bluuebunny/crossref_metadata_2025 huggingface dataset:
Are Teachers Ready to Integrate Science Concepts into Secondary Agriculture Programs?
Authors: Scales Jason , Terry Jr. , Torres Robert M.
Published: February 2010

For the past two decades, the idea of integrating more science concepts into the secondary agriculture curriculum has gained support. The purpose of this study was to assess the confidence and competence of agriculture instructors to teach concepts related to science. The sample was derived from the population of agriculture instructors teaching in secondary schools of a selected Missouri. For this descriptive research, an instrument was developed to assess the instructors' perceived level of competence to teach selected grade level expectations (GLE) for science in grades 9 to 11. A second instrument, obtained from the American Board for Certification in Teacher Excellence, was used to assess the general biological science knowledge of the teachers. Agriculture instructors perceive that they are competent to teach nearly all of the selected concepts associated with the selected GLE. On the other hand, less than 10% of the teachers scored high enough on the examination to indicate proficient knowledge of biological science, raising questions regarding their competence to teach this subject matter.
Winning the War: A Historical Analysis of the FFA During World War II
Authors: Wolf Kattlyn J. , Connors James J.
Published: February 2010

The United States' participation in World War II affected millions of men, women, and children, both at home and around the world. The war effort also affected the Future Farmers of America (FFA). FFA members, agriculture teachers, and national FFA officers all volunteered to serve their country during the war. Local FFA chapters and individual FFA members joined with other citizens to support the war effort. The national convention of the FFA and local FFA chapter operations were affected during the war years. Thousands of former FFA members left their homes and farms to enlist in the armed forces. Many gave the last full measure of sacrifice, their own lives, to the call of liberty. The gallantry of several FFA members was recognized with military honors, media features or commemorated in song following the war. This historical study researched the activities of local FFA chapters, the national FFA organization, and individual FFA members during World War II. Historical events were documented with primary and secondary sources including books, magazines, personal letters, personal communications, and reports available from the National FFA Archives.
Alternative Synthesewege zum Ethylen
Authors: Behr A. , Kleyensteiber A. , Hartge U.
Published: February 2010

Ethylen ist der bedeutendste Baustein der industriellen organischen Chemie. Seine Folgechemie ist äußerst vielfältig und die aus Ethylen hergestellten Produkte sind ein ständiger Bestandteil unseres täglichen Lebens. Derzeit ist Ethylen fast ausschließlich über thermische Crackprozesse von Kohlenwasserstoffen zugänglich. Die immer stärker ins Bewusstsein tretende natürliche Begrenzung der Erdölvorräte und damit des Hauptrohstoffs für die Basischemikalie Ethylen hat das Interesse an alternativen Zugangsrouten neu belebt. Diese Übersicht betrachtet die bekannten Synthesewege und beschreibt einen Prozess zur Herstellung von Ethylen, der sich auch für kleinere Produktionsmaßstäbe eignet.
Distribution of kinetochore fragments during mitosis with unreplicated genomes
Authors: Johnson Mary Kathrine , Wise Dwayne A.
Published: February 2010

When hydroxyurea and caffeine are added to Chinese hamster ovary cells, the cells bypass the S‐phase checkpoint, and enter unscheduled mitosis. These cells build a morphologically normal spindle, and distribute unreplicated kinetochore fragments to daughters. We examined these cells and found that they undergo a full repertoire of mitotic stages, with the exception of anaphase B. Spindle elongation did not occur in these cells. When taxol was added, treated cells arrested indicating that microtubule turnover was necessary for kinetochore fragment separation. When released from taxol arrest, these cells divided. Finally, we determined that mitosis with unreplicated genome cells separated kinetochore fragments relatively equally. This mitosis is minimal, but still successful in kinetochore separation, which provides insight into the mechanism of anaphase movement. © 2010 Wiley‐Liss, Inc.
Altered renal proximal tubular endocytosis and histology in mice lacking myosin‐VI
Authors: Gotoh Nanami , Yan Qingshang , Du Zhaopeng , Biemesderfer Daniel , Kashgarian Michael , Mooseker Mark S. , Wang Tong
Published: February 2010

