Improved Online Algorithms for Knapsack and GAP in the Random Order Model

The knapsack problem is one of the classical problems in combinatorial optimization: Given a set of items, each specified by its size and profit, the goal is to find a maximum profit packing into a knapsack of bounded capacity. In the online setting, items are revealed one by one and the decision, if the current item is packed or discarded forever, must be done immediately and irrevocably upon arrival. We study the online variant in the random order model where the input sequence is a uniform random permutation of the item set. We develop a randomized (1/6.65)-competitive algorithm for this problem, outperforming the current best algorithm of competitive ratio 1/8.06 [Kesselheim et al. SIAM J. Comp. 47(5)]. Our algorithm is based on two new insights: We introduce a novel algorithmic approach that employs two given algorithms, optimized for restricted item classes, sequentially on the input sequence. In addition, we study and exploit the relationship of the knapsack problem to the 2-secretary problem. The generalized assignment problem (GAP) includes, besides the knapsack problem, several important problems related to scheduling and matching. We show that in the same online setting, applying the proposed sequential approach yields a (1/6.99)-competitive randomized algorithm for GAP. Again, our proposed algorithm outperforms the current best result of competitive ratio 1/8.06 [Kesselheim et al. SIAM J. Comp. 47(5)]

Accountability and the Cooperative Extension Service: An Emerging Role for Rural Sociology

Presidential address of the Southern Rural Sociological Association, Orlando, Florida, February 1986

Gaining a competitive advantage : employees' perceptions on the role of leadership and talent management factors in a small company in South Africa

Purpose – This research paper falls within the interpretive research philosophy and considers talent management within the field of competitive advantage. It aims to explore the organisation members’ perceptions of talent, talent management, the factors perceived to facilitate competitive advantage and the role of leadership in the facilitation of talent management. It attempts to achieve a greater understanding of talent management as practically applied by organisations. Design/Methodology – A qualitative research approach in collecting and analysing data was implemented for this particular research study to address the research problem. The research design consists of a qualitative case study of one organisation. The organisation was purposively selected due to its superior performance in its particular industry. The data was collected by using in-depth interviews and observation and analysed using qualitative content analysis. Organisational documents supplemented the data collection process. Rationale – Current talent management literature shows a lack of understanding of talent and the role leadership plays in talent management. A number of authors have called for research which focuses on the perspectives of all stakeholders, especially at the individual level. It was also suggested that greater focus is allocated to small to medium enterprises, as multi-national corporations dominated the current literature. This research paper has the potential to increase levels of understanding at both organisation and individual level. This study examined TM from a range of perspectives, focused on a smaller organisation and is one of the few qualitative studies in the world within a developing country—research that is lacking in the literature. Findings – Participants held different views on talent and talent management, supporting the lack of consensus on these topics and the lack of a standardised understanding. The findings highlight that talent management was mostly perceived to involve the correct positioning of people within the organisation and that talent involved skills, knowledge and abilities to perform their roles well. Organisational structure, processes, and the lack of leadership ability were perceived as the dominant factors affecting the effective implementation of talent management practices. Talent management was perceived as important by the middle and lower-level participants of the study and was perceived as not important by higher-level participants—a contrasting finding due to the fact that the higher-level candidates felt that it was important to retain staff, understood the consequences of staff loss and that it was difficult to replace talent. Theoretical and managerial implications – The findings correspond with previous studies that the understanding of talent management is still lacking and thus potentially jeopardizes shaping a competitive advantage. The leadership cadre at the case organisation failed to see the importance of talent management and failed to link talent management to competitive advantage and ultimately failed to strategise potential talent management practices and effective talent management implementation. The modern business environment is changing and the realisation that talent management is of crucial importance to sustained competitive advantage is becoming evident. Limitations – The main source of error was a potential bias of results and a lack of rigorous data analysis, which was overcome by attending to the reliability of the research. Future research – There is potential for further empirical research to be conducted in other industries while maintaining focus on smaller businesses. The focus must also be maintained on the perspectives of all stakeholders in organisations.Business ManagementM. Com

Unterrepräsentation von Frauen durch Geschlechtsstereotype?: Verknüpfung von Stereotypenbedrohung, Zugehörigkeitsgefühl und Erwartung-Wert-Modell in der Internationalen PhysikOlympiade

Die vorliegende Arbeit untersucht die Verknüpfung von Stereotypenbedrohung, Zugehörigkeitsgefühl und Erwartung-Wert-Modell als Wirkkette, die eine Unterrepräsentation von jungen Frauen im Auswahlwettbewerb zur Internationalen PhysikOlympiade begünstigt

