bluuebunny/crossref_metadata_2025 huggingface dataset:
The value of hyperbilirubinaemia in the diagnosis of acute appendicitis
Authors: Emmanuel Andrew , Murchan Peter , Wilson Ian , Balfe Paul
Published: April 2011

INTRODUCTION

No reliably specific marker for acute appendicitis has been identified. Although recent studies have shown hyperbilirubinaemia to be a useful predictor of appendiceal perforation, they did not focus on the value of bilirubin as a marker for acute appendicitis. The aim of this study was to determine the value of hyperbilirubinaemia as a marker for acute appendicitis.

MATERIALS AND METHODS

A retrospective analysis of appendicectomies performed in two hospitals (n=472). Data collected included laboratory and histological results. Patients were grouped according to histology findings and comparisons were made between the groups.

RESULTS

The mean bilirubin levels were higher for patients with simple appendicitis compared to those with a non-inflamed appendix (p<0.001). More patients with simple appendicitis had hyperbilirubinaemia on admission (30% vs 12%) and the odds of these patients having appendicitis were over three times higher (odds ratio: 3.25, p<0.001). Hyperbilirubinaemia had a specificity of 88% and a positive predictive value of 91% for acute appendicitis. Patients with appendicitis who had a perforated or gangrenous appendix had higher mean bilirubin levels (p=0.01) and were more likely to have hyperbilirubinaemia (p<0.001). The specificity of hyperbilirubinaemia for perforation or gangrene was 70%. The specificities of white cell count and C-reactive protein were less than hyperbilirubinaemia for simple appendicitis (60% and 72%) and perforated or gangrenous appendicitis (19% and 36%).

CONCLUSIONS

Hyperbilirubinaemia is a valuable marker for acute appendicitis. Patients with hyperbilirubinaemia are also more likely to have appendiceal perforation or gangrene. Bilirubin should be included in the assessment of patients with suspected appendicitis.
Solubility phenomena involving CaSO4 in hydrometallurgical processes concerning heavy metals
Authors: Zeng Dewen , Wang Wenlei
Published: April 2011

Deposit of CaSO4 in hydrometallurgical processes involving heavy metals usually decreases production quality and harms the production process. To avoid its formation at false time and sites, a sound understanding of the solubility behavior of CaSO4 in the quaternary systems CaSO4 + H2SO4 + (heavy metal)SO4 + H2O over large ranges of temperature and concentration is a prerequisite. Up to now, although a large amount of solubility data has been reported in these systems, little information is available on the solubility of anhydrite, especially at salt concentrations near saturation points. In this paper, we introduce the effect of CaSO4 in hydrometallurgical processes involving heavy metals, review published solubility data of calcium sulfate and its hydrate in relevant systems, and report our newly determined solubility results involving anhydrite in the quaternary systems CaSO4 + H2SO4 + MSO4 + H2O (M = Cu,Zn,Mn) at 348.1 and 363.1 K. Based on the newly obtained data some application examples were given. On account of the complexity of the solubility phase diagram of these quaternary systems, where the calcium sulfate solubility is a function of its crystal type, temperature, compositions of sulfuric acid, and heavy metal sulfate, a complete solubility phase diagram is not available until some basic data measurement, for instance, water activity at temperatures higher than 298 K, and final modeling has been finished.
Does glycosyl transfer involve an oxacarbenium intermediate? Computational simulation of the lifetime of the methoxymethyl cation in water
Authors: Williams Ian H. , Ruiz Pernía J. Javier , Tuñón Iñaki
Published: April 2011

2D free-energy surfaces for transfer of the methoxymethyl cation between two water molecules are constructed from molecular dynamics (MD) simulations in which these atoms are treated quantum-mechanically within a box of 1030 classical solvent water molecules at 300 K. This provides a simple model for glycosyl transfer in water. The AM1/TIP3P surfaces with 2D-spline corrections at either MPWB1K/6-31+G(d,p) or MP2/6-31+G(d,p) contain a shallow free-energy well corresponding to an oxacarbenium ion intermediate in a DN*AN mechanism. MD analysis at three temperatures leads to a classical estimate of the lifetime of the methoxymethyl cation in water; when quantum corrections for vibrational zero-point energy are included, the lifetime is estimated to be about 1 ps, in agreement with the best experimental estimate. This suggests that computational simulation, with appropriate high-level correction, is a reliable tool to obtain detailed and reliable mechanistic descriptions for glycosidases. In view of the importance of developing improved anti-influenza drugs, simulations of sialidases that considered both sialyl oxacarbenium ion and covalent sialyl-enzyme as possible intermediates could provide particular insight.
Supersaturation and solute enrichment and their role in phase transformations in metal alloys
Authors: Rettenmayr Markus
Published: April 2011

Supersaturations and depletion or enrichment of solute/solvent are known to be the driving forces for phase transformations. In the present work, a series of different experiments is presented where in a single phase or a two-phase mixture supersaturation or enrichment/depletion of solute occur in at least one of the phases. In all cases the result is a phase transformation, particularly either the precipitation of a secondary phase out of a primary phase, or the migration of the interface in a two-phase mixture. It is demonstrated that solute transport in the phase exhibiting faster kinetics controls the phase transformation process.
Superelectrophilic chemistry in the gas phase
Authors: Roithová Jana
Published: April 2011

