bluuebunny/crossref_metadata_2025 huggingface dataset:
Symmetries and covering maps for the minimal tension string on AdS3 × S3 × T4
Authors: McStay N. M. , Reid-Edwards R. A.
Published: April 2024

Abstract

This paper considers a recently-proposed string theory on AdS3 × S3 × T4 with one unit of NS-NS flux (k = 1). We discuss interpretations of the target space, including connections to twistor geometry and a more conventional spacetime interpretation via the Wakimoto representation. We propose an alternative perspective on the role of the Wakimoto formalism in the k = 1 string, for which no large radius limit is required by the inclusion of extra operator insertions in the path integral. This provides an exact Wakimoto description of the worldsheet CFT. We also discuss an additional local worldsheet symmetry, Q(z), that emerges when k = 1 and show that this symmetry plays an important role in the localisation of the path integral to a sum over covering maps. We demonstrate the emergence of a rigid worldsheet translation symmetry in the radial direction of the AdS3, for which again the presence of Q(z) is crucial. We conjecture that this radial symmetry plays a key role in understanding, in the case of the k = 1 string, the encoding of the bulk physics on the two-dimensional boundary.
Indirect detection of dark matter with (pseudo)-scalar interactions
Authors: Biondini Simone , Bollig Julian , Vogl Stefan
Published: April 2024

Abstract

Indirect detection is one of the most powerful methods to search for annihilating dark matter. In this work, we investigate the impact of non-perturbative effects in the indirect detection of dark matter. For this purpose we utilize a minimal model consisting of a fermionic dark matter candidate in the TeV mass range that interacts via scalar- and pseudo-scalar interactions with a massive scalar mediator mixing with the Higgs. The scalar interaction induces an attractive Yukawa potential between dark matter particles, such that annihilations are Sommerfeld enhanced, and bound states can form. These non-perturbative effects are systematically dealt with (potential) non-relativistic effective field theories and we derive the relevant cross sections for dark matter. We discuss their impact on the relic density and indirect detection. Annihilations in dwarf galaxies and the Galactic Center require special care and we derive generalized J-factors for these objects that account for the non-trivial velocity dependence of the cross sections in our model. We use limits on the gamma-ray flux based on Fermi-LAT observations and limits on the rate of exotic energy injection from Planck to derive bounds on the parameter space of the model. Finally, we estimate the impact that future limits from the Cherenkov Telescope Array are expected to have on the model.
Riemann zeros as quantized energies of scattering with impurities
Authors: LeClair André , Mussardo Giuseppe
Published: April 2024

Abstract

We construct an integrable physical model of a single particle scattering with impurities spread on a circle. The S-matrices of the scattering with the impurities are such that the quantized energies of this system, coming from the Bethe Ansatz equations, correspond to the imaginary parts of the non-trivial zeros of the the Riemann ζ(s) function along the axis $$\mathfrak{R}\left(s\right)=\frac{1}{2}$$ of the complex s-plane. A simple and natural generalization of the original scattering problem leads instead to Bethe Ansatz equations whose solutions are the non-trivial zeros of the Dirichlet L-functions again along the axis $$\mathfrak{R}\left(s\right)=\frac{1}{2}$$. The conjecture that all the non-trivial zeros of these functions are aligned along this axis of the complex s-plane is known as the Generalised Riemann Hypothesis (GRH). In the language of the scattering problem analysed in this paper the validity of the GRH is equivalent to the completeness of the Bethe Ansatz equations. Moreover the idea that the validity of the GRH requires both the duality equation (i.e. the mapping s → 1 – s) and the Euler product representation of the Dirichlet L-functions finds additional and novel support from the physical scattering model analysed in this paper. This is further illustrated by an explicit counterexample provided by the solutions of the Bethe Ansatz equations which employ the Davenport-Heilbronn function $$\mathcal{D}\left(s\right)$$, i.e. a function whose completion satisfies the duality equation χ(s) = χ(1 – s) but that does not have an Euler product representation. In this case, even though there are infinitely many solutions of the Bethe Ansatz equations along the axis $$\mathfrak{R}\left(s\right)=\frac{1}{2}$$, there are also infinitely many pairs of solutions away from this axis and symmetrically placed with respect to it.
Global solutions to the Kirchhoff equation with spectral gap data in the energy space
Authors: Ghisi Marina , Gobbino Massimo
Published: April 2024

We prove that the classical hyperbolic Kirchhoff equation admits global-in-time solutions for some classes of initial data in the energy space. We also show that there are enough such solutions so that every initial datum in the energy space is the sum of two initial data for which a global-in-time solution exists. The proof relies on the notion of spectral gap data, namely initial data whose components vanish for large intervals of frequencies. We do not pass through the linearized equation, because it is not well-posed at this low level of regularity.
The role of the immunosuppressive PD-1/PD-L1 checkpoint pathway in the aging process and age-related diseases
Authors: Salminen Antero
Published: April 2024

