bluuebunny/crossref_metadata_2025_split huggingface dataset:
Linear Quadratic Regulator for Delayed Systems Using the Hamiltonian Approach and Exact Closed-Loop Poles for First-Order Systems
Authors: Shaik Junaidvali , Vyasarayani C. P. , Chatterjee Anindya 
Published: April 2023

Abstract
We consider the linear quadratic regulator (LQR) for linear constant-coefficient delay differential equations (DDEs) with multiple delays. The Hamiltonian approach is used instead of an algebraic Riccati partial differential equation. Two coupled DDEs governing the state and control input are derived using the calculus of variations. This coupled system, with infinitely many roots in both left and right half-planes, defines a boundary value problem. Its left half-plane roots are the exact closed-loop poles of the controlled system. These closed-loop poles have not been used to compute the optimal feedback before. Here, the distributed delay kernel that yields exactly those poles is first computed using an eigenfunction expansion. Increasing the number of terms in the truncated expansion yields a highly oscillatory kernel. However, the oscillatory kernel's antiderivative converges to a piecewise smooth function on the delay interval plus a Dirac delta function at zero. Discontinuities in the kernel coincide with discrete delay values in the original DDE. Using this insight, a fitted piecewise polynomial kernel matches the exact closed-loop poles very well. The twofold contribution of the Hamiltonian approach is thus clarity on the form of the feedback kernel as well as the exact closed-loop poles. Subsequently, the fitted piecewise polynomial kernel can be used for a much simpler control calculation. The polynomial coefficients can be fitted by solving a few simultaneous linear equations. Two detailed numerical examples of the LQR for DDEs, one with two delays and one with three delays, show excellent results.
Optimization of Piecewise-Focusing Concentrating Solar Thermal Collectors Using the System Advisor Model, and Comparison to a Central Receiver System
Authors: Bisset David K 
Published: April 2023

Abstract
Heat collection performance simulations using the system advisor model (SAM) with typical meteorological year weather data from four geographic locations are used to investigate (a) the optimum overall tilt of piecewise-focusing (PWF) collectors, and (b) PWF collector performance in comparison to the SAM default central receiver system. Results show that the overall tilt angle is not critical, but values up to 50 deg are best at non-tropical latitudes, even when output in summer is more valuable than in winter. For tropical latitudes, 40 deg of tilt is sufficient. Increasing PWF collector width relative to height is advantageous. Depending on location, PWF collector performance is 66–90% better than for the SAM default 100 MWe central receiver system, per square meter of reflector or heliostat. Using SAM’s detailed control over system parameters, it is shown that the PWF collector’s superior performance is derived mainly from better geometry (smaller cosine losses), but the near-absence of atmospheric attenuation and the smaller receiver heat losses are also significant.
Acute Mechanical and Skin Temperature Responses to Different Interrepetition Rest Intervals During Full-Squat Exercise
Authors: Baena-Raya Andrés , Díez-Fernández David M. , García-Ramos Amador , Martinez-Tellez Borja , Boullosa Daniel , Soriano-Maldonado Alberto , Rodríguez-Pérez Manuel A. 
Published: April 2023

Purpose: This study aimed to (1) evaluate the acute effects of different interrepetition rest full-squat protocols on countermovement jump (CMJ) height, velocity loss (VL), and skin temperature (Tsk) and (2) determine whether the VL, the changes in Tsk, or the individual strength level is associated with the change in CMJ height. Methods: Sixteen resistance-trained men randomly performed 3 squat protocols at maximal intended velocity with 60% of the 1-repetition maximum (sets × repetitions [interrepetition rest]): traditional (2 × 6 [0 s]), cluster 2 (2 × 6 [30 s every 2 repetitions]), and cluster 1 (1 × 12; [36 s every repetition]), plus a control session. CMJ height was assessed before and 2, 4, and 8 minutes after the protocols. Results: There was a significant main effect of protocol for the VL (F = 20.54, P < .001) and loss in mean power (F = 12.85, P < .001; traditional > cluster 2 > cluster 1). However, we found a comparable reduction of CMJ height after 8 minutes: traditional (−3.4% [4.2%]), cluster 2 (−5.3% [4.9%]), cluster 1 (−5.4% [2.9%]), and control (−4.2% [3.6%]). Overall, mean Tsk acutely decreased after all the protocols. Higher individual strength level (but not VL or the changes in Tsk) was associated with lower CMJ-height loss (P < .05). Conclusions: Although different interrepetition rest full-squat protocols may alter the loss in velocity and power, they result in a similar decrease in Tsk and CMJ height, which could be more influenced by individual strength level than VL or changes in Tsk.
Helicity-modulated remote C-H functionalization
Authors: Yang Na , Shen Chengshuo , Zhang Guoli , Gan Fuwei , Ding Yongle , Crassous Jeanne , Qiu Huibin 
Published: April 2023

