areas involved in cognitive control when listening to relative criticism
Contact Manifolds, Contact Instantons, and Twistor Geometry
Recently, Kallen and Zabzine computed the partition function of a twisted
supersymmetric Yang-Mills theory on the five-dimensional sphere using
localisation techniques. Key to their construction is a five-dimensional
generalisation of the instanton equation to which they refer as the contact
instanton equation. Subject of this article is the twistor construction of this
equation when formulated on K-contact manifolds and the discussion of its
integrability properties. We also present certain extensions to higher
dimensions and supersymmetric generalisations.Comment: v3: 28 pages, clarifications and references added, version to appear
in JHE
Spin-orbit density wave induced hidden topological order in URu2Si2
The conventional order parameters in quantum matters are often characterized
by 'spontaneous' broken symmetries. However, sometimes the broken symmetries
may blend with the invariant symmetries to lead to mysterious emergent phases.
The heavy fermion metal URu2Si2 is one such example, where the order parameter
responsible for a second-order phase transition at Th = 17.5 K has remained a
long-standing mystery. Here we propose via ab-initio calculation and effective
model that a novel spin-orbit density wave in the f-states is responsible for
the hidden-order phase in URu2Si2. The staggered spin-orbit order 'spontaneous'
breaks rotational, and translational symmetries while time-reversal symmetry
remains intact. Thus it is immune to pressure, but can be destroyed by magnetic
field even at T = 0 K, that means at a quantum critical point. We compute
topological index of the order parameter to show that the hidden order is
topologically invariant. Finally, some verifiable predictions are presented.Comment: (v2) Substantially modified from v1, more calculation and comparison
with experiments are include
Whole breast and regional nodal irradiation in prone versus supine position in left sided breast cancer
Background: Prone whole breast irradiation (WBI) leads to reduced heart and lung doses in breast cancer patients receiving adjuvant radiotherapy. In this feasibility trial, we investigated the prone position for whole breast + lymph node irradiation (WB + LNI).
Methods: A new support device was developed for optimal target coverage, on which patients are positioned in a position resembling a phase from the crawl swimming technique (prone crawl position). Five left sided breast cancer patients were included and simulated in supine and prone position. For each patient, a treatment plan was made in prone and supine position for WB + LNI to the whole axilla and the unoperated part of the axilla. Patients served as their own controls for comparing dosimetry of target volumes and organs at risk (OAR) in prone versus in supine position.
Results: Target volume coverage differed only slightly between prone and supine position. Doses were significantly reduced (P < 0.05) in prone position for ipsilateral lung (Dmean, D2, V5, V10, V20, V30), contralateral lung (Dmean, D2), contralateral breast (Dmean, D2 and for total axillary WB + LNI also V5), thyroid (Dmean, D2, V5, V10, V20, V30), oesophagus (Dmean and for partial axillary WB + LNI also D2 and V5), skin (D2 and for partial axillary WB + LNI V105 and V107). There were no significant differences for heart and humeral head doses.
Conclusions: Prone crawl position in WB + LNI allows for good breast and nodal target coverage with better sparing of ipsilateral lung, thyroid, contralateral breast, contralateral lung and oesophagus when compared to supine position. There is no difference in heart and humeral head doses
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