The accumulation of senescent cells within tissues is a hallmark of the aging process. Senescent cells are also commonly present in many age-related diseases and in the cancer microenvironment. The escape of abnormal cells from immune surveillance indicates that there is some defect in the function of cytotoxic immune cells, e.g., CD8+ T cells and natural killer (NK) cells. Recent studies have revealed that the expression of programmed death-ligand 1 (PD-L1) protein is abundantly increased in senescent cells. An increase in the amount of PD-L1 protein protects senescent cells from clearance by the PD-1 checkpoint receptor in cytotoxic immune cells. In fact, the activation of the PD-1 receptor suppresses the cytotoxic properties of CD8+ T and NK cells, promoting a state of immunosenescence. The inhibitory PD-1/PD-L1 checkpoint pathway acts in cooperation with immunosuppressive cells; for example, activation of PD-1 receptor can enhance the differentiation of regulatory T cells (Treg), myeloid-derived suppressor cells (MDSC), and M2 macrophages, whereas the cytokines secreted by immunosuppressive cells stimulate the expression of the immunosuppressive PD-L1 protein. Interestingly, many signaling pathways known to promote cellular senescence and the aging process are crucial stimulators of the expression of PD-L1 protein, e.g., epigenetic regulation, inflammatory mediators, mTOR-related signaling, cGAS-STING pathway, and AhR signaling. It seems that the inhibitory PD-1/PD-L1 immune checkpoint axis has a crucial role in the accumulation of senescent cells and thus it promotes the aging process in tissues. Thus, the blockade of the PD-1/PD-L1 checkpoint signaling might be a potential anti-aging senolytic therapy.

Key messages

Senescent cells accumulate within tissues during aging and age-related diseases.

Senescent cells are able to escape immune surveillance by cytotoxic immune cells.

Expression of programmed death-ligand 1 (PD-L1) markedly increases in senescent cells.

Age-related signaling stimulates the expression of PD-L1 protein in senescent cells.

Inhibitory PD-1/PD-L1 checkpoint pathway suppresses clearance of senescent cells.
Seltene Differenzialdiagnose bei osteolytischer Läsion des Unterkiefers einer jungen Erwachsenen
Authors: Shin Hyunkyu , Naros Andreas , Kieninger Sinja , Polligkeit Joachim , Fend Falko , Milla Jakob
Published: April 2024

Wir stellen einen seltenen Fall mit hämatologischer Neoplasie bei einer jungen Erwachsenen vor, welche zuerst 2008 beschrieben wurde und seit 2022 in beide gängigen Tumorklassifikationssysteme hämatologischer Neoplasien, ICC und WHO, aufgenommen wurde. Diese Neoplasie zeigt eine charakteristische immunhisthochemische ALK-Positivität und entsprechend molekular ein ALK-Fusionsgen. Patholg*innen sollten diese Entität kennen, zumal eine Unterscheidung zwischen dieser Erkrankung und anderen häufiger auftretenden Erkrankungen des gleichen Formenkreises sowie einer mesenchymalen Neoplasie mit ALK-Aberration herausfordernd ist.
Strong Symmetry Breaking in Coupled, Identical Lengyel–Epstein Oscillators via Folded Singularities
Authors: Awal Naziru M. , Epstein Irving R. , Kaper Tasso J. , Vo Theodore
Published: April 2024

We study pairs of symmetrically coupled, identical Lengyel-Epstein oscillators, where the coupling can be through both the fast and slow variables. We find a plethora of strong symmetry breaking rhythms, in which the two oscillators exhibit qualitatively different oscillations, and their amplitudes differ by as much as an order of magnitude. Analysis of the folded singularities in the coupled system shows that a key folded node, located off the symmetry axis, is the primary mechanism responsible for the strong symmetry breaking. Passage through the neighborhood of this folded node can result in splitting between the amplitudes of the oscillators, in which one is constrained to remain of small amplitude, while the other makes a large-amplitude oscillation or a mixed-mode oscillation. The analysis also reveals an organizing center in parameter space, where the system undergoes an asymmetric canard explosion, in which one oscillator exhibits a sequence of limit cycle canards, over an interval of parameter values centered at the explosion point, while the other oscillator executes small amplitude oscillations. Other folded singularities can also impact properties of the strong symmetry breaking rhythms. We contrast these strong symmetry breaking rhythms with asymmetric rhythms that are close to symmetric states, such as in-phase or anti-phase oscillations. In addition to the symmetry breaking rhythms, we also find an explosion of anti-phase limit cycle canards, which mediates the transition from small-amplitude, anti-phase oscillations to large-amplitude, anti-phase oscillations.
Staged neurosurgical approach for giant and progressive neonatal arachnoid cysts: a case series and review of the literature
Authors: Peraud Aurelia , Schuler-Ortoli Marie , Schaal Matthias , Reister Frank , Ehrhardt Harald , Friebe-Hoffmann Ulrike
Published: April 2024

Objectives

Prenatally diagnosed complex arachnoid cysts are very rare. While the true prenatal incidence is still unknown, they account for approximately 1% of intracranial masses in newborns. They rarely exhibit rapid growth or cause obstructive hydrocephalus, but if they increase to such a dimension during pregnancy, the ideal management is not well established. We present our detailed perinatal experience, covering prenatal diagnosis, a compassionate delivery process, and neonatal stabilization. Finally, a thorough postnatal neurosurgical intervention was performed. Initially, our focus was on the gradual reduction of cyst size as a primary effort, followed by subsequent definitive surgical treatment.