Superelectrophilic chemistry in the gas phase is driven by the high intrinsic reactivity of dications. The formation of new doubly charged products proceeds via highly internally excited intermediates. Conditions for the formation of the doubly charged intermediates and a “cooling principle” in the reactivity of dications are explained. The reactivity is demonstrated with several examples.
Computational thermodynamics: A mature scientific tool for industry and academia
Authors: Hack Klaus
Published: April 2011

The paper gives an overview of the general theoretical background of computational thermochemistry as well as recent developments in the field, showing special application cases for real world problems. The established way of applying computational thermodynamics is the use of so-called integrated thermodynamic databank systems (ITDS). A short overview of the capabilities of such an ITDS is given using FactSage as an example. However, there are many more applications that go beyond the closed approach of an ITDS. With advanced algorithms it is possible to include explicit reaction kinetics as an additional constraint into the method of complex equilibrium calculations. Furthermore, a method of interlinking a small number of local equilibria with a system of materials and energy streams has been developed which permits a thermodynamically based approach to process modeling which has proven superior to detailed high-resolution computational fluid dynamic models in several cases. Examples for such highly developed applications of computational thermodynamics will be given. The production of metallurgical grade silicon from silica and carbon will be used to demonstrate the application of several calculation methods up to a full process model.
Chemistry of salts in aqueous solutions: Applications, experiments, and theory
Authors: Voigt Wolfgang
Published: April 2011

Salts comprise a very large and important group of chemical compounds. Natural occurrence of salts and industrial processes of their recovery, conversion, purification, and use depend on solubility phenomena and their chemistry in aqueous solutions, mostly in multi-ion systems. Modeling of these processes as well as developing new ones requires knowledge of the properties of the aqueous salt solutions in extended T-p-x ranges including a growing number of components in solutions (CO2, SO2, lithium salts, salts of rare earth metals, actinides, etc.). At least for the thermodynamic properties, the general accepted methodology is to use thermodynamic databases of aqueous species and solids in combination with an appropriate ion-interaction model to perform equilibrium calculations for species distributions in solution and phase equilibria. The situation in respect to available thermodynamic models and data for their parameterization is discussed at selected examples. Thereby, the importance of accurate experimental determinations of phase equilibrium data for derivation of model parameters is emphasized. Furthermore, it is concluded that experimental investigations should follow a chemical systematic. Simple physical models or quantum chemical calculations cannot predict unknown quantities in the databases with sufficient accuracy. Finally, solubility changes in salt-water systems at enhanced temperatures are considered. Systems, which can be considered as molten hydrates, display interesting phase behavior and chemical reactivity as protic ionic liquids. The latter can be exploited in chemical syntheses to substitute mixtures of concentrated acids like HNO3/H2SO4 by simple salts like ferric nitrate. For an understanding of the chemical and phase behavior of water-salt systems in terms of structure–property relations, a renaissance of chemical guided basic investigations of such systems would be worthwhile.
The Importance of the Dhammathats in Burmese Law and Culture
Authors: Huxley Andrew
Published: April 2011

Burma's dhammathats are pre-colonial compilations of legal and ethical material. They provide vivid insights into the details of everyday village life and into the process by which Burmese authors adapted Pali texts from India to their own purposes. They appear to be at least as old as any other surviving Burmese literature and contain valuable lessons for contemporary Burma. This article hopes to rescue them from their unjust neglect.
Comparison of Three Pottery Villages in Shan State, Burma
Authors: Reith Charlotte
Published: April 2011

During my visit from 1991-1994 to three pottery-producing villages in Shan State, I was struck by the differences in technology and product. Contrary to my assumption that this small area would evidence a shared technology and similar products, I found three distinctly differing pottery traditions. In some places in the world, membership in the same ethic group seems to be an important factor in determining the techniques and products of the potters belonging to that group. However, two of these villages, Compani and Awe Yaw, are both populated by Danu and have distinctly different ways of making pots. While it is primarily concerned with the pottery-making processes in the three villages, this article is also interested in the lives of the potters and how they face the challenges inherent in their craft.
Half a Century of Publishing in Mandalay: The Ludu Kyi-bwa-yay Press
Authors: Allott Anna
Published: April 2011

The Ludu Kyi-bwa-yay Press was established in Mandalay as a radical left-wing publishing house by Ludu U Hla and his wife, Daw Amar, in 1938. Ludu U Hla was a pioneering Burmese journalist, would-be social reformer, social historian, and, most of all, recorder of folk-tales. Daw Amar began her writing career in 1938 as a translator, mostly of anti-Western works; in 1964 she began a series of major works dealing with Burmese traditional performing arts and the history and culture of Upper Burma and of Mandalay. U Hla died in 1982, and in March 1984 much of the press was destroyed in the great Mandalay fire. Nevertheless, the press resumed publishing in 1987 under the direction of Daw Amar and despite continued strict government censorship has remained in operation until the present. The latest book in Ludu U Hla's folktale series appeared posthumously in 1996. This article is followed by a translation of a short biography of Ludu U Hla written by Daw Amar.
Rise of a Mainland Trading State: Rahkaing Under the Early Mrauk-U Kings, c. 1430-1603
Authors: Charney Michael W.
Published: April 2011

