Natural Tension Research Articles

A hierarchical mesh film with superhydrophobic and superoleophilic properties for oil and water separation

AbstractBACKGROUND: Solid surfaces possessing both superhydrophobic and superoleophilic properties have attracted great interest for fundamental research and potential application. However, fabrication of the reported surfaces is usually time‐consuming and the wetability of the surfaces could not be achieved to the desired level in rugged environments.RESULTS: A hierarchical stainless steel mesh film comprising structures with three scales of roughness was synthesized by a simple chemical bath deposition method. After being modified with a low surface energy material e.g. Teflon, these films exhibit superhydrophobic and superoleophilic properties. In this study it was demonstrated that the unique properties of the as‐prepared films match well with the requirements for the effective separation of oil and water mixtures.CONCLUSION: It was confirmed that the unique surface wetability of the surface is due to the cooperative effect of the hierarchical structures of the stainless steel mesh films and the natural low surface tension of Teflon. Furthermore, fabrication is simple and economic, and the surface exhibited robust durability even in a rugged environment. Copyright © 2011 Society of Chemical Industry

Quantum charged rigid membrane

The early Dirac proposal to model the electron as a charged membrane is reviewed. A rigidity term, instead of the natural membrane tension, involving linearly the extrinsic curvature of the worldvolume swept out by the membrane is considered in the action modeling the bubble in the presence of an electromagnetic field. We set up this model as a genuine second-order derivative theory by considering a non-trivial boundary term which plays a relevant part in our formulation. The Lagrangian in question is linear in the bubble acceleration and by means of the Ostrogradski–Hamiltonian approach, we observed that the theory comprises the management of both first- and second-class constraints. We thus show that our second-order approach is robust allowing for a proper quantization. We found an effective quantum potential which permits us to compute bounded states for the system. We comment on the possibility of describing brane world universes by invoking this kind of second-order correction terms.

Sampling and Cost-Sharing: Approximation Algorithms for Stochastic Optimization Problems

We consider two- and multistage versions of stochastic combinatorial optimization problems with recourse: in this framework, the instance for the combinatorial optimization problem is drawn from a known probability distribution $\pi$ and is only revealed to the algorithm over two (or multiple) stages. At each stage, on receiving some more information about the instance, the algorithm is allowed to build some partial solution. Since the costs of elements increase with each passing stage, there is a natural tension between waiting for later stages, to gain more information about the instance, and purchasing elements in earlier stages, to take advantages of lower costs. We provide approximation algorithms for stochastic combinatorial optimization problems (such as the Steiner tree problem, the Steiner network problem, and the vertex cover problem) by means of a simple sampling-based algorithm. In every stage, our algorithm samples the probability distribution of the requirements and constructs a partial solution to serve the resulting sample. We show that if one can construct cost-sharing functions associated with the algorithms used to construct these partial solutions, then this strategy results in provable approximation guarantees for the overall stochastic optimization problem. We also extend this approach to provide an approximation algorithm for the stochastic version of the uncapacitated facility location problem, a problem that does not fit into the simpler framework of our main model.

NanoDrop Microvolume Quantitation of Nucleic Acids

Biomolecular assays are continually being developed that use progressively smaller amounts of material, often precluding the use of conventional cuvette-based instruments for nucleic acid quantitation for those that can perform microvolume quantitation. The NanoDrop microvolume sample retention system (Thermo Scientific NanoDrop Products) functions by combining fiber optic technology and natural surface tension properties to capture and retain minute amounts of sample independent of traditional containment apparatus such as cuvettes or capillaries. Furthermore, the system employs shorter path lengths, which result in a broad range of nucleic acid concentration measurements, essentially eliminating the need to perform dilutions. Reducing the volume of sample required for spectroscopic analysis also facilitates the inclusion of additional quality control steps throughout many molecular workflows, increasing efficiency and ultimately leading to greater confidence in downstream results. The need for high-sensitivity fluorescent analysis of limited mass has also emerged with recent experimental advances. Using the same microvolume sample retention technology, fluorescent measurements may be performed with 2 μL of material, allowing fluorescent assays volume requirements to be significantly reduced. Such microreactions of 10 μL or less are now possible using a dedicated microvolume fluorospectrometer. Two microvolume nucleic acid quantitation protocols will be demonstrated that use integrated sample retention systems as practical alternatives to traditional cuvette-based protocols. First, a direct A260 absorbance method using a microvolume spectrophotometer is described. This is followed by a demonstration of a fluorescence-based method that enables reduced-volume fluorescence reactions with a microvolume fluorospectrometer. These novel techniques enable the assessment of nucleic acid concentrations ranging from 1 pg/ μL to 15,000 ng/ μL with minimal consumption of sample.

