Specific Choice Research Articles

Neural network Gaussian processes as efficient models of potential energy surfaces for polyatomic molecules

Kernel models of potential energy surfaces (PESs) for polyatomic molecules are often restricted by a specific choice of the kernel function. This can be avoided by optimizing the complexity of the kernel function. For regression problems with very expensive data, the functional form of the model kernels can be optimized in the Gaussian process (GP) setting through compositional function search guided by the Bayesian information criterion. However, the compositional kernel search is computationally demanding and relies on greedy strategies, which may yield sub-optimal kernels. An alternative strategy of increasing complexity of GP kernels treats a GP as a Bayesian neural network (NN) with a variable number of hidden layers, which yields NNGP models. Here, we present a direct comparison of GP models with composite kernels and NNGP models for applications aiming at the construction of global PES for polyatomic molecules. We show that NNGP models of PES can be trained much more efficiently and yield better generalization accuracy without relying on any specific form of the kernel function. We illustrate that NNGP models trained by distributions of energy points at low energies produce accurate predictions of PES at high energies. We also illustrate that NNGP models can extrapolate in the input variable space by building the free energy surface of the Heisenberg model trained in the paramagnetic phase and validated in the ferromagnetic phase. By construction, composite kernels yield more accurate models than kernels with a fixed functional form. Therefore, by illustrating that NNGP models outperform GP models with composite kernels, our work suggests that NNGP models should be a preferred choice of kernel models for PES.

ANALYZING BANKS’ PERFORMANCE DURING THE RECENT BREAKDOWNS. WHAT WERE THE MAIN DRIVERS?

We observe the main efficiency drivers of European Banking Groups after the burst of the Global Financial Crisis. This analysis is a live issue within the studies in the field of intermediation. The observed period (2010–2021) is emblematic of the complexity of the financial market in the last two decades. The efficiency levels derive from a stochastic frontier approach; a k-means cluster analysis distinguishes the units into three homogeneous groups, so that the main determinants of the higher level of efficiency can be identified. They are linked to a particular business model, specific managerial choices, costs rationalization and liquidity optimization.

The universal one-loop effective action with gravity

We complete the so-called Universal One-Loop Effective Action (UOLEA) with effects of gravity and provide a systematic approach to incorporate higher dimensional operators in curved spacetime. The functional determinant stemming from the path integral is computed using the Covariant Derivative Expansion (CDE), in a momentum representation that does not rely on a specific choice of coordinate to be defined, as it often is. This efficient approach manifests an interesting novelty as it allows to integrate out chiral fermions in curved spacetime in a direct manner leading to new operators involving the curvature, and provides a new alternative to the use of Feynman diagrams in that regard. The method presented would very well fit in a code that performs CDE, offering the possibility to integrate out at one-loop fields on a curved spacetime background, including spin-2 fields, like the graviton. Eventually these results should provide an interesting way to study low energy effects of UV completions of gravity.

Soliton solutions to a wave equation using the (ϕ'/ϕ)– expansion method

This article aims to explore and examine general soliton solutions within the context of the generalized Benjamin-Bona-Mahony equation. This equation is a significant mathematical tool employed in the study of wave dynamics in ocean physics. In this paper, we investigate and generate new propagating soliton solutions for the above-mentioned equation using the (ϕ′/ϕ) − expansion method, an elegant mathematical approach. Rational, trigonometric, and hyperbolic functions are used to express these solutions. In order to provide a visual comprehension of the complex physical phenomena regulating the system, we additionally demonstrate graphics in two and three dimensions. The study explores a range of parameter configurations that yield distinct soliton solutions. By visually depicting these solutions based on specific parameter choices, a deeper comprehension of the system's complex behavior is achieved. The article sheds light on novel findings concerning soliton solutions for the mentioned equation, unveiling previously unnoticed aspects of this captivating mathematical problem.

