Nematic DNA Thermotropic Liquid Crystals with Photoresponsive Mechanical Properties

Over the last decades, water‐based lyotropic liquid crystals of nucleic acids have been extensively investigated because of their important role in biology. Alongside, solvent‐free thermotropic liquid crystals (TLCs) from DNA are gaining great interest, owing to their relevance to DNA‐inspired optoelectronic applications. Up to now, however, only the smectic phase of DNA TLCs has been reported. The development of new mesophases including nematic, hexagonal, and cubic structures for DNA TLCs remains a significant challenge, which thus limits their technological applications considerably. In this work, a new type of DNA TLC that is formed by electrostatic complexation of anionic oligonucleotides and cationic surfactants containing an azobenzene (AZO) moiety is demonstrated. DNA–AZO complexes form a stable nematic mesophase over a temperature range from ?7 to 110 °C and retain double‐stranded DNA structure at ambient temperature. Photoisomerization of the AZO moieties from the E‐ to the Z‐ form alters the stiffness of the DNA–AZO hybrid materials opening a pathway toward the development of DNA TLCs as stimuli‐responsive biomaterials.     

3D‐based hp‐adaptive first‐order shell finite element for modelling and analysis of complex structures—Part 1: The model and the approximation

The paper presents a 3D‐based adaptive first‐order shell finite element to be applied to hierarchical modelling and adaptive analysis of complex structures. The main feature of the element is that it is equipped with 3D degrees of freedom, while its mechanical model corresponds to classical first‐order shell theory. Other useful features of the element are its modelling and adaptive capabilities. The element is assigned to hierarchical modelling and hpq‐adaptive analysis of shell parts of complex structures consisting of solid, thick‐ and thin‐shell parts, as well as of transition zones, where h, p and q denote the mesh density parameter and the longitudinal and transverse orders of approximation, respectively. The proposed hp‐adaptive first‐order shell element can be joined with 3D‐based hpq‐adaptive hierarchical shell elements or 3D hpp‐adaptive solid elements by means of the family of 3D‐based hpq/hp‐ or hpp/hp‐adaptive transition elements. The main objective of the first part of our research, presented in this paper, is to provide non‐standard information on the original parts of the element algorithm. In order to do that, we present the definition of shape functions necessary for p‐adaptivity, as well as the procedure for imposing constraints corresponding to the lack of elongation of the straight lines perpendicular to the shell mid‐surface, which is the procedure necessary for q‐adaptivity. The 3D version of constrained approximation presented next is the basis for h‐adaptivity of the element. The second part of our research, devoted to methodology and results of the numerical research on application of the element to various plate and shell problems, are described in the second part of this paper. Copyright © 2006 John Wiley & Sons, Ltd.     

Microbial quality of hemodialysis water,a survey of six centers in Lagos,Nigeria

Patients with end‐stage kidney disease (ESRD) on maintenance hemodialysis (HD) are usually exposed to large volumes of dialysate, which is separated from patients' blood only by thin membrane of dialyzer. It is therefore essential to frequently monitor the quality of HD water to ensure that it meets the recommended standards. The objective of this study was to evaluate the microbial quality of HD water in Lagos, Nigeria. Four sets of pre‐ and post‐treatment water samples, 20 mL each, were collected from six HD centers in Lagos and tested for microbial contamination using the molten Tryptic soy agar in accordance with Association for Advancement of Medical Instrumentation (AAMI) and European Best Practice Guidelines (EBPG). Pyrogen tests were also conducted on pre‐ and post‐treatment samples using standard technique. Information on water treatment modalities, maintenance practices and quality control measures in each center were obtained using a questionnaire. All centers use treated water for HD purpose. None of the HD centers met EBPG/AAMI guidelines for microbial contaminants as the mean levels of Escherichia coli in both feed and treated water were 441.7 ± 87.90 and 168.5 ± 64.03, respectively. E. coli was the commonest organism isolated in both feed and treated water in all the centers. HD water quality is still a neglected problem in our environment and more efforts are required to ensure good water quality for HD purpose.     

