bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiplexed p53 Mutation Detection by Microchip Electro‐phoresis with Laser‐Induced Fluorescence Detector
Authors: Li Gang , Ge Shuli , Ni Xiaofang , Wang Qingjiang , He Pinjiang , Fang Yuzhi
Published: June 2010

A form of single‐strand DNA‐conformation polymorphism analysis (SSCP) employing nondenaturing slab gel electrophoresis is applicable to the genetic diagnosis of mutations at exons 7, 8 and 9 of the p53 gene. Recently, microchip electrophoresis (ME) systems have been used in SSCP analysis instead of conventional slab gel electrophoresis in terms of speed, sensitivity and automation. The aim of the present study was to investigate the application of SSCP and ME analysis as a rapid and effective method to the detection of mutations for exons 7, 8 and 9 of the p53 gene. It was found that using the electric field strength 260 V/cm and the sieving matrix of 4 mg/mL poly(ethylene oxide) was very useful to achieve better resolution and fast detection of mutations at exons 7, 8 and 9 of p53 gene. Under the optimized conditions, mutations at exons 7–9 of p53 gene were analyzed within 60 s and the relative standard deviation values of the migration times were less than 5.81% (n=5). The detection limit can be as low as 1 ng·L−1.
Theory of Microbial Carbonate Precipitation and Its Application in Restoration of Cement‐based Materials Defects
Authors: Qian Chunxiang , Wang Ruixing , Cheng Liang , Wang Jianyun
Published: June 2010

Bacterial induced carbonate mineralization has been demonstrated as a new potential method for restoration of limestones in historic buildings and monuments. We claim here the formation of calcium carbonate was controlled by extracellular polymeric substances (EPS) isolated from Bacillus pasteurii. The process of crystallization nucleation was accelerated in the presence of cells and inhibited in the presence of EPS. The CaCO3 film deposited on cement paste surface was about 100 µm after 7 d treatment. The results of various restoring methods showed that higher decrease of water absorption of cement paste was gained in brushing application in the presence of agar, which could maintain urease with high activity in long term compared to spraying method. The coefficient of capillary suction of cement paste treated with brushing method was reduced by 90%. Mixed media consisted of sands, urea, Ca2+ and concentrated biomass, was injected into artificial cracks of cement paste followed by continual nutrient supplement, and CaCO3 particles were precipitated gradually between sands particles which were combined with cement matrix. The results showed that the compressive strength of recovered specimens was restored to 84%, which demonstrated that this kind of bio‐restoration method is effective in repairing surface defects of cement‐based materials.
Novel Monocyclam Derivatives as HIV Entry Inhibitors: Design, Synthesis, Anti‐HIV Evaluation, and Their Interaction with the CXCR4 Co‐receptor
Authors: Pettersson Sofia , Pérez‐Nueno Violeta I. , Mena Maria Pau , Clotet Bonaventura , Esté José A. , Borrell José I. , Teixidó Jordi
Published: June 2010

The CXCR4 receptor has been shown to interact with the human immunodeficiency virus (HIV) envelope glycoprotein gp120, leading to fusion of viral and cell membranes. Therefore, ligands that can attach to this receptor represent an important class of therapeutic agents against HIV, thus inhibiting the first step in the cycle of viral infection: the virus–cell entry/fusion. Herein we describe the in silico design, synthesis, and biological evaluation of novel monocyclam derivatives as HIV entry inhibitors. In vitro activity testing of these compounds in cell cultures against HIV strains revealed EC50values in the low micromolar range without cytotoxicity at the concentrations tested. Docking and molecular dynamics simulations were performed to predict the binding interactions between CXCR4 and the novel monocyclam derivatives. A binding mode of these compounds is proposed which is consistent with the main existing site‐directed mutagenesis data on the CXCR4 co‐receptor. Moreover, molecular modeling comparisons were performed between these novel monocyclams, previously reported non‐cyclam compounds from which the monocyclams are derived, and the well‐known AMD3100 bicyclam CXCR4 inhibitors. Our results suggest that these three structurally diverse CXCR4 inhibitors bind to overlapping but not identical amino acid residues in the transmembrane regions of the receptor.
Risk factors for central venous catheter thrombotic complications in children and adolescents with cancer
Authors: Revel‐Vilk S. , Yacobovich J. , Tamary H. , Goldstein G. , Nemet S. , Weintraub M. , Paltiel O. , Kenet G.
Published: June 2010

BACKGROUND:

The use of central venous catheters (CVCs) has greatly improved the quality of care in children with cancer, yet these catheters may cause serious infectious and thrombotic complications. The aim of this prospective registry study was to assess the host and CVC‐related risk factors for CVC‐created thrombotic complications.

METHODS:

Patients undergoing CVC insertion for chemotherapy were followed prospectively for CVC complications. At the time of enrollment, demographic, clinical, and CVC‐related data, and family history of thrombosis were collected. Survival and Cox regression analyses were performed.

RESULTS:

A total of 423 CVCs were inserted into 262 patients for a total of 76,540 catheter days. The incidence of CVC‐related deep‐vein thrombosis (DVT) was 0.13 per 1000 catheter‐days (95% confidence interval [CI], 0.06‐0.24). Insertion of peripherally inserted central catheters (PICCs) and insertion in an angiography suite significantly increased the risk of symptomatic CVC‐related DVT. The incidence of CVC occlusion was 1.35 per 1000 catheter‐days (95% CI, 1.1‐1.63). Positive family history of thrombosis significantly increased the risk of CVC occlusion (hazard ratio [HR], 2.16; 95% CI, 1.2‐3.8). The CVC‐related risk factors were insertion of Hickman catheters, insertion in angiography suite, and proximal‐tip location. Patients developing at least 1 episode of both CVC occlusion and infection had an increased risk for developing symptomatic CVC‐related DVT (HR, 4.15; 95% CI, 1.2‐14.4).

