bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of voltage sweep direction on the performance evaluation of P3HT : PCBM solar cells
Authors: Kumar Pankaj , Sharma Abhishek , Singh Dwijendra Pratap
Published: April 2012

Investigations on the effect of direction of voltage sweeps, on the current density–voltage (J–V) characteristics in polymer bulk‐heterojunction solar cells, based on the blend of poly(3‐hexylthiophene) (P3HT) and phenyl [6,6] C61 butyric acid methyl ester (PCBM), are reported with time. On the freshly prepared device, the direction of the voltage sweep did not have any effect; however, as the device started degrading, the change in direction of the voltage sweep resulted into different characteristics. Analysis beyond complete degradation, when all the photovoltaic parameters reduced to zero, revealed some interesting results. The J–V characteristics, measured with voltage sweep from −ve to +ve voltage, both in the dark and under illumination, were observed to pass through the second quadrant. On the other hand, with the change in the direction of voltage sweep, viz. from +ve to −ve voltage, the characteristics both in the dark and under illumination passed through the fourth quadrant. These results have been explained on the basis of polarization of the degraded active layer due to applied external voltage. This is an important effect and is observed to depend on the applied voltages during performance evaluation and becomes more prominent with time. This effect puts a question mark on the correctness of the method for calculation of the parameters of a degraded device. Studies on degradation of P3HT : PCBM solar cells showed that both the short circuit current density (Jsc) and the power conversion efficiency (η) decay exponentially, whereas the open circuit voltage (Voc) decays almost linearly with time. Copyright © 2012 John Wiley & Sons, Ltd.
Diffusion‐free high efficiency silicon solar cells
Authors: Prajapati Victor , Janssens Tom , John Joachim , Poortmans Jef , Mertens Robert
Published: April 2012

Traditional POCl3 diffusion is performed in large diffusion furnaces heated to ~850 C and takes an hour long. This may be replaced by an implant and subsequent 90‐s rapid thermal annealing step (in a firing furnace) for the fabrication of p‐type passivated emitter rear contacted silicon solar cells. Implantation has long been deemed a technology too expensive for fabrication of silicon solar cells, but if coupled with innovative process flows as that which is mentioned in this paper, implantation has a fighting chance. An SiOx/SiNy rear side passivated p‐type wafer is implanted at the front with phosphorus. The implantation creates an inactive amorphous layer and a region of silicon full of interstitials and vacancies. The front side is then passivated using a plasma‐enhanced chemical vapor deposited SiNxHy. The wafer is placed in a firing furnace to achieve dopant activation. The hydrogen‐rich silicon nitride releases hydrogen that is diffused into the Si, the defect rich amorphous front side is immediately passivated by the readily available hydrogen; all the while, the amorphous silicon recrystallizes and dopants become electrically active. It is shown in this paper that the combination of this particular process flow leads to an efficient Si solar cell. Cell results on 160‐µm thick, 148.25‐cm2 Cz Si wafers with the use of the proposed traditional diffusion‐free process flow are up to 18.8% with a Voc of 638 mV, Jsc of 38.5 mA/cm2, and a fill factor of 76.6%. Copyright © 2012 John Wiley & Sons, Ltd.
Synthesis and properties of star polymers with a C5‐symmetric bowl‐shaped aromatic core
Authors: Stuparu Mihaiela C.
Published: April 2012

We report the synthesis and properties of star polymers with a C5‐symmetric aromatic core. For this, corannulene‐based penta‐substituted polymerization initiators were synthesized. These initiators were then used to polymerize cyclic ester and styrenic monomers via ring opening polymerization and free radical polymerization methods, respectively. Preliminary results suggest that these novel polymers can interact with fullerene, C60, and the degree of interaction can be tuned by the chemical nature of the solvent. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Hyperbranched photo responsive and liquid crystalline azo‐siloxane polymers synthesized by click chemistry
Authors: Pandey Someshwarnath , Mishra Sarada P. , Kolli Balakrishna , Kanai Tapan , Samui Asit B.
Published: April 2012

Three new types of hyperbranched photoactive liquid crystalline siloxane polymers containing azo moieties were synthesized using click chemistry methodology. The polymers were soluble in most of the polar solvents like chloroform, tetrahydrofuran, dimethylformamide, dimethyl sulphoxide and dichloromethane. The molecular weights of the polymers were in the range of 9000–12,000 g mol−1. The trans‐cis photoisomerization of the polymer were studied both under UV radiation and dark. The isomerization rate constants were found to be in the range of 0.7–1.4 × 10−2 sec−1 and 7.0 × −2.5 × 10−5 sec−1. The thermotropic behavior of the polymers was studied by using polarizing optical microscopy and differential scanning calorimetry, respectively. The polymers P1 and P2 showed liquid crystalline texture characteristic of nematic phase. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Biodegradable stereocomplex materials of polylactide‐grafted dextran exhibiting soft and tough properties in dry and wet states
Authors: Nagahama Koji , Shimizu Keiko , Ichimura Shunsuke , Takahashi Akihiro , Ouchi Tatsuro , Ohya Yuichi
Published: April 2012

