bluuebunny/crossref_metadata_2025 huggingface dataset:
A Research Study on Identifying the Correlation between Fourth Graders’ Attitudes and Behaviors toward the Environment
Authors: Hasiloglu Mehmet Akif , Kunduraci Ayse
Published: May 2018

This study aims to examine the degree to which scores received by fourth graders in Turkey on the environmental attitudes scale is reflected in their environmental awareness (with respect to practice, behaviors), and to identify the correlation between attitudes and behaviors. Case study design was used to collect data in the study. Observation and questionnaire techniques were used as the data collection instruments. The sample of the study consisted of 15 students selected among the fourth graders attending elementary schools in Agri province of Turkey in the 2015-2016 academic year. The Attitudes Toward the Environment Scale (ATES), developed by Yasaroglu (2012), was used to measure students’ attitudes toward the environment. The reliability of the scale was examined by Yasaroglu (2012) using Cronbach’s alpha internal consistency coefficient, which is reported to be 0.84. Observations were made to measure students’ environmental awareness by using the video recording technique. On the other hand, Spearman’s Correlation analysis was used for data analysis. The relationship between students’ scores on the attitude scale and their scores for environmental awareness, assigned on the basis of the observations made, was found weak, as indicated by the correlation between the two (Spearman’s rho (r)=0.075). An important finding was that even though students received satisfactory scores on the ATES scale, a sizable number of them failed to reflect these attitudes in their practices or behaviors, which would indicate environmental awareness.
A Study of Primary School Teachers’ and Turkish Language Teachers’ Anxiety about Tablet PC Assisted Teaching
Authors: Ozturk Ergun
Published: May 2018

Many educational institutions use a number of technologies in classrooms to promote the effectiveness of learning activities. In recent years, tablet PCs have become the primary of these technologies. Tablet PCs in particular play an important role in increasing the effectiveness and efficiency of the process of learning and teaching. In order to reveal this effect of tablet PCs on learning-teaching and to ensure that tablet PCs are used effectively by teachers, development of favorable attitudes by teachers towards computers and elimination of anxiety about using these devices are of utmost importance. The purpose of this study is to determine primary school and Turkish teachers’ anxiety level about using tablet PCs in the process of learning and teaching. To this end, the anxiety scale for tablet PC assisted teaching developed by the researcher was administrated to the teachers. In order to determine the teachers’ anxiety level about using tablet PC in teaching, cross-sectional survey technique was used in the research. According to the results of the research, Turkish teachers’ anxiety level about teaching with tablet PC was found to be higher than that of primary school teachers. Also, in both branches of teaching, females have higher anxiety level about teaching with tablet PC than males. The findings of the research suggest that teachers should be provided with adequate training in using tablet PCs and integration of tablet PCs into educational activities, and that the technical infrastructure should be arranged accordingly.
Measuring Environmental Sensitivity in Educational Contexts: A Validation Study With German-Speaking Students
Authors: Tillmann Teresa , El Matany Katharina , Duttweiler Heather
Published: May 2018

Sensory-Processing Sensitivity (SPS), as part of the general theory on Environmental Sensitivity (Pluess, 2015), is a temperamental individual difference variable, referring to sensitive perception and processing of as well as reflection upon environmental stimuli. For its measurement, Aron and Aron (1997) developed the Highly Sensitive Person Scale (HSP Scale) for application with adults. However, despite some adaption into German (Konrad & Herzberg, 2017) and a first English version for children (Pluess et al., 2018), no suitable measures of SPS for children exist in German. The presented two studies aimed at developing and validating a short, 10-item German version of the scale, which can be administered efficiently in educational field studies with German-speaking secondary school students. The factorial structure, its relationship with other personality traits (i.e., the Big Five; McCrae & Costa, 1990) and exploratory analyses on relationships with additional school-related variables were revealed using data from two independent student samples (N = 301 German academic-track secondary school students and N = 460 German vocational track secondary school students). Relations to existing research, practical implications for the educational context, and limitations of the studies are discussed.
Effect of temperature on thermodynamic properties of protic ionic liquids: 2-hydroxy ethylammonium lactate (2-HEAL) + short hydroxylic solvent
Authors: Barros Safira , S. Andrade Rebecca , Iglesias Miguel
Published: May 2018

In this study, we have synthesized the
protic ionic liquid 2-hydroxy ethylammonium lactate
(2-HEAL), and investigated its volumetric and acoustic behaviour into
different hydroxylic media (water, methanol and ethanol) at the temperature
288.15-323.15 K and atmospheric pressure. Total solubility of the ionic liquid
into these solvents was observed at this range of temperature. Apparent molar volume and apparent molar isentropic
compressibility values have been computed from the experimental data and fitted
to a temperature dependent Redlich-Mayer equation. From these
correlations, the limiting infinite dilution values of the apparent magnitudes
have also been computed. Derived magnitudes such as isobaric expansibility and
isothermal coefficient of pressure excess molar enthalpy were computed due to
their importance in the study of specific molecular interactions among the ions
and covalent molecules enclosed into mixtures. The measured experimental data
were used to test the accuracy of prediction of different models
(Mchaweh-Nasrifar–Moshfeghian model (MNM model) and the modified Heller
temperature dependent equation (MHE) for density and Collision Factor Theory
(CFT) for ultrasonic velocity). The obtained results
indicate that ionic liquid interactions in water are weaker than in the
studied alcoholic solutions, as previously observed in analogous protic ionic
liquids.
Block relevance (BR) analysis and polarity descriptors in property-based drug design
Authors: Ermondi Giuseppe , Caron Giulia
Published: May 2018