Myosin VI (Myo6) is an actin‐based molecular motor involved in clathrin‐mediated endocytosis that is highly expressed in the renal proximal tubule brush border. We investigated the renal physiological consequences of loss of Myo6 function by performing renal clearance and physiological measurements on Myo6 functional null Snell's waltzer (sv/sv) and control heterozygous (+/sv) mice. Sv/sv mice showed reduced body weight and elevated blood pressure compared with controls; no differences were observed for glomerular flow rate, urine volume, blood acid‐base parameters, and plasma concentrations and urinary excretions of Na+ and K+. To assess the integrity of endocytosis‐mediated protein absorption by the kidney, urinary albumin excretion was measured, and the proximal tubular uptake of intravenously injected endocytic marker horseradish peroxidase (HRP) was examined. Albumin excretion was increased nearly 4‐fold in sv/sv mice relative to controls. Conversely, HRP uptake was reduced and delayed in proximal tubule cells of the sv/sv kidney observed by electron microscopy at 5 and 30 min after injection. Consistent with impaired endocytosis, we also observed defects indicating alterations along the endocytic pathway in sv/sv proximal tubule cells: (1) decreased membrane association of the clathrin adaptor subunit, adaptin beta, and Disabled‐2 (Dab2) after sedimentation of renal homogenates and (2) reduced apical vacuole number. In addition, proximal tubular dilation and fibrosis, likely secondary effects of the loss of Myo6, were observed in sv/sv kidneys. These results indicate that Myo6 plays a key role in endocytosis‐mediated protein absorption in the mouse kidney proximal tubule. © 2010 Wiley‐Liss, Inc.
WASH and the Arp2/3 complex regulate endosome shape and trafficking
Authors: Duleh Steve N. , Welch Matthew D.
Published: February 2010

Activators of the Arp2/3 complex, termed nucleation‐promoting factors (NPFs), are required for the proper spatial and temporal control of actin assembly in cells. Mammalian cells express several NPFs, each of which functions in a distinct cellular process, including WASP and N‐WASP in phagocytosis and endocytosis, WAVE and JMY in cell migration, and WHAMM in ER‐to‐Golgi transport. Although another NPF called WASH was recently identified, the cellular localization and function of this protein were unclear. Here we demonstrated that human WASH alone potently activated the Arp2/3 complex in vitro and in cells, suggesting that the protein is not autoinhibited like N‐WASP, but is likely regulated by interacting proteins. In cells, WASH was associated with Rab5‐positive early endosomes and Rab11‐positive recycling endosomes that were enriched for actin filaments. Silencing of WASH or Arp2/3 complex expression by RNAi, or disruption of actin function by drug treatments, caused enlargement and elongation of endosomes. Intriguingly, WASH silencing, as well as actin disruption, delayed EGF transport to LAMP1‐positive late endosomes. These observations indicate that actin polymerization by WASH influences the shape and maturation of endosomes, and highlight a previously unrecognized role for WASH and the Arp2/3 complex in the degradative steps of endocytic trafficking. © 2010 Wiley‐Liss, Inc.
The hERG Potassium Channel and Drug Trapping: Insight from Docking Studies with Propafenone Derivatives
Authors: Thai Khac‐Minh , Windisch Andreas , Stork Daniela , Weinzinger Anna , Schiesaro Andrea , Guy Robert H. , Timin Eugen N. , Hering Steffen , Ecker Gerhard F.
Published: February 2010

The inner cavity of the hERG potassium ion channel can accommodate large, structurally diverse compounds that can be trapped in the channel by closure of the activation gate. A small set of propafenone derivatives was synthesized, and both use‐dependency and recovery from block were tested in order to gain insight into the behavior of these compounds with respect to trapping and non‐trapping. Ligand–protein docking into homology models of the closed and open state of the hERG channel provides the first evidence for the molecular basis of drug trapping.
Low‐cost, high‐throughput, automated counting of bacterial colonies
Authors: Clarke Matthew L. , Burton Robert L. , Hill A. Nayo , Litorja Maritoni , Nahm Moon H. , Hwang Jeeseong
Published: February 2010

Research involving bacterial pathogens often requires enumeration of bacteria colonies. Here, we present a low‐cost, high‐throughput colony counting system consisting of colony counting software and a consumer‐grade digital camera or document scanner. We demonstrate that this software, called “NICE” (NIST's Integrated Colony Enumerator), can count bacterial colonies as part of a high‐throughput multiplexed opsonophagocytic killing assay used to characterize pneumococcal vaccine efficacy. The results obtained with NICE correlate well with the results obtained from manual counting, with a mean difference of less than 3%. NICE is also rapid; it can count colonies from multiple reaction wells within minutes and export the results to a spreadsheet for data processing. As this program is freely available from NIST, NICE should be helpful in bacteria colony enumeration required in many microbiological studies, and in standardizing colony counting methods. Published 2010 Wiley‐Liss, Inc.
Enumeration and phenotypic assessment of human plasmacytoid and myeloid dendritic cells in whole blood
Authors: Chowdhury Ferdousi , Johnson Peter , Williams Anthony Peter
Published: February 2010

