bluuebunny/crossref_metadata_2025 huggingface dataset:
DUST DIFFUSION AND SETTLING IN THE PRESENCE OF COLLISIONS: TRAPPING (SUB)MICRON GRAINS IN THE MIDPLANE
Authors: Krijt Sebastiaan , Ciesla Fred J.
Published: May 2016

In protoplanetary disks, the distribution and abundance of small (sub)micron grains are important for a range of physical and chemical processes. For example, they dominate the optical depth at short wavelengths and their surfaces are the sites of many important chemical reactions, such as the formation of water. Based on their aerodynamical properties (i.e., their strong dynamical coupling with the surrounding gas) it is often assumed that these small grains are well-mixed with the gas. Our goal is to study the vertical (re)distribution of grains taking into account settling, turbulent diffusion, and collisions with other dust grains. Assuming a fragmentation-limited background dust population, we developed a Monte Carlo approach that follows single monomers as they move through a vertical column of gas and become incorporated in different aggregates as they undergo sticking and fragmenting collisions. We find that (sub)micron grains are not necessarily well-mixed vertically, but can become trapped in a thin layer with a scale height that is significantly smaller than that of the gas. This collisional trapping occurs when the timescale for diffusion is comparable to or longer than the collision timescale in the midplane and its effect is strongest when the most massive particles in the size distribution show significant settling. Based on simulations and analytical considerations, we conclude that for typical dust-to-gas ratios and turbulence levels, the collisional trapping of small grains should be a relatively common phenomenon. The absence of trapping could then indicate a low dust-to-gas ratio, possibly because a large portion of the dust mass has been removed through radial drift or is locked up in planetesimals.
FREQUENCY MODULATION OF DIRECTLY IMAGED EXOPLANETS: GEOMETRIC EFFECT AS A PROBE OF PLANETARY OBLIQUITY
Authors: Kawahara Hajime
Published: May 2016

We consider the time–frequency analysis of a scattered light curve of a directly imaged exoplanet. We show that the geometric effect due to planetary obliquity and orbital inclination induce the frequency modulation of the apparent diurnal periodicity. We construct a model of the frequency modulation and compare it with the instantaneous frequency extracted from the pseudo-Wigner distribution of simulated light curves of a cloudless Earth. The model provides good agreement with the simulated modulation factor, even for the light curve with Gaussian noise comparable to the signal. Notably, the shape of the instantaneous frequency is sensitive to the difference between the prograde, retrograde, and pole-on spin rotations. While our technique requires the albedo map to be static, it does not need to solve the albedo map of the planet. The time–frequency analysis is complementary to other methods which utilize the amplitude modulation. This paper demonstrates the importance of the frequency domain of the photometric variability for the characterization of directly imaged exoplanets in future research.
HESS J1943+213: A NON-CLASSICAL HIGH-FREQUENCY-PEAKED BL LAC OBJECT
Authors: Straal S. M. , Gabányi K. É. , Leeuwen J. van , Clarke T. E. , Dubner G. , Frey S. , Giacani E. , Paragi Z.
Published: May 2016

HESS J1943+213 is an unidentified TeV source that is likely a high-frequency-peaked BL Lac (HBL) object, but that is also compatible with a pulsar wind nebula (PWN) nature. Each of these enormously different astronomical interpretations is supported by some of the observed unusual characteristics. In order to finally classify and understand this object, we took a three-pronged approach, through time-domain, high angular resolution, and multi-frequency radio studies. First, our deep time-domain observations with the Arecibo telescope failed to uncover the putative pulsar powering the proposed PWN. We conclude with ∼70% certainty that HESS J1943+213 does not host a pulsar. Second, long-baseline interferometry of the source with e-MERLIN at 1.5 and 5 GHz shows only a core, that is, a point source at

–100 mas resolution. Its 2013 flux density is about one-third lower than that detected in the 2011 observations with similar resolution. This radio variability of the core strengthens the HBL object hypothesis. Third, additional evidence against the PWN scenario comes from the radio spectrum we compiled. The extended structure follows a power-law behavior with spectral index

while the core component displays a flat spectrum (

). In contrast, the radio synchrotron emission of PWNe predicts a single power-law distribution. Overall, we rule out the PWN hypothesis and conclude that the source is a BL Lac object. The consistently high fraction (70%) of the flux density from the extended structure then leads us to conclude that HESS J1943+213 must be a non-classical HBL object.
THE COMPLETE, TEMPERATURE RESOLVED EXPERIMENTAL SPECTRUM OF METHYL FORMATE (HCOOCH3) BETWEEN 214.6 AND 265.4 GHz
Authors: McMillan James P. , Fortman Sarah M. , Neese Christopher F. , Lucia Frank C. De
Published: May 2016

Because methyl formate (HCOOCH3) is abundant in the interstellar medium and has a strong, complex spectrum, it is a major contributor to the list of identified astrophysical lines. Because of its spectral complexity, with many low lying torsional and vibrational states, the quantum mechanical (QM) analysis of its laboratory spectrum is challenging and thus incomplete. As a result it is assumed that methyl formate is also one of the major contributors to the lists of unassigned lines in astrophysical spectra. This paper provides a characterization, without the need for QM analysis, of the spectrum of methyl formate between 214.6 and 265.4 GHz for astrophysically significant temperatures. The experimental basis for this characterization is a set of 425 spectra, with absolute intensity calibration, recorded between 248 and 408 K. Analysis of these spectra makes possible the calculation of the Complete Experimental Spectrum of methyl formate as a function of temperature. Of the 7132 strongest lines reported in this paper, 2523 are in the QM catalogs. Intensity differences of 5%–10% from those calculated via QM models were also found. Results are provided in a frequency point-by-point catalog that is well suited for the simulation of overlapped spectra. The common astrophysical line frequency, line strength, and lower state energy catalog is also provided.
PAIRS AND GROUPS OF GENETICALLY RELATED LONG-PERIOD COMETS AND PROPOSED IDENTITY OF THE MYSTERIOUS LICK OBJECT OF 1921
Authors: Sekanina Zdenek , Kracht Rainer
Published: May 2016