Block Relevance (BR) analysis is a tool to interpret QSPR/PLS models which can provide the information content of any physicochemical determinant used in property-based drug discovery; its application for the characterization of experimental polarity descriptors is discussed.
Influence of oxygen on the Warburg effect: do cancer cells produce lactate only from glucose?
Authors: Graboń Wojciech , Otto-Ślusarczyk Dagmara , Barańczyk-Kuźma Anna
Published: May 2018

The common characteristics of many tumors is phenomenon termed the Warburg effect – the production of abundant amounts of lactate in the presence of sufficient oxygen. It is commonly accepted that lactate is synthesized from glucose; hence, the other term for this phenomenon is aerobic glycolysis. Hypoxia, frequently observed in solid tumors, results in an increased HIF 1 transcription factor activity, which stimulates lactate synthesis by activating the transcription of glucose transporters and glycolytic enzymes genes, while inhibiting mitochondrial pyruvate metabolism. However, under normoxic conditions, when the HIF-1 factor is inactive, the lactate is the product not only of glycolysis, but also of glutaminolysis. Both pathways are activated by the c-myc transcription factor. Glutaminolysis, the mitochondrial pathway involving Krebs cycle enzymes, provides energy to the cell and the pathway intermediates (L-glutamate, L-aspartate, acetyl CoA) are substrates for the synthesis of nucleic acids, proteins and lipids. Subsequently, the cytoplasmic oxaloacetate-malate-pyruvate-lactate axis provides redox cofactors - NADPH for lipid and DNA synthesis and for cellular antioxidant systems as well as NAD+ necessary for efficient glycolysis resulting in increased lactate synthesis from glucose at normoxia. Thus, oxygen as Krebs cycle activator enhances lactate synthesis as the end product of glutaminolysis as well as promotes glycolytic lactate synthesis. In conclusion, the Warburg effect is the result of oxygen-induced extensive lactate production in both glycolysis and glutaminolysis pathways. Thus, an increased lactate synthesis at normoxia is just not the result of the cellular shift to extramitochondrial metabolism, but a manifestation of transcriptionally regulated adaptive response, allowing the cancer cells to acquire the energy and nutrients necessary for growth and proliferation.
Estimation of the chemical specific
surface area of catalytic nanoparticles
by TEM images analysis
Authors: Pawlyta M. , Sobel B. , Liszka B.
Published: May 2018

Purpose: The purpose of this article is the development of quantitative methods for
assessing the quality of nanocomposite materials used in fuel cells.
Design/methodology/approach: latinum is the most commonly used catalyst in fuel
cells, commonly in the form of nanoparticles deposited on the surface of carbon black.
Due to the nanometric size of platinum particles, transmission electron microscopy can
be applied to evaluate the produced catalysts. TEM image also allow to determinate the
approximate value of the chemical specific surface area) of platinum nanoparticles, but only
in case of spherical particles.
Findings: In present work, taking into account additional assumptions resulting directly from
the analysis of microscopic images, the method of estimation of the particle diameter and
the chemical specific surface area for nonsymmetrical (elongated) nanoparticles is present.
Research limitations/implications: The presented work presents a method for
determining the specific surface of platinum, when their shape is elongated. It is worth
noting that the modified formulas for determining the particle diameter and the value of
the chemically active specific surface of the platinum nanoparticles of the elongated shape
are equivalent to the formulas previously given for spherical particles, if the particle length
and its diameter are equal. In this case, patterns for symmetric particles and more general
(modified) patterns can be used interchangeably.
Practical implications: Development of new and more effective catalysts for fuel cells.
Originality/value: The significance of the presented work results from the possibility
of using the described method in the catalyst studies during real catalytic processes.
It allows comparing catalytic activity after the process, also in unusual conditions and in an
aggressive environment, using minimal amounts of material.
Pemanfaatan ovitrap dalam pengukuran populasi Aedes sp. dan penentuan kondisi rumah
Authors: Hidayati Lisa , Hadi Upik Kesumawati , Soviana Susi
Published: May 2018

Kejadian demam berdarah dengue (DBD) masih menjadi masalah kesehatan masyarakat di Indonesia. Pengamatan selama kurun waktu 20 sampai 25 tahun sejak awal ditemukan kasus DBD menyatakan bahwa angka kejadian luar biasa DBD mengalami peningkatan setiap lima tahun. Tujuan dari penelitian ini adalah 1) mempelajari keanekaragaman nyamuk Aedes di kota Sukabumi, 2) mengukur populasi Aedes sp. berdasarkan jumlah telur dan indeks ovitrap, dan 3) mengetahui hubungan indeks ovitrap dengan kondisi rumah. Telur Aedes sp. dikumpulkan dari 14 kelurahan di Kota Sukabumi yang memiliki angka insiden tertinggi, mulai dari bulan Mei 2015 hingga Agustus 2015. Pengumpulan telur dilakukan dengan cara memasang perangkap telur (ovitrap) sebanyak 230 buah di 115 rumah (di dalam dan di luar rumah). Hasil pengumpulan ovitrap menunjukan jumlah telur yang diperoleh dari ovitrap di dalam rumah 3 kali lebih banyak dibandingkan dengan telur dari ovitrap di luar rumah  (1307 banding 429). Nyamuk Ae. aegypti ditemukan pada ovitrap di dalam rumah dan Ae. albopictus pada ovitrap di luar rumah. Indeks ovitrap di dalam rumah mencapai 60%, atau 1,6 kali lebih banyak dibandingkan dengan indeks ovitrap di luar rumah (37%). Rumah dengan ventilasi dan sanitasi buruk berisiko 3,09 kali meningkatkan angka indeks ovitrap. Hasil penelitian ini dapat digunakan sebagai informasi dasar bagi masyarakat untuk meningkatkan kebersihan lingkungan melalui pengurangan tempat perindukan nyamuk sehingga menurunkan kejadian DBD.
Siklus hidup dan statistik demografi kutukebul Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) biotipe B dan non-B pada tanaman cabai (Capsicum annuum L.)
Authors: Hidayat Purnama , Kurniawan Hazen Arrazie , Afifah Lutfi , Triwidodo Hermanu
Published: May 2018

