bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sample and realized minimum variance portfolios: Estimation, statistical inference, and tests
Authors: Golosnoy Vasyl , Gribisch Bastian , Seifert Miriam Isabel 
Published: May 2021

AbstractThe global minimum variance portfolio (GMVP) is the starting point of the Markowitz mean‐variance efficient frontier. The estimation of the GMVP weights is therefore of much importance for financial investors. The GMVP weights depend only on the inverse covariance matrix of returns on financial risky assets, for this reason the estimated GMVP weights are subject to substantial estimation risk, especially in high‐dimensional portfolio settings. In this paper we review the recent literature on traditional sample estimators for the unconditional GMVP weights which are typically based on daily asset returns, as well as on modern realized estimators for the conditional GMVP weights based on intraday high‐frequency returns. We present various types of GMVP estimators with the corresponding stochastic results, discuss statistical tests and point on some directions for further research. Our empirical application illustrates selected properties of realized GMVP weights.This article is categorized under:
Statistical and Graphical Methods of Data Analysis > Multivariate Analysis
Statistical and Graphical Methods of Data Analysis > Analysis of High Dimensional Data
Statistical Models > Multivariate Models
Seven challenges in the multiscale modeling of multicellular tissues
Authors: Fletcher Alexander G. , Osborne James M. 
Published: May 2021

AbstractThe growth and dynamics of multicellular tissues involve tightly regulated and coordinated morphogenetic cell behaviors, such as shape changes, movement, and division, which are governed by subcellular machinery and involve coupling through short‐ and long‐range signals. A key challenge in the fields of developmental biology, tissue engineering and regenerative medicine is to understand how relationships between scales produce emergent tissue‐scale behaviors. Recent advances in molecular biology, live‐imaging and ex vivo techniques have revolutionized our ability to study these processes experimentally. To fully leverage these techniques and obtain a more comprehensive understanding of the causal relationships underlying tissue dynamics, computational modeling approaches are increasingly spanning multiple spatial and temporal scales, and are coupling cell shape, growth, mechanics, and signaling. Yet such models remain challenging: modeling at each scale requires different areas of technical skills, while integration across scales necessitates the solution to novel mathematical and computational problems. This review aims to summarize recent progress in multiscale modeling of multicellular tissues and to highlight ongoing challenges associated with the construction, implementation, interrogation, and validation of such models.This article is categorized under:
Reproductive System Diseases > Computational Models
Metabolic Diseases > Computational Models
Cancer > Computational Models
Gravitational production of a conformal dark sector
Authors: Redi Michele , Tesi Andrea , Tillim Hannah 
Published: May 2021

Abstract
Dark sectors with purely gravitational couplings to the Standard Model are unavoidably populated from the SM plasma by graviton exchange, and naturally provide dark matter candidates. We examine the production in the relativistic regime where the dark sector is approximately scale invariant, providing general analytical formulas that depend solely on the central charge of the dark sector. We then assess the relevance of interactions that can lead to a variety of phenomena including thermalisation, non-perturbative mass gaps, out-of-equilibrium phase transitions and cannibalism in the dark sector. As an illustrative example we consider the dark glueball scenario in this light and show it to be a viable dark matter candidate due to the suppression of gravitational production. We go on to extend these results to strongly coupled CFTs and their holographic duals at large-N with the dark dilaton as the dark matter candidate.
Moduli-dependent Calabi-Yau and SU(3)-structure metrics from machine learning
Authors: Anderson Lara B. , Gerdes Mathis , Gray James , Krippendorf Sven , Raghuram Nikhil , Ruehle Fabian 
Published: May 2021

AbstractWe use machine learning to approximate Calabi-Yau and SU(3)-structure metrics, including for the first time complex structure moduli dependence. Our new methods furthermore improve existing numerical approximations in terms of accuracy and speed. Knowing these metrics has numerous applications, ranging from computations of crucial aspects of the effective field theory of string compactifications such as the canonical normalizations for Yukawa couplings, and the massive string spectrum which plays a crucial role in swampland conjectures, to mirror symmetry and the SYZ conjecture. In the case of SU(3) structure, our machine learning approach allows us to engineer metrics with certain torsion properties. Our methods are demonstrated for Calabi-Yau and SU(3)-structure manifolds based on a one-parameter family of quintic hypersurfaces in ℙ4.
Four-dimensional N = 1 theories, S-fold constraints on T-branes, and behaviors in IR and UV
Authors: Kimura Yusuke 
Published: May 2021