Water‐swellable biodegradable materials exhibiting mechanically tenacious and tough characters in the wet state were prepared by a simple blend of two enantiomeric polylactide‐grafted dextran copolymers (Dex‐g‐PLLA and Dex‐g‐PDLA). DSC and WAXD analyses demonstrated the formation of SC crystals in the copolymer blend films. SC blend films showed lamellar‐type microphase‐separated structures. When swollen with water, these blend films showed the same level of tensile strengths and Young's modulus as the films in the dry state. SC blend films degraded gradually over a month under physiological conditions with a degradation rate faster than the corresponding Dex‐g‐PLLA films. The SC‐forming enantiomeric mixture of polylactide‐grafted polysaccharides should be a good candidate for an implantable biocompatible material exhibiting favorable mechanical properties and degradation behavior. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Preparation of poly(acrylic acid)‐b‐polystyrene by two‐step atom transfer radical polymerization in supercritical carbon dioxide
Authors: Minami Hideto , Tanaka Atsushi , Kagawa Yasuyuki , Okubo Masayoshi
Published: April 2012

It is known that it is difficult to polymerize carboxylic acid‐based monomer by atom transfer radical polymerization (ATRP) in polar solvents due to the protonation of ligand caused by acidic dissociation of the monomer. In this study, precipitation reverse ATRP of acrylic acid (AA) was carried out in supercritical carbon dioxide (scCO2), which is a nonpolar solvent to dissolve transition metal complexes, at 30 MPa and 45 °C. The polymerization proceeded smoothly and the conversion reached 86% for 3 h. After vending of scCO2, a dry poly(acrylic acid) (PAA) powder was obtained. Weight‐average molecular weight and polydispersity of the methylated PAA, which were measured by gel‐permeation chromatography after methyl esterification, were 3.5 × 104 and 2.07, respectively, indicating that the precipitation reverse ATRP proceeded with a bad control manner. However, chain extension of the methylated PAA with styrene was possible by ATRP in a bulk system. Moreover, PAA‐b‐polystyrene was successfully prepared in scCO2 directly by two‐step ATRP, although its molecular weight distribution was broad. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Associations of obesity and asthma with functional exercise capacity in urban minority adolescents
Authors: Rastogi Deepa , Khan Unab I. , Isasi Carmen R. , Coupey Susan M.
Published: April 2012

Purpose

To examine the independent association of asthma and obesity and of their co‐existence with functional exercise capacity among urban adolescents.

Methods

One hundred eighteen Hispanic‐ and African‐American adolescents including 33 obese asthmatics, 18 normal‐weight asthmatics, 38 obese non‐asthmatics, and 29 normal‐weight non‐asthmatics underwent anthropometric measures, 6‐minute walk test (6MWT) as measure of functional exercise capacity and spirometry as measure of pulmonary function. The 6‐minute walk distance (6MWD) was compared between the four study groups. The association of 6MWD with measures of lower airway obstruction, and measures of adiposity was assessed.

Results

The 6MWD was lower among the obese groups with the least distance covered by the obese asthmatic group (P = 0.02). In the obese asthmatic group, there was a negative correlation between 6MWD and body mass index (BMI) (r = −0.35, P = 0.03), but no association was noted with percent‐predicted forced expiratory volume in the 1st second (FEV1; r = 0.07, P = 0.70). Conversely, the 6MWD correlated with FEV1 among normal‐weight asthmatics (r = 0.45, P = 0.04) and normal‐weight non‐asthmatics (r = 0.4, P = 0.03), but was not associated with BMI in either of the two groups. After adjusting for age, height, gender, and ethnicity, BMI was noted to be a significant predictor (β −2.76, 95% CI −4.77 to −0.76, P < 0.01) of the 6MWD among the obese while percent predicted FEV1 (β 1.87, 95% CI 0.28–3.45, P = 0.02) was a significant predictor among the normal‐weight participants.

Conclusions

Our findings suggest that among urban minority obese asthmatic adolescents, functional exercise capacity was associated with obesity, rather than pulmonary function. Pediatr Pulmonol. 2012. 47:1061–1069. © 2012 Wiley Periodicals, Inc.
Developmental and genetic aspects of congenital diaphragmatic hernia
Authors: Veenma D.C.M. , de Klein A. , Tibboel D.
Published: April 2012

Congenital diaphragmatic hernia (CDH) is a frequent occurring cause of neonatal respiratory distress and occurs 1 in every 3,000 liveborns. Ventilatory support and pharmaceutical treatment of the co‐occurring lung hypoplasia and pulmonary hypertension are insufficient in, respectively, 20% of isolated cases and 60% of complex ones leading to early perinatal death. The exact cause of CDH remains to be identified in the majority of human CDH patients and prognostic factors predicting treatment refraction are largely unknown. Their identification is hampered by the multifactorial and heterogenic nature of this congenital anomaly. However, application of high‐resolution molecular cytogenetic techniques to patients' DNA now enables detection of chromosomal aberrations in 30% of the patients. Furthermore, recent insights in rodent embryogenesis pointed to a specific disruption of the early mesenchymal structures in the primordial diaphragm of CDH‐induced offspring. Together, these data allowed for the introduction of new hypotheses on CDH pathogenesis, although many issues remain to be resolved. In this review, we have combined these new insights and remaining questions on diaphragm pathogenesis with a concise overview of the clinical, embryological, and genetic data available. Pediatr Pulmonol. 2012; 47:534–545. © 2012 Wiley Periodicals, Inc.
The fraction of NO in exhaled air and estimates of alveolar NO in adolescents with asthma: Methodological aspects
Authors: Heijkenskjöld‐Rentzhog Charlotte , Alving Kjell , Kalm‐Stephens Pia , Lundberg Jon O , Nordvall Lennart , Malinovschi Andrei
Published: April 2012

Rationale

This study investigated the oral contribution to exhaled NO in young people with asthma and its potential effects on estimated alveolar NO (CalvNO), a proposed marker of inflammation in peripheral airways. Secondary aims were to investigate the effects of various exhalation flow‐rates and the feasibility of different proposed adjustments of (CalvNO) for trumpet model and axial diffusion (TMAD).

