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- Creator:
- Paig-Tran, Erin
- Description:
- Solid-liquid filtration is a ubiquitous process found in industrial and biological systems. Although implementations vary widely, almost all filtration systems are based on a small set of fundamental separation mechanisms, including sieve, cross-flow, hydrosol, and cyclonic separation. Anatomical studies showed that manta rays have a highly specialized filter-feeding apparatus that does not resemble previously described filtration systems. We examined the fluid flow around the manta filter-feeding apparatus using a combination of physical modeling and computational fluid dynamics. Our results indicate that manta rays use a unique solid-fluid separation mechanism in which direct interception of particles with wing-like structures causes particles to “ricochet” away from the filter pores. This filtration mechanism separates particles smaller than the pore size, allows high flow rates, and resists clogging.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Biological Sciences
22. Densities and zonation patterns of native and non-indigenous oysters in southern California bays
- Creator:
- Zacherl, Danielle
- Description:
- Worldwide, artificially armored shorelines can dominate available estuarine habitat. Increases in artificial substrata in southern California, USA, coincide with increased abundances of nonindigenous species. The US west coast Olympia oyster, Ostrea lurida, may be particularly sensitive to changes in natural habitat availability and recently experienced large-scale declines in abundance. Simultaneously, the non-indigenous and often invasive Pacific oyster, Crassostrea gigas, has been introduced along the US West Coast, including into southern California estuaries where its impact is unstudied. We recorded C. gigas and O. lurida densities from October 2010 through July 2017 throughout southern California on several habitat types and as a function of tidal elevation as a critical baseline for evaluating impacts of C. gigas. Ostrea lurida was present in higher proportions than C. gigas in hard substrate-dominated habitats, whether natural or human-introduced. A strong zonation pattern emerged; C. gigas achieved its maximum density above +0.4 m MLLW versus O. lurida at or below +0.2 m MLLW. These data reveal the optimal tidal elevation for placement of a restored O. lurida bed and establish a critical baseline and techniques for evaluating future changes in oyster density.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Biological Sciences
- Creator:
- Yang, Joshua
- Description:
- Background Non-communicable diseases (NCDs) account for over two-thirds of deaths worldwide, and global efforts to address NCDs have accelerated. Current prevention and control efforts rely primarily on individual behavior/lifestyle approaches that place the onus of responsibility for health on the individual. These approaches, however, have not stopped the increasing trend of NCDs worldwide. Thus, there is urgent need for exploring alternative approaches in order to attain the aim of reducing global premature NCDs mortality by 25% by 2025, and meeting the NCD reduction objective in the Sustainable Development Goals. Discussion We suggest the need for a structural approach to addressing the NCDs epidemic that integrates social science and public health theories. We evaluate two overarching principles (empowerment and human rights) and three social determinants of health (labor and employment, trade and industry, and macroeconomics) addressed in the 2013 Global Action Plan for the Prevention and Control of NCDs to demonstrate how a structural approach to NCDs can be incorporated into existing NCD interventions. For each area considered, theoretical considerations for structural thinking are provided and conclude with recommended actions. Conclusion Achieving the global health agenda goals of reducing NCDs mortality will require a shift to a paradigm that embraces concerted efforts to address both behavioral/lifestyle factors and structural dimensions of NCDs.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Public Health
- Creator:
- Lockie, Robert
- Description:
- This study investigated relationships that linear speed and lower-body power have on change-of-direction (COD) speed in collegiate women soccer players. Data from two Division I (n = 39) and one Division II (n = 18) schools were analyzed. Subjects were assessed in: power (vertical jump (VJ); jump height, peak anaerobic power measured in watts (PAPw), power-to-body mass ratio (P:BM); linear speed (10-m sprint); and COD speed (modified T-test (MTT), 505, COD deficit). Independent samples T-tests derived significant between-group differences, with effect sizes (d) calculated. Pearson’s correlations determined relationships between COD speed, linear speed, and power, with regression equations calculated. Division I players demonstrated superior 505, COD deficit, VJ height, PAPw, and P:BM (d = 1.09–2.21). Division II players were faster in the MTT (d = 1.51). For all players, the 505 correlated with the 10-m sprint (r = 0.39–0.53) and VJ height (r = −0.65–0.66), while the COD deficit related to the 10-m sprint (r = −0.77–0.82). The regression data supported these results. Division I players were superior in the 505 and COD deficit, and expressed their power in the 180° 505 task. Division II players should enhance lower-body power and the ability to perform 180° direction changes.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Kinesiology
- Creator:
- Verdugo, Anael
- Description:
- This paper presents a computational study of the stability of the steady state solutions of a biological model with negative feedback and time delay. The motivation behind the construction of our system comes from biological gene networks and the model takes the form of an integro-delay differential equation (IDDE) coupled to a partial differential equation. Linear analysis shows the existence of a critical delay where the stable steady state becomes unstable. Closed form expressions for the critical delay and associated frequency are found and confirmed by approximating the IDDE model with a system of delay differential equations (DDEs) coupled to ordinary differential equations. An example is then given that shows how the critical delay for the DDE system approaches the results for the IDDE model as becomes large.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Mathematics
- Creator:
- Verdugo, Anael
- Description:
