bluuebunny/crossref_metadata_2025 huggingface dataset:
R&D and the Export Decision of New Firms
Authors: Braymen Charles , Briggs Kristie , Boulware Jessica
Published: April 2012

Recent literature on the firm‐level decision to export has focused on identifying factors that influence the export decision by firms regardless of the number of years they have been in operation. This article, alternatively, examines the factors that influence new firms to export within the first four years of operation. The results support two key findings that have commonly emerged from entrepreneurial case studies: (1) There is a positive link between research and development (R&D) and early internationalization, and (2) international ties of managers, as is evidenced by the effect of foreign‐born owners, positively impact the firm's decision to export. The former result is the emphasis of this article. In addition, we find that innovation spillovers from neighboring firms impact the export decision of new firms that engage in R&D.
Experience and Confidence in an Internet‐Based Asset Market Experiment
Authors: Fiedler Marina
Published: April 2012

The experience effect in asset markets is one that was thought to be settled. As subjects gained experience with the interface and each other, they typically exhibit fewer instances of mispricing and at lower magnitudes. But questions regarding trading experience are not easy to address in the lab with the typical subject pool since the kind of experience one can typically generate in the lab is experience with the experimental environment itself—not with external environments. However, in virtual worlds asset markets are highly evolved, providing a subject pool with skilled and experienced traders that can be accessed via the Internet. This study compares experimental asset markets with participants recruited from virtual world trading groups to experimental markets with participants recruited from the virtual world at large. I further examine trader performance and trading behavior within markets. The findings indicate that asset markets with virtual world participants recruited from trading groups are more prone to exhibit bubbles than are markets with virtual world participants recruited at large. Within condition, experienced traders are less likely to follow fundamentals and more likely to engage in strategies that result in loss of earnings. Excess confidence is rejected as an explanation for this pattern, as confidence is found to be related to higher earnings and fundamental value trading strategies.
Remarks on Virtual World and Virtual Reality Experiments
Authors: Harrison Glenn W. , Haruvy Ernan , Rutström E. Elisabet
Published: April 2012

In recent years there has been increased behavioral research in virtual reality and virtual worlds. While these experiments could offer substantial advantages to researchers, they might also pose risks. We begin by identifying key concepts in virtual experimental research. Then we review the critical virtual reality component of virtual worlds. Finally, we offer guidance in conducting virtual world research.
Learning and Estimation of the New Keynesian Phillips Curve Models
Authors: Liu Dandan
Published: April 2012

The extant literature is split on the best measure of marginal cost in the New Keynesian Philips Curve, with the output gap and the labor share being the most commonly advocated proxy measures. Which one is the best measure? In this article, I assume that agents update their understanding and expectation period by period, a learning process. In terms of econometrics, I use a recursive Vector Autoregression approach and conduct a forecasting exercise that considers updating of information sets used for formation of expectation. I find that the traditional output gap measure is a more significant variable explaining the dynamics of the U.S. inflation rate, as compared with a measure of the labor income share. Furthermore, the role of the output gap cannot be replaced using lagged values of inflation. Instead, both the output gap and lags of the actual inflation rate are important determinants of inflation.
Interpreting Wage Gaps of Disabled Men: The Roles of Productivity and of Discrimination
Authors: Longhi Simonetta , Nicoletti Cheti , Platt Lucinda
Published: April 2012

Using the UK Labour Force Survey, we study wage gaps for disabled men after the introduction of the Disability Discrimination Act. We estimate wage gaps at the mean and at different quantiles of the wage distribution and decompose them into a part explained by differences in workers' and job characteristics, a part that can be ascribed to health‐related reduced productivity, and a residual part. The large original wage gaps reduce substantially when we control for differences in education and occupation, although significant residuals remain. However, when we isolate productivity differences between disabled and nondisabled workers, the residual wage gap becomes insignificant in most cases.
Focal Points and Economic Efficiency: The Role of Relative Label Salience
Authors: Dugar Subhasish , Shahriar Quazi
Published: April 2012

Coordination games represent coordination problems that arise across social science disciplines. Focal points have been found to be an effective way to solve many of these coordination problems. We experimentally analyze the efficiency‐enhancing power of focal points in 2 × 2 Pareto‐ranked coordination games. We find that the power of focal labels, when attached to the Pareto‐efficient strategy, to promote efficiency critically depends upon the alternative strategy's label salience. When the relative salience of our focal labels is considerably weaker, focal labels mostly fail to raise expected efficiency beyond the mixed‐strategy prediction. But when the relative salience of our focal labels is markedly stronger, focal labels raise expected efficiency much beyond the mixed‐strategy prediction. Furthermore, we find that the efficiency‐enhancing power of focal labels decreases as a measure of risk‐dominance increases across games.
Small Firms and the Growth Stage: Can Entrepreneurship Education Programmes Be Supportive?
Authors: Bureau S. , Salvador E. , Fendt J.
Published: April 2012