Methods

This case series shows the treatment course of three fetuses with antenatally diagnosed large arachnoid cysts. We present pre- and postnatal management and imaging, as well as the surgical treatment plan and the available clinical course during follow-up.

Results

Two girls and one boy were included in the current review. All three cases presented with prenatally diagnosed complex arachnoid cysts that increased in size during pregnancy. The mean gestational age at delivery was 35 weeks (range 32 to 37 weeks), and all patients were delivered by a caesarian section. Increasing head circumference and compression of brain structures were indications for delivery, as they are associated with a high risk of excess intracranial pressures and CSF diapedesis, as well as traumatic delivery and maternal complications. All cysts were supratentorial in location; one expanded into the posterior fossa, and one was a multicompartment cyst. All children underwent an initial surgical procedure within the first days of life. To relieve cyst pressure and achieve a reduction in head circumference, an ultrasound-guided or endoscopic-assisted internal shunt with drainage of the cyst to the ventricles or subdural/subarachnoid space was inserted. Definite surgical therapy consisted of cyst marsupialization and/or cysto-peritoneal shunt implantation. All children survived without severe neurodevelopmental impairments.

Conclusion

With the cases presented, we demonstrate that the slow reduction of immense cyst size as an initial procedure until optimal requirements for final surgical treatment were achieved has proven to be optimal for neurological outcome. Special emphasis has to be taken on the delicate nature of premature newborn babies, and surgical steps have to be thoroughly considered within the interdisciplinary team.
Comparative analysis of linear- and circular-stapled gastrojejunostomies in Roux-en-Y gastric bypass: a focus on postoperative morbidity using the comprehensive complication index
Authors: Sadiku Floni , Alceste Daniela , Serra Michele , Hehl Stefanie Josefine , Gero Daniel , Thalheimer Andreas , Bueter Marco , Widmer Jeannette
Published: April 2024

Purpose

The linear-stapled (LSA) and the circular-stapled anastomosis (CSA) are the two most commonly performed techniques for the gastrojejunostomy (GJ) during laparoscopic Roux-en-Y gastric bypass (RYGB). This study compared the outcome after both techniques with special focus on postoperative morbidity using the comprehensive complication index (CCI).

Methods

Five hundred eighty-eight patients operated between 01/2010 and 12/2019 were included in the final analysis and divided in two cohorts according to the surgical technique of the GJ (LSA (n = 290) or CSA (n = 298)). Before 09/2016, the CSA was exclusively performed for the GJ, while after 09/2016, the LSA was solely used.

Results

The mean CCI for patients with Clavien-Dindo complication grade ≥ 2 within the first 90 days after RYGB was 31 ± 9.1 in the CSA and 25.7 ± 6.8 in the LSA group (p < 0.001), both values still below the previously published benchmark cutoff (≤ 33.73). The C-reactive Protein (CRP)-levels on postoperative days (POD) 1 and 3 as well as the use of opioids on POD 1 were significantly higher in the CSA- than in the LSA-group (all p < 0.001). There were significantly more internal herniations in the CSA group during the first 24 postoperative months (p < 0.001).

Conclusion

Patients after RYGB with CSA were found to have higher CCI values during the first 90 PODs compared to patients in which the LSA was applied. To achieve optimal outcomes in terms of patient morbidity, the LSA seems to be the superior technique for GJ in RYGB.
Long-term quality of life after hybrid robot-assisted and open Ivor Lewis esophagectomy for esophageal cancer in a single center: a comparative analysis
Authors: Neuschütz Kerstin J. , Fourie Lana , Germann Nicolas , Pieters Anouk , Däster Silvio , Angehrn Fiorenzo V. , Klasen Jennifer M. , Müller-Stich Beat P. , Steinemann Daniel C. , Bolli Martin
Published: April 2024

Purpose

Due to improved survival of esophageal cancer patients, long-term quality of life (QoL) is increasingly gaining importance. The aim of this study is to compare QoL outcomes between open Ivor Lewis esophagectomy (Open-E) and a hybrid approach including laparotomy and a robot-assisted thoracic phase (hRob-E). Additionally, a standard group of healthy individuals serves as reference.

Methods

With a median follow-up of 36 months after hRob-E (n = 28) and 40 months after Open-E (n = 43), patients’ QoL was assessed using the European Organization for Research and Treatment of Cancer (EORTC) QoL Questionnaire Core 30 (QLQ-C30) and the EORTC Esophagus specific QoL questionnaire 18 (QLQ-OES18).

Results

Patients showed similar clinical-pathological characteristics, but hRob-E patients had significantly higher ASA scores at surgery (p < 0.001). Patients and healthy controls reported similar global health status and emotional and cognitive functions. However, physical functioning of Open-E patients was significantly reduced compared to healthy controls (p = 0.019). Operated patients reported reduced role and social functioning, fatigue, nausea and vomiting, dyspnea, and diarrhea. A trend towards a better pain score after hRob-E compared to Open-E emerged (p = 0.063). Regarding QLQ-OES18, hRob-E- and Open-E-treated patients similarly reported eating problems, reflux, and troubles swallowing saliva.

