1,276 research outputs found
Investigating the Relationship Between Sulcogyral Patterns and Structural and Functional Connectivity Metrics in the Orbitofrontal Cortex
Located within the frontal lobe, the human orbitofrontal cortex (OFC) is widely known for its roles in sensory integration, emotion processing, decision-making, and goal-directed behaviors. Atypical structural organization of the OFC may explain atypical social or motivational behaviors displayed by individuals with brain disorders, such as bipolar disorder patients (BP).
The human brain can be imaged using magnetic resonance imaging (MRI) to reveal interesting aspects of the underlying brain architecture. This brain is composed of different tissue types, including gray and white matter, as well as various morphological features, including sulci & gyri. Within the OFC, the sulci can be labeled and classified into a finite number of patterns based on the continuity of the most medial and most lateral sulci. Typical patterns (Type I) have previously been found at higher frequencies bilaterally in healthy populations, whereas atypical patterns (Type II and Type III) have been found at higher frequencies in relative to patients with schizophrenia (SZ).
In order to characterize differences in morphological properties of structural OFC architecture in BP patients (N=46) relative to healthy controls (N=52), we trace OFC sulcogyral patterns based on a previously established protocol, employ a voxel-based morphometry (VBM) analysis to assess OFC gray matter (GM), and implement a diffusion tensor imaging (DTI) tractography analysis to measure white matter tract microstructural properties. Chi-square analysis compared sulcogyral pattern frequency distributions between groups, and independent sample t-tests compared additional OFC properties. Based on previous work and overlap of symptoms and genetics between BP and SZ, we predict that OFC architecture in BP individuals will differ from controls.
We find that BP displayed increased atypical (Type II and Type III) sulcal pattern frequencies relative to controls in the left hemisphere (χ2= 18.6, p \u3c 0.001). T-tests reveal that global OFC GM volumes were significantly decreased in both right (p = 0.0338) and left (p = 0.0039) hemispheres of BP relative to controls. BP also exhibit a reduced number of tracts in the uncinate fasciculus (UF) relative to controls on the left that trended toward significance (p = 0.094).
Overall, we find atypical OFC structural organization of sulcal patterns, reduced gray matter volume, and fewer white matter UF tracts in BP relative to controls, especially in the left hemisphere. Exploring and quantifying various structural brain properties within the OFC may be useful in assessing individual risk to brain dysfunction and facilitate a personalized approach for diagnosis and treatment
On the length of chains of proper subgroups covering a topological group
We prove that if an ultrafilter L is not coherent to a Q-point, then each
analytic non-sigma-bounded topological group G admits an increasing chain <G_a
: a of its proper subgroups such that: (i) U_{a in b(L)} G_a=G; and
For every sigma-bounded subgroup H of G there exists a such that H is a
subset of G_a. In case of the group Sym(w) of all permutations of w with the
topology inherited from w^w this improves upon earlier results of S. Thomas
Flow organization and heat transfer in turbulent wall sheared thermal convection
We perform direct numerical simulations of wall sheared Rayleigh-B\'enard
(RB) convection for Rayleigh numbers up to , Prandtl number unity, and
wall shear Reynolds numbers up to . Using the Monin-Obukhov length
we identify three different flow states, a buoyancy dominated regime
(; with the thermal
boundary layer thickness), a transitional regime (; with the height of the domain), and a shear dominated
regime (). In the buoyancy dominated regime the flow
dynamics are similar to that of turbulent thermal convection. The transitional
regime is characterized by rolls that are increasingly elongated with
increasing shear. The flow in the shear dominated regime consists of very
large-scale meandering rolls, similar to the ones found in conventional Couette
flow. As a consequence of these different flow regimes, for fixed and with
increasing shear, the heat transfer first decreases, due to the breakup of the
thermal rolls, and then increases at the beginning of the shear dominated
regime. For the Nusselt number effectively scales as
, with while we find
in the buoyancy dominated regime. In the transitional regime the effective
scaling exponent is , but the temperature and velocity profiles
in this regime are not logarithmic yet, thus indicating transient dynamics and
not the ultimate regime of thermal convection
The ultrafilter number for singular cardinals
We prove the consistency of a singular cardinal with small value of
the ultrafilter number , and arbitrarily large value of .Comment: 8 page
Quasi-selective ultrafilters and asymptotic numerosities
We isolate a new class of ultrafilters on N, called “quasi-selective” because they are intermediate between selective ultrafilters and P-points. (Under the Continuum Hypothesis these three classes are distinct.) The existence of quasi-selective ultrafilters is equivalent to the existence of “asymptotic numerosities” for all sets of tuples A ⊆ N^k. Such numerosities are hypernatural numbers that generalize finite cardinalities to countable point sets. Most notably, they maintain the structure of ordered semiring, and, in a precise sense, they allow for a natural extension of asymptotic density to all sets of tuples of natural numbers