Gate Dielectrics for Organic Field‐Effect Transistors: New Opportunities for Organic Electronics

In this contribution we review the motivations for, and recent advances in, new gate dielectric materials for incorporation into organic thin‐film transistors (OTFTs) for organic electronics. After a general introduction to OTFT materials, operating principles, and processing requirements for optimizing low‐cost organic electronics, this review focuses on three classes of OTFT‐compatible dielectrics: i) inorganic (high‐k) materials; ii) polymeric materials; and iii) self‐assembled mono‐ and/multilayer materials. The principal goals in this active research area are tunable and reduced OTFT operating voltages, leading to decreased device power consumption while providing excellent dielectric/insulator properties and efficient low‐cost solution‐phase processing characteristics.     

Carbon Nanotubes for Cold Electron Sources

Technological advances in the field of microelectronic fabrication techniques have triggered a great interest in vacuum microelectronics. In contrast to solid‐state microelectronics, which entails scattering‐dominated electron transport in semiconducting solids, vacuum microelectronics relies on the scattering‐free, ballistic motion of electrons in vacuum. Since the first international conference on vacuum microelectronics substantial progress in this field has been made. The first technological devices using micrometer‐sized electron emitting structures are currently being commercialized. Field‐emission flat‐panel displays (FED) seem to be an especially promising competitor to LCD displays. Today there is only one mature technology for producing micro‐gated field‐emission arrays: the Spindt metal‐tip process. The drawbacks of this technology are expensive production, critical lifetime in vacuum, and high operating voltage. Carbon nanotubes (CNT) can be regarded as the potential second‐generation technology to the Spindt metal micro‐tip. In this review we show that the field emission (FE) behavior of CNT can be accurately described by Fowler–Nordheim tunneling and that the field‐enhancement factor β is the most prominent factor. Therefore the FE properties of a CNT thin film can be understood in terms of local field enhancement β(x,y), which can be determined with scanning anode field emission microscopy (SAFEM). To characterize the FE properties of an ensemble of electron emitters we used a statistical approach (as for thin film emitters), where f(β)dβ gives the number of emitters on a unit area with field‐enhancement factors within the interval [β,β + dβ]. We show that the field‐enhancement distribution function f(β) gives an almost complete characterization of the FE properties.     

Mechanical Exfoliation and Characterization of Single‐ and Few‐Layer Nanosheets of WSe2, TaS2, and TaSe2

Single‐ and few‐layer transition‐metal dichalcogenide nanosheets, such as WSe₂, TaS₂, and TaSe₂, are prepared by mechanical exfoliation. A Raman microscope is employed to characterize the single‐layer (1L) to quinary‐layer (5L) WSe₂ nanosheets and WSe₂ single crystals with a laser excitation power ranging from 20 μW to 5.1 mW. Typical first‐order together with some second‐order and combinational Raman modes are observed. A new peak at around 308 cm^?1 is observed in WSe₂ except for the 1L WSe₂, which might arise from interlayer interactions. Red shifting of the A_1g mode and the Raman peak around 308 cm^?1 is observed from 1L to 5L WSe₂. Interestingly, hexagonal‐ and monoclinic‐structured WO₃ thin films are obtained during the local oxidation of thinner (1L–3L) and thicker (4L and 5L) WSe₂ nanosheets, while laser‐burned holes are found during the local oxidation of the WSe₂ single crystal. In addition, the characterization of TaS₂ and TaSe₂ thin layers is also conducted.     