- The repressilator is a genetic network that exhibits oscillations. The net-work is formed of three genes, each of which represses each other cyclically, creating a negative feedback loop with nonlinear interactions. In this work we present a computational bifurcation analysis of the mathematical model of the repressilator. We show that the steady state undergoes a transition from stable to unstable giving rise to a stable limit-cycle in a Hopf bifurcation. The nonlinear analysis involves a center manifold reduction on the six-dimensional system, which yields closed form expressions for the frequency and amplitude of the oscillation born at the Hopf. A parameter study then shows how the dynamics of the system are influenced for different parameter values and their associated biological significance.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Mathematics
27. Enhancing Learning Power through First-Year Experiences for Students Majoring in STEM Disciplines
- Creator:
- Koch, Robert
- Description:
- Academic programs targeted for first-time students can help their persistence in STEM majors. Our project, ASCEND STEM, included three first-year experiences (FYEs) designed to offer students the skills that would help them successfully traverse potential barriers to academic success. In the FYEs, we sought to strengthen the learning power, improve the academic achievements, and increase the postsecondary success of first-time, full-time freshmen majoring in a STEM discipline. Two models of FYE were offered in three settings—two scenarios were for engineering majors and the third for science and mathematics majors. Both models tested whether the offering of literacy skill building in the context of discipline knowledge acquisition strengthened learning power (as measured by the Effective Lifelong Learning Inventory) and asked whether this could affect academic success and persistence within the STEM major. We found that either model one, integrating literacy skill building and discipline-based concepts into a single course (the approach used in science and math), or model two, pairing a literacy skill building course with either a discipline-based course or a special group support program (the approach used in engineering), improved learning power. Increases in learning power were a valid predictor of improved grades and persistence in engineering where a highquality control group was available.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Biological Sciences
- Creator:
- Schenk, H. Jochen
- Description:
- Premise of the Study Xylem sap in angiosperms moves under negative pressure in conduits and cell wall pores that are nanometers to micrometers in diameter, so sap is always very close to surfaces. Surfaces matter for water transport because hydrophobic ones favor nucleation of bubbles, and surface chemistry can have strong effects on flow. Vessel walls contain cellulose, hemicellulose, lignin, pectins, proteins, and possibly lipids, but what is the nature of the inner, lumen‐facing surface that is in contact with sap? Methods Vessel lumen surfaces of five angiosperms from different lineages were examined via transmission electron microscopy and confocal and fluorescence microscopy, using fluorophores and autofluorescence to detect cell wall components. Elemental composition was studied by energy‐dispersive X‐ray spectroscopy, and treatments with phospholipase C (PLC) were used to test for phospholipids. Key Results Vessel surfaces consisted mainly of lignin, with strong cellulose signals confined to pit membranes. Proteins were found mainly in inter‐vessel pits and pectins only on outer rims of pit membranes and in vessel‐parenchyma pits. Continuous layers of lipids were detected on most vessel surfaces and on most pit membranes and were shown by PLC treatment to consist at least partly of phospholipids. Conclusions Vessel surfaces appear to be wettable because lignin is not strongly hydrophobic and a coating with amphiphilic lipids would render any surface hydrophilic. New questions arise about these lipids and their possible origins from living xylem cells, especially about their effects on surface tension, surface bubble nucleation, and pit membrane function.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Biological Sciences
- Creator:
- Stapp, Paul
- Description:
- In late 2009, the Catalina Island Conservancy began using fertility control to replace periodic removals to manage an introduced population of American bison (Bison bison) on the island. Through the application of the immunocontraceptive vaccine porcine zona pellucida (PZP), population growth was slowed within 1 year, and halted over time. In response to lingering questions about the use of PZP to manage large, free-ranging wildlife populations, we sought to determine the reversibility of PZP by ceasing the annual application to a subset of 15 bison cows and monitoring for subsequent calf arrival, and to document changes in the timing and length of the breeding season in response to PZP by monitoring breeding behavior and assessing fecal progesterone (FP) levels for all 60 resident cows over a 13-month period. As of June 2017, no new calves had been observed on the island, suggesting that, following repeated annual treatment with PZP (3 or 4 years), bison do not resume normal reproduction for at least 4 or 5 years, and that fewer treatments would be advisable if a faster return to fertility is desired. Based on observations of bull and cow behavior, and FP levels, cows displayed estrous cycles consistently throughout the study period, indicating that bison may ovulate year-round when conception and its consequences, e.g., lactation and presence of calves, are blocked. Because there is little evidence that an extended breeding season would negatively impact the health of bulls or result in large numbers of out-of-season births on Catalina, PZP appears to be a highly effective tool for managing the population of introduced bison on the island. However, the extended period of contraception and breeding activity of both cows and bulls may make PZP less suitable in high-latitude, predator-rich environments where bison conservation remains a top priority.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Biological Sciences
- Creator:
- Rathbun, Matt
- Description:
- A twisted torus knot is a knot obtained from a torus knot by twisting adjacent strands by full twists. The twisted torus knots lie in F, the genus 2 Heegaard surface for S3. Primitive/primitive and primitive/Seifert knots lie in F in a particular way. Dean gives sufficient conditions for the parameters of the twisted torus knots to ensure they are primitive/primitive or primitive/Seifert. Using Dean’s conditions, Doleshal shows that there are infinitely many twisted torus knots that are fibered and that there are twisted torus knots with distinct primitive/Seifert representatives with the same slope in F. In this paper, we extend Doleshal’s results to show there is a four parameter family of positive twisted torus knots. Additionally, we provide new examples of twisted torus knots with distinct representatives with the same surface slope in F.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Mathematics