We present the history of investigation of the dynamical properties of pairs and groups of genetically related long-period comets (other than the Kreutz sungrazing system). Members of a comet pair or group move in nearly identical orbits, and their origin as fragments of a common parent comet is unquestionable. The only variable is the time of perihelion passage, which differs considerably from member to member owing primarily to an orbital-momentum increment acquired during breakup. Meter-per-second separation velocities account for gaps of years or tens of years, thanks to the orbital periods of many millennia. The physical properties of individual members may not at all be alike, as illustrated by the trio of C/1988 A1, C/1996 Q1, and C/2015 F3. We exploit orbital similarity to examine whether the enigmatic and as-yet-unidentified object discovered from the Lick Observatory near the Sun at sunset on 1921 August 7 happened to be a member of such a pair and to track down the long-period comet to which it might be genetically related. Our search shows that the Lick object, which could not be a Kreutz sungrazer, was likely a companion to comet C/1847 C1 (Hind), whose perihelion distance was ∼9 R
⊙ and true orbital period was approximately 8300 yr. The gap of 74.4 yr between their perihelion times is consistent with a separation velocity of ∼1 m s−1 which sets the fragments apart following the parent's breakup in a general proximity of perihelion during the previous return to the Sun in the seventh millennium BCE.
FIRST DETECTION OF GAS-PHASE METHANOL IN A PROTOPLANETARY DISK
Authors: Walsh Catherine , Loomis Ryan A. , Öberg Karin I. , Kama Mihkel , van ’t Hoff Merel L. R. , Millar Tom J. , Aikawa Yuri , Herbst Eric , Widicus Weaver Susanna L. , Nomura Hideko
Published: May 2016

The first detection of gas-phase methanol in a protoplanetary disk (TW Hya) is presented. In addition to being one of the largest molecules detected in disks to date, methanol is also the first disk organic molecule with an unambiguous ice chemistry origin. The stacked methanol emission, as observed with the Atacama Large Millimeter/submillimeter Array, is spectrally resolved and detected across six velocity channels (

>
3
σ

), reaching a peak signal-to-noise of

5.5
σ

, with the kinematic pattern expected for TW Hya. Using an appropriate disk model, a fractional abundance of

3
×

10

−
12

–
4
×

10

−
11

(with respect to H2) reproduces the stacked line profile and channel maps, with the favored abundance dependent upon the assumed vertical location (midplane versus molecular layer). The peak emission is offset from the source position, suggesting that the methanol emission has a ring-like morphology: the analysis here suggests it peaks at

≈
30

au

, reaching a column density

≈
3
–
6
×

10

12

cm−2. In the case of TW Hya, the larger (up to millimeter-sized) grains, residing in the inner 50 au, may thus host the bulk of the disk ice reservoir. The successful detection of cold gas-phase methanol in a protoplanetary disk implies that the products of ice chemistry can be explored in disks, opening a window into studying complex organic chemistry during planetary system formation.
SPIRAL WAVES TRIGGERED BY SHADOWS IN TRANSITION DISKS
Authors: Montesinos Matías , Perez Sebastian , Casassus Simon , Marino Sebastian , Cuadra Jorge , Christiaens Valentin
Published: May 2016

Circumstellar asymmetries such as central warps have recently been shown to cast shadows on outer disks. We investigate the hydrodynamical consequences of such variable illumination on the outer regions of a transition disk, and the development of spiral arms. Using 2D simulations, we follow the evolution of a gaseous disk passively heated by the central star, under the periodic forcing of shadows with an opening angle of ∼28°. With a lower pressure under the shadows, each crossing results in a variable azimuthal acceleration, which in time develops into spiral density waves. Their pitch angles evolve from Π ∼ 15°–22° at the onset, to ∼11°–14°, over ∼65 au to 150 au. Self-gravity enhances the density contrast of the spiral waves, as also reported previously for spirals launched by planets. Our control simulations with unshadowed irradiation do not develop structures, except for a different form of spiral waves seen at later times only in the gravitationally unstable control case. Scattered light predictions in the H-band show that such illumination spirals should be observable. We suggest that spiral arms in the case-study transition disk HD 142527 could be explained as a result of shadowing from the tilted inner disk.
PROBABILISTIC INFERENCE OF BASIC STELLAR PARAMETERS: APPLICATION TO FLICKERING STARS*
Authors: Angus Ruth , Kipping David. M.
Published: May 2016

The relations between observable stellar parameters are usually assumed to be deterministic. That is, given an infinitely precise measurement of independent variable, “x”, and some model, the value of dependent variable, “y” can be known exactly. In practice this assumption is rarely valid and intrinsic stochasticity means that two stars with exactly the same “x” will have slightly different “y”s. The relation between short-timescale brightness fluctuations (flicker) of stars and both surface gravity and stellar density are two such stochastic relations that have until now been treated as deterministic ones. We recalibrate these relations in a probabilistic framework, using hierarchical Bayesian modeling to constrain the instrinsic scatter in the relations. We find evidence for additional scatter in the relationship, that cannot be accounted for by the observational uncertainties alone. The scatter in surface gravity and stellar density does not depend on flicker, suggesting that using flicker as a proxy for

log
g

and ρ
⋆ is equally valid for dwarf and giant stars, despite the fact that the observational uncertainties tend to be larger for dwarfs.
New records of Gerromorpha and Nepomorpha (Insecta: Hemiptera: Heteroptera) from South America
Authors: Moreira Felipe , Rodrigues Higor , Barbosa Julianna , Reduciendo Klementová Barbora , Svitok Marek
Published: May 2016

