Abstract
We present an application of the major new features of pySecDec, a program designed to numerically calculate multi-loop integrals. One important new feature is the ability to integrate ...weighted sums of integrals in a way which is optimised to reach a given accuracy goal on the sums rather than on the individual integrals. Another feature is the option to perform asymptotic expansions. These new assets of the program represent an important step towards the efficient evaluation of multi-loop amplitudes in a largely automated way. We will illustrate them in a pedagogical example, through the calculation of the one-loop amplitude for Higgs plus jet production in the gluon channel, mediated by a top quark loop. Numerical results in the heavy top limit, compared to their analytic counterparts, are shown as well.
In a recent paper Nucl. Phys. B 585 (2000) 741 we have presented an automated subtraction method for divergent multi-loop/leg integrals in dimensional regularisation which allows for their numerical ...evaluation, and applied it to diagrams with massless internal lines. Here we show how to extend this algorithm to Feynman diagrams with massive propagators and arbitrary propagator powers. As applications, we present numerical results for the master 2-loop 4-point topologies with massive internal lines occurring in Bhabha scattering at two loops, and for the master integrals of planar and non-planar massless double box graphs with two off-shell legs. We also evaluate numerically some two-point functions up to 5 loops relevant for beta-function calculations, and a 3-loop 4-point function, the massless on-shell planar triple box. Whereas the 4-point functions are evaluated in non-physical kinematic regions, the results for the propagator functions are valid for arbitrary kinematics.
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•Super TPV based on XNBR and PA12 via the application of novel cyclic peroxide.•Highest mechanical properties and thermal stability of TPV of 50:50 XNBR-PA12.•Superior performance ...behaviour with reference to heat and oil aging study.
Thermoplastic vulcanizates (TPVs) are special classes of thermoplastic elastomers, in which dynamic vulcanization of the rubber phase takes place during melt mixing with a semi-crystalline thermoplastic matrix phase at elevated temperature. TPV is characterized by processing behaviour like thermoplastic at elevated temperature and performance properties of vulcanized rubber at ambient temperature. High performance TPVs or super TPVs are new generation TPVs which exhibit high heat resistance as well as excellent oil resistance property suitable for automotive under-the-hood applications. In the present work, a new super TPV based on carboxylated acrylonitrile butadiene rubber (XNBR) and polyamide (PA12) has been developed. (XNBR:PA12) TPVs of different blend ratios have been prepared by using a fixed concentration of novel cyclic monofunctional peroxide. Final morphology of TPVs varies from either a co-continuous to a dispersed one depending on the blend ratio. TPV of 50:50 XNBR-PA12 shows the highest mechanical properties as well as superior thermal stability among all other TPVs. From differential scanning calorimetric (DSC) study, it can be clearly seen that the glass transition temperature (Tg) of XNBR has shifted to high temperature range in case of all TPVs as compared to that of uncrosslinked blend system. Dynamic mechanical analysis (DMA) also demonstrates that tanδ values of all the TPVs are lower and the storage moduli are higher than the uncrosslinked blend system. Lowest tanδ peak of TPV of 50:50 blend ratio of XNBR:PA12 indicates the highest degree of crosslinking and this is also supported by the swelling studies. The highest level of mechanical properties and superior thermal stability support that phenomenon. Heat aging and oil resistance study have also been carried out in details to understand the performance behaviour of these super TPVs at service condition.
This paper presents the quantification of uncertain natural frequency for laminated composite plates by using a novel surrogate model. A group method of data handling in conjunction to polynomial ...neural network (PNN) is employed as surrogate for numerical model and is trained by using Latin hypercube sampling. Subsequently the effect of noise on a PNN based uncertainty quantification algorithm is explored in this study. The convergence of the proposed algorithm for stochastic natural frequency analysis of composite plates is verified and validated with original finite element method (FEM). Both individual and combined variation of stochastic input parameters are considered to address the influence on the output of interest. The sample size and computational cost are reduced by employing the present approach compared to direct Monte Carlo simulation (MCS).
