bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of degradable polymer composites from starch and poly(ethyl cyanoacrylate)
Authors: Kim Sanghoon , Peterson Steven C.
Published: April 2012

This report describes the development of degradable polymer composites, which can be made at room temperature without special equipment. The developed composites are made from poly(ethyl cyanoacrylate) and starch. Ethyl cyanoacrylate monomers are mixed with starch and the polymerization reaction of these monomers was initiated by dissociated OH‐ ions from moisture on the surface of the starch. After the polymerization, the body of starch granules acts as filler and the micrometer‐scale gaps formed by starch granules are filled with the poly(ethyl cyanoacrylate). The glass transition temperature of the composite matrix ranges from 106°C to 113°C and thermal degradation begins around 160°C. The polymer composites produced by this procedure contain 50–64 wt% of starch and have compressive strengths of 80 (±10) MPa. Optimum starch composition for these composites is ∼60 wt%. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
Investigation of adhesion phenomena in thermoplastic polyurethane injection molding process
Authors: Chen Jian‐Yu , Hwang Sheng‐Jye
Published: April 2012

Adhesion is a serious problem when ejecting products from mold cavities in the injection molding process. This study developed a mechanism for measuring adhesion force in injection molding process. The apparatus measured and quantified adhesion force and engineers could use the measurements to understand the effectiveness of mold release agent and different adhesion release coatings. Three different surface roughness conditions (Ra = 0.01, 0.08, and 1.20 μm) without surface coating were compared and the results showed that the smallest adhesion force would be obtained when Ra = 0.08 μm. With Ra = 0.08 μm and 0.01 μm, it was found that single‐layer CrN (chromium nitride) coating and modified CrN coating were effective in alleviating adhesion force whereas multi‐layer CrN coating was not effective. In addition, the adhesion force was proportional to the ejection speed, melting temperature, and cooling time. Because thermoplastic polyurethane (TPU) behaves like a rubber‐like material and is thus different from other stiff resin after cooling, the release of adhesion of TPU is time‐dependent. Comparing the peak and integrated impulse values of the measured curve in continuous experiment, it was found that these two results were in good agreement with each other. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
Barrier properties of poly(ethylene‐co‐vinyl acetate)/cellulose composite membranes
Authors: Elanthikkal Silviya , Francis Tania , Unnikrishnan G. , Varghese Soney , Guthrie J.T.
Published: April 2012

Poly(ethylene‐co‐vinyl acetate) (EVA)/cellulose composite membranes were prepared and their vapor permeation characteristics were studied. Two types of EVA [having vinyl acetate contents of 18% (EVA18) and of 40% (EVA40), respectively] were used for the composite fabrication. Cellulose, isolated from banana waste fibers, was used as the filler. It was observed that the EVA40 composites were more permeating than were the EVA18 composites. This observation is explained on the basis of more amorphous nature of EVA40 as compared to EVA18. The extent of vapor permeation decreased with increase in the cellulose content in the composites. The presence of voids in the polymer membranes that were designed to possess controlled behavior for the permeation was confirmed using scanning electron microscopic images to complement the observations made during the permeation studies. The influence of molecular weight, molar size, and polarity of the penetrants, on the permeation process, was also considered. The permeability of the membrane samples was calculated and the values obtained were compared with the theoretical values provided by using the modified Neilson permeability equation. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
Solid conveying in vane extruder for polymer processing: Effects on pressure establishment
Authors: Qu Jin‐Ping , Zhang Gui‐Zhen , Chen Hui‐Zhuo , Yin Xiao‐Chun , He He‐Zhi
Published: April 2012

The pressure establishment in the solid conveying section of a vane extruder was theoretically and experimentally studied in the present article. Based on the structural and conveying characteristics of the vane extruder, a four‐plate model was developed. The effects of the device geometry (eccentricity ε and discharge port β), the polymer properties (different materials), and the operating conditions (temperature and rotating speed) on the pressure were also studied using a visual experimental device. The results showed that the experimental data were highly consistent with the theoretical data, which indicated that the theoretical model was sensible. Considering the optimization design of the device and its processing parameters, the eccentricity ε and the discharge port β of the discharge baffle should be appropriately selected, and the setting temperature of the feeding section should be set to a low value. The rotating speed of the rotor had no significant influence on the pressure establishment. In addition, the thermo‐mechanical history of the vane extruder was shorter than that of the conventional screw extruder. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
Studies on compatibility of biodegradable starch/polyvinyl alcohol blends
Authors: Sreekumar P.A. , Al‐Harthi Mamdouh A. , De S.K.
Published: April 2012

Compatibility of starch/polyvinyl alcohol (PVA) blends, prepared by solution cast method, is dependent on the blend composition. Crystallinity of the blend, as measured by X‐ray diffraction (XRD) and differential scanning calorimeter (DSC), decreases with increase in starch content. Thermogravimetric analysis (TGA) shows that the broadness in the peak width at the degradation region increases with increase in starch content in the starch/PVA blend. Dynamic mechanical thermal analysis (DMTA) reveal that the broadness of the relaxation peaks is due to the partial compatibility of the glycerol plasticized starch/PVA blends. The tensile property decreases with increase in starch content and the 30/70 starch/PVA blend shows maximum ductility in respect to both the percentage of elongation and energy at break. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
Synthesis of single‐core and multiple‐core core‐shell nanoparticles by RAFT emulsion polymerization: Lead sulfide‐copolymer nanocomposites
Authors: Das Paramita , Claverie Jerome P.
Published: April 2012