Renormalon structure in Bjorken sum rule

Leading-twist Bjorken polarised sum rule (BSR) Γ‾1p−n(Q2) is evaluated using its known renormalon structure. In addition, we add OPE terms with the dimension D=2,4, and fit this to experimental data for inelastic BSR in specific intervals of momenta, Q2≥Qmin2, where Qmin2≈(1.7±0.3)GeV2. Reasonable values of the pQCD coupling can be extracted only for specific choices of Qmin2, but have in general, for other choices of Qmin2, very large uncertainties and thus cannot be extracted in practice. On the other hand, if we fix the pQCD coupling to the known world average values, the D=2 and D=4 OPE terms can be determined within reasonable uncertainties dominated by the experimental uncertainties of the data.

Pediatric Residency Graduates’ Characteristics, Career Choice, and Satisfaction by Race and Ethnicity, 2011–2022

ObjectiveLearning more about resident characteristics, career choices, job search experiences, and satisfaction for different racial and ethnic backgrounds can inform needs and approaches to diversifying the physician workforce. MethodsWe analyzed survey data collected from national random samples of pediatric residents graduating from 2011 to 2022. We used chi-square linear association to examine trends in reported race and ethnicity and multivariable logistic regression to estimate associations of race and ethnicity with graduates’ characteristics including debt, career choice, job search experience, and satisfaction with specialty choice and report predicted percentage values (PV). ResultsAdjusted response rate was 53.7% (6392/11,900); 59.7% of respondents identified as white, 20.6% Asian, 10.5% Hispanic/Latino/Spanish, 5.6% Black/African American, and 3.6% Other. These percentages were unchanged across years.Black graduates were more likely than white graduates to identify as female (PV = 81.7 [95% CI = 77.7–85.8] and 73.4 [95% CI = 72.0–74.9], P < .00) and report educational debt >$200,000 (PV = 63.1 [95% CI = 57.2–68.9] and 51.2 [95% CI = 49.3–53.0], P < .00). Black and Hispanic graduates were least likely to be entering subspecialty fellowships. Black, Asian, and Other graduates were more likely than white residents to report job search difficulty. Among residents starting full-time general pediatrics positions, half or more of all race and ethnicity groups reported starting salaries of >$175,000 without significant differences. Nearly all would choose pediatrics again. ConclusionsFew strides have been made over the past decade in diversifying pediatrics. Trainees from minoritized racial and ethnic backgrounds may require support via educational debt relief, mentoring, and social support to overcome barriers and ensure their success.

New regional industrial policy and environmental problems

Aim. The need to accelerate the transition to "green" and digital technologies leads to a more active participation of the state in the economy, including through an active industrial policy. In this regard, the main attention should be paid to the development and use of modern methodological approaches to the formation of a new regional industrial policy, taking into account the environmental aspect.Discussion. One of the main sources of pollutant emissions is industrial production. The article analyses the level of emissions of pollutants from industrial enterprises into the atmosphere in Russia as a whole, as well as for the regions that are leading in the growth of emissions into the atmosphere of industrial enterprises and in the growth in the number of polluting enterprises. Based on the analysis, it is concluded that in many regions of Russia industrial policy is carried out inefficiently. The growth of industrial production occurs extensively by increasing the number of enterprises or industries without taking into account environmental consequences and without the use of modern technologies that reduce the negative impact on the environment. An analysis of methodological approaches to the definition of the "new" industrial policy has been carried out and its general principles have been identified.Conclusion. To date, there is no clear definition of the "new" industrial policy, however, in modern scientific literature there are various methodological approaches that differ from the "old" type of industrial policy. The approaches discussed above differ in the emphasis either on the choice of specialisation – what to produce – or on the process by which prioritization and implementation occurs – how to produce.