Aquatic and semiaquatic Heteroptera occur on all continents except Antarctica and occupy a wide variety of habitats, including lentic and lotic water bodies, perennial or temporary. In the Neotropical Region, there is a lack of knowledge concerning the geographical distribution of most represented species, which can only be solved by the collection of specimens in under-studied areas and publication of new records and lists of species.

New records are presented for eleven species of Gerromorpha and ten Nepomorpha, including first records from Venezuela (Brachymetra lata, Limnogonus hyalinus, Rhagovelia evidis, Tenagobia peruana, Limnocoris burmeisteri, L. fittkaui fittkaui, Placomerus micans, and Martarega gonostyla), the Venezuelan State of Bolívar (Cylindrostethus palmaris, R. elegans, R. tenuipes, and Ambrysus stali), the Brazilian State of Bahia (Martarega bentoi), Peru (Euvelia lata), and the Peruvian Region of Arequipa (Microvelia pulchella).
Une approche spatiale des instruments de l’action publique : l’exemple des réformes du secteur de la santé en Inde
Authors: Eliot Emmanuel
Published: May 2016

Dans de nombreux pays du monde, les systèmes de soins sont affectés par des réformes de nature politique, organisationnelle et financière. Ces dernières contribuent à renforcer la concurrence, multiplier les interactions entre acteurs publics et privés et entre le local et le global. À partir de l’exemple du système de soins public indien, cet article insiste sur les difficultés de l’analyse des paysages sanitaires contemporains et présente les avantages d’une approche centrée sur l’étude des « instruments de l’action publique » (Lascoumes P., Le Galès P., 2005) et de leurs spatialités. Ces réflexions sont développées à partir de l’étude du rôle des Organisations Non Gouvernementales (ONG) dans les transformations du système de soins public. Une méthodologie est présentée et appliquée à l’étude de quatre ONG.
Traversée des Balkans, troisième partie
Authors: Bacon Lucie
Published: May 2016

Résumé Feuilleton-carte
« Dans l’horrible situation où nous sommes, faire entendre la voix de la vérité »
Authors: Wahnich Sophie
Published: May 2016

Résumé Sagesses révolutionnaires
Justicia «excepcional» y lógicas de radicalización durante la primera pacificación de Venezuela (1812-1814)
Authors: Hébrard Véronique
Published: May 2016

Tras el análisis de la política de Pacificación impulsada por el general Domingo de Monteverde en la Capitanía de Venezuela, entre 1812 y 1814, este articulo se propone estudiar los mecanismos a través de los cuales fue implantada una justicia que se puede considerar como «excepcional», así como sus violentos efectos en el marco de una sociedad signada por la guerra civil. A partir del examen privilegiado de fuentes judiciales el objetivo consiste en reconstruir la organización de esa justicia de «pacificación» durante esos años y abordar su disfunción a partir de prácticas arbitrarias ligadas al abuso de poder en un periodo histórico de cambio de régimen y de guerra civil. Lo que permitirá, por último, repensar el proceso de aceleración de las tensiones civiles y de las violencias que esta política judicial generó.
Guerras, libertad y ciudadanía. Los afro-descendientes de Esmeraldas en la independencia
Authors: Morelli Federica
Published: May 2016

El artículo analiza el papel jugado por la crisis del imperio español y de las guerras de independencia hispanoamericanas en la trasformación de las jerarquías raciales y sociales de la época colonial y en la configuración de nuevos derechos de ciudadanía. Estudiando el caso de Esmeraldas, una región de frontera al noroeste de Ecuador, se quiere poner en evidencia los variados mecanismos que los afro-descendientes, tanto esclavos como libres, utilizaron para acceder a la libertad y la ciudadanía durante el derrumbe de la Monarquía. Se trató de estrategias diferentes a las empleadas por los esclavos y libres de color en otras regiones de Hispanoamérica ya que respondieron a dinámicas propias de una región de frontera.
De Prefectos a Mandatarios de la Nación. La violencia en la política peruana (1829-1836)
Authors: Peralta Ruiz Víctor
Published: May 2016

Bajo el primer gobierno del general Agustín Gamarra (1829-1833) se inició en el Perú la remodelación estatal o «dominación contemporánea mediante la administración». Consistió en el traslado al ejercicio estatal del modelo de patronazgo institucional puesto en práctica por Gamarra durante su desempeñó como prefecto del Cuzco. Sin embargo, este sistema administrativo de ideología conservadora sustentado en la oficialidad del ejército, las máximas autoridades departamentales y connotados personajes civiles fue insuficiente para dar estabilidad al país. Dos motivos lo explican: 1) las propias inseguridades del presidente hacia la lealtad de sus colaboradores políticos; 2) el enfrentamiento de Gamarra, primero, con los liberales que controlaban la Convención Nacional y la prensa, segundo, la pugna con el general Andrés de Santa Cruz por liderar la unificación de Perú y Bolivia en un solo Estado, y, tercero, la competencia con el coronel Felipe Santiago Salaverry por personificar la verdadera revolución conservadora «salvadora de la patria».
El deber de enrolarse y el derecho a votar. Reflexiones en torno a la ciudadanía armada y el sufragio en argentina, 1863-1877
Authors: Macías Flavia
Published: May 2016