Whilst entrepreneurship education is booming, it focuses largely on nascent entrepreneurs and company creation. In contrast, a major challenge in small business entrepreneurship is growth. The authors first position growth and its barriers in small firms in the context of current theory and practice in entrepreneurship education: from this analysis, they identify prerequisites and drivers for growth-related entrepreneurship training for small businesses. A pedagogical experiment focused on growth, targeted at a mixed audience of small firm entrepreneurs and graduate students enrolled in an entrepreneurship major in a business school, is then described. The experiment is presented as an integrated process model. The authors suggest that such programmes could be developed in three main directions: (a) changing the culture of business schools so that they become less individual-centred and more open and value-creating for their students and the external community; (b) strongly and regularly involving entrepreneurship students in the realities of business beyond start-up; and (c) making systematic and sophisticated use of the Internet for enhancing growth through e-learning and community-building.
Mentorship and Sustainable Research Output
Authors: Nundulall Reetha , Dorasamy Nirmala
Published: April 2012

Higher education institutions (HEIs) in South Africa are facing challenges arising as a result of the shift from traditional teaching activities to a combination of research and teaching. Increasing emphasis on research, an integral part of this transformation of higher education, has required HEIs to develop and implement capacity development strategies to enable those new to research to engage in research output; and mentorship is a strategy that is enjoying increasing popularity. This article explores the challenges faced in the implementation of a formal research mentorship programme (REMP), using the University of Johannesburg as a case study. A quantitative approach was adopted to obtain the perceptions of academic staff of REMP as a strategy for building research capacity. The findings reveal that whilst the REMP is strongly favoured by academics as a means of guiding novice researchers, key factors need to be addressed to ensure its success. This article examines the challenges for both mentors and mentees and suggests actions to help mentorship programmes make sustainable contributions to the development of research capacity.
Investing in Higher Education Abroad
Authors: Monk Des
Published: April 2012

This paper presents the results of an examination of the value of business postgraduate courses undertaken by Chinese students at UK universities: such courses cost many thousands of pounds in tuition fees alone. It seemed worthwhile to attempt to assess the benefits that might accrue to such students, especially in terms of their subsequent experience in the labour market. The results suggest that it is the non-financial rather than the financial rewards of postgraduate study that are considered important by Chinese students. Moreover, there is a mismatch between the expectations of these students and their subsequent experience in the Chinese labour market. This issue has become particularly important following the announcement by the present UK coalition government of its intention to reduce central funding subsidies to university teaching by 40% and to reduce the number of students who would be permitted to enter the country. As a result, UK universities are now in an increasingly competitive market for international students; for strategic purposes, it is important to understand the perceptions that such students have formed of the benefits that have accrued as a result of their time spent studying in the UK.
Team Exploratory Testing Sessions
Authors: Saukkoriipi Soili , Tervonen Ilkka
Published: April 2012

Exploratory testing (ET) is popular, especially among agile development teams. In this paper, we study the team aspect in the ET context and explore how to use ET in team sessions to complement other testing activities. The goal was to define a team exploratory testing (TET) session approach and to provide evidence that the approach is worth using. A TET session approach is defined by means of parameters, roles, and process. Also, instructions for using the approach are given. The team is the key factor that gives the approach its value and distinguishes it from basic ET. The team enables greater access to expertise, experience, and information. The TET session approach enables participants with different professional background to join in the session. The sessions may be focused on different purposes; they can contribute to finding defects or learning the system, for example. With careful parameter definition, the approach’s risks are mitigated.
Formation of Van Der Waals Complexes in Concerted Unimolecular Elimination Processes
Authors: Dubnikova Faina , Lifshitz Assa
Published: April 2012

Potential energy surfaces for three unimolecular elimination reactions: , , and were calculated using a variety of quantum chemical methods. It was shown that, in all the three cases, the transition state in the first step of the reaction leads to the production of the complex intermediates based on van der Waals interactions. In addition to the fact that the three complexes appear as intermediates on the potential energy surfaces, which means that they are not free entities, the entropy values of the two elimination products are far above those of the complexes due to their additional Sackur-Tetrode entropy. Moreover, the three vibrational frequencies of the H2O group in the (CH3)3COH complex and the H–Cl and H–F stretch frequencies in CH3CF3 and CH3CH2CH2Cl are quite different (see the various tables). The energy levels of the complexes were found to be below those of the corresponding decomposition products. Rate constants for the elimination processes were calculated from the potential energy surfaces using transition-state theory and were compared to available experimental data.
Degradation of Asphaltenic Fraction by Locally Isolated Halotolerant Bacterial Strains
Authors: Ali Hager R. , El-Gendy Nour Sh. , Moustafa Yasser M. , Roushdy Mohamed I. , Hashem Ahmed I.
Published: April 2012

Three halotolerant bacterial species were isolated from locally oil-polluted water sample for their ability to utilize asphaltene (Asph) fraction as sole carbon and energy source. These bacteria degrade 83–96% of 2500 mg/L asphaltene within 21 d at 30°C and pH7. They were identified as Bacillus sp. Asph1, Pseudomonas aeruginosa Asph2, and Micrococcus sp. Asph3. A statistically significant difference at 95% confidence level for cell growth and percentage biodegradation (%BD) was observed in all biotreatment flasks relative to noninoculated (–ve control) flasks. Regression analysis estimated a quadratic polynomial equation for Asph biodegradation as a function of cell growth. Gel permeation chromatographic (GPC) and Fourier transform infrared (FT-IR) analysis revealed decrease in Asph average molecular weights and significant alternations in functional groups after biotreatment, respectively.
Adverse Outcomes of IVF/ICSI Pregnancies Vary Depending on Aetiology of Infertility
Authors: Kuivasaari-Pirinen Paula , Raatikainen Kaisa , Hippeläinen Maritta , Heinonen Seppo
Published: April 2012