Understanding barriers to home‐based and self‐care in‐center hemodialysis

Despite superior outcomes and lower associated costs, relatively few patients with end‐stage renal disease undergo self‐care or home hemodialysis. Few studies have examined patient‐ and physician‐specific barriers to self‐care and home hemodialysis in the modern era. The degree to which innovative technology might facilitate the adoption of these modalities is unknown. We surveyed 250 patients receiving in‐center hemodialysis and 51 board‐certified nephrologists to identify key barriers to adoption of self‐care and home hemodialysis. Overall, 172 (69%) patients reported that they were “likely” or “very likely” to consider self‐care hemodialysis if they were properly trained on a new hemodialysis system designed for self‐care or home use. Nephrologists believed that patients were capable of performing many dialysis‐relevant tasks, including: weighing themselves (98%), wiping down the chair and machine (84%), clearing alarms during treatment (53%), taking vital signs (46%), and cannulating vascular access (41%), but thought that patients would be willing to do the same in only 69%, 34%, 31%, 29%, and 16%, respectively. Reasons that nephrologists believe patients are hesitant to pursue self‐care or home hemodialysis do not correspond in parallel or by priority to reasons reported by patients. Self‐care and home hemodialysis offer several advantages to patients and dialysis providers. Overcoming real and perceived barriers with new technology, education and coordinated care will be required for these modalities to gain traction in the coming years.     

Evaluation of the strain energy density control volume for a nanoscale singular stress field

Fracture mechanics at micro‐ and nano‐scale has become a very attractive topic in the last years. However, the results are still few, mostly because of the lack of effective analytical tools and of the difficult to conduct experimental tests at those scales. In this study, the authors report preliminary analysis on the application of the Strain Energy Density (SED) method at nano‐scale. In detail, starting from mechanical properties experimentally evaluated on small single crystal silicon cracked specimens, a first evaluation of the control volume due to a nano‐size singular stress field is carried out. If the extension of the SED approach at micro‐ nano‐scale is given in near future, an easy and fast tool to design against fatigue will be provided for micro‐ nano‐devices such as MEMS and NEMS, resulting in a significant technological impact and providing an easy and fast tool to conduct static and fatigue assessment at micro‐ and nano‐scale.     

Anwendungsfelder moderner Oberflächentechnik bei Anbietern oberflächentechnologischer Dienstleistungen

Concerning the transfer of results from research and development into commercial business practice for small and middle sized enterprises, offering surface‐technological services, the situation is generally better than aspected. This is the conclusion arrived at by the Institut for knowledge transfer at the University of Bremen (IfW) after carrying out a random analysis of the enterprises offering surface technology services. The study is a component of the project “Technology transfer surface technology”, which is accomplished on behalf the Federal Ministry for education and research (BMBF) by the VDI Technologiezentrum. Two thirds of the enterprises asked plan to introduce new procedures or modernize and/or supplement existing procedures in the next two years. All the same one third plans on top of this to use new layer materials. At present the situation regarding the application of modern surface technology, shows that the correct application of the surface and layer technologies bears fruits. The degree to which thermal spraying and the PVD and CVD techniques are applied has increased. Old procedures are rapidly being displaced by innovative and more pollution free procedures – especially in the field of thermal treatment. The technological developments planned for the next two years by the enterprises asked show that the degree with which the technologies specified above are spreading will continue to increase. Also the predication as to, which industries will be ranked in the future as important customers of the surface‐technological services, is changing. While the enterprises evaluate the situation toke restrained in the electro‐technology and electronics industry. An increased demand from air and space industry is expected. Moreover a clear increase in the paper and graphic arts industry is predicted.     

Conformation‐Controlled Molecular Sieving Effects for Membrane‐Based Propylene/Propane Separation

Membrane‐based separation is poised to reduce the operation cost of propylene/propane separation; however, identifying a suitable molecular sieve for membrane development is still an ongoing challenge. Here, the successful identification and use of a metal–organic framework (MOF) material as fillers, namely, the Zr‐fum‐ fcu ‐MOF possessing an optimal contracted triangular pore‐aperture driving the efficient diffusive separation of propylene from propane in mixed‐matrix membranes are reported. It is demonstrated that the fabricated hybrid membranes display a high propylene/propane separation performance, far beyond the current trade‐off limit of polymer membranes with excellent properties under industrial conditions. Most importantly, the mechanism behind the exceptional high propylene/propane selectivity is delineated by exploring theoretically the efficiency of sieving of different conformers of propane through the hypothesized triangular rigid pore‐aperture of Zr‐fum‐ fcu ‐MOF.     