We report here a simple and direct route for the preparation of lead sulfide (PbS) quantum dots (QDs) embedded into polymeric nanospheres by emulsion polymerization. In this process, QDs are first dispersed in an aqueous solution containing a statistical oligomer constituted of five butyl acrylate and ten acrylic acid units prepared by reversible addition fragmentation chain transfer (RAFT) polymerization using a trithiocarbonate as RAFT agent. Then, the dispersion of PbS QDs is engaged into an emulsion polymerization process to form core‐shell nanoparticles. Transmission electron microscopy reveals the presence of single‐core core‐shell particles at low concentration of PbS QD, whereas multiple‐core core‐shell particles containing either well separated or aggregated PbS QDs are formed at high concentration of PbS QDs. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Characterization of Nano‐Porous Bentonite (Montmorillonite) Particles using FTIR and BET‐BJH Analyses
Authors: Hayati‐Ashtiani Majid
Published: April 2012

Bentonite clays find wide industrial application and rich in Montmorillonite which is nano‐structured and nano‐porous member of smectite group and the dominant constituent of a bentonite. The mineralogical and physico‐chemical properties of bentonites are studied by some instrumental analyses such as FTIR, and BET‐BJH method. The FTIR analysis is used to compare the purity of various natural montmorillonite samples, namely S1 and S2. FTIR analysis reveals the absorptions due to Al · O · Si bending (where Al is an octahedral cation) at 524 cm–1, Si · O · Si Bending at 466 cm–1, and Al · Al · OH Bending at 917 cm–1 and these absorptions in turn indicate the presence of the dominant montmorillonite. This method shows that the natural bentonites contain non‐smectite phases in both samples. BET (Brunauer‐Emmett‐Teller) specific surface area and PSD (Pore Size Distribution) analyses show that the external surface area of sample S2 measured by BET method (ABET) (m2/g) is higher than that in S1 (17.4 to 14.4 m2/g) but S1 is more nano‐porous than S2. At last but not least, the properties of some bentonites are studied through a combination of instrumental analyses namely FTIR, and BET specific surface area and BJH (Barret‐Johner‐Halenda) pore size distribution analyses (BET‐BJH analyses).
Malignant pleural mesothelioma in a child with ataxia–telangiectasia
Authors: Rosas‐Salazar Christian , Gunawardena Sriya W. , Spahr Jonathan E.
Published: April 2012

Ataxia–telangiectasia (AT) is a hereditary disorder characterized by progressive neurological dysfunction, oculocutaneous telangiectasia, immunodeficiency, cancer susceptibility, and radiation sensitivity. Pleural neoplasms are extremely rare in the pediatric population, even in patients with AT. We describe the case of a 16‐year‐old male with AT who developed a malignant pleural mesothelioma (MPM). Benign or infectious lung and pleural diseases are common in those with AT. Hence, delayed diagnosis of respiratory neoplasms can occur in these patients. This report highlights the need of heightened vigilance in patients with AT with recurrent or persistent pleuropulmonary disease. To our knowledge, no other cases of MPM in children with AT have been reported. Pediatr Pulmonol. 2013; 48:94–97. © 2012 Wiley Periodicals, Inc.
Clinical safety, pharmacokinetics, and efficacy of ambrisentan therapy in children with pulmonary arterial hypertension
Authors: Takatsuki Shinichi , Rosenzweig Erika B. , Zuckerman Warren , Brady Daniela , Calderbank Michelle , Ivy D. Dunbar
Published: April 2012

Recent trials in adult PAH revealed the efficacy of ambrisentan. However, in children with PAH, the clinical safety and pharmacokinetics of ambrisentan has not been well studied. Our aim was to investigate the clinical safety, pharmacokinetics, tolerability, and efficacy of endothelin receptor antagonist therapy with ambrisentan in children with pulmonary arterial hypertension (PAH). This retrospective cohort study provides clinical data from pediatric patients with PAH receiving ambrisentan as add‐on therapy or transition from bosentan. Safety included evaluation of adverse events including aminotransferase abnormalities. The clinical impact was evaluated by improvement from baseline in clinical variables. A total of 38 pediatric patients with PAH received ambrisentan. Fifteen of 38 patients were switched from bosentan to ambrisentan. The remaining 23 children were treated with ambrisentan as an add‐on therapy due to disease progression. In both transition and add‐on cases, mean pulmonary artery pressure significantly improved (transition; 55 ± 18 vs. 45 ± 20 mmHg, n = 13, P = 0.04, add‐on; 52 ± 17 vs. 45 ± 19 mmHg, n = 13, P = 0.03) during the follow‐up. World Health Organization functional class improved in 31% of patients, but one patient required an atrial septostomy due to disease progression during the follow‐up period (median, range; 20, 4–44 months). Five patients (13%) discontinued ambrisentan due to severe headache, lack of clinical efficacy, or near syncope. Ten patients (26%) had side effects associated with ambrisentan treatment, including nasal congestion, headache, and flushing. However, no patients had aminotransferase abnormalities and there were no deaths after initiation of ambrisentan during follow‐up. Pharmacokinetics were evaluated in sixteen children treated with ambrisentan from 2.5 mg to 10.0 mg; the mean peak plasma concentration was 738 ± 452 ng/ml, mean time to peak plasma concentration was 3.2 ± 2.1 hours, and mean area under the curve plasma concentration was 6657 ± 4246 ng·hour/ml. In conclusion, initial experience with ambrisentan in children suggests that treatment is safe with similar pharmacokinetics to those in adults and may improve PAH in some children. Pediatr Pulmonol. 2013; 48:27–34. © 2012 Wiley Periodicals, Inc.
Mechanism of strain retention and shape memory in main chain liquid crystalline networks
Authors: Ren Wanting , Griffin Anselm C.
Published: April 2012