Conclusions

The global health status is not impaired after esophagectomy. Despite higher ASA scores, QoL of hRob-E patients is similar to that of patients operated with Open-E. Moreover, patients after hRob-E appear to have a better score regarding physical functioning and a better pain profile than patients after Open-E, indicating a benefit of minimally invasive surgery.
Successful adaptation of twinning concept for global neurosurgery collaborations—a validation study
Authors: Corell Alba , Jabang John N. , Manneh Job , Manneh Ebrima K. , Tisell Magnus , Brandt Christian , Majing Tomas , Smedberg Camilla , Förars Charlotte , Rebucas Sarinah , Goswell Pascal , Ronold Tove , Landén Caroline , Engström Anders , Sorto Pia , Uche Enoch , Wague Daouda , Sakho Youssoupha , Sundblom Jimmy
Published: April 2024

Introduction

Globally, many regions have an urgent, unmet need of neurosurgical care. A multi-step neurosurgical twinning technique, International Neurosurgical Twinning Modeled for Africa (INTIMA), was proved to be successful during a previous mission to Neurosurgical Unit, Enugu, Nigeria. The Swedish African Neurosurgical Collaboration (SANC) performed a developmental mission together with the local neurosurgical unit in The Gambia, adopting the INTIMA model.

Methods

A multidisciplinary team visited for a 2-week collaborative mission at the Neurosurgical Department of the Edward Francis Small Teaching Hospital in Banjul, The Gambia. The mission followed the data of neurosurgical operations during and after the mission as well as about the operations 3 months prior to and after the mission was collected.

Results

During the mission, a total of 22 operations was carried out, the most common being degenerative spinal conditions (n = 9). In the 3 months following the mission, 43 operations were performed compared to 24 during the 3 months leading up to the mission. The complexity of the performed procedures increased after the mission. An operating microscope (Möller-Wedel) was donated and installed and the neurosurgeons on site underwent training in microneurosurgery. The surgical nurses, nurses at the postoperative ward, and the physiotherapists underwent training. A biomedical engineer serviced multiple appliances and devices improving the patient care on site while training local technicians.

Conclusion

This study validated the use of the INTIMA model previously described in a mission by Swedish African Neurosurgical Collaboration (SANC). The model is sustainable and produces notable results. The core strength of the model is in the multidisciplinary team securing all the aspects and steps of the neurosurgical care. Installation of an operating microscope opened for further microsurgical possibilities, improving the neurosurgical care in The Gambia.
Parkinson's disease and vitamins: a focus on vitamin B12
Authors: Rekik Arwa , Santoro Carlo , Poplawska-Domaszewicz Karolina , Qamar Mubasher Ahmad , Batzu Lucia , Landolfo Salvatore , Rota Silvia , Falup-Pecurariu Cristian , Murasan Iulia , Chaudhuri Kallol Ray
Published: April 2024

Parkinson’s disease (PD) has been linked to a vast array of vitamins among which vitamin B12 (Vit B12) is the most relevant and often investigated specially in the context of intrajejunal levodopa infusion therapy. Vit B12 deficiency, itself, has been reported to cause acute parkinsonism. Nevertheless, concrete mechanisms through which B12 deficiency interacts with PD in terms of pathophysiology, clinical manifestation and progression remains unclear. Recent studies have suggested that Vit B12 deficiency along with the induced hyperhomocysteinemia are correlated with specific PD phenotypes characterized with early postural instability and falls and more rapid motor progression, cognitive impairment, visual hallucinations and autonomic dysfunction. Specific clinical features such as polyneuropathy have also been linked to Vit B12 deficiency specifically in context of intrajejunal levodopa therapy. In this review, we explore the link between Vit B12 and PD in terms of physiopathology regarding dysfunctional neural pathways, neuropathological processes as well as reviewing the major clinical traits of Vit B12 deficiency in PD and Levodopa-mediated neuropathy. Finally, we provide an overview of the therapeutic effect of Vit B12 supplementation in PD and posit a practical guideline for Vit B12 testing and supplementation.
Cellulosic fibers spun from stabilized imidazolium ionic liquids: identification of chromophores in the fibers after accelerated ageing
Authors: Rosenau Thomas , Potthast Antje , Zhang Jiaping , Barbini Stefano , Koide Mitsuharu , Rinner Uwe , Hettegger Hubert
Published: April 2024

Cellulosic fibers spun from 1,3-dialkylimidazolium ionic liquids are effectively stabilized against cellulose degradation by the addition of antioxidants, but this protective effect comes at the expense of chromophore generation from the degradation products of the stabilizers. In this study, we identified the oxidation and degradation products of four natural antioxidants, α-tocopherol, N-methyl-α-tocopheramine, propyl gallate, and hydroxytyrosol, formed upon accelerated ageing of the fibers. Ageing was performed according to standard protocols under either dry or moist conditions and the extraction was done with supercritical carbon dioxide. Chromophore formation in spinning dope, upon dry ageing and moist ageing were compared. In total, 16 different oxidation/degradation products were isolated, their structure confirmed by comprehensive analytical characterization with full NMR resonance assignment in the 1H and 13C domains as well as by comparison with authentic samples, and their formation pathways discussed. Knowledge of the chemical structures of the degradation products originating from the stabilizers now provides a good starting point for optimization of the fiber bleaching stage.

