bluuebunny/crossref_metadata_2025 huggingface dataset:
Prevalence of molecular markers of anti-malarial drug resistance in Plasmodium vivax and Plasmodium falciparum in two districts of Nepal
Authors: Ranjitkar Samir , Schousboe Mette L , Thomsen Thomas Thyge , Adhikari Madhav , Kapel Christian MO , Bygbjerg Ib C , Alifrangis Michael
Published: April 2011

Background

Sulphadoxine-pyrimethamine (SP) and chloroquine (CQ) have been used in treatment of falciparum and vivax malaria in Nepal. Recently, resistance to both drugs have necessitated a change towards artemisinin combination therapy (ACT) against Plasmodium falciparum in highly endemic areas. However, SP is still used against P. falciparum infections in low endemic areas while CQ is used in suspected cases in areas with lack of diagnostic facilities. This study examines the prevalence of molecular markers of CQ and SP resistance in P. falciparum and Plasmodium vivax to determine if high levels of in vivo resistance are reflected at molecular level as well.

Methods

Finger prick blood samples (n = 189) were collected from malaria positive patients from two high endemic districts and analysed for single nucleotide polymorphisms (SNPs) in the resistance related genes of P. falciparum and P. vivax for CQ (Pfcrt, Pfmdr1, Pvmdr1) and SP (Pfdhfr, Pfdhps, Pvdhfr), using various PCR-based methods.

Results and discussion

Positive P. vivax and P. falciparum infections were identified by PCR in 92 and 41 samples respectively. However, some of these were negative in subsequent PCRs. Based on a few P. falciparum samples, the molecular level of CQ resistance in P. falciparum was high since nearly all parasites had the Pfcrt mutant haplotypes CVIET (55%) or SVMNT (42%), though frequency of the Pfmdr1 wild type haplotype was relatively low (35%). Molecular level of SP resistance in P. falciparum was found to be high. The most prevalent Pfdhfr haplotype was double mutant CNRNI (91%), while frequency of Pfdhps double mutant SGEAA and AGEAA were 38% and 33% respectively. Combined, the frequency of quadruple mutations (CNRNI-SGEAA/AGEAA) was 63%. Based on P. vivax samples, low CQ and SP resistance were most likely due to low prevalence of Pvmdr1 Y976F mutation (5%) and absence of triple/quadruple mutations in Pvdhfr.

Conclusions

Based on the limited number of samples, prevalence of CQ and SP resistance at molecular levels in the population in the study area were determined as high in P. falciparum and low in P. vivax. Therefore, CQ could still be used in the treatment of P. vivax infections, but this remains to be tested in vivo while the change to ACT for P. falciparum seems justified.
Tumor escape and progression of HER-2/neu negative breast cancer under immune pressure
Authors: Kmieciak Maciej , Payne Kyle K , Idowu Michael O , Grimes Margaret M , Graham Laura , Ascierto Maria-Libera , Wang Ena , Wang Xiang-Yang , Bear Harry D , Manjili Masoud H
Published: April 2011

Background

Emerging data from pre-clinical and clinical studies suggest that HER-2/neu-specific T cell responses could induce HER-2/neu antigen loss in the tumor cells. These data suggest that patients with HER-2/neu negative breast cancer might have had HER-2/neu positive premalignant lesions in the past that progressed to HER-2/neu negative breast cancer under HER-2/neu-specific immune pressure.

Methods

We conducted a pilot study in patients with HER-2/neu positive and HER-2/neu negative breast cancers as well as a patient with ductal carcinoma in situ (DCIS). HER-2/neu expression was determined by FISH. HER-2/neu-specific T cell responses were determined by using IFN-γ ELISA. Expression of IFN-γ Rα in the tumors was determined by immunohistochemistry analysis of paraffin-embedded tissues.

Results

We determined that majority of (10 of 12) patients with HER-2/neu negative breast cancer had HER-2/neu-specific IFN-γ producing T cell responses which was stronger than those in patients with HER-2/neu positive tumors. Such immune responses were associated with nuclear translocation of IFN-γ Rα in their tumor cells. Patient with DCIS also showed HER-2/neu-specific T cell responses.

Conclusion

These data suggest that conducting retrospective studies in patients with HER-2/neu negative breast cancers and prospective studies in patients with HER-2/neu positive DCIS can determine whether HER-2/neu negative invasive carcinomas arise from HER-2/neu positive DCIS under the immune pressure.
Preparation of SnS2 colloidal quantum dots and their application in organic/inorganic hybrid solar cells
Authors: Tan Furui , Qu Shengchun , Wu Ju , Liu Kong , Zhou Shuyun , Wang Zhanguo
Published: April 2011

Dispersive SnS2 colloidal quantum dots have been synthesized via hot-injection method. Hybrid photovoltaic devices based on blends of a conjugated polymer poly[2-methoxy-5-(3",7"dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) as electron donor and crystalline SnS2 quantum dots as electron acceptor have been studied. Photoluminescence measurement has been performed to study the surfactant effect on the excitons splitting process. The photocurrent of solar cells with the hybrid depends greatly on the ligands exchange as well as the device heat treatment. AFM characterization has demonstrated morphology changes happening upon surfactant replacement and annealing, which can explain the performance variation of hybrid solar cells.
Role of HCV Core gene of genotype 1a and 3a and host gene Cox-2 in HCV-induced pathogenesis
Authors: Jahan Shah , Khaliq Saba , Ijaz Bushra , Ahmad Waqar , Hassan Sajida
Published: April 2011

Background

Hepatitis C virus (HCV) Core protein is thought to trigger activation of multiple signaling pathways and play a significant role in the alteration of cellular gene expression responsible for HCV pathogenesis leading to hepatocellular carcinoma (HCC). However, the exact molecular mechanism of HCV genome specific pathogenesis remains unclear. We examined the in vitro effects of HCV Core protein of HCV genotype 3a and 1a on the cellular genes involved in oxidative stress and angiogenesis. We also studied the ability of HCV Core and Cox-2 siRNA either alone or in combination to inhibit viral replication and cell proliferation in HCV serum infected Huh-7 cells.