In vitro fertilization (IVF) is a risk factor for pregnancy, but there have been few studies on the effect of infertility’s aetiology. Thus, we have assessed the role of aetiology on IVF pregnancy outcomes in a retrospective cohort study comparing the outcomes of IVF singleton pregnancies with those of spontaneous pregnancies in the general Finnish population. The study group consisted of 255 women with births resulting from singleton IVF pregnancies. Six subgroups were formed according to the following causes of infertility: anovulation (27%), endometriosis (19%), male factor (17%), tubal factor (15%), polycystic ovary syndrome (11%), and unexplained infertility (12%). The reference group consisted of 26,870 naturally conceived women. Adjusted odds ratios (AORs), for confounding factors such as age and parity, were estimated using logistic regression analysis. Women with endometriosis and anovulation had increased risks of preterm birth (AOR 3.25, 95% CI 1.5–7.1 and AOR 2.1, and 95% CI 1.0–4.2, resp.), while women in couples with male factor infertility had a twofold risk of admission to neonatal intensive care (AOR 2.5, 95% CI 1.2–5.3). The findings show that the aetiology of infertility influenced the obstetrics outcome, and that pooling results may obscure some increased risks among subgroups.
Use of Electron Paramagnetic Resonance Spectroscopy to Study Dielectric Properties of Liquids
Authors: Glatzhofer Daniel T. , Kadam Rahul S.
Published: April 2012

The signal response of an EPR active species is attenuated by the medium it is in. Keeping all other parameters the same, the higher the dielectric constant of the medium, the lower the EPR signal response. This behavior is problematic in studying EPR active species in high dielectric media but can be capitalized upon to monitor changes in the dielectric constant or estimate the dielectric constant of the medium. Using a coaxial EPR cell design, the EPR signal of a stable nitroxyl radical compound (2,2,6,6-tetramethyl-piperidin-1-oxyl radical) in a low dielectric constant solvent in an inner tube is attenuated by the solvent present between the inner and outer tubes (jacket medium). The attenuation increases monotonically with an increase in the dielectric constant of the jacket medium. Calibration curves can be constructed using jacket media of known dielectric constants ranging from 2 to 80 and the dielectric constant of a sample used as the jacket medium can be estimated by interpolation. This technique is applied to estimate the dielectric constants and/or composition of mixed solvents and to monitor the rate of a reaction.
Investigation of the properties of conductive hydrogel composite containing Zn particles
Authors: Golikand Ahmad Nozad , Didehban Khadijeh , Rahimi Rahmatollah
Published: April 2012

In this work, the conductive hydrogel composites containing Zn particle synthesized and their electrical and thermal properties were investigated. Polyacrylamide/Zn composites were synthesized by free radical polymerization in aqueous solution. The effect of preparation conditions such as the influence of crosslinker amount, initiator amount, Zn amount, and water absorbency on electrical conductivity of hydrogel was investigated. The effect of preparation conditions on thermal properties has been characterized using thermogravimetric analysis (TGA) method. The structures of metal‐composites were evaluated by FTIR and scanning electron microscopy (SEM) methods. SEM revealed a more uniform pore size when Zn particles were used when compared with pure polyacrylamide. TGA curves showed that both hydrogels were stable upto 600°C. The Zn/polyacrylamide hydrogels have a good conductivity of 4.30 mS cm−1. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Irradiation‐induced grafting of poly(vinylidene fluoride)‐graft‐poly(styrene sulfonic acid) for the preparation of planar and tube‐shaped air‐drying membranes
Authors: Cohen Eyal , Ophir Amos
Published: April 2012

A novel air‐drying membrane was developed and investigated as an alternative for planar and tube‐shaped drying membranes composed of Nafion®. The new membrane is based on poly(vinylidene fluoride) (PVDF) polymer types grafted with polystyrene sulfonic acid. Modification of the PVDF membrane by chemical grafting was initiated via γ‐irradiation of pre‐made film and tube‐shaped samples. The grafting was conducted while the pre‐irradiated PVDF samples were immersed in styrene monomer solution. Three unique characterization methods were introduced to evaluate the ion exchange and barrier functions of the membrane. This investigation focuses on optimizing the degree of grafting yield, and subsequently the control of the membrane's overall functional performances, through (1) monitoring the PVDF's degree of crystallinity and (2) monitoring the styrene monomer solution temperature, respectively. Different levels of crystallinity were achieved by melt blending the PVDF‐copolymer with PVDF‐homopolymer, in various mixing ratios. Another variable examined in this investigation was the introduction of an ionic complex on the sulfonic acid end groups, and its effect on the membrane functional performance was studied. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Study of two chitosan derivatives phosphorylated at hydroxyl or amino groups for application as flocculants
Authors: Zhao Di , Xu JianFeng , Wang Lu , Du JianJia , Dong KeDong , Wang CaiFei , Liu XiangDong
Published: April 2012