NanoDrop Microvolume Quantitation of Nucleic Acids

Biomolecular assays are continually being developed that use progressively smaller amounts of material, often precluding the use of conventional cuvette-based instruments for nucleic acid quantitation for those that can perform microvolume quantitation. The NanoDrop microvolume sample retention system (Thermo Scientific NanoDrop Products) functions by combining fiber optic technology and natural surface tension properties to capture and retain minute amounts of sample independent of traditional containment apparatus such as cuvettes or capillaries. Furthermore, the system employs shorter path lengths, which result in a broad range of nucleic acid concentration measurements, essentially eliminating the need to perform dilutions. Reducing the volume of sample required for spectroscopic analysis also facilitates the inclusion of additional quality control steps throughout many molecular workflows, increasing efficiency and ultimately leading to greater confidence in downstream results. The need for high-sensitivity fluorescent analysis of limited mass has also emerged with recent experimental advances. Using the same microvolume sample retention technology, fluorescent measurements may be performed with 2 μL of material, allowing fluorescent assays volume requirements to be significantly reduced. Such microreactions of 10 μL or less are now possible using a dedicated microvolume fluorospectrometer. Two microvolume nucleic acid quantitation protocols will be demonstrated that use integrated sample retention systems as practical alternatives to traditional cuvette-based protocols. First, a direct A260 absorbance method using a microvolume spectrophotometer is described. This is followed by a demonstration of a fluorescence-based method that enables reduced-volume fluorescence reactions with a microvolume fluorospectrometer. These novel techniques enable the assessment of nucleic acid concentrations ranging from 1 pg/ μL to 15,000 ng/ μL with minimal consumption of sample.

Controlled evaporative assembly of polymers from confined solutions

INTRODUCTION In the process of drying, nonvolatile solutes (e.g., polymers, proteins, viruses, bacteria, DNA, microspheres, nanocrystals, carbon nanotubes, etc.) contained within a sessile droplet (i.e., unconstrained liquid) readily assemble into a diverse range of intriguing oneor two-dimensional structures, possessing dimensions of a few hundred submicrons and beyond. It is, in principle, a nonequilibrium process. Two main characteristic patterns are often observed: ‘‘coffee rings’’ and irregular network structures (i.e., Benard cells). A ‘‘coffee ring’’ forms when, in the absence of natural convection and surface tension gradients, the contact line of an evaporating drop becomes pinned. This ensures that liquid evaporating from the edge is replenished by liquid from the interior, so the outward flow carries the nonvolatile dispersions to the edge. The evaporation flux varies spatially, with the highest flux observed at the edge of drop. A subset of the ‘‘coffee rings’’ phenomenon is the formation of concentric rings by repeated microscopic pinning and depinning events (i.e., ‘‘stick-slip’’ motion) of the three-phase contact line, that is, the competition between the friction force and surface tension of the solution. However, random concentric rings are generally formed. Moreover, based on Navier-Stokes equations with a lubrication approximation, the bulk of current theoretical work has centered on understanding a single ring formation using either analytical or numerical methods. By contrast, only a few elegant theoretical studies have focused, either analytically or numerically, on the formation of periodic multirings (i.e., concentric rings) during droplet evaporation on a substrate. A gradient of temperature normal to the droplet surface due to solvent evaporation can induce a Marangoni-Benard convection (i.e., closed-loop circular convection), which results in irregular Benard cells caused by the upward flow of lower, warmer liquid. The spatial variation of evaporative flux and possible convection mean, however, that these nonequilibrium, dissipative structures (e.g., ‘‘coffee rings,’’ cellular structures, fingering instabilities, etc.) are often irregular and stochastically organized.