Results

Over expression of Core gene of HCV 3a genotype showed stronger effect in regulating RNA and protein levels of Cox-2, iNOS, VEGF, p-Akt as compared to HCV-1a Core in hepatocellular carcinoma cell line Huh-7 accompanied by enhanced PGE2 release and cell proliferation. We also observed higher expression levels of above genes in HCV 3a patient's blood and biopsy samples. Interestingly, the Core and Cox-2-specific siRNAs down regulated the Core 3a-enhanced expression of Cox-2, iNOS, VEGF, p-Akt. Furthermore, the combined siRNA treatment also showed a dramatic reduction in viral titer and expression of these genes in HCV serum-infected Huh-7 cells. Taken together, these results demonstrated a differential response by HCV 3a genotype in HCV-induced pathogenesis, which may be due to Core and host factor Cox-2 individually or in combination.

Conclusions

Collectively, these studies not only suggest a genotype-specific interaction between key players of HCV pathogenesis but also may represent combined viral and host gene silencing as a potential therapeutic strategy.
Vertebrates used for medicinal purposes by members of the Nyishi and Galo tribes in Arunachal Pradesh (North-East India)
Authors: Chakravorty Jharna , Meyer-Rochow V Benno , Ghosh Sampat
Published: April 2011

Arunachal Pradesh, the easternmost part of India, is endowed with diverse natural resources and inhabited by a variety of ethnic groups that have developed skills to exploit the biotic resources of the region for food and medicines. Information on animals and animal parts as components of folk remedies used by local healers and village headmen of the Nyishi and Galo tribes in their respective West Siang and Subansiri districts were obtained through interviews and structured questionnaires. Of a total of 36 vertebrate species used in treatments of ailments and diseases, mammals comprised 50%; they were followed by birds (22%), fishes (17%), reptiles (8%) and amphibians (3%). Approximately 20 common complaints of humans as well as foot and mouth disease of cattle were targets of zootherapies. Most commonly treated were fevers, body aches and pains, tuberculosis, malaria, wounds and burns, typhoid, smallpox, dysentery and diarrhoea, jaundice, and early pregnancy pains. Very few domestic animal species (e.g., goat and cattle) were used zootherapeutically. More frequently it was wild animals, including endangered or protective species like hornbill, pangolin, clouded leopard, tiger, bear, and wolf, whose various parts were either used in folk remedies or as food. Some of the animal-based traditional medicines or animal parts were sold at local markets, where they had to compete with modern, western pharmaceuticals. To record, document, analyze and test the animal-derived local medicines before they become replaced by western products is one challenge; to protect the already dwindling populations of certain wild animal species used as a resource for the traditional animal-derived remedies, is another.
The loop-less tmCdc34 E2 mutant defective in polyubiquitination in vitro and in vivo supports yeast growth in a manner dependent on Ubp14 and Cka2
Authors: Lass Agnieszka , Cocklin Ross , Scaglione Kenneth M , Skowyra Michael , Korolev Sergey , Goebl Mark , Skowyra Dorota
Published: April 2011

Background

The S73/S97/loop motif is a hallmark of the Cdc34 family of E2 ubiquitin-conjugating enzymes that together with the SCF E3 ubiquitin ligases promote degradation of proteins involved in cell cycle and growth regulation. The inability of the loop-less Δ12Cdc34 mutant to support growth was linked to its inability to catalyze polyubiquitination. However, the loop-less t riple m utant (tm) Cdc34, which not only lacks the loop but also contains the S73K and S97D substitutions typical of the K73/D97/no loop motif present in other E2s, supports growth. Whether tmCdc34 supports growth despite defective polyubiquitination, or the S73K and S97D substitutions, directly or indirectly, correct the defect caused by the loop absence, are unknown.

Results

tmCdc34 supports yeast viability with normal cell size and cell cycle profile despite producing fewer polyubiquitin conjugates in vivo and in vitro. The in vitro defect in Sic1 substrate polyubiquitination is similar to the defect observed in reactions with Δ12Cdc34 that cannot support growth. The synthesis of free polyubiquitin by tmCdc34 is activated only modestly and in a manner dependent on substrate recruitment to SCFCdc4. Phosphorylation of C-terminal serines in tmCdc34 by Cka2 kinase prevents the synthesis of free polyubiquitin chains, likely by promoting their attachment to substrate. Nevertheless,
tm

CDC34 yeast are sensitive to loss of the Ubp14 C-terminal ubiquitin hydrolase and DUBs other than Ubp14 inefficiently disassemble polyubiquitin chains produced in
tm

CDC34 yeast extracts, suggesting that the free chains, either synthesized de novo or recycled from substrates, have an altered structure.