CONCLUSIONS:

Both patient‐related and CVC‐related factors are associated with higher risk of symptomatic thrombotic complications. These risk factors could be used in the clinical setting and in developing future studies for CVC thromboprophylaxis. Cancer 2010. © 2010 American Cancer Society.
Quantitative DNA methylation analysis detects cervical intraepithelial neoplasms type 3 and worse
Authors: Lai Hung‐Cheng , Lin Ya‐Wen , Huang Rui‐Lan , Chung Ming‐Tzeung , Wang Hui‐Chen , Liao Yu‐Ping , Su Po‐Hsuan , Liu Yung‐Liang , Yu Mu‐Hsien
Published: June 2010

BACKGROUND:

DNA methylation may be used a potential biomarker for detecting cervical cancer. The authors of this report used quantitative methylation analysis of 4 genes in a full spectrum of cervical lesions to test its potential clinical application.

METHODS:

This hospital‐based, retrospective, case‐control study was conducted in 185 patients and included patients who had a normal uterine cervix (n = 53), cervical intraepithelial neoplasm type 1 (CIN1) (n = 37), CIN2 (n = 22), CIN3 (n = 24), carcinoma in situ (CIS) (n = 22), squamous cell carcinoma (SCC, n = 20), and adenocarcinoma (AC) (n = 7). Methylation levels of the genes sex‐determining region Y, box 1 (SOX1); paired box gene 1 (PAX1); LIM homeobox transcription factor 1α (LMX1A), and NK6 transcription factor‐related locus 1 (NKX6‐1) were determined by using real‐time methylation‐specific polymerase chain reaction (PCR) amplification. Cutoff values of the percentage of methylation reference (PMR) for different diagnoses were determined to test the sensitivity and specificity and to generate receiver operating characteristic (ROC) curves. Two‐sided Mann‐Whitney U tests were used to test differences in PMR between groups.

RESULTS:

The PMRs of the 4 genes were significantly higher in CIN3 and worse (CIN3+) lesions than the PMRs in specimens of normal cervix and CIN1 or CIN2 (P < .001). ROC curve analysis demonstrated that the sensitivity, specificity, and accuracy for detecting CIN3+ lesions were 0.88, 0.82, and 0.95, respectively, for SOX1; 0.78, 0.91, and 0.89, respectively, for PAX1; 0.77, 0.88, and 0.90, respectively, for LMX1A; and 0.93, 0.97, and 0.97, respectively, for NKX6‐1.

CONCLUSIONS:

The current results indicated that quantitative PCR‐based testing for DNA methylation of 4 genes holds great promise for cervical cancer screening and warrants further population‐based studies using standardized DNA methylation testing. Cancer 2010. © 2010 American Cancer Society.
Evolvable hardware design based on a novel simulated annealing in an embedded system
Authors: He Guoliang , Xiong Naixue , Yang Laurence T. , Kim Tai‐hoon , Hsu Ching Hsien , Li Yuanxiang , Hu Ting
Published: June 2010

The auto‐design of electronic circuits for the next generation Information Technology (IT) computing environments is currently one of the most extensively studied issues in the field of evolvable hardware (EHW) architectures. It aims to improve the reliability and fault‐tolerance of hardware systems using embedded techniques. As the scalability of logic circuits becomes larger and more complex nowadays, its auto‐design is more and more difficult. In order to improve the efficiency and the capability of digital circuit auto‐design, in this paper, a multi‐objective simulated annealing (MSA)‐based increasable evolution approach is proposed in an embedded system. First, an extended matrix encoding method is used to indicate the potential performance of a circuit. Therefore, the risk of deleting a circuit with a good developing potential during evolution can be reduced. Second, we consider each output of a digital circuit as an objective, and MSA is designed for digital logic circuits with gradual evolution scheme. In the process of evolution, each objective is evolved in parallel with adaptive mechanism of neighborhood and a performance evaluation. Finally, a framework of online evolution with macro‐blocks is employed to implement MSA on a field‐programmable gate array efficiently and securely. In our experiments, six arithmetic circuits are designed to assess the performance of MSA with gate‐level and function‐level approaches comparing to other algorithms. The comparison results show that our method is very efficient in the auto‐design of EHW. Copyright © 2010 John Wiley & Sons, Ltd.
Performance modelling and analysis of Deficit Round Robin scheduling scheme with self‐similar traffic
Authors: Liu Lei , Jin Xiaolong , Min Geyong , Li Keqiu
Published: June 2010

The provisioning of fairness to various network applications is an important Quality‐of‐Service demand and has thus become a challenging research issue in contemporary communication networks. Deficit Round Robin (DRR) is a promising fair scheduling mechanism owing to its low complexity and excellent ability of achieving a good degree of fairness in terms of throughput. On the other hand, self‐similar traffic was found to be pervasively present in communication networks and has great impact on the performance of scheduling systems. However, to the best of our knowledge, there has not been any analytical model reported in the open literature for the DRR mechanism in the presence of self‐similar traffic. To fill this gap, this paper analytically investigates the queueing performance of DRR and develops a new analytical model for deriving the upper and lower bounds of the queue length distributions of individual traffic flows in DRR scheduling systems subject to self‐similar traffic. Extensive comparison between simulation and analytical results validates the accuracy of the developed model. To demonstrate its applications, the analytical model is used to investigate the effects of packet size on the performance of the queueing system. The developed model is further applied to study the configuration of weights of individual traffic flows. Copyright © 2010 John Wiley & Sons, Ltd.
Interactions between Oxygen Atoms on Pt(100): Implications for Ordering during Chemisorption and Catalysis
Authors: Liu Da‐Jiang , Evans James W.
Published: June 2010