Mechanical skin thinning-to-thickening transition observed in vivo through 2D high frequency elastography

This study was based on two dimensional (2D) high frequency elastography to describe quantitatively the mechanical behavior of the human dermis in vivo. The study was conducted on the forearm skin and elastographic tests were performed using a combination of two devices: an extensiometer developed for the in vivo study of the mechanical behavior of the skin using uniaxial stretching stress, and a 20 MHz real time sonographer (Dermcup 2020™) for ultrasound skin imaging. The staggered strain estimation algorithm (SSE) was used to produce elastograms. A temporal cumulative technique was applied to improve elastogram quality and to monitor variations in skin strain during stretching. The influence of the natural skin tension controlled by arm bending was studied and distinctive mechanical behavior was observed for low and high mechanical stress levels. In a preliminary analysis, the reproducibility of measurements was assessed by means of coefficient of variation (CV) in 5 selected healthy volunteers.Finally, two hypotheses linked to the geometrical and structural properties of the dermis are proposed to account for the new findings described in this study.

Marine (Aquaculture) Space Allocation: Assessing Transitional Challenges to Local Economies in New Zealand

Local economies of marine areas are largely unexplored in mainline journals, perhaps because they have been considered marginal to the land, too underdeveloped, too specialised or of little importance in the local economy. The relatively recent emphasis on marine spatial planning and the development of offshore power generation has drawn attention to the importance of rights to marine areas. There exist natural tensions between activities that rely on the relatively permanent occupation of marine space (e.g. aquaculture) and those that require that same space for transitional periods of times, perhaps fleetingly, as space ‘to move through’ (e.g. fishing). Different methods of resolving these tensions can produce significant inequities, but less acknowledged is the potential for significant disruption of local economies caught in the contortions of transitions from one legislative regime to another. A recent aquaculture case in New Zealand serves as the basis for an analysis of issues of locality in decision-making when an existing rights holder seeks to renew those rights at a time of transition between one regime and another.

Challenges and Opportunities for Medical Directors in Pathology and Laboratory Medicine: Standardization, Integration, and InnovationThe Authors’ Reply

Because the practice of pathology and laboratory medicine evolves rapidly, laboratory medical directors must constantly introduce new tests and services and continue to provide consistent, reliable results for existing tests. Innovations in laboratory medicine are frequently introduced, and the number of commercial vendors of test kits and reagents increases yearly. These innovations, however, may pose barriers to standardization and integration of laboratories and to interpretation of results generated by different laboratories. We propose a practical framework for medical directors to address the seemingly contradictory challenges of standardizing and integrating while simultaneously providing the flexibility to introduce innovations. We recommend initiating standardization first, then integration, while maintaining flexibility for innovation. As organizations strive to create effective processes to enhance value, the role of the laboratory medical director will become critical in resolving the natural tension between standardization/integration and innovation in laboratory medicine and pathology. The practice of pathology and laboratory medicine has evolved substantially in the past decade. Laboratory medical directors are faced with the dual challenges of introducing new tests and services while simultaneously providing consistent, reliable results for existing tests. Point-of-care testing, noninvasive testing, automation, genetic testing, and telepathology are just a few of the many innovations that have changed the practice of laboratory medicine and pathology. This burgeoning growth includes a similar increase in the number of commercial vendors of test kits and reagents. Although greater purchasing options may offer financial savings, lack of standardization across vendors and practices impedes integration of laboratories and often presents problems for physicians who

Health reform and the immediate needs of rural and remote communities

Health reform and the immediate needs of rural and remote communities

Interpretations of corruption in Intercultural bargaining

There is a fine line in business negotiations between being perceived as corrupt and having proper engagement with the natural tension and excitement of the business bargaining process. Combining literature review and experiential observation we provide a framework that will assist global business managers to more successfully negotiate cross-cultural business transactions. We identify some archetypal underpinnings of bargaining in a business context and question the established perceptions of corruption in intercultural business dealings. We conclude that different cultural systems produce variations of negotiating behaviour that need to be judged with a deeper local knowledge to avoid simply transferring inappropriate labels.

