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Surfactant Formulations to Enhance Triclopyr Amine Efficacy: Effects on Adhesion, Retention and Contact Phytotoxicity On Three Hardwood SpeciesForster, W. Alison II 13 November 1998 (has links)
Loblolly pine (Pinus taeda L) is the leading Southern (USA) pine, in terms of acres planted (Fortson et al.,1996). Since commercial forest acreage is predicted to remain fairly constant over the next 50 years, productivity must be increased if the South is going to meet a larger share of the nation's timber supply needs (Gjerstad and Barber, 1987). Hardwoods have been shown to have a consistent negative growth impact on pines, and uncontrolled hardwoods continue to compete aggressively with pines throughout a rotation, especially when hardwoods remain in the pine canopy.
Competing vegetation can be efficiently controlled by herbicides, which need to be formulated either in-can or in-tank to allow them to perform optimally. Adjuvants have proven essential to increasing the efficacy of herbicides, due to their ability to consistently improve the performance of the basic pesticide product. There are, broadly speaking, two routes by which adjuvants can do this. The first is the minimization of off target deposition and second, by the maximization of the herbicidal effect once it is placed on the target ( Reeves, 1989). The major contributors to off- target deposition and retention are drift, in-flight volatilization, droplet shatter, bounce or runoff, washoff, and removal by wind. These losses result in pesticides never reaching the target or achieving only transitory deposition. There are two basic methods of maximizing the effect of the pesticide once it is on the target. The first is to improve coverage by the spray solution, which can be accomplished by lowering the surface tension of the spray with surfactant materials. The second is by improving the penetration or uptake into the target. Organosilicone surfactants can reduce the surface tension of aqueous pesticides far below that which is possible with nonsilicone surfactants, resulting in efficient wetting of even the most hydrophobic leaf surfaces. Additionally, by virtue of their low surface tension, these adjuvants can significantly increase the uptake of active chemicals directly into the plant via stomatal infiltration ( Stevens et al., 1991).
Triclopyr ([(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid) has been found to be an effective herbicide for hardwood control. Its two commercial formulations, a triethylamine (TEA) salt (Garlon 3A) and a butoxyethyl ester ( Garlon 4 ), vary considerably in their acceptability. The current ester formulation has two undesirable characteristics. One is that all ester formulations, regardless of chain length, have some volatility which is usually more than that of water-soluble salts. The second is that the current ester formulation utilizes a kerosene solvent which is known to cause rapid foliar necrosis (possibly inhibiting herbicide translocation) and is a suspected carcinogen ( Zedaker et al., 1995). In most applications, the ester formulation has been more efficacious than the amine formulation on both an equal active ingredient basis and on an equal cost basis. Research had demonstrated a potential to enhance the uptake of triclopyr through the use of organosilicones; however, significant problems still existed. It was found that the commercial TEA formulation of triclopyr (Garlon 3A) was "antagonistic" to the organosilicone surfactant Silwet L-77. To take full advantage of the properties of organosilicones, the antagonistic co-formulants of Garlon 3A needed to be removed or replaced, the best surfactant formulation identified, and a cost-effective concentration of the surfactant(s) needed to be found.
To do this adequately required that both physico-chemical processes and biological processes be studied. The relevant physico-chemical processes involved in a formulation's effect on spray impaction on the target plant include adhesion, reflection, retention and run-off. The important biological processes include the uptake and translocation of the herbicide into the plant.
The objectives of this study were: to evaluate the influence of formulation, active ingredient concentration, droplet size and leaf surface (adaxial vs. abaxial) on contact phytotoxicity, adhesion and retention to Acer rubrum, Liquidambar styraciflua and Quercus rubra by triclopyr formulations containing organosilicone surfactants and mixtures of silicone plus conventional surfactants. The adhesion and retention studies also evaluated the influence of leaf angle. Further objectives were to evaluate the influence of formulation and active ingredient concentration on spray retention by the adaxial and abaxial leaf surface of the selected species under field and track-sprayer conditions and to determine whether leaf characteristics (wax character and leaf angle ) could explain adhesion / retention.