We present a DFT analysis of the interactions between chemisorbed oxygen on the unreconstructed (1×1)‐Pt(100) surface. These interactions control ordering of O not just for single‐species adsorption, but also within O domains during coadsorption and reaction with other species such as CO. The calculations indicate that O prefers bridge sites, as deduced previously. In addition, we find a large difference in the interactions between O at different types of bridge site pairs separated by one lattice constant. There is strong repulsion for pairs separated by a Pt atom, but only a weak interaction for pairs separated by a fourfold hollow site. This finding elucidates the tendency for striped (n×1)‐O ordering often observed in chemisorption and reaction studies.
DNA Structural Changes Under Different Stretching Methods Studied By Molecular Dynamics Simulations
Authors: Qi Wenpeng , Lei Xiaoling , Fang Haiping
Published: June 2010

We present a molecular dynamics simulation study of 22‐mer DNA conformational variations obtained by stretching both 3′‐termini and both 5′‐termini. Stretching 3′‐termini by 3.5 nm required 142 kJ mol−1 and the force plateau was ∼80 pN, whereas stretching 5′‐termini by the same length required 190 kJ mol−1 and the force plateau was ∼100 pN. Stretching 3′‐termini led to a larger untwisting of the double helix and the successive base pairs rolled to the side of the DNA minor groove, while stretching 5′‐termini resulted in the base pairs rolling to the major groove side and reducing of the diameter of DNA molecule. The most distinctive difference between stretching 3′‐termini and 5′‐termini was that at the force plateau region stretching the 5′‐termini resulted in breakage of the base pairs, which considerably disturbed the structure of the DNA double helix. All of the variations of base rotation and translation for both stretching methods took place when the relative length of DNA l was longer than 1.2, which was the point the force plateau appeared.
Red to Green Switch Driven by Order in an Ionic IrIII Liquid‐Crystalline Complex
Authors: Szerb Elisabeta I. , Talarico Anna M. , Aiello Iolinda , Crispini Alessandra , Godbert Nicolas , Pucci Daniela , Pugliese Teresa , Ghedini Mauro
Published: June 2010

New cationic IrIII materials of general formula [Ir(ppy)2(Cn‐bpy)]PF6 {H(ppy) = 2‐phenylpyridine; Cn‐bpy = 3,4,5‐R‐4,4′‐benzoyloxymethyl‐2,2′‐bipyridine; n = 8, R = OC8H17; n = 0, R = H} were synthesised and fully characterised. Both complexes show high phosphorescence quantum yields in their condensed phases. Moreover, the introduction of long alkoxy chains on the bipyridne ligand in [Ir(ppy)2(C8‐bpy)]PF6 (1) has induced mesomorphism, and consequently a dynamic functional material with properties modulated by external stimuli has been obtained. Starting from the isotropic phase, on slow cooling a crystalline phase characterised by a bright green emission is obtained. However, on fast cooling a kinetically favoured columnar hexagonal mesophase is preferentially formed, which is stable down to room temperature. In this phase, the high luminescence is still maintained, even if a switch to yellow emission colour is observed. Moreover, through spin coating of solutions of 1, it has been possible to obtain its amorphous thin film to accomplish a further shift of the emission wavelength in the orange‐red spectral range. A fully reversible colour tuning process by surface stress and heating from the orange‐red film to the green crystalline phase, indicative of a mechanochromic behaviour, is also achieved.
Novel Synthetic Strategy towards the Efficient Synthesis of Substituted Bis(pyrazolyl)(2‐pyridyl)methane Ligands
Authors: Hoffmann Alexander , Flörke Ulrich , Schürmann Markus , Herres‐Pawlis Sonja
Published: June 2010

A general one‐pot synthesis of new substituted heteroscorpionate ligands is presented. These mixed‐functionality ligands were obtained in a catalyzed Peterson rearrangement starting from the substituted pyrazole, thionyl chloride, and an aldehyde. Thus, the synthesis of polyfunctional tridentate ligands is enabled, and they contain, besides the two pyrazole groups, other functionalities relevant for coordination chemistry. Additionally, the steric hindrance is easily defined in the ligands by the substitution of the pyrazole rings. By combination of the versatility in donor function and steric demand, a systematic tuning of the properties of the bis(pyrazolyl)methane ligands is possible. The synthesis and full characterization of 11 bis(pyrazolyl)methane ligands are reported. Two of these were structurally characterized as well.
Orthogonal Regioselective Synthesis of N‐Alkyl‐3‐substituted Tetrahydroindazolones
Authors: Kim Jonghoon , Song Heebum , Park Seung Bum
Published: June 2010

A divergent strategy for the regioselective and orthogonal synthesis of complementary regioisomers of N‐alkyl‐3‐substituted‐tetrahydroindazolones 3 and 4 was achieved from Boc‐protected alkylhydrazines 1. The robustness and substrate generality of this method were validated by synthesizing 3 and 4 through the intra‐ and intermolecular condensation of 1 with various 2‐acylcyclohexane‐1,3‐diones 2 and aldehydes, respectively.
Outdoor to indoor channel characteristics on two different floors
Authors: Wang Wei , Jost Thomas , Dammann Armin
Published: June 2010