Abstract
We analyze four-dimensional (4d) N = 1 superconformal field theories (SCFTs) obtained as deformations of 4d N = 2 SCFTs on S-folds by tilting 7-branes. Geometric compatibility with the structures of S-folds constrains the forms of T-branes. As a result, brane monodromies are constrained. We also discuss two 4d N = 1 theories on probe D3-branes, where the two theories behave identically in IR, but they originate from different theories in UV. Studying the global structure of their geometry is useful in constructing these two theories.
A $$ T\overline{T} $$-like deformation of the Skyrme model and the Heisenberg model of nucleon-nucleon scattering
Authors: Nastase Horatiu , Sonnenschein Jacob 
Published: May 2021

Abstract
The Skyrme model, though it admits correctly a wide range of static properties of the nucleon, does not seem to reproduce properly the scattering behavior of nucleons at high energies. In this paper we present a $$ T\overline{T} $$
T

T
¯

-like deformation of it, inspired by a 1+1 dimensional model, in which boosted nucleons behave like shock waves. The scattering of the latter saturates the Froissart bound. We start by showing that 1+1 dimensional $$ T\overline{T} $$
T

T
¯

deformations of the free abelian pion action are in fact generalizations of the old Heisenberg model for nucleon-nucleon scattering, yielding the same saturation of the Froissart bound. We then deform the strong coupling limit of the bosonized action of multi-flavor QCD in two dimensions using the $$ T\overline{T} $$
T

T
¯

deformation of the WZW action with a mass term. We derive the classical soliton solution that corresponds to the nucleon, determine its mass and discuss its transformation into a shock-wave upon boosting. We uplift this action into a 3+1 dimensional $$ T\overline{T} $$
T

T
¯

-like deformation of the Skyrme action. We compare this deformed action to that of chiral perturbation theory. A possible holographic gravity dual interpretation is explored.
String scale thermal anti-de Sitter spaces
Authors: Ashok Sujay K. , Troost Jan 
Published: May 2021

Abstract
We study finite temperature string scale AdS3 backgrounds. One background is AdS3× S1× T2 in which the anti-de Sitter space-time and the circle are at the radius $$ \sqrt{\alpha^{\prime }} $$

α
′

. Using path integral techniques, we show that the bulk spectrum includes a continuum of states as well as Ramond-Ramond ground states that agree with those of the symmetric orbifold of the two-torus after second quantization. We also examine the one-loop free energy of the background AdS3× S1 at curvature radius $$ \sqrt{2{\alpha}^{\prime }/3} $$

2

α
′

/
3

. In the space-time NSNS sector, the string theory spontaneously breaks conformal symmetry as well as R-charge conjugation symmetry. We prove that the minimum in the boundary energy is reached for a singly wound string. In the RR sector, we classify the infinite set of ground states with fractional R-charges. Moreover, we remark on the behaviour of critical temperatures as the curvature scale becomes smaller than the string scale.In an appendix, we derive the Hawking-Page transition in string theory by integrating a world sheet one-point function.
Effective relational cosmological dynamics from quantum gravity
Authors: Marchetti Luca , Oriti Daniele 
Published: May 2021

Abstract
We discuss the relational strategy to solve the problem of time in quantum gravity and different ways in which it could be implemented, pointing out in particular the fundamentally new dimension that the problem takes in a quantum gravity context in which spacetime and geometry are understood as emergent. We realize concretely the relational strategy we have advocated in the context of the tensorial group field theory formalism for quantum gravity, leading to the extraction of an effective relational cosmological dynamics from quantum geometric models. We analyze in detail the emergent cosmological dynamics, highlighting the improvements over previous work, the contribution of the quantum properties of the relational clock to it, and the interplay between the conditions ensuring a bona fide relational dynamics throughout the cosmological evolution and the existence of a quantum bounce resolving the classical big bang singularity.
Microwave scan and brain biomarkers to rule out intracranial hemorrhage: study protocol of a planned prospective study (MBI01)
Authors: Vedin Tomas , Bergenfeldt Henrik , Holmström Emanuel , Lundager-Forberg Jakob , Edelhamre Marcus 
Published: May 2021