Methods

Exhaled NO at flow rates of 50–300 ml/sec, and salivary nitrite was measured before and after antibacterial mouthwash in 29 healthy young people (10–20 years) and 29 with asthma (10–19 years). CalvNO was calculated using the slope–intercept model with and without TMAD adjustment.

Results

Exhaled NO at 50 ml/sec decreased significantly after mouthwash, to a similar degree in asthmatic and healthy subjects (8.8% vs. 9.8%, P = 0.49). The two groups had similar salivary nitrite levels (56.4 vs. 78.4 µM, P = 0.25). CalvNO was not significantly decreased by mouthwash. CalvNO levels were similar when flow‐rates between 50–200 or 100–300 ml/sec were used (P = 0.34 in asthmatics and P = 0.90 in healthy subjects). A positive association was found between bronchial and alveolar NO in asthmatic subjects and this disappeared after the TMAD‐adjustment. Negative TMAD‐adjusted CalvNO values were found in a minority of the subjects.

Conclusions

Young people with and without asthma have similar salivary nitrite levels and oral contributions to exhaled NO and therefore no antibacterial mouthwash is necessary in routine use. TMAD corrections of alveolar NO could be successfully applied in young people with asthma and yielded negative results only in a minority of subjects. Pediatr Pulmonol. 2012. 47:941–949. © 2012 Wiley Periodicals, Inc.
A Modified Type‐12 Impact Sensitivity Test Apparatus for Explosives
Authors: Phillips Jason J.
Published: April 2012

This investigation is to improve the Type‐12 impact sensitivity test apparatus through the merging of basic split‐Hopkinson pressure bar principles with existing impact sensitivity testing methods. This is accomplished mainly through the addition of resistance strain gage equipment. Upon completion of the modifications to the apparatus, incident pressure waves created by impact are recorded, as well as sharp pressure releases suspected to be caused by rapid mechanical failure of energetic material samples. To solve data acquisition issues during the initial testing attempts with the modified equipment, the Type‐12 tooling is further adapted by installing a high‐density polyethylene (HDPE) bushing through which the striker bar is inserted. A series of sensitivity tests are then conducted using RDX to determine if this alteration affected the normal operation of the instrument. It is found that this modification to the apparatus creates a 46 % reduction in the standard deviation of H50 results in comparison to the standard tooling.
A “Link‐Psi” strategy using crosslinking indicates that the folding transition state of ubiquitin is not very malleable
Authors: Shandiz Ali T. , Baxa Michael C. , Sosnick Tobin R.
Published: April 2012

Using a combined crosslinking‐ψ analysis strategy, we examine whether the structural content of the transition state of ubiquitin can be altered. A synthetic dichloroacetone crosslink is first introduced across two β strands. Whether the structural content in the transition state ensemble has shifted towards the region containing the crosslink is probed by remeasuring the ψ value at another region (ψ identifies the degree to which an inserted bi‐Histidine metal ion binding site is formed in the transition state). For sites around the periphery of the obligate transition state nucleus, we find that the resulting changes in ψ values are near or at our detection limit, thereby indicating that the structural content of the transition state has not measurably changed upon crosslinking. This work demonstrates the utility of the simultaneous application of crosslinking and ψ‐analysis for examining potential transition state heterogeneity in globular proteins.
Template‐based structure prediction and classification of transcription factors in Arabidopsis thaliana
Authors: Lu Tao , Yang Yuedong , Yao Bo , Liu Song , Zhou Yaoqi , Zhang Chi
Published: April 2012

Transcription factors (TFs) play important roles in plants. However, there is no systematic study of their structures and functions of most TFs in plants. Here, we performed template‐based structure prediction for all TFs in Arabidopsis thaliana, with their full‐length sequences as well as C‐terminal and N‐terminal regions. A total of 2918 model structures were obtained with a high confidence score. We find that TF families employ only a smaller number of templates for DNA‐binding domains (DBD) but a diverse number of templates for transcription regulatory domains (TRD). Although TF families are classified according to DBD, their sizes have a significant correlation with the number of unique non‐DNA‐binding templates employed in the family (Pearson correlation coefficient of 0.74). That is, the size of TF family is related to its functional diversity. Network analysis reveals new connections between TF families based on shared TRD or DBD templates; 81% TF families share DBD and 67% share TRD templates. Two large fully connected family clusters in this network are observed along with 69 island families. In addition, 25 genes with unknown functions are found to be DNA‐binding and/or TF factors according to predicted structures. This work provides a global view of the classification of TFs based on their DBD or TRD templates, and hence, a deeper understanding of DNA‐binding and regulatory functions from structural perspective. All structural models of TFs are deposited in the online database for public usage at http://sysbio.unl.edu/AthTF.
Active site residues critical for flavin binding and 5,6‐dimethylbenzimidazole biosynthesis in the flavin destructase enzyme BluB
Authors: Yu Ta‐Yi , Mok Kenny C. , Kennedy Kristopher J. , Valton Julien , Anderson Karen S. , Walker Graham C. , Taga Michiko E.
Published: April 2012