Sub-unit cell layer-by-layer growth of Fe3O4, MgO, and Sr2RuO4 thin films
The use of oxide materials in oxide electronics requires their controlled
epitaxial growth. Recently, it was shown that Reflection High Energy Electron
Diffraction (RHEED) allows to monitor the growth of oxide thin films even at
high oxygen pressure. Here, we report the sub-unit cell molecular or block
layer growth of the oxide materials Sr2RuO4, MgO, and magnetite using Pulsed
Laser Deposition (PLD) from stoichiometric targets. Whereas for perovskites
such as SrTiO3 or doped LaMnO3 a single RHEED intensity oscillation is found to
correspond to the growth of a single unit cell, in materials where the unit
cell is composed of several molecular layers or blocks with identical
stoichiometry, a sub-unit cell molecular or block layer growth is established
resulting in several RHEED intensity oscillations during the growth of a single
unit-cell
Trustee: Full Privacy Preserving Vickrey Auction on top of Ethereum
The wide deployment of tokens for digital assets on top of Ethereum implies
the need for powerful trading platforms. Vickrey auctions have been known to
determine the real market price of items as bidders are motivated to submit
their own monetary valuations without leaking their information to the
competitors. Recent constructions have utilized various cryptographic protocols
such as ZKP and MPC, however, these approaches either are partially
privacy-preserving or require complex computations with several rounds. In this
paper, we overcome these limits by presenting Trustee as a Vickrey auction on
Ethereum which fully preserves bids' privacy at relatively much lower fees.
Trustee consists of three components: a front-end smart contract deployed on
Ethereum, an Intel SGX enclave, and a relay to redirect messages between them.
Initially, the enclave generates an Ethereum account and ECDH key-pair.
Subsequently, the relay publishes the account's address and ECDH public key on
the smart contract. As a prerequisite, bidders are encouraged to verify the
authenticity and security of Trustee by using the SGX remote attestation
service. To participate in the auction, bidders utilize the ECDH public key to
encrypt their bids and submit them to the smart contract. Once the bidding
interval is closed, the relay retrieves the encrypted bids and feeds them to
the enclave that autonomously generates a signed transaction indicating the
auction winner. Finally, the relay submits the transaction to the smart
contract which verifies the transaction's authenticity and the parameters'
consistency before accepting the claimed auction winner. As part of our
contributions, we have made a prototype for Trustee available on Github for the
community to review and inspect it. Additionally, we analyze the security
features of Trustee and report on the transactions' gas cost incurred on
Trustee smart contract.Comment: Presented at Financial Cryptography and Data Security 2019, 3rd
Workshop on Trusted Smart Contract
The Generic Model of Computation
Over the past two decades, Yuri Gurevich and his colleagues have formulated
axiomatic foundations for the notion of algorithm, be it classical,
interactive, or parallel, and formalized them in the new generic framework of
abstract state machines. This approach has recently been extended to suggest a
formalization of the notion of effective computation over arbitrary countable
domains. The central notions are summarized herein.Comment: In Proceedings DCM 2011, arXiv:1207.682
A General Framework for Sound and Complete Floyd-Hoare Logics
This paper presents an abstraction of Hoare logic to traced symmetric
monoidal categories, a very general framework for the theory of systems. Our
abstraction is based on a traced monoidal functor from an arbitrary traced
monoidal category into the category of pre-orders and monotone relations. We
give several examples of how our theory generalises usual Hoare logics (partial
correctness of while programs, partial correctness of pointer programs), and
provide some case studies on how it can be used to develop new Hoare logics
(run-time analysis of while programs and stream circuits).Comment: 27 page
A Vernacular for Coherent Logic
We propose a simple, yet expressive proof representation from which proofs
for different proof assistants can easily be generated. The representation uses
only a few inference rules and is based on a frag- ment of first-order logic
called coherent logic. Coherent logic has been recognized by a number of
researchers as a suitable logic for many ev- eryday mathematical developments.
The proposed proof representation is accompanied by a corresponding XML format
and by a suite of XSL transformations for generating formal proofs for
Isabelle/Isar and Coq, as well as proofs expressed in a natural language form
(formatted in LATEX or in HTML). Also, our automated theorem prover for
coherent logic exports proofs in the proposed XML format. All tools are
publicly available, along with a set of sample theorems.Comment: CICM 2014 - Conferences on Intelligent Computer Mathematics (2014
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