This study of the rise of the maritime kingdom of Rahkaing (Arakan) in the 15th and 16th centuries attempts to demonstrate how the kings of Danya-wati gradually drew other power centers in the Rahkaing littoral (including Mekha-wati, Dwara-wati, and Chittagong) into its political orbit. Vital to this political centralization were the collateral processes of increasing maritime trade, demographic growth spurred by resettled war captives, the suppression of rival lowland tribes, supplies of firearms, and the development of a multi-directional system of religious patronage. By the end of the 16th century, Mrauk-U rulers, as both Buddhist kings and Islamic sultans, controlled the entire Rahkaing littoral as one kingdom and had begun their expansion into neighboring regions as distant as Dacca in Bengal and Pegu in Burma.
Languages in Contact: The Case of English and Burmese
Authors: Wheatley Julian , Hnin Tun San San
Published: April 2011

This article deals with the nature and the effects of the long period of linguistic contact between Burmese and English. Part 1 deals with general issues of contact and borrowing; part 2 provides examples of English loanwords in Burmese, and considers the processes of phonological and semantic accommodation that they reflect.
The North Wind and the Sun: Japan's Response To The Political Crisis in Burma, 1988-1998
Authors: Seekins Donald M.
Published: April 2011

Japan's response to the political crisis in Burma after the establishment of the State Law and Order Restoration Council (SLORC) in September 1988 reflected the interests of powerful constituencies within the Japanese political system, especially business interests, to which were added other constituencies such as domestic supporters of Daw Aung San Suu Kyi's struggle for democracy and those who wished to pursue 'Sun Diplomacy,' using positive incentives to encourage democratization and economic reform. Policymakers in Tokyo, however, approached the Burma crisis seeking to take minimal risks—a "maximin strategy"—which limited their effectiveness in influencing the junta. This was evident in the February 1989 "normalization" of Tokyo's ties with SLORC. During 1989-1998, Japanese business leaders pushed hard to promote economic engagement, but "Sun Diplomacy" made little progress in the face of the junta's increasing repression of the democratic opposition.
The Concepts of Dobama ("Our Burma") and Thudo-Bama ("Their Burma") in Burmese Nationalism, 1930-1948
Authors: Nemoto Kei
Published: April 2011

This article attempts to demonstrate the interdependent operation of the term dobama ("our Burma") and its opposite, thudo-bama ("their Burma"), in the minds of members of the Dobama-asiayoun ("Our Burma Party"). From the party's very beginning in 1930 to the Anti-Fascist People's Freedom League's struggle against Japanese rule and subsequently for independence from the British from 1944 to 1947, Dobama party members, known as "thahkins," avoided being identified as thudo-bama , meaning "the Burmese of their (the British or Japanese) side" or "the Burmese people who collaborated with the colonial regime." Instead, they invariably identified themselves as dobama , or "our Burmese." The thahkins preferred to define themselves in negative rather than positive terms. In other words, they chose to identify themselves by describing what they were not rather than what they were, and by attacking their imagined enemies, the thudo-bama , rather than attempting a clear definition of dobama .
The VOC in Burma: 1634 — 1680
Authors: Dijk Wil O.
Published: April 2011

This article is intended to show that the archives of the Dutch East India Company (VOC) at the General State Archives (ARA), The Hague, The Netherlands, are a rich source of information on seventeenth century Burma. Because this unearthed data is mostly about commerce, this paper deals with the VOC s trade with Burma. What has come to light is that the Dutch factories in Burma were an important and integral part of the VOC s network of trade, seeing that the profits helped to fund the purchase of Indian textiles that were the backbone of much of the Dutch inter-Asian trade. The Dutch, moreover, sold Burmese export products profitably from Persia to Japan and Holland. In the end, the VOC s establishment in Burma became the victim of a general change in Dutch fortunes when forces in both Europe and the Far East began working against the Dutch East India Company.
Adoniram Judson and the Creation of a Missionary Discourse in Pre-Colonial Burma
Authors: James Helen
Published: April 2011

In the following paper I argue that Adoniram Judson, the first American Baptist Missionary to Burma, was strongly empathetic with his adopted country. His work as interpreter-translator during the negotiations leading to the Treaty of Yandabo in 1826 and his visits to Ava both immediately before and after the First Anglo-Burmese War (1824-1826), although couched in the language of Christian mission, exhibited characteristics markedly different from the perspective of Ann Judson's memoir, and from those of certain missionary narratives subsequent to his own. I propose to examine aspects of three texts: Ann Judson's An Account of the American Baptist Mission to the Burman Empire ; Henry Gouger's Personal Narrative of Two Years Imprisonment in Burmah ; and Adoniram Judson's deposition to John Crawfurd. I shall also refer to J. Snodgrass' Narrative of the Burmese War (1824-1826) and Henry Trant's Two Years in Ava for other perspectives on some events.
"Making a Name for Themselves:" Karen Identity and the Politicization of Ethnicity in Burma
Authors: Harriden Jessica
Published: April 2011

The history of Karen nationalism has been interpreted in terms of inter-ethnic conflict and conceptualizations of ethnicity have influenced understanding of Karen political identity. While 'Karen' incorporated various linguistic, sociocultural, religious and political sub-groups, the Karen National Union (KNU) elite promoted a singular pan-Karen identity in order to minimize such diversity. As a result, factionalism emerged between different Karen groups, obstructing the KNU's political vision and leaving many Karens dissatisfied with KNU attempts to represent their various interests. The fall of Manerplaw in 1995 was thus the result of intra-ethnic conflict as much as conflict between Karens and non-Karens.
Modern Burmese Painting According to Bagyi Aung Soe
Authors: Ker Yin
Published: April 2011