Conclusions

The catalytic motif replacement compromises polyubiquitination activity of Cdc34 and alters its regulation in vitro and in vivo, but either motif can support Cdc34 function in yeast viability. Robust polyubiquitination mediated by the S73/S97/loop motif is thus not necessary for Cdc34 role in yeast viability, at least under typical laboratory conditions.
Monoallelic deletion of the microRNA biogenesis gene Dgcr8 produces deficits in the development of excitatory synaptic transmission in the prefrontal cortex
Authors: Schofield Claude M , Hsu Ruby , Barker Alison J , Gertz Caitlyn C , Blelloch Robert , Ullian Erik M
Published: April 2011

Background

Neuronal phenotypes associated with hemizygosity of individual genes within the 22q11.2 deletion syndrome locus hold potential towards understanding the pathogenesis of schizophrenia and autism. Included among these genes is Dgcr8, which encodes an RNA-binding protein required for microRNA biogenesis. Dgcr8 haploinsufficient mice (Dgcr8+/-) have reduced expression of microRNAs in brain and display cognitive deficits, but how microRNA deficiency affects the development and function of neurons in the cerebral cortex is not fully understood.

Results

In this study, we show that Dgcr8+/- mice display reduced expression of a subset of microRNAs in the prefrontal cortex, a deficit that emerges over postnatal development. Layer V pyramidal neurons in the medial prefrontal cortex of Dgcr8+/- mice have altered electrical properties, decreased complexity of basal dendrites, and reduced excitatory synaptic transmission.

Conclusions

These findings demonstrate that precise microRNA expression is critical for the postnatal development of prefrontal cortical circuitry. Similar defects in neuronal maturation resulting from microRNA deficiency could represent endophenotypes of certain neuropsychiatric diseases of developmental onset.
Microarray based analysis of an inherited terminal 3p26.3 deletion, containing only the CHL1 gene, from a normal father to his two affected children
Authors: Cuoco Cristina , Ronchetto Patrizia , Gimelli Stefania , Béna Frédérique , Divizia Maria Teresa , Lerone Margherita , Mirabelli-Badenier Marisol , Mascaretti Monica , Gimelli Giorgio
Published: April 2011

Background

terminal deletions of the distal portion of the short arm of chromosome 3 cause a rare contiguous gene disorder characterized by growth retardation, developmental delay, mental retardation, dysmorphisms, microcephaly and ptosis. The phenotype of individuals with deletions varies from normal to severe. It was suggested that a 1,5 Mb minimal terminal deletion including the two genes CRBN and CNTN4 is sufficient to cause the syndrome.

In addition the CHL1 gene, mapping at 3p26.3 distally to CRBN and CNTN4, was proposed as candidate gene for a non specific mental retardation because of its high level of expression in the brain.

Methods and Results

we describe two affected siblings in which array-CGH analysis disclosed an identical discontinuous terminal 3p26.3 deletion spanning less than 1 Mb. The deletion was transmitted from their normal father and included only the CHL1 gene. The two brothers present microcephaly, light mental retardation, learning and language difficulties but not the typical phenotype manifestations described in 3p- syndrome.

Conclusion

a terminal 3p26.3 deletion including only the CHL1 gene is a very rare finding previously reported only in one family. The phenotype of the affected individuals in the two families is very similar and the deletion has been inherited from an apparently normal parent. As already described for others recurrent syndromes with variable phenotype, these findings are challenging in genetic counselling because of an evident variable penetrance.
Tissue inhibitor of metalloproteinase 1 (TIMP-1) deficiency exacerbates carbon tetrachloride-induced liver injury and fibrosis in mice: involvement of hepatocyte STAT3 in TIMP-1 production
Authors: Wang Hua , Lafdil Fouad , Wang Lei , Yin Shi , Feng Dechun , Gao Bin
Published: April 2011

Background

Tissue inhibitor of metalloproteinase 1 (TIMP-1), which is thought to be produced mainly by activated hepatic stellate cells and Kupffer cells in the liver, plays a pivotal role in matrix remodeling during liver injury and repair; while the effect of TIMP-1 on hepatocellular damage remains obscure.

Results

Hepatic expression of TIMP-1 mRNA and protein was up-regulated both in acute and chronic liver injury induced by carbon tetrachloride (CCl4). Compared with wild-type mice, TIMP-1 knockout mice were more susceptible to CCl4-induced acute and chronic liver injury, as shown by higher levels of serum alanine aminotransferase (ALT), greater number of apoptotic hepatocytes, and more extended necroinflammatory foci. TIMP-1 knockout mice also displayed greater degree of liver fibrosis after chronic CCl4injection when compared with wild-type mice.In vitrotreatment with TIMP-1 inhibited cycloheximide-induced cell death of primary mouse hepatocytes. Finally, up-regulation of TIMP-1 in the liver and serum after chronic CCl4treatment was markedly diminished in hepatocyte-specific signal transducer and activator of transcription 3 (STAT3) knockout mice.In vitrotreatment with interleukin-6 stimulated TIMP-1 production in primary mouse hepatocytes, but to a lesser extent in STAT3-deficient hepatocytes.

