A ��place n play�� modular pump for portable microfluidic applications

This paper presents an easy-to-use, power-free, and modular pump for portable microfluidic applications. The pump module is a degassed particle desorption polydimethylsiloxane (PDMS) slab with an integrated mesh-shaped chamber, which can be attached on the outlet port of microfluidic device to absorb the air in the microfluidic system and then to create a negative pressure for driving fluid. Different from the existing monolithic degassed PDMS pumps that are generally restricted to limited pumping capacity and are only compatible with PDMS-based microfluidic devices, this pump can offer various possible configures of pumping power by varying the geometries of the pump or by combining different pump modules and can also be employed in any material microfluidic devices. The key advantage of this pump is that its operation only requires the user to place the degassed PDMS slab on the outlet ports of microfluidic devices. To help design pumps with a suitable pumping performance, the effect of pump module geometry on its pumping capacity is also investigated. The results indicate that the performance of the degassed PDMS pump is strongly dependent on the surface area of the pump chamber, the exposure area and the volume of the PDMS pump slab. In addition, the initial volume of air in the closed microfluidic system and the cross-linking degree of PDMS also affect the performance of the degassed PDMS pump. Finally, we demonstrated the utility of this modular pumping method by applying it to a glass-based microfluidic device and a PDMS-based protein crystallization microfluidic device.     

Vertical microbubble column–A photonic lab-on-chip for cultivation and online analysis of yeast cell cultures

This paper presents a vertically positioned microfluidic system made of poly(dimethylsiloxane) (PDMS) and glass, which can be applied as a microbubble column (μBC) for biotechnological screening in suspension. In this μBC, microbubbles are produced in a cultivation chamber through an integrated nozzle structure. Thus, homogeneous suspension of biomass is achieved in the cultivation chamber without requiring additional mixing elements. Moreover, blockage due to produced carbon dioxide by the microorganisms—a problem predominant in common, horizontally positioned microbioreactors (MBRs)—is avoided, as the gas bubbles are released by buoyancy at the upper part of the microsystem. The patterned PDMS layer is based on an optimized two-lithographic process. Since the naturally hydrophobic PDMS causes problems for the sufficient production of microbubbles, a method based on polyelectrolyte multilayers is applied in order to allow continuous hydrophilization of the already bonded PDMS-glass-system. The μBC comprises various microelements, including stabilization of temperature, control of continuous bubble formation, and two optical configurations for measurement of optical density with two different sensitivities. In addition, the simple and robust application and handling of the μBC is achieved via a custom-made modular plug-in adapter. To validate the scalability from laboratory scale to microscale, and thus to demonstrate the successful application of the μBC as a screening instrument, a batch cultivation of Saccharomyces cerevisiae is performed in the μBC and compared to shake flask cultivation. Monitoring of the biomass growth in the μBC with the integrated online analytics resulted in a specific growth rate of 0.32 h⁻¹, which is almost identical to the one achieved in the shake flask cultivation (0.31 h⁻¹). Therefore, the validity of the μBC as an alternative screening tool compared to other conventional laboratory scale systems in bioprocess development is proven. In addition, vertically positioned microbioreactors show high potential in comparison to conventional screening tools, since they allow for high density of integrated online analytics and therefore minimize time and cost for screening and guarantee improved control and analysis of cultivation parameters.     

The survival analysis on newcomers＇ turnover： A perspective of social networks

本研究以社会网络为视角,探讨影响企业新进员工跳槽的社会网络机制。选取2008年参加工作的毕业生为对象进行生存分析发现,入职前后的社会网络强度会显著提高新进员工的跳槽可能,而扩大入职后的网络规模则会延长新进员工的工作持续时间。交互效应的检验表明,入职前网络强度与入职后网络规模和强度的交互效应均会对工作持续时间产生积极影响。本研究最后提出了有针对性的建议。     

Organizational knowledge,learning and memory – a perspective of an immune system

Organizational knowledge, learning and memory have been popular topics for both academic research and practical applications over the past 20 years. But until now, these issues have been discussed independently and in a fragmented way. It is asserted that these concepts are interrelated and should be considered as a part of a system. Here, the perspective of the immune system is employed to integrate the issues of organizational knowledge, learning and memory into a framework and to explain their interrelationships. The perspective developed in this paper pioneers a micro-view to integrate and explain organizational phenomena.     

A term function–aware keyword citation network method for science mapping analysis

Various keyword network methods are used to map scientific fields, but few studies have considered the semantic roles of keywords in such networks. This study proposes a term function–aware keyword citation network to fill this research limitation. Specifically, we first used a term function identification method to identify research questions and methods from scientific articles. Then, we constructed a question-method term citation network to represent the correlation structure of keywords. Next, we explored the topology characteristics, question-method bipartite network, and knowledge community structure of the generated network to validate its superiority in science mapping analysis. A dataset of 299,567 conference proceedings collected from the Association for Computing Machinery (ACM) digital library is used to evaluate the effectiveness of our methods. The results show that the term function identification model based on Bidirectional Encoder Representations from Transformers (BERT) achieves a score of 0.90 F1. And the question-method term citation network outperforms existing keyword citation methods in revealing association patterns between scientific knowledge and improving the interpretability of the knowledge structure of the computing field. We believe that our work expands the methodology of keyword citation network and science mapping analysis and provides guidance for considering the term function in various scenarios.     