Graphical abstract
Using a NEAT approach with curriculums for dynamic content generation in video games
Authors: Hind Daniel , Harvey Carlo
Published: April 2024

This paper presents a novel exploration of the use of an evolving neural network approach to generate dynamic content for video games, specifically for a tower defence game. The objective is to employ the NeuroEvolution of Augmenting Topologies (NEAT) technique to train a NEAT neural network as a wave manager to generate enemy waves that challenge the player’s defences. The approach is extended to incorporate NEAT-generated curriculums for tower deployments to gradually increase the difficulty for the generated enemy waves, allowing the neural network to learn incrementally. The approach dynamically adapts to changes in the player’s skill level, providing a more personalised and engaging gaming experience. The quality of the machine-generated waves is evaluated through a blind A/B test with the Games Experience Questionnaire (GEQ), and results are compared with manually designed human waves. The study finds no discernible difference in the reported player experience between AI and human-designed waves. The approach can significantly reduce the time and resources required to design game content while maintaining the quality of the player experience. The approach has the potential to be applied to a range of video game genres and within the design and development process, providing a more personalised and engaging gaming experience for players.
Respiratory outcomes after cleft palate closure in Robin sequence: a retrospective study
Authors: Sullivan Nathaniel A. T. , Lachkar Nadia , Don Griot J. Peter W. , Kruisinga Frea H. , Leeuwenburgh-Pronk Wendela G. , Broers Chantal J. M. , Breugem Corstiaan C.
Published: April 2024

Objectives

There is a paucity of information about the possible risk factors that could identify patients with Robin sequence (RS) who are more prone to developing obstructive airway complications after palate closure. This study aimed to compare the respiratory complication rates in patients with RS and isolated cleft palate (ICP).

Materials and methods

In this retrospective study, we reviewed the medical records of 243 consecutive patients with RS and ICP who were treated at Amsterdam University Medical Centers over the past 25 years. We collected preoperative data on previous treatment, diagnostic findings, surgical technique, weight, and presence of congenital anomalies.

Results

During cleft palate closure, patients with RS were older (11.9 versus 10.1 months; p = 0.001) and had a lower gestational age than those with ICP (37.7 versus 38.5 weeks; p = 0.002). Patients with RS had more respiratory complications (17 versus 5%; p = 0.005), were more often non-electively admitted to the pediatric intensive care unit (PICU) (13 versus 4.1%; p = 0.022), and had a longer hospital stay duration (3.7 versus 2.7 days; p = 0.011) than those with ICP. The identified risk factors for respiratory problems were a history of tongue-lip-adhesion (TLA) (p = 0.007) and a preoperative weight of < 8 kg (p = 0.015). Similar risk factors were identified for PICU admission (p = 0.015 and 0.004, respectively).

Conclusions

The possible risk factors for these outcomes were a low preoperative weight and history of TLA. Closer postoperative surveillance should be considered for patients with these risk factors.

Clinical relevance

Identifying risk factors for respiratory complications could provide clinicians better insight into their patients and allows them to provide optimal care for their patients.
Impact of the COVID-19 pandemic on maxillofacial trauma surgery in Germany - implications from the national DRG database
Authors: Meisgeier Axel , Pienkohs Simon , Moosdorf Laura , Neff Andreas
Published: April 2024

Purpose

The COVID-19 pandemic has affected the personal and social lives of millions of people and also impacted the etiological factors of midfacial trauma such as falls, interpersonal violence or traffic accidents. The aim of this study was to analyze the influence of the COVID-19 pandemic on maxillofacial trauma surgery in the German healthcare system.

Methods

Nationwide data regarding the national diagnosis-related-group (DRG) inpatient billing system used in all German hospitals was received from the German Federal Statistical Office. Various trauma-associated procedures of the Operation and Procedure Classification System (OPS), a German modification of the International Classification of Medical Procedures (ICPM), were statistically associated with different epidemiological factors between 2012 and 2021.

Results

A statistically significant decrease (p < 0.05) in surgeries regarding maxillofacial fractures was registered during the years 2020 and 2021. Young male patients had the largest decline in maxillofacial trauma surgeries during this period (p < 0.05). In contrast. elderly patients 80 years and older showed a dramatic increase in the frequency of fractures in both the midface and the mandible (p < 0.05).

Conclusions

During the COVID 19 pandemic there has been a shift in the number, composition and etiology of maxillofacial fracture surgeries. Measures of social distancing and personal risk avoidance had a societal positive effect on the frequency of facial injuries. This stands in contrast to the drastic increase in fractures of elderly people who should be protected primarily by the measures taken. These results can help to understand these influences better in future pandemics.