Abstract
Purpose
The aim of this planned study is to evaluate the ability of a cranial microwave scanner in conjunction with nine brain biomarkers (Aβ40, Aβ42, GFAP, H-FABP, S100B, NF-L, NSE, UCH-L1 and IL-10) to detect and rule out traumatic intracranial hemorrhage in an emergency department setting. Traumatic brain injury is a world-wide topic of interest for researchers and clinicians. It affects 2% of the population per annum and presents challenges for physicians as patients’ initial signs and symptoms do not always correlate with the extent of brain injury. The gold standard for diagnosis of intracranial hemorrhage is head computerized tomography (CT) with the drawbacks of high cost and radiation exposure. A fast, secure way of diagnosing without these drawbacks has potential to make care more effective and reduce cost.

Methods
Study will be prospective and enroll adult, consenting patients with head trauma who seek emergency department care. Only patients where the treating physician prescribes a head-CT will be included. The microwave scan and blood sampling will be performed in close temporal proximity to the CT scan. Results will be analyzed with sensitivity, specificity and receiver operator characteristics analysis to provide the best combination of a number of biomarkers and the microwave scan.

Conclusion
This study will explore the diagnostic accuracy of a head microwave scanner in combination with biomarkers in ruling out intracranial hemorrhage in traumatic brain injury patients presenting to the emergency department. Potentially, this combined diagnostic approach could achieve both high sensitivity and high specificity, thereby reducing the need of CT-head scans when managing these patients.
Clinicaltrials.gov identifier: NCT04666766. Registered December 11, 2020.
Unklare chronische Schwindelsyndrome – Erfahrungen mit einem interdisziplinären stationären Diagnostikkonzept
Authors: Münst J. , Pudszuhn A. , v. Bernstorff M. , Obermueller T. , Erdur H. , Audebert H. J. , Rose M. , Reisshauer A. , Hoffmann I. , Schönfeld U. , Hofmann V. M. 
Published: May 2021

ZusammenfassungSchwindel ist ein häufiges Leitsymptom. Insbesondere Patienten mit chronischen Schwindelsyndromen erleben eine deutliche Beeinträchtigung der Lebensqualität und bei Berufstätigen eine Einschränkung der Arbeitsfähigkeit. Folgen sind finanzielle und kapazitive Belastungen des Gesundheitssystems aufgrund von häufigen Mehrfachuntersuchungen und Krankschreibungen bis hin zur Erwerbsunfähigkeit der Betroffenen. Bei 150 Patienten mit in der ambulanten Diagnostik unklaren chronischen Schwindelsyndromen wurde auf der Grundlage eines strukturierten interdisziplinären stationären Diagnostikkonzepts bei über 90 % der Fälle mindestens eine die Beschwerden begründende Diagnose erhoben. Chronische Schwindelsyndrome sind häufig multifaktoriell bedingt. Bei mehr als der Hälfte der Patienten fanden sich u. a. psychosomatische (Begleit‑)Diagnosen. Zielführende therapeutische Empfehlungen können nur diagnosespezifisch erfolgen, weshalb in dauerhaft unklaren Fällen auch die Abklärung im Rahmen eines interdisziplinären stationären Diagnostikkonzepts sinnvoll und gerechtfertigt sein kann.
Genome-wide association mapping of sodium and potassium concentration in rice grains and shoots under alternate wetting and drying and continuously flooded irrigation
Authors: Chen Caijin , Travis Anthony J. , Hossain Mahmud , Islam Md Rafiqul , Price Adam H. , Norton Gareth J. 
Published: May 2021