Liquid crystalline networks (LCNs) are described in which there is anelasticity in strain recovery response (under zero load) after uniaxial tensile loading. This strain retention is shown as a function of time after release of load and is further characterized by thermal, X‐ray, and stress/strain experiments. It was found that, at temperatures in the smectic phase far below the isotropization temperature, this LCN film retains significant levels of strain when in the monodomain state. On free recovery (zero load) of the LCN film there is a rapid elastic response followed by a slow anelastic response for those films that had undergone a polydomain‐to‐monodomain transition during the initial imposed strain regimen. It is postulated that the mechanism leading to the strain retention involves nanosegregation‐driven pinning of unfolded hairpins in shallow energy wells and that this effect is responsible for the thermally activated recovery of strain (shape memory) at elevated temperatures.

magnified image

Stress–strain curves of pre‐strained C11(MeHQ)Si8XL10 LC networks having various initial strains: (a) 350%, (b) 300%, (c) 250%, (d) 200%, (e) 150%, (f) 100%, and (g) 50%.
Chronic Administration of Daidzein, a Soybean Isoflavone, Improves Endothelial Dysfunction and Attenuates Oxidative Stress in Streptozotocin‐induced Diabetic Rats
Authors: Roghani Mehrdad , Vaez Mahdavi Mohammad‐Reza , Jalali‐Nadoushan Mohammad‐Reza , Baluchnejadmojarad Tourandokht , Naderi Gholamali , Roghani‐Dehkordi Farshad , Taghi Joghataei Mohammad , Kord Maryam
Published: April 2012

The effect of chronic daidzein, a soybean isoflavone, on aortic reactivity of streptozotocin‐diabetic rats was studied. Male diabetic rats received daidzein for 7 weeks a week after diabetes induction. Contractile responses to KCl and phenylephrine (PE) and relaxation response to acetylcholine (ACh) were obtained from aortic rings. Maximum contractile response of endothelium‐intact rings to PE was significantly lower in daidzein‐treated diabetic rats relative to untreated diabetic rats, and endothelium removal abolished this difference. Endothelium‐dependent relaxation to ACh was significantly higher in daidzein‐treated diabetic rats as compared with diabetic rats and pretreatment of rings with nitric oxide synthase inhibitor N(G)‐nitro‐l‐arginine methyl ester and/or indomethacin attenuated it. Two‐month diabetes also resulted in an elevation of malondialdehyde (MDA) and decreased superoxide dismutase (SOD) activity, and daidzein treatment significantly reversed the increased MDA content and reduced activity of SOD. Therefore, chronic treatment of diabetic rats with daidzein could prevent some abnormal changes in vascular reactivity in diabetic rats through nitric oxide and prostaglandin‐related pathways, and via attenuation of oxidative stress in aortic tissue and endothelium integrity seems essential for this effect. Copyright © 2012 John Wiley & Sons, Ltd.
Warranty Claim Forecasting Based On Weighted Maximum Likelihood Estimation
Authors: Akbarov Artur , Wu Shaomin
Published: April 2012

Warranty claims reported in recent months might carry more up‐to‐date information than those reported in earlier months. Using weighted maximum likelihood estimation for estimating model parameters might therefore lead to better performance of warranty forecasting models than maximum likelihood estimation. This paper examines this issue and also presents comparison of the forecasting performance of the parametric models such as Poisson processes and ARIMA models and non‐parametric models such as artificial neural networks. It shows that mixed non‐homogenous Poisson process models can lead to better forecasting results than other competing methods. The paper also shows that the models built with the weighted maximum likelihood estimation yield smaller error than those based on the maximum likelihood estimation. Copyright © 2012 John Wiley & Sons, Ltd.
Charts with Variable Sample Size, Sampling Interval, and Warning Limits
Authors: Mahadik Shashibhushan B.
Published: April 2012

The notion of variable warning limits is proposed for variable sample size and sampling interval (VSSI) charts. The basic purpose is to lower down the frequency of switches between the pairs of values of the sample sizes and sampling interval lengths of VSSI charts during their implementations. Expressions for performance measures for the variable sample size, sampling interval, and warning limits (VSSIWL) charts are developed. The performances of these charts are compared numerically with that of VSSI and VSSI (1, 3) charts, where VSSI (1, 3) charts are the VSSI charts with runs rule (1, 3) for switching between the pairs of values of sample sizes and sampling interval lengths. Runs rule (1, 3) greatly reduces the frequency of the switches; however, it slightly worsens the statistical performances of the VSSI charts in detecting moderate shifts in the process mean. It is observed that the out‐of‐control statistical performance and overall switching rate of VSSIWL charts are adaptive for the same in‐control statistical performances. These charts can be set to yield exactly similar performances as that of VSSI (1, 3) charts, to yield tradeoff performances between that of VSSI (1, 3) and VSSI charts, or to yield significantly lower switching rate than even that of VSSI (1, 3) charts at the cost of slightly inferior statistical performances than that of VSSI (1, 3) charts. Copyright © 2012 John Wiley & Sons, Ltd.
The Performance of the Adaptive Exponentially Weighted Moving Average Control Chart with Estimated Parameters
Authors: Saleh Nesma A. , Mahmoud Mahmoud A. , Abdel‐Salam Abdel‐Salam G.
Published: April 2012

