Successive Relaxations Research Articles

Blood safety markers in Dutch donors after relaxation of deferral for men who have sex with men: re-emergence of syphilis and HIV pre-exposure prophylaxis use.

Less discriminatory donor selection policies for men who have sex with men (MSM) may impact transfusion safety in terms of higher residual risks for known transfusion-transmitted infections (TTIs), increased vulnerability toward new TTIs that are also transmitted via sex, and HIV infections masked by pre-exposure prophylaxis (PrEP). TTI trends in Dutch donors were studied over a 13-year period (2011-2023), characterized by successive relaxations of MSM deferral criteria. Structured posttest counseling was performed to determine risk factors in TTI-positive donors. PrEP drug levels were measured in 9977 donations from male donors living in urban areas and in 67 donors with active or resolved syphilis. HIV incidence (from 5.8 to 1.5 per 1,000,000 donor years (DY)) and HBV incidence (from 12.4 to 4.5 per 1,000,000 DY) in Dutch donors decreased with less stringent MSM deferral criteria, while syphilis prevalence (from 26.4 to 44.1 per 100,000 new donors) and syphilis incidence (from 18.3 to 46.3 per 1,000,000 DY) increased over time. The proportion of MSM-related syphilis rose from 2% to 32% in new donors and from 12% to 27% in repeat donors. PrEP was detected in 2 of 9977 (0.02%) donations from male donors living in urban areas, and in 1 of 39 (2.6%) male donors with syphilis. To date, phasing out donor deferral for MSM had no significant impact on transfusion safety in the Netherlands. However, rising syphilis rates and (recent) PrEP use in the blood donor population, albeit rare, suggest an influx of donors with higher sexual risk profiles and requires intensified TTI surveillance in donors.

EFFLEURAGE MASSAGE MENGGUNAKAN ESENSIAL OIL SERAI (CYMBOPOGON Sp) DAN TEH SEREH EFEKTIF UNTUK MENURUNKAN NYERI PADA IBU POST PARTUM

The reported prevalence of postpartum morbidity included: bleeding 71.92%, fever 12.18%, hypertension 10.64%, after pain 6.1% and others 0.71%. Pain after childbirth is caused by successive uterine contractions and relaxations that occur continuously. Effleurage massage is a non-pharmacological pain reduction method because touch and pain are stimulated at the same time, the sensation of touch travels to the brain and closes the gate in the brain, thus limiting the amount of pain felt in the brain. Flavonoids, tannins and saponins have the effect of inhibiting the cyclooxygenase enzyme which can suppress the production of prostaglandins (PGE2), thus providing analgesic and anti-inflammatory effects. The purpose of this study was to determine the effectiveness of effleurage massage using lemongrass aromatherapy and lemongrass tea drink (cymbopogon sp) on pain in postpartum mothers. The design of this study was a quasi-experimental with control group, paired T-test, unpaired T-test and Man Whitney test. There was a decrease in pain scores, after being given the intervention, the score decreased by 3 higher than the control group, namely 2. The decrease in anxiety scores in the intervention group was higher than the control group, namely 12.16 and 1.39. The results showed that there was a relationship between effleurage massage with lemongrass essential oil and lemongrass tea drink cymbopogon sp on post partum mother pain (after pain). There is great potential for further collaborative research by midwives to explore clinical applications with large-scale randomized sampling techniques..

Modeling Monophasic Flow of Polymer Solutions in Porous Media: Assessing Relative Impact of Intrinsic Fluid Properties and Pore Microstructure

Polymer solutions are often described as viscoelastic fluids, whose rheological behavior dynamically evolves according to the flow shear rate due to successive contractions and relaxations of inner deformable components. Contrary to shear-thickening and shear-thinning fluids, viscoelastic fluids can undergo an increase in the normal stress-differences even in simple geometries, leading to counterintuitive flow patterns. In this paper, we investigate numerically the monophasic flow of viscoelastic fluids through microfluidic devices. The objective is to qualitatively assess how modification of the rheological properties and the geometry of porous media representative element affect the flow regime at microscale. Deviations from equivalent Newtonian model are analyzed to quantify the contribution of elasticity in the flow. It is demonstrated that depending on the geometry, flow of polymer solution can display anisotropic features and flow resistance at relatively low viscoelastic numbers, which is coherent with previous microscopic experimental and numerical studies. Ensued applications of the formulated microscale model are discussed.