AbstractKey messageIdentification of a large number of QTL and candidate genes for sodium accumulation in a field grown population of rice derived from theaussubpopulation.AbstractRice (Oryza sativaL.) is a globally important cereal crop. Sodium (Na+) and potassium (K+) are the major monovalent ions which affect rice growth, and exploring their uptake mechanisms will be useful for understanding rice biology. Since the balance of Na+and K+plays a significant role in adaptation of rice to salinity, that biology might inform the search for tolerance. In this study, the Na+and K+concentration and Na+/K+ratio in grains and shoots were analyzed in the Bengal and Assam Aus Panel grown in field conditions under continuously flooded (CF) and alternate wetting and drying (AWD) irrigation. Overall, AWD irrigation significantly reduced the Na+concentration and increased the K+concentration in shoots and grains compared to the plants grown under CF. Genome-wide association mapping was conducted on Na+, K+concentration and Na+/K+ratio with 2 million SNPs using an efficient mixed model. Only QTLs which contained more than two significant SNPs (p < 0.0001) and where at least one of these significant SNPs passed a 10% false discovery rate were reported. A total of 106 QTLs were identified as being associated with Na+concentration and Na+/K+ratio across all traits and field conditions, with 48 QTLs found in multiple traits and/or water conditions. Four notable QTLs (one each on chromosomes 1 and 11, two on chromosome 2) and the haplotype variants of four candidate genes (OsHKT1;5,OsNHX2,LOC_Os02g32490andOsFAD2_1) are discussed. The QTLs/candidate genes identified here could be useful for breeding rice that accumulates lower concentrations of sodium.
Gain and loss of function mutations in biological chemical reaction networks: a mathematical model with application to colorectal cancer cells
Authors: Sommariva Sara , Caviglia Giacomo , Piana Michele 
Published: May 2021

AbstractThis paper studies a system of Ordinary Differential Equations modeling a chemical reaction network and derives from it a simulation tool mimicking Loss of Function and Gain of Function mutations found in cancer cells. More specifically, from a theoretical perspective, our approach focuses on the determination of moiety conservation laws for the system and their relation with the corresponding stoichiometric surfaces. Then we show that Loss of Function mutations can be implemented in the model via modification of the initial conditions in the system, while Gain of Function mutations can be implemented by eliminating specific reactions. Finally, the model is utilized to examine in detail the G1-S phase of a colorectal cancer cell.
The Carers’ Needs Assessment for Dementia (CNA-D): a validation study in the Italian population
Authors: Zucca Milena , Rubino Elisa , Vacca Alessandro , De Martino Paola , Caglio Marcella , Marcinnó Andrea , Bo Mario , Rainero Innocenzo 
Published: May 2021

Abstract
Background
Dementia has devastating consequences for families with important physical, psychological, social, and financial effects. Evaluation of caregiver’s needs may be an important step to reduce the burden of family caregivers of dementia patients. An Austrian scale, the Carers’ Needs Assessment for Dementia, is now available for measuring the caregiver’s needs. The aim of our study was to evaluate the psychometric properties of the Italian version of the CNA-D (iCNA-D).

Methods
A sample of 214 voluntary caregivers of dementia patients was recruited at the Department of Neuroscience, University of Turin (Italy). All participants were administered the iCNA-D. Validity and reliability of the instrument were evaluated using Beck Depression Inventory (BDI), Beck Anxiety Inventory (BAI), Symptom Checklist-90 (SCL-90), and the Italian version of Zarit Burden Interview (I-ZBI).

Results
The most common unmet need reported for the iCNA-D was “counseling and emotional support” (31.5%). This item demonstrates adequate reliability with moderate internal consistency for all “summary scores” of iCNA-D (α ≥ 0.75) and split-half correlation of more than 0.80 for two of them. We also found positive correlations in two out of three “summary scores” of iCNA-D and in the overall outcomes of BDI, BAI, SCL-90, and I-ZBI.