Two phosphorylated chitosan derivatives with a similar degree of substitution of about 0.5 were synthesized via either the esterification of chitosan's hydroxyl groups by P2O5 in methanesulfonic acid or the selective incorporation of methylene phosphonic groups on chitosan's amino groups by formaldehyde/H3PO3 in water. The performances of the resulting O‐phosphorylated chitosan (OPC) and N‐methylene phosphonic chitosan (NMPC) as amphoteric flocculants were assessed in comparison with that of unmodified chitosan. In turbidity removal experiments using kaolin suspensions in water, OPC removed about 90% turbidity, but NMPC only removed 60%. The lower flocculation efficiency of NMPC was attributed to the decreased acid strength of the N‐methylene phosphate groups in NMPC. These results revealed that the acidity of the phosphate groups introduced in the modified chitosans is an important factor with regard to the flocculation efficiency, and consequently that O‐phosphorylation is more suitable than N‐phosphorylation for preparing chitosan‐based amphoteric flocculants. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Bacterial cellulose–poly(vinyl alcohol) nanocomposite hydrogels prepared by chemical crosslinking
Authors: Yang Liang , Zhang Hong‐Yu , Yang Qun , Lu Da‐nian
Published: April 2012

The bacterial cellulose–poly(vinyl alcohol) (BC/PVA) nanocomposite hydrogels using BC as the reinforcement and PVA as the matrix materials were formed in coagulating bath and crosslinked with formaldehyde, and characterized by attenuated total reflection Fourier transform infrared spectroscopy, mechanical properties tests, thermogravimetric analysis, and scanning electron microscope analysis. It was known that the chemical cross‐linked BC/PVA nanocomposite hydrogels exhibited some promising characteristics, such as appropriate mechanical strength and excellent thermal properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Environment friendly UV‐curable resins from palm stearin alkyds
Authors: Ang Desmond Teck Chye , Gan Seng Neon
Published: April 2012

Non‐self‐drying palm stearin alkyds were converted into UV‐curable resins via fumarization and maleinization. The maleated alkyds (AlkM) and fumarized alkyds (AlkF) were characterized by 1H‐NMR and FTIR before they were formulated into UV‐curable coatings, with methyl methacrylate as the active diluents, and benzophenone as UV photoinitiator. The film properties, which include the film hardness, adhesion, water and alkali resistance, and thermal stability, of the two series of alkyd coatings were compared. In both series, alkyds with high amount of CHCH could be cured with UV within short time to produce coatings with good film properties. Although both approaches, fumarization and maleinization, serve the same purpose to increase the level of unsaturation in the alkyd, it was found that coatings produced from the two series of alkyds have different UV curability and film properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Generation and characterization of a Notch1 signaling‐specific reporter mouse line
Authors: Smith Emma , Claudinot Stéphanie , Lehal Rajwinder , Pellegrinet Luca , Barrandon Yann , Radtke Freddy
Published: April 2012

Signaling through the Notch1 receptor is essential for the control of numerous developmental processes during embryonic life as well as in adult tissue homeostasis and disease. Since the outcome of Notch1 signaling is highly context‐dependent, and its precise physiological and pathological role in many organs is unclear, it is of great interest to localize and identify the cells that receive active Notch1 signals in vivo. Here, we report the generation and characterization of a BAC‐transgenic mouse line, N1‐Gal4VP16, that when crossed to a Gal4‐responsive reporter mouse line allowed the identification of cells undergoing active Notch1 signaling in vivo. Analysis of embryonic and adult N1‐Gal4VP16 mice demonstrated that the activation pattern of the transgene coincides with previously observed activation patterns of the endogenous Notch1 receptor. Thus, this novel reporter mouse line provides a unique tool to specifically investigate the spatial and temporal aspects of Notch1 signaling in vivo. genesis 50:700–710, 2012. © 2012 Wiley Periodicals, Inc.
Predicting the early invasiveness of nasopharyngeal mucosal neoplasia after radiotherapy by narrow‐band imaging: A pilot study
Authors: Lin Yen‐Chun , Wang Wen‐Hung , Tsai Wan‐Chi , Chen Chih‐Cheng , Chen Wen‐Cheng , Lee Kam‐Fai
Published: April 2012

Background

This study evaluated the correlation between the histologic findings of nasopharyngeal mucosal neoplasias after radiotherapy and narrow‐band imaging (NBI) endoscopic findings.

Methods

One hundred six patients were enrolled. All patients underwent conventional white‐light endoscopic examinations of the nasopharynx, which were followed by NBI endoscopy. Biopsy specimens were obtained if scattered brown‐spotted lesions were identified.

Results

We identified 22 patients with brown‐spotted lesions by NBI endoscopy. Histopathologic study confirmed that 4 lesions were neoplastic, including 2 dysplastic lesions and 2 carcinomatous lesions. According to pathologic examinations, the thickness of the epithelium in carcinomatous, dysplastic, and nonneoplastic lesions were (mean ± SD) 0.85 ± 0.21 mm, 0.45 ± 0.21 mm, and 0.35 ± 0.07 mm, respectively. The epithelial thickness of carcinomatous and dysplastic lesions was significantly thicker than that of nonneoplastic lesions (p < .001 and p = .026, respectively). According to the NBI endoscopic examinations, the epithelial thickness of the brown‐spotted lesions with irregular borders was significantly thicker than those lesions with tailed/round borders (0.48 ± 0.24 mm vs 0.26 ± 0.07 mm, p = .009). Visualization by NBI corresponded to the histopathologic findings; the prevalence of neoplastic lesions with tailed/round borders and irregular borders was 0% (0/13) and 44.4% (4/9), respectively (p = .017).