Variations in Black Carbon concentration and sources during COVID-19 lockdown in Delhi

A nationwide lockdown was imposed in India due to COVID-19 pandemic in five phases from 25th March to May 31, 2020. The lockdown restricted major anthropogenic activities, primarily vehicular and industrial, thereby reducing the particulate matter concentration. This work investigates the variation in Black Carbon (BC) concentration and its sources (primarily Fossil Fuel (ff) burning and Biomass Burning (bb)) over Delhi from 18th February to July 31, 2020, covering one month of pre-lockdown phase, all the lockdown phases, and two months of successive lockdown relaxations. The daily average BC concentration varied from 0.22 to 16.92 μg/m3, with a mean value of 3.62 ± 2.93 μg/m3. During Pre-Lockdown (PL, 18th Feb-24th March 2020), Lockdown-1 (L1, 25th March-14th April 2020), Lockdown-2 (L2, 15th April-3rd May 2020), Lockdown-3 (L3, 4th-17th May 2020), Lockdown-4 (L4, 18th-31st May 2020), Unlock-1 (UN1, June 2020), and Unlock-2 (UN2, July 2020) the average BC concentrations were 7.93, 1.73, 2.59, 3.76, 3.26, 2.07, and 2.70 μg/m3, respectively. During the lockdown and unlock phases, BC decreased up to 78% compared to the PL period. The BC source apportionment studies show that fossil fuel burning was the dominant BC source during the entire sampling period. From L1 to UN2 an increasing trend in BCff contribution was observed (except L3) due to the successive relaxations given to anthropogenic activities. BCff contribution dipped briefly during L3 due to the intensive crop residue burning events in neighboring states. CWT analysis showed that local emission sources were the dominant contributors to BC concentration over Delhi.

Optimal trajectories and normal load analysis of hypersonic glide vehicles via convex optimization

Hypersonic trajectory optimization has been intensively investigated through different approaches; however, the normal-load-optimal entry problems were barely studied and reported in the literature. Finding the optimal trajectories with maximum or minimum peak normal load is essential to evaluate the maneuverability and structural strength of the vehicle. In this paper, both the maximum and minimum peak-normal-load entry trajectories are explored using convex optimization. Based on the previous work, the maximum-peak-normal-load entry problem is firstly addressed by a Big-M method and a line-search approach. Through successive relaxations, the nonconvex discrete-event optimal control problem associated with maximum-peak-normal-load entry is transformed into a sequence of mixed-integer convex optimization problems. Then, a line-search technique is introduced to improve the convergence of the proposed method. Additionally, a sequential convex programming method is designed to solve the minimum-peak-normal-load entry problem to comprehensively analyze the normal load during the entry flight. There are efficient solvers that can solve each relaxed convex subproblem with a global optimum if the feasible set of the subproblem is nonempty. The convergence and accuracy of the proposed methodologies are demonstrated by numerical simulations, and the feasibility of the converged solutions is discussed based on an entry-corridor approach.

Downconversion process in Yb3+doped GdAG nanocrystals

The efficient near infrared 2F5/2→2F7/2 downconversion emission of Yb3+ was observed upon excitation of Gd3Al5O12:Yb3+ nanocrystals in UV range. Its integrated intensity was measured as a function of excitation power in the range 1–30mW and compared for a low and high concentration of Yb ions. The model of luminescence dependency on absorbed pump power was applied to investigate the emission mechanism. It was found that the N parameter of that model, interpreted as the order of the process, was dependent on concentration of Yb ions. Moreover, the presence of Yb2+ has been confirmed. The mechanism of energy transfer processes leading to observed Yb3+ emission was discussed in terms of a sequence of successive cross relaxations via a presence of divalent and trivalent Yb ions: Gd3+→Yb2+→ (Yb3+)*.

Using Semidefinite Relaxation to Solve the Day-Ahead Hydro Unit Commitment Problem

In this paper, we present a mixed-integer formulation with nonlinear production functions of the day-ahead hydro unit commitment problem for hydro-dominant power systems. The objective is to minimize unit startup and shutdown costs and maximize water use efficiency in the daily operation of multiple hydro plants. Determination of hourly generation dispatches and unit configurations is subject to reservoir dynamics, power balance, as well as target constraints coupling short-term generation with long-term reservoir operation goals. In addition, ac power flow constraints are considered. An equivalent quadratically-constrained quadratic formulation is approximated by successive convex semidefinite programming relaxations in a branch-and-bound algorithm for optimal solutions. Numerical case studies for several system configurations are presented to illustrate the effectiveness of the relaxation algorithm.