The “flavin destructase” enzyme BluB catalyzes the unprecedented conversion of flavin mononucleotide (FMN) to 5,6‐dimethylbenzimidazole (DMB), a component of vitamin B12. Because of its unusual chemistry, the mechanism of this transformation has remained elusive. This study reports the identification of 12 mutant forms of BluB that have severely reduced catalytic function, though most retain the ability to bind flavin. The “flavin destructase” BluB is an unusual enzyme that fragments the flavin cofactor FMNH2 in the presence of oxygen to produce 5,6‐dimethylbenzimidazole (DMB), the lower axial ligand of vitamin B12 (cobalamin). Despite the similarities in sequence and structure between BluB and the nitroreductase and flavin oxidoreductase enzyme families, BluB is the only enzyme known to fragment a flavin isoalloxazine ring. To explore the catalytic residues involved in this unusual reaction, mutants of BluB impaired in DMB biosynthesis were identified in a genetic screen in the bacterium Sinorhizobium meliloti. Of the 16 unique point mutations identified in the screen, the majority were located in conserved residues in the active site or in the unique “lid” domain proposed to shield the active site from solvent. Steady‐state enzyme assays of 12 purified mutant proteins showed a significant reduction in DMB synthesis in all of the mutants, with eight completely defective in DMB production. Ten of these mutants have weaker binding affinities for both oxidized and reduced FMN, though only two have a significant effect on complex stability. These results implicate several conserved residues in BluB's unique ability to fragment FMNH2 and demonstrate the sensitivity of BluB's active site to structural perturbations. This work lays the foundation for mechanistic studies of this enzyme and further advances our understanding of the structure‐function relationship of BluB.
The bacterial outer membrane β‐barrel assembly machinery
Authors: Kim Kelly H. , Aulakh Suraaj , Paetzel Mark
Published: April 2012

β‐Barrel proteins found in the outer membrane of Gram‐negative bacteria serve a variety of cellular functions. Proper folding and assembly of these proteins are essential for the viability of bacteria and can also play an important role in virulence. The β‐barrel assembly machinery (BAM) complex, which is responsible for the proper assembly of β‐barrels into the outer membrane of Gram‐negative bacteria, has been the focus of many recent studies. This review summarizes the significant progress that has been made toward understanding the structure and function of the bacterial BAM complex.
The interface of protein structure, protein biophysics, and molecular evolution
Authors: Liberles David A. , Teichmann Sarah A. , Bahar Ivet , Bastolla Ugo , Bloom Jesse , Bornberg‐Bauer Erich , Colwell Lucy J. , de Koning A. P. Jason , Dokholyan Nikolay V. , Echave Julian , Elofsson Arne , Gerloff Dietlind L. , Goldstein Richard A. , Grahnen Johan A. , Holder Mark T. , Lakner Clemens , Lartillot Nicholas , Lovell Simon C. , Naylor Gavin , Perica Tina , Pollock David D. , Pupko Tal , Regan Lynne , Roger Andrew , Rubinstein Nimrod , Shakhnovich Eugene , Sjölander Kimmen , Sunyaev Shamil , Teufel Ashley I. , Thorne Jeffrey L. , Thornton Joseph W. , Weinreich Daniel M. , Whelan Simon
Published: April 2012

Abstract The interface of protein structural biology, protein biophysics, molecular evolution, and molecular population genetics forms the foundations for a mechanistic understanding of many aspects of protein biochemistry. Current efforts in interdisciplinary protein modeling are in their infancy and the state‐of‐the art of such models is described. Beyond the relationship between amino acid substitution and static protein structure, protein function, and corresponding organismal fitness, other considerations are also discussed. More complex mutational processes such as insertion and deletion and domain rearrangements and even circular permutations should be evaluated. The role of intrinsically disordered proteins is still controversial, but may be increasingly important to consider. Protein geometry and protein dynamics as a deviation from static considerations of protein structure are also important. Protein expression level is known to be a major determinant of evolutionary rate and several considerations including selection at the mRNA level and the role of interaction specificity are discussed. Lastly, the relationship between modeling and needed high‐throughput experimental data as well as experimental examination of protein evolution using ancestral sequence resurrection and in vitro biochemistry are presented, towards an aim of ultimately generating better models for biological inference and prediction.
Hemostatic gelatin sponge is a superior matrix to matrigel for establishment of LNCaP human prostate cancer in nude mice
Authors: Cui Lingling , Chen Pingping , Tan Zongqing , Li Wenjie , Dong Zhongyun
Published: April 2012

BACKGROUND

Matrigels, solubilized basement membrane preparations, are often used to support tumor development in animal models. However, tumors formed by a mixture of tumor cells and Matrigel may vary significantly. The purpose of this study was to compare tumor development and growth of LNCaP human prostate cancer cells mixed with Matrigel or in gelatin sponges.

METHODS

LNCaP cells were mixed with Matrigel or absorbed into VETSPON, a gelatin sponge, and inoculated into the subcutis of nude mice. Tumor incidence and growth rate were determined. Gene expression and cell growth and survival in tumor lesions were evaluated by immunohistochemistry (IHC), immunoblotting, and RT‐PCR.

RESULTS

All mice (12/12) inoculated with LNCaP cells in VETSPON produced tumors, compared to 70% (19/27) of mice injected with the cells with Matrigel. Tumor volume also varied less with VETSPON implants. No significant differences were observed in gene expression, cell growth, apoptosis, and microvessel density in tumors established from the two types of implants. However, in samples collected on days 1 and 4, more cells in Matrigel implants than those in VETSPON implants were stained positive for cleaved‐caspase 3 and ‐PARP1. Expression of VEGF‐A, HIF‐1α, and Bcl‐2 was elevated in the early VETSPON implants.

