Gilbert R. Peralta
Department of Mathematics and Computer Science
College of Science
UP Baguio
Analysis of a Nonlinear Fluid-Structure Interaction Model with Mechanical Dissipation and Delay, Nonlinearity, 32: 5110-5149, 2019
The interaction between a solid and a fluid has been studied extensively in the past decades. Applications typically arise in several engineering designs and blood flow models. The research takes into account a model where there is a delay in the feedback control on the structural component. This entails that there is a time-lag for the control to be effective. It is known that delays can lead to instability. Nevertheless, the study shows that under a suitable strength of the control, one can still steer the state to an equilibrium even if delays are present in the system.
Significance:
A fluid-structure interaction model with discrete and distributed delays in the structural damping is studied. The fluid and structure dynamics are governed by the Navier–Stokes and linear elasticity equations, respectively. Due to the presence of delay, a crucial ingredient of the weak formulation is the use of hidden boundary regularity for transport equations. In two space dimensions, it is shown that weak solutions are unique. For smooth and compatible data, we establish the existence of the pressure and by applying micro-local analysis, further regularity of the solutions is available. Finally, the exponential stability of the system is obtained through an appropriate Lyapunov functional.
Link to the article: https://iopscience.iop.org/article/10.1088/1361-6544/ab46f5
Impact factor: (2018/2019) 1.729
Gilbert R. Peralta
Department of Mathematics and Computer Science
College of Science
UP Baguio
Uniform Exponential Stability of a Fluid-Plate Interaction Model Due to Thermal Effects, Evolution Equations and Control Theory, 9 (1): 39-60, 2020
The exponential stability of an incompressible fluid, for example water, in a container where part of the boundary is composed of a thin elastic plate was established. In particular, the total energy of the system decays exponentially fast, however, the rate depends on the physical properties of the fluid and the material characteristics of the plate. Stabilization is the first step towards more challenging aspects in systems theory such as control, observation, detection and optimization. The analysis presented in this work can be utilized in numerical approximations and simulations of coupled fluid-plate models, for instance, in the development of stable finite element schemes.
Significance:
We consider a coupled fluid-thermoelastic plate interaction model. The fluid velocity is modeled by the linearized 3D Navier-Stokes equation while the plate dynamics is described by a thermoelastic Kirchoff system. By eliminating the pressure term, the system is reformulated as an abstract evolution problem and its well-posedness is proved by semigroup methods. The dissipation in the system is due to the diffusion of the fluid and heat components. Uniform stability of the coupled system is established through multipliers and the energy method. The multipliers used for thermoelastic plate models in the literature are modified in accordance to the applicability of a certain Stokes map.
Link to the article: https://www.aimsciences.org/article/doi/10.3934/eect.2020016
Impact factor: (2018/2019) 1.048
Cherry P. Fernandez-Colorado
Department of Veterinary Praclinical Sciences
College of Vetirenary Medicine
UP Los Baños
Riemerella anatipestifer Infection in Ducks Induces IL-17A Production but not IL-23p19, Scientific Reports: 13269,
DOI: 10.1038/s41598-019-49516-z, 2019
Figure 6. mRNA expression profiles of duIL-23p19, IL-12p40 and Th17 cytokines in the spleen of R. anatipestifer-infected ducks at early time points. Two-week-old healthy ducks were infected intramuscularly with 5 x 107 CFU of R. anatipestifer serotype 7. Spleens were collected at the indicated time points and subjected to qRT-PCR. mRNA expression levels were normalized to those of β-actin and calibrated using the expression levels in uninfected birds (NC). Data are shown as the mean ± SE from two independent experiments. *P < 0.05, **P < 0.01 and ***P < 0.001 indicate statistical significance. RA, R. anatipestifer
Riemerella anatipestifer is one of the most harmful bacteria that greatly affects the duck industry. Riemerella anatiestifer infection causes polyserositis, septicemia and meningitis and is associated with a 5-75% mortality rate depending on the virulence of the strain. Due to the lack of information on bacterial-host interactions and host immune responses, the control of Riemerella anatipestifer infection has only been partially successful. Cytokines play an important role in immunomodulation especially in directing the innate and adaptive immune responses. In recent immunological studies, the infection is associated with the production of proinflammatory cytokines, including IL-17A, which is produced by Th17 immune cells and IL-23 cytokine is important in the development of these Th17 cells. IL-23p19 in ducks is still unknown, thus, in this study, duck IL-23p19 was cloned, characterized and investigated its mRNA expression during the infection. Expression of IL-23p19 was relatively high in mitogen-activated splenic lymphocytes as well as in splenic lymphocytes and macrophages stimulated with Riemerella anatipestifer. However, expression levels of duIL-23p19 were not significantly upregulated at early time points in Riemerella anatipestifer infection in ducks. In sera collected at 24 h after this infection, IL-23p19 expression levels were unchanged, whereas IL-17A significantly increased. These results suggest that during Riemerella anatipestifer infection, IL-17A can have biological functions independent of duck IL-23p19, especially at early times post-infection.