Remote C-H functionalization is highly important for the conversion and utilization of arenes, but the conventional routes are comprehensively developed with the assistance of transition metal catalysts or templates. We report a facile metal/template-free electrochemical strategy for remote C-H functionalization in a helical system, where aromatic or aliphatic hydrogen act as a directing group to promote the alkoxylation at the opposite site of the helical skeleton by generating a unique helical “back-biting” environment. Such helicity-modulated C-H functionalization is prevalent for carbo[
n
]helicenes (
n
= 6 to 9, primitive or substituted) and hetero[6]helicenes and also occurs when the aryl hydrogen on the first position is replaced by a methyl group or a phenyl group. Thus, the relatively inert helicene skeleton can be precisely furnished with a rich array of alkoxy pendants with tunable functional moieties. Notably, the selective decoration of a methoxy group on
N
-methylated aza[6]helicene close or distant to the nitrogen atom leads to distinct luminescence variation upon changing the solvents.
Time to Introduce Nerve Density in Cancer Histopathologic Assessment
Authors: Hondermarck Hubert , Jiang Chen Chen 
Published: April 2023

Summary
The density of nerves in the tumor microenvironment is increasingly reported to be associated with worse clinical outcome in various cancers. Therefore, it is time to consider the assessment of nerve density in clinical cancer pathology, and interestingly, the development of artificial intelligence may facilitate this clinical translation.
See related article by Perez-Pacheco et al., p. 2501
Sex Differences in Cardiac Troponin Trajectories Over the Life Course
Authors: de Bakker Marie , Anand Atul , Shipley Martin , Fujisawa Takeshi , Shah Anoop S.V. , Kardys Isabella , Boersma Eric , Brunner Eric J. , Mills Nicholas L. , Kimenai Dorien M. 
Published: April 2023

Background:
Cardiac troponin concentrations are lower in women than men. We examined whether age- and risk factor-related changes in cardiac troponin over the life course differ by sex and if the trajectory of cardiac troponin was informative in respect of cardiovascular outcomes in women and men in the general population.

Methods:
In the Whitehall II cohort, high-sensitivity cardiac troponin I concentrations were measured on 3 occasions over a 15-year period. Using linear mixed-effects models, the sex-specific trajectories of cardiac troponin were evaluated, and the relationship with conventional cardiovascular risk factors determined. Using multistate joint models, the association between sex-specific trajectories of cardiac troponin and a composite outcome of nonfatal myocardial infarction, nonfatal stroke, or cardiovascular death was evaluated.

Results:

In 2142 women and 5151 men (mean, 58±7 and 57±7 years of age, respectively), there were 177 (8.3%) and 520 (10.1%) outcome events, respectively, during a median follow-up of 20.9 (25th to 75th percentile, 15.8–21.3) years. Cardiac troponin concentrations were persistently lower in women than in men (median baseline concentration: 2.4 [25th to 75th percentile, 1.7–3.6] ng/L versus 3.7 [25th to 75th percentile, 2.6–5.8] ng/L, respectively,
P
<0.001), with women exhibiting a relatively larger increase with advancing age as compared with men (
P

interaction

<0.001). Apart from age, a significant and divergent interaction with sex was found for the association between cardiac troponin and body mass index (BMI) (
P

interaction

=0.008) and diabetes (
P

interaction

=0.003). During follow-up, cardiac troponin concentrations were associated to the outcome in both women and men (adjusted hazard ratio per 2-fold difference [95% CI, 1.34 (1.17–1.52) and 1.30 (1.21–1.40), respectively],
P

interaction

=
0.752). The slope of cardiac troponin was significantly associated with the outcome in women, but not in men (adjusted hazard ratio [95% CI, 2.70 (1.01–7.33) and 1.31 (0.62–2.75), respectively],
P

interaction

=
0.250).

