323 research outputs found
A Feynman-Kac Formula for Anticommuting Brownian Motion
Motivated by application to quantum physics, anticommuting analogues of
Wiener measure and Brownian motion are constructed. The corresponding Ito
integrals are defined and the existence and uniqueness of solutions to a class
of stochastic differential equations is established. This machinery is used to
provide a Feynman-Kac formula for a class of Hamiltonians. Several specific
examples are considered.Comment: 21 page
Neoarchean magmatism in the southern Scott and Raggatt Mountains, Napier Complex, east Antarctica
Cretaceous provenance change in the Hegang Basin and its connection with the Songliao Basin, NE China: Evidence for lithospheric extension driven by palaeo-Pacific roll-back
The Cretaceous Hegang Basin is located on the Jiamusi Block, NE China, and separated from the Songliao Basin by the Lesser Xing'an Range (LXR). Seismic interpretation shows that the Chengzihe, Muling and Dongshan formations of the Hegang Basin thicken eastwards with westwards onlap, indicating that the LXR existed as a palaeo-uplift during that period, whereas the Houshigou Formation shows no thickness change, indicating that the LXR was possibly under water at this time. This is supported by results of detrital zircon analysis from the Hegang Basin in which the Chengzihe Formation is dominated by approximately 180 Ma zircons, which can only be provided by the LXR, whereas the Houshigou Formation records no Early Jurassic ages. This view is consistent with previous studies of the Songliao Basin for a provenance change between the Denglouku and Quantou formations. We conclude that the LXR was a highland during deposition of the Chengzihe, Muling and Dongshan formations but that it was under water when the Houshigou Formation was deposited. There was thus a connection between the Hegang and Songliao basins, which marks an eastwards migration of the depositional and extensional centre of the Songliao-Hegang basin system. This eastwards migration implies lithospheric extension driven by palaeo-Pacific roll-back
Two Neoarchean tectonothermal events on the western edge of the North Atlantic Craton, as revealed by SIMS dating of the Saglek Block, Nain Province, Labrador
The Saglek Block forms the northern part of the Nain Province and underwent widespread metamorphism at
c. 2.7 Ga, producing the dominant gneissosity and intercalation of supracrustal sequences. Zircon dating of gneiss samples
collected along 80 km of the Labrador coast from Ramah Bay in the north to Hebron Fjord in the south confirms the widespread
extent of high-grade metamorphism between 2750 and 2700 Ma. In addition, a distinct event between 2550 and 2510 Ma
produced felsic melt with peritectic garnet in metavolcanic gneiss and granoblastic recrystallization in mafic granulite. Ductile
deformation of granite emplaced at c. 2550 Ma indicates that this later event involved a degree of tectonism during high-T
metamorphism. Such tectonism may be related to a hypothesized post-2.7 Ga juxtaposition of the predominantly Eoarchean
Saglek Block against the Mesoarchean Hopedale Block, along a northāsouth boundary that extends from the coast near Nain to
offshore of Saglek Bay. Evidence of reworking of c. 2.7 Ga gneisses by c. 2.5 Ga tectonothermal activity has been found
elsewhere on the margins of the North Atlantic Craton, of which the Nain Province represents thewestern margin. In particular, a
recent suggestion that c. 2.5 Ga metamorphic ages along the northern margin of the North Atlantic Craton inSWGreenland may
record the final assembly of the craton could also apply to the western margin as represented by the rocks of the Nain Province
Quantum delocalization in photon-pair generation
The generation of correlated photon pairs is a key to the production of entangled quantum states, which have a variety of applications within the area of quantum information. In spontaneous parametric down-conversionāthe primary method of generating correlated photon pairsāthe associated photon annihilation and creation events are generally thought of as being colocated: The correlated pair of photons is localized with regards to the pump photon and its positional origin. A detailed quantum electrodynamical analysis highlights a mechanism exhibiting the possibility of a delocalized origin for paired output photons: The spatial extent of the region from which the pair is generated can be much larger than previously thought. The theory of both localized and nonlocalized degenerate down-conversion is presented, followed by a quantitative analysis using discrete-volume computational methods. The results may have significant implications for quantum information and imaging applications, and the design of nonlinear optical metamaterials
New insight into tuning magnetic phases of RMn6Sn6 kagome metals
Kagome metals with magnetic order offer the possibility of tuning topological
electronic states via external control parameters such as temperature or
magnetic field. ErMnSn (Er) is a member of a group of ,
~rare earth, compounds hosting ferromagnetic Mn kagome nets whose magnetic
moment direction and layer-to-layer magnetic correlations are strongly
influenced by coupling to magnetic moments in neighboring triangular
layers. Here, we use neutron diffraction and magnetization data to examine the
temperature-driven transition in Er from a planar-ferrimagnetic to
distorted-triple-spiral magnetic order. These data inform mean-field
calculations which highlight the fragile, tunable nature of the magnetism
caused by competing Mn-Mn and Mn-Er interlayer magnetic exchange couplings and
Mn and Er magnetic anisotropies. This competition results in the near
degeneracy of a variety of collinear, non-collinear, and non-coplanar magnetic
phases which we show are readily selected and adjusted via changing temperature
or magnetic field. Thermal fluctuations of the Er moment direction provide the
key to this tunability.Comment: 10 pages, 7 figures, Supplementary Informatio
The First Provenance Challenge