Conclusions

TIMP-1 plays an important role in protecting against acute and chronic liver injury and subsequently inhibiting liver fibrosis induced by CCl4. In addition to activated stellate cells and Kupffer cells, hepatocytes are also responsible for TIMP-1 production during liver injury via a STAT3-dependent manner.
Nasca classification of hemivertebra in five dogs
Authors: Besalti Omer , Ozak Ahmet , Pekcan Zeynep , Eminaga Salih
Published: April 2011

Five dogs, four small mixed breed and a Doberman Pinscher, presented in our clinic with hemivertebra. Complete physical, radiological and neurological examinations were done and the spinal deformities were characterized in accord with the Nasca classification used in human medicine. Two dogs had multiple hemivertebrae (round, oval or wedge-shaped: Type 3) in the thoracic region; one dog had an individual surplus half vertebral body (Type 1) plus a wedge-shaped hemivertebra (Type 2b) in the lumbar region; one dog had multiple hemivertebrae which were fused on one side (Type 4a) in the thoracic region; and one dog had a wedge-shaped hemivertebra (Type 2a) in the cervical region.
Guest Editor's Letter
Authors: Roitman Janet
Published: April 2011

Over the past years, France has been rocked not only by violent demonstrations in the banlieues (city outskirts) but also by raging debates regarding the place of “postcolonial studies” in the French archive and in current scholarship. The dispute over postcolonial studies in this European venue is symptomatic of disagreement about the status of French colonial history and the category of race in the construction of contemporary national narratives. The varied and conflicting understandings of both postcolonial studies and the nature of empires entail fierce disagreement over the status of race and immigration in France (if not Europe) today. This introductory essay reviews the arguments presented in the main articles, discussion papers, and Doxa essays included in this special issue. The author enters the debate by arguing against the notion that postcolonial studies can be summarized as a theoretical form. Because postcolonial studies has produced compelling accounts of the epistemological bases for the production of difference and historical forms of regulation, its intellectual force lies in the constant postulation of alternative narratives and counter-histories in a relentless effort to displace the fault lines of power-knowledge. However, to what extent can this contemporary scholarship rid itself of the categories of nineteenth-century academic disciplines? By considering the third languages of the postcolonial world, one can address this predicament of thinking and reasoning in the language of the educator, the statesman, the colonizer, the slaver, the exterminator. In the end, though, an epistemological rupture would entail more than differential languages; it requires that significance no longer be located in historical inscription.
Imagin(in)g Racial France: Take 1 KaKuDji
Authors: Malaquais Dominique
Published: April 2011

France is most cosmopolitan where it is least central. If the City of Lights is a cosmopolis, it is far less so in Saint-Germain-des-Près or the Marais than in its disenfranchised banlieues (suburbs) and many an (ex) colonies on which its language was and continues to be imposed. Here an extraordinary brassage is at work—a mix and, at times, a linking of arms, a wealth of commentary and engaged political analysis—that speaks, as few words can, to the tangible reality of postcolonial France. Nowhere is this as evident as in the explosion of artistic activity taking place in Kinshasa, Democratic Republic of the Congo, and Douala, Cameroon, or, closer to “home,” Saint-Denis and Mantes-la-Jolie. Individual artists and collectives, activist art spaces and teaching hubs, some wholly ephemeral and few of which make it to the limelight of the city center, are located there, many in closer touch with the heartbeat of twenty-first-century global life than are the people and places au centre that attract international collectors, art aficionados, and pundits bent on telling us the state of the world.
Fabrication and Characterization of Cu-14Al-3.5Ni Shape Memory Alloys by Ingot Metallurgy
Authors: Ganesh K. Jai , Suresh Arunya
Published: April 2011

Shape Memory Alloys (SMAs) are versatile functional materials with an I.Q of their own. This class of SMART Materials exhibit unique properties like superelasticity and shape memory effect (SME) which have made them suitable for potential applications. Although Ni-Ti SMAs have attracted attention ever since their inception in 1962, Cu based SMAs due to their ease in fabrication, cost effectiveness and high temperature properties are gaining immense popularity. This research aimed at the fabrication of Cu-14 Al-3.5 Ni (wt %) Shape Memory Alloy by a simple cost effective route and its characterization to correlate its structure and properties. The alloy of desired composition was melted in an Electric Resistance Furnace at 1473 K and cast in a metallic mould. Homogenization was carried out at 1123 K for twenty four hours followed by analysis of chemical composition by Optical Emission Spectroscopy. Transformation temperatures of the alloy were determined using Differential Scanning Calorimetry. Heat treatment operations were carried out at 1273 K for one hour followed by quenching in different media. Optical and SEM micrographs were taken at various magnifications and the formation of self accommodating martensite was observed which was further confirmed by X-Ray Diffraction technique. Further improvements in the mechanical properties of the alloy by quaternary additions of Mn and Ti have been cited. Finally, SME was observed in a rolled strip of the alloy, thus concreting the obtained results.
Cross-linkable Highly Fluorinated Polymers with Tunable Refractive Index
Authors: Qi Yinghua , Jiang Jia , Callender Claire L. , Ding Jianfu , Day Michael
Published: April 2011

Novel cross-linkable, highly fluorinated poly(arylene ether ketone/sulfone)s have been prepared by copolycondensation reactions of a perfluorinated aromatic ketone or sulfone with 4,4'-(hexafluoroisopropylidene)diphenol (6F-BPA)/4,4'-isopropylidene bis(2,6-dibromophenol) (4Br-BPA) and a tetrafluorostyrol-containing bisphenol, at low temperature in the presence of calcium hydride and cesium fluoride. Property investigations have shown that these polymers can be easily processed into thin films, have good thermal stability, and exhibit low optical loss at 1550 nm (0.4 – 0.5 dB/cm). The refractive index can be tailored over a range of 1.50 to 1.57, allowing the polymers to be used as both core and cladding materials in optical waveguiding applications.
A Smart Medical Diagnostic Tool using Resistive Sensor Technology
Authors: Iyer Krithika K. , Prasad A. K. , Gouma P. I.
Published: April 2011