The adaptive exponentially weighted moving average (AEWMA) control chart has the advantage of detecting balance mixed range of mean shifts. Its performance has been studied under the assumption that the process parameters are known. Under this assumption, previous studies have shown AEWMA to provide superior statistical performance when compared with other different types of control charts. In practice, however, the process parameters are usually unknown and are required to be estimated. Using a Markov Chain approach, we show that the performance of the AEWMA control chart is affected when parameters are estimated compared with the known‐parameter case. In addition, we show the effect of different standard deviation estimators on the chart performance. Finally, a performance comparison is conducted between the exponentially weighted moving average (EWMA) chart and the AEWMA chart when the process parameters are unknown. We recommend the use of the AEWMA chart over the ordinary EWMA chart especially when a small number of Phase I samples is available to estimate the unknown parameters. Copyright © 2012 John Wiley & Sons, Ltd.
Modeling absorption of the kindling fluorescent protein with the neutral form of the chromophore
Authors: Topol Igor , Collins Jack , Mironov Vladimir , Savitsky Alexander , Nemukhin Alexander
Published: April 2012

Kindling fluorescent protein (KFP) is an important member of the colored proteins family widely used as biomarkers in living cells. We apply quantum chemistry modeling of KFP properties by computing structure and spectra of a large molecular cluster mimicking the chromophore‐containing pocket, assuming the protonated (neutral) form of the chromophore in the trans configuration. We provide evidence that this protein conformation accounts for the previously observed but unassigned absorption band at 445 nm. We demonstrate that the structure and charge of the amino acid residues nearest to the chromophore play a role in the shifts in the absorption wave length, thus underlying a strong role of intermolecular interactions when considering properties of the fluorescent proteins. © 2012 Wiley Periodicals, Inc.
The optimization of wireless power transmission: design and realization
Authors: Jia Zhiwei , Yan Guozheng , Liu Hua , Wang Zhiwu , Jiang Pingping , Shi Yu
Published: April 2012

Background

A wireless power transmission system is regarded as a practical way of solving power‐shortage problems in multifunctional active capsule endoscopes.

Methods

The uniformity of magnetic flux density, frequency stability and orientation stability are used to evaluate power transmission stability, taking into consideration size and safety constraints. Magnetic field safety and temperature rise are also considered. Test benches are designed to measure the relevent parameters. Finally, a mathematical programming model in which these constraints are considered is proposed to improve transmission efficiency. To verify the feasibility of the proposed method, various systems for a wireless active capsule endoscope are designed and evaluated.

Results

The optimal power transmission system has the capability to supply continuously at least 500 mW of power with a transmission efficiency of 4.08%.

Conclusions

The example validates the feasibility of the proposed method. Introduction of novel designs enables further improvement of this method. Copyright © 2012 John Wiley & Sons, Ltd.
Input‐to‐state stability of a class of Lur'e descriptor systems
Authors: Yang Chunyu , Zhang Qingling , Huang Shoudong
Published: April 2012

This paper considers a class of Lur'e descriptor systems (LDS) subject to exogenous disturbances. The concept of input‐to‐state stability (ISS) is generalized to descriptor systems. Such a notion characterizes the robust stability of the full state of the systems. Based on the conventional ISS theory, a sufficient condition expressed by linear matrix inequalities (LMIs) for the LDS to be ISS is derived. It is further shown that this condition also guarantees a special class of LDS to be of index one. Then, a state feedback controller is designed to make the closed‐loop system ISS. Finally, an example is given to illustrate the obtained results. Copyright © 2012 John Wiley & Sons, Ltd.
Exponential stability and stabilization for nonlinear descriptor systems with discrete and distributed delays
Authors: Wu Jiancheng , Lu Guoping , Wo Songlin , Xiao Xiaoqing
Published: April 2012

This paper discusses the exponential stability and stabilization for nonlinear descriptor systems with discrete and distributed delays. In terms of the Lyapunov method, the exponential stability of the slow subsystem is firstly obtained. Then, a new homotopy‐based approach is proposed to investigate the exponential stability of the fast subsystem. By an estimate of the weighted matrix norm for a nonlinear mapping, the exponential stability of the fast subsystem and thus delay‐dependent sufficient conditions for the exponential stability of the systems are obtained. In addition, a state feedback controller is designed for the stabilization of the nonlinear descriptor systems. Finally, the effectiveness of the proposed approach is illustrated by numerical examples. Copyright © 2012 John Wiley & Sons, Ltd.
Modeling and security analysis of enterprise network using attack–defense stochastic game Petri nets
Authors: Wang Yuanzhuo , Li Jingyuan , Meng Kun , Lin Chuang , Cheng Xueqi
Published: April 2012

In this paper, we propose a novel modeling method attack–defense stochastic game Petri nets (or ADSGN) to model and analyze the security issues in enterprise network. We firstly give the definition and modeling method algorithm of ADSGN and then propose the algorithm of the strategy. The proposed ADSGN method is successfully applied to describe the attack and defense courses in the enterprise network. Finally, we analyze the mean time to first security breach and the mean time to security breach in the enterprise network quantifiably, and proved that our method can also be applied to other areas with respect to game issues. Copyright © 2012 John Wiley & Sons, Ltd.
Who bribes? Evidence from the United Nations' oil‐for‐food program
Authors: Jeong Yujin , Weiner Robert J.
Published: April 2012