Recently the fusion of positioning and wireless communication has gained many interests due to the merits of location information for future communication systems. Both positioning and wireless communication are highly dependent on the air channel. Current channel models are well suited for communication applications but less for positioning. Therefore, we investigate and compare the channel characteristics of different floors in favour of positioning based on an outdoor to indoor broadband channel sounder measurement campaign. Power delay profiles on both floors show similar structure caused by outdoor wave propagation, and angle of arrivals mostly arrive from the same direction. Differences can be seen in the RMS delay spread, power, NLoS error and coherence characteristics. Copyright © 2010 John Wiley & Sons, Ltd.
Semi‐implicit subgrid modelling of three‐dimensional free‐surface flows
Authors: Casulli Vincenzo , Stelling Guus S.
Published: June 2010

In this paper, a semi‐implicit numerical model for two‐ and three‐dimensional free‐surface flows will be formulated in such a fashion as to intrinsically account for subgrid bathymetric details. It will be shown that with the proposed subgrid approach the model accuracy can be substantially improved without increasing the corresponding computational effort. Copyright © 2010 John Wiley & Sons, Ltd.
Curvilinear finite elements for Lagrangian hydrodynamics
Authors: Dobrev V. A. , Ellis T. E. , Kolev Tz. V. , Rieben R. N.
Published: June 2010

We have developed a novel high‐order, energy conserving approach for solving the Euler equations in a moving Lagrangian frame, which is derived from a general finite element framework. Traditionally, such equations have been solved by using continuous linear representations for kinematic variables and discontinuous constant fields for thermodynamic variables; this is the so‐called staggered grid hydro (SGH) method. From our general finite element framework, we can derive several specific high‐order discretization methods and in this paper we introduce a curvilinear finite element method which uses continuous bi‐quadratic polynomial bases (the Q2 isoparametric elements) to represent the kinematic variables combined with discontinuous (mapped) bi‐linear bases to represent the thermodynamic variables. We consider this a natural generalization of the SGH approach and show that under simplifying low‐order assumptions, we exactly recover the classical SGH method. We review the key parts of the discretization framework and demonstrate several practical advantages to using curvilinear finite elements for Lagrangian shock hydrodynamics, including: the ability to more accurately capture geometrical features of a flow region, significant improvements in symmetry preservation for radial flows, sharper resolution of a shock front for a given mesh resolution including the ability to represent a shock within a single zone and a substantial reduction in mesh imprinting for shock waves that are not aligned with the computational mesh. Copyright © 2010 John Wiley & Sons, Ltd.
Reversed arterial flow in the paramedian segments of the liver after pancreaticoduodenectomy
Authors: Di Domenico Stefano , Santacroce Elena , Magoni Rossi Arianna , Giannone Antonella , Valente Umberto
Published: June 2010

Variation of splanchnic arterial anatomy is frequent and may complicate pancreatic surgery, leading to life‐threatening postoperative complications. We report a case of severe hepatic dysfunction after pancreaticoduodenectomy due to accidental section of the right hepatic artery. Bedside ultrasound examination showed a reversed arterial flow in the paramedian segments of the liver. Based on intraoperative and ultrasound findings, a retrograde arterial supply of the right liver from the left hepatic artery through spontaneous anastomosis between the arteries of segment 4 and the right paramedian segments was assumed and confirmed by postoperative CT examination. © 2010 Wiley Periodicals, Inc. J Clin Ultrasound 39:99–103, 2011
Novel parameter for the diagnosis of distal middle cerebral artery stenosis with transcranial Doppler sonography
Authors: Ahn Suk‐Won , Park Sang‐Soon , Lee Yong‐Seok
Published: June 2010

Purpose

Transcranial Doppler sonography (TCD) is commonly used for the diagnosis of middle cerebral artery (MCA) stenosis. However, TCD indices to predict distal MCA (M2) stenosis have not yet been established. We compared TCD and magnetic resonance angiography (MRA) to validate a new index for the diagnosis of M2 stenosis.

Methods

Consecutive patients who underwent TCD and MRA were included. Based on MRA, M2 stenosis was defined as >50% narrowing beyond the bifurcation area. TCD index of the M2/M1 ratio was defined as the ratio between the mean flow velocity (MFV) obtained at a depth of 30–44 mm (M2) and a depth of 45–65 mm (M1). Sensitivity and specificity of the M2/M1 ratio were calculated from the receiver operating characteristic curve. The diagnostic yield of elevated MFV (>80 cm/s) and asymmetry index of >30% for M2 stenosis were also investigated.

Results

Among the consecutive patients, 105 with M2 stenosis were compared with 123 without MCA stenosis. The M2/M1 ratio was significantly higher in the M2 stenosis group (1.10 versus 0.86, p < 0.001). Sensitivity and specificity for M2 stenosis were most satisfying when the M2/M1 ratio of 0.97 was adopted as the cutoff value. Diagnostic yield of the M2/M1 ratio was better than MFV or asymmetry index.

Conclusions

The M2/M1 ratio may be a highly specific parameter for assessing M2 stenosis with TCD. © 2010 Wiley Periodicals, Inc. J Clin Ultrasound 38:420–425, 2010
Cystic change in thyroid carcinoma: Prevalence and estimated volume in 360 carcinomas
Authors: Henrichsen Tara L. , Reading Carl C. , Charboneau J. William , Donovan Daniel J. , Sebo Thomas J. , Hay Ian D.
Published: June 2010

Purpose.

The aim of this study was to determine the prevalence and amount of cystic change in thyroid cancer. This study also examined associated sonographic characteristics of cystic malignant thyroid nodules to help recognize these clinically important nodules.

Methods.