This paper reports on the development of a smart sensor array consisting of selective gas sensing elements for use in disease diagnosis to monitor signaling gases. These are gases typically found in exhaled human breath that can serve as biomarkers for specific diseases. Utilizing the polymorphic selectivity of semiconducting metal oxides and by employing temperature modulation we have developed a smart gas selective sensor array able to identify and discriminate between isoprene, NOx, alcohols and amines/NH3. The sensing elements are thin films based on the various polymorphs of molybdenum trioxide. A breath analysis system based on our smart sensor array can be used for non-invasive monitoring and differential diagnosis of diseases.
Piezoelectric polymers
Authors: Bauer Siegfried , Bauer-Gogonea Simona , Dansachmüller Mario , Dennler Gilles , Graz Ingrid , Kaltenbrunner Martin , Keplinger Christoph , Reiss Howard , Sariciftci Niyazi Serdar , Singh Thokchom Birendra , Schwödiauer Reinhard
Published: April 2011

The science and technology of piezoelectric polymers has long been dominated by ferroelectric polymers from the polyvinylidene fluoride (PVDF) family. The piezoelectricity in this polymer class arises from the strong molecular dipoles within the polymer chain and from the resulting change of the dipole density upon application of a mechanical stimulus. Ferroelectric polymers show moderate piezoelectric coefficients (d33 and d31,32 around 20-30 pC/N) in comparison to ceramic piezoelectrics, with an acoustic impedance comparable to that of water. The thermal stability of the piezoelectric effect is limited to below 100°C, though stability up to 125°C has recently been announced. Applications of ferroelectric polymers emerged in many niches. A good example of a success story for PVDF applications are clamp-on transducers used as pressure sensor for Diesel injection lines, with selling numbers over 50 million pieces per year. A relatively new development are relaxor ferroelectric polymers, based on electron-irradiated poly(vinylidene fluoride) trifluoroethylene copolymers or on terpolymers of vinylidene fluoride, trifluoroethylene and chlorofluoroethylene. Relaxor ferroelectric copolymers exhibit strong electrostriction and thus large piezoelectric coefficients, when used under electric dc-bias fields. Internally charged cellular polymer foam electrets (ferroelectrets) resemble close similarities to ferroelectrics. They display large intrinsic piezoelectric d33-coefficients well above 100 pC/N and very small d31 and d32 coefficients, coupled with a limited thermal stability up to 50°C in the polypropylene workhorse material. The materials are pioneered in Finland and already entered the market in niches, for example in musical pick-ups. They promise large area applications, for example in surveillance and intruder systems. Finally, organic semiconductors have shown a rather unusual electromechanical response, governed by a power law S=V3/2 of strain S versus voltage V, located in between traditional piezoelectricity and electrostriction. The field of piezoelectric polymers therefore received new stimulus, and the material class of piezoelectric polymers has been significantly broadened recently.
Soft Actuators based on Polypyrrole and Polyaniline Composite Films
Authors: Kaneto Keiichi , Takashima Wataru
Published: April 2011

Elongation and contraction of polypyrrole and poly(3-methoxyaniline-5-sulfonate) (PMAS) composite films induced upon electrochemical oxidation and reduction, viz., electrochemomechanical deformation (ECMD) are studied. The composite films were electrochemically prepared in electrolyte solutions of pyrrole and dodecylbenzene sulfonic (DBS) acid with a presence of PMAS acid. The contents of DBS and PMAS were varied. Films which were obtained at higher contents of PMAS, were gel like due to a lot of water content. The change of film length due to ECMD was measured as functions of various electrolytes in either aqueous or organic solvents. The results indicated that films exhibited both cathodic and anodic expansions depending on the bulkiness of cations and anions as well as the content of PMAS.
Non-linear charge transport in polythiophene under high AC field
Authors: Obrzut Jan , Psurek Tatiana , Chiang C. K. , DeLongchamp Dean M.
Published: April 2011

Complex impedance and conductivity were measured for regioregular poly(3-hexylthiophene) (P3HT) at alternating current (AC) voltages using a waveform technique. The waveforms were Fourier transformed from time domain to frequency domain and analyzed at fundamental and higher order harmonic frequencies. It was found that the impedance of the semi-conducting P3HT decreases with increasing electric field strength. The non-linear charge transport is dominated by a third harmonic response that originates from extended polarizability of π-type electronic states. The third order non-linear conductivity can be used to quantify the effect of an electric field on the conduction mechanism and to correlate the intrinsic charge carriers mobility with molecular structure.
Symmetry reduction of δ-plutonium: an electronic-structure effect
Authors: Moore Kevin T. , Söderlind Per , Schwartz Adam J. , Laughlin David
Published: April 2011

Using first-principles density-functional theory calculations, we show that the anomalously large anisotropy of δ-plutonium is a consequence of greatly varying bond-strengths between the 12 nearest neighbors. Employing the calculated bond strengths, we expand the tenants of classical crystallography by incorporating anisotropy of chemical bonds, which yields a structure with the monoclinic space groupCmfor δ-plutonium rather than face-centered cubicFm3m. The reduced space group for δ-plutonium enlightens why the ground state of the metal is monoclinic, why distortions of the metal are viable, and has considerable implications for the behavior of the material as it ages. These results illustrate how an expansion of classical crystallography that accounts for anisotropic electronic structure can explain complicated materials in a novel way.
Statistical Texture Analysis of Microscopy Images for the Purpose of Surface Characterization
Authors: Sadowski Thomas E , Broadbridge Christine Caragianis , DaPonte John
Published: April 2011