CONCLUSION

These data indicate that VETSPON promotes tumor cell survival at the early stage of implantation and suggest that the gelatin sponge is superior to Matrigel in supporting development and progression of human prostate cancer in nude mice. This model should be useful for preclinical studies in nude mice using LNCaP cells. Prostate 72:1669–1677, 2012. © 2012 Wiley Periodicals, Inc.
Low dosed interferon alpha augments the anti‐tumor potential of histone deacetylase inhibition on prostate cancer cell growth and invasion
Authors: Hudak Lukasz , Tezeeh Patrick , Wedel Steffen , Makarević Jasmina , Juengel Eva , Tsaur Igor , Bartsch Georg , Wiesner Christoph , Haferkamp Axel , Blaheta Roman A.
Published: April 2012

We evaluated whether low‐dosed interferon alpha (IFNa) may augment the anti‐tumor potential of the histone deacetylase (HDAC)‐inhibitor valproic acid (VPA) on prostate cancer cells in vitro and in vivo. PC‐3, DU‐145, or LNCaP prostate cancer cells were treated with VPA (1 mM), IFNa (200 U/ml), or with the VPA‐IFNa combination. Tumor cell growth, cell cycle progression, and cell cycle regulating proteins were then investigated by the MTT assay, flow cytometry, and western blotting. Tumor cell adhesion to endothelium or to immobilized extracellular matrix proteins, as well as migratory properties of the cells, were evaluated. Integrin α and β adhesion molecules and alterations of cell signaling pathways were analyzed. Finally, effects of the drug treatment on prostate cancer growth in vivo were determined in the NOD/SCID mouse model. VPA reduced tumor cell adhesion, migration, and growth in vitro. A much stronger anti‐cancer potential was evoked by the VPA‐IFNa combination, although IFNa in itself did not block growth or adhesion. The same effect was seen when tumor growth was evaluated in vivo. Molecular analysis revealed distinct elevation of histone H3 acetylation caused by VPA which was further up‐regulated by VPA‐IFNa, whereas IFNa alone did not alter H3 acetylation. The combinatorial benefit became obvious in Akt phosphorylation, p21 and p27 and integrin α1, α3, and β1 expression. Application of low‐dosed IFNa to a VPA based regimen profoundly boosts the anti‐tumor properties of VPA. The combined use of VPA and low‐dosed IFNa may therefore be an innovative option in treating advanced prostate cancer. Prostate 72:1719–1735, 2012. © 2012 Wiley Periodicals, Inc.
Quantitative impact assessment of spray coverage and pest behavior on contact pesticide performance
Authors: Martini Xavier , Kincy Natalie , Nansen Christian
Published: April 2012

BACKGROUND: Standard procedures for evaluation of pesticide performance do not take into account pest behavioral response or incomplete spray coverage. In this study, a series of laboratory experiments was conducted with two non‐systemic miticides (propargite and hexythiazox) applied to cotyledon cotton plants, which were subsequently infested with spider mites. The results of these laboratory experiments are discussed through a comprehensive pest population dynamics model.

RESULTS: When cotton leaves were submerged in miticide solutions, both miticides provided effective control of spider mites. In a two‐choice test it was demonstrated that propargite was repellent to spider mites, but not hexythiazox. Finally, the spray coverage on cotton plants was varied, and, for both miticides, significantly positive relationships between spray coverage and spider mite mortality were shown. However, propargite required higher spray coverage (20%) than hexythiazox (10%) to control spider mites. A theoretical model showed that, without repellency, the pesticide performance is positively correlated with target pest mobility. If the pesticide is repellent, the probability of exposure decreases, especially for a less mobile pest.

CONCLUSION: With an experimental and theoretical modeling approach, it was demonstrated how the combination of behavioral avoidance and low spray coverage can markedly reduce pesticide performance. Copyright © 2012 Society of Chemical Industry
Structure–activity relationships of eugenol derivatives against Aedes aegypti (Diptera: Culicidae) larvae
Authors: Barbosa Juliana DF , Silva Viviane B , Alves Péricles B , Gumina Giuseppe , Santos Roseli LC , Sousa Damião P , Cavalcanti Sócrates CH
Published: April 2012

BACKGROUND: Dengue fever is a severe public health problem for several countries. In order to find effective larvicides to aid control programs, the structure‐activity relationships of eugenol derivatives against Aedes aegypti (Diptera: Culicidae) larvae were evaluated. Additionally, the composition and larvicidal activity of Syzygium aromaticum essential oil was assessed.

RESULTS: Four compounds representing 99.05% of S. aromaticum essential oil have been identified. The essential oil was active against Ae. aegypti larvae (LC50 = 62.3 and 77.0 ppm, field‐collected and Rockefeller larvae respectively). The larvicidal activity of eugenol, the major compound of the essential oil, was further evaluated (LC50 = 93.3 and 71.9 ppm, field‐collected and Rockefeller larvae respectively). The larvicidal activity and structure‐activity relationships of synthetic derivatives of eugenol were also assessed. The larvicidal activity of the derivatives varied between 62.3 and 1614.9 ppm. Oxidation of eugenol allylic bond to a primary alcohol and removal of the phenolic proton resulted in decreased potency. However, oxidation of the same double bond in 1‐benzoate‐2‐methoxy‐4‐(2‐propen‐1‐yl)‐phenol resulted in increased potency.