Rangoon-based artist Bagyi Aung Soe (1924-1990) has been regarded by fellow artists as a pioneer of modern art in Burma. Influenced by precepts practiced at Rabindranath Tagore's Śāntiniketan, he elaborated an original painting approach and style synthesizing diverse artistic approaches, which neither adhered exclusively to the European or Burmese artistic tradition nor regurgitated twentieth-century Western artistic innovations. Despite his renown within Burma, his idiom remains little understood both within and beyond Burma because of a lack of awareness of his motivations and their context. This article attempts to elucidate Bagyi Aung Soe's interpretation of modernity in Burmese painting, and with reference to his works and writings, examine the modernity of his art.
A Norm of Burmese Kingship?: The Concept of Raza-dhamma through Five Konbaung Period Texts
Authors: Candier Aurore
Published: April 2011

The Burmese concept of raza-dhamma, which derives from the Pali rāja dhamma found in early Buddhist literature, refers to a tenfold code for righteous kings. In the early eighteenth century, U Kala's Maha-raza-win-kyi connected the raza-dhamma to the origin myth of Mahathammata and laid the groundwork for later texts. While scholars thus far have limited their perspectives to the early Konbaung sources, this article attempts a more systematic approach tracing the evolution of a commentarial genre that broadened the scope of the concept. Throughout the middle and late Konbaung period, the interpretation of the ten raza-dhamma represents the first argument of a constantly redefined discourse on kingship. A historical and linguistic investigation of five significant texts shows how this concept participated in the gradual changes of the sociopolitical representations during three periods. From Bagyidaw's reign (1820s-1830s), this article analyzes the royal chronicle Hman-hnan maha-raza-win-daw-kyi and two normative texts, the Monywe hsayadaw's Razaw-wada-kyan and the Maha-dhamma-thinkyan's Dhammaw-padetha-kyan, all three written between 1827 and 1832. Next, it investigates the concept in Mindon's early reign (1850s-1860s) through the third Maung Htaung hsayadaw's Raza-thewaka-dipani-kyan (1856), which enlarged upon the Dhammaw-padetha-kyan. Finally, turning to the late Konbaung period (end of the 1870s-1890s), this article look at the concept in Hpo Hlaing's Raza-dhamma-thingaha-kyan (1878).
'Bodawpaya's Madness': Monastic Accounts of King Bodawpaya's Conflict with the Burmese Sangha, Part One
Authors: Pranke Patrick
Published: April 2011

In the early nineteenth century, a conflict between the Burmese king, Bodawpaya (r. 1782-1819) and his council of monastic leaders led to the temporary persecution and suppression of the Burmese sangha. Historical research into t he affair has relied for the most part on early European reports and more recently on Bodawpaya's own royal orders to come to an understanding of the motives and objectives of the king's actions. This article takes a somewhat different approach by exploring the incident as it was seen through the eyes of the monastic community. Citing both contemporary sources and later nineteenth- and twentieth-century historical retrospectives, this article discusses the issues deemed important by the sangha in terms of its perceived legitimacy, its role in the world as an agent of salvation, and its prerogatives as an institution vis-à-vis the Buddhist state. This information, important in its own right, also helps to clarify the motives that informed the king's behavior, as well as allows a more critical assessment of western accounts of the controversy. The apologetics presented in the monastic narratives are technical and imbedded in a conceptual universe that merges the religious, the cosmological and the political, and as such require a familiarity with Theravāda scholasticism and the Burmese Buddhist world view to be understood. Implicitly, this article argues for the utility of such kinds of Buddhist cultural literacy in the study of Burmese religious history and in Burma studies more generally.
Legal Education in Burma since the mid-1960s
Authors: Zan Myint
Published: April 2011

This article reports on and analyzes developments in Burmese legal education since the mid-1960s. Among others it analyzes the method of admission to various law courses, an overview of and commentary on the course syllabi and the teaching methods and delivery of legal education. The article examines the correspondence courses or distance legal education courses offered since 1975 and the ostensible switch from Burmese to English as a medium of instruction to gauge their effectiveness. The research methodology adopted is based, among others, on the author's own experiences as a law student at Rangoon Arts and Science University. For a more contemporaneous report and analysis, the author also studied the distance education materials prepared for various law courses. He sat in and observed the teaching in both undergraduate (Bachelor of Laws) and post graduate (Master of Laws) classes and conducted interviews with academic staff, undergraduate, and postgraduate students as well recent law graduates and lawyers. The author describes and comments on the course requirements and teaching methods of the postgraduate Master of Laws and Doctor of Philosophy (in law) programs. He also describes and analyzes the format, content, and quality of the seminars for the PhD presentations (regarding the theses), and gives possible suggestions for improvement. From this retrospective of the past four decades of Burmese legal education, the author avers that there are no grounds for optimism as regards future prospects.
Three Nineteenth-Century Law Book Lists: Burmese Legal History from the Inside
Authors: Huxley Andrew
Published: April 2011

Through an investigation of three Burmese law book lists by Maungdaung Sayadaw, Tha Dwe, and Kyaw Htun this article seeks to construct a narrative history of legal traditions. By breaking each list into smaller units and comparing the results a common core of Burmese legal history emerges. The lists, shed light on who the typical authors of a dhammathat were while items that appear on some, but not all, of the lists help indicate controversies that were still matters of live debate during the nineteenth century.
Rockets and Ashes: Pongyibyan as Depicted in Nineteenth- and Twentieth-Century European Sources
Authors: Isaacs Ralph
Published: April 2011