Conclusions:
Trajectories of cardiac troponin differ between women and men in the general population, with differing associations to conventional risk factors and cardiovascular outcomes. Our findings highlight the importance of a sex-specific approach when serial cardiac troponin testing is applied for cardiovascular risk prediction.
Paternal Filiation in Muslim-Majority Environments: A Comparative Look at the Interpretive Practice of Positive Islamic Law in Indonesia, Egypt, and Morocco
Authors: Dupret Baudouin , Belkadi Adam , Lindbekk Monika , Yakin Ayang Utriza 
Published: April 2023

Abstract
In most Muslim-majority countries, Islamic normativity underwent a process of “positivization” completely altering the sense which is made of these norms and the ways through which they are obtained. This article aims to deepen our understanding of this phenomenon through a comparative examination of an issue addressed in classical fiqh, partly legislated in modern statutes and codes, sensitive to the progress of scientific evidentiary methods, and largely at judges’ discretion. It proceeds, for each of the three countries under study (Indonesia, Egypt, and Morocco), to describe the situation, starting with the legal system, family law, and the question of paternal filiation (ithbât al-nasab, in Arabic), then paying attention to the “trajectory” of a recent case, from first-instance decisions to final rulings. In conclusion, it focuses on the room that the combination of fiqh principles and contemporary legal sources and thinking opens for creative analogy, radically innovative interpretation, and polycentric tensions between various jurisdictions.
Northward Shifts of the Sahara Desert in Response to Twenty-First-Century Climate Change
Authors: Tian Chuyin , Huang Guohe , Lu Chen , Song Tangnyu , Wu Yinghui , Duan Ruixin 
Published: April 2023

Abstract
The spatial extent of the Sahara (the largest nonpolar desert) has significant impacts on the livelihood of people residing in its surrounding areas. Despite the fact that climate change would foreseeably impact the location and size of the desert, its future responses (i.e., advance or retreat) are rarely explored in previous studies. Here, through the development of an ensemble Bayesian discriminant analysis approach, we use 10 of the latest high-resolution GCM (global climate model) simulations to document robust annual and seasonal responses of the Sahara Desert to twenty-first-century climate change, with the consideration of modeling uncertainties. We find northward shifts of the Sahara/Sahel and eastern expansion of the nondesert zone under both SSP2–4.5 and SSP5–8.5 scenarios, the former more pronounced in the wet season and the latter in the dry season. Countries located near the Mediterranean may thus experience higher risks of drought, while the projected retreat of the Saharan southern boundary will be beneficial to the local water availability of proximal countries.

Significance Statement
Given that sub-Saharan Africa is one of the most vulnerable regions to climate change, the Sahara’s expansion would bring unexpected health risks to billions of people. It is thus vital to understand its robust response to global warming. However, previous studies are merely focused on using a simple precipitation threshold as the definition criterion to estimate the varying size of the Sahara Desert. In addition, significant uncertainty in precipitation projections also limits relevant investigations of the Sahara’s future responses. Here, by developing an ensemble Bayesian discriminant analysis approach, we could provide an objective basis for desert identification under large intermodel uncertainty. Further, we find significant northward shifts of both the Sahara and the Sahel, which may induce higher risks of drought over the northwest of North Africa.
Suicides among adults in Paraguay: An 18-year national exploratory study (2004–2022)
Authors: Torales Julio , Barrios Iván , Melgarejo Osvaldo , Tullo-Gómez Juan Edgar , Díaz Noelia Ruiz , O’Higgins Marcelo , Maggi Carol , Adorno Víctor , Medina Alicia , Villalba-Arias Jorge , González-Urbieta Israel , Caycho-Rodríguez Tomás , Castaldelli-Maia João Mauricio , Ventriglio Antonio 
Published: April 2023