Convex underestimating relaxation techniques for nonconvex polynomial programming problems: computational overview

AbstractThis paper introduces constructing convex-relaxed programs for nonconvex optimization problems. Branch-and-bound algorithms are convex-relaxation-based techniques. The convex envelopes are important, as they represent the uniformly best convex underestimators for nonconvex polynomials over some region. The reformulation-linearization technique (RLT) generates linear programming (LP) relaxations of a quadratic problem. RLT operates in two steps: a reformulation step and a linearization (or convexification) step. In the reformulation phase, the constraint and bound inequalities are replaced by new numerous pairwise products of the constraints. In the linearization phase, each distinct quadratic term is replaced by a single new RLT variable. This RLT process produces an LP relaxation. The LP-RLT yieds a lower bound on the global minimum. LMI formulations (linear matrix inequalities) have been proposed to treat efficiently with nonconvex sets. An LMI is equivalent to a system of polynomial inequalities. A semialgebraic convex set describes the system. The feasible sets are spectrahedra with curved faces, contrary to the LP case with polyhedra. Successive LMI relaxations of increasing size yield the global optimum. Nonlinear inequalities are converted to an LMI form using Schur complements. Optimizing a nonconvex polynomial is equivalent to the LP over a convex set. Engineering application interests include system analysis, control theory, combinatorial optimization, statistics, and structural design optimization.

A branch-and-bound multi-parametric programming approach for non-convex multilevel optimization with polyhedral constraints

In this paper we develop a general but smooth global optimization strategy for nonlinear multilevel programming problems with polyhedral constraints. At each decision level successive convex relaxations are applied over the non-convex terms in combination with a multi-parametric programming approach. The proposed algorithm reaches the approximate global optimum in a finite number of steps through the successive subdivision of the optimization variables that contribute to the non-convexity of the problem and partitioning of the parameter space. The method is implemented and tested for a variety of bilevel, trilevel and fifth level problems which have non-convexity formulation at their inner levels.

Spontaneous oscillatory contraction (SPOC) in cardiomyocytes.

SPOC (spontaneous oscillatory contraction) is a characteristic state of the contractile system of striated (skeletal and cardiac) muscle that exists between the states of relaxation and contraction. For example, Ca-SPOCs occur at physiological Ca2+ levels (pCa ∼6.0), whereas ADP-SPOC occurs in the virtual absence of Ca2+ (pCa ≥ 8; relaxing conditions in the presence of MgATP), butin the presence of inorganic phosphate (Pi) and a high concentration of MgADP. The concentration of Mg-ADP necessary for SPOC is nearly equal to or greater than the MgATP concentration for cardiac muscle and is several times higher for skeletal muscle. Thus, the cellular conditions for SPOC are broader in cardiac muscle than in skeletal muscle. During these SPOCs, each sarcomere in a myofibril undergoes length oscillation that has a saw-tooth waveform consisting of a rapid lengthening and a slow shortening phase. The lengthening phase of one half of a sarcomere is transmitted to the adjacent half of the sarcomere successively, forming a propagating wave (termed a SPOC wave). The SPOC waves are synchronized across the cardiomyocytes resulting in a visible wave of successive contractions and relaxations termed the SPOC wave. Experimentally, the SPOC period (and therefore the velocity of SPOC wave) is observed in demembranated cardiomyocytes and can be prepared from a wide range of animal hearts. These periods correlate well with the resting heartbeats of a wide range of mammals (rat, rabbit, dog, pig and cow). Preliminary experiments showed that the SPOC properties of human cardiomyocytes are similar to the heartbeat of a large dog or a pig. This correlation suggests that SPOCs may play a fundamental role in the heart. Here, we briefly summarize a range of SPOC parameters obtained experimentally, and relate them to a theoretical model to explain those characteristics. Finally, we discuss the possible significance of these SPOC properties in each and everyheartbeat.

Uplink Interference Management for Coexisting MIMO Femtocell and Macrocell Networks: An Interference Alignment Approach

This paper considers uplink interference management for two-tier cellular systems by way of Interference Alignment (IA). In order to manage the uplink interference caused by macrocell users at the femtocell base stations (FBS), cooperation between macrocell users with the closest femtocell base stations is proposed with the goal of aligning the received signals of macrocell users in the same subspace at multiple FBSs. The precoder design for macrocell users is accomplished using successive semidefinite programming relaxations. The proposed solution aims to minimize the cross-tier interference leaked to the femtocells while providing the macrocell users with a minimum received signal to interference plus noise ratio (SINR) at the macrocell base station (MBS). Intra-tier femtocell interference is dealt with minimum mean squared error (MMSE) interference suppression. Numerical results demonstrate that the proposed two-tier interference management approach improves the performance of femtocell users, while maintaining the desired quality of the communication channel of macrocell users.