Kutukebul Bemisia tabaci (Gennadius) biotipe B yang juga dikenal sebagai Bemisia argentifolii  (Gennadius) merupakan jenis biotipe yang lebih ganas dalam merusak tanaman dibandingkan dengan biotipe non-B. Saat ini kutukebul B. tabaci biotipe B telah dilaporkan keberadaanya di Indonesia. Informasi dasar, seperti siklus hidup, lama hidup, keperidian, dan kemampuan berkembang biak kutukebul sangat diperlukan sebagai dasar dalam menyusun strategi pengendalian hama kutukebul tersebut. Penelitian bertujuan untuk mempelajari siklus hidup dan statistik demografi kutukebul B. tabaci biotipe B dan non-B pada tanaman cabai. Penelitian dilakukan dengan mengamati perkembangan sejak telur sampai menjadi dewasa di growth chamber yang terkontrol suhu dan pencahayaannya. Pengamatan dilakukan terhadap beberapa aspek biologi dan beberapa parameter statistik demografi. Hasil penelitian menunjukkan bahwa kutukebul B. tabaci biotipe B memiliki beberapa aspek biologi yang berbeda dengan non-B pada tanaman cabai. Siklus hidup kutukebul B. tabaci biotipe B dan non-B masing-masing adalah 33,27 dan 30,86 hari. Kutukebul B. tabaci biotipe B memiliki laju reproduksi bersih (R0) yang hampir sama dengan biotipe non-B, begitu juga rataan masa generasinya. Namun demikian, laju pertambahan intrinsik (r) kutukebul B. tabaci biotipe B 2,5 kali lebih cepat dibandingkan biotipe non-B. Kutukebul B. tabaci biotipe B berlipat ganda populasinya (DT) 2 kali lebih cepat dibandingkan biotipe non-B. Kutukebul B. tabaci biotipe B berpotensi lebih berbahaya dibandingkan dengan biotipe non-B sehingga perlu diwaspadai keberadaannya.
Lecture conventionnaliste du cas des établissements Thunevin
Authors: Verstraete Thierry , Néraudau Gérard , Jouison-Laffitte Estèle
Published: May 2018

Les établissements Thunevin évoluent dans la production et le négoce de vin. Robert Parker, célèbre critique américain et créateur de la non moins célèbre revue The Wine Advocate, a qualifié leur fondateur et dirigeant, Jean-Luc Thunevin, de « bad boy ». Ce terme peut traduire une forme de déviance par rapport aux règles de conduite instituées dans un univers d’action particulier ou, autrement dit, par rapport aux registres conventionnels des espaces sociaux investis. Pour appréhender cette originalité, nous avons choisi d’adopter une perspective conventionnaliste pour apprendre du succès des établissements Thunevin. En effet, parti de rien, Jean-Luc Thunevin est aujourd’hui emblématique du mouvement des « vins de garage ». Ainsi, l’entreprise a porté son cru fétiche, Château Valandraud, au sommet de l’appellation en devenant premier grand cru classé de Saint-Émilion lors du classement de 2012 (les vins de Saint-Émilion sont soumis au classement de façon décennale). Cette réussite exceptionnelle incitait à une étude de cas intrinsèque, laquelle s’est combinée à une étude de cas instrumentale (Stake, 1994, 1995) par la lumière que le cas des établissements Thunevin prenait sous l’éclairage de la perspective conventionnaliste.
Perception de la RSE par les dirigeants de PME camerounaises
Authors: Sangue Fotso Robert
Published: May 2018

La responsabilité sociale de l’entreprise (RSE) s’impose aujourd’hui comme un levier stratégique de développement des entreprises, quelle que soit leur taille. L’intérêt porté à la PME revêt ainsi un caractère important pour l’étude de ce concept. L’objectif de cette recherche est d’appréhender dans un territoire donné la perception qu’ont les dirigeants de PME de la RSE dans un environnement marqué par le déséquilibre institutionnel. Une enquête exploratoire menée auprès de 22 dirigeants de PME camerounaises a permis de relever que les PME sont porteuses de finalités non exclusivement lucratives, que les convictions managériales – caractérisées par les valeurs éthiques et substantielles – et la culture traditionnelle fondent la perception de la RSE des dirigeants de PME.
Une contribution à l’étude de la structuration du contrôle de gestion en PME : le cas de trois entreprises familiales et industrielles de taille intermédiaire (ETI)
Authors: Barbelivien Dominique , Meyssonnier François
Published: May 2018

L’étude de la mise en place du contrôle de gestion dans trois entreprises françaises, familiales et industrielles, de taille intermédiaire (ETI), montre qu’elle ne dépend pas que de la taille de l’entreprise et que le contrôle de gestion est plus porteur d’une logique de rationalisation que d’une logique de financiarisation. Le processus de structuration du contrôle de gestion est limité dans ses objectifs et incomplet dans l’instrumentation qui en résulte. Le système de pilotage de la performance sur lequel il débouche n’accorde qu’un pouvoir d’influence modéré au nouveau contrôleur de gestion.
The HIV-1 Tat protein recruits a ubiquitin ligase to reorganize the 7SK snRNP for transcriptional activation
Authors: Faust Tyler B , Li Yang , Bacon Curtis W , Jang Gwendolyn M , Weiss Amit , Jayaraman Bhargavi , Newton Billy W , Krogan Nevan J , D'Orso Iván , Frankel Alan D
Published: May 2018