Trial registration

German Clinical Trials Register No: DRKS00032778.
A Predictor-Corrector Algorithm for Semidefinite Programming that Uses the Factor Width Cone
Authors: Kirschner Felix , Klerk Etienne de
Published: April 2024

We propose an interior point method (IPM) for solving semidefinite programming problems (SDPs). The standard interior point algorithms used to solve SDPs work in the space of positive semidefinite matrices. Contrary to that the proposed algorithm works in the cone of matrices of constant factor width. We prove global convergence and provide a complexity analysis. Our work is inspired by a series of papers by Ahmadi, Dash, Majumdar and Hall, and builds upon a recent preprint by Roig-Solvas and Sznaier [arXiv:2202.12374, 2022].
The geometry of the vergence-accommodation conflict in mixed reality systems
Authors: Wang Xiaoye Michael , Southwick Daniel , Robinson Ian , Nitsche Michael , Resch Gabby , Mazalek Ali , Welsh Timothy N.
Published: April 2024

Mixed reality technologies, such as virtual (VR) and augmented (AR) reality, present promising opportunities to advance education and professional training due to their adaptability to diverse contexts. Distortions in the perceived distance in such mediated conditions, however, are well documented and have imposed nontrivial challenges that complicate and limit transferring task performance in a virtual setting to the unmediated reality (UR). One potential source of the distance distortion is the vergence-accommodation conflict—the discrepancy between the depth specified by the eyes’ accommodative state and the angle at which the eyes converge to fixate on a target. The present study involved the use of a manual pointing task in UR, VR, and AR to quantify the magnitude of the potential depth distortion in each modality. Conceptualizing the effect of vergence-accommodation offset as a constant offset to the vergence angle, a model was developed based on the stereoscopic viewing geometry. Different versions of the model were used to fit and predict the behavioral data for all modalities. Results confirmed the validity of the conceptualization of vergence-accommodation as a device-specific vergence offset, which predicted up to 66% of the variance in the data. The fitted parameters indicate that, due to the vergence-accommodation conflict, participants’ vergence angle was driven outwards by approximately 0.2°, which disrupted the stereoscopic viewing geometry and produced distance distortion in VR and AR. The implications of this finding are discussed in the context of developing virtual environments that minimize the effect of depth distortion.
ERT-based experimental integrated approach for soil hydrological characterization in rainfall-induced shallow landslides prone areas
Authors: Vivaldi Valerio , Torrese Patrizio , Bordoni Massimiliano , Viglietti Filippo , Meisina Claudia
Published: April 2024

Shallow landslides triggered by heavy rainfalls are slope instabilities, developed in the most superficial eluvial layers, involving the first 2 m from the ground level. A crucial predisposing factor in shallow landslides occurrence is the soil water content, generally measured trough sensors installed in the first soil layers. However, despite being a very precise approach, this monitoring technique provides for a site-specific dataset. An integrated method to extend the hydrological characterization from site-specific to slope scale is presented, combining geotechnical analyses, field data monitoring, and geophysical investigations, in two experimental test sites located on Italian Apennines. Ten Electrical Resistivity Tomographies (ERT) of the first soil horizons were performed through different array geometries (2D-3D-Time-Lapse), calibrated and interpreted basing on stratigraphic logs, trenches, and monitored soil water content field data. The test sites colluvial covers composition was analyzed and compared to resistivity values to build conceptual hydrogeological models of the deep-water circulation. In addition, two time-lapse (4D) ERT surveys were performed in both test sites simulating very intense precipitations, to determine the resistivity variations at different soil drainage conditions, thus estimating the average bulk permeability. Bulk permeability can be also a useful input parameter for slope stability models, widely employed in engineering practices. This integrated method proved to be very useful for the hydrogeological characterization of the subsoil at slope scale, where it is susceptible to slope instability, improving the knowledge of water circulation, as well as the bulk permeability heterogeneities, which are shallow landslides triggering parameters.
Risk assessment for synthetic GICs: a quantitative framework for asset–liability management
Authors: Alimoradian Behzad , Jakubiak Jeffrey , Loisel Stéphane , Salhi Yahia
Published: April 2024

This study addresses a research gap in quantitative modeling framework and scenario analysis for the risk management of stable value fund wraps, a crucial segment of the U.S. financial market with over USD $400 billion in assets. In this paper, we present an asset–liability model that encompasses an innovative approach to modeling the assets of fixed-income funds coupled with a liability model backed by empirical analysis on a unique data set covering 80% of the stand-alone plan sponsor market, contrasting with models based solely on regular deterministic cash flows and interest rate differences. Our model identifies and analyzes two critical risk scenarios from the insurer’s perspective: inflationary and yield spike. Our approach demonstrates that the tail risk of wraps, used as an economic capital measure, is sensitive to characteristic parameters of the fund, such as the duration, portfolio composition and credit quality of assets. This finding significantly differs from U.S. regulatory approaches like the NAIC’s, which often result in a zero capital requirement. These findings reveal limitations in current actuarial risk and profitability metrics for U.S. insurers and argue that a more sophisticated risk model reproducing the two critical scenarios is necessary.
Response of consumers to wage shocks in the framework of the Portuguese assistance program
Authors: Alves Nuno , Cardoso Fátima , Pereira Manuel Coutinho
Published: April 2024