This article describes the Burmese festival of pongyibyan, the ceremonies at the cremation of a senior monk, mainly by collating written accounts and photographs by Europeans who witnessed pongyibyan in the nineteenth and early twentieth centuries. Certain rites of the pongyibyan ceremony offer interesting parallels to accounts of the Buddha's own funeral found in the Mahaparinibbana Sutta. This article cites descriptions of the preparation of the monk's corpse by evisceration, embalming, lacquering, wrapping in cloth, and gilding, including descriptions of both the simple inner coffin and elaborate outer coffin, and the mortuary chapel (neiban-kyaung) where the body lay in state awaiting cremation. The article depicts the architectural and symbolic significance of the tall funeral pyres with figures of mythical beings and the role of the sat-hsaya, the craftsman in bamboo and cut paper who built them as well offering a description of the lonswethi, the tug-of-war for merit. Numerous foreign observers reported the Burmese passion for rocketry. At least three types of rockets (don) were used at pongyibyan for kindling the funeral pyre. Rockets commonly caused injury or death to spectators, and were discouraged by the British colonial government.
Displacement Current Measurement of MIS Devices with Ionic
Liquids to Explore Carrier Behaviors in Model Interfaces of Organic
Devices
Authors: Yamada Taiki , Noguchi Yutaka , Ouchi Yukio , Ishii Hisao
Published: April 2011

Charge injection property of organic thin film devices is a key issue to
understand the device operation. Displacement current measurement (DCM) is a
powerful technique to probe the charge injection behaviors in terms of a
change in the apparent capacitance of test devices. However, it requires to
suppress actual current flowing through the device for investigating the
details of interface phenomena. We propose here the use of ionic liquids
(ILs) as a top contact insulator in organic metal-insulator-semiconductor
(MIS) structures. Because of the high stability and dielectric constant of
the ILs, the external applied voltage was applied mainly to the organic
layer with suppressing the actual current. The DCM curves of Pt
wire/IL/α-NPD/ITO structure were measured, and they actually show the
signals due to the hole injection from theITO to α-NPD layer and
accumulation at the IL/α-NPD.
Electrical Conductance of Single Oligothiophene Molecular Wires:
Temperature Effect
Authors: Lee See Kei , Yamada Ryo , Tanaka Shoji , Tada Hirokazu
Published: April 2011

We investigated temperature dependence of the electrical conductance of
single oligothiophene molecular wires with the length of 2.2 nm (5-mer), 5.6
nm (14-mer) and 6.7 nm (17-mer) by using the scanning tunneling microscopy
break junction method. Results show that the dominant charge carrier
transport for 5-mer molecule is tunneling while for 17-mer molecule is
hopping. The carrier transport mechanism of 14-mer are tunneling transport
(T ≤ 350 K) and hopping transport (T > 350 K) indicating that hopping and
tunnelling transport are competitive process in the molecular junction.
The direct measurement of energy barrier height at metal/
polyfluorene derivatives interface by internal photoemission
spectroscopy
Authors: Itoh Eiji , Takaishi Shinya
Published: April 2011

We have investigated the barrier height for electron injection at the
cathode / polyflu-orene derivatives interface by the internal photoemission
(IPE) spectroscopy techniques using the “electron only device” structure
consisting of TiO2, electron transporting polyimide inter-layer
(IL), and polyfluorene derivatives. We also estimated the barrier height by
the current analysis based on the Schottky thermal emission current model,
and it coincides well to the threshold energy of IPE result only when the
energy is lower than 1.1eV. The measured barrier height obtained by IPE
linearly increases with both the work-function of cathode materials.
However, the slope parameter becomes less than 1 (~0.6) for poly
(9,9-dioctylfluorene) (F8) probably due to the interfacial gap states. On
the other hand, the slope parameter becomes very small (~0.18) for the poly
(9,9-dioctylfluorene)-co- benzo- thiadiazole) (F8BT) probably due to the
electron pinning at the cathode/ acceptor interface.
Twin-domain Epitaxial Growth and Metal-insulator Transition of VO2 Thin Film on C-Plane Sapphire
Authors: Chen Changhong , Zhao Yong , Pan Xuan , Holtz Mark , Fan Zhaoyang
Published: April 2011

We report heteroepitaxial growth of VO2 thin film on c-plane sapphire by pulsed DC magnetron sputtering. X-ray diffraction experiment indicates that the 150 nm thick film is in triple-domain (020)-epitaxial structure with six-fold rotational symmetry in the basal plane; in particular, off-axis Φ scans from (011) and (220) show twin and triple peaks in each group of the diffraction profiles due to angle β mismatch and V4+-V4+ dimerization, respectively. The epitaxial relationship between VO2 and c-plane sapphire can be concluded as be ${\rm{VO}}_{\rm{2}} \left[ {{\rm{010}}} \right]{\rm{ }}\left\| {{\rm{Al}}_{\rm{2}} {\rm{O}}_{\rm{3}} \left[ {{\rm{0001}}} \right]\,{\rm{and}}\,{\rm{VO}}_{\rm{2}} {\rm{ }}\left({{\rm{\bar 202}}} \right){\rm{ }}} \right\|{\rm{Al}}_{\rm{2}} {\rm{O}}_{\rm{3}} \left\{ {11\bar 20} \right\}$, with the in-plane lattice mismatch of 2.66% (tensile) along $\left[ {\bar 202} \right]$ and the out-of-plane lattice mismatch of -2.19% (compressive). Temperature dependence of resistivity in van der Pauw method shows that the resistivity changes by ~5 orders of magnitude through the metal-insulator transition, and a narrow hysteresis window of ~3 K is obtained between cooling and heating cycles with respect to phase-transition temperatures at 347.1 and 350.1 K.
Structural and Ferroelectric Properties of Large c/a Phase Bismuth Ferrite Thin Films Prepared by Ion Beam Sputtering
Authors: Nakashima Seiji , Tsujita Yosuke , Fujisawa Hironori , Park Jung Min , Kanashima Takeshi , Okuyama Masanori , Shimizu Masaru
Published: April 2011