Emerging Trends in Frontline Treatment for Acute Myeloid Leukemia (AML): A Survey of NCI-Designated Cancer Centers

Introduction: For the past several decades the standard of care treatment for frontline therapy for acute myeloid leukemia (AML) in individuals that are eligible for intensive induction therapy has been 7 + 3 (7 days of cytarabine (Ara-C) + 3 days of danuorubicin). Older individuals with AML and those that are ineligible for intensive induction tend to be a more difficult population to treat. Since 2018, venetoclax + hypomethylating agents (HMA) (azacitidine or decitabine) has been considered the standard of care frontline treatment for AML in those who are induction ineligible. Over the past decade there have been significant improvements in genetic and molecular testing that have greatly impacted the development of new frontline treatment therapies for individuals with acute myeloid leukemia (AML) with promising treatment outcomes. Methods: In an effort to quantify the impact that these evolving therapies have had on influencing leukemia treatment practices, a questionnaire was sent to every director/chair of Leukemia at each National Cancer Institute (NCI) designated center. Our two-question questionnaire centered around determining the preferred AML treatment for both patients who are not on clinical trials that are eligible and those that are ineligible for intensive induction therapy. Questions were created based on the 2019 NCCN clinical practice guidelines for AML. The survey was limited to 2 questions so as to elicit higher response rate to the questionnaire. Question #1: What is the preferred induction regimen backbone used at your center - In patients eligible for intense chemo, off-study? 7+3FLAG-IDACLAG-IDAVenetoclax w/ 5-azacytidine or decitabineOther Question #2: What is the preferred induction regimen backbone at your center - In patients who are ineligible for intensive chemo, off-study, and having actionable mutations (IDH or FLT3)? Venetoclax + Hypomethylating agentTargeted agent against IDH or FLT3 withoutvenetoclax +/- hypomethylating agentTargeted agent against IDH or FLT3 withvenetoclax +/- hypomethylating agentOther Results: From our study, we received 31/63 (49.2%) responses and saw that for the intensive induction 90.3% (28/31) respondents selected 7 +3 as the preferred treatment with 3.2% (1/31) choosing FLAG-IDA, with the remaining 6.5% (2/31) choosing “other” ((7 +3) w/ FLT3 inhibitor). Comparatively, for the intensive induction ineligible treatment, 61.3% (19/31) respondents preferred venetoclax + HMAs with 38.7% (12/31) preferring targeted agent w/ venetoclax +/- HMA. Of note, four respondents selected venetoclax + HMA as the preferred treatment, but also preferred aza-ivosidenib for IDH1 mutant AML. Conclusion: Preliminary findings from our survey suggest that results from genetic molecular testing may have a greater influence on the evolution in treatment for the intensive induction ineligible population. As more data comes out regarding combining targeted therapy with more broad-based treatments, clarity will emerge on the most appropriate standard-of-care approach. Additionally, improved turnaround time of testing methodology will likely modify treatment approaches. Our next steps include repeat outreach to obtain 100% response rate and sending a follow-up questionnaire to understand the rational for each specific treatment choice.

Impact of a Preclinical Medical Student Anesthesiology Elective on the Attitudes and Perceptions of Medical Students Regarding Anesthesiology.

First- and second-year medical students typically have limited exposure to the field of anesthesiology, yet recent match data shows growing interest in the specialty. Early, structured exposure to anesthesiology in the form of a preclinical elective may allow medical students to make more informed decisions on their specialty of choice. The anesthesiology preclinical elective, BIOL 6704: "Anesthesia: Much More than Putting you to Sleep", is a one-credit course taught at The Warren Alpert Medical School of Brown University. A survey consisting of fifteen questions assessing changes in attitudes, perceptions, and interest in anesthesiology was distributed to first- and second-year medical students before and after course participation. The results were analyzed using the Wilcoxon's signed-rank test for paired samples. The biggest impact of the preclinical elective was observed in the students' subjective understanding of key aspects of the practice of anesthesiology. Statistically significant improvement was seen in the understanding of airway management, anesthetic pharmacology, basics of ultrasound, vascular access, anesthesiology subspecialties, and an understanding of anesthesiology residency. Overall, results were limited by our small sample size. Our elective allows medical students to explore anesthesiology early in their medical school career. After taking this course, students noted more familiarity with various topics in anesthesiology. Peer institutions lacking a similar course may consider using our experience to increase interest about the specialty of anesthesiology for future students.