This paper studies the impact on consumption of the exogenous changes in public wages in Portugal during and after the economic and financial assistance program (2011-2014), by exploiting the variability in the size of such changes across municipalities. The initial wage cuts triggered a marked reduction of private consumption, while the reinstatements in the later years gave rise to an increase, albeit of a smaller magnitude. The consumption response was larger for employees with relatively lower wages. Households smoothed the impact on consumption of negative income shocks partly by drawing down their deposits. Consumer credit did not play such a role, as households deleveraged as a response to those negative shocks.
Computing equivariant matrices on homogeneous spaces for geometric deep learning and automorphic Lie algebras
Authors: Knibbeler Vincent
Published: April 2024

We develop an elementary method to compute spaces of equivariant maps from a homogeneous spaceG/Hof a Lie groupGto a module of this group. The Lie group is not required to be compact. More generally, we study spaces of invariant sections in homogeneous vector bundles, and take a special interest in the case where the fibres are algebras. These latter cases have a natural global algebra structure. We classify these automorphic algebras for the case where the homogeneous space has compact stabilisers. This work has applications in the theoretical development of geometric deep learning and also in the theory of automorphic Lie algebras.
Business chatbots with deep learning technologies: state-of-the-art, taxonomies, and future research directions
Authors: Zhang Yongxiang , Lau Raymond Y. K. , David Xu Jingjun , Rao Yanghui , Li Yuefeng
Published: April 2024

With the support of advanced hardware and software technology, Artificial Intelligence (AI) techniques, especially the increasing number of deep learning algorithms, have spawned the popularization of online intelligent services and accelerated the contemporary development and applications of chatbot systems. The promise of providing 24/7 uninterrupted business services and minimizing workforce costs has made business chatbots a hot topic due to the impact of the pandemic. It has attracted considerable attention from academic researchers and business practitioners. However, a thorough technical review of advanced chatbot technologies and their relevance and applications to various business domains is rare in the literature. The main contribution of this review article is the critical analysis of various chatbot development approaches and the underlying deep learning computational methods in the context of some business applications. We first conceptualize current business chatbot architectures and illustrate the technical characteristics of two common structures. Next, we explore the mainstream deep learning technologies in chatbot design from the perspective of computational methods and usages. Then, we propose a new framework to classify chatbot construction architectures and differentiate the traditional retrieval-based and generation-based chatbots in terms of the modern pipeline and end-to-end structures. Finally, we highlight future research directions for business chatbots to enable researchers to devote their efforts to the most promising research topics and commercial scenarios and for practitioners to benefit from realizing the trend in business chatbot development and applications.
Prokaryotic communities of the French Polynesian sponge Dactylospongia metachromia display a site-specific and stable diversity during an aquaculture trial
Authors: Maslin Mathilde , Paix Benoît , van der Windt Niels , Ambo-Rappe Rohani , Debitus Cécile , Gaertner-Mazouni Nabila , Ho Raimana , de Voogd Nicole J.
Published: April 2024

Dynamics of microbiomes through time are fundamental regarding survival and resilience of their hosts when facing environmental alterations. As for marine species with commercial applications, such as marine sponges, assessing the temporal change of prokaryotic communities allows us to better consider the adaptation of sponges to aquaculture designs. The present study aims to investigate the factors shaping the microbiome of the sponge Dactylospongia metachromia, in a context of aquaculture development in French Polynesia, Rangiroa, Tuamotu archipelago. A temporal approach targeting explants collected during farming trials revealed a relative high stability of the prokaryotic diversity, meanwhile a complementary biogeographical study confirmed a spatial specificity amongst samples at different longitudinal scales. Results from this additional spatial analysis confirmed that differences in prokaryotic communities might first be explained by environmental changes (mainly temperature and salinity), while no significant effect of the host phylogeny was observed. The core community of D. metachromia is thus characterized by a high spatiotemporal constancy, which is a good prospect for the sustainable exploitation of this species towards drug development. Indeed, a microbiome stability across locations and throughout the farming process, as evidenced by our results, should go against a negative influence of sponge translocation during in situ aquaculture.
A Method to Dampen Acoustic Waves in Compressible Reactive Flow Simulations
Authors: Eigemann Jonas , Beck Christian , Kempf Andreas
Published: April 2024

A novel technique is presented to improve the initialization of compressible combustion LES, DNS or URANS by numerically turning the flame into a damper to quickly remove (artificial) pressure fluctuations and acoustic energy from the system. This is achieved by modifying the pressure dependency of the heat release rate, effectively modifying the Rayleigh Integral to achieve negative values, so that the acoustic energy is quickly removed from the system. The technique can (a) reduce the cost of simulations (by shortening the initialization), (b) contribute to stabilize the simulation, (c) help to avoid unrealistic thermoacoustic modes and, (d) potentially, be modified to compensate for excessive numerical dissipation of acoustic energy. Examples from LES of a thermoacoustic test case are presented to demonstrate the effective stabilization achieved.
Wildfire effects on the fate of deposited nitrogen in a boreal larch forest
Authors: Liu Weili , Zu Jiaxing , Liu B , Qi Lin , Huang Wei , Fang Yunting , Yang Jian
Published: April 2024