A Dual‐Responsive Mesoporous Silica Nanoparticle for Tumor‐Triggered Targeting Drug Delivery

A novel pH‐ and redox‐ dual‐responsive tumor‐triggered targeting mesoporous silica nanoparticle (TTTMSN) is designed as a drug carrier. The peptide RGDFFFFC is anchored on the surface of mesoporous silica nanoparticles via disulfide bonds, which are redox‐responsive, as a gatekeeper as well as a tumor‐targeting ligand. PEGylated technology is employed to protect the anchored peptide ligands. The peptide and monomethoxypolyethylene glycol (MPEG) with benzoic‐imine bond, which is pH‐sensitive, are then connected via “click” chemistry to obtain TTTMSN. In vitro cell research demonstrates that the targeting property of TTTMSN is switched off in normal tissues with neutral pH condition, and switched on in tumor tissues with acidic pH condition after removing the MPEG segment by hydrolysis of benzoic‐imine bond under acidic conditions. After deshielding of the MPEG segment, the drug‐loaded nanoparticles are easily taken up by tumor cells due to the exposed peptide targeting ligand, and subsequently the redox signal glutathione in tumor cells induces rapid drug release intracellularly after the cleavage of disulfide bond. This novel intelligent TTTMSN drug delivery system has great potential for cancer therapy.     

Engineering the Future of Silk Materials through Advanced Manufacturing

Silk is a natural fiber renowned for its outstanding mechanical properties that have enabled the manufacturing of ultralight and ultrastrong textiles. Recent advances in silk processing and manufacturing have underpinned a re‐interpretation of silk from textiles to technological materials. Here, it is argued that silk materials—optimized by selective pressure to work in the environment at the biotic–abiotic interface—can be harnessed by human micro‐ and nanomanufacturing technology to impart new functionalities and opportunities. A critical overview of recent progress in silk technology is presented with emphasis on high‐tech applications enabled by recent innovations in multilevel modifications, multiscale manufacturing, and multimodal characterization of silk materials. These advances have enabled successful demonstrations of silk materials across several disciplines, including tissue engineering, drug delivery, implantable medical devices, and biodissolvable/degradable devices.     

Nanostructuring Lipophilic Dyes in Water Using Stable Vesicles,Quatsomes, as Scaffolds and Their Use as Probes for Bioimaging

A new kind of fluorescent organic nanoparticles (FONs) is obtained using quatsomes (QSs), a family of nanovesicles proposed as scaffolds for the nanostructuration of commercial lipophilic carbocyanines (1,1′‐dioctadecyl‐3,3,3′,3′‐tetramethyl‐indocarbocyanine perchlorate (DiI), 1,1′‐dioctadecyl‐3,3,3′,3′‐tetramethyl‐indodicarbocyanine perchlorate (DiD), and 1,1′‐dioctadecyl‐3,3,3′,3′‐tetramethyl‐indotricarbocyanine iodide (DiR)) in aqueous media. The obtained FONs, prepared by a CO₂‐based technology, show excellent colloidal‐ and photostability, outperforming other nanoformulations of the dyes, and improve the optical properties of the fluorophores in water. Molecular dynamics simulations provide an atomistic picture of the disposition of the dyes within the membrane. The potential of QSs for biological imaging is demonstrated by performing superresolution microscopy of the DiI‐loaded vesicles in vitro and in cells. Therefore, fluorescent QSs constitute an appealing nanomaterial for bioimaging applications.     