Garlon 4, Garlon 3A and Triclopyr TEA + sequestrant (each at 0.32%, 1.6% and 3.2% ae) plus various concentrations of the surfactants Polyglycol 26-2, Rhodasurf DA-630, Surfadone LP-100, Silwet L-77 and Silwet 408, were tested for contact phytotoxicity, adhesion and retention on the adaxial and abaxial leaf surfaces of sweetgum, red oak and red maple.
Little or no contact phytotoxicity was observed with any formulation applied to the adaxial surface within 6 hours; some phytotoxicity was noted within 24 hours. Abaxial surface treatments showed much greater contact phytotoxicity. Contact phytotoxicity was caused by (1) increasing concentrations of stock triclopyr products, and (2) the influence of the organosilicone surfactants. However, these results were very species dependent. Conclusions made from the contact phytotoxicity study were: if the droplet size becomes too big, then efficacy will be reduced; increasing the concentration of active ingredient above a certain limit will not increase efficacy, and may in fact reduce it; the addition of the organosilicone surfactants Silwet L-77 and Silwet 408 delayed and reduced phytotoxicity in red oak ( the most susceptible species to contact phytotoxicity), and to a lesser extent in red maple, but increased the rate in sweetgum.
Major influences on adhesion were: droplet size ( increasing droplet size decreased adhesion); adaxial/abaxial leaf surface (abaxial adhesion less than adaxial); product concentration (increasing product concentration increased adhesion); leaf angle (increasing leaf angle decreased adhesion); and addition of surfactants (variable adhesion).
All new formulations gave greater adhesion than the commercial formulations, with Triclopyr TEA plus sequestrant plus n-octyl pyrrolidone plus Silwet 408 giving, overall, the greatest adhesion. Increasing product concentration gave greater adhesion. Increasing droplet size and angle of impact reduced adhesion. The adaxial leaf surface showed higher adhesion than the abaxial leaf surface. Adhesion was higher on sweetgum, followed by red oak, with red maple being the most difficult species to get formulations to adhere to.
Whereas increasing product concentration improves adhesion, the lowest contact phytotoxicity result would be from lowering product concentration. Looking at both sets of results, the best product concentration of those studied would then be 1.6% ae as this can provide high adhesion, while still enabling us to choose a formulation which gives minimal contact phytotoxicity.
In the laboratory, formulation had no significant effect on retention. However, there are other considerations which affect retention that need to be kept in mind. It was observed that droplets containing organosilicone could impact an already wetted surface and still adhere or be retained, whereas those droplets not containing any organosilicone surfactant would bounce quite a distance on impact with a pre-wetted surface. Impaction with an already wetted surface was not part of this study, and therefore was not studied quantitatively. Also, formulations containing organosilicone surfactants provide greater "wrap-around" to the lower surface ( Forster and Zabkiewicz, 1998), which is of great benefit when stomata are only on the abaxial surface, as is the case with these species.
Concentration and leaf angle also had no significant effect on retention. Droplet size was significant, with retention decreasing with increasing droplet size. Retention by the adaxial surface was significantly higher than retention by the abaxial surface. There was no significant difference overall between sweetgum and red oak, but retention by red maple was significantly lower.
Spray retention by the adaxial and abaxial leaf surfaces of the three tree species was also characterized in a field experiment conducted on a right of way site in North Anna, Virginia, USA. Amine ( Garlon 3A) formulations of triclopyr combined with Silwet 408, and the commercial triclopyr ester formulation, Garlon 4, were applied using a Radiarc sprayer equipped with 0.508 mm nozzles (approx. 1000 um droplets) applying 140 l/ha. The addition of the organosilicone surfactant Silwet 408 to the amine formulation gave the same total deposition as the commercial ester formulation, Garlon 4, while enhancing the abaxial retention as a percentage of total deposition. Thus the addition of organosilicone surfactant may have the ability to enhance herbicide uptake via the abaxial leaf surface, and therefore enhance efficacy. Field trial results showed that the alcohol ethoxylate, DA6, is not an essential component of the triclopyr amine / Silwet 408 formulation, in terms of retention.
The field trial application was also simulated on sweetgum, using a track-sprayer at the NZ Forest Research Institute Ltd. As in the field trial, the addition of Silwet 408 to triclopyr amine greatly enhanced abaxial retention as a percentage of total deposition, compared to that of Garlon 4. However, the track-sprayer results were very different from the field results, with amounts of adaxial and abaxial retention and total deposition much lower.