How do managers react in an environment where bribery is likely to bring high rewards, but also presents high risks? We examine the supply side (firms' illicit payments) of bribery in a global setting, using the United Nations' (UN) Oil‐for‐Food Program, part of UN sanctions on Iraq. Some companies helped Iraq circumvent UN sanctions through bribe payments in the form of illicit surcharges. Our transaction‐level analysis of factors affecting bribe payments draws on the economic theory of crime, agency theory, and home country institutions. Results suggest that firms pay larger bribes when there are stronger financial and managerial incentives, but pay less when their home countries have implemented the OECD Anti‐Bribery Convention. We find little relationship between a widely used country‐level corruption perception index and firms' actual bribery. Copyright © 2012 John Wiley & Sons, Ltd.
Asymmetric Hybrid Silica Nanomotors for Capture and Cargo Transport: Towards a Novel Motion‐Based DNA Sensor
Authors: Simmchen Juliane , Baeza Alejandro , Ruiz Daniel , Esplandiu Maria José , Vallet‐Regí Maria
Published: April 2012

An innovative self‐propelled nanodevice able to perform motion, cargo transport, and target recognition is presented. The system is based on a mesoporous motor particle, which is asymmetrically functionalized by the attachment of single‐stranded DNA onto one of its faces, while catalase is immobilized on the other face. This enzyme allows catalytic decomposition of hydrogen peroxide to oxygen and water, giving rise to the driving force for the motion of the whole system. Moreover the motor particles are able to capture and transport cargo particles functionalized with a noncomplementary single‐stranded DNA molecule, only if a specific oligonucleotide sequence is present in the media. Functionalization with characteristic oligonucleotide sequences in the system implies a potential for further developments for lab‐on‐chip devices with applications in biomedical applications.
Resonant Laser‐Induced Formation of Double‐Walled Carbon Nanotubes from Peapods under Ambient Conditions
Authors: Berd Mourad , Puech Pascal , Righi Ariete , Benfdila Arezki , Monthioux Marc
Published: April 2012

The selective excitation of fullerenes encapsulated in single‐walled carbon nanotubes (SWCNTs) is carried out by irradiating them using a UV laser, the wavelength of which corresponds exactly to their maximum of absorption. Under such conditions, fullerenes strongly absorb the laser energy, open, and break, while the containing SWCNT merely acts as both a nanoreactor and a mold which is only weakly heated by the laser. The containing tube confines the fullerene fragments, promotes their reconstruction into an inner tube, and protects them from air oxidation. This leads to the overall formation of double‐walled carbon nanotubes (DWCNTs). The transformation is found to strongly depend on the laser irradiance and dose. This proves that the related mechanism is a multiphoton photolysis, different from the previous heat‐induced transformation attempts found in the literature, whether the heat is produced by means of a thermostat, infrared laser, or nonresonant UV laser. The actual peapod‐to‐DWCNT transformation is monitored by Raman spectroscopy and high‐resolution transmission electron microscopy.
Adjuvant Properties of Mesoporous Silica Particles Tune the Development of Effector T Cells
Authors: Vallhov Helen , Kupferschmidt Natalia , Gabrielsson Susanne , Paulie Staffan , Strømme Maria , Garcia‐Bennett Alfonso E. , Scheynius Annika
Published: April 2012

Alum is the most frequently used adjuvant today, primarily inducing Th2 responses. However, Th1‐type responses are often desirable within immune therapy, and therefore the development of new adjuvants is greatly needed. Mesoporous silica particles with a highly ordered pore structure have properties that make them very interesting for future controlled drug delivery systems, such as controllable particle and pore size; they also have the ability to induce minor immune modulatory effects, as previously demonstrated on human‐monocyte‐derived dendritic cells (MDDCs). In this study, mesoporous silica particles are shown to be efficiently engulfed by MDDCs within 2 h, probably by phagocytic uptake, as seen by confocal microscopy and transmission electron microscopy. A co‐culture protocol is developed to evaluate the capability of MDDCs to stimulate the development of naïve CD4+ T cells in different directions. The method, involving ELISpot as a readout system, demonstrates that MDDCs, after exposure to mesoporous silica particles (AMS‐6 and SBA‐15), are capable of tuning autologous naïve T cells into different effector cells. Depending on the size and functionalization of the particles added to the cells, different cytokine patterns are detected. This suggests that mesoporous silica particles can be used as delivery vehicles with tunable adjuvant properties, which may be of importance for several medical applications, such as immune therapy and vaccination.
Improved Photodynamic Cancer Treatment by Folate‐Conjugated Polymeric Micelles in a KB Xenografted Animal Model
Authors: Syu Wei‐Jhe , Yu Hsiu‐Ping , Hsu Chia‐Yen , Rajan Yeasudhasan Christu , Hsu Yuan‐Hung , Chang Yuan‐Chia , Hsieh Wen‐Yuan , Wang Chau‐Hui , Lai Ping‐Shan
Published: April 2012