On Accelerated Coordinate Descent Methods for Searching Equilibria in Two-Stage Transportation Equilibrium Traffic Flow Distribution Model

The search for equilibrium in a two-stage traffic flow model reduces to the solution of a special nonsmooth convex optimization problem with two groups of different variables. For numerical solution of this problem, the paper proposes to use the accelerated block-coordinate Nesterov-Stich method with a special choice of block probabilities at each iteration. Theoretical estimates of the complexity of this approach can markedly improve the estimates of previously used approaches. However, in the general case they do not guarantee faster convergence. Numerical experiments with the proposed algorithms are carried out in the paper.

On the Boundary Behavior of Mass-Minimizing Integral Currents

Let Σ \Sigma be a smooth Riemannian manifold, Γ ⊂ Σ \Gamma \subset \Sigma a smooth closed oriented submanifold of codimension higher than 2 2 and T T an integral area-minimizing current in Σ \Sigma which bounds Γ \Gamma . We prove that the set of regular points of T T at the boundary is dense in Γ \Gamma . Prior to our theorem the existence of any regular point was not known, except for some special choice of Σ \Sigma and Γ \Gamma . As a corollary of our theorem we answer to a question in Almgren’s Almgren’s big regularity paper from 2000 showing that, if Γ \Gamma is connected, then T T has at least one point p p of multiplicity 1 2 \frac {1}{2} , namely there is a neighborhood of the point p p where T T is a classical submanifold with boundary Γ \Gamma ; we generalize Almgren’s connectivity theorem showing that the support of T T is always connected if Γ \Gamma is connected; we conclude a structural result on T T when Γ \Gamma consists of more than one connected component, generalizing a previous theorem proved by Hardt and Simon in 1979 when Σ = R m + 1 \Sigma = \mathbb R^{m+1} and T T is m m -dimensional.

Halo-independent bounds on Inelastic Dark Matter

We discuss halo-independent constraints on the Inelastic Dark Matter (IDM) scenario, in which a Weakly Interaction Massive Particle (WIMP) state χ with mass m χ interacts with nuclear targets by upscattering to a heavier state χ′ with mass m χ + δ.In order to do so we adopt the single-stream method, that exploits the complementarity of Direct Detection (DD) and Capture in the Sun to extend the experimental sensitivity to the full range of incoming WIMP speeds.We show that a non-vanishing mass splitting δ modifies such range, and that for particular combinations of m χ and δ the complementarity between the two detection techniques required by the method is lost. In such cases a specific choice of the WIMP speed distribution in our Galaxy is required to obtain a constraint on the WIMP-nucleus cross section or coupling. Specifically, assuming for the escape velocity in our Galaxy u esc the reference value u esc ref = 560 km/s a halo-independent bound is possible when δ ≲ 510 keV for a Spin-Independent interaction and when δ ≲ 245 keV for a Spin-Dependent interaction (with the Spin-Independent value slightly reduced to δ ≲ 490 keV when u esc > u esc ref). In the low WIMP mass regime the bound from capture in the Sun is always more constraining than that for DD and is sufficient alone to provide a halo-independent constraint, while for large WIMP masses the halo-independent bound is given by a combination of capture in the Sun and DD. In this latter case the reduction in sensitivity due to the mass splitting δ is more pronounced for DD than for capture, and capture plays a more important role to determine the halo-independent bound compared to the elastic case. In particular we find that, for u esc = u esc ref, unless the mass of the target used in DD is larger than about four times that of the target driving capture in the Sun, DD does not play any role in the determination of the maximal value of δ for which a halo-independent bound is possible. We also discuss the issue of thermalization of IDM within the Sun and show that its impact on our results is mild.

Characterizing phonemic fluency by transfer learning with deep language models.