Licensing standard-essential patents in the IoT – A value chain perspective on the markets for technology

Innovative industries need efficient markets for technology (MFTs). One determinant of MFT efficiency neglected until now is licensing level—that is, the level in the value chain where patents are licensed. Patents may be licensed upstream, to firms that put the patented knowledge into practice. I refer to this as integrated licensing. Alternatively, patents may be licensed further downstream in the value chain, in particular to makers of final devices. I call this bifurcated licensing since it separates intellectual property rights from the technical knowledge they cover. I study the licensing level of essential patents on communication standards such as LTE and Wi-Fi in relation to the Internet of Things (IoT). The choice of licensing level in this context is currently a hotly debated topic. To show how bifurcated licensing affects MFT efficiency, I present empirical evidence from a qualitative study comprising interviews with 30 individuals from 22 diverse firms, focusing on startups. IoT device makers clearly find the uncertainty regarding infringement, patent validity, and the licensing process hinders efficient licensing, which is compounded by the large number of IoT device makers and, for SMEs and startups, by resource constraints. As a theory contribution, I show that a patent's licensing level need not correspond with the implementation level of the patented knowledge—in other words, licensing may be bifurcated rather than integrated. I develop a model of how licensing level affects MFT efficiency. Implications for practice are that device-level licensing of standard-essential patents (SEPs), if broadly implemented, would have a negative effect on innovation and entrepreneurship in the IoT. Policymakers should ensure that SEP licensing is simplified.     

Incentive or disincentive for research data disclosure? A large-scale empirical analysis and implications for open science policy

When researchers disclose their original data, they can enhance the visibility of their research works and gain more academic credits (credit effect). By contrast, doing so may accelerate the knowledge replacement process, which dissipates the academic credit that their research works may have received (competition effect). In this study, we examine whether and the extent to which scientists gain academic credit for their research works by publicly disclosing their data. Our review of various literature hypothesizes that data-disclosing research gains more academic credit than non-data-disclosing research in the short term. However, this difference gradually disappears and reverses as the competition effect emerges. This pattern is expected to systematically differ depending on the academic reputation of the journals where the data-disclosing research is published. We empirically test the derived hypotheses by analyzing the metadata of over 310,000 Web of Science Core Collection (WoS CC)-indexed journal articles published in 2010. Our analysis supports both hypotheses. The present study contributes to the on-going policy discussion about the need for institutional measures to promote disclosure of research data by scientists.     

Polyester μ-assay chip for stem cell studies

The application of microfluidic technologies to stem cell research is of great interest to biologists and bioengineers. This is chiefly due to the intricate ability to control the cellular environment, the reduction of reagent volume, experimentation time and cost, and the high-throughput screening capabilities of microscale devices. Despite this importance, a simple-to-use microfluidic platform for studying the effects of growth factors on stem cell differentiation has not yet emerged. With this consideration, we have designed and characterized a microfluidic device that is easy to fabricate and operate, yet contains several functional elements. Our device is a simple polyester-based microfluidic chip capable of simultaneously screening multiple independent stem cell culture conditions. Generated by laser ablation and stacking of multiple layers of polyester film, this device integrates a 10 × 10 microwell array for cell culture with a continuous perfusion system and a non-linear concentration gradient generator. We performed numerical calculations to predict the gradient formation and calculate the shear stress acting on the cells inside the device. The device operation was validated by culturing murine embryonic stem cells inside the microwells for 5 days. Furthermore, we showed the ability to maintain the pluripotency of stem cell aggregates in response to concentrations of leukemia inhibitory factor ranging from 0 to ∼1000 U/ml. Given its simplicity, fast manufacturing method, scalability, and the cell-compatible nature of the device, it may be a useful platform for long-term stem cell culture and studies.     

To be or not to be franchised? A knowledge-based perspective

This paper investigates the rationale for choosing franchising rather than independent activity, arguing that this choice may be motivated by knowledge and competence considerations. We consider the franchise chain as a specific learning organizational form and explore whether this structure handles knowledge and builds competences according to an idiosyncratic pattern. Concretely, we empirically identify differences in the architecture of competences of franchised vs independent shops in the car maintenance industry in France, and analyse some causes for those differences. Thanks to in depth interviews coupled with lexical and quantitative analyses we find that franchised shops do master specific competences. However, the distinctive competences held by franchisees do not necessarily reflect franchisors’ knowledge, and are not exclusively the consequences of a shared identity in the franchise chain. We conclude that the development of franchise cannot be explained by competence-related arguments only, knowledge and competences being managed in distinctive ways within different franchising networks.     