The prevalence of obesity has increased dramatically worldwide. The obesity epidemic begs for novel concepts and therapeutic targets that cohesively address "food-abuse" disorders. We demonstrate a ...molecular link between impairment of a central kinase (Akt) involved in insulin signaling induced by exposure to a high-fat (HF) diet and dysregulation of higher order circuitry involved in feeding. Dopamine (DA) rich brain structures, such as striatum, provide motivation stimuli for feeding. In these central circuitries, DA dysfunction is posited to contribute to obesity pathogenesis. We identified a mechanistic link between metabolic dysregulation and the maladaptive behaviors that potentiate weight gain. Insulin, a hormone in the periphery, also acts centrally to regulate both homeostatic and reward-based HF feeding. It regulates DA homeostasis, in part, by controlling a key element in DA clearance, the DA transporter (DAT). Upon HF feeding, nigro-striatal neurons rapidly develop insulin signaling deficiencies, causing increased HF calorie intake.
We show that consumption of fat-rich food impairs striatal activation of the insulin-activated signaling kinase, Akt. HF-induced Akt impairment, in turn, reduces DAT cell surface expression and function, thereby decreasing DA homeostasis and amphetamine (AMPH)-induced DA efflux. In addition, HF-mediated dysregulation of Akt signaling impairs DA-related behaviors such as (AMPH)-induced locomotion and increased caloric intake. We restored nigro-striatal Akt phosphorylation using recombinant viral vector expression technology. We observed a rescue of DAT expression in HF fed rats, which was associated with a return of locomotor responses to AMPH and normalization of HF diet-induced hyperphagia.
Acquired disruption of brain insulin action may confer risk for and/or underlie "food-abuse" disorders and the recalcitrance of obesity. This molecular model, thus, explains how even short-term exposure to "the fast food lifestyle" creates a cycle of disordered eating that cements pathological changes in DA signaling leading to weight gain and obesity.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
ALIX recruits ESCRT-III CHMP4 and is involved in membrane remodeling during endosomal receptor sorting, budding of some enveloped viruses, and cytokinesis. We show that ALIX dimerizes via the middle ...domain (ALIX-V) in solution. Structural modeling based on small angle X-ray scattering (SAXS) data reveals an elongated crescent-shaped conformation for dimeric ALIX lacking the proline-rich domain (ALIXBRO1-V). Mutations at the dimerization interface prevent dimerization and induce an open elongated monomeric conformation of ALIX-V as determined by SAXS modeling. ALIX dimerizes in vivo and dimeric ALIX colocalizes with CHMP4B upon coexpression. We show further that ALIX dimerization affects HIV-1 budding. C-terminally truncated activated CHMP4B retaining the ALIX binding site forms linear, circular, and helical filaments in vitro, which can be bridged by ALIX. Our data suggest that dimeric ALIX represents the active form that interacts with ESCRT-III CHMP4 polymers and functions as a scaffolding protein during membrane remodeling processes.
The dynamic and efficient coordination of primary photosynthetic reactions with leaf energization and metabolism under a wide range of environmental conditions is a fundamental property of plants ...involving processes at all functional levels. The present historical perspective covers 60 years of research aiming to understand the underlying mechanisms, linking major breakthroughs to current progress. It centers on the contributions of Ulrich Heber who had pioneered novel concepts, fundamental methods, and mechanistic understanding of photosynthesis. An important first step was the development of non-aqueous preparation of chloroplasts allowing the investigation of chloroplast metabolites ex vivo (meaning that the obtained results reflect the in vivo situation). Later on, intact chloroplasts, retaining their functional envelope membranes, were isolated in aqueous media to investigate compartmentation and exchange of metabolites between chloroplasts and external medium. These studies elucidated metabolic interaction between chloroplasts and cytoplasm during photosynthesis. Experiments with isolated intact chloroplasts clarified that oxygenation of ribulose-1.5-bisphosphate generates glycolate in photorespiration. The development of non-invasive optical methods enabled researchers identifying mechanisms that balance electron flow in the photosynthetic electron transport system avoiding its over-reduction. Recording chlorophyll
a
(Chl
a
) fluorescence allowed one to monitor, among other parameters, thermal energy dissipation by means of ‘nonphotochemical quenching’ of the excited state of Chl
a
. Furthermore, studies both in vivo and in vitro led to basic understanding of the biochemical mechanisms of freezing damage and frost tolerance of plant leaves, to SO
2
tolerance of tree leaves and dehydrating lichens and mosses.