This study focuses on the application of an image processing technique known as texture analysis to provide a complementary method to process non-contact atomic force microscopy data. For the current study, SrBi2Ta9O9 (SBT) thin films (∼200nm) on silicon samples were prepared via MOD and imaged via nc-AFM. Previous studies have qualitatively chosen grain size or grain density to quantify the surface characteristics of SBT but for this study texture analysis was used. Results obtained from the texture analysis and the subsequent stepwise discriminant analysis illustrated the importance of grain density and its effect on the statistics obtained from the gray scale cooccurrence matrix.
Combinatorial Methodology on Zeolite Membrane Development for Organic Chemical Process Intensification
Authors: Inoue Tomoya , Hasegawa Yasuhisa , Nagase Takako , Kiyozumi Yoshimichi , Hamakawa Satoshi , Mizukami Fujio
Published: April 2011

Combinatorial methodology for zeolite membrane development is discussed. Zeolite membrane is now attracting attentions as an energy-saving separation apparatus via pervaporation and/or vapor permeation, but sometimes it suffers performance (flux and/or separation factor) deterioration due to lack of chemical stability. We separate the development scheme into three steps – i) zeolite selection via chemical affinity and stability evaluation in powder applying combinatorial methodology, ii) membrane preparation for thus selected zeolite species, and iii) their evaluation in parallel manner. We have successfully developed hydrophilic zeolite membranes with tolerance against acidic environment. Thus developed zeolite membranes were successfully applied esterification reaction from a stoichiometric mixture of a carboxylic acid and an alcohol by assisting equilibrium shift via direct pervaporation from crude reaction solution.
Biocatalytic Activity of Polyethylene Imine Hydrogel Complexes with Transition Metal Ions
Authors: Bektenova Gulnara , Chinibayeva Nurzhan , Bekturov Essen
Published: April 2011

Polyethylene imine hydrogel complexes with various salts of ferric and ferrous iron and also with complex salts of iron as well as insoluble ternary complexes of various composition: low cross-linked polyethylene imine hydrogel - copper (II) nitrate - sodium dodecylbenzylsulfate have been received. Their biocatalytic properties in the reaction of hydrogen peroxide decomposition (catalase activity) have been investigated. It was shown that catalase activity of complexes depends on the salts type and valence state of iron ions. The complexes of ferric iron as well as ternary complexes are most active in the reaction of hydrogen peroxide decomposition.
The fabrication of hydrogel as a microvalve in microfluidic system
Authors: Wei Chehung , Chen Jui-Hung
Published: April 2011

The small volume of sample and fast response time are the primary features of micro fluidic system. It is essential for expensive samples. Microvalve is a key to regulate the flow movement component in an integrated microfluidic system. The working principle of conventional microvalves relies on its mechanical or electromagnetic properties. These valves are neither biocompatible nor are suitable for bioassays. Stimuli-response hydrogels whose properties of efficient mode of energy conversion (chemical to mechanical), excellent biocompatibility and the combination of multiple function (sensing and actuation) have become the leading candidate as engineered microscale components. In this paper, we study the feasibility of thermo-sensitive hydrogel as a valve on the microchip. A metal resistor was used as the temperature regulator. The results show that the miniaturization fabrication of the hydrogel depends on many factors like the volume of the hydrogel (the size of the valve), the vacuum condition (the evaporation rate) and the deposition substrate. The degree of swelling and deswelling of the hydrogel valve depends on the size of the hydrogel. This micro fluidic system is regulated by temperature change of the aqueous solution. The integration with other fluidic component is crucial for practical application.
Water Mobility in Reverse Micelles Studied by Quasielastic Neutron Scattering and Molecular Dynamics Simulation
Authors: Ladanyi Branka , Levinger Nancy
Published: April 2011

Reverse micelles (RMs) are aggregates in which nanoscale droplets of a polar liquid, usually water, are surrounded by a surfactant layer in a nonpolar continuous phase. They are widely used as media for reactions in which the extent of confinement or the presence of a surfactant interface play a central role. We have used molecular dynamics (MD) computer simulation and quasielastic neutron scattering (QENS) and to investigate the mobility of water molecules in reverse micelles. The contribution of water to the QENS signal is enhanced by deuterating the surfactant and the nonpolar phase. Our studies of water mobility have focused on the effects of water pool size, determined by the water/surfactant mole ratios w0, as well as on the properties of the water-surfactant interface. Specifically, we have examined the effects of varying w0 and of substituting other alkali ions for the usual Na+ counterion of the anionic surfactant AOT (bis (2-ethylhexyl) sulfosuccinate)). We find good agreement between the QENS signal and its prediction from MD simulation. This allows us to obtain additional insight into water mobility by analyzing the MD self-intermediate scattering function (ISF) of water hydrogens in terms of contributions from molecular rotation and translation and from molecules in different interfacial layers. MD data indicate that the translational ISF decays nonexponentially due to lower water mobility close to the interface and to confinement-induced restrictions on the range of translational displacements. Rotational relaxation also exhibits nonexponential decay. However, rotational mobility of O-H bond vectors in the interfacial region remains fairly high due to the lower density of water-water hydrogen bonds in the vicinity of the interface.
Chemically Selective Reactions in Confined Spaces in Hybrid Aerogels
Authors: Liu Xipeng , Yao Chunhua , Risen William M
Published: April 2011