Conclusions

This study demonstrates that lesions with an irregular pattern tend to be neoplastic lesions. Irregularities observed under NBI are important pathologic indicators of the early invasiveness of nasopharyngeal mucosal neoplasia after radiotherapy. This result warrants further inquiry to confirm its accuracy. © 2012 Wiley Periodicals, Inc. Head Neck, 2013
BRAFV600E mutation in fine‐needle aspiration aspirates: Association with poorer prognostic factors in larger papillary thyroid carcinomas
Authors: Lee Ji In , Jang Hye Won , Kim Sun Wook , Kim Jong–Won , Oh Young Lyun , Chung Jae Hoon
Published: April 2012

Background

Recent studies have shown that BRAFV600E mutation is associated with poor prognostic factors in papillary thyroid carcinoma (PTC). However, there are no studies about the association of the BRAFV600E mutation with poor prognostic factors according to tumor size in PTC.

Methods

We investigated the prevalence of the BRAFV600E mutation and its association with prognostic factors according to tumor size of PTC. BRAFV600E mutation status was assessed in thyroid fine‐needle aspiration (FNA) specimens from 605 patients before thyroidectomy for PTC, and its association with postoperative clinicopathologic factors was evaluated.

Results

The overall prevalence of the BRAFV600E mutation was 67%, and larger tumors more often had the BRAFV600E mutation (p for trend < .05). The BRAFV600E mutation was significantly associated with male sex, tumor size, extrathyroidal invasion, nodal metastasis, and advanced tumor stage (p < .05). There was a significant size‐dependent relationship between the presence of the BRAFV600E mutation and extrathyroidal invasion, nodal metastasis, and advanced tumor stage (p for trend < .05).

Conclusion

The prevalence of the BRAFV600E mutation increased with increased tumor size. Preoperative FNA‐detected BRAFV600E mutation was associated with poor prognostic factors, and the association was stronger in larger tumors. © 2012 Wiley Periodicals, Inc. Head Neck, 2013
Rate constants calculation of hydrogen abstraction reactions CH3CHBr + HBr and CH3CBr2 + HBr
Authors: Wang Li , Zhao Jianxiang , He Hongqing , Zhang Jinglai
Published: April 2012

Dual‐level direct dynamics method is used to study the kinetic properties of the hydrogen abstraction reactions of CH3CHBr + HBr → CH3CH2Br + Br (R1) and CH3CBr2 + HBr → CH3CHBr2 + Br (R2). Optimized geometries and frequencies of all the stationary points and extra points along the minimum‐energy path are obtained at the MPW1K/6‐311+G(d,p), MPW1K/ma‐TZVP, and BMK/6‐311+G(d,p) levels. Two complexes with energies less than that of the reactants are located in the entrance of each reaction at the MPW1K/6‐311+G(d,p) and MPW1K/ma‐TZVP levels, respectively. The energy profiles are further refined with the interpolated single‐point energies method at the G2M(RCC5)//MPW1K/6‐311+G(d,p) level of theory. By the improved canonical variational transition‐state theory with the small‐curvature tunneling correction (SCT), the rate constants are evaluated over a wide temperature range of 200–2000 K. Our calculations have shown that the radical reactivity decreases from CH3CHBr to CH3CBr2. Finally, the total rate constants are fitted by two modified Arrhenius expression. © 2012 Wiley Periodicals, Inc.
Magnetic, kinetic, and optical properties of new high‐pressure phases in the system Cr–GaSb: Ab initio density functional theory study
Authors: Kulatov Erkin , Magnitskaya Maria , Uspenskii Yurii , Popova Svetlana , Brazhkin Vadim , Maksimov Evgenii
Published: April 2012

The structural, transport, magnetic, and optical properties of high‐pressure‐synthesized metastable compounds CrGaSb and CrGa2Sb2 are calculated from first principles. In addition to theoretical results, new X‐ray structural measurements of CrGa2Sb2 up to 9 GPa are reported. Both high‐pressure phases CrGaSb and CrGa2Sb2 are found to be at the edge between metal and semiconductor, which implies that the standard density functional theory predictions may be misleading. To clarify the situation, a study is conducted whether the results depend significantly on the approximation used for the exchange–correlation potential. A possible effect of slight nonstoichiometry found in the CrGa2Sb2 samples is also investigated. The calculation results agree with most available experimental data and are internally consistent, which provides the assurance that, as a whole, they give a reliable picture of electronic properties in CrGaSb and CrGa2Sb2. © 2012 Wiley Periodicals, Inc.
Theoretical study on the reaction mechanism of formation of 3,5‐diacetyl‐1,4‐dihydrolutidine
Authors: Teramae Hiroyuki , Y. Maruo Yasuko
Published: April 2012