The HIV-1 Tat protein hijacks P-TEFb kinase to activate paused RNA polymerase II (RNAP II) at the viral promoter. Tat binds additional host factors, but it is unclear how they regulate RNAP II elongation. Here, we identify the cytoplasmic ubiquitin ligase UBE2O as critical for Tat transcriptional activity. Tat hijacks UBE2O to ubiquitinate the P-TEFb kinase inhibitor HEXIM1 of the 7SK snRNP, a fraction of which also resides in the cytoplasm bound to P-TEFb. HEXIM1 ubiquitination sequesters it in the cytoplasm and releases P-TEFb from the inhibitory 7SK complex. Free P-TEFb then becomes enriched in chromatin, a process that is also stimulated by treating cells with a CDK9 inhibitor. Finally, we demonstrate that UBE2O is critical for P-TEFb recruitment to the HIV-1 promoter. Together, the data support a unique model of elongation control where non-degradative ubiquitination of nuclear and cytoplasmic 7SK snRNP pools increases P-TEFb levels for transcriptional activation.
miRNA‐106a and prostate cancer radioresistance: a novel role for LITAF in ATM regulation
Authors: Hoey Christianne , Ray Jessica , Jeon Jouhyun , Huang Xiaoyong , Taeb Samira , Ylanko Jarkko , Andrews David W. , Boutros Paul C. , Liu Stanley K.
Published: May 2018

Recurrence of high‐grade prostate cancer after radiotherapy is a significant clinical problem, resulting in increased morbidity and reduced patient survival. The molecular mechanisms of radiation resistance are being elucidated through the study of microRNA (miR) that negatively regulate gene expression. We performed bioinformatics analyses of The Cancer Genome Atlas (TCGA) dataset to evaluate the association between miR‐106a and its putative target lipopolysaccharide‐induced TNF‐α factor (LITAF) in prostate cancer. We characterized the function of miR‐106a through in vitro and in vivo experiments and employed transcriptomic analysis, western blotting, and 3′UTR luciferase assays to establish LITAF as a bona fide target of miR‐106a. Using our well‐characterized radiation‐resistant cell lines, we identified that miR‐106a was overexpressed in radiation‐resistant cells compared to parental cells. In the TCGA, miR‐106a was significantly elevated in high‐grade human prostate tumors relative to intermediate‐ and low‐grade specimens. An inverse correlation was seen with its target, LITAF. Furthermore, high miR‐106a and low LITAF expression predict for biochemical recurrence at 5 years after radical prostatectomy. miR‐106a overexpression conferred radioresistance by increasing proliferation and reducing senescence, and this was phenocopied by knockdown of LITAF. For the first time, we describe a role for miRNA in upregulating ATM expression. LITAF, not previously attributed to radiation response, mediates this interaction. This route of cancer radioresistance can be overcome using the specific ATM kinase inhibitor, KU‐55933. Our research provides the first report of miR‐106a and LITAF in prostate cancer radiation resistance and high‐grade disease, and presents a viable therapeutic strategy that may ultimately improve patient outcomes.
Breaking script: Deviations and postevent information in adult memory for a repeated event
Authors: MacLean Carla L. , Coburn Patricia I. , Chong Kristin , Connolly Deborah L.
Published: May 2018

Witnesses to industrial incidents may be asked to recall a single instance of a familiar event. This research systematically tested if deviations to what typically occurs and postevent information (PEI) enhanced reporting of an instance of a repeated event. Across 2 experiments, each participant experienced 5 food‐tasting instances; these instances comprised the repeated event. Half of the participants in both Experiments 1 (continuous deviation setting) and 2 (continuous deviation integrated) experienced a deviation to how the third instance occurred. Also, half of the participants in both experiments received PEI about the third instance. All participants demonstrated superior reporting for the first instance of the repeated event. The continuous deviation setting in Experiment 1 enhanced reporting for all 5 instances of the repeated event (general effect). In Experiment 2, participants who received a continuous deviation integrated and PEI demonstrated superior reporting for the first and third instances of the event (targeted effect).
Neutrophil Chemotaxis in Moving Gradients
Authors: Qasaimeh Mohammad A. , Pyzik Michal , Astolfi Mélina , Vidal Silvia M. , Juncker David
Published: May 2018

Neutrophils are known to rapidly migrate to sites of infection and injury, and track bacteria guided by spatiotemporally controlled chemokine gradients. Previous studies of neutrophil chemotaxis, using micropipettes and lately microfluidic devices, are limited to stationary sources and gradients. Thus, despite the well‐known ability of neutrophils to track bacteria in vitro, their response to defined moving gradients remains unknown. Here, a “floating” concentration gradient of interleukin‐8 is generated using a microfluidic quadrupole, and neutrophils cultured in a Petri dish are challenged with steep stationary and moving gradients. Individual neutrophils are tracked by live microscopy and their chemotaxis is analyzed. Interestingly, neutrophils are shown to enter the gradient region in a rolling‐like behavior, rapidly adhere to the bare dish, and polarize within 30 s, faster than what has been observed to date. Under stationary gradients, neutrophil migration length is maximal for cells located at the low end of the gradient, whereas under moving gradients, neutrophils migrate over longer distances and the length travelled is independent of their starting position. Furthermore, neutrophils are shown to initiate their migration at a maximum speed, slowing down when migrating deeper into the gradient and eventually stopping. This work lays the foundation for future chemotaxis assays with moving gradients.
Effects of Heat Treatment on Microstructure and Mechanical Properties of an ECAPed Al–Zn–Mg–Cu Alloy
Authors: Li Jinghui , Li Fuguo , Ma Xinkai , Li Jiang , Liang Shan , Zhang Long
Published: May 2018