In agreement with published literature, it was found that the micro-roughness of the leaf surface can be used as a guide to explain adhesion results. The difference among trees in terms of leaf angles appeared to be much less important in explaining retention. / Master of Science
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THE CHANGING LANDSCAPE OF NEW ENGLAND COLLEGES AND UNIVERSITIES: WHAT FACTORS ARE ASSOCIATED WITH THE RETENTION OF BLACK, LATINX, AND WHITE STUDENTS?Rodgers-Tonge, Decorti, 0000-0002-0990-6007 January 2021 (has links)
Long-term declines in birth rates pose a threat to the economic viability of higher education institutions (HEIs), and these institutions must strategically plan for these changes. Increasing the enrollment and retention of underrepresented Black and Latinx students is one potential strategy to offset declining numbers of high-school graduates. While educational attainment has increased overall during the last two decades, Black and Latinx students continue to have lower educational attainment levels than White students. This study uses quantitative data from the Integrated Postsecondary Education Data System (IPEDS) from 2000 to 2018 to estimate enrollment and retention levels of Black, Latinx, and White students in Higher Educational Institutions (HEIs) in the New England Region (NER). The study estimates correlations between Black, Latinx, and White enrollment and retention levels, revealing a negative impact on Black and Latinx enrollment and retention as White enrollment increases. This research likewise reveals a decrease in White enrollment as Black and Latinx enrollment increases.
Additionally, this study uses a K-means cluster analysis to understand the association between enrollment and retention level performance of NER HEIs. Findings from two different cluster analyses show 1) a negative pattern of retention of Blacks and Latinx students as enrollment for these populations increases in HEIs and 2) a positive retention pattern for a subset of HEIs with higher retention levels with lower numbers of Black and Latinx enrollment totals. This proposal describes and interprets these findings and proposes new research examining institutional characteristics that may give rise to Blacks and Latinx students' retention levels. This study considers a wide range of institutional characteristics, including supportive programming and the types of financial aid packages specifically designed to retain students, while accounting for endowment and institutional size. This dissertation aims to provide NER HEI administrators with data that can inform short and long-term strategic planning. / Business Administration/Interdisciplinary
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Characteristics of Persisting Students Utilizing the Retention Self-Study Framework: A Case StudyGasser, Ray F January 2006 (has links)
Although retention has become a critical priority for most institutions, this interest has not yielded significantly increased retention rates over the past 30 years. Understanding how each individual institution could increase retention rates will help to avoid the critics of higher education who have grown wary over the increasing costs. In order to justify the increases in tuition, higher education must show that students can persist, graduate, and succeed in the 'real world'.This exploratory study seeks to provide insight into persistence by focusing on understanding the common themes of students who persisted. In 2001, Woodard, Mallory, & DeLuca published a research article providing a comprehensive structure that incorporates an extensive body of student retention research along with the authors' own research. The framework provides institutions with a model to explore the areas that affect student retention. The authors describe four major components to retention: the student sphere, institutional sphere, academic affairs sphere, and student services sphere. Within each of these spheres is a number of characteristics that research indicates effects retention. The Retention Self-Study Framework (2001) draws heavily from the research of Vincent Tinto (1975, 1987, 1993), John Bean (1980, 1983), Alexander Astin (1984), and Ernest Pascarella (1980).This study investigates the extent to gender, race, high school class rank, socio-economic status, institutional choice, financial aid package, and parents' education relate to the experiences within the Retention Self-Study Framework (Woodard, Mallory, & DeLuca, 2001).Utilizing the Retention Self-Study Framework, the author created a survey that asked students about each of the various characteristics within the four spheres described in the framework. The research was conducted at a large Research-Extensive university in southwest United States of undeclared majors. Utilizing both mixed methods, the research provides a fresh look at issues of retention and those experiences that are related to persistence and suggests implications for practice and future research.