On handling cutting planes in interior-point methods for solving semi-definite relaxations of binary quadratic optimization problems

We describe an improved technique for handling large numbers of cutting planes when using an interior-point method for the solution of linear and semi-definite programming relaxations of combinatorial optimization problems. The approach combines an infeasible primal-dual interior-point algorithm with a cutting-plane scheme that does not solve successive relaxations to optimality, but adds and removes cuts at intermediate iterates based on indicators for cut violation and feasibility of the associated slacks. The slack variables of added cuts are initialized using a recently proposed interior-point warm-start technique that relaxes the interiority condition on the original primal-dual variables and enables a restart from the current iterate without additional centring or correction steps. Our computational tests on relaxations of the maximum-cut and single-row facility-layout problem demonstrate that this new scheme is robust for both unconstrained and constrained binary quadratic problems and that its performance is superior to solving only the final relaxation with all relevant cuts known in advance.

Nonlinear Model for Viscoelastic Behavior of Achilles Tendon

Although the mechanical properties of ligament and tendon are well documented in research literature, very few unified mechanical formulations can describe a wide range of different loadings. The aim of this study was to propose a new model, which can describe tendon responses to various solicitations such as cycles of loading, unloading, and reloading or successive relaxations at different strain levels. In this work, experiments with cycles of loading and reloading at increasing strain level and sequences of relaxation were performed on white New Zealand rabbit Achilles tendons. We presented a local formulation of thermodynamic evolution outside equilibrium at a representative element volume scale to describe the tendon's macroscopic behavior based on the notion of relaxed stress. It was shown that the model corresponds quite well to the experimental data. This work concludes with the complexity of tendons' mechanical properties due to various microphysical mechanisms of deformation involved in loading such as the recruitment of collagen fibers, the rearrangement of the microstructure (i.e., collagens type I and III, proteoglycans, and water), and the evolution of relaxed stress linked to these mechanisms.

An Improved Interior-Point Cutting-Plane Method for Binary Quadratic Optimization

Abstract We describe an improved technique for handling large numbers of cutting planes when using an interior-point method for the solution of linear or semidefinite relaxations in binary quadratic optimization. The approach does not require solving successive relaxations to optimality but chooses cuts at intermediate iterates based on indicators of inequality violation and feasibility of their slacks, which are initialized using a recently proposed warmstart technique without any additional correction steps. Computational tests on instances of max-cut suggest that this new scheme is superior to solving only the final relaxation with all relevant cuts known in advance.

On Interior-Point Warmstarts for Linear and Combinatorial Optimization

Despite the many advantages of interior-point algorithms over active-set methods for linear optimization, one of the remaining practical challenges is their current limitation to efficiently solve series of related problems by an effective warmstarting strategy. As a remedy, in this paper we present a new infeasible-interior-point approach to quickly reoptimize an initial problem instance after data perturbations, or a new linear programming relaxation after adding cutting planes for discrete or combinatorial problems. Based on the detailed complexity analysis of the underlying algorithm, we perform a comparative analysis to coldstart initialization schemes and present encouraging computational results with iteration savings of around 50% on average for perturbations of the Netlib linear programs (LPs) and successive linear programming relaxations of max-cut and the traveling salesman problem.

Causes and effects of geochemical variations in late Cenozoic volcanism of the Foça volcanic centre, NW Anatolia, Turkey

The Foça volcanic centre (FVC) occupies a NNE–SSW-oriented highland between two EW-trending structural grabens in western Anatolia, and includes early–middle Miocene mafic and felsic extrusive suites. Its evolutionary history consists of an older volcano stage (16.6–16.1 Ma) and a younger volcano stage (15.2–14.1 Ma), which are characterized by different eruption styles and compositional and geochemical features. The older units include high-K calc-alkaline basalt, andesite, trachyandesite, rhyolite, and associated pyroclastic rocks, which formed during ignimbrite eruptions and plinian–subplinian air-fall episodes. The younger sequences are composed of shoshonitic–alkaline basalt lavas and dikes, trachytes, phonolites, and phonolitic ignimbrites that formed strombolian cones. The Foça volcanic rocks display high initial 87Sr/86Sr ratios (0.7075–0.7082 for the calc-alkaline mafic lavas, 0.7073–0.7064 for calc-alkaline felsic lavas, and 0.7063–0.7075 for the alkaline series) and low 143Nd/144Nd (0.5123–0.5125 in both series with ϵNd values varying from − 1.3 to − 6.0). These FVC geochemical features are consistent with those of other volcanic centres in western Anatolia (i.e. Bodrum, Urla-Cumaovası) and on the Aegean islands (i.e. Samos, Patmos, Chios). The geochemical and Sr–Nd isotopic compositions of the Foça volcanic units suggest that both lithospheric and asthenospheric mantle melts were involved in their evolution; however, the mantle lithosphere fingerprint was diminished by the middle Miocene, as the asthenospheric mantle melt input became dominant. These findings, combined with the bimodal character of post-collisional volcanism in the study area, suggest that geochemical variations in the nature of volcanism from calc-alkaline to alkaline and the changes in tectonic regimes through time may have been caused by successive thermal relaxations associated with possible ‘piecemeal’ removal of the base of subcontinental lithospheric mantle beneath western Anatolia. This interpretation is more plausible than a catastrophic collapse or wholesale delamination of the entire lithospheric mantle. Asthenospheric upwelling caused by this inferred convective thinning provided underplating of mantle-derived magmas, which interacted with the previously metasomatized lithospheric mantle and the overlying crust, resulting in their partial melting and in production of high-K calc-alkaline to mildly alkaline, incompatible element enriched magmas in separate magma chambers in which fractional crystallization occurred.