El presente trabajo reflexiona sobre uno de los temas clave de la historia política decimonónica hispanoamericana: el papel de las fuerzas cívico militares, en particular la Guardia Nacional, en los procesos electorales y sus efectos en la construcción de la ciudadanía política. En particular, se concentra en la Argentina de las décadas de 1860 y 1870 y explora de qué manera las leyes y las instituciones definieron y delimitaron la relación entre el enrolamiento en la Guardia Nacional y el ejercicio del derecho a voto. Para ello se estudian los debates legislativos previos a la puesta en vigencia de la Ley Electoral Nacional de 1863 y los relativos a las reformas electorales de 1873 y 1877, así como los cambios en la legislación electoral y las influencias del pensamiento de Domingo Faustino Sarmiento en los referidos procesos.
«La medida de su existencia». La abolición de las comunidades indígenas y el juicio de amparo en el contexto desamortizador. (Centro de México, 1856-1910)
Authors: Marino Daniela
Published: May 2016

Este trabajo indaga sobre el proceso administrativo y judicial de reparto de la propiedad comunal de la población indígena. Examina las consecuencias de algunas medidas tomadas por estados del centro de México para subsanar escollos legales, así como la actuación de los tribunales. Mediante el análisis de expedientes de juicios de amparo presentados por individuos, grupos y pueblos busca determinar cuáles fueron los roles jugados por la legislación, la jurisprudencia y las prácticas jurídicas de los actores en la transformación de la cultura de la propiedad, y cómo se imbricó este proceso con la construcción del Estado y la ciudadanía.
VINYL AND LINOLEUM FLOORING: HEALTH ISSUES AS PERCEIVED BY LAY PEOPLE AND ARCHITECTS
Authors: Petrović Emina K. , Vale Brenda , Wilson Marc S.
Published: May 2016

Recently more information has emerged on possible adverse health effects associated with some building and furnishing materials, leading to or initiating legislative changes towards their reduction or elimination in many parts of the world. However, more general knowledge of the health risks associated with building and furnishing materials could make a significant contribution to improvements in indoor air quality. A study was set up to evaluate the level of knowledge in the relevant literature and the general population (from New Zealand, United Kingdom and the United States), and New Zealand architectural professionals. The results for vinyl and linoleum are presented, these being two flooring materials very similar in terms of appearance and application, but different in terms of chemical content and possible impact on health. The article indicates significant issues with the level of reported knowledge, with participants from the general population struggling to differentiate between vinyl and linoleum, and professionals reporting more prevalent use of vinyl, which they rate as less healthy.
Navigating the heavy seas of online publishing: Reflections on ten years editorship
Authors: Carpentier Samuel , Dörry Sabine , Lord Sébastien , Matthey Laurent , Nelles Jen , Walther Olivier
Published: May 2016

Articulo – Journal of Urban Research celebrates its 10th anniversary! To celebrate this milestone, the current editors discuss the numerous changes and challenges related to publishing a peer-reviewed online journal. Since 2005, Articulo has progressively become more international, more professional, and more specialized than its initiators ever dreamed it could be. In ten years, the rather confidential publication has progressively become a journal read by 9,000 people every month. Our editors, who used to work side by side, now live 6,000 km apart. In the midst of often tumultuous change, what hasn’t changed is our commitment to the highest quality of publication and our conviction that knowledge – especially if funded by public money – should be universally and freely accessible. Rigorous peer-review and open access are the two principles on which the journal will navigate the often rough seas of online publishing in the future.
The Information Paradox
Authors: Shahtahmasebi Said
Published: May 2016

This paper is based on a 2008 chapter (Shahtahmasebi, 2008) exploring the availability of information for public health policy purposes which argued its ineffectiveness to add insight and inform the process of policy development. Processes are dynamic by nature which politicians and professionals often neglect in addressing public health issues. The Chapter argued that whilst information is a major currency within health systems a lack of understanding of what constitutes information has disguised available data as small change. Since 2008, against a backdrop of reorganisations, restructuring, buzzwords, and coupled with the rapid advancement in technology the issues remain the same but are somewhat more complicated due to the feedback effect of dynamic processes. For example, a curious persistence of various governments with electronic health records has done nothing to address the gap in “information” or incompatibility in the information systems developed and managed by various care agencies. Furthermore, changing information to “intelligence” (e.g. Public Health Intelligence Units) or “observatories” to carry out similar tasks of reporting health outcomes using the same routine data will not solve the problem. This paper proposes a re-evaluation of the author's focus on informatics and suggests a move away from a technological “solution” based approach to a human behaviour-led approach that utilises the full potential of technologies to address important issues. To this end, this paper proposes a conceptual model to improve access, over and above clinical data, to health data.
Situation Understanding for Operational Art in Cyber Operations
Authors: Kuusisto Tuija , Kuusisto Rauno , Roehrig Wolfgang
Published: May 2016

This paper presents a theoretically motivated framework and methodology that has been designed for finding out the emergent phenomena and information needs for planning and decision-making. The approach is based on complexity thinking, system modeling, communication and cognition philosophy, social system theories and content analysis research technique. It provides results with the analysis of quite small sets of information. The paper demonstrates the approach with a case study. The study was performed in an international cyber experiment of the Multinational Capability Development Campaign (MCDC) 2013-2014. The case study shows that the proposed approach is plausible for increasing understanding about complex situations. This is needed in operational art for creating such compositions and resources that enable success in military operations.
ICTs, E-health, and Multidisciplinary Healthcare Teams
Authors: Olaniran Bolanle A.
Published: May 2016