We have studied the reaction path of the formation of 3,5‐diacetyl‐1,4‐dihydrolutidine (DL1), 3,5‐dibenzoyl‐1,4‐dihydro‐2,6‐dimethylpyridine, and 2,6‐dibenzoyl‐1,4‐dihydro‐3,5‐dimethylpyridine with the ab initio molecular orbital method at HF/3‐21G and HF/6‐31G(d,p) levels. For DL1, we also calculated at MP2/6‐31G(d,p) level. The barrier heights of H2O elimination elementary reactions are about 50–60 kcal/mol and quite high in the gas phase, however, this is well agreed with the experimental results that the reaction proceeds in aqueous solutions. © 2012 Wiley Periodicals, Inc.
Theoretical studies of electrostatic effect of protein environment on electronic structures and chemical indices of the active site of oxygenated and deoxygenated hemerythrin
Authors: Takano Yu , Yamaguchi Kizashi , Nakamura Haruki
Published: April 2012

We have studied the electrostatic effect of protein environment on electronic structures and chemical indices of the active site of oxygenated and deoxygenated hemerythrin (oxyHr and deoxyHr) using hybrid density functional calculations. We found that the UBHandHLYP method can be regarded as a reliable method for the nature of chemical bonds of Hr even in the protein. The electrostatic effects of the protein environment on oxyHr and deoxyHr greatly improve the magnetic couplings and provide the polarized electronic structures. The electrostatic effects on the active site of oxyHr hardly affect the shape and symmetry of singly occupied natural orbitals but contribute to the enhanced orbital interaction between the active core of Hr and oxygen molecule. This strong orbital interaction leads to easy binding of oxygen molecule to Hr for oxygen transport. Thus, our computation suggests that protein environment regulates the electronic structures of the active site to intensify the intrinsic ability of the active site and to express biological functions such as oxygen transport, energy conversion, and electron transfer. © 2012 Wiley Periodicals, Inc.
Temperature dependence of self‐assembled molecular capsules consisting of gear‐shaped amphiphile molecules with molecular dynamics simulations
Authors: Koseki Jun , Kita Yukiumi , Hiraoka Shuichi , Nagashima Umpei , Tachikawa Masanori
Published: April 2012

Molecular dynamics simulations of hexameric molecular capsules constructed from gear‐shaped amphiphile molecules with the aid of solvophobic effect and van der Waals force were performed with general AMBER force field to elucidate the thermodynamical properties of the capsules. The optimized structure of the capsule 16 consisting of methylated gear‐shaped molecules (1) is a nearly cubic structure, whereas the distorted structure is found for the capsule 26 consisting of ones lacking three methyl groups, (2) so as to maximize the contact surface. Disassembly temperature for the demethylated capsule 26, ∼210 K, is much lower than that for the methylated one 16, ∼340 K, which is consistent with the corresponding experimental result that 16 is stable, whereas 2 exists as a monomer in aqueous methanol. © 2012 Wiley Periodicals, Inc.
Molecular Dynamics simulations of azanaphthoquinone annelated pyrrole derivatives as anticancer agent in DNA duplex
Authors: Punkvang Auradee , Pungpo Pornpan , Kamsri Pharit , Kasamsri Dararat , Srisupan Apinya , Saparpakorn Patchreenart , Hannongbua Supa , Wolschann Peter , Prueksaaroon Supakit , Pongprom Nipawan
Published: April 2012

The azanaphthoquinone annelated pyrrole derivatives were synthesized and characterized with an effort to develop novel DNA intercalating agents as anticancer compounds. To model the binding of these compounds in the intercalation site of the DNA duplex, molecular dynamics (MD) simulations using AMBER program were performed. Moreover, molecular mechanics/Poisson–Boltzmann surface area method was used to calculate the binding free energy of azanaphthoquinone annelated pyrrole derivatives in the intercalation site of the DNA duplex. On the basis of MD simulations, the π–π stacking interaction of azanaphthoquinone annelated pyrrole derivatives with base pairs of C and G is the crucial interaction for binding of these DNA intercalating agents. Moreover, the hydrogen bond interaction of side chain could enhance the binding affinity of azanaphthoquinone annelated pyrrole derivatives in the intercalation site. Therefore, the obtained results should be helpful for better understanding the binding of azanaphthoquinone annelated pyrrole derivatives in the intercalation site. © 2012 Wiley Periodicals, Inc.
Bonding Quality of Chemically‐Modified Soybean Protein Concentrate‐Based Adhesives in Particleboards from Rice Husks
Authors: Ciannamea E. M. , Martucci J. F. , Stefani P. M. , Ruseckaite R. A.
Published: April 2012

The aim of the present study was to upgrade the bonding quality and water resistance of medium‐density particleboards based on rice husks (RH) as a wood substitute and soybean protein concentrate (SPC) as the binder via chemical modification of SPC. Alkali (A), citric acid (CA) and boric acid (BA) were used to modify proteins and the carbohydrate complex in SPC. The effect of chemical treatment performed on SPC was followed by Fourier transform infrared, differential scanning calorimetry, thermo‐gravimetric analysis and initial apparent viscosity measurements. Board properties were evaluated in terms of internal bond (IB) and physical properties. Results revealed that boards bonded with SPC treated with boric acid, exhibited the highest IB and the lowest water absorption and thickness swelling at 2 and 24 h, due to cross‐linking reactions with exposed OH‐groups in the amorphous region of cellulose of RH. Results demonstrate that boric acid‐modified–SPC‐bonded boards met the requirements of IB recommended by the US Standard ANSI A208.1‐2009 for M1, MS, M2 and M3‐grade medium‐density particleboards but failed to pass the thickness swelling required. This issue of BSPC‐RH boards is compensated for by the benefit of being formaldehyde‐free which makes them suitable for indoor applications.
Calcium carbonate polymorph control using droplet-based microfluidics
Authors: Yashina Alexandra , Meldrum Fiona , deMello Andrew
Published: April 2012