In the present work, the development and characterization of an intrinsically self-healable material based on butyl imidazole modified bromobutyl rubber (BIIR)/natural rubber (NR) blends, which are ...filled with carbon nanotubes (CNTs) are reported. It was found that the addition of CNTs and the blending with NR significantly enhance the tensile strength of the BIIR composites. The use of butyl imidazole as physical cross-linker for the BIIR phase provides the blend composites the non-covalent bondings, which are responsible for their self-healing properties. Owing to the increase of the viscosity of the BIIR phase upon its physical crosslinking the island-matrix morphology of the blend changes over to a co-continuous structure. The preferential wetting of the CNT surface by the low-loading NR phase in the NR/BIIR blends can be explained by the good rubber-filler interaction between the linked phospholipids of the NR molecules and the π-electrons of the CNT surface. As a result, the favored localization of the CNTs in the NR phase strongly improves the electrical properties of the blends according to the double percolation theory. On the other hand it does not deteriorate the self-healing of the BIIR phase. The high electrical conductivity provides us a possibility to heat the blend by application of an electrical voltage in order to accelerate the self-healing process.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Novel thermoplastic vulcanizates (TPVs) based on silicone rubber (PDMS) and polyamide (PA12) have been prepared by dynamic vulcanization process. The effect of dynamic vulcanization and influence of ...various types of peroxides as cross-linking agents were studied in detail. All the TPVs were prepared at a ratio of 50/50 wt% of silicone rubber and polyamide. Three structurally different peroxides, namely dicumyl peroxide (DCP), 3,3,5,7,7-pentamethyl 1,2,4-trioxepane (PMTO) and cumyl hydroperoxide (CHP) were taken for investigation. Though DCP was the best option for curing the silicone rubber, at high temperature it suffers from scorch safety. An inhibitor 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) was added with DCP to stabilize the radicals in order to increase the scorch time. Though CHP (hydroperoxide) had higher half life time than DCP at higher temperature, it has no significant effect on cross-linking of silicone rubber. PMTO showed prolonged scorch safety and better cross-linking efficiency rather than the other two. TPVs of DCP and PMTO were made up to 11 minutes of mixing. Increased values of tensile strength and elongation at break of PMTO cross-linked TPV indicate the superiority of PMTO. Scanning electron micrographs correlate with mechanical properties of the TPVs. High storage modulus (E') and lower loss tangent value of the PMTO cross-linked TPV indicate the higher degree of cross-linking which is also well supported by the overall cross-link density value. Thus PMTO was found to be the superior peroxide for cross-linking of silicone rubber at high temperature.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
We present a program for the numerical evaluation of form factors entering the calculation of one-loop amplitudes with up to six external legs. The program is written in Fortran95 and performs the ...reduction to a certain set of basis integrals numerically, using a formalism where inverse Gram determinants can be avoided. It can be used to calculate one-loop amplitudes with massless internal particles in a fast and numerically stable way.
Program title: golem95_v1.0
Catalogue identifier: AEEO_v1_0
Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEEO_v1_0.html
Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland
Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html
No. of lines in distributed program, including test data, etc.: 50 105
No. of bytes in distributed program, including test data, etc.: 241 657
Distribution format: tar.gz
Programming language: Fortran95
Computer: Any computer with a Fortran95 compiler
Operating system: Linux, Unix
RAM: RAM used per form factor is insignificant, even for a rank six six-point form factor
Classification: 4.4, 11.1
External routines: Perl programming language (http://www.perl.com/)
Nature of problem: Evaluation of one-loop multi-leg tensor integrals occurring in the calculation of next-to-leading order corrections to scattering amplitudes in elementary particle physics.
Solution method: Tensor integrals are represented in terms of form factors and a set of basic building blocks (“basis integrals”). The reduction to the basis integrals is performed numerically, thus avoiding the generation of large algebraic expressions.
Restrictions: The current version contains basis integrals for massless internal particles only. Basis integrals for massive internal particles will be included in a future version.
Running time: Depends on the nature of the problem. A rank 6 six-point form factor at a randomly chosen kinematic point takes 0.13 seconds on an Intel Core 2 Q9450 2.66 GHz processor, without any optimisation. With compiler optimisation flag -O3 the same point takes 0.09 seconds. Timings for lower point form factors are: All form factors for five-point functions from rank 0 to rank 4: 0.04 s. All form factors for rank 5 five-point functions: 0.05 s. All form factors for four-point functions from rank 0 to rank 4: 0.01 s.
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