L∞-gain analysis for positive singular time-delay systems

This paper is devoted to the characterization of L_∞-gain for positive singular systems with time-varying delays. First, we introduce an augmented system to replace the original system in order to analyze the positivity of singular systems with time-varying delays. By investigating the monotonicity of state trajectory, the L_∞-gain for singular system with constant delays is characterized. Then, by comparing the trajectories of time-varying delay system and constant delay case, we finally propose the L_∞-gain for singular system with time-varying delays. It is shown that the L_∞-gain of positive singular systems is independent of the magnitude of delays.     

New mechanism for neural stem cell maintenance in early embryos

Teaming up with co-workers from Japan, UK and US,CAS biochemists have revealed a novel mechanism for main-taining neural stem cells in early     

A decomposition analysis on convecting–radiating rectangular plate fins for variable thermal conductivity and heat transfer coefficient

The present study concentrates to make a complete thermal analysis on a rectangular fin with its primary surface by taking into consideration of radiation heat exchange with the surrounding along with the convective mode of heat transfer. The one side of the primary surface is heated by a fluid with high temperature which may be required to dissipate heat quickly by a fin array system. To analyze an actual case study, the thermal conductivity of the fin material and convective heat transfer coefficient over the surface are treated as a variable and they are as a function of the local fin surface temperature. With the aforementioned condition, the energy equations for both the fin and primary surface become nonlinear. The decomposition method is suggested to solve these highly nonlinear equations to obtain a closed form temperature distribution. The result of temperature distribution determined by the present analysis is compared with that of the numerical values. With the adaptation of the simplified case, the present method is also compared with the exactly closed form results. From both of these comparisons, an exact matching of results is found. The fin performances, namely, fin efficiency, surface efficiency and augmentation factor are evaluated for a wide range of thermogeometric parameters.     

Unfolding the popularity of video conferencing apps – A privacy calculus perspective

Video conferencing (VC) applications (apps) have surged in popularity as an alternative to face-to-face communications. Although VC apps offer myriad benefits, it has caught much media attention owing to concerns of privacy infringements. This study examines the key determinants of professionals’ attitude and intentions to use VC apps in the backdrop of this conflicting duality. A conceptual research model is proposed based on theoretical foundations of privacy calculus and extended with conceptualizations of mobile users’ information privacy concerns (MUIPC), trust, technicality, ubiquity, as well as theoretical underpinnings of social presence theory. Structural equation modeling is used to empirically test the model using data collected from 484 professionals. The study offers insights regarding the trade-offs that professionals are willing to make in the face of information privacy concerns associated with VC apps. Based on the findings, the study emphasizes the promotion of privacy protection at the organizational level, control mechanisms that motivate employees to actively engage in privacy protection behavior, and a multi-faceted approach for data transparency within the VC app platforms.     

Development of a magnetic immunosorbent for on-chip preconcentration of amyloid �� isoforms: Representatives of Alzheimer��s disease biomarkers

Determination of amyloid β (Aβ) isoforms and in particular the proportion of the Aβ 1-42 isoform in cerebrospinal fluid (CSF) of patients suspected of Alzheimer’s disease might help in early diagnosis and treatment of that illness. Due to the low concentration of Aβ peptides in biological fluids, a preconcentration step prior to the detection step is often necessary. This study utilized on-chip immunoprecipitation, known as micro-immunoprecipitation (μIP). The technique uses an immunosorbent (IS) consisting of magnetic beads coated with specific anti-Aβ antibodies organized into an affinity microcolumn by a magnetic field. Our goal was to thoroughly describe the critical steps in developing the IS, such as selecting the proper beads and anti-Aβ antibodies, as well as optimizing the immobilization technique and μIP protocol. The latter includes selecting optimal elution conditions. Furthermore, we demonstrate the efficiency of anti-Aβ IS for μIP and specific capture of 5 Aβ peptides under optimized conditions using various subsequent analytical methods, including matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), capillary electrophoresis, microchip electrophoresis, and immunoblotting. Synthetic Aβ peptides samples prepared in buffer and spiked in human CSF were analyzed. Finally, on-chip immunoprecipitation of Aβ peptides in human CSF sample was performed.     

Finite-time analysis and H∞ control for switched stochastic systems

This paper is concerned with the finite-time stability, boundedness and H_∞ control problems for a class of switched stochastic systems. Using the average dwell time method and the multiple Lyapunov-like function technique, some sufficient conditions are proposed to guarantee the finite-time properties for the switched stochastic systems in the form of matrix inequalities. Also, a state feedback controller for the finite-time H_∞ control problem is obtained. An example is employed to verify the effectiveness of the proposed method.     

A recipe for growing Escherian crystals

Architectural control of nanoparticles with well- defined shapes and the alignment of nanobuilding blocks into ordered superstructures have become the key issues in materials chemistry and nanotechnology since recent years, and copper monosulfide, as one …