Photodynamic therapy (PDT) is a light‐induced chemical reaction that produces localized tissue damage for the treatment of cancers and various nonmalignant conditions. In the clinic, patients treated with PDT should be kept away from direct sunlight or strong indoor lighting to avoid skin phototoxicity. In a previous study, it was demonstrated that the skin phototoxicity of meta‐tetra(hydroxyphenyl)chlorin (m‐THPC), a photosensitizer used in the clinic, can be significantly reduced after micellar encapsulation; however, no improvement in antitumor efficacy was observed. In this work, a folate‐conjugated polymeric m‐THPC delivery system is developed for improving tumor targeting of the photosensitizer, preventing photodamage to the healthy tissue, and increasing the effectiveness of the photosensitizers. The results demonstrate that folate‐conjugated m‐THPC‐loaded micelles with particle sizes around 100 nm are taken up and accumulated by folate receptor‐overexpressed KB cells in vitro and in vivo, and their PDT has no significant adverse effects on the body weight of mice. After an extended delivery time, a single dose of folate‐conjugated m‐THPC‐loaded micelles has higher antitumor effects (tumor growth inhibition = 92%) through inhibition of cell proliferation and reduction of vessel density than free m‐THPC or m‐THPC‐loaded micelles at an equivalent m‐THPC concentration of 0.3 mg kg−1 after irradiation. Furthermore, folate‐conjugated m‐THPC‐loaded micelles at only 0.2 mg kg−1 m‐THPC have a similar antitumor efficacy to m‐THPC or m‐THPC‐loaded micelles with the m‐THPC concentration at 0.3 mg kg−1, which indicates that the folate conjugation on the micellar photosensitizer apparently reduces the requirement of m‐THPC for PDT. Thus, folate‐conjugated m‐THPC‐loaded micelles with improved selectivity via folate–folate receptor interactions have the potential to reduce, not only the skin photosensitivity, but also the drug dose requirement for clinical PDT.
A Redox‐Switchable Au8‐Cluster Sensor
Authors: Wu Te‐Haw , Hsu Yu‐Yen , Lin Shu‐Yi
Published: April 2012

The proof of concept of a simple sensing platform based on the fluorescence of a gold cluster consisting of eight atoms, which is easily manipulated by reduction and oxidation of a specific molecule in the absence of chemical linkers, is demonstrated. Without using any coupling reagents to arrange the distance of the donor–acceptor pair, the fluorescence of the Au8‐cluster is immediately switched off in the presence of 2‐pyridinethiol (2‐PyT) quencher. Through an upward‐curving Stern–Volmer plot, the system shows complex fluorescence quenching with a combination of static and dynamic quenching processes. To analyze the static quenching constant (V) by a “sphere of action” model, the collisional encounter between the Au8‐cluster and 2‐PyT presents a quenching radius (r) ≈5.8 nm, which is larger than the sum of the radii of the Au8‐cluster and 2‐PyT. This implies that fluorescence quenching can occur even though the Au8‐cluster and 2‐PyT are not very close to each other. The quenching pathway may be derived from a photoinduced electron‐transfer process of the encounter pair between the Au8‐cluster (as an electron donor) and 2‐PyT (as an electron acceptor) to allow efficient fluorescence quenching in the absence of coupling reagents. Interestingly, the fluorescence is restored by oxidation of 2‐PyT to form the corresponding disulfide compound and then quenched again after the reduction of the disulfide. This redox‐switchable fluorescent Au8‐cluster platform is a novel discovery, and its utility as a promising sensor for detecting H2O2‐generating enzymatic transformations is demonstrated.
Structural Effect and Mechanism of C70‐Carboxyfullerenes as Efficient Sensitizers against Cancer Cells
Authors: Liu Qiaoling , Guan Mirong , Xu Li , Shu Chunying , Jin Chan , Zheng Junpeng , Fang Xiaohong , Yang Yongji , Wang Chunru
Published: April 2012

Carboxyfullerenes with different adduct numbers and cage sizes are tested as photosensitizers for photodynamic therapy (PDT). The photodynamic efficiency of these carboxyfullerenes depends mainly on the cage size, C60 versus C70, and to a lesser extent on the adduct numbers. In particular, malonic acid modified C70 fullerenes are more efficient than their C60 counterparts as photosensitizers, and the mechanism of cell death induced by C70‐carboxyfullerene under light irradiation is investigated in detail. The results indicate that cell death occurs via necrosis accompanied by membrane blebbing, which is a unique phenomenon for photosensitizer‐induced cell death. Since C70‐carboxyfullerene displays an efficient PDT property and negligible dark cytotoxicity, it is promising for use in PDT applications, especially in vascular capillary diseases usually occurring under the surface.
Chiral Pinwheel Clusters Lacking Local Point Chirality
Authors: Sun Kai , Shao Ting‐Na , Xie Jia‐Le , Lan Meng , Yuan Hong‐Kuan , Xiong Zu‐Hong , Wang Jun‐Zhong , Liu Ying , Xue Qi‐Kun
Published: April 2012

The supramolecular pinwheel cluster is a unique chiral structure with evident handedness. Previous studies reveal that the chiral pinwheels are composed of chiral or achiral molecules with polar groups, which result in strong intermolecular interactions such as hydrogen‐bonding or dipole interactions. Herein, it is shown that the simple linear aromatic molecule, pentacene, can be self‐assembled into large chiral pinwheel clusters on the semimetal Bi(111) surface, due to enhanced intermolecular interactions. The pentacene pinwheels reveal two levels of organizational chirality: the chiral hexamers resulting from asymmetric shifting along the long molecular axis, and chiral arrangement of six hexamers with a rotor motif. Furthermore, a new relation between the local point chirality and organizational chirality is identified from the pinwheels: the former is not essential for the latter in 2D pinwheel clusters of the pentacene molecule.
Playing MUSIC — building context‐aware and self‐adaptive mobile applications
Authors: Floch J. , Frà C. , Fricke R. , Geihs K. , Wagner M. , Lorenzo J. , Soladana E. , Mehlhase S. , Paspallis N. , Rahnama H. , Ruiz P.A. , Scholz U.
Published: April 2012