Equal‐channel angular pressing (ECAP) has a considerable advantage in the preparation of bulk fine‐grained alloys. To investigate the effect of solid solution treatment (SST) on the microstructure and mechanic properties of an Al–Zn–Mg–Cu alloy after ECAP, a comparative study is conducted using experimental techniques. It is shown that ECAP processing introduces a strong grain refinement, while the SST induces precipitation of skeleton‐like second phases distributed discontinuously at the grain boundary and needle‐like second phases in the grain. In addition, SST can also improve significantly the fractions of both high angle grain boundaries and recrystallization. The {110}<001> texture is introduced and the polar density is reduced during SST. Microstructural evolution involves three typical characteristics, namely, shear bands, substructure, and precipitates. The corresponding mechanism of microstructure evolution is proposed, considering the effect of dislocations, precipitates, and grain boundaries. After SST, the improvement of strength and hardness is not obvious, but significant in plasticity by 33.3%. Different strengthening mechanisms are also examined during ECAP and subsequent SST.
Laser‐Textured Metal Substrates as Photoanodes for Enhanced PEC Water Splitting Reactions
Authors: Bialuschewski Danny , Hoppius Jan S. , Frohnhoven Robert , Deo Meenal , Gönüllü Yakup , Fischer Thomas , Gurevich Evgeny L. , Mathur Sanjay
Published: May 2018

We demonstrate the effect of femtosecond laser structuring of titanium substrates to increase the absorption, photoconversion, and overall photoelectrochemical water splitting (PEC) performance compared to pristine metal substrates, independent of any additional top coat layers. The influence of ultra short laser pulse patterning on PEC efficiency is investigated toward spectroscopic (UV‐Vis), microscopic (SEM), crystallographic (XRD), and compositional (XPS) properties. The beneficial effect of a periodically patterned substrate is attributed to enhanced specific surface area and improved in‐plane light trapping when compared to flat surfaces. Photoanodes for water splitting experiments fabricated by titanium and iron oxide films on laser pre‐patterned Ti substrates are also found to show enhanced PEC efficiency (0.057 mA cm−2) when compared to unpatterened substrates (0.028 mA cm−2). The lower absolute PEC efficiencies are due to extreme thin films.
Additive Manufacturing of Porous Structures for Unmanned Aerial Vehicles Applications
Authors: Klippstein Helge , Hassanin Hany , Diaz De Cerio Sanchez Alejandro , Zweiri Yahya , Seneviratne Lakmal
Published: May 2018

Unmanned aerial vehicles (UAVs) have shown promising benefits in many applications. This has been enabled by the emergence of additive manufacturing (AM), which give the designers a large amount of geometrical freedom. In this paper, a novel design process of fused deposition modeling (FDM) combining both topology and infill optimization is introduced for AM of high performance porous structures. Tensile testing of FDM printed samples is first carried out to study the effect of the build orientation on the mechanical properties of acrylonitrile butadiene styrene (ABS) samples. It is found that samples built perpendicular to the load axis are the weakest with a tensile strength of 29 MPa and Young's modulus of 1960 MPa. The materials properties are fed to the finite elements analysis (FEA) for geometrical topology optimization, aiming to maximize stiffness and reduce weight of those parts. Afterwards, an infill optimization is carried out on the topology optimized parts using different mesostructures such as honeycomb, triangular, and rectangular to achieve high structural performance. The results showed that triangular pattern with 50% infill density had the lowest developed stresses, less mass, and strain energy when compared to other structures. Optimum UAVs parts of a quadcopter are successfully manufactured, assembled, and tested.
Stepwise Degradable Nanocarriers Enabled Cascade Delivery for Synergistic Cancer Therapy
Authors: Yang Yannan , Lu Yao , Abbaraju Prasanna Lakshmi , Azimi Iman , Lei Chang , Tang Jie , Jambhrunkar Manasi , Fu Jianye , Zhang Min , Liu Yang , Liu Chao , Yu Chengzhong
Published: May 2018

Hypoxia‐activated prodrugs have brought new opportunities for safe and effective tumor ablation, but their therapeutic efficacy is limited by insufficient activation in tumor microenvironments. Herein, a novel cascade delivery system with tandem functions by integrating a hypoxia‐activated prodrug (AQ4N) and glucose oxidase (GOx) is designed to improve its efficacy. Innovative yolk–shell organosilica nanoparticles with a tetrasulfide bridged composition, a small‐pore yolk, and a large‐pore shell featuring a shell‐to‐yolk stepwise degradability are constructed as a carrier for AQ4N and GOx, one enzyme that catalyzes the oxidation of glucose to produce hydrogen peroxide. The glutathione (GSH) is depleted by tetrasulfide bond in the framework and induces shell degradation for fast release of GOx, which in turn induces starvation (glucose removal), oxidative cytotoxicity (H2O2 production and GSH depletion), and hypoxia (oxygen consumption). Finally, the hypoxia activates the liberated prodrug AQ4N for chemotherapy. The cascading and synergistic functions including GSH depletion, starvation, oxidative cytotoxicity, and chemotherapy lead to improved performance in tumor inhibition and antimetastasis.
Yellow‐Colored Electro‐Optic Crystals as Intense Terahertz Wave Sources
Authors: Jeong Chan‐Uk , Kang Bong Joo , Lee Seung‐Heon , Lee Seung‐Chul , Kim Won Tae , Jazbinsek Mojca , Yoon Woojin , Yun Hoseop , Kim Dongwook , Rotermund Fabian , Kwon O‐Pil
Published: May 2018