This paper explores the role ICTs play in the multidisciplinary teams (MDTMs) in healthcare settings. The discussion addresses benefits and challenges of ICTs along with implications for MTDMs. For example, clarification between electronic health records (EHRs) and electronic medical records (EMRs) along with their impact on privacy was made. The paper offers certain suggestions on overcoming some of the challenges identified. Retchin's (2008) framework for inter-professional and co-managed care was presented. The framework focuses on how information communication technologies can impact overall patient health care and delivery.
Mobile Healthcare in an Increasingly Connected Developing World
Authors: Yadav Nikhil , Aliasgari Mehrdad , Poellabauer Christian
Published: May 2016

Global health care has become an enormous industry worldwide, where trends such as aging populations, environmental and climate changes, catastrophic events, and the spread and evolution of diseases pose significant challenges. With the rapid growth of information technology (IT), wireless technologies, and mobile services, health care processes are able to increasingly benefit from new technological advances. Specifically, the area of “mobile health” or mHealth, which leverages mobile phone functionality to provide medical and public health services, has become a very promising trend. Wireless and mobile technologies have great potential in improving patient care, reducing costs, streamlining processes, and allowing adherence to regulations. However, the developing world faces numerous challenges in realizing the infrastructure and technical expertise required to adopt secure mHealth solutions and applications. In this paper the authors discuss these challenges and solutions suitable for the developing world, highlighting existing problems and risks in realizing secure mHealth applications and services.
Phase-Selective Hydrothermal Preparation and Upconversion Luminescence of NaYF4:Yb3+,Tm3+
Authors: Pornpatdetaudom Thanataon , Serivalsatit Karn
Published: May 2016

Upconversion luminescence materials have been proved to have a good efficiency on converting low energy light to high energy light. These materials have received considerable attentions for many applications such as bio-labels, sensors, using for developing solar cells and photocatalytic applications under sunlight. Among many inorganic host materials, NaYF4 has been proved to be the best for doping lanthanide ions and have a good upconversion emission due to its low phonon energy, chemical stability, and transparency in the near infrared to ultraviolet range. In this study, NaYF4:Yb3+,Tm3+ upconversion luminescence materials were synthesized by hydrothermal method at temperature of 90 to 200 °C for period between 1 to 24 hours. The synthesized NaYF4:Yb3+,Tm3+ were characterized by X-ray diffraction, scanning electron microscopy, and fluorescence spectroscopy. The hydrothermal temperature and reaction time have strongly influence on phases and upconversion emission of the synthesized NaYF4:Yb3+,Tm3+. At 90 °C for 1 hour of reaction time, the pure cubic phase of NaYF4:Yb3+,Tm3+ was found. After increasing temperature and reaction time, the NaYF4:Yb3+,Tm3+ converted from cubic phase to hexagonal phase. Under excitation of 980 nm diode laser, the hexagonal NaYF4:Yb3+,Tm3+ exhibited the emission wavelength at about 656 nm (3F2 → 3H6), 469, 492, 552 nm (1G4 → 3H6), 537 nm (1D2 → 3H5), 450, 461 nm (1D2 → 3F4), 362 nm (1D2 → 3H6) and 345 nm (1I6 → 3F4). The upconversion emission intensity of the hexagonal NaYF4:Yb3+,Tm3+ was much stronger, compared with that of the cubic NaYF4:Yb3+,Tm3+.
Effect of Solvent and Drug Impregnation Techniques on Total Drug Content in Rifampicin Impregnated Hydroxyapatite for Localized Bone Tuberculosis Treatment
Authors: Suvannapruk Waraporn , Suwanprateeb Jintamai
Published: May 2016

Rifampicin drug was experimentally loaded into 3D printed porous hydroxyapatite using two types of solvents (methanol or N-methyl-2-pyrrolidone) and various solution impregnation techniques aiming to maximize the total drug content in the samples. All vacuum assisted impregnations gave greater rifampicin content in the sample than that of atmospheric immersion. For similar vacuum assisted impregnation technique, the use of methanol could produce greater amount of drug in the sample than using N-methyl-2-pyrrolidone. For each solvent, the loading technique which gave maximum drug content was different. 2_step vacuum loading technique could impregnate the greatest amount of drug in the hydroxyapatite sample when using methanol as a solvent while one step vacuum loading technique with 10 % solution level (1_step_10) gave the greatest amount of the impregnated drug when using N-methyl-2-pyrrolidone as a solvent. These differences were related to the evaporation rate of the solvent and the degree of concentrated drug on the surface of the samples.
Influence of Curing on Calcined Kaolin-Based Geopolymer
Authors: Lertcumfu Narumon , Eitssayeam Sukum , Pengpat Kamonpan , Tunkasiri Tawee , Sweatman Denis Russell , Jaita Pharatree , Rujijanagul Gobwute
Published: May 2016

The object of this work was to use calcined kaolin-based geopolymer as an alternative material to replace ordinary Portland cement (OPCs) by applying geopolymerization processes. Geopolymer slurry was prepared from calcined kaolin and alkali activators, which consisted of 10 M NaOH and Na2SiO3 solution. The fresh slurry was cast into plastic molds and then cured at room temperature for 24 h. Reaction temperatures were measured (for 24 hours after casting). Compressive strength of the geopolymer was tested after curing at room temperature and after microwave heating. The mechanical properties increased with added plaster for microwave curing of 5 min. It is believed that this process can increase the efficiency of the production line for geopolymer.
Preparation, Characterization and Catalytic Performance of ZnO-SBA-15 Catalysts
Authors: Lao-Ubol Supranee , Khunlad Rungsinee , Larpkiattaworn Siriporn , Chen Shih Yuan
Published: May 2016