Calcium carbonate (CaCO3) is one of the most abundant minerals and of high importance in many areas of science including global CO2 exchange, industrial water treatment energy storage, and the formation of shells and skeletons. Industrially, calcium carbonate is also used in the production of cement, glasses, paints, plastics, rubbers, ceramics, and steel, as well as being a key material in oil refining and iron ore purification. CaCO3 displays a complex polymorphic behaviour which, despite numerous experiments, remains poorly characterised. In this paper, we report the use of a segmented-flow microfluidic reactor for the controlled precipitation of calcium carbonate and compare the resulting crystal properties with those obtained using both continuous flow microfluidic reactors and conventional bulk methods. Through combination of equal volumes of equimolar aqueous solutions of calcium chloride and sodium carbonate on the picoliter scale, it was possible to achieve excellent definition of both crystal size and size distribution. Furthermore, highly reproducible control over crystal polymorph could be realised, such that pure calcite, pure vaterite, or a mixture of calcite and vaterite could be precipitated depending on the reaction conditions and droplet-volumes employed. In contrast, the crystals precipitated in the continuous flow and bulk systems comprised of a mixture of calcite and vaterite and exhibited a broad distribution of sizes for all reaction conditions investigated.
CO2 dissolution in water using long serpentine microchannels
Authors: Cubaud Thomas , Sauzade Martin , Sun Ruopeng
Published: April 2012

The evolution of carbon dioxide bubbles dissolving in water is experimentally examined using long microchannels. We study the coupling between bubble hydrodynamics and dissolution in confined geometries. The gas impregnation process in liquid produces significant flow rearrangements. Depending on the initial volumetric liquid fraction, three operating regimes are identified, namely saturating, coalescing, and dissolving. The morphological and dynamical transition from segmented to dilute bubbly flows is investigated. Tracking individual bubbles along the flow direction is used to calculate the temporal evolution of the liquid volumetric fraction and the average flow velocity near reference bubbles over long distances. This method allows us to empirically establish the functional relationship between bubble size and velocity. Finally, we examine the implication of this relationship during the coalescing flow regime, which limits the efficiency of the dissolution process.
Tunable spatial heterogeneity in structure and composition within aqueous microfluidic droplets
Authors: Hui Sophia Lee Su , Wang Pengzhi , Kun Yap Swee , Alan Hatton T. , Khan Saif A.
Published: April 2012

In this paper, we demonstrate biphasic microfluidic droplets with broadly tunable internal structures, from simple near-equilibrium drop-in-drop morphologies to complex yet uniform non-equilibrium steady-state structures. The droplets contain an aqueous mixture of poly(ethylene glycol) (PEG) and dextran and are dispensed into an immiscible oil in a microfluidic T-junction device. Above a certain well-defined threshold droplet speed, the inner dextran-rich phase is “stirred” within the outer PEG-rich phase. The stirred polymer mixture is observed to exhibit a near continuum of speed and composition-dependent phase morphologies. There is increasing interest in the use of such aqueous two-phase systems in microfluidic devices for biomolecular applications in a variety of contexts. Our work presents a method to go beyond equilibrium phase morphologies in generating microfluidic “multiple” emulsions and at the same time raises the possibility of biochemical experimentation in benign yet complex biomimetic milieus.
Utilizing microfluidics to synthesize polyethylene glycol microbeads for Förster resonance energy transfer based glucose sensing
Authors: Kantak Chaitanya , Zhu Qingdi , Beyer Sebastian , Bansal Tushar , Trau Dieter
Published: April 2012

Here, we utilize microfluidic droplet technology to generate photopolymerizeable polyethylene glycol (PEG) hydrogel microbeads incorporating a fluorescence-based glucose bioassay. A microfluidic T-junction and multiphase flow of fluorescein isothiocyanate dextran, tetramethyl rhodamine isothiocyanate concanavalin A, and PEG in water were used to generate microdroplets in a continuous stream of hexadecane. The microdroplets were photopolymerized mid-stream with ultraviolet light exposure to form PEG microbeads and were collected at the outlet for further analysis. Devices were prototyped in PDMS and generated highly monodisperse 72 ± 2 μm sized microbeads (measured after transfer into aqueous phase) at a continuous flow rate between 0.04 ml/h—0.06 ml/h. Scanning electron microscopy analysis was conducted to analyze and confirm microbead integrity and surface morphology. Glucose sensing was carried out using a Förster resonance energy transfer (FRET) based assay. A proportional fluorescence intensity increase was measured within a 1–10 mM glucose concentration range. Microfluidically synthesized microbeads encapsulating sensing biomolecules offer a quick and low cost method to generate monodisperse biosensors for a variety of applications including cell cultures systems, tissue engineering, etc.
Mechanism of densification in silica glass under pressure as revealed by a bottom-up pairwise effective interaction model
Authors: Izvekov Sergei , Rice Betsy M.
Published: April 2012