This study presents newly developed yellow‐colored organic electro‐optic crystals to provide high terahertz (THz) wave generation efficiency. Compared with currently existing red‐ or orange‐colored electro‐optic crystals, which are used for most benchmark organic THz sources, yellow‐colored crystals have additional superior advantages for THz wave generation, e.g., higher transparency in the visible wavelength range with accompanying different phase‐matching possibilities. The new yellow‐colored crystals consist of a highly nonlinear optical 4‐(4‐hydroxystyryl)‐1‐methylpyridinium (OHP) cation, with a relatively short wavelength of maximal absorption at 390 nm in solution, and various halogen‐substituted benzenesulfonate anions, with strong secondary‐bonding ability. OHP 4‐chlorobenzenesulfonate (OHP‐CBS) crystals exhibit large off‐resonant macroscopic optical nonlinearity and high transparency, with a cut‐off wavelength for solid‐state absorption near 490 nm. OHP‐CBS crystals provide excellent THz wave generation characteristics based on optical rectification. A 0.53 mm thick OHP‐CBS crystal delivers ≈27 times higher optical‐to‐THz conversion efficiency and a much broader spectrum bandwidth compared with the standard 1.0 mm thick ZnTe at 1300 nm pumping. Particularly, compared with a benchmark organic quinolinium crystal with a similar thickness of 0.55 mm, OHP‐CBS crystals exhibit 1.7 times higher optical‐to‐THz conversion efficiency, and show a significantly different THz spectral shape.
Off/On Fluorescent Nanoparticles for Tunable High‐Temperature Threshold Sensing
Authors: Julià López Alex , Ruiz‐Molina Daniel , Landfester Katharina , Bannwarth Markus B. , Roscini Claudio
Published: May 2018

Herein, a versatile threshold temperature sensor based on the glass transition temperature‐triggered fluorescence activation of a dye/developer duo, encapsulated in polymeric nanoparticles is reported. The emission enhancement, detectable even by unaided eye is completed within a narrow temperature range and activates at adjustable threshold temperatures up to 200 °C. Fluorescence is chosen as sensing probe due to its high detection sensitivity together with an advanced spatial and temporal resolution. The strategy is based on nanoparticles prepared from standard thermoplastic polymers, a fluorescence developer, and the commercially available Rhodamine B base dye, a well‐known and widely used fluorescent molecule. By making nanoparticles of different thermoplastic polymers, fast, abrupt, and irreversible disaggregation induced fluorescence enhancement, with tunable threshold temperature depending on the nanoparticles polymer glass transition is achieved. As a proof‐of‐concept for the versatility of this novel family of NPs, their use for sensing the thermal history of environments and surfaces exposed to the threshold temperature is showed.
Microstructure Evolution of Concentration Gradient Li[Ni0.75Co0.10Mn0.15]O2 Cathode for Lithium‐Ion Batteries
Authors: Yoon Chong S. , Kim Suk Jun , Kim Un‐Hyuck , Park Kang‐Joon , Ryu Hoon‐Hee , Kim Hee‐Soo , Sun Yang‐Kook
Published: May 2018

Detailed analysis of the microstructural changes during lithiation of a full‐concentration‐gradient (FCG) cathode with an average composition of Li[Ni0.75Co0.10Mn0.15]O2 is performed starting from its hydroxide precursor, FCG [Ni0.75Co0.10Mn0.15](OH)2 prior to lithiation. Transmission electron microscopy (TEM) reveals that a unique rod‐shaped primary particle morphology and radial crystallographic texture are present in the prelithiation stage. In addition, TEM detected a two‐phase structure consisting of MnOOH and Ni(OH)2, and crystallographic twins of MnOOH on the Mn‐rich precursor surface. The formation of numerous twins is driven by the lattice mismatch between MnOOH and Ni(OH)2. Furthermore, the twins persist in the lithiated cathode; however, their density decrease with increasing lithiation temperature. Cation disordering, which influences cathode performance, is observed to continuously decrease with increasing lithiation temperature with a minimum observed at 790 °C. Consequently, lithiation at 790 °C (for 10 h) produced optimal discharge capacity and cycling stability. Above 790 °C, an increase in cation disordering and excessive coarsening of the primary particles lead to the deterioration of electrochemical properties. The twins in the FCG cathode precursor may promote the optimal primary particle morphology by retarding the random coalescence of primary particles during lithiation, effectively preserving both the morphology and crystallographic texture of the precursor.
Defect Restoration of Low‐Temperature Sol‐Gel‐Derived ZnO via Sulfur Doping for Advancing Polymeric Schottky Photodiodes
Authors: Kim Kyounghwan , Sim Kyu Min , Yoon Seongwon , Jang Min Su , Chung Dae Sung
Published: May 2018

This study shows that the deep‐level defect states in sol‐gel‐derived ZnO can be efficiently restored by facile sulfur doping chemistry, wherein the +2 charged oxygen vacancies are filled with the S2− ions brought by thiocyanate. By fabricating a solution‐processed polymeric Schottky diode with ITO/ZnO as the cathode, the synergetic effects of such defect‐restored ZnO electron selective layers are demonstrated. The decreased chemical defects and thus reduced mid‐gap states enable to not only enlarge the effective built‐in potential, which can expand the width of the depletion region, but also increase the Schottky energy barrier, which can reduce undesired dark‐current injection. As a result, the demonstrated simple‐structure blue‐selective polymeric Schottky photodiode renders near‐ideal diode operation with an ideality factor of 1.18, a noise equivalent power of 1.25 × 10−14 W Hz−1/2, and a high peak detectivity of 2.4 × 1013 Jones. In addition, the chemical robustness of sulfur‐doped ZnO enables exceptional device stability against air exposure as well as device‐to‐device reproducibility. Therefore, this work opens the possibility of utilizing low‐temperature sol‐gel‐derived ZnO in realizing high‐performance, stable, and reliable organic photodiodes that could be employed in the design of practical image sensors.
Organic–Inorganic Hybrid Halide Perovskites for Memories, Transistors, and Artificial Synapses
Authors: Choi Jaeho , Han Ji Su , Hong Kootak , Kim Soo Young , Jang Ho Won
Published: May 2018