Although the idea of context‐awareness was introduced almost two decades ago, few mobile software applications are available today that can sense and adapt to their run‐time environment. The development of context‐aware and self‐adaptive applications is complex and few developers have experience in this area. On the basis of several demonstrators built by the joint European research project MUSIC, this paper describes typical context and adaptation features relevant for the development of context‐aware and self‐adaptive mobile applications. We explain how the demonstrators were realised using the open‐source platform MUSIC and present the feedback of the developers of these demonstrators. The main contribution of this paper is to show how the development complexity of context‐aware and self‐adaptive mobile applications can be mastered by using an adaptation framework such as MUSIC. Copyright © 2012 John Wiley & Sons, Ltd.
MicroRNAs Regulate p21Waf1/Cip1 Protein Expression and the DNA Damage Response in Human Embryonic Stem Cells
Authors: Dolezalova Dasa , Mraz Marek , Barta Tomas , Plevova Karla , Vinarsky Vladimir , Holubcova Zuzana , Jaros Josef , Dvorak Petr , Pospisilova Sarka , Hampl Ales
Published: April 2012

Studies of human embryonic stem cells (hESCs) commonly describe the nonfunctional p53-p21 axis of the G1/S checkpoint pathway with subsequent relevance for cell cycle regulation and the DNA damage response (DDR). Importantly, p21 mRNA is clearly present and upregulated after the DDR in hESCs, but p21 protein is not detectable. In this article, we provide evidence that expression of p21 protein is directly regulated by the microRNA (miRNA) pathway under standard culture conditions and after DNA damage. The DDR in hESCs leads to upregulation of tens of miRNAs, including hESC-specific miRNAs such as those of the miR-302 family, miR-371-372 family, or C19MC miRNA cluster. Most importantly, we show that the hESC-enriched miRNA family miR-302 (miR-302a, miR-302b, miR-302c, and miR-302d) directly contributes to regulation of p21 expression in hESCs and, thus, demonstrate a novel function for miR-302s in hESCS. The described mechanism elucidates the role of miRNAs in regulation of important molecular pathway governing the G1/S transition checkpoint before as well as after DNA damage.
Paternally Inherited Gsα Mutation Impairs Adipogenesis and Potentiates a Lean Phenotype In Vivo
Authors: Liu Jan-Jan , Russell Elizabeth , Zhang Deyu , Kaplan Frederick S. , Pignolo Robert J. , Shore Eileen M.
Published: April 2012

Paternally inherited inactivating mutations of the GNAS gene have been associated with a rare and disabling genetic disorder, progressive osseous heteroplasia, in which heterotopic ossification occurs within extraskeletal soft tissues, such as skin, subcutaneous fat, and skeletal muscle. This ectopic bone formation is hypothesized to be caused by dysregulated mesenchymal progenitor cell differentiation that affects a bipotential osteogenic-adipogenic lineage cell fate switch. Interestingly, patients with paternally inherited inactivating mutations of GNAS are uniformly lean. Using a mouse model of Gsα-specific exon 1 disruption, we examined whether heterozygous inactivation of Gnas affects adipogenic differentiation of mesenchymal precursor cells from subcutaneous adipose tissues (fat pad). We found that paternally inherited Gsα inactivation (Gsα+/p−) impairs adipogenic differentiation of adipose-derived stromal cells (ASCs). The Gsα+/p− mutation in ASCs also decreased expression of the adipogenic factors CCAAT-enhancer-binding protein (C/EBP)β, C/EBPα, peroxisome proliferator-activated receptor gamma, and adipocyte protein 2. Impaired adipocyte differentiation was rescued by an adenylyl cyclase activator, forskolin, and provided evidence that Gsα-cAMP signals are necessary in early stages of this process. Supporting a role for Gnas in adipogenesis in vivo, fat tissue weight and expression of adipogenic genes from multiple types of adipose tissues from Gsα+/p− mice were significantly decreased. Interestingly, the inhibition of adipogenesis by paternally inherited Gsα mutation also enhances expression of the osteogenic factors, msh homeobox 2, runt-related transcription factor 2, and osteocalcin. These data support the hypothesis that Gsα plays a critical role in regulating the balance between fat and bone determination in soft tissues, a finding that has important implications for a wide variety of disorders of osteogenesis and adipogenesis.
Direct Toll-Like Receptor-Mediated Stimulation of Hematopoietic Stem and Progenitor Cells Occurs In Vivo and Promotes Differentiation Toward Macrophages
Authors: Megías Javier , Yáñez Alberto , Moriano Silvia , O'Connor José-Enrique , Gozalbo Daniel , Gil María-Luisa
Published: April 2012

