Kinetic Modeling and Numerical Simulation as Tools to Scale Microalgae Cell Membrane Permeabilization by Means of Pulsed Electric Fields (PEF) From Lab to Pilot Plants

Pulsed Electric Fields (PEF) is a promising technology for the gentle and energy efficient disruption of microalgae cells such as Chlorella vulgaris. The technology is based on the exposure of cells to a high voltage electric field, which causes the permeabilization of the cell membrane. Due to the dependency of the effective treatment conditions on the specific design of the treatment chamber, it is difficult to compare data obtained in different chambers or at different scales, e.g., lab or pilot scale. This problem can be overcome by the help of numerical simulation since it enables the accessibility to the local treatment conditions (electric field strength, temperature, flow field) inside a treatment chamber. To date, no kinetic models for the cell membrane permeabilization of microalgae are available what makes it difficult to decide if and in what extent local treatment conditions have an impact on the permeabilization. Therefore, a kinetic model for the perforation of microalgae cells of the species Chlorella vulgaris was developed in the present work. The model describes the fraction of perforated cells as a function of the electric field strength, the temperature and the treatment time by using data which were obtained in a milliliter scale batchwise treatment chamber. Thereafter, the model was implemented in a CFD simulation of a pilot-scale continuous treatment chamber with colinear electrode arrangement. The numerical results were compared to experimental measurements of cell permeabilization in a similar continuous treatment chamber. The predicted values and the experimental data agree reasonably well what demonstrates the validity of the proposed model. Therefore, it can be applied to any possible treatment chamber geometry and can be used as a tool for scaling cell permeabilization of microalgae by means of PEF from lab to pilot scale. The present work provides the first contribution showing the applicability of kinetic modeling and numerical simulation for designing PEF processes for the purpose of biorefining microalgae biomass. This can help to develop new processes and to reduce the costs for the development of new treatment chamber designs.DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli

La función del lenguaje en una situación política.

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Unpacking psychological inequalities in organisations:Psychological capital reconsidered

In this paper, we argue that psychological capital is unequally distributed among people from different social classes, ethnic backgrounds and genders. Confronting the limitations of the current, individualistic perspective on psychological capital, we offer a re-conceptualisation of the construct from a critical, interdisciplinary perspective, placing it at the intersection of sociology and psychology. We discuss the various mechanisms through which social inequalities may cause differential access to psychological capital for members of low- and high-status social groups and show how this differential access to psychological capital results in and exacerbates social inequalities. By doing this, we postulate a recursive theory on psychological capital that both recognises the formative effect of socio-organisational structures on one's psychology and vice versa

INCLEAD:Development of an inclusive leadership measurement tool

In this paper, as preview of an ongoing research manuscript, we aim to provide the field with an inclusive leadership operationalization reflecting a consolidated conceptualization of inclusive leadership. We use the consolidated conceptualization of inclusive leadership developed recently based on the existing knowledge in the literature

About and beyond leading uniqueness and belongingness:A systematic review of inclusive leadership research

The purpose of this systematic review of 107 papers is to address the conceptual confusion about what inclusive leadership (IL) behavior entails and understand the theoretical development of IL. Synthesizing the divergent conceptualizations of inclusive leader behaviors, we propose a multilevel (i.e., employee, team, organizational) model of IL behavior consisting of four dimensions namely, fostering employee's uniqueness (e.g., promoting diversity); strengthening belongingness within a team (e.g., building relationships); showing appreciation (e.g., recognizing efforts and contributions); and supporting organizational efforts (e.g., promoting organizational mission on inclusion). Further, we provide a summary of studied variables as a nomological network in relation to inclusive leadership and an overview of the different theories (e.g., social exchange, intrinsic motivation) supporting the respective relationships and explaining the underlying mechanisms (e.g., reciprocity, motivation). We propose future research to empirically test the multi-level model of IL and examine the predictive value in terms of employee and organizational outcomes

Development of a Continuous Pulsed Electric Field (PEF) Vortex-Flow Chamber for Improved Treatment Homogeneity Based on Hydrodynamic Optimization

Pulsed electric fields (PEF) treatment is an effective process for preservation of liquid products in food and biotechnology at reduced temperatures, by causing electroporation. It may contribute to increase retention of heat-labile constituents with similar or enhanced levels of microbial inactivation, compared to thermal processes. However, especially continuous PEF treatments suffer from inhomogeneous treatment conditions. Typically, electric field intensities are highest at the inner wall of the chamber, where the flow velocity of the treated product is lowest. Therefore, inhomogeneities of the electric field within the treatment chamber and associated inhomogeneous temperature fields emerge. For this reason, a specific treatment chamber was designed to obtain more homogeneous flow properties inside the treatment chamber and to reduce local temperature peaks, therefore increasing treatment homogeneity. This was accomplished by a divided inlet into the chamber, consequently generating a swirling flow (vortex). The influence of inlet angles on treatment homogeneity was studied (final values: radial angle α = 61°; axial angle β = 98°), using computational fluid dynamics (CFD). For the final design, the vorticity, i.e., the intensity of the fluid rotation, was the lowest of the investigated values in the first treatment zone (1002.55 1/s), but could be maintained for the longest distance, therefore providing an increased mixing and most homogeneous treatment conditions. The new design was experimentally compared to a conventional co-linear setup, taking into account inactivation efficacy of Microbacterium lacticum as well as retention of heat-sensitive alkaline phosphatase (ALP). Results showed an increase in M. lacticum inactivation (maximum Δlog of 1.8 at pH 7 and 1.1 at pH 4) by the vortex configuration and more homogeneous treatment conditions, as visible by the simulated temperature fields. Therefore, the new setup can contribute to optimize PEF treatment conditions and to further extend PEF applications to currently challenging products

Staffing effectiveness across countries:An institutional perspective

This study draws on institutional theory to investigate why and how staffing effectiveness varies across countries. Utilising data from multiple sources (Cranfield Network on Comparative Human Resource Management [CRANET], Global Leadership and Organisational Behaviour Effectiveness [GLOBE], World Economic Forum [WEF], Transparency International, Tightness-Looseness Index), it covers 2,918 organisations in 11 countries. Extending earlier research on comparative staffing that focuses on cultural or regulatory differences separately, our findings show that companies in different countries implement staffing practices in line with their normative (i.e., cultural), regulatory, and cognitive institutions. A second key finding shows that institutionally embedded staffing practices are associated with organisational turnover, thus challenging dominant universalist perspectives on staffing effectiveness. Finally, we shed light on a central yet understudied boundary condition of contextual perspectives on staffing by identifying the strength of institutional pressures (i.e., societal tightness-looseness) as a moderator of the relationships between national institutions, staffing, and turnover

Roomies for Life?:An Assessment of How Staying with a Local Facilitates Refugee Integration

In light of failing integration policies and practices, we provide a qualitative evaluation of a social innovation that aims to facilitate integration by providing refugees an opportunity to reside temporarily with locals. Our analysis of the experiences shared by refugee guests and local hosts provides insight on the theory and practice of refugee integration in three ways: we (1) inform research and policy on the effectiveness of staying with a local as a means for integrating refugees, (2) unpack the mechanisms through which staying with a local facilitates refugee integration, and (3) theoretically enrich the literature on indicators of integration