Background: The number of suicides has been increasing worldwide, year after year, becoming the fourth leading cause of death among young people between 15 and 29 years of age. Aim: In this study, we explored the frequency and characteristics of suicides among the adult general population in Paraguay between 2004 and 2022, considering that suicide attempts and suicidal risk/ideation are frequent and relevant issues in the consultation activity, even if epidemiological evidence on the national rates of suicide is scarce. Methods: In this observational, descriptive, and exploratory study, official records of all deaths by suicide were reviewed and information analyzed. In addition, an attempt was made to predict the number of suicides in the next 5 years according to a mathematical modeling. Results: In the 18-year period, 5,527 suicides of adults were recorded. Patients’ mean age was 36.8 ± 17 years old. A 76.77% of them were males, 77.44% were from an urban area and 25.98% from the Greater Asunción and Central Department of Paraguay. The most frequently used method of suicide was intentional self-inflicted injury by hanging, strangulation, or suffocation (all 67.6%). The expected number of national suicides in the following years from 2023 to 2027 will range between 462 and 530. Limitations include the lack of information regarding diagnoses and personal history in the suicide reports as well as the possibility of underreporting of national suicide cases. Conclusion: Our results represent the first large national epidemiological report of suicides in Paraguay and may be of interest for mental health professionals and health authorities in order to reduce the suicide mortality rate within the country.
The Plane Hydrostatic Test as a Means for Selecting Appropriate Failure Criteria in Fibre Composites
Authors: Theocaris Pericles S. 
Published: April 2023

Biaxial tests in anisotropic plates of composite materials do not provide a conclusive evidence for the selection of the appropriate version of the failure tensor polynomial criterion (FTP). On the other hand triaxial tests, which could be decisive, present difficulties and inaccuracies when anisotropic materials should be tested. It was shown in this paper that a simple biaxial hydrostatic test in the transverse isotropic plane of a transversely isotropic material constitutes an accurate technique to decide which version of the criterion is valid. It was proved that the anisotropy along the strong stress axis of the material increases considerably the differences in failure in the transverse isotropic plane between the various criteria and it constitutes a safe test for deciding the validity of the appropriate criterion. Tests in biaxial hydrostatic tension or compression with different composite materials indicated clearly the superiority of the elliptic paraboloid failure surface criterion (EPFS).
Microstructure of Composite Materials Using Small-Angle Neutron Scattering and Contrast Variation: Approaches toward Understanding the Structure of Carbon Black-Elastomer Mixtures
Authors: Hjelm Rex P. , Seeger Philip A. , Wampler Wesley A. 
Published: April 2023

Mixed composites of rubber and carbon black are of fundamental importance to rubber technology, and neutron scattering provides a unique view of structure in these interesting and complex systems. This is due, in part, to the nature of the interaction of the neutron with nuclei, which is a function of the specific nucleus, not on atomic number, per se. This allows neutrons to be used to probe fluctuations in chemical and isotopic composition and density in a manner that is a distinct from x-rays or electrons. This aspect of neutron scattering has been used extensively in the study of multicomponent systems, even when components have elements of similar atomic numbers. The large difference in scattering from some isotopes—hydrogen and deuterium being the most important example—can be used to enhance fluctuations in these systems and thus to probe structures that are not accessible by other methods. We describe the use of small-angle neutron scattering in carbon black, elastomer and carbon black elastomer mixtures using the method of contrast variation. In this approach the sample is suspended in solvents containing different proportions of perdeuterated and protonated molecules. The variation in scattering observed as a function of solvent scattering power gives information on the distribution of components within the sample. Our first experiences using this approach show the potentials of the technique. The use of solvents near the average scattering length density of the carbon black allows observation of non-uniformity in carbon black particles that has not been previously noted. Further, we have established that the shape of the scattering curves in N762 carbon black can be explained as scattering from spherical particles of size and polydispersity measured by electron microscopy. In N121, in which the particle sizes are smaller than N762, contribution to the scatter from the carbon black particle interactions is observable. In gels of solvent extracted carbon black and elastomer we find that the scattering is dominated by carbon black density fluctuations. We find further that the elastomer coats the carbon black particles, at least in N762. There are differences in the association of the carbon blacks in solvent extracted mixtures compared to the carbon blacks suspended in cyclohexane. There may be changes, as well, in the elastomer conformation in the mixtures compared to the polymer alone in cyclohexane. These differences are small in gels containing low concentrations of polyisoprene and carbon black, but are quite profound in a gel containing styrene butadiene rubber with high concentrations of components. Further measurements and modelling of die data will be needed to come to a more satisfactory picture of carbon black morphology and elastomer conformation in the solvent extracted mixtures.
Marine Grade Polyester Resins for Boat Building in the 1990s
Authors: Norwood L.S. , Holton E.C. 
Published: April 2023