Non-equilibrium universality: slow drives, measurements and dephasing

The behavior of quantum systems can be influenced by factors such as unitary evolution, measurements or decoherence. For large composite systems, these mechanisms can give rise to collective phenomena like phase transitions and universality. One example are quantum phase transitions in the ground states of a Hamiltonian. Close to the transition scale invariant behavior emerges, characterized by a set of universal critical exponents. If the system is driven in the vicinity of the transition, the drive scale can lead to a breakdown of the equilibrium scaling behavior. Nevertheless, the breakdown inherits universal properties and gives access to the leading critical exponents (Kibble-Zurek mechanism). However, the whole hierarchy of critical exponents, relevant and irrelevant, is accessible by a slow drive. We establish this generalized mechanism and its observable consequences at the level of elementary, but experimentally relevant, spin and fermion models. We construct drives that turn equilibrium irrelevant couplings into relevant drive couplings with an observable scaling in the excitation density. Criticality and universality also arise from competing unitary evolution and measurements, allowing for measurement-induced transitions. An example are (free) fermion models featuring a transition between an extended `critical' phase and a `pinned', weakly entangled phase. We investigate the role of dephasing/imperfect measurements onto the transition based on (i) numerical approaches (stochastic quantum trajectories), (ii) an effective bosonic replica field theory, and (iii) a perturbative treatment of the fermion dynamics. On the one hand, weak dephasing leaves the `critical' phase and measurement-induced transition in tact. On the other hand, we observe the emergence of a new, temperature-like scale for strong dephasing and weak measurements, enabled by the interplay of all three mechanisms. Despite the presence of the finite scale, observables like density-dependent correlations still feature scale invariant behavior. Paired with a perturbative treatment for strong dephasing, this behavior hints at a diffusion-like dynamics on the diagonal of the density matrix in the occupation number basis

Semi-Quantitative Assessment on Winyah Bay\u27s Microplastic Contamination Levels

Although there is much concern globally regarding microplastic contamination in aquatic environments, there is little documentation on microplastic contamination concentrations within South Carolina inland waters and coastal areas. Specifically, Winyah Bay, SC should be of high priority for microplastic contamination evaluations as it is the third largest drainage basin (47,060 km2) and the second largest (157 km2) estuarine system on the east coast of the United States. Today, the general influencing physical factors on microplastic transport are mostly known by the scientific community, however, transport and deposition patterns of microplastics heavily vary by location depending on various physical, chemical, and ecological factors. We tested several different microplastic extraction techniques for Winyah Bay’s sample type and we advanced the methodology to be more efficient. Bottle and grab samples were taken from surface waters and surface sediment, respectively, within Winyah Bay and its associated rivers. Microplastics were extracted from water samples through plankton nets and sieves with hydrogen peroxide for organic matter digestion as needed. We found that filtering water samples through a sieve reduced processing contamination in comparison to filtering through a plankton net. Additionally, we found that extracting microplastics from muddy, thus strongly cohesive sediment samples, was more easily and efficiently accomplished using highly volatile kerosene instead of the commonly used canola oil of higher viscosity. The methodological development of extracting microplastics from these cohesive sediments was so time consuming, such that, no microplastic abundance data from sediments were produced from this study. The average (1.64 particles/L for 2016a, 6.24 particles/L for 2016b, and 0.31 particles/L for 2017; \u3e63 µm, 28-50% particle recovery rate) is comparable to other microplastic abundances across the surface waters (~0.3 m) of the coastal eastern United States (i.e., Georgia: 2 particles/L and some Florida sites: 1-5 particles/L). Oppositely, the average is not as comparable to other sites of the coastal eastern United States (i.e., other Florida sites: 6-20 particles/L and Chesapeake Bay: 1-560 g/km2). Additionally, microplastic fibers made up 90% of the total microplastics collected from surface water samples in this study which is comparable to the domination of fibers also found in Georgia and Florida studies. This study adds to the demonstration that there is a consistent challenge in microplastic literature to compare between studies as each study uses different methods. Our data suggests that microplastic abundances in Winyah Bay, SC are influenced by precipitation (r = .411, p = .030) and tides (i.e., salinity (r = .402, p = .034), density (r = .422, p = .025), and tidal range (.400, p = .035))

Physical aging in glassy mixed matrix membranes; tuning particle interaction for mechanically robust nanocomposite films