This study was a retrospective review of 360 malignant thyroid nodules surgically removed at our institution between January 1, 2002 and December 31, 2004. All patients had signed research authorization. All patients had preoperative sonograms and surgical pathologic proof of their thyroid malignancy. The 360 malignant nodules were found in 307 patients. All scans were performed using 7‐ to 15‐MHz transducers, and most studies included a digital video clip of the cancer. The preoperative ultrasound examinations were retrospectively reviewed by three radiologists and a sonographer. An estimate of cystic component percentage was derived by consensus. The presence of a mural nodule, thick irregular wall, microcalcifications, and prominent vascularity was also recorded.

Results.

Of the 360 carcinomas, 318 (88.3%) were solid to minimally (less than 5%) cystic, 33 (9.2%) were 6–50% cystic, 9 (2.5%) were 51–100% cystic. Of the nine (2.5%) malignancies that were greater than 50% cystic, all had other suspicious findings including mural nodules, microcalcifications, increased vascularity, and/or a thick irregular wall about the cystic portion.

Conclusion.

The vast majority (88%) of thyroid cancer is uniformly solid or has minimal (1–5%) cystic change by sonography. Marked cystic change (>50% of the nodule) occurred in only 2.5% of cancers, which had other sonographic findings worrisome for malignancy. © 2010 Wiley Periodicals, Inc. J Clin Ultrasound 38:361‐366, 2010
Learning from errors: The role of context, emotion, and personality
Authors: Zhao Bin
Published: June 2010

This research focused on the relationship between negative emotionality and learning from errors. Specifically, negative emotionality was expected to impair learning from errors by decreasing motivation to learn. Perceived managerial intolerance of errors was hypothesized to increase negative emotionality, whereas emotional stability was proposed to decrease negative emotionality. All the hypotheses were tested in a laboratory simulation. Contrary to the prediction, a positive association was found between negative emotionality and motivation to learn. The effects of perceived managerial intolerance of errors and emotional stability on negative emotionality were as predicted. Moreover, exploratory data analyses were conducted at the level of specific negative emotions and revealed differentiated effects of specific negative emotions on learning from errors. Copyright © 2010 John Wiley & Sons, Ltd.
Work‐life flow: How individuals, Zappos, and other innovative companies achieve high engagement
Authors: Perschel Anne
Published: June 2010

Individuals, their coaches, and visionary leaders, including Zappos CEO Tony Hsieh, are aligning work and culture with the principles of flow to enrich careers, lives, and organizations. This article examines flow—an individual's state of maximum engagement—and the criteria for achieving it. It spells out methods for coaching people to achieve a state of flow at work, and then presents examples of how individuals have infused their jobs with flow. It also discusses several visionary leaders who incorporate flow states into their companies' culture, including an in‐depth look at how Hsieh uses flow principles to create high engagement and deliver superior business results. © 2010 Wiley Periodicals, Inc.
Storytelling at Juniper Networks connects a global organization to the values and behaviors of success
Authors: Ohara Stacey Clark , Cherniss Mariah
Published: June 2010

Culture had begun to drift in this high‐tech company, and new challenges called for some new behaviors to position the business for its second decade. Storytelling became the perfect tool to foster a deeper understanding of the company culture and unite employees across the organization, and it is now a key organizational capability for sustaining the Juniper Way. The authors describe the impact of growth on the culture of this start‐up, and detail a comprehensive storytelling initiative to integrate Juniper values and desired behaviors into a now global organization. They also discuss the ways storytelling was recently used to help launch a new business strategy and brand identity. © 2010 Wiley Periodicals, Inc.
Effect of acetonitrile–water mixtures on the reaction of dinitrochlorobenzene and dinitrochlorobenzotrifluoride with hydroxide ion
Authors: El‐Mallah N. M. , Senior S. A. , Nabil G. M. , Ramadan M. Sh. , Hamed E. A.
Published: June 2010

The kinetics of alkaline hydrolysis of 2‐chloro‐3,5‐dinitrobenzotrifluoride 1 and 1‐chloro‐2,4‐dinitrobenzene 2 were studied in various acetonitrile–water (AN–H2O) mixtures (10–90% w/w) at different temperatures. Thermodynamic parameters ΔH# and ΔS# show great variation, whereas ΔG# appears to vary little with the solvent composition presumably due to compensating variations. The results are discussed in terms of the solvent parameters such as preferential solvation, dielectric constant, polarity/polarizability, and hydrogen bond donor and acceptor parameters. It has been found that the factors controlling the reaction rates are the desolvation of OH−, the solvophobicity of the medium, and free water molecules in rich AN mixed solvent. The data showed that the solvatochromic parameters of (AN–H2O) mixed solvent are destroyed in the presence of excess OH−. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 453–463, 2010
A Core‐First Preparation of Poly(3‐alkylthiophene) Stars
Authors: Senkovskyy Volodymyr , Beryozkina Tetyana , Bocharova Vera , Tkachov Roman , Komber Hartmut , Lederer Albena , Stamm Manfred , Severin Nikolai , Rabe Jürgen P. , Kiriy Anton
Published: June 2010

A new and facile method for the preparation of mono‐ and hexa‐functional Ni‐bipyridyl‐based initiators that mediate Kumada polycondensation of 2‐bromo‐5‐chloromagnesio‐3‐hexylthiophene into head‐to‐tail regioregular poly(3‐hexylthiophene), P3HT, has been developed. An important advantage of the catalytic system presented herein is the ease of the preparation of a number of Ar‐Nibipy‐Br initiators from readily available aryl halides. As an example, the “core‐first” synthesis of 6‐arm star‐like P3HT having a hexaphenylbenzene core is demonstrated.
New Trends in Poly(ethylene oxide) or Polystyrene Macromonomer Based Networks Exhibiting Silsesquioxane Cross‐Linking Points
Authors: Harris Hassan , Nohra Bassam , Gavat Odile , Lutz Pierre J.
Published: June 2010