By employing novel hybrid silica/functional polymer aerogels, control of the course of chemical reactions between reactants confined inside of the aerogels with reactants whose access to the confinement domain is controlled by diffusion has been explored. Thus, monolithic silica/biopolymer hybrid aerogels have been synthesized with coordinated metal ions that can react with amino acids, such as L-cysteine, that are provided externally in a surrounding solution. Metal ions, such as Au(III), that can react in solution with the amino acid to produce one set of products under a given set of stoichiometric or concentration conditions, and a different set of products under a second set of conditions, were selected for incorporation into the aerogel. It was discovered that the course of the reaction can be changed by spatial confinement of the reaction domain in the aerogel. For example, in the case of Au(III) and L-cysteine, the Au(III) ions are confined in nanoscale domains, and when they are reacted with the amino acid, the nature of the reaction products is controlled by diffusion of the L-cysteine into the domains. Exploration of these and related phenomena will be presented.
Molecular Dynamics Studies of Surface Nucleation and Crystal Growth of Si on SiO2Substrates
Authors: Lee Byoung-Min , Baik Hong Koo , Kuranaga Takahide , Munetoh Shinji , Motooka Teruaki
Published: April 2011

Molecular dynamics (MD) simulations of atomistic processes of nucleation and crystal growth of silicon (Si) on SiO2substrate have been performed using the Tersoff potential based on a combination of Langevin and Newton equations. A new set of potential parameters was used to calculate the interatomic forces of Si and oxygen (O) atoms. It was found that the (111) plane of the Si nuclei formed at the surface was predominantly parallel to the surface of MD cell. The values surface energy for (100), (110), and (111) planes of Si at 77 K were calculated to be 2.27, 1.52, and 1.20 J/m2, respectively. This result suggests that, the nucleation leads to a preferred (111) orientation in the poly-Si thin film at the surface, driven by the lower surface energy.
Chemical bath deposition of nanocrystaline CdS and CdPbS layers and investigation of their photoconductivity
Authors: Rakovics Vilmos
Published: April 2011

The investigation of photoconductive properties of chemical bath deposited (CBD) cadmium sulphide (CdS) layers was the main objective of this work. For completeness, the CdS layers were characterized using X-ray diffraction, scanning electron microscopy, optical absorption, DC electrical conductivity, photoconductivity measurements. It has been found that the CdS layers grown are hexagonal with (002) preferential orientation. The n-type CdS materials show 100–200 nm clusters consisting of 10–20 nm size crystallites. The optical band gap is 2.42-2.52 eV, which shows a red-shift to 2.34 eV upon heat treatment. The effect of Cu doping and co-deposition of CdS with PbS were also investigated. Dark conductivity was increased after heat treatment of pure CdS layers, and decreased in case of Cu doped samples. Photoconductive response time of Cu doped CdS and Cd(Pb)S samples were smaller than the response time of pure CdS samples.
Surface Enhanced Raman Scattering on Physically Self-assembled Ag Nanorod Arrays
Authors: Suzuki Motofumi , Maekita Wataru , Wada Yoshinori , Nakajima Kaoru , Kimura Kenji , Fukuoka Takao , Mori Yasushige
Published: April 2011

We have established a process to fabricate Ag nanorod arrays with tunable morphology, hence tunable plasmonic properties. Based on a dynamic oblique deposition (DOD) technique, the nanorods are aligned in a way where their major axis is quasi-parallel. The aspect ratio of the nanorods is adjusted by choosing an appropriate DOD condition to show plasma resonance in the wavelength region around the Raman scattering at the excitation wavelength of 785 nm. The nanorod arrays thus tuned provide intense surface enhanced Raman scattering useful for practical applications to biochemical sensors.
Functionalization of 3-D Structures for Grafting of Biological Molecules
Authors: Oillic Cécile , Mur Pierre , Blanquet Elisabeth , Delapierre Guillaume , Vinet Françise , Billon Thierry
Published: April 2011

Even though most microarrays present good quality, accuracy and reliability, they are made on a planar surface structure, which neither enough increases the accessibility of the targets to the probes nor the loading capacity of the solid support. To achieve a high density of reactive functions, the use of a non-planar structure is investigated to increase the available surface area for grafting of biomolecules. We propose to build up a pseudo-three-dimensional silicon structure, covered with a specific oxide layer, and then functionalized, allowing to introduce covalent and stable bindings of amino-modified oligonucleotides probes on the reactive layer of the support. The performances of these supports after silanisation are investigated by means of hybridization experiments using complementary fluorescent labeled-oligonucleotides targets. Our results indicate that these novel surfaces provide a higher specific surface area for attaching biomolecules and higher accessibility of the targets, which will increase the density of biomolecules and hence, the sensitivity of the fluorescence signal in comparison to the results obtained with a planar surface structure.
Catalysis with Transition Metal Nanoparticles of Different Shapes
Authors: Narayanan Radha , El-Sayed Mostafa A.
Published: April 2011

Colloidal metal nanoparticles have a high surface-to-volume ratio which makes them potentially attractive catalysts. Furthermore, atoms located at different facets, edges, or corners could show different catalytic activity. For this reason, different shapes could have different catalytic activities. In addition, surface atoms are so active that there could be significant changes in their shape and size during the course of nanocatalysis. As a result, a thorough examination on the effect of the catalytic process on the shape and size of colloidal metal nanoparticles after catalysis is necessary to fully evaluate their use in catalytic processes.