The effects of nitrogen (N) deposition on forests largely depend on the ecosystem N status and the fates of deposited N. Boreal forests are typically N-limited ecosystems and are considered to be more efficient in retaining deposited N relative to temperate and tropical forests. As a primary disturbance in boreal forests, wildfires may alleviate N limitation in the burned ecosystem and increase mineralization, resulting in the altered outcomes of the N deposition. In order to explore the effects of a severe wildfire on the retention of deposited N, we investigated the fates of newly deposited N in burned and unburned boreal larch forests by applying 15NH4NO3 tracers to the forest floors. Results showed that total ecosystem retention for the deposited N was 60% in the forest recovering from a severe wildfire burned five years ago, significantly lower than in the unburned mature forest (89%). The difference was mainly attributed to the substantially lower retention in vegetation (8.3%) in the burned site than in the unburned forest (32.4%), as tracer recoveries in soil were similar (51.2 and 56.6%, respectively). Although most 15N tracer was immobilized in organic soil in both burned and unburned forests (33 and 47%, respectively), a noticeably higher amount of 15N was found in mineral soil in the burned forest (19%) than in the unburned forest (10%), suggesting mineral soil as a significant sink for N deposition in the burned forest. A higher total 15N retention in the unburned forest implies that more new N input may stimulate C sequestration and promote the productivity of the Eurasian boreal forest under the background of atmospheric N deposition. However, a considerable amount of deposited N may be lost from the disturbed boreal larch forest ecosystem after a severe wildfire.
Assessing the Utility of Strontium Isotopes in Fossil Dental Calculus
Authors: Dosseto Anthony , Dux Florian , Eisenhofer Raphael , Weyrich Laura
Published: April 2024

Strontium (Sr) isotopes measured in fossil remains have been a useful tool to assess the geographical origin and even migrations of humans and other animals. In particular, dental enamel generally represents the ideal material, as it is dense and less prone to diagenetic replacement of Sr post-burial. However, fossil teeth can often be precious artefacts and difficult to access for destructive analysis. Here, we assess whether measuring Sr isotopes in fossil dental calculus could be used at least as a rangefinder to determine the geographical origin of an individual. We measured trace element concentrations in modern calculus (from a local dental practice), and trace element concentrations and 87Sr/86Sr ratios in human fossil calculus, dentine, and enamel from specimens collected in York, UK. Comparing trace element concentrations between modern and fossil calculus show that metals present in fossil calculus are mostly acquired post-burial, including Sr. The relationship between 87Sr/86Sr and Rb/Sr ratios in fossil calculus, dentine, and enamel suggests that the diagenetic end member would have a 87Sr/86Sr ratio consistent with the one modelled for the York region, but a low Rb/Sr. Without calculus data, dentine and enamel data would have probably suggested a lower 87Sr/86Sr ratio for a diagenetic end member, expecting high Rb/Sr values. Thus, while Sr isotopes in fossil calculus may not be useful to identify the geographical origin of an individual, they may be useful in constraining the composition of the diagenetic end member. Combining Sr isotopes in fossil dental calculus and enamel could be a more robust approach to identify geographical origin than using enamel alone.
U.S. Industrial Transformation and the “How” of 21st Century Industrial Strategy
Authors: Reynolds Elisabeth B.
Published: April 2024

The U.S. policy paradigm has shifted in the first years of the Biden Administration toward a more robust industrial strategy. Over the next decade, trillions of public and private-sector dollars will be invested in technologies and industries deemed critical to national and economic security. This sets the U.S. on a new trajectory, one that accelerates the development and growth of innovative technologies and key industries while also attempting to rebuild U.S. manufacturing capabilities and the middle class more broadly. This shift in U.S. policy is generating significant debate about the merits of industrial policies and their efficacy. This paper outlines the promises and pitfalls of industrial strategy and the key provisions in the three pieces of recent legislation including “guardrails” and “conditionalities” that are meant to put the country on a path toward successful implementation. While there has been significant focus on the “what” of the Biden industrial strategy, less attention has been paid to the “how.” This paper reviews the criteria by which to judge the how, the key provisions of the new legislation, and broader challenges and limitations to meeting all of the Biden Administration industrial strategy objectives.
ROV-Based Autonomous Maneuvering for Ship Hull Inspection with Coverage Monitoring
Authors: Cardaillac Alexandre , Skjetne Roger , Ludvigsen Martin
Published: April 2024

Hull inspection is an important task to ensure sustainability of ships. To overcome the challenges of hull structure inspection in an underwater environment in an efficient way, an autonomous system for hull inspection has to be developed. In this paper, a new approach to underwater ship hull inspection is proposed. It aims at developing the basis for an end-to-end autonomous solution. The real-time aspect is an important part of this work, as it allows the operators and inspectors to receive feedback about the inspection as it happens. A reference mission plan is generated and adapted online based on the inspection findings. This is done through the processing of a multibeam forward looking sonar to estimate the pose of the hull relative to the drone. An inspection map is incrementally built in a novel way, incorporating uncertainty estimates to better represent the inspection state, quality, and observation confidence. The proposed methods are experimentally tested in real-time on real ships and demonstrate the applicability to quickly understand what has been done during the inspection.