Poly(ethylene oxide) (PEO) hydrogels and polystyrene (PS) networks were synthesized in toluene by coupling α,ω‐diallyl PEO or α,ω‐diundecenyl PS macromonomers with octafunctional silsesquioxanes via hydrosilylation in the presence of a “Speier” catalyst. Their equilibrium swelling degree and uniaxial compression modulus could be controlled by the synthesis parameters, i.e. the solvent, the macromonomer molar mass and the macromonomer concentration.
Photo‐Plasticity in Thiol‐ene Network Polymers – A Review
Authors: Cook Wayne D. , Chen Fei , Nghiem Quoc Dat , Scott Timothy F. , Bowman Christopher N. , Chausson Sophie , Le Pluart Loic
Published: June 2010

In this paper we briefly overview the area of stimuli responsive polymers and the subset of photo‐plastic polymers which change shape or undergo stress relaxation during irradiation. The chemistry, mechanism and properties of a new class of photo‐plastic polymers is presented in detail – these tetrathiol‐diene networks contain an allylic dithioether (also termed allylic disulphide) unit in the network strands and when this moiety is attacked by a photogenerated radical, the allylic dithioether undergoes β‐cleavage which breaks one network bond and reforms another. Two different methods of integration of the allylic dithioether unit into the backbone are investigated – the use of a cyclic allylic dithioether which copolymerizes with a thiol‐ene system or the incorporation of the allylic dithioether moiety in a divinyl ether monomer which can directly copolymerize with the thiol. The photo‐plasticity effect of these thiol‐ene networks is revealed in both creep and stress relaxation experiments, however, the extent of photo‐plasticity is less extensive than expected. The polymerization kinetics and evolution of the rheological properties during photocuring are studied and the slower copolymerization of the monomer containing the allylic dithioether is discussed. The photo‐rheology and dynamic mechanical properties of the thiol‐ene networks are interpreted in terms of the network structure.
Mechanism of Peroxide Cross‐Linking of EPDM Rubber
Authors: van Duin Martin , Orza Ramona , Peters Ron , Chechik Victor
Published: June 2010

The results of three experimental studies, i.e. GC‐MS of peroxide‐cross‐linked alkene/alkane mixtures, 13C NMR of peroxide‐cured, 13C‐labeled 2‐ethylidene‐5‐norbornene ‐ ethylene‐propylene‐diene‐monomer (EPDM) and EPR of peroxide curing of EPDM, are combined, yielding a more accurate description of the mechanism of peroxide cure of EPDM. Both alkyl and allyl macro‐radicals are formed via H‐abstraction from the EPM main chain and the residual diene unsaturation, respectively. Combination of these macro‐radicals yields alkyl/alkyl, alkyl/allyl and allyl/allyl cross‐links and addition of these macro‐radicals to the residual diene unsaturation yields alkyl/alkene and allyl/alkene cross‐links.
Stimulus–Responsive Nematic Gels
Authors: Urayama Kenji
Published: June 2010

Nematic elastomers exhibit a rich variety of stimulus–response behaviors owing to their hybrid characters of liquid crystals and elastomers. The nematic elastomers swollen by low molecular mass liquid crystals show anisotropic swelling, and their volume and shape significantly depend on temperature. The swollen nematic elastomers exhibit macroscopic deformation together with a large change in optical birefringence in fast response to electric fields (electro–opto–mechanical effect). The mechanical stretching of the nematic elastomers normal to the initial director drives the director realignment along the elongation axis.
Liquid Crystal Elastomers with Magnetic Actuation
Authors: Winkler Moritz , Kaiser Andreas , Krause Simon , Finkelmann Heino , Schmidt Annette M.
Published: June 2010

Magneto‐active liquid crystal elastomers (LCEs) are accessible by the incorporation of superparamagnetic Fe3O4 nanoparticles into oriented nematic side‐chain LCEs and offer a contactless activation pathway to the nematic‐to‐isotrope transition by local magnetic heating in external fields. In magneto‐mechanical measurements, a sample contraction of up to 30% is observed under field influence, with full reversibility when the field is switched off. The load evolved reaches 60 kPa and more. The ability of the materials to respond to a contactless electromagnetic stimulus with a well‐defined contraction can be of use for various actuator applications.
Micellar Solutions of a Symmetrical Amphiphilic ABA Triblock Copolymer with a Temperature‐Responsive Shell
Authors: Jain A. , Kulkarni A. , Koumba A. M. Bivigou , Wang W. , Busch P. , Laschewsky A. , Müller‐Buschbaum P. , Papadakis C. M.
Published: June 2010

We have studied the thermal behavior of an ABA triblock copolymer having short, deuterated polystyrene end‐blocks and a longer poly(N‐isopropyl acrylamide) middle block, the latter exhibiting a lower critical solution temperature. The collapse of the micelles was investigated using dynamic light scattering. Small‐angle neutron scattering with contrast matching allowed us to quantify the core‐shell structure of the micelles as well as their correlations as a function of temperature.
The Localization Model of Rubber Elasticity
Authors: Douglas Jack F.
Published: June 2010