BiFeO3 (BFO) thin films have been deposited on SrRuO3/SrTiO3 (001) substrate by using ion beam sputtering process. At low oxygen partial pressure of 11 m Pa, rhombohedral and large c/a mixed phase thin film have been obtained in spite of rhombohedral BFO single phase formation at high oxygen partial pressure of 73 mPa. From wide area 2θ-Ψ mappings, diffraction peaks from large c/a phase BFO thin film were obtained with the same extinction rule as those of rhombohedral BFO. Reciprocal space mappings around BFO (003) and BFO (103) spots indicate that lattice parameters of large c/a phase BFO were a = 0.381 nm and c = 0.461 nm (c/a =1.22), respectively. Moreover ferroelectric domain switching could be observed in both of rhombohedral BFO and mixed phase BFO thin films.
Oxidative Jet Deposition of Polythiophenes
Authors: Gilpin A. Davison , Boerio F. James
Published: April 2011

An oxidative jet deposition process was used to deposit films of polythiophenes. The oxidative jet is created using two different methods, an ozone jet or a plasma jet. An ozone jet is created by forcing a gas mixture containing oxygen through a corona-discharge apparatus. A plasma jet is created by forcing an ionization gas through a radio-frequency plasma chamber. Polymerization and film deposition was achieved by rastering the jet over a substrate while a monomer was injected into the oxidative jet. The injected monomers include thiophene, 2-methylthiophene, 3-methylthiophene, and 3,4-ethylenedioxythiophene (EDOT). The resulting films were studied with Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and time-of-flight secondary ion mass spectrometry (TOF-SIMS). FTIR spectra of the jet deposited films were characteristic of undoped poly(3,4-ethylenedioxythiophene) PEDOT. FTIR spectra showed that parameter optimized plasma jet deposited films contained less overoxidation in the form of hydroxyl and carbonyl groups than films deposited through the ozone jet process. The fabrication of organic electronics could be improved by this technology because a jet process allows for inline processing. Inline processing offers practical industrial advantages over the batch process methods currently used for depositing films of polythiophenes.
Quasi-pyramidal texturing using phase-segregated masks
Authors: Saenger Katherine L. , Carruthers Roy , Fogel Keith E. , Inns Daniel
Published: April 2011

Surface texturing processes for thin silicon solar cells ideally remove as little Si as possible relative to amount of topography generated. Here we describe how a micron-scale quasi-pyramidal texture may be achieved in Si layers with arbitrary crystallinity using a phase-segregated mask in combination with reactive ion etching (RIE). The Si to be textured is coated with a thin barrier layer followed by a layer of Al-Si alloy which phase-segregates into micron-sized regions of Al and Si after low temperature (<450 °C) annealing. One omponent of the mask is selectively etched away and the Si under the exposed barrier regions is etched by a process that gives the desired depth and lateral undercut. In this paper we show the dependence of the segregated Al-Si morphology on Al-Si alloy composition, thickness, and annealing conditions, and then present examples of texturing produced in single crystal Si by these masks in combination with CF4/O2 reactive ion etching.
High-rate Etching of Organic Materials using Gas Cluster Beam
Authors: Suda Takanori , Toyoda Noriaki , Yamada Isao
Published: April 2011

Organic materials or polymers, which are widely used in electronic devices, are easily damaged by energetic ion or electron bombardment. Therefore, it is difficult to use conventional ion or electron beam processes for etching organic materials. In this study, a gas cluster beam possessing kinetic energy of the order of several hundred eV was used as a novel means to realize high-rate, low-damage etching. Polyethylene (PE) and polyvinyl chloride (PVC) were used as the target organic materials. Using a SF6 cluster beam, the etching depth suddenly increased when the nozzle gas pressure exceeded 0.6 MPa, as in the case of cluster beam formation. When the SF6 gas pressure in the nozzle was 1.2 MPa, the etching rates of PVC and PE were 2.88 μm/s and 1.62 μm/s, respectively. The dependence of the etching effect on cluster size was studied by varying the gas temperature. The etching depth of PVC increased with increasing average cluster size and intensity of the beam. The flow rate of the gas was constant; hence, etching of the organic materials did not occur because of the individual impact of the molecular beam. In fact, it occurred because of the neutral cluster, which had a large total kinetic energy. The energy per molecule of the gas cluster beam is of the order of several tens of meV; hence, high-rate, low-damage etching of organic materials can be potentially achieved.
Formation of Silicon and Silicon-Based Semiconductor Materials via Photoinduced Reaction Using Femtosecond Laser
Authors: Nishimura Masakazu , Kanehira Shingo , Sakakura Masaaki , Shimotsuma Yasuhiko , Miura Kiyotaka , Hirao Kazuyuki
Published: April 2011