Though phonemic fluency tasks are traditionally indexed by the number of correct responses, the underlying disorder may shape the specific choice of words-both correct and erroneous. We report the first comprehensive qualitative analysis of incorrect and correct words generated on the phonemic ('S') fluency test, in a large sample of patients (n = 239) with focal, unilateral frontal or posterior lesions and healthy controls (n = 136). We conducted detailed qualitative analyses of the single words generated in the phonemic fluency task using categorical descriptions for different types of errors, low-frequency words and clustering/switching. We further analysed patients' and healthy controls' entire sequences of words by employing stochastic block modelling of Generative Pretrained Transformer 3-based deep language representations. We conducted predictive modelling to investigate whether deep language representations of word sequences improved the accuracy of detecting the presence of frontal lesions using the phonemic fluency test. Our qualitative analyses of the single words generated revealed several novel findings. For the different types of errors analysed, we found a non-lateralized frontal effect for profanities, left frontal effects for proper nouns and permutations and a left posterior effect for perseverations. For correct words, we found a left frontal effect for low-frequency words. Our novel large language model-based approach found five distinct communities whose varied word selection patterns reflected characteristic demographic and clinical features. Predictive modelling showed that a model based on Generative Pretrained Transformer 3-derived word sequence representations predicted the presence of frontal lesions with greater fidelity than models of native features. Our study reveals a characteristic pattern of phonemic fluency responses produced by patients with frontal lesions. These findings demonstrate the significant inferential and diagnostic value of characterizing qualitative features of phonemic fluency performance with large language models and stochastic block modelling.

Factors Influencing Medical Students' Pursuit of Urology: Results From the AUA Census (2019-2021).

Growing interest in urology among medical students highlights the need to understand factors influencing their specialty choice in today's context. We also investigate COVID-19's impact on these factors and any disparities among female and underrepresented in medicine (URiM) students. From 2019 to 2021, the AUA Annual Census survey included medical student-focused questions on demographics, career interests, and decision factors. Responses were analyzed. One hundred ninety-two medical students participated. Thirty-six (24%) identified as female and 19 (13%) as URiM. Common reasons students would choose urology included surgical procedures (93%) and "good lifestyle" among surgical careers (85%), with no differences across gender or URiM status. Compared to pre-COVID (2019), during COVID (2020-2021), a greater proportion of students cited cutting-edge technology (90.1% vs 73.1%, P = .008) and surgical procedures (98.6% vs 87.2%, P = .008) as reasons to choose urology. Reasons for not choosing urology included competitiveness (48%) and poor lifestyle (26%). Female and URiM students expressed concern related to the combined "male dominated/gender discrimination/lack of diversity" aspect (female 33% vs male 3%, P < .001; URiM 25% vs non-URiM 7%, P = .04). The AUA Census survey highlights factors influencing medical students' decisions regarding urology. Interest in procedural and technological aspects grew during COVID. Students expressed concern over the field's competitiveness and poor lifestyle, while also acknowledging that urology offers a favorable lifestyle compared to other surgical careers. Female and URiM students expressed ongoing concerns over the combined aspect of gender discrimination and/or the lack of existing diversity in the field.

Surfaces of 20th century facades: reflections 1 on their archaeological awareness

The archaeological approach to the study of elevations is applied here to 20th-century architecture. In particular, post-World War II facades are examined through several case studies. This research uses the method of the archaeology of architecture: the meticulous attention to materials, workmanship, and technological devices, the examination of the socio-economic context, and the analysis of the motivations behind specific choices. These elements contribute to discovering the history of an artefact in a given period of time as completely as possible. The archaeology of architecture has been widely experimented on historical buildings since the 1970s; very rare has been the application to the study of contemporary buildings. The authors, on the basis of the research already started in 2018, at this stage of the study seek to further develop the topic under investigation, also with comparisons on a broader national and international scale. The architectural surfaces of the second half of the 20th century are analyzed here by studying individual components on the facades: the colour and texture of the plaster, any tile, wood, or stone coverings, or the exposed concrete work. The final aim is to develop an overall method of investigation that considers the specificity of the period examined and the possible adaptation of analysis tools that can help in the archaeological study of these contemporary architectures.