Conclusions
The iCNA-D could be a valid and reliable tool for a comprehensive assessment of needs and possible social supports proposed to relatives who take care of patients with dementia. Better understanding of family caregivers’ needs could improve planning of local services and reduce caregivers’ perception of distress and burden.
A study on using data clustering for feature extraction to improve the quality of classification
Authors: Piernik Maciej , Morzy Tadeusz 
Published: May 2021

AbstractThere is a certain belief among data science researchers and enthusiasts alike that clustering can be used to improve classification quality. Insofar as this belief is fairly uncontroversial, it is also very general and therefore produces a lot of confusion around the subject. There are many ways of using clustering in classification and it obviously cannot always improve the quality of predictions, so a question arises, in which scenarios exactly does it help? Since we were unable to find a rigorous study addressing this question, in this paper, we try to shed some light on the concept of using clustering for classification. To do so, we first put forward a framework for incorporating clustering as a method of feature extraction for classification. The framework is generic w.r.t. similarity measures, clustering algorithms, classifiers, and datasets and serves as a platform to answer ten essential questions regarding the studied subject. Each answer is formulated based on a separate experiment on 16 publicly available datasets, followed by an appropriate statistical analysis. After performing the experiments and analyzing the results separately, we discuss them from a global perspective and form general conclusions regarding using clustering as feature extraction for classification.
Structural change detection applying long-term seismic interferometry by deconvolution method to a modern civil engineering structure (New Zealand)
Authors: Skłodowska Anna Maria , Holden Caroline , Guéguen Philippe , Finnegan John , Sidwell Geoff 
Published: May 2021

AbstractPulse-wave propagation velocity and resonance frequency measured in civil engineering structures are both related to structural design. Monitoring their variation following seismic strong shaking provides information about the immediate building capacity. Joint-interpretation of frequency and velocity variation requires a better understanding of the processes controlling seismic structural health. In this study, we analysed 8 years of earthquake data recorded by the vertical array installed in the Te Puni building in Wellington, New Zealand, as part of the GeoNet building instrumentation programme. Co-seismic variations of pulse wave velocity and fundamental frequency are analysed and interpreted through a Timoshenko beam-like building model. This study shows that even though no structural damage was visually reported over the considered time of monitoring, co- and post-seismic variation of both parameters’ values are observed for almost all earthquakes, including a permanent shift following strong ground shaking. Variations of pulse-wave velocity and resonance frequency are cross-interpreted in terms of the building model. They reflect a time variant building response, correlated with the seismic loading. In addition, time delay of the pulse-wave velocity as a function of the building height provides relevant information on the location of the changes and confirms the efficient cross-interpretation of both methods for seismic Structural Health monitoring.
Maternal hypertensive disorders and neurodevelopmental disorders in offspring: a population-based cohort in two Nordic countries
Authors: Wang Hui , László Krisztina D. , Gissler Mika , Li Fei , Zhang Jun , Yu Yongfu , Li Jiong 
Published: May 2021

AbstractMaternal hypertensive disorders during pregnancy (HDP) have been associated with neuropsychiatric problems in offspring. We aim to investigate the associations between specific types of maternal HDP and offspring neurodevelopmental disorders and further examine whether the timing of onset and severity of HDP would affect these associations. The study population consisted of 4,489,044 live-born singletons in Denmark during 1978–2012 and Sweden during 1987–2010. Maternal HDP was categorized into chronic hypertension, gestational hypertension, and pre-eclampsia; pre-eclampsia was further stratified according to timing (early-onset, late-onset), or severity (moderate, severe) of the disease. Neurodevelopmental disorders, including attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and intellectual disability (ID), were defined by ICD-coded register diagnosis. Cox regression was used to calculate hazard ratios (HR) while adjusting for potential confounders, and sibling analyses assessed the influence of unmeasured shared familial factors. Maternal HDP was associated with increased risks of ADHD (HR, 1.24; 95% confidence interval [CI], 1.20–1.28), ASD (1.29 [1.24–1.34]), and ID (1.58 [1.50–1.66]) in offspring, respectively, which was mostly driven by pre-eclampsia. The strongest associations were observed for early-onset and severe pre-eclampsia, and the corresponding HRs for ADHD, ASD and ID were 1.93 [1.73–2.16], 1.86 [1.61–2.15], and 3.99 [3.42–4.65], respectively. The results were similar in the sibling analyses. The associations between maternal HDP and offspring neurodevelopmental disorders were consistent across the subgroups of sex, preterm status, parity, maternal age and psychiatric disorders. Maternal HDP, especially early-onset pre-eclampsia, are associated with increased risks of ADHD, ASD, and ID in particular, independent of shared familial factors.