The series of ZnO-SBA-15 catalysts with 0.9wt% to 8.5wt% ZnO content have been synthesized by solvothermal impregnated of Zn acetate in ethanol on mesoporous silica SBA-15 platelets in order to maximize the methyl ester selectivity in transesterification reaction. The properties of these catalyst were characterized by N2 adsorption-desorption isotherm, NH3 temperature-programmed desorption, SEM, and XRD. The results showed that the ordered mesoporous structure of SBA-15 was remained with specific surface areas above 500 m2/g and a narrow pore size distribution observed with the mean pore size around 60 Å after ZnO modification. The strength of the acid sites and total acid amount of ZnO-SBA-15 catalysts is varied with number of ZnO loadings. The synthesized ZnO-SBA-15 catalyst was tested for catalytic activity in transesterification of crude Jatropha oil. It was found that at 200 °C for 2 h reaction of the ZnO-SBA-15 catalysts with acid capacities of 0.36-1.29 mmol H+/g-catal gave 68-98wt% of FAME yields and 0.4-1.4wt% of FFA yields which are comparable to the pure ZnO.
Synthesis and Sintering of Magnesium Aluminate Spinel Nanopowders Prepared by Precipitation Method using Ammonium Hydrogen Carbonate as a Precipitant
Authors: Saelee Adison , Jiemsirilers Sirithan , Jinawath Supatra , Serivalsatit Karn
Published: May 2016

Magnesium aluminate spinel (MgAl2O4) is widely used in many engineering applications due to its high melting point (2135°C), high mechanical strength, chemical inertness, and good optical properties. Precipitation method is recognized as a convenient and cost-effective method for the synthesis of nanopowders. In this present work, MgAl2O4 nanopowders were prepared by precipitation method using ammonium hydrogen carbonate as a precipitant. The precipitated precursors were a mixture of ammonium dawsonite (NH4Al (OH)2CO3·H2O) and hydrotalcite (Mg6Al2(CO3)(OH)16·4H2O). After calcining at 1100°C for 2 hours, The MgAl2O4 nanopowders with particle size of 20-170 nm were obtained. The sinterability of the MgAl2O4 nanopowders was evaluated by sintering compacts of the MgAl2O4 nanopowders at temperature of 1300-1650°C for 2 hours. The relative density of the sintered MgAl2O4 ceramics reached about >97% of theoretical density after sintering at 1500°C for 2 hours. The Vicker’s hardness of the sintered ceramics reached a value of 1414 HV (13.9 GPa) after sintering at 1650°C for 2 hours.
Synthesis and Investigation of MoO3 Microfilms and Nanorods by Thermal Chemical Vapor Deposition
Authors: Chaiyo Pitchanunt , Kanlayavisut Ladarat , Vongwatthaporn Rinnatha , Min Bok Ki , Kim Seong Jun , An Ki Seok , Sumran Supon , Pukird Supakorn
Published: May 2016

MoO3 microfilms and nanorods can be synthesized by using the powder of MoS2 as starting materials by thermal chemical vapor deposition. The prepared products on substrates were investigated by field emission scanning electron microscope (FESEM), X-ray photoemission spectroscopy (XPS) and Raman spectroscopy. FESEM images showed the uniformly microfilms and nanorods-like with diameter around 50-100 nm and length of about through 5 μm, respectively. XPS patterns and Raman shifts revealed the prepared products consisting of MoO3 structure phases.
Effect of SnCl4 Concentration on Transparent and Conducting Undoped Tin Oxide Thin Films
Authors: Khlayboonme S. Tipawan , Thanomngam Pitiporn , Thowladda Warawoot
Published: May 2016

The purpose-built pyrolysis system based on an ultrasonically generated aerosol has been successfully used for deposition of highly transparent and conductive undoped tin (IV) oxide thin films. The morphological, structural, optical and electrical properties as well as electronic structures of the films for different concentrations of SnCl4.5H2O used as the starting precursor were investigated. FE-SEM displayed the substrate surfaces were uniformly covered with the film. The film thickness varied with the precursor concentration. XRD patterns showed the deposited films were a tetragonal phase and presented random orientations. The optical transmission spectra of all films revealed highly transmittance in the visible region. Refractive index of the films was between 1.85 and 2.0. XPS spectra for the Sn 3d5/2 and Sn 3d3/2 confirmed that the films were composed of SnO and SnO2 phases. The non-stoichiometric composition decreased with increasing concentration of the precursor. The films deposited with 0.30 M showed the highest conductivity and carrier concentration of 17 W-1cm-1 and 9.5 x 1019 cm-3, respectively. The disagreement of relation between XPS and Hall measurement suggested the higher carrier concentration arose from incorporation of residual chlorine from the solution precursor during deposition into the films. The interstitially incorporated chlorine considerably influenced the electrical properties of the films.
Mechanical Behavior of Fired-Clay Bricks from Stream Sediments under Uniaxial Compressive Loading
Authors: Trakoolngam Kritika , Promkotra Sarunya
Published: May 2016