CONCLUSION: Structural characteristics were identified that may contribute to the understanding of the larvicidal activity of phenylpropanoids. The present approach may help future work in the search for larvicidal compounds. Copyright © 2012 Society of Chemical Industry
Composition and biological activity of essential oils against Metopolophium dirhodum (Hemiptera: Aphididae) cereal crop pest
Authors: Sánchez Chopa Carolina , Descamps Lilian R
Published: April 2012

BACKGROUND: Natural pesticides based on plant essential oils may represent alternative crop protectants. This study analysed the chemical constituents and bioactivities of essential oils from Schinus areira L., Rosmarinus officinalis L. and Tagetes terniflora Kunth against winged and wingless adults of Metopolophium dirhodum (Walk.).

RESULTS: The major component of S. areira was α‐phellandrene, that of R. officinalis was 1,8‐cineole and that of T. terniflora was cis‐ocimene. Rosemary essential oil was more effective than the others in immersion method tests. In contact toxicity, the rosemary oil was the most toxic to wingless adults and the S. areira leaf oil was the most toxic to winged adults. All the EOs produced some degrees of repellency in adults and effects on the reproduction and demographic parameters.

CONCLUSION: These results showed that the essential oils from S. areira, R. officinalis and T. terniflora could be used as an alternative in the management of M. dirhodum. Copyright © 2012 Society of Chemical Industry
Spectral selection of spatial modes in edge‐emitting lasers
Authors: Savenko I. G. , Gordeev N. Yu. , Iorsh I. V. , Kaliteevski M. A. , Maximov M. V. , Zhukov A. E.
Published: April 2012

We have analytically considered the way of high‐order lateral modes suppression in edge‐emitting lasers by integrating into the cavity a spectral filter based on the set of etched micrometer‐size features. We have found optimal features location and numerically calculated their spectral and loss properties for single‐mode laser and investigated the effect robustness against size fluctuation (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of surface analysis methods to nanomaterials: summary of ISO/TC 201 technical report: ISO 14187:2011 – surface chemical analysis – characterization of nanomaterials
Authors: Baer D. R.
Published: April 2012

The ISO technical report 14187 provides an introduction to (and examples of) the information that can be obtained about nanostructured materials by using surface analysis tools. In addition, both general issues and challenges associated with characterizing nanostructured materials and the specific opportunities and challenges associated with individual analytical methods are identified. As the size of objects or components of materials approaches a few nanometers, the distinctions among ‘bulk’, ‘surface’, and ‘particle’ analysis blur. This technical report focuses on issues specifically relevant to surface chemical analysis of nanostructured materials. The report considers a variety of analysis methods but focuses on techniques that are in the domain of ISO/TC 201 including Auger electron spectroscopy, X‐ray photoelectron spectroscopy, secondary ion mass spectrometry, and scanning probe microscopy. Measurements of nanoparticle surface properties such as surface potential that are often made in a solution are not discussed. Copyright © 2012 John Wiley & Sons, Ltd.
Host country uncertainty, intra‐MNC production shifts, and subsidiary performance
Authors: Lee Seung‐Hyun , Song Sangcheol
Published: April 2012

This study examines whether or not production shifts occur among the foreign subsidiaries of multinational corporations (MNCs) under the influence of differing macroeconomic conditions in their host countries. This study compares intra‐MNC production shifts under the influence of exchange rate changes across different host countries. Our findings indicate that the increase of a subsidiary's production at the time of its host country currency depreciation decreases the production of other subsidiaries within the same MNC network. Our empirical evidence also shows that MNC subsidiaries that engage in production shifts with other affiliated subsidiaries command a higher performance. Copyright © 2012 John Wiley & Sons, Ltd.
Studying Polymer/Fullerene Intermixing and Miscibility in Laterally Patterned Films with X‐Ray Spectromicroscopy
Authors: He Xiaoxi , Collins Brian A. , Watts Benjamin , Ade Harald , McNeill Christopher R.
Published: April 2012

Films of the fullerene derivatives [6,6]‐phenyl‐C61‐butyric acid methyl ester (PC61BM) and [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) are patterned on silicon nitride membranes using photolithography to study, with X‐ray spectromicroscopy, the lateral, solid‐state diffusion of fullerene derivatives into conjugated polymer films. After patterning of the fullerene film, a film of conjugated polymer is laminated on top and the structure is annealed in order to study lateral intermixing and facilitate measurement of fullerene miscibility. Lateral intermixing of polymer and fullerene readily occurs for poly(2,5‐bis(3‐tetradecylthiophen‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT) and regiorandom poly(3‐hexylthiophene) (RRa‐P3HT). A 42 wt.% miscibility of PC61BM in PBTTT is measured, while miscibilities of 20 and 41 wt.% are measured for PC61BM and PC71BM, respectively, in RRa‐P3HT, thereby demonstrating a significant difference in the miscibilities of these two fullerene derivatives. For regioregular poly(3‐hexylthiophene) (RR‐P3HT), incomplete lateral intermixing of fullerene and RR‐P3HT is observed with PCBM crystallite formation competing with the lateral diffusion of PCBM molecules into the polymer film.
IGF-II Promotes Stemness of Neural Restricted Precursors
Authors: Ziegler Amber N. , Schneider Joel S. , Qin Mei , Tyler William A. , Pintar John E. , Fraidenraich Diego , Wood Teresa L. , Levison Steven W.
Published: April 2012