Charge‐Storage Aromatic Amino Compounds for Nonvolatile Organic Transistor Memory Devices

Here, charge‐storage nonvolatile organic field‐effect transistor (OFET) memory devices based on interfacial self‐assembled molecules are proposed. The functional molecules contain various aromatic amino moieties (N‐phenyl‐N‐pyridyl amino‐ (PyPN), N‐phenyl amino‐ (PN), and N,N‐diphenyl amino‐ (DPN)) which are linked by a propyl chain to a triethoxysilyl anchor group and act as the interface modifiers and the charge‐storage elements. The PyPN‐containing pentacene‐based memory device (denoted as PyPN device) presents the memory window of 48.43 V, while PN and DPN devices show the memory windows of 24.88 and 8.34 V, respectively. The memory characteristic of the PyPN device can remain stable along with 150 continuous write‐read‐erase‐read cycles. The morphology analysis confirms that three interfacial layers show aggregation due to the N atomic self‐catalysis and hydrogen bonding effects. The large aggregate‐covered PyPN layer has the full contact area with the pentacene molecules, leading to the high memory performance. In addition, the energy level matching between PyPN molecules and pentacene creates the smallest tunneling barrier and facilitates the injection of the hole carriers from pentacene to the PyPN layer. The experimental memory characteristics are well in agreement with the computational calculation.     

Modelling three‐dimensional piece‐wise homogeneous domains using the α‐shape‐based natural element method

In this paper, the application of the natural element method (NEM) to the numerical analysis of two‐ and three‐dimensional piece‐wise homogeneous domains is presented. The NEM differs from other meshless methods in its capability to accurately reproduce essential boundary conditions along convex boundaries. The α‐shape‐based extension of this method (α‐NEM) generalizes this behaviour to non‐convex domains, enables us to construct models entirely in terms of the initial cloud of points and allows us to simulate material discontinuities in a straightforward manner. In the following sections, simple and effective algorithms are presented for the construction of α‐shapes in domains composed of various materials. Examples are presented in two‐ and three‐dimensional cases in the context of linear elastostatics showing good performance even with the simple numerical quadrature used. Copyright © 2002 John Wiley & Sons, Ltd.     

Negatively Charged Gold Nanoparticles Inhibit Alzheimer's Amyloid‐β Fibrillization,Induce Fibril Dissociation,and Mitigate Neurotoxicity

Amyloids are pathogenic hallmarks in many neurodegenerative diseases such as amyloid‐β (Aβ) fibrils in Alzheimer's disease (AD). Here, the effect of gold nanoparticles (AuNPs) on amyloids is examined using Aβ as a model system. It is found that bare AuNPs inhibited Aβ fibrillization to form fragmented fibrils and spherical oligomers. Adding bare AuNPs to preformed Aβ fibrils results in ragged species where AuNPs bind preferentially to fibrils. Similar results are demonstrated with carboxyl‐ but not amine‐conjugated AuNPs. Co‐incubation of negatively charged AuNPs with Aβ relieved Aβ toxicity to neuroblastoma. Overall, it is demonstrated that AuNPs possessing negative surface potential serve as nano‐chaperones to inhibit and redirect Aβ fibrillization, which could contribute to applications for AD.     

Qualifikationsbedarf Oberflächentechnik: Unternehmen,Universitäten,Fachhochschulen. Need of qualification surface technology: enterprises,universities, universities of applied sciences

With constantly growing requirements for research, development and application the modern surface technology has been developed into an interdisciplinary key and cross section technology. Tailor‐made qualification is a substantial condition, in order to fully exploit the potential of innovation in this future field. Not sufficient offers of further education and lacking qualification of the operational personnel can obstruct the industrial application of surface technology. This paper specifies qualification requirements of enterprises within the area of surface techniques and reveals, how universities and universities of applied sciences adjust themselves future‐oriented to the qualification need and contribute to the broadening of the technological efficiency. Current studies are taken as a basis, which were conducted on behalf of the Federal Ministry of Education and Research and coordinated by the VDI Technology Center Duesseldorf in the context of a qualification initiative on surface technology.     