Long-term evidence strongly supports the suitability of polyester resins for the construction of marine structures. However, misuse and incorrect selection has resulted in some distrust of their use for the manufacture of large structures. In this paper the issues surrounding the limitations of general purpose resins are discussed and cost-effective alternatives suggested which, if used correctly, can resist blister formation indefinitely. The mechanical performance of these systems is also discussed and compared with vinyl esters, epoxies and toughened resins. Under cold curing conditions isophthalic acid and isophthalic acid-neopentyl glycol based resins are more than adequate for resisting blister formation for, in some systems, in excess of 20 years at ambient temperatures and with laminate properties matching those of cold cured epoxy or vinyl ester systems. Examples are given of the effective combination of different resin systems where the main structural laminate is protected by an environmental barrier providing cost-effective structural composites suitable for all marine structures.
The Effect of Mixer Type and Processing Conditions on the Morphology of Polyamide/Polypropylene Blend
Authors: Vainio Tommi P. , Seppälä Jukka V. 
Published: April 2023

The effect of mixer type and processing conditions on the morphology of immiscible binary polyamide/polypropylene blend was studied. Blends were prepared in seven different mixers operating at various screw speeds. Changing the screw speed altered the shear stress and mixing intensity applied to the melt, and also the viscosity ratio. Average panicle sizes of the dispersed phase (PP) and the particle size distributions were determined for extruded and for subsequently injection moulded blends. The number average particle size level achieved in the melt blending was fairly well transferred to the injection moulded blend although the size distribution was broadened after the injection moulding due to the formation of both small (≍1 μm) and large (>10 μm) particles. The morphology of the skin region was very different from that of the core region in both the extruded and the injection moulded blends. The dispersed phase droplet size was dependent on screw speed to some degree. This dependency was greatest for the single screw extruder. Particle size correlated strongly with shear stress, specific mechanical energy input, and mixing intensity of the mixer. Shear stress, we were led to conclude, is a more important factor in controlling the morphology than the shear-rate-dependent viscosity ratio. Mechanical properties of the blends were poor due to weak adhesion at the interface of the blend components. Additionally, we found that melt blending promoted a better and more homogeneous dispersion in the injection moulded blend.
A Visco-Plastic Analysis of Bonded Joints under Complex Loading
Authors: Chiu W.K. , Jones R. , Chao M. 
Published: April 2023

Adhesively bonded joints are traditionally designed using a single stress/strain curve to describe the mechanical behaviour of the adhesive. This paper addresses the validity of this assumption, given that the properties of film adhesives commonly used in bonded joints (e.g. FM 73) have been shown to demonstrate significant time dependencies both at room and high temperatures. To this end, a series of finite element analysis were conducted where the time dependent properties of the adhesive were modelled using a unified plasticity theory. The findings of this work show that, when performing certification assessments which require statements on the integrity and the durability of adhesively bonded joints subjected to complex load spectra, it may be necessary to consider an analysis which accounts for both time and load history effects. It is also shown that, for monotonic loading under constant loading rates, the peak stress strain response of the adhesive in a double lap joint follows the Glinka hypothesis for the notch stress-strain response of metals. However, it is shown that this approximation may not be valid for complex loading spectra.