Fascinating characteristics of halide perovskites (HPs), which cannot be seen in conventional semiconductors and metal oxides, have boosted the application of HPs in electronic devices beyond optoelectronics such as solar cells, photodetectors, and light‐emitting diodes. Here, recent advances in HP‐based memory and logic devices such as resistive‐switching memories (i.e., resistive random access memory (RRAM) or memristors), transistors, and artificial synapses are reviewed, focusing on inherently exotic properties of HPs: i) tunable bandgap, ii) facile majority carrier control, iii) fast ion migration, and iv) superflexibility. Various fabrication techniques of HP thin films from solution‐based methods to vacuum processes are introduced. Up‐to‐date work in the field, emphasizing the compositional flexibility of HPs, suggest that HPs are promising candidates for next‐generation electronic devices. Taking advantages of their unique electrical properties, low‐cost and low‐temperature synthesis, and compositional and mechanical flexibility, HPs have enormous potential to provide a new platform for future electronic devices and explosively intensive studies will pave the way in finding new HP materials beyond conventional silicon‐based semiconductors to keep up with “More‐than‐Moore” times.
Inverse Opal Scaffolds with Gradations in Mineral Content for Spatial Control of Osteogenesis
Authors: Zhu Chunlei , Qiu Jichuan , Pongkitwitoon Suphannee , Thomopoulos Stavros , Xia Younan
Published: May 2018

The design and fabrication of inverse opal scaffolds with gradations in mineral content to achieve spatial control of osteogenesis are described. The gradient in mineral content is established via the diffusion‐limited transport of hydroxyapatite nanoparticles in a closely packed lattice of gelatin microbeads. The mineral‐graded scaffold has an array of uniform pores and interconnected windows to facilitate efficient transport of nutrients and metabolic wastes, ensuring high cell viability. The graded distribution of mineral content can provide biochemical and mechanical cues for spatially regulating the osteogenic differentiation of adipose‐derived stromal cells. This new class of scaffolds holds promise for engineering the interfaces between mineralized and unmineralized tissues.
Tissue Mimicry in Morphology and Composition Promotes Hierarchical Matrix Remodeling of Invading Stem Cells in Osteochondral and Meniscus Scaffolds
Authors: Stuckensen Kai , Schwab Andrea , Knauer Markus , Muiños‐López Emma , Ehlicke Franziska , Reboredo Jenny , Granero‐Moltó Froilán , Gbureck Uwe , Prósper Felipe , Walles Heike , Groll Jürgen
Published: May 2018

An integral approach toward in situ tissue engineering through scaffolds that mimic tissue with regard to both tissue architecture and biochemical composition is presented. Monolithic osteochondral and meniscus scaffolds are prepared with tissue analog layered biochemical composition and perpendicularly oriented continuous micropores by a newly developed cryostructuring technology. These scaffolds enable rapid cell ingrowth and induce zonal‐specific matrix synthesis of human multipotent mesenchymal stromal cells solely through their design without the need for supplementation of soluble factors such as growth factors.
Quantifying Polaron Formation and Charge Carrier Cooling in Lead‐Iodide Perovskites
Authors: Bretschneider Simon A. , Ivanov Ivan , Wang Hai I. , Miyata Kiyoshi , Zhu Xiaoyang , Bonn Mischa
Published: May 2018

Notwithstanding the success of lead‐halide perovskites in emerging solar energy conversion technologies, many of the fundamental photophysical phenomena in this material remain debated. Here, the initial steps following photogeneration of free charge carriers in lead‐iodide perovskites are studied, and timescales of charge carrier cooling and polaron formation, as a function of temperature and charge carrier excess energy, are quantified. It is found, using terahertz time‐domain spectroscopy (THz‐TDS), that the observed femtosecond rise in the photoconductivity can be described very well using a simple model of sequential charge carrier cooling and polaron formation. For excitation above the bandgap, the carrier cooling time depends on the charge carrier excess energy and lattice temperature, with cooling rates varying between 1 and 6 meV fs−1, depending on the cation. While carrier cooling depends on the cation, polaron formation occurs within ≈400 fs in CH3NH3PbI3(MAPbI3), CH(NH2)2PbI3(FAPbI3), and CsPbI3. Its formation time is independent of temperature between 160 and 295 K. The very similar polaron formation dynamics observed for the three perovskites points to the critical role of the inorganic lattice, rather than the cations, for polaron formation.
A 1300 mm2 Ultrahigh‐Performance Digital Imaging Assembly using High‐Quality Perovskite Single Crystals
Authors: Liu Yucheng , Zhang Yunxia , Zhao Kui , Yang Zhou , Feng Jiangshan , Zhang Xu , Wang Kang , Meng Lina , Ye Haochen , Liu Ming , Liu Shengzhong (Frank)
Published: May 2018

By fine‐tuning the crystal nucleation and growth process, a low‐temperature‐gradient crystallization method is developed to fabricate high‐quality perovskite CH3NH3PbBr3 single crystals with high carrier mobility of 81 ± 5 cm2 V−1 s−1 (>3 times larger than their thin film counterpart), long carrier lifetime of 899 ± 127 ns (>5 times larger than their thin film counterpart), and ultralow trap state density of 6.2 ± 2.7 × 109 cm−3 (even four orders of magnitude lower than that of single‐crystalline silicon wafers). In fact, they are better than perovskite single crystals reported in prior work: their application in photosensors gives superior detectivity as high as 6 × 1013 Jones, ≈10–100 times better than commercial sensors made of silicon and InGaAs. Meanwhile, the response speed is as fast as 40 µs, ≈3 orders of magnitude faster than their thin film devices. A large‐area (≈1300 mm2) imaging assembly composed of a 729‐pixel sensor array is further designed and constructed, showing excellent imaging capability thanks to its superior quality and uniformity. This opens a new possibility to use the high‐quality perovskite single‐crystal‐based devices for more advanced imaging sensors.
Laminated Object Manufacturing of 3D‐Printed Laser‐Induced Graphene Foams
Authors: Luong Duy Xuan , Subramanian Ajay K. , Silva Gladys A. Lopez , Yoon Jongwon , Cofer Savannah , Yang Kaichun , Owuor Peter Samora , Wang Tuo , Wang Zhe , Lou Jun , Ajayan Pulickel M. , Tour James M.
Published: May 2018