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An intervention towards the improvement of academic performance, success and retention among bachelor of nursing students at a higher education institution in the Western CapeMthimunye, Katlego Dumisani Trevor January 2019 (has links)
Philosophiae Doctor - PhD / Academic success, which is measured by continuous assessment and
examination results, is one of the major goals of higher education. However, Higher Education
institutions worldwide are faced with a challenge on how to improve the academic
performance, success and ultimately the retention of students during their studies.
Aim: The aim of this study was to develop an intervention towards the improvement of
academic performance, success and retention among undergraduate nursing students at a
university in the Western Cape, South Africa.
Methods: A multi-method research approach was employed to meet the study aim and
objectives. The study was conducted in three phases that were guided by the adapted phases of
the Design and Development (D&D) model by Rothman and Thomas (2013). Phase one (Study
1– 4) was the problem analysis and information gathering phase. Phase two was the design and
early development during which designing observational elements and specifying procedural
elements were applied. Phase three (Study 5) was the validation phase.
Results: This thesis comprised of five interdependent studies. Study 1: A systematic review
of literature was conducted encompassing previous literature from 2006 to 2016 regarding the
predictors of academic performance and success among undergraduate nursing students. It was
found that satisfactory academic performance among nursing students is associated with older
age, female gender, English language proficiency, majority ethnic status, pre-admission
academic achievements, selecting nursing as first choice for study, participating in organised
music programmes, active academic engagement, as well as psychological and emotional
factors. Study 2: Undergraduate nursing students’ (n =232) perceptions regarding their
educational environment were explored. This study showed that generally the nursing students
were positive about their educational environment. However, the findings indicated that
enhancements are required to improve the conditions of the educational environment. Study
3: The study explored the challenges experienced by undergraduate nursing students (6 - focus
group discussions) regarding their academic performance and success and the measures
implemented to overcome these challenges. The findings revealed that students’ academic
performance is influenced by the students’ economic background, place of residence,
inadequate theoretical and clinical support and the unfavorable educational environment.
However, the findings also indicated that students employ a surface approach to learning,
maintain a positive attitude and remain academically engaged in response to these challenges.
Study 4: The study explored the challenges experienced by nurse educators (n = 8) regarding
the academic performance, success and retention of undergraduate nursing students and the
measures implemented to overcome these challenges. The findings revealed that students’
academic performance is influenced by poor class attendance, lack of academic readiness,
socioeconomic backgrounds, English language proficiency, structure of the programme, the
educational environment and the working conditions for nurse educators. Study 5: A three
round Delphi study was conducted to validate an intervention towards improving the academic
performance, success and retention among nursing students. The intervention was structured
into eleven categories that emerged from phase 2: (1) Select high quality prospective nursing
students; (2) Provide English language support; (3) Promote class attendance; 4) providing
financial support to deserving students; (5) Provide university residence to undergraduate
nursing students; (6) Encourage family support and involvement; (7) Make the undergraduate
nursing programme student-friendly; (8) Ensure a conducive teaching and learning
environment; (9) Enhance theoretical and clinical support to undergraduate nursing students at
all times; (10) Ensure uniformity and consistency in the process of teaching and learning as
well as; (11) Provide support to nurse educators and clinical supervisors.
Conclusion: The findings of this study have several implications for the education of nursing
students. The developed intervention may help promote better understanding of the academic
performance, success and retention of nursing students.
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Retention of the Experienced NurseBrinegar, Tina Melissa 01 January 2017 (has links)
The nursing profession is facing a potentially devastating shortage of nurses by the year 2020. Contributing to the shortage is the retirement of experienced nurses who are over the age of 45, and an aging baby boomer population. The loss will place a considerable strain on the overloaded health systems. As a result, it is important to identify successful strategies for addressing the problem of experienced nurse retention. Therefore, the purpose of this project was to conduct a systematic review of literature to answer the question of what retention strategies have been used to prevent the loss of the experienced nurse who is approaching retirement age. The systematic review, guided by Benner's theory of novice to expert and Kanter's empowerment theory, included quantitative, qualitative and mixed methods studies published between 2007 and 2017. Studies published in the United States and Canada were 8studies selected for detailed review, were graded using the Joanna Briggs Institute grading criteria. The themes identified in this study included five key indicators: nurse autonomy and empowerment (75%), stress and burnout (62%), workplace engagement (68%), leadership commitment (56%), and training/career development action plans (56%). The key indicators may provide the basis for recommendations for managers and leaders in promoting experienced nurse retention in their work settings. Positive social change is possible when management takes into consideration the value of the key indicators above in experienced nurse retention efforts. By retaining experienced nurses, the nursing profession can promote positive patient outcomes and a mentoring plan for nurses approaching retirement age.