Large firms and the science-technology interface Patents,patent citations,and scientific output of multinational corporations in thin films

Firms operating in science-based technological fields reflect some of the complexities of the science-technology interaction. The present study attempts to investigate these interactions by analyzing patent citations, publication and patent outputs of multinational corporations (MNCs) in 'thin film' technology. In particular we explore different characteristics of knowledge production and knowledge utilization of these firms. The results indicate no correlation between intensity of research activity and patents produced by the MNCs. The relationship between scientific and technological knowledge generation as well as the linkage between science and technology appear to be firm-specific rather than dependent on a technological or industrial sector. The dispersion of journal sources for the majority of patent citations of scientific literature as well as for the majority of scientific outputs is narrow. Basic journals play an important role in patent citation as well as in addressing research of MNCs in thin-film technology.     

An Analysis of Motivation Constructs with First‐Year Engineering Students: Relationships Among Expectancies,Values, Achievement,and Career Plans

Background Researchers have identified many factors affecting undergraduate engineering students' achievement and persistence. Yet, much of this research focuses on persistence within academia, with less attention to career plans after graduation. Furthermore, the relative influence of expectancy‐versus value‐related beliefs on students' achievement and career plans is not fully understood. Purpose (Hypothesis ) To address these gaps, we examined the relationships among the following motivation constructs for female and male first‐year engineering students: (a) expectancy‐related constructs that included engineering self‐efficacy (i.e., a judgment of one's ability to perform a task in engineering) and expectancy for success in engineering (i.e., the belief in the possibility of success in engineering); (b) value‐related constructs that included identification with engineering (i.e., the extent to which one defines the self through a role or performance in engineering) and engineering values (i.e., beliefs related to engineering interest, importance, and usefulness); (c) engineering achievement; and (d) engineering career plans. Design /Method Participants included 363 first‐year engineering students at a large state university. The students completed an online survey instrument in the first and second semester of their first year. Results Students' expectancy‐ and value‐related beliefs decreased over the first year for both men and women. Men reported higher levels for expectancy‐related beliefs than women. Expectancy‐related constructs predicted achievement better than the value‐related constructs, whereas value‐related constructs predicted career plans better for both men and women. Conclusions Expectancy‐ and value‐related constructs predicted different outcomes. Thus, both types of constructs are needed to understand students' achievement and career plans in engineering.     

Tunable Energy Landscapes to Control Pathway Complexity in Self‐Assembled N‐Heterotriangulenes: Living and Seeded Supramolecular Polymerization

Herein, the synthesis and self‐assembling features of N‐heterotriangulenes 1 – 3 decorated in their periphery with 3,4,5‐trialkoxy‐N‐(alkoxy)benzamide moieties that enable kinetic control of the supramolecular polymerization process are described. The selection of an appropriate solvent results in a tunable energy landscape in which the relative energy of the different monomeric or aggregated species can be regulated. Thus, in a methylcyclohexane/toluene (MCH/Tol) mixture, intramolecular hydrogen‐bonding interactions in the peripheral side units favor the formation of metastable inactivated monomers that evolve with time at precise conditions of concentration and temperature. A pathway complexity in the supramolecular polymerization of 1 – 3 cannot be determined in MCH/Tol mixtures but, importantly, this situation changes by using CCl₄. In this solvent, the off‐pathway product is a face‐to‐face H‐type aggregate and the on‐pathway product is the slipped face‐to‐face J‐type aggregate. The autocatalytic transformation of the metastable monomeric units, as well as the two competing off‐ and on‐pathway aggregates allow the realization of seeded and living supramolecular polymerizations. Interestingly, the presence of chiral, branched side chains in chiral ( S )‐ 2 noticeably retards the kinetics of the investigated transformations. This work brings to light the relevance of controlling the pathway complexity in self‐assembling units and opens new avenues for the investigation of complex and functional supramolecular structures.