Insulin-like growth factor (IGF)-I and IGF-II regulate brain development and growth through the IGF type 1 receptor (IGF-1R). Less appreciated is that IGF-II, but not IGF-I, activates a splice variant of the insulin receptor (IR) known as IR-A. We hypothesized that IGF-II exerts distinct effects from IGF-I on neural stem/progenitor cells (NSPs) via its interaction with IR-A. Immunofluorescence revealed high IGF-II in the medial region of the subventricular zone (SVZ) comprising the neural stem cell niche, with IGF-II mRNA predominant in the adjacent choroid plexus. The IGF-1R and the IR isoforms were differentially expressed with IR-A predominant in the medial SVZ, whereas the IGF-1R was more abundant laterally. Similarly, IR-A was more highly expressed by NSPs, whereas the IGF-1R was more highly expressed by lineage restricted cells. In vitro, IGF-II was more potent in promoting NSP expansion than either IGF-I or standard growth medium. Limiting dilution and differentiation assays revealed that IGF-II was superior to IGF-I in promoting stemness. In vivo, NSPs propagated in IGF-II migrated to and took up residence in periventricular niches while IGF-I-treated NSPs predominantly colonized white matter. Knockdown of IR or IGF-1R using shRNAs supported the conclusion that the IGF-1R promotes progenitor proliferation, whereas the IR is important for self-renewal. Q-PCR revealed that IGF-II increased Oct4, Sox1, and FABP7 mRNA levels in NSPs. Our data support the conclusion that IGF-II promotes the self-renewal of neural stem/progenitors via the IR. By contrast, IGF-1R functions as a mitogenic receptor to increase precursor abundance.

Disclosure of potential conflicts of interest is found at the end of this article.
Transduction of Neural Precursor Cells with TAT-Heat Shock Protein 70 Chaperone: Therapeutic Potential Against Ischemic Stroke after Intrastriatal and Systemic Transplantation
Authors: Doeppner Thorsten R. , Ewert Tobias A. S. , Tönges Lars , Herz Josephine , Zechariah Anil , ElAli Ayman , Ludwig Anna-Kristin , Giebel Bernd , Nagel Florian , Dietz Gunnar P. H. , Weise Jens , Hermann Dirk M. , Bähr Mathias
Published: April 2012

Novel therapeutic concepts against cerebral ischemia focus on cell-based therapies in order to overcome some of the side effects of thrombolytic therapy. However, cell-based therapies are hampered because of restricted understanding regarding optimal cell transplantation routes and due to low survival rates of grafted cells. We therefore transplanted adult green fluorescence protein positive neural precursor cells (NPCs) either intravenously (systemic) or intrastriatally (intracerebrally) 6 hours after stroke in mice. To enhance survival of NPCs, cells were in vitro protein-transduced with TAT-heat shock protein 70 (Hsp70) before transplantation followed by a systematic analysis of brain injury and underlying mechanisms depending on cell delivery routes. Transduction of NPCs with TAT-Hsp70 resulted in increased intracerebral numbers of grafted NPCs after intracerebral but not after systemic transplantation. Whereas systemic delivery of either native or transduced NPCs yielded sustained neuroprotection and induced neurological recovery, only TAT-Hsp70-transduced NPCs prevented secondary neuronal degeneration after intracerebral delivery that was associated with enhanced functional outcome. Furthermore, intracerebral transplantation of TAT-Hsp70-transduced NPCs enhanced postischemic neurogenesis and induced sustained high levels of brain-derived neurotrophic factor, glial cell line-derived neurotrophic factor, and vascular endothelial growth factor in vivo. Neuroprotection after intracerebral cell delivery correlated with the amount of surviving NPCs. On the contrary, systemic delivery of NPCs mediated acute neuroprotection via stabilization of the blood-brain-barrier, concomitant with reduced activation of matrix metalloprotease 9 and decreased formation of reactive oxygen species. Our findings imply two different mechanisms of action of intracerebrally and systemically transplanted NPCs, indicating that systemic NPC delivery might be more feasible for translational stroke concepts, lacking a need of in vitro manipulation of NPCs to induce long-term neuroprotection.

Disclosure of potential conflicts of interest is found at the end of this article.
Concurrent enrollment in lecture and laboratory enhances student performance and retention
Authors: Matz Rebecca L. , Rothman Edward D. , Krajcik Joseph S. , Banaszak Holl Mark M.
Published: April 2012

Laboratories have been a cornerstone in teaching and learning across multiple scientific disciplines for more than 100 years. At the collegiate level, science laboratories and their corresponding lectures are often offered as separate courses, and students may not be required to concurrently enroll in both. In this study, we provide evidence that enrolling in an introductory laboratory concurrently with the corresponding lecture course enhances learning gains and retention in comparison to students who enroll in the lecture alone. We examined the impact of concurrent versus nonconcurrent enrollment on 9,438 students' withdrawal rates from and final grades in the general chemistry lecture at the University of Michigan at Ann Arbor using multiple linear and binary logistic regression analyses, respectively, at a significance level of 0.05. We found that concurrent enrollment in the lecture and laboratory positively impacts (1) the odds of retention in the lecture by 2.2 times on average and (2) final lecture grades by up to 0.19 grade points on a 4.0 scale for the lowest‐scoring students according to university‐level mathematics and chemistry placement exam scores. These data provide important results for consideration by curriculum advisors and course planners at universities that do not require concurrent enrollment in general chemistry as well as other science courses. In the face of current budget cuts that threaten to shorten or eliminate laboratory experiences altogether at multiple educational levels, this study demonstrates the value of laboratories in promoting science learning and retention. © 2012 Wiley Periodicals, Inc. J Res Sci Teach 49: 659–682, 2012
Should great lakes city build a new power plant? How youth navigate socioscientific issues
Authors: Levine Rose Shari , Calabrese Barton Angela
Published: April 2012