The first Provenance Challenge was set up in order to provide a forum for the community to help understand the capabilities of different provenance systems and the expressiveness of their provenance representations. To this end, a Functional Magnetic Resonance Imaging workflow was defined, which participants had to either simulate or run in order to produce some provenance representation, from which a set of identified queries had to be implemented and executed. Sixteen teams responded to the challenge, and submitted their inputs. In this paper, we present the challenge workflow and queries, and summarise the participants contributions
The Precambrian Khondalite Belt in the Daqingshan area, North China Craton: evidence for multiple metamorphic events in the Palaeoproterozoic era
High-grade pelitic metasedimentary rocks (khondalites) are widely distributed in the northwestern part of the North China Craton and were named the āKhondalite Beltā. Prior to the application of zircon geochronology, a stratigraphic division of the supracrustal rocks into several groups was established using interpretative field geology. We report here SHRIMP UāPb zircon ages and Hf-isotope data on metamorphosed sedimentary and magmatic rocks at Daqingshan, a typical area of the Khondalite Belt. The main conclusions are as follows: (1) The early Precambrian supracrustal rocks belong to three sequences: a 2.56ā2.51 Ga supracrustal unit (the previous Sanggan āgroupā), a 2.51ā2.45 Ga supracrustal unit (a portion of the previous upper Wulashan āgroupā) and a 2.0ā1.95 Ga supracrustal unit (including the previous lower Wulashan āgroupā, a portion of original upper Wulashan āgroupā and the original Meidaizhao āgroupā) the units thus do not represent a true stratigraphy; (2) Strong tectono-thermal events occurred during the late Neoarchaean to late Palaeoproterozoic, with four episodes recognized: 2.6ā2.5, 2.45ā2.37, 2.3ā2.0 and 1.95ā1.85 Ga, with the latest event being consistent with the assembly of the Palaeoproterozoic supercontinent Columbia; (3) During the late Neoarchaean to late Palaeoproterozoic (2.55ā2.5, 2.37 and 2.06 Ga) juvenile, mantle-derived material was added to the crust
Critical research gaps and recommendations to inform research prioritisation for more effective prevention and improved outcomes in colorectal cancer
OBJECTIVE: Colorectal cancer (CRC) leads to significant morbidity/mortality worldwide. Defining critical research gaps (RG), their prioritisation and resolution, could improve patient outcomes.DESIGN: RG analysis was conducted by a multidisciplinary panel of patients, clinicians and researchers (n=71). Eight working groups (WG) were constituted: discovery science; risk; prevention; early diagnosis and screening; pathology; curative treatment; stage IV disease; and living with and beyond CRC. A series of discussions led to development of draft papers by each WG, which were evaluated by a 20-strong patient panel. A final list of RGs and research recommendations (RR) was endorsed by all participants.RESULTS: Fifteen critical RGs are summarised below: RG1: Lack of realistic models that recapitulate tumour/tumour micro/macroenvironment; RG2: Insufficient evidence on precise contributions of genetic/environmental/lifestyle factors to CRC risk; RG3: Pressing need for prevention trials; RG4: Lack of integration of different prevention approaches; RG5: Lack of optimal strategies for CRC screening; RG6: Lack of effective triage systems for invasive investigations; RG7: Imprecise pathological assessment of CRC; RG8: Lack of qualified personnel in genomics, data sciences and digital pathology; RG9: Inadequate assessment/communication of risk, benefit and uncertainty of treatment choices; RG10: Need for novel technologies/interventions to improve curative outcomes; RG11: Lack of approaches that recognise molecular interplay between metastasising tumours and their microenvironment; RG12: Lack of reliable biomarkers to guide stage IV treatment; RG13: Need to increase understanding of health related quality of life (HRQOL) and promote residual symptom resolution; RG14: Lack of coordination of CRC research/funding; RG15: Lack of effective communication between relevant stakeholders.CONCLUSION: Prioritising research activity and funding could have a significant impact on reducing CRC disease burden over the next 5 years.</p
Triassic sedimentation and postaccretionary crustal evolution along the Solonker suture zone in Inner Mongolia, China
Detrital zircon U-Pb dating of the Xingfuzhilu Formation in southern Inner Mongolia yields a maximum depositional age of around 220āMa. The predominantly Permian and Triassic zircons are characterized by oscillatory zoning and euhedral shapes, with mostly positive zircon ĪµHf(t) values (+2.0 to +16.4), indicating that they were derived from a proximal magmatic source. Early-Middle Paleozoic zircons have variable zircon ĪµHf(t) values from ā6.2 to +11.2 and are characterized by weak oscillatory zoning and subhedral-subrounded shapes, suggesting that the sources are a proximal magmatic arc, possibly mixed with components of the Ondor Sum magmatic arc and the magmatic arc at the northern margin of the North China Craton. The remnants of Precambrian blocks in the southeastern Central Asian Orogenic Belt (CAOB), and the North China Craton may also have been a minor source region for the Xingfuzhilu succession. These results, combined with regional data, indicate that a closing remnant ocean basin or narrow seaway possibly existed in the Middle Permian (Guadalupian) immediately prior to final collision of the CAOB and closure of the Paleo-Asian Ocean. Subsequent collision resulted in the crustal uplift and thickening along the Solonker suture zone, accompanied by possible slab break-off and lithospheric delamination during the Latest Permian to Middle Triassic. The resultant orogen in the Late Triassic underwent exhumation and denudation of rocks in response to the postorogenic collapse and regional extension. Vertical crustal growth in the Triassic is documented by detrital zircons from the Xingfuzhilu Formation and appears to have been widespread across entire eastern CAOB
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