In this paper, we briefly review our recent work on examining the shape dependence of nanocatalysis as well as the stability of platinum and palladium nanoparticles during the course of two reactions: the electron transfer reaction and the Suzuki reaction. It is found that nanocatalysis is indeed shape-dependent during the early stages of the electron transfer reaction. During the full course of the reaction, there are changes in the nanoparticle shape as well as changes in the activation energy that takes place. In the case of a relatively harsh reaction such as the Suzuki reaction, spherical palladium nanoparticles grow in size due to Ostwald ripening processes. Tetrahedral platinum nanoparticles catalyzing the Suzuki reaction transform into spherical shape and grow larger in size. We also conducted studies on the effect of individual reactants on the nanoparticle size and shape. In addition, the surface catalytic mechanisms of the reactions have been confirmed using spectroscopic tools such as FTIR and Raman spectroscopy. These kinds of studies will be very useful in the process of designing better nanocatalysts in the future.
Integration of Nanoparticles Into and Onto Optical Fiber Sensors
Authors: Dhawan A. , Muth J. F.
Published: April 2011

Metallic and semi-conducting nano-particles were incorporated into and on the surface of optical fibers to form sensors and other optoelectronic devices on standard telecommunications grade optical fibers. Optical fibers provide a macroscopic platform to exploit the wide range of functionality inherent in nanostructures and nano-particles. Several ways of forming sensitive and robust chemical sensors, based on plasmon resonances of metallic islands and nano-particles, were demonstrated. These nano-particles were formed on tip or surface of the optical fibers by thermal or plasma arc annealing of very thin (4 -12 nm) gold films, that were deposited by electron beam deposition and sputtering. Development of in-line optical fiber structures, involving single mode or multimode optical fibers fused to an arrangement of coreless and graded index fibers, was also carried out. This enabled light propagating in the core of the optical fiber to expand to the surface of the coreless fiber and to effectively interact with nano-particles on the surface and the environment. Metallic and semiconducting nano-particles were also incorporated inside an optical fiber matrix and this could enable us to effectively characterize novel materials and possibly form optical switches. Moreover, these optical fiber sensors and devices were integrated into textile structures to explore the possibility of formation of optoelectronic textiles.
Surface Characterization of Silicon Carbide Following Shallow Implantation of Palladium Ions
Authors: Muntele Claudiu I. , Sarkisov Sergey , Muntele Iulia , Ila Daryush
Published: April 2011

Silicon carbide is a promising wide-bandgap semiconductor intended for use in fabrication of high temperature, high power, and fast switching microelectronics components running without cooling. For hydrogen sensing applications, silicon carbide is generally used in conjunction with either palladium or platinum, both of them being good catalysts for hydrogen. Here we are reporting on the temperature-dependent surface morphology and depth profile modifications of Au, Ti, and W electrical contacts deposited on silicon carbide substrates implanted with 20 keV Pd ions.
Effects of Possible Spin-Spin Interactions on EPR spectra of Cu2+ exchanged Faujasite–X (I)
Authors: Kowenje Chrispin B. O. , Jones Barry R. , Kanyi Charles W.
Published: April 2011

The interpretation of the continuous wave electron paramagnetic resonance (CW-EPR) spectra of Cu2+ exchanged in Faujasite zeolite is not straightforward. Recent literature points to the role of both Cu2+ zeolite sites and Cu2+ relationship to lattice Al in determining the parameters of Cu2+ spin Hamiltonian. Our work shows that at low concentration, Cu2+ EPR signals show negligible spin-spin interactions. At higher Cu (II) concentrations, a third CW-EPR spectrum that has contributions from both the CW-EPR and the spin-spin interactions, appears.
Ion Modification for Improvement of Electrical Properties of Perovskite-based Ferroelectric Thin Films Fabricated by Chemical Solution Deposition Method
Authors: Uchida Hiroshi , Yasui Shintaro , Ueno Risako , Nakaki Hiroshi , Nishida Ken , Osada Minoru , Funakubo Hiroshi , Katoda Takashi , Koda Seiichiro
Published: April 2011

Ion modification for various perovskite-based ferroelectric thin films using rare-earth cations was attempted for improving the electrical properties. Strategy for controlling the electrical properties is mainly based on two concepts, that is, (i) substituting the volatile cations such as Pb2+ and Bi3+, and (ii) controlling the crystal anisotropy of perovskite unit cell. In this study, the influences of ion-modification conditions (i.e., amount, species and occupying site of substituent cations) on the electrical properties of perovskite-based ferroelectric films fabricated by a chemical solution deposition were investigated. Substituting volatile cations in simple-perovskite oxides, such Pb2+ in Pb(Zr,Ti)O3 and Bi3+ in BiFeO3, for the rare-earth cations like La3+ and Nd3+ reduced the leakage current density of these films due to suppressing the metal and / or oxygen vacancies, as well as in layered-perovskite oxides, such as Bi4Ti3O12 films [i.e., strategy (i)]. Also, crystal anisotropy of perovskite-based oxides could controlled by varying the species and the occupying site of substituent cations [i.e., strategy (ii)]; for example, the crystal anisotropy of Pb(Zr,Ti)O3 lattice was elongated by Ti- and Zr-site (B-site) substitution using rare-earth cations whose ionic radii locate on the smaller part of rare-earth series (such as Y3+, Dy3+), that resulted in enhancing the spontaneous polarization. We concluded that the strategy for controlling the electrical property mentioned in this study would be applicable for a various kind of perovskite-based ferroelectric films.