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An analysis of staff turnover in the optometric industry / by Marna SlabbertSlabbert, Marna January 2008 (has links)
Thesis (M.B.A.)--North-West University, Potchefstroom Campus, 2009.
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An analysis of staff turnover in the optometric industry / by Marna SlabbertSlabbert, Marna January 2008 (has links)
Thesis (M.B.A.)--North-West University, Potchefstroom Campus, 2009.
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An analysis of staff turnover in the optometric industry / by Marna SlabbertSlabbert, Marna January 2008 (has links)
Thesis (M.B.A.)--North-West University, Potchefstroom Campus, 2009.
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University Budget Models, Institutional Size, and Student OutcomesBatchelder, James P 01 December 2020 (has links)
The purpose of the non-experimental quantitative research study was to identify if there is a significant difference between the types of budget model an institution utilizes, institutional size, and student enrollment, retention, and graduation rates. This study was to identify if there is significant difference between institutional size and the type budget model utilized.
Member institutions of the American Association of State Colleges and Universities (AASCU) were selected to participate in this study due to their similarities of mission and admissions policy. AASCU institutions share a common mission that focuses on access, innovation, regional support, and inclusion. AASCU institutions are all public regional institutions.
Larger institutions within the study presented significantly higher retention and graduation rates compared to medium size institutions. I used the Carnegie classification of size as institutions that have enrollments less than 3,000 as small, institutions that have enrollments less than 10,000 as medium, and institutions with enrollments greater than 10,000 as large. I study found no significant difference in the types of budget model utilized and the student outcomes related to enrollment, retention, or graduation rates. I did indicate that institutions that utilized a more decentralized budgeting approach had higher enrollment percentages and higher retention and graduation rates than institutions that utilized a centralized budget model. I also did not identify any significant difference in the size of an institution and the type of budget model utilized.
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Peer Counseling/Mentoring and its Impact on the Academic Success and Retention of African American Students at a Predominantly White InstitutionWhite, Eva Maria 04 May 2018 (has links)
The purpose of this study was to examine the peer counseling/mentoring experiences of African American students involved in a formal undergraduate Peer Counseling/Mentoring program at Mississippi State University. This study specifically examined the Peer Counseling/Mentoring experiences of undergraduate African American students at a predominantly White institution to determine if a relationship existed between peer counseling/mentoring, retention and academic performance. The research design for this study was descriptive, correlational and casual comparative. A pilot study was conducted to detect any problems that should be remedied before conducting the actual study. Based on information gathered in the pilot study, no revisions were required for the survey instrument. Participants in the research study completed a three-part survey instrument. Part I of the survey instrument collected demographic and enrollment data with one question pertaining to participants’ utilization of their peer counselor/mentor. Part II, the Racial and Mentoring Experiences Scale, collected data that examined the participants’ peer counseling/mentoring experiences, the factors that contributed to their persistence, the relationship between grade point average and academic performance, and the difference in grade point average of those who did or did not utilize their peer counselor/mentor. Part III of the survey instrument, an open-ended questionnaire, gathered information regarding the participants’ experiences. The survey instrument was completed and returned by 177 African American seniors from Mississippi State University. According to the findings in this study, Peer Counseling/Mentoring programs support the persistence and retention of African American students at predominantly White institutions. A statistically significant difference was found to exist between participants who utilized their Peer Counselor/Mentor and those who did not. The results indicated that those who utilized their Peer Counselor/Mentor had a higher self-reported grade point average than those who did not utilize their Peer Counselor/Mentor. The Peer Counselor/Mentor program provided participants with a peer who understood their challenges, contributed to their persistence and strengthened their confidence and connection to the university cultural/climate. The research revealed that if administrators desire their African American students to graduate at rates on par with their Caucasian counterparts strong consideration should be given to the implementation of Peer Counselor/Mentor programs.
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