In the northeast of Thailand, raw material for fired-clay brick is obtained from fine stream sediments in the lower Nam Phong and upper Chi River sub-watersheds. Hundreds of brickyards exist along the waterway producing rice husk ash (RHA) bricks for construction. Technical study on the production of these bricks is limited, therefore, detailed studies on mechanical and chemical properties will enhance the understanding of the production process in order for further improvement. In this study, a preliminary investigation of the brickyards and production process was conducted. Brick samples as well as raw sediment materials were collected from 6 randomly selected locations for laboratory testing on physical, chemical, and mechanical properties. A total of 300 brick specimens were collected being 50 specimens from each location. The brick dimensions are roughly 5×5×15 cm with an average weight of about 680 g. X-Ray Diffractometry show that the fired brick composition is approximately 90-98% quartz, 5-7% clay minerals, and less than 1% minor minerals. Mechanical behavior of the fired-clay bricks was evaluated by compressive loading of single brick units conducted under dry and submerged (with reverse osmosis water) conditions. The compressive strength of the brick unit is found to be proportional to its density with values in the range of about 0.4-1.2 MPa. Bricks with RHA to sediment ratio of 1:3 exhibit a higher average strength that that of other ratios.
Development of Decorative Ceramic Glaze from Palm Fiber Ash
Authors: bin Muhamad Nor Mohd Al Amin , Hazwani Ya’acob Nur Hawa
Published: May 2016

Palm fiber ashes are the industrial waste which is abundantly available in Malaysia. In this study, palm fiber ash were used to produce decorative ceramic glaze. The content of minerals in the palm fiber ash were analyzed by using X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF), respectively. The formulations of glaze with different composition of raw materials were studied by adding different amount of calcium carbonate and feldspar. The glaze slurries then coated on ball clay body bisque which was obtained from Kg. Dengir and sintered at 1200 ° C for two hours.The glaze was characterized in term of its physical appearance such as type of glaze and colour. Both glossy and matte glaze produced by using different composition of glaze formulation. The presence of silica minerals (79 %) contributed to glossy surface to the glaze. It is clearly seen that the glossiness of glaze improved by increasing amount of feldspar. Feldspar acts as fluxing agent which form a glassy phase at lower temperature. In addition, the presence of small amount of iron oxide (2.2 wt.%) contributed to brown colour of glaze. An addition of calcium carbonate give effect to the colour of glaze, which change from brown to yellow colour as amount of CaCO3 increased. As a conclusion, the palm fibre ashes were highly suitable to supply abundant and cheap raw materials to produce decorative ceramic glaze.
Modified Composition of Low Temperature Sintering Alumina Crucible for Glass Melting
Authors: Jampeerung Parida , Meechoowas Ekarat , Thammaprecha Pimpisa , Tapasa Kanit , Jitwatcharakomol Tepiwan
Published: May 2016

The low temperature sintering alumina crucible were prepared with four different formulas by modified the original formula with sintering aids CaCO3, MgCO3, Ball clay and ZrO2. The admixtures were mixed and grinded by ball mill for 24 hrs. The slurry alumina was casted in plaster mold for test samples and crucibles. After dried, the alumina was sintered at 1450, 1500 and 1550°C for 2 hrs. The sintering crucible was investigated chemical composition and properties. The crucibles were tested by melting glass at 1500°C. As a result, the composition (% by weight) was 85-94% Al2O3 2-3% SiO2 1.7-6.5% ZrO2 1.4-3.5% CaO and 0.3-1% MgO with the phase of aluminum oxide (Al2O3), spinel (MgAl2O4) and baddeleyite (ZrO2). The alumina crucible sintered at 1550°C have 9-12 % firing shrinkage density 3.35-3.64 g/cm3 and the coefficient of thermal expansion at 7.72-8.17 ´ 10-6 K-1 which depended on the composition that was similar to commercial 94% alumina (sintered at 1700°C). After tested for the melting glass, these crucibles had high thermal shock resistance which could move out of furnace without any cracks. The selected formula could be used for crucible production with lower sintering temperature, even it decreased sintering temperature from 1700°C to 1550°C. This would save 15-20% of the energy consumption.
Study of Melting Ability of Granulated Glass Batch
Authors: Tapasa Kanit , Meechoowas Ekarat , Thepbutdee Suwannee , Montreeuppathumb Amorntep
Published: May 2016

In the conventional soda-lime glass production, loose raw materials are normally mixed into a glass batch for melting. Dusting and segregation of the loose glass batch are always occurred during the melting process inside the glass furnace. Also, the loose glass batch has low thermal conductivity which limits the glass melting ability and pulling rate of the glass furnace. Granulation and preheating of glass raw materials have been proposed to solve the problems. In this study, the granulated soda-lime glass batch (SiO2 50% Na2CO3 22.5% CaCO3 12% NaAlSi3O8 9.5% BaCO3 2.5% ZnO 1.75% Sb2O3 1% and K2CO3 0.75% by weight) was prepared to study the melting ability in an electric furnace. The granulated batch was also preheated at 500-600°C before melting. The preheating temperature was matched to the temperature of flue gas at the bottom of the stack in the glass furnace. The purpose behind this was aiming to recover the waste heat from the furnace. The experiment exhibited the increased melting ability for the granulated-preheated glass batch
The Fabrication and Dielectric Constant of (1-3) Piezoceramic Polymer Composites
Authors: Tontrakoon Jerapong , Rujijanagul Gobwute , Pengpat Kamonpan , Eitssayeam Sukum , Intatha Uraiwan , Sanjoom Ratabongkot , Tunkasiri Tawee
Published: May 2016