As Toll-like receptors (TLRs) are expressed by hematopoietic stem and progenitor cells (HSPCs), they may play a role in hematopoiesis in response to pathogens during infection. We show here that TLR2, TLR4, and TLR9 agonists (tripalmitoyl-S-glyceryl-L-Cys-Ser-(Lys)4 [Pam3CSK4], lipopolysaccharide [LPS], and CpG oligodeoxynucleotide [ODN]) induce the in vitro differentiation of purified murine lineage negative cells (Lin−) as well as HSPCs (identified as Lin− c-Kit+ Sca-1+ IL-7Rα− [LKS] cells) toward macrophages (Mph), through a myeloid differentiation factor 88 (MyD88)-dependent pathway. In order to investigate the possible direct interaction of soluble microorganism-associated molecular patterns and TLRs on HSPCs in vivo, we designed a new experimental approach: purified Lin− and LKS cells from bone marrow of B6Ly5.1 mice (CD45.1 alloantigen) were transplanted into TLR2−/−, TLR4−/−, or MyD88−/− mice (CD45.2 alloantigen), which were then injected with soluble TLR ligands (Pam3CSK4, LPS, or ODN, respectively). As recipient mouse cells do not recognize the TLR ligands injected, interference by soluble mediators secreted by recipient cells is negligible. Transplanted cells were detected in the spleen and bone marrow of recipient mice, and in response to soluble TLR ligands, cells differentiated preferentially to Mph. These results show, for the first time, that HSPCs may be directly stimulated by TLR agonists in vivo, and that the engagement of these receptors induces differentiation toward Mph. Therefore, HSPCs may sense pathogen or pathogen-derived products directly during infection, inducing a rapid generation of cells of the innate immune system.
Mechanical properties of talc‐ and (calcium carbonate)‐filled poly(vinyl chloride) hybrid composites
Authors: Tuen Bee Soo , Hassan Azman , Abu Bakar Aznizam
Published: April 2012

The main objective of this study was to investigate and compare the mechanical properties of poly(vinyl chloride) (PVC) composites filled with calcium carbonate (CaCO3), talc, and talc/CaCO3. Talc and CaCO3 with different grades were incorporated into the PVC matrix. To produce the composites, the PVC resin, fillers, and other additives were first dry‐blended by using a laboratory mixer before being milled into sheets in a two‐roll mill. Test specimens were prepared by compression molding, after which the mechanical properties of the composites were determined. Single and hybrid filler loadings used were fixed at 30 phr (parts per hundred parts of resin). Talc‐filled composite showed the highest flexural modulus and the lowest impact strength, whereas uncoated, ground, 1‐μm CaCO3 (SM 90) showed optimum properties in terms of impact strength and flexural modulus among all grades of CaCO3. It was selected to combine with talc at different ratios in the hybrid composites. The impact strength of the hybrid composites gradually increased with increasing SM 90 content, but the flexural and tensile properties showed an opposite behavior. Hybrid (10 phr talc):(20 phr SM 90)‐filled PVC composite reached a synergistic hybridization with balanced properties in impact strength, as well as flexural and tensile properties. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers
Development of semitransparent wood‐polymer composites
Authors: Dias Paulo A.N. , Alves José A.C. , Fagg Duncan Paul , Reis Marco S. , Gil Maria H.
Published: April 2012

A new material has been developed consisting of pieces of wood embedded within a matrix of acrylic polymer, resulting in a transparent or semitransparent wood‐based product. This material presents quite appealing aesthetic features, thereby opening new possibilities for decorative applications. Because acrylic and methacrylic monomers are in the liquid state at room temperature, it is possible to introduce wood (in the current case, walnut wood) into a mixture of acrylic (hydroxypropyl acrylate) and/or methacrylic monomers (methyl methacrylate and 2‐hydroxyethyl methacrylate) along with a plasticizer (dioctyl phthalate) in the presence of a chemical initiator (benzoyl peroxide). A transparent polymeric matrix with dispersed wood is then obtained through bulk free‐radical polymerization. Introducing this reaction mixture along with pieces of wood into a mold results in a wood‐polymer composite. A 24−1 experimental fractional factorial design was implemented to study the importance of the composition of these materials on several relevant properties. The sheets produced were characterized by tensile testing, dynamic mechanical thermal analysis, thermal gravimetric analysis, and heat deflection temperature. The models obtained for predicting each property pointed to valuable insights regarding the influential constituents. In particular, our results suggested that monomers to be used in future applications of this material should be selected in terms of their cost and the desired flexibility for the final product, not in terms of their polarity. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers
Application of a high‐resolution animal‐borne remote video camera with global positioning for wildlife study: Observations on the secret lives of woodland caribou
Authors: Thompson Ian D. , Bakhtiari Mehdi , Rodgers Arthur R. , Baker James A. , Fryxell John M. , Iwachewski Edward
Published: April 2012

For many species of animals, obtaining basic life‐history data is difficult and even some common aspects, such as diet choice, remain unknown. To overcome this problem, we deployed what is, to our knowledge, the first successful application of a terrestrial high‐resolution animal‐borne video camera with on‐board long‐term recording and an associated Global Positioning (GPS) unit. Five cameras recorded video and audio and associated GPS locations of woodland caribou (Rangifer tarandus caribou) activities during 20 weeks from March to July 2011, although the units can run for >36 weeks depending on the rate of data collection. About 6% of videos were unusable because of fogging or snow on the lens, and clarity of plant images, especially ground covers, was a problem in a few of the files but overall quality of the videos was high and identification of diet by plant species can be achieved. We present a sample of data on several aspects of previously unknown behaviors of woodland caribou from boreal forests in central Canada, including parturition and diet selection to the level of individual plant species, to illustrate the capability of these units for improving our understanding of the behaviors of large elusive animals. © 2012 The Wildlife Society.