There is a growing consensus that simply learning enough science to decipher public debates on socioscientific issues will not make citizens better equipped to handle the complex and ill‐structured problems these controversial issues present. This study highlights the interaction and complex interplay between youth authored and appropriated frames for making sense of socioscientific issues. To do so, we analyze how two middle‐school aged youth, in an after‐school program focused on green energy technologies, made sense of and took a stance on whether their city should build a new hybrid power plant over the course of a 13‐week unit. Using critical sociocultural perspectives on learning and qualitative case study, we examined how the two youth navigated the issue and the resources, scientific and otherwise, they leveraged in defining the problem spaces involved in whether their city should build a new power plant. Our findings indicate that the scientific knowledge youth brought with them and acquired over the course of the investigation influenced how they made sense of the issue, but their knowledge was deeply connected to a range of personal and public discourses that influenced how they defined the issue and why it mattered to them. In particular, it was through how they framed their range of knowledge and experiences that they were able to recognize the multi‐dimensional nature of the problem and propose complex solutions resonant with the science they understood. Our study offers conceptual tools for teaching and learning socioscientific issues. © 2012 Wiley Periodicals, Inc. J Res Sci Teach 49: 541–567, 2012
Verfügbarkeit von Metallrohstoffen für die Dünnschicht‐Photovoltaik
Authors: Liedtke Maren
Published: April 2012

Gallium, Tellur und Indium sind wichtige Rohstoffe für die Dünnschichttechnologien, für die ein steigender Bedarf prognostiziert wird. Sie kommen nur in geringer Konzentration in der Erdkruste vor und werden nur in geringen Mengen gewonnen bzw. technologisch eingesetzt. Die Gewinnung erfolgt als Beiprodukt im Zuge der Herstellung von Industriemetallen wie Aluminium, Kupfer oder Zink. Abbau und Aufbereitung der Hauptmetalle begrenzen daher die maximale Produktionskapazität dieser Spurenmetalle. Die weltweiten Gewinnungskapazitäten für Beiprodukte sind begrenzt, und das Potenzial ihrer Gewinnung wird aus wirtschaftlichen Gründen meist nicht ausgeschöpft. Die Primärproduktion von Beiprodukten kann durch eine erhöhte Gewinnung der Hauptprodukte und durch den Ausbau von Gewinnungskapazitäten innerhalb eines bestehenden Produktionsprozesses gesteigert werden. Eine weitere Möglichkeit bietet die Gewinnung aus bisher kaum genutzten Erzen sowie aus bergbaulichen und metallurgischen Reststoffen.
PECVDTM Coatings in Industrial Applications
Authors: Seaman Walter , Madocks John , Jochum Toni
Published: April 2012

The adoption of GPI's Linear PECVDTM process has accelerated over the last year. Several R&D and production reactor modules were installed at major companies and a turnkey in‐line system was completed. Through these installations, customers are confirming the superior deposition rate, uniformity and stability of Linear PECVDTM compared to reactive sputtering. Today Linear PECVDTM is being used to deposit oxide and nitride films on a variety of substrates. The films include SiO2, TiO2, Al22O3, SiN, ZnO, and SnO and the applications include multi‐layer AR coatings, single layer oxides and nitrides in combination with sputtered films, thin‐film solar coatings, barrier films, anti‐smudge coatings and TCO's. This progress demonstrates that GPI's Linear PECVDTM technology may soon displace reactive sputtering of oxides and nitrides for large area substrates in architectural glass, flat panel display and flexible web applications.
Optimization of protein models
Authors: Gront Dominik , Kmiecik Sebastian , Blaszczyk Maciej , Ekonomiuk Dariusz , Koliński Andrzej
Published: April 2012

Protein structure predictions, and experimentally derived protein structures, very often require certain structure improvement (refinement), which means bringing it closer to real, usually in vivo working conformations. In respect to the variety of protein models to be refined, computational optimization procedures could be divided into localized (applied to a small part of a structure) and global (whole structure). Generally speaking, the first problem is usually tractable, and the latter remains to be extremely challenging for systems larger then peptides or small proteins: optimization complexity and difficulty dramatically increase with the size of structures to be optimized. © 2012 John Wiley & Sons, Ltd.

This article is categorized under:

Molecular and Statistical Mechanics > Molecular Dynamics and Monte-Carlo Methods
New advances in metadynamics
Authors: Sutto Ludovico , Marsili Simone , Gervasio Francesco Luigi
Published: April 2012

Metadynamics is an algorithm for accelerating rare events and reconstructing the associated free energy surface. It works by biasing the evolution of the system by a history‐dependent potential that is adaptively constructed in the space of a suitably chosen set of collective variables. Since its first appearance, the method has been successfully applied in several domains of science. Its widespread adoption is not only due to its efficiency, flexibility, and availability but also to its continuous evolution and its combination with complementary enhanced sampling algorithms. Here, we focus on the progress made in the development of more general and powerful collective variables and on the very recent and exciting evolutions of the method. © 2012 John Wiley & Sons, Ltd.

This article is categorized under:

Molecular and Statistical Mechanics > Molecular Dynamics and Monte-Carlo Methods