While the unusual elastic properties of rubbery polymer materials have been studied for literally centuries, a quantitative theoretical description of these properties in terms of molecular structural parameters remains a challenging task. Classical network elasticity theories are based on the concept of flexible volumeless network chains fixed into a network in which there are no excluded volume, or even topological, interactions between the chains and where the chains explore accessible configurations by Brownian motion. In this type of model, the elasticity of the deformed network derives from the entropic changes in this idealized network arising from a deformation of the network junction positions. The shortcoming of this approach is clear from the observation that unswollen rubbery materials are nearly incompressible, reflecting the existence of strong intermolecular interactions that restrict the polymer chains to an exploration of their local molecular environments. The imposition of a deformation of these solid rubbery materials then necessitates a consideration of how local molecular packing constraints become modified under deformation and the impact of these changes on the macroscopic elasticity of the material as a whole. Many researchers have struggled with this difficult problem, but we focus on the simple ‘localization model’ of rubber elasticity introduced by Gaylord and Douglas (GD), which provides an attractive and mathematically simple minimal model for the network elasticity of rubbers having strong intermolecular interactions in the dense polymer state. GD assume that the network chain segments are localized at the network junctions, as in classical elasticity theory, but they also consider the chains to be localized along their contours by a local harmonic potential arising from inter‐particle packing interactions, as in atoms in a simple harmonic crystal. This is the familiar Edwards‐De Gennes ‘tube’ model of polymers in the condensed state. The existence of the tube means that the entropy of the network chains is reduced relative to chains without this constraint, but the crucial problem is how this entropy change becomes modified as the material becomes deformed. GD approach this problem by first observing that both the volume of the material and the network chains are essentially invariant under deformation so they require that the dimensions of the confining tube to also be a deformation invariant where this constraint is applied at a segmental level. The properties of the resulting ‘localization model’ of elasticity of dry and swollen rubbers are summarized and some extensions of the model to describe chain finite extensibility and stiff polymer networks are briefly summarized.
Structural Characterization of Protein‐Imprinted Gels Using Lattice Monte Carlo Simulation
Authors: Levi Liora , Srebnik Simcha
Published: June 2010

Molecular imprinting is a technique for the creation of artificial recognition sites in synthetic organic or inorganic polymers, formed by cross‐linking in the presence of a template molecule. Removal of the templates leaves cavities that fit the template molecules in size, shape and functionality. Although this technique has been shown to be effective when targeting small rigid molecules, attempts to extend it to larger templates, such as proteins, have failed to show similar success. As opposed to small molecules, proteins are characterized by large size, flexible structure, and large number of functional groups available for recognition. These characteristics, among others, make it impossible to use imprinting procedures of small molecules for protein imprinting. In order to plan new imprinting strategies for proteins, one must reveal the problematic points in the polymerization process of the current methods, which result in low imprinting efficiency. In our research we focus on a bulk imprinting method using radical polymerization of hydrogels, applied to small globular proteins (e.g., lysosyme and cytochrome c). We model the system using lattice Monte Carlo (MC) simulation, using a modified kinetic gelation model (KGM) to simulate the polymerization process, which results in an inflexible protein‐imprinted gel. The effect of initiator molar ratio, polymer volume fraction (VF), cross‐linker density, and protein charge density and distribution on gelation, gel structure, and on the imprinted pore structure and functionality is investigated in the dry state of the gel. It is found that the imprinted pores wrap the template protein more fully and with larger number of linking sites than the non‐imprinted pores. The insertion of non‐template proteins with various charge densities and distributions into the imprinted pores indicates that charge density of the adsorbing protein is the dominant factor influencing the number of linked recognition sites.
Magnetically Induced Heating in Elastomeric Nanocomposites ‐ Theory and Experiment
Authors: Levine Igal , Zvi Regev Ben , Winkler Moritz , Schmidt Annette M. , Gottlieb Moshe
Published: June 2010

Magnetic nanoparticles are known to generate heat when exposed to an alternating external magnetic field. A multi‐scale model for the heat generation by magnetic nanoparticles embedded in an elastomeric material has been developed. The model affords the determination of the unsteady‐state temperature profiles in the particles and in the surrounding polymeric medium by numerically solving the equation of energy. We obtained the complete thermal history of the system as a function of all relevant parameters including particle size, particle volume fraction, thermal properties of the particle and the medium, and details of the imposed magnetic field. The predicted results are in good agreement with experimental data obtained on liquid crystalline elastomers.
Enclosure of Secondary Chirality Based on Highly‐Oriented Lipid Aggregates into a Polymer Sheet by Photo‐Induced Polymerization of Polymerizable Monomer Gels
Authors: Takafuji Makoto , Kira Yoshiko , Ishiordori Arata , Hachisako Hiroshi , Sawada Tsuyoshi , Ihara Hirotaka
Published: June 2010

The L‐glutamide derivative with double long‐chain alkyl groups and a pyrenyl head group (Pyr‐lipid) worked as organogelator in benzene and cyclohexane. Gelation was brought about through network formation with well‐developed fibrous aggregates based on lipid membrane‐like highly‐oriented structures. Gelation was observed in polymerizable monomers such as methyl methacrylate (MMA) and styrene (St). Extremely intense CD spectra were observed at the absorption band of pyrenyl group in a monomer solution at gel‐forming temperature, but the intensity decreased remarkably at the sol‐forming temperature. The transparent solid sheet was obtained by photo‐irradiation to the MMA gel in a quartz cell. More than 99% of MMA was polymerized even in the gel state and the weight‐average molecular weight (Mw) of the resultant polymer was 7.2 × 104 g mol−1. CD spectra indicated that chirally‐oriented structures in the gel state were maintained after polymerization of MMA and were stable at the temperature above the original gel‐to‐sol transition temperature. Fluorescence spectra of Pyr‐lipid in the monomer solutions supported that the pyrene excimer was formed in the lipid aggregates and the stabilization of the excimer formation was achieved by polymerization of MMA in the gel state.
Counterion and pH‐Mediated Structural Changes in Charged Biopolymer Gels
Authors: Horkay Ferenc , Basser Peter J. , Hecht Anne‐Marie , Geissler Erik
Published: June 2010