We have succeeded in silicon (Si) precipitation inside a glass/aluminum (Al) sandwich structure via photoinduced reaction using femtosecond (fs) laser irradiation. The sandwich structure was fabricated by direct bonding below 573 K. Raman spectra at the photomodified area indicated that Si crystals formed at the interface between the glass and metallic Al after the laser irradiation. In addition, the particle size of the precipitated Si could be changed by changing the pulse energy of the laser. Furthermore, we have also focused the laser pulses on Fe-Si film to trigger crystallization and phase transformation of FexSiy at the interface between Fe/Si multilayer and glass.
Coupling of Defect Fields to Domains and Phase Transition Characteristics of Ferroelectric Thin Films with Charged Defects
Authors: Misirlioglu Ibrahim B. , Cologlu Hale N. , Yildiz Mehmet
Published: April 2011

We analyze the effect of charged defects on the electrical domains, phase transition characteristics and electrical properties of ferroelectric thin films with thin dead layers using a non-linear thermodynamic model. Depending on their density and field strength, defects can pin and couple to electrical domains in the film. For ultrathin films, depolarizing effects dominate and the transition from the paraelectric state is into the multidomain ferroelectric state during cooling and is strongly smeared. The competition between defect induced extrinsic effects and the dead layer related limit is demonstrated.
TEM studies of the ternary Ti36 Al62 Nb2 alloy
Authors: Chakravadhanula V.S.K. , Kelm K. , Kienle L. , Duppel V. , Lotnyk A. , Sturm D. , Heilmaier M. , Schmitz G. J. , Drevermann A. , Stein F. , Palm M.
Published: April 2011

Al-rich Ti-Al alloys attracted some attention during the past years due to the possibility of their application as light-weight, high-performance materials at elevated temperatures. The effect of the addition of Nb to Al-rich Ti-Al alloys has been studied for Ti36 Al62 Nb2 by a combined approach of transmission electron microscopy (TEM) techniques for unraveling the structure and composition at the nanoscale. Structural analyses on as-cast ternary alloys revealed the presence of h-TiAl2-, Ti3Al5- and γ-TiAl-type phases. After heat treatment, phase transformations like the replacement of the metastable h-TiAl2-type by the stable r-TiAl2-type were identified. Additionally, changes of the microstructural features like the formation of interfaces with different orientation relationships are apparent. The orientation and interfacial relationships involved are compared to those of binary Ti-Al alloys rich in Al.
Robustness versus Performance Assessment for Different Gamma-TiAl Processing Routes
Authors: Thomas Marc
Published: April 2011

One of the main driving force for the development of advanced structural materials is weight saving especially in the transportation industry in order to reduce CO2 emission. The utilization of gamma aluminides, as good candidates for aerospace applications, is strongly related to the development of a cost-effective and robust processing route, as far as possible. It is well established that the processing route, i.e. cast, wrought or PM, has a dramatic effect on the microstructure and texture of gamma-TiAl alloys. Therefore, significant microstructural variations through post-heat treatments coupled with compositional modifications can only guarantee a proper balance of desired properties. However, a number of metallurgical factors during the processing steps can contribute to some scattering in properties. This review will highlight several critical process variables in terms of the resulting g-TiAl microstructures. Of primary importance is the as-cast texture which is difficult to control and may contribute to prefer some alternative processing routes to ensure a better repeatability in mechanical results. Some innovative processing techniques for controlling the structure will then be presented. The main point which will be discussed in this paper is whether an approach leading to a robust process would not be at the expense of the high performance of the structural material.
Effects of Geometric Constraint on Phase Selection and Segregation in Cast TiAl
Authors: Zhang Sailei , Johnson David R. , Krane Matthew J.M.
Published: April 2011

Simulations of directional solidification of binary peritectic TiAl alloys through ceramic preforms consisting of narrow straight channels with spacings on the order of the dendritic tip radius were performed with a modified cellular automaton coupled to a finite volume calculation of solute diffusion. Depending upon the channel spacing, the microstructure may be refined after dendritic growth through the preform. As the channel width decreases, the lateral solute diffusion in the liquid is more constrained, changing the morphology of the primary phase from dendritic to cellular. In narrow channels, the liquid concentration gradient ahead of the solid/liquid interface decreases resulted in lower growth velocities and higher undercoolings. For hypo-peritectic TiAl alloys, growth conditions that lead to growth of β dendrites can result in α nucleation and growth in narrow channels due to the geometric constraint on solute diffusion.
Mechanical Properties of Cr5Si3 with the D8m Structure
Authors: Ochiai Yuji , Kishida Kyosuke , Tanaka Katsushi , Inui Haruyuki
Published: April 2011

Elastic properties, thermal expansion and deformation behavior of Cr5Si3 with the D8m structure were investigated using single crystals. From the values of Cauchy pressures as well as the ratio of the polycrystalline bulk modulus (B) to shear moduls (G) estimated from single-crystal elastic constants (cij), deformation behavior of Cr5Si3 is expected to be relatively brittle compared to Mo5Si3 with the same crystal structure. However, plastic deformation of Cr5Si3 is confirmed above 900 ~ 1100 °C depending on the loading axis orientations.
Synthesis and Microstructure of Porous Aluminum and Intermetallic Nanomaterials
Authors: Purdy Andrew P. , Miller Joel B.
Published: April 2011