Laser‐induced graphene (LIG), a graphene structure synthesized by a one‐step process through laser treatment of commercial polyimide (PI) film in an ambient atmosphere, has been shown to be a versatile material in applications ranging from energy storage to water treatment. However, the process as developed produces only a 2D product on the PI substrate. Here, a 3D LIG foam printing process is developed on the basis of laminated object manufacturing, a widely used additive‐manufacturing technique. A subtractive laser‐milling process to yield further refinements to the 3D structures is also developed and shown here. By combining both techniques, various 3D graphene objects are printed. The LIG foams show good electrical conductivity and mechanical strength, as well as viability in various energy storage and flexible electronic sensor applications.
A Living‐Dead Magnetic Layer at the Surface of Ferrimagnetic DyTiO3 Thin Films
Authors: Aeschlimann Raphaël , Preziosi Daniele , Scheiderer Philipp , Sing Michael , Valencia Sergio , Santamaria Jacobo , Luo Chen , Ryll Hanjo , Radu Florin , Claessen Ralph , Piamonteze Cinthia , Bibes Manuel
Published: May 2018

When ferromagnetic films become ultrathin, key properties such as the Curie temperature and the saturation magnetization are usually depressed. This effect is thoroughly investigated in magnetic oxides such as half‐metallic manganites, but much less in ferrimagnetic insulating perovskites such as rare‐earth titanates RTiO3, despite their appeal to design correlated 2D electron gases. Here, the magnetic properties of epitaxial DyTiO3 thin films are reported. While films thicker than about 50 nm show a bulk‐like response, at low thickness a surprising increase of the saturation magnetization is observed. This behavior is described using a classical model of a “dead layer” but assuming that this layer is actually “living,” that is, it responds to the magnetic field with a strong paramagnetic susceptibility. Through depth‐dependent X‐ray absorption and photoemission spectroscopy, it is shown that the “living‐dead layer” corresponds to surface regions where magnetic (S = 1/2) Ti3+ ions are replaced by nonmagnetic Ti4+ ions. Hysteresis cycles at the Dy M5 and Ti L3 edges indicate that the surface Ti4+ ions decouple the Dy3+ ions, thus unleashing their strong paramagnetic response. Finally, it is shown how capping the DyTiO3 film can help increase the Ti3+ content near the surface and thus recover a better ferrimagnetic behavior.
An Unprecedented Stimuli‐Controlled Single‐Crystal Reversible Phase Transition of a Metal–Organic Framework and Its Application to a Novel Method of Guest Encapsulation
Authors: Tan Fangchang , López‐Periago Ana , Light Mark E. , Cirera Jordi , Ruiz Eliseo , Borrás Alejandro , Teixidor Francesc , Viñas Clara , Domingo Concepción , Planas José Giner
Published: May 2018

The flexibility and unexpected dynamic behavior of a third‐generation metal–organic framework are described for the first time. The synthetic strategy is based on the flexibility and spherical shape of dipyridyl‐based carborane linkers that act as pillars between rigid Co/BTB (BTB: 1,3,5‐benzenetricarboxylate) layers, providing a 3D porous structure (1). A phase transition of the solid can be induced to generate a new, nonporous 2D structure (2) without any loss of the carborane linkers. The structural transformation is visualized by snapshots of the multistep single‐crystal‐to‐single‐crystal transformation by single‐crystal and powder X‐ray diffraction. Poor hydrogen bond acceptors such as MeOH, CHCl3 or supercritical CO2 induce such a 3D to 2D transformation. Remarkably, the transformation is reversible and the 2D phase 2 is further converted back into 1 by heating in dimethylformamide. The energy requirements involved in such processes are investigated using periodic density functional theory calculations. As a proof of concept for potential applications, encapsulation of C60 is achieved by trapping this molecule during the reversible 2D to 3D phase transition, whereas no adsorption is observed by straight solvent diffusion into the pores of the 3D phase.
Green Fabrication of Amphiphilic Quaternized β‐Chitin Derivatives with Excellent Biocompatibility and Antibacterial Activities for Wound Healing
Authors: Xu Huan , Fang Zehong , Tian Weiqun , Wang Yanfeng , Ye Qifa , Zhang Lina , Cai Jie
Published: May 2018

Bacterial infection has always been a great threat to public health, and new antimicrobials to combat it are urgently needed. Here, a series of quaternized β‐chitin derivatives is prepared simply and homogeneously in an aqueous KOH/urea solution, which is a high‐efficiency, energy‐saving, and “green” route for the modification of chitin. The mild reaction conditions keep the acetamido groups of β‐chitin intact and introduce quaternary ammonium groups on the primary hydroxyl at the C‐6 position of the chitin backbone, allowing the quaternized β‐chitin derivatives (QCs) to easily form micelles. These QCs are found to exhibit excellent antimicrobial activities against Escherichia coli, Staphylococcus aureus, Candida albicans, and Rhizopus oryzae with minimum inhibitory concentrations (MICs) of 8, 12, 60, and 40 µg mL−1, respectively. As a specific highlight, their inherent outstanding biocompatibility and significant accelerating effects on the healing of uninfected, E. coli‐infected, and S. aureus‐infected wounds imply that these novel polysaccharide‐based materials can be used as dressings for clinical skin regeneration, particularly for infected wounds.