Significance:
This work adds knowledge on the host-pathogen interactions and on host protective immunity to Riemerella anatipestifer, which is considered as one of the most important pathogens in the duck industry. The avian immune system provides an important model for the study of basic and applied immunology. Thus, this work also shows the important contributions of immune-related cytokines to host protective immunity in ducks during Riemerella anatipestifer infection.
Link to the article: https://doi.org/10.1038/s41598-019-49516-z
Impact factor: (2018/2019) 4.011
Alice Prieto-Carolino1 and Bernice Vania Landoy Mamauag1
1Division of Social Sciences, College of Arts and Sciences (UP Visayas)
Pagdipara: Caring Work by Poor Elderly Women in Coastal Communities in Iloilo, Philippines, Asian Journal of Womens Studies, 25 (3): 375-395, 2019
In the Philippine context, women largely take on the caring work and this is perceived as natural or a given. But if we consider the influence of patriarchy then caring is done by women due to the dominance of men over them. Since capitalism values money, most of the caring work of women which is unpaid is perceived as less important than the paid work of men. Further, family ethics dictates that family concerns precede over women’s personal concerns, then they are expected to devote their lives to promote the family’s well-being, sometimes even at their own expense.
The stories of the three, poor Filipino elderly women who live in coastal communities in Iloilo province show the challenges and issues they face in dealing with their gendered social relations and their marginalized status. They are expected to subscribe to cultural norms of being the ideal wives; despite their age they continue their volunteer work as barangay health workers; they are expected to become dutiful daughters and to adjust to their husband’s struggles against the provider stereotype.
The paper asserts that poverty among poor, elderly women adds to their caring work which further reinforces their marginalization. The family as a social construct needs to be reexamined especially the power relations between women and men that disadvantage women in terms of the benefits and costs of care work.
Significance:
Our study gives voice to older women in coastal communities as they describe the many ways by which they care for their families and their communities. We also unpack the caring and care work that these older women do and show that care work contributes to these women’s marginalization. We assert that the relationships that women are embedded in should be reexamined so that caring and care work should not be burdensome to women.
Link to the article: https://www.tandfonline.com/doi/pdf/10.1080/12259276.2019.1646493
Impact factor: (2018/2019) 0.228
Menandro N. Acda1, Rosalie C. Mendoza1, Jeanette O. Grande1
1Department of Forest Products and Paper Science, College of Forestry and
Natural Resources (UP Los Baños)
Effect of Keratin Fibers on Setting and Hydration Characteristics of Portland Cement, Journal of Natural Fibers: https://doi.org/10.1080/15440478.2019.1701604, 2019
Fig. 1. Waste chicken feathers from poultry processing plants create serious solid waste disposal problem.
Fig. 2. Measurement cement setting time using Vicat apparatus.
The effect of varying amounts of keratin fibers on the setting and hydration behavior of Portland cement was investigated. Both initial and final cement setting times increased by up to 46% and 54%, respectively, with an increasing amount of keratin fibers from 2% to 6% by mass of cement compared to unmodified control samples. Apparently, the addition of keratin fibers retarded cement hydration although the mechanism of this phenomenon is still unclear. Thermal and infrared spectroscopic analyses suggested that keratin fibers possibly blocked hydrations sites or prevented cement crystallization which retarded cement curing. Considering the potential use of keratin fibers as reinforcement in mortar or cement composites, further research is necessary to understand the kinetics and mechanism of said effect. Pretreatment and refining to induce fibrillation should also be explored to reduce freeness and drainage rate to levels suitable for wet mat formation if this material should be used in composite manufacture.
Significance:
Chicken feather is a waste product of the poultry industry. Billions of kilograms of waste chicken feathers are produced in commercial dressing plants to supply the increasing demand for poultry meat. Consequently, the large volume of waste feather creates a serious solid waste disposal problem in many countries. Chicken feathers are often burned, buried in landfills or recycled into low-quality animal feeds. However, these disposal methods are expensive, restricted or generate greenhouse gases that pose danger to both man and the environment. Chicken feather is made up of keratin, an insoluble and highly durable protein found in the hair, hoofs, and horns of animals. A potential high volume, high value use of waste chicken feather is a substitute wood fiber in cement composites. Studies have shown that cement bonded chicken feather fiber composites had excellent decay and termite resistance which made them very attractive as construction materials in tropical climates. However, stiffness (MOE) and flexural strength (MOR) were slightly lower compared to that of unmodified control boards. Apparently, the addition of chicken feather fiber resulted in decreased mechanical strength. It is widely believed that this is due to the poor adhesion of the organic fiber to the inorganic cement. It is also suspected that keratin fibers affect the setting and hydration behavior of cement like that observed with wood fibers. Unfortunately, no studies to date have been conducted to support this hypothesis. The present paper reports on the effect of keratin fibers from chicken feathers on the setting and hydration characteristics of the cement matrix.
Link to the article: https://www.tandfonline.com/eprint/BK998Q34SC2IUXMF58XP/full?target=10.1080/15440478.2019.1701604
Impact factor: (2018/2019) 1.252