A series of porous aluminum-based materials are prepared by the reduction of solutions of metal chlorides with lithium powder in diethyl ether under dry argon. The reactants must be combined slowly, but either order of addition is used. The reduction of AlCl3 produces hollow Al balls composed of ~100 nm aluminum particles in nearly quantitative yield after the LiCl byproduct is washed away with dry tetrahydrofuran. Similar structures are formed when mixtures of AlCl3 and SiCl4, are reduced, except that the second component has the effect of reducing the Al nanoparticle size. Mixtures of AlCl3 with FeCl3 reduce to similar ball-like porous structures that are composed of Al, Fe, and Fe-Al intermetallic nanoparticles. When AlCl3 and ZnCl2 are co-reduced, flake-like nanoporous structures are obtained, and solutions of AlCl3 + VCl3 produce more compact nanoporous structures. Some side reactions involving ether cleavage that produces aluminum alkoxides and alkyls do occur, and the amount of side reaction is dependent on the identity of the second metal. The reduction of AlCl3 with excess (4 eq) Li powder produces LiAl nanomaterials. NMR shows the intermetallic compound LiAl to be the only Li-Al intermetallic present.
Microstructural and mechanical properties of ternary Mo-Si-B alloys resulting from different processing routes
Authors: Krüger Manja , Heilmaier Martin , Shyrska Veronika , Loboda Petr I.
Published: April 2011

Mo-base silicide alloys take advantage of their outstanding intrinsic properties, notably the high melting point and, thus, their excellent mechanical and creep strength. We demonstrate how the processing route influences the microstructure and consequently the mechanical and oxidation behaviour. Therefore two fabrication routes, a powder metallurgical (PM) and a zone melting (ZM) process, both starting from elemental powders, were used to prepare several Mo-Si-B alloys with varying chemical compositions. While PM processing leads to an ultrafine microstructure with a continuous Mo solid solution (“α-Mo”) matrix and embedded particles of the two intermetallic compounds Mo3Si and Mo5SiB2, the directionally solidified (ZM) materials possess a coarse grained structure composed of an intermetallic matrix with dendritic islands of α-Mo. A comparative assessment of the mechanical behaviour of the alloys utilizing both the Vickers indentation fracture (VIF) technique and three-point bending tests emphasizes the beneficial effect of a continuous Mo matrix resulting in increased room temperature fracture toughness and a reduction of the brittle-to-ductile-transition-temperature (BDTT). Likewise, the positive effect of the fine grained and homogeneous microstructure on oxidation performance is shown by the evaluation of mass change during heat treatment at 1100°C.
Study of the effect of Al, Cr and Sn additions on the microstructure and properties of Nb silicide based alloys
Authors: Tsakiropoulos P , Zelenitsas K , Vellios N
Published: April 2011

The effects of Al, Cr and Sn on segregation, microstructure, phase stability and hardness of Nb-24Ti-18Si-5X (X = Al, Cr, Sn, at%) alloys were studied. The microstructure of the as cast alloys with Cr, Al and Sn respectively contained (Nb,Ti)ss, Nb3Si, αNb5Si3 and C14-NbCr2 Laves, (Nb,Ti)ss and βNb5Si3 and (Nb,Ti)ss, Nb3Sn and Nb5Si3. The microstructures of the heat treated alloys with Al and Cr (1500 oC/100 h) contained (Nb,Ti)ss and αNb5Si3 and the alloy with Sn (1200 oC/100 h) contained (Nb,Ti)ss, Nb3Sn and αNb5Si3. Compared with Al and Cr, alloying with Sn enhanced the stability of the as cast microstructure, caused strong macrosegregation of Si and Ti, suppressed the segregation of Ti in the (Nb,Ti)ss that was promoted by Al and Cr, had the strongest effect on the macrohardness of the cast and heat treated alloys and on the vol% of the Nbss. All three alloying additions promoted the transformation of βNb5Si3 to αNb5Si3 during heat treatment and decreased the hardness of Nb5Si3 in the as cast alloys with Sn having the strongest effect and Al the weakest. After the heat treatment the hardness of Nb5Si3 increased in the alloys containing Cr and Sn and decreased in the Al containing alloy with Cr having the strongest effect.
Morphology change of γ′ precipitates in γ/γ′ two-phase microstructure in Co-based superalloys by higher-order alloying
Authors: Tanaka Katsushi , Ooshima Masahiro , Okamoto Norihiko L. , Kishida Kyosuke , Inui Haruyuki
Published: April 2011

Changes in the morphology of γ′ precipitates in a γ/γ′ two-phase microstructure in Co-based superalloys, which occur through higher-order alloying, have been investigated. The shape of γ′ precipitates changes from a cuboid to an irregularly rounded shape when the Ta content increases to 4 at.%. The irregular shape of the γ′ precipitates changes to cuboid again upon further alloying with 2 at.% Mo. Changes in the morphology of γ′ precipitates are closely related to variations in the lattice misfit between γ and γ′ phases upon alloying. A lattice misfit increases with an increase in Ta content, which makes γ/γ′ interfaces incoherent when the lattice misfit exceeds a critical value. On the contrary, the lattice misfit decreases upon alloying with Mo. Changes in the lattice misfit upon alloying are well explained through the partition behavior of alloying elements and their atomic volume.