Arctic curves of the four-vertex model

We consider the four-vertex model with a special choice of fixed boundary conditions giving rise to limit shape phenomena. More generally, the considered boundary conditions relate vertex models to scalar products of off-shell Bethe states, boxed plane partitions, and fishnet diagrams in quantum field theory. In the scaling limit, the model exhibits the emergence of an arctic curve separating a central disordered region from six frozen ‘corners’ of ferroelectric or anti-ferroelectric type. We determine the analytic expression of the interface by means of the Tangent Method. We supplement this heuristic method with an alternative, rigorous derivation of the arctic curve. This is based on the exact evaluation of suitable correlation functions, devised to detect spatial transition from order to disorder, in terms of the partition function of some discrete log-gas associated to the orthogonalizing measure of the Hahn polynomials. As a by-product, we also deduce that the arctic curve’s fluctuations are governed by the Tracy–Widom distribution.

Outcomes of rural generalist internship training in Victoria, Australia.

Victoria, Australia commenced its first Rural Community Internship Training program in 2012 to support the development of rural generalist (RG) doctors. These general practitioners have additional skills to work at a broad scope to deliver the range of primary care and additional specialist services that communities need. Unlike most internships, which are wholly hospital-based and delivered mostly within larger metropolitan and regional centres, this RG internship training model involves completing general practice experience in smaller rural communities working with RGs and visiting specialists. This study aimed to explore the characteristics and satisfaction of doctors who participate in RG internship training in Victoria and their workforce outcomes. Between October and November 2021, a retrospective 10-minute anonymous survey invitation was sent to all contactable interns (n=222) who had completed/were completing the RG internship training (2012-2021). The survey was co-designed with RG internship managers and other stakeholders of a statewide evaluation advisory group, informed by the latest evidence regarding RG medicine and rural training predictors, and outcomes of interest. Participants completed the survey using Microsoft Forms, with three invitations circulated to an up-to-date email address maintained by the internship program. Collected data were analysed descriptively, by subgroup, to explore training pathway outcomes by region, training stage and specialty choice. Workforce distribution outcomes were defined in line with objectives of the program and predetermined indicators of RG scope. Results were compared with the benchmarks of rural workforce training outcomes in Australia using recent research. There were 59 participants (27% response rate); 81% were in postgraduate years 3-7. Respondents included 54% male, 17% rurally bonded, 39% of rural origin, 34% having had more than 3 months rural undergraduate training and 48% doing RG training where they previously did undergraduate training. All were satisfied/very satisfied with the RG training and 61% were working in general practice (excluding the prevocational group). Overall, 40% were currently working in the same rural region as their internship (including three who were currently interns), 56% continued to complete some prevocational training in the same region as their RG internship, while 20% had gone on to be currently based in smaller rural communities (Modified Monash Model locations 4-7) and 44% to be working part-time in smaller rural communities. Overall, 42% self-identified as working as an RG and nearly all (97%) met at least one of the key indicators of extended (RG) scope. In all areas the RG internship outcomes were better than the national benchmarks from published evidence about rural training. This study provides evidence from doctors up to 9 years after completing their RG internship. Compared with industry benchmarks, the RG internships attract rurally intentioned and rurally experienced doctors who may be likely to remain in the same rural region as their undergraduate rural medical training and continue their postgraduate training in the same region. They were all satisfied with RG internship training, had high propensity to follow a general practice career and work at broad scope in smaller communities. Importantly, they intended to stay in the region where they trained. This suggests RG internship programs are a positive intervention for promoting an RG workforce.

Study of Settlement Patterns in Farming–Pastoral Zones in Eastern Inner Mongolia Using Planar Quantization and Cluster Analysis