Piezoceramic-polymer composites having (1-3) type connectivity and of a scale size suitable for high frequency >1 MHz transducers was carried out in this study. The piezoceramics (PbZr0.52Ti0.48O3, PZT) were prepared by the conventional mixed oxide route. The starting powders of PbO, ZrO2 and TiO2 were mixed and calcined at 800oC. The calcined powder was mixed with excess PbO and a lithium/bismuth-based glass forming in order to lower the sintering temperature to approximately 1000oC. A method for extruding rods of approximately 400 m diameter was developed. The fast firing process was carried out to sinter the PZT rods. Then the rods were assembled and impregnated with epoxy resin to form 1-3 composites containing approximately 20 and 50 vol% piezoceramics. Both PZT rods and the composites were studied by a scanning electron microscope (SEM). The dielectric properties of the composites were measured. The equivalent capacitance model was employed to determine the dielectric for comparison.
Phase Structure, Microstructure and Electrical Properties of BCZT Ceramics Prepared by Seed-Induced Method
Authors: Hirunsit Wasuporn , Parjansri Piewpan , Intatha Uraiwan , Eitssayeam Sukum , Tunkasiri Tawee
Published: May 2016

The effect of particle sizes of CaZrO3 (CZ) nanocrystal on the phase structure, microstructure and electrical properties of Ba0.85Ca0.15Zr0.10Ti0.90O3 (BCZT) was studied. The CaCO3 and ZrO2 were used as starting materials for CaZrO3 (CZ) seeds synthesized by the molten-salt method. The results were found that the CZ powder has a pure perovskite with the particle size about 370 to 460 nm. Then the CZ nanocrystals were mixed with the metal oxides BaCO3, CaCO3, ZrO2 and TiO2 by mixed oxide method. The phase structure, microstructure and electrical properties of BCZT ceramic were investigated as a function of particle size and concentration of CZ. The results indicated that all samples showed pure perovskite phase. The highest values of density, grain size, dielectric constant (εr) and piezoelectric coefficient (d33) were 5.50 g/cm3, 10.95 μm, 2992 and 446 pC/N, respectively which obtained at the CZ seed size 459 nm.
The Effect of Glass/PVA Composite Composition on the Adhesion and Strength of a 96% Alumina Joint
Authors: Somton Kritkaew , Rodchom Mana , Wonglom Thassanee , Laoratanakul Pitak , McCuiston Ryan C.
Published: May 2016

This research studied the effect of composition of a glass-based high temperature adhesive on the bond strength of 96% alumina bars. The adhesives studied were composed of 40-70% glass powder, 5-30% polyvinyl alcohol (PVA), and 15-55% water. Half-lengths of green alumina bend bars were bonded together with the adhesive to form a full length bar and then sintered. The flexural strengths of the sintered bars were measured and the resultant fracture surfaces were examined by SEM. The results showed that an initial increase in the PVA and glass content increased the flexural strength to the highest value of 120 MPa, but that further increases resulted in decreased strength. The strength values fluctuated when the PVA content was above 20% and the glass content was 40% or 60%, which indicated poor adhesive homogeneity. SEM analysis of the fracture surfaces showed a separation layer between the alumina and glass adhesive when the glass or PVA content were either too high or too low, which again indicated poor adhesive homogeneity. It was concluded that the optimal composition of the adhesive was 45-55% glass and 7-15% PVA, which gave a minimum flexural strength of 80 MPa.
Conversion of Aluminum Dross Residue into Value-Added Ceramics
Authors: Sooksaen Pat , Puathawee Pathompong
Published: May 2016

This study utilized aluminum dross residue obtained from secondary process of aluminum production as the main component in the fabrication of ceramic refractories. The amount of residue varied in the range 60-90 wt% and other components in the ceramic formulations were a combination of alumino-silicate based clays. Alpha-alumina, a-Al2O3 was the main crystalline phase found in all sintered samples according to x-ray diffraction analysis. Mullite phase, Al6Si2O13 was also found in all the sintered refractories. It appeared as the main second phase which gave high strength and refractoriness. All the synthesized refractories had excellent heat-resistant characteristics when tested for thermal shock resistance. Samples were heated at 1200°C and subsequently quenched to cold water and ambient air. Refractories produced from aluminum dross residue in this study are advantageous for various applications such as high alumina bricks, high duty firebricks for steel and glass melting industry.
Powder Injection Molding of Mullite: The Study of Binder Dissolution Behavior during Debinding Step Using Statistical Methods
Authors: Chakartnarodom Parinya , Kongkajun Nuntaporn , Chuankrerkkul Nutthita
Published: May 2016

The purpose of this work is to use the statistical methods including linear regression and statistical hypothesis test to study the dissolution behavior of polyethylene glycol (PEG), a water-soluble binder, during debinding step of the green specimens of mullite formed by powder injection molding (PIM). Two systems of composite binders were investigated including (A) 80 wt% polyethylene glycol (PEG) and 20 wt% polyvinyl butyral (PVB) and (B) 78 wt% PEG, 20 wt% PVB, and 2 wt% steric acid (SA)The lab-scale plunger type PIM machine was used to prepare the green specimens consisting of mullite powder and the composite binder. The possible solid loadings of the green specimens that could be prepared by this machine were 50, 52, and 54 vol% mullite (50, 48, and 46 vol% binder). The debinding was done by soaking the green specimens in the warm water at 40 or 60 oC to remove PEG. At level of significance 0.05 for statistical analysis, the dissolution behavior of PEG can be fitted with Avarami equation. In addition, from the Avarami equation obtained from each experimental condition, the dissolution rate of PEG was independent of the parameters used in this study including solid loading in the green specimens, water temperatures for debinding, and composite binder systems.