DNA solutions and gels exhibit a wide range of phenomena, many of which have not yet been fully understood. In the presence of multivalent counterions, attraction between charged DNA strands occurs. Increasing the concentration of multivalent ions leads to a decrease of the osmotic pressure, and a sufficiently high ion concentration results in the precipitation of the polymer. Replacing the monovalent counterions by hydrogen ions (decreasing the pH) also produces a marked decrease of the osmotic pressure, and at low pH a phase transition takes place. In this paper we analyze osmotic swelling pressure measurements and small‐angle neutron scattering (SANS) measurements made on chemically cross‐linked DNA gels swollen in near physiological salt solutions. The effect of calcium ions is compared with that of decreasing the pH of the equilibrium salt solution. We demonstrate that both the concentration dependence of the osmotic pressure and the SANS response of DNA gels display significant differences in the two cases.
Elastic finite element analysis on cross‐sections of random hollow sphere structures
Authors: Fiedler T. , Kim H. S. , Belova I. V. , Sloan S. W. , Murch G. E. , Öchsner A.
Published: June 2010

This paper addresses elastic analysis based on 2D finite element models for metallic hollow‐sphere structures. In the first part, the influence of micro‐porosity on the elastic behaviour of sintered metallic hollow sphere wall material is investigated. Young's modulus of the metallic hollow sphere wall material is found to linearly decrease with increasing micro‐porosity ranging up to about 45%. In the second part, elastic parameters for metallic syntactic foams (MSF) consisting of thin or thick walled hollow spheres, and for epoxy containing spherical pores are studied. Data obtained from finite element models are compared with theoretical predictions based on the rule of mixtures developed elsewhere and found to be in good agreement with each other for MSF but not for porous epoxy. The shear modulus of MSF with thin‐walled hollow spheres was found to increase with increasing volume fraction of matrix whereas that of MSF with thick walled hollow spheres was found to decrease. Specific Young's modulus of MSF with thin‐walled hollow spheres was also found to increase with increasing foam density whereas that of MSF with thick walled hollow spheres was found to decrease. Poisson's ratio obtained was relatively low for porous epoxy matrix material but high for MSF with thin or thick‐walled hollow spheres.

Dieser Artikel beschäftigt sich mit der elastischen Finite‐Elemente‐Analyse zwei‐dimensionaler Modelle von Hohlkugelstrukturen. Im ersten Teil der Arbeit wird der Einfluss von Mikroporosität auf das elastische Verhalten der gesinterten Hohlkugelschale untersucht. Es wurde beobachtet, dass der Elastizitätsmodul des gesinterten Materials linear mit steigender Porosität abnimmt. Der zweite Teil der Arbeit befasst sich mit Hohlkugelstrukturen bestehend aus Hohlkugeln und Epoxidmatrix verschiedener Wandstärkent: dickwandige Hohlkugeln, dünnwandige Hohlkugeln und dem Grenzfallt→ 0 (kugelförmige Einschlüsse ohne Hohlkugelschale). Die Ergebnisse der Finite‐Elemente‐Analyse wurden mit analytischen Modellen verglichen und mit Ausnahme der kugelförmigen Einschlüsse eine gute Übereinstimmung erzielt. Der Schubmodul dünnwandiger Hohlkugelstrukturen nimmt mit zunehmendem Volumenanteil der Epoxidmatrix zu, der Schubmodul von dickwandigen Hohlkugelstrukturen jedoch ab. Die ermittelten Querkontraktionszahlen sind für den Fall kugelförmiger Einschlüsse (t→ 0) vergleichsweise niedrig. Deutlich höhere Ergebnisse wurden für dünn‐ und dickwandige Hohlkugelstrukturen erzielt.
Large deformation of core materials for sandwich panels
Authors: Speich M. , Merkel M. , Öchsner A.
Published: June 2010

Sandwich panels represent a basic design unit for light weight structures. Sandwich panels typically consist of at least two different materials for core and skin. Within the scope of this paper, the large deformation behaviour of different cellular core materials for sandwich panels is investigated. The large deformation behaviour for different core materials is analysed experimentally by compression tests. We investigate metallic hollow sphere structures (MHSS) and synthetic polyvinyl chloride (PVC) foams. In addition, appropriate computational models are presented to account for the deformation mechanisms and to compare computational to experimental results. With these models we will be able to already validate the future experimental test set‐ups with numerical simulations before the test set‐up is build.

Sandwichelemente gelten als Grundstruktur für Leichtbau‐Konstruktionen. Sie bestehen normalerweise aus mindestens zwei verschiedenen Materialien für den Kern und die Deckschichten. Dieser Beitrag befasst sich mit dem Verhalten bei großer Verformung von verschiedenen Kernmaterialien. Dieses Verhalten wird mit einem Druckversuch experimentell für zwei solcher Kernmaterialien untersucht. Die beiden Materialien sind zum einen metallische Hohlkugelstrukturen (MHKS) und zum anderen ein Polyvinylchlorid‐Schaum. Zusätzlich werden dazu passende Simulationsmodelle erstellt, um die experimentell gewonnen Ergebnisse mit solchen aus der FE‐Analyse zu vergleichen. Mit diesen Modellen sind wir in der Lage, zukünftige Test‐Aufbauten bereits vor dem Bau mit Hilfe von numerischer Simulation zu überprüfen.