Settlements are comprehensive carriers of the material form expression and social appearance of human activities under specific geographical environmental choices. The analysis and preservation of their forms are important principles and strategies for rural settlement planning and construction. In this study, 28 settlements in the farming–pastoral zones in eastern Inner Mongolia were selected as the research objects. By combining fractal geometry and computer programming, the relationship between the boundary form, spatial structure, and architectural order of the settlements was quantitatively expressed, and quantitative indicators that better summarize the form of the settlements in the farming–pastoral zones in eastern Inner Mongolia were extracted. Then, factor analysis and cluster analysis were conducted using the Statistical Package for the Social Sciences software (SPSS26.0) to obtain the characteristic types of settlement forms. Finally, the classification results were combined with social and humanistic factors and the geographical environment to test the rationality of the results. The results show that (1) five form indicators effectively describe the settlement forms in the research area, among which the shape index, dimension of the public space, and architectural density play a crucial role in the spatial structure factors. (2) In this study, we mainly used a data collection and processing–principal component extraction and systematic clustering-type division method to complete scientific research on settlement form classification. (3) By combining the clustering results with the spatial form features and analysis mainly based on spatial structure factors, the settlement forms in the farming–pastoral zones in eastern Inner Mongolia are described as three typical types: multidirectional expanding settlement, settlement patterns extending at both ends, and centripetal development settlement. Furthermore, the characteristics of the human–land relationship implicit in each type of settlement form are explained, achieving a scientific representation and classification of the settlement forms. The research results provide useful quantitative guidance for rural revitalization, settlement form optimization, and preservation in the farming–pastoral zones in eastern Inner Mongolia

Gauged SU(3)F and loop induced quark and lepton masses

We investigate a local SU(3)F flavour symmetry for its viability in generating the masses for the quarks and charged leptons of the first two families through radiative corrections. Only the third-generation fermions get tree-level masses due to specific choice of the field content and their gauge charges. Unprotected by symmetry, the remaining fermions acquire non-vanishing masses through the quantum corrections induced by the gauge bosons of broken SU(3)F. We show that inter-generational hierarchy between the masses of the first two families arises if the flavour symmetry is broken with an intermediate SU(2) leading to a specific ordering in the masses of the gauge bosons. Based on this scheme, we construct an explicit and predictive model and show its viability in reproducing the realistic charged fermion masses and quark mixing parameters in terms of not-so-hierarchical fundamental couplings. The model leads to the strange quark mass, ms ≈ 16 MeV at MZ, which is ~2.4σ away from its current central value. Large flavour violations are a generic prediction of the scheme which pushes the masses of the new gauge bosons to 103 TeV or higher.

Asymptotic behavior of a system of two coupled queues when the content of one queue is very high

We consider a system of two parallel discrete-time single-server queues, queue 1 and queue 2. The service time of any customer in either queue is equal to 1 time slot. Arrivals during consecutive slots occur independently from slot to slot. However, the arrival streams into both queues are possibly mutually interdependent, i.e., during any slot, the numbers of arrivals in queue 1 and queue 2 need not be statistically independent. Their joint probability generating function (pgf) A(x, y) fully characterizes the queueing model. As a consequence of the possible intra-slot correlation in the arrival process, the numbers of customers present (“system contents”) in queues 1 and 2, at any given slot boundary, are not necessarily independent either. In a previous paper, we have already discussed the mathematical difficulty of computing their steady-state joint pgf U(z_1,z_2); explicit closed-form results can only be obtained for specific choices of A(x, y). In this paper, we therefore look at the problem from an other angle. Specifically, we study the (asymptotic) conditional steady-state behavior of the system under the condition that the content of queue 1 is (temporarily) very high (goes to infinity). For ease of terminology, we refer to the system as the “asymptotic system” in these circumstances. We prove that the asymptotic system is nearly identical to the original (unconditional) system, but with a modified joint arrival pgf A^*(x,y) that can be computed explicitly from A(x, y). This fundamental result allows us to determine the stability condition of queue 2 in the asymptotic system, and explicitly compute the classical queueing performance metrics of queue 2, such as the pgf, the moments and the approximate tail distribution of its system content, when this condition is fulfilled. It also leads to accurate approximative closed-form expressions for the joint tail distribution of the system contents in both queues, in the original (unconditional) system. We extensively illustrate our methodology by means of various specific (popular) choices of A(x, y). In some examples, where an explicit solution for U(z_1,z_2) or for the (approximative) joint tail distribution is known, we retrieve the known results easily. In other cases, new results are found for arrival pgfs A(x, y) for which no explicit results were known until now.