Despite the exceptional separation performance of modern glassy mixed matrix membranes, these materials are not being utilized to improve the performance of existing membrane technologies. Nano-sized additives can greatly enhance separation performance, and have recently been used to overcome age-related performance loss of high performance MMMs. However nano-additives also compromise the structural integrity of films and little is known on how physical aging affects their mechanical properties over time. A solution for both physical aging and mechanical instability is required before these high performance materials can be utilised in industrial membrane applications. Here, we examine physical aging in mixed matrix membranes through mechanical properties and gas permeation experiments using three glassy polymers, Matrimid® 5218, poly-1-trimethylsilyl-1-propyne (PTMSP), and a Polymer of Intrinsic Microporosity (PIM-1); and a range of nano-scale additives previously shown to enhance gas separation performance. We find polymer-additive interactions strongly influence local physical aging and play a key role in determining the overall material properties of glassy nanocomposite films. Strong interface interactions can slow physical aging, and may not correlate to reinforced or age-stable films. Whereas traditionally ‘incompatible’ nanocomposites exhibit mechanical properties that can improve over time and even outperform their native polymers. Tuning polymer-additive interactions is vital to achieving the physical aging, mechanical stability, and permselectivity requirements of advanced mixed matrix membrane technologies and reducing the enormous global energy cost of separation processes

Genomic Evolution of Glioblastoma

Understanding how tumors evolve and drive uncontrolled cellular growth may lead to better prognosis and therapy for individuals suffering from cancer. A key to understanding the paths of progression are to develop computational and experimental methods to dissect clonal heterogeneity and statistically model evolutionary routes. This thesis contains results from analysis of genomic data using computational methods that integrate diverse next generation sequencing data and evolutionary concepts to model tumor evolution and delineate likely routes of genomic alterations. First, I introduce some background and present studies into how tumor genomic sequencing tells us about tumor evolution. This will encompass some of the principles and practices related to tumor heterogeneity within the field of computional biology. Second, I will present a study of longitudinal sampling in Glioblastoma (GBM) in cohort of 114 individuals pre- and post-treatment. We will see how genomic alterations were dissected to uncover a diverse and largely unexpected landscape of recurrence. This details major observations that the recurrent tumor is not likely seeded by the primary lesion. Second, to dissect heterogeneity from clonal evolution, multiple biopsies will be added to extend our longitudinal GBM cohort. This new data will introduce analyses to explicate inter and intra-tumor heterogeneity of GBM. Specifically, we identify a metric of intratumor heterogeneity able to identify multisector biopsies and propose a model of tumor growth in multiple GBM. These results will relate to clinical outcome and are in agreement with previously established hypotheses in truncal mutation targeting. Fourth, I will introduce new models of clonal growth applicable to 2 patient biopsies and then fit these to our GBM cohort. Simulations are used to verify models and a brief proof is presented

Light responsive membranes for gas separation

Recent developments in the field of coordinated porous materials (including metal organic frameworks and zeolitic imidazolate frameworks) have demonstrated that it is possible to tailor CO2 sorbents that respond dynamically to illumination with UV and/or broadband light, such that they cyclically adsorb and desorb CO2 according to the illumination state. This has been achieved via several routes, including through the use of light-responsive ligands, light-responsive guest molecules located within the pores, and via adsorption of a light-responsive dye. Since the use of these materials as light-responsive sorbents is challenging (due to engineering constraints in providing unhindered gas and light access to as much of the sorbent as possible), it is highly desirable to incorporate them into thin polymeric membranes to create mixed-matrix membranes with light responsive properties. This could lead to membranes with switchable separation characteristics, or other desirable properties such as some form of self-cleaning or self-regeneration after pore blocking. This presentation will unveil the recent developments in our lab as we develop these novel mixed-matrix membrane materials, including an overview of the light-responsive porous materials we have synthesised and characterised, the design and performance of our newest illuminated test cells for both flat sheet and hollow-fibre membranes (using a unique in-situ LED lighting arrangement to provide maximum illumination and simplify gas sealing)

One Person, One Vote, 435 Seats: Interstate Malapportionment and Constitutional Requirements Is Our Constitutional Order Broken - Structural and Doctrinal Questions in Constitutional Law: Gerrymandering, Congressional Representation, and Trust in the Political System

Beginning in the 1960s and 1970s, the Supreme Court began to establish and enforce a constitutional requirement for the apportionment of legislative districts at the national, state, and local levels. This requirement, the “one person, one vote” principle, has become a benchmark of the constitutional jurisprudence as well as a conceptualization of the fundamental democratic norm of political equality. Since these early cases, apportionment plans that violate this constitutional requirementeven with levels of intrastate malapportionment of less than 1%have been held to be unconstitutional. Yet, there is a much more severe form of malapportionment that continues today and will worsen with the reapportionment of the United States House of Representatives after the 2010 Census: interstate malapportionment. The levels of interstate malapportionment are over 9,000% greater than the levels of intrastate malapportionment already found unconstitutional. This Article explores the causes and possible solutions to this problem. It concludes that the constitutional requirement of “one person, one vote” can only be constitutionally addressedto any considerable degreeby reconsidering the twentieth century statutory requirement that fixed the size of the House at 435 seats