Challenges and Opportunities for Medical Directors in Pathology and Laboratory Medicine

Because the practice of pathology and laboratory medicine evolves rapidly, laboratory medical directors must constantly introduce new tests and services and continue to provide consistent, reliable results for existing tests. Innovations in laboratory medicine are frequently introduced, and the number of commercial vendors of test kits and reagents increases yearly. These innovations, however, may pose barriers to standardization and integration of laboratories and to interpretation of results generated by different laboratories. We propose a practical framework for medical directors to address the seemingly contradictory challenges of standardizing and integrating while simultaneously providing the flexibility to introduce innovations. We recommend initiating standardization first, then integration, while maintaining flexibility for innovation. As organizations strive to create effective processes to enhance value, the role of the laboratory medical director will become critical in resolving the natural tension between standardization/integration and innovation in laboratory medicine and pathology.

Physicians Should Treat Mentally Ill Death Row Inmates, Even if Treatment is Refused

Competency to be executed evaluations are conducted with a clear understanding that no physician-patient relationship exists. Treatment however, is not so neatly re-categorized in large measure because it involves the physician's active provision of the healing arts. A natural tension exists between what practices may be legally permissible and what are ethically acceptable. We present an overview of the existing positions on this matter in the process of framing our argument.

Capital Markets Regulation: How Can Accounting Research Contribute?

In examining the possible contribution that accounting research can play in ensuring effective and efficient regulation of securities markets, two principal opportunities stand out. First, the role of research in informing debate about proposed regulatory intervention (ex ante contribution to regulatory debate). Second, the ability of research to inform analysis as to the effectiveness of previously implemented regulatory changes (ex post contribution to regulatory debate). In the ex ante case, there is a natural tension between the way in which regulatory initiatives often arise quickly and the inevitable passage of time required to fully appreciate the degree to which underlying problems have been correctly characterised and can be framed in a manner suitable for addressing via rigorous analytical and empirical research. It is also impossible to empirically assess the effect of regulatory intervention that has not yet occurred. Finally, if data are simply not available, then research is limited to analytical analysis and prediction. In the ex post case, there is often a natural reluctance to subject regulatory intervention to mandatory analysis, and even when a statutory requirement exists for such analysis and review, the time horizon is often far too short for meaningful analysis. In both the ex ante and ex post cases, what is unavoidable is that regulation can only be legitimately informed by research that is sufficiently rigorous so as to have robust conclusions. Assessing research on these dimensions means that transparency is required so as to allow researchers to engage in meaningful debate about the validity of the conclusions. This inevitably means that research needs to be a partnership between regulatory agencies and academia, and that when research is used to justify regulatory interventions it must be publicly available and subject to robust debate.

Simulating the wrinkling and aging of skin with a multi-layer finite element model

One of the outward signs of the aging process of human skin is the increased appearance of wrinkles on its surface. Clinical studies show that the increased frequency of wrinkles with age may be attributed to changes in the composition of the various layers of skin, leading to a change in mechanical properties. A parameter study was performed on a previously proposed multi-layer finite element model of skin. A region of skin was subject to an in-plane compression, resulting in wrinkling. A number of physical properties of the skin model were changed and the effects these changes had on the size of the subsequent wrinkles were measured. Reducing the moisture content of the stratum corneum by 11% produces wrinkles 25–85% larger. Increasing the dermal collagen fibre density by 67%, results in wrinkles, which are 25–50% larger. A reduction and change in the pre-stress distribution in the skin model, which represents the natural tension and relaxed skin tension lines in real skin, also influences the wrinkle height in a similar manner to real aging skin. Typically, there can be up to a 100% increase in the height of wrinkles as skin ages. This model would be of benefit in the development of cosmetic moisturisers and plastic-surgery techniques to reduce the appearance of aging.