Influence of sintering conditions and doping on the dielectric relaxation originating from the surface layer effects in CaCu 3Ti 4O 12 ceramics

Detailed investigations into the dielectric dispersion phenomenon in the giant dielectric constant material CaCu 3Ti 4O 12 (CCTO) around room temperature revealed the existence of two successive dielectric relaxations. In the temperature domain, a new dielectric relaxation was clearly observed around 250 K, in addition to the well-investigated dielectric relaxation close to 100 K. The effect of sintering and doping (La 3+) on the strength of these dielectric relaxations were studied in detail. The sintering temperature as well as its duration was found to have tremendous influence on the dielectric relaxation that was encountered around 250 K. This Maxwell–Wagner (M–W) type of relaxation was found to be originating from the surface layer containing the Cu-rich phase, which was ascribed to the difference in the oxygen content between the surface and the interior of the sample. Interestingly, this particular additional relaxation was not observed in La 2/3Cu 3Ti 4O 12, a low dielectric constant member of the CCTO family, in which the segregation of Cu-rich phase on the surface was absent. Indeed the correlation between the new relaxation and the presence of Cu-rich phase in CCTO ceramics was further corroborated by the absence of the same after removing the top and bottom layers.

Optimization of Polynomials on Compact Semialgebraic Sets

A basic closed semialgebraic subset S of $\R^n$ is defined by simultaneous polynomial inequalities $g_1\ge 0,\dotsc,g_m\ge 0$. We give a short introduction to Lasserre's method for minimizing a polynomial f on a compact set S of this kind. It consists of successively solving tighter and tighter convex relaxations of this problem which can be formulated as semidefinite programs. We give a new short proof for the convergence of the optimal values of these relaxations to the infimum $f^\ast$ of f on S which is constructive and elementary. In the case where f possesses a unique minimizer $x^\ast$, we prove that every sequence of nearly optimal solutions of the successive relaxations gives rise to a sequence of points in $\R^n$ converging to $x^\ast$.

Solving nonconvex optimization problems

It is well known that most analysis and design problems in robust and nonlinear control can be formulated as global optimization problems with polynomial objective functions and constraints. The objective of this article is to show how GloptiPoly can solve challenging nonconvex optimization problems in robust nonlinear control. GloptiPoly is a general-purpose software with a user-friendly interface. First, we describe several nonconvex optimization problems arising in control system analysis and design. These problems involve multivariable polynomial objective functions and constraints. We then review the theoretical background behind GloptiPoly. Next, an example is presented to illustrate the successive linear matrix inequality relaxations and general features of the GloptiPoly software. Finally, we apply GloptiPoly to several control-related problems.

Dual approach using a variant perimeter constraint and efficient sub-iteration scheme for topology optimization

To prevent numerical instabilities associated with the mesh-dependence, checkerboards and grey regions in topology optimization, a variant perimeter-constrained version of the SIMP algorithm is proposed using a smooth and quadratic function. In order to have an efficient implementation and to make sure the strict satisfaction of such an upper-bound perimeter constraint, a diagonal quadratic approximation of the perimeter constraint is used in the construction of each explicit optimization subproblem. The latter is then solved by a dual sub-iteration scheme. Numerical results show that the incorporation of such a sub-iteration scheme leads to a convergent solution without needs of move-limits or artificial control parameters. In addition to this, it is found that successive relaxations of the perimeter constraint by increasing the upper-bound tend to regularize the topology solution and result in a checkerboard free and satisfactory design solution without grey regions.