A new short-range pairwise numerical potential for silica is presented. The potential is derived from a single ab initio molecular dynamics (AIMD) simulation of molten silica using the force-matching method with the forces being represented numerically by piecewise functions (splines). The AIMD simulation is performed using the Born-Oppenheimer method with the generalized gradient approximation (BLYP) for the XC energy functional. The new effective potential includes a soft-repulsive shoulder to describe the interactions of oxygen ions at short separations. The new potential, despite being short-ranged and derived from single-phase data, exhibits a good transferability to silica crystalline polymorphs and amorphous silica. The importance of the O–O soft-repulsive shoulder interaction on glass densification under cold and shock compressions is assessed from MD simulations of silica glass under room and shock Hugoniot conditions, respectively. Results from these simulations indicate that the appearance of oxygen complexes (primarily pairs) interacting through soft-repulsive shoulder potential occurs at 8–10 GPa, and under cold compression conditions becomes notable at 40 GPa, essentially coinciding with the transition to a Si sixfold coordination state. An analysis of changes in system structure in compressed and shocked states reveals that the O ions interacting through the soft-repulsive shoulder potential in denser states of silica glass may create a mechanical multi-stability under elevated pressures and thus to contribute to the observed anomalous densification.
Origin of ferromagnetism and oxygen-vacancy ordering induced cross-controlled magnetoelectric effects at room temperature
Authors: Wei X. K. , Zou T. , Wang F. , Zhang Q. H. , Sun Y. , Gu L. , Hirata A. , Chen M. W. , Yao Y. , Jin C. Q. , Yu R. C.
Published: April 2012

In dilute magnetic oxide hexagonal Ba(Ti0.9Fe0.1)O2.81 bulk ceramic, we report on combined ferromagnetism and improper ferroelectricity as well as cross-controlled magnetoelectric effects at room temperature. The annular-bright-field (ABF) imaging technique in scanning transmission electron microscopy (STEM) demonstrates an oxygen vacancy ordering in the hexagonal closest-packed Ba1-O1 layers and severe distortion of the octahedra and pyramids. Strong dependencies of the susceptibility on temperature and magnetic field as well as the frequency dependence of magnetization under an ac electric field reveal that the intrinsic ferromagnetism of the highly insulating system dynamically evolves from a paramagnetic ground state, and dynamic exchanges of trapped electrons in the ordered polarons are attributed to the ferromagnetic interaction. Accordingly, aided by the motion of oxygen vacancies, responses of the trapped electrons to the ac magnetic field result in the reversal of magnetically induced voltages between high and low states. Our results not only expand our understanding on the magnetoelectric coupling mechanism, but also provide a grand opportunity toward designing novel multiferroic materials through introducing ordered point defects into a centrosymmetric matrix.
The cored and logarithm galactic potentials: Periodic orbits and integrability
Authors: Jiménez-Lara Lidia , Llibre Jaume
Published: April 2012

We apply the averaging theory of first order to study analytically families of periodic orbits for the cored and logarithmic Hamiltonians \documentclass[12pt]{minimal}\begin{document}$H_C= \dfrac{1}{2}\left(p_x^2 + p_y^2\right)\break + \sqrt{1 + x^2 + \dfrac{y^2}{q^2}} -1,$\end{document}HC=12px2+py2+1+x2+y2q2−1, and \documentclass[12pt]{minimal}\begin{document}$H_L= \dfrac{1}{2} \left(p_x^2 + p_y^2\right) +\dfrac{1}{2}\log \left(1+x^2+\dfrac{y^2}{q^2}\right),$\end{document}HL=12px2+py2+12log1+x2+y2q2, which are relevant in the study of the galactic dynamic. We first show, after introducing a scale transformation in the coordinates and momenta with a parameter ɛ, that both systems give essentially the same set of equations of motion up to first order in ɛ. Then the conditions for finding families of periodic orbits, using the averaging theory up to first order in ɛ, apply equally for both systems in every energy level H = h > 0 with H either HC or HL. We prove the existence of two periodic orbits if q is irrational, for ɛ small enough, and we give an analytic approximation for the initial conditions of these periodic orbits. Finally, the previous periodic orbits provide information about the non-integrability of the cored and the logarithmic Hamiltonian systems.
Three-dimensional transport imaging for the spatially resolved determination of carrier diffusion length in bulk materials
Authors: Blaine K. E. , Phillips D. J. , Frenzen C. L. , Scandrett C. , Haegel N. M.
Published: April 2012

A contact-free optical technique is developed to enable a spatially resolved measurement of minority carrier diffusion length and the associated mobility-lifetime (μτ) product in bulk semiconductor materials. A scanning electron microscope is used in combination with an internal optical microscope and imaging charge-coupled device (CCD) to image the bulk luminescence from minority carrier recombination associated with one-dimensional excess carrier generation. Using a Green's function to model steady-state minority carrier diffusion in a three-dimensional half space, non-linear least squares analysis is then applied to extract values of carrier diffusion length and surface recombination velocity. The approach enables measurement of spatial variations in the μτ product with a high degree of spatial resolution.