Reconsidering the tension between bureaucracy and professionalism in publicly and privately funded schools

This article sheds new light on the so-called ‘natural tension’ between bureaucracy and professionalism in schools. As it is quite common in the educational field to appoint teachers, it is debatable whether the assumed tension really exists. It seems more reasonable to find hierarchical control within the professional group. This notion forces to discuss the professional bureaucracy antagonism and to examine the interplay between teachers and managers within schools more concretely. The presented findings are based on a recent empiric study that compared the interplay between teachers and middle managers in publicly and privately funded schools.

Computational modeling of reconstructive surgery: The effects of the natural tension on skin wrinkling

A computational model is presented for the simulation of procedures of reconstructive surgery characterized by the excision of a cutaneous defect and the closure and suture of the wound edges. The skin is modeled as a plane membrane with zero flexural stiffness. The membrane undergoes large deformations and is characterized by a Fung type constitutive response in biaxial tension. Skin wrinkling, which is a typical outcome of the surgery in the form of extrusion of the wound edges and dog-ears, is considered through a modification of the elastic potential as originally proposed by Pipkin's Relaxed Energy Density theory [A.C. Pipkin, The relaxed energy density for isotropic elastic membranes, IMA J. Appl. Math. 36 (1986) 85–99; A.C. Pipkin, Relaxed energy density for large deformations of membranes, IMA J. Appl. Math. 52 (1994) 197–308]. The post-buckling analysis of a stretched annular membrane performed by Geminard et al. [Wrinkle formations in axi-symmetrically stretched membranes, Eur. Phys. J. E 15 (2004) 117–126] is used to validate the model under conditions similar to those of the surgery and to discuss the influence of a pre-existing tension in the membrane on the extension of the wrinkled regions. The model is applied to simulate different surgical procedures and investigate the effects of the natural state of the skin and the shape and size of the excisions. The results explain and validate current practice.

Accounting Conservatism and the Efficiency of Debt Contracts

ABSTRACTIn this paper we examine how accounting conservatism affects the efficiency of debt contracting. We develop the statistical and informational properties of accounting reports under varying degrees of conditional and unconditional accounting conservatism, consistent with Basu's [1997] description of differential verifiability standards. Optimal debt covenants and interest rates on debt are derived from a natural tension between debt holders and equity claimants. We show how optimal covenants vary with the degree of conservatism and derive an efficiency metric that depends on the degree of conservatism. We find that accounting conservatism actually decreases the efficiency of debt contracts, contrary to the suggestions of Watts [2003] and contrary to the hypothesis in numerous empirical studies.

Love as Redemption

This research documents the American Dream in two popular biopics: Ray (2004) and Walk the Line (2005). In both films, the American Dream, framed by the ideology of individuality, follows a particular trajectory: Struggle, individual effort, responsibility, and talent lead to material wealth, but the protagonists' immoral behaviors overwhelm them, thus creating a host of professional and personal problems. The relevance of racism and class struggle, long identified as significant barriers to upward mobility, is minimized for a more personal issue, psychological trauma, to explain their moral declines. Both films resolve the natural tensions between the material (individualism) and the moral (brotherhood) by introducing the Hollywood love story as an acceptable narrative for the lead character's redemption. The mythology allows for a more feminine narrative (heterosexual romantic love) as moral resolution, one that avoids the more complicated notions of brotherhood (racial and class equality) as part of the ideological equation.

A Flexible Privacy-Enhanced Location-Based Services System Framework and Practice

Location based services(LBS) are becoming increasingly important to the success and attractiveness of next generation wireless systems. However, a natural tension arises between the need for user privacy and the flexible use of location information. In this paper we present a framework to support privacy enhanced location based services. We classify the services according to several basic criteria and we propose a hierarchical key distribution method to support these services. The key idea behind the system is to hierarchically encrypt location information under different keys, and distribute the appropriate keys only to group members with the necessary permission. Four methods are proposed to deliver hierarchical location information while maintaining privacy. We propose a key tree rebalancing algorithm to maintain the re-keying performance of the group key management. Furthermore, we present a practical LBS system implementation. Hierarchical location information coding offers flexible location information access which enables a rich set of location based services. Our load tests show such a system is highly practical with good efficiency and scalability.