Traditionally, flow cytometry analysis of dendritic cells (DC) has followed a negative selection procedure, often limiting the characterization of individual DC subsets to enumeration. We demonstrate the development, evaluation, and clinical application of a novel 6 color/8 parameter flow cytometry panel to allow enumeration and monitoring of activation status of circulating human myeloid (MDC1) and plasmacytoid (PDC) dendritic cells in human whole blood. Enumeration showed a trend of greater numbers of MDC1s and PDCs being collected for fresh whole blood than frozen PBMCs, with this difference being statistically significant (P = 0.04) for unstimulated PDC enumeration. Intra‐assay variation had a coefficient of variation <10% and interassay results between operators showed good correlation (r > 0.95). Our results on fresh whole blood showed a significant up regulation of CD83 on both MDC1 and PDC at 4 h post Toll‐like ligand stimulus and this activity was comparable in frozen PBMC samples. Comparison for the late activation marker CCR7 showed a significant difference (P <0.05) in expression between fresh and frozen samples, precluding its use for batch analysis of frozen samples. In addition, the level of activation is dependent on the anticoagulant used for sample collection. For CD83 expression at 4 h both EDTA and lithium heparin samples are comparable for MDC1 and PDC populations. Whereas for CCR7 expression, lithium heparin is preferable as EDTA increases the background expression in PDC, preventing further functional assessments. We demonstrate the importance of establishing the kinetic profile of activation marker expression and the importance of evaluating sample collection tubes and sample type before application of novel cytometry panels to a clinical study. We have shown that this DC enumeration flow cytometry panel is a robust analysis system that allows the flexibility of including activation markers. © 2010 International Society for Advancement of Cytometry
Cloning and characterization of a new gene from the PAT protein family, in a marsupial, the stripe‐faced dunnart (Sminthopsis macroura)
Authors: Au Phil Chi Khang , Selwood Lynne , Familari Mary
Published: February 2010

Recent studies of PAT proteins in Drosophila and Xenopus have revealed significant roles for this family of proteins in the polarized transport of lipid droplets and maternal determinants during early embryogenesis. In mammals, PAT proteins are known to function mainly in lipid metabolism, yet research has yet to establish a role for PAT proteins in mammalian embryogenesis. Oocytes and early cleavage stages in Sminthopsis macroura show obvious polarized cytoplasmic distribution of organelles, somewhat similar to Drosophila and Xenopus, suggesting that a PAT protein may also be involved in S. macroura embryonic development. In the present study, we identified a new marsupial gene for PAT family proteins, DPAT, from S. macroura. Expression analyses by RT‐PCR and whole mount fluorescent in situ hybridization revealed that DPAT expression was specific to oocytes and cleavage stage conceptuses. Analysis of the localization of lipid droplets during S. macroura early embryonic development found a polarized distribution of lipid droplets at the two‐ and four‐cell stage, and an asymmetric enrichment in blastomeres on one side of conceptuses from two‐ to eight‐cell stage. Lipid droplets largely segregate to pluriblast cells at the 16‐cell stage, suggesting a role in pluriblast lineage allocation. Mol. Reprod. Dev. 77: 373–383, 2010. © 2010 Wiley‐Liss, Inc.
Divergent regulation of angiopoietin‐1 and ‐2, Tie‐2, and thrombospondin‐1 expression by estrogen in the baboon endometrium
Authors: Bonagura Thomas W. , Aberdeen Graham W. , Babischkin Jeffery S. , Koos Robert D. , Pepe Gerald J. , Albrecht Eugene D.
Published: February 2010

Estrogen has an important role in the reconstruction of a new vascular network in the endometrium during each menstrual cycle; however, the underlying mechanisms are incompletely understood. Angiopoietin‐1 (Ang‐1) promotes vessel assembly, whereas Ang‐2 and thrombospondin‐1 (TSP‐1) cause vessel breakdown. To determine the potential effect of estrogen on the expression of these angioregulatory factors in the endometrium, Ang‐1, Ang‐2, TSP‐1, and Tie‐2 receptor mRNA levels were assessed by real‐time reverse transcriptase polymerase chain reaction in glandular epithelial and stromal cells isolated from the endometrium of ovariectomized baboons treated acutely with estradiol. Corresponding protein expression was assessed by immunocytochemistry and the proximity ligation assay (PLA) during advancing stages of the baboon menstrual cycle. Serum estradiol levels in ovariectomized baboons were 400 pg/ml within 4–6 hr of estradiol treatment. Ang‐1 mRNA levels in glandular epithelial cells increased threefold (P < 0.01) within 4 hr of estradiol administration. In contrast, TSP‐1 mRNA levels decreased four‐ to fivefold (P < 0.01) in endometrial glandular epithelial and stromal cells 4–6 hr after estradiol, whereas Ang‐2 and Tie‐2 expression was unaltered. Immunostaining for Ang‐1 increased, TSP‐1 decreased, and Ang‐2 and Tie‐2 were unaltered in the endometrium during the secretory compared with the proliferative phase of the cycle. Endometrial Ang‐1 protein expression, quantified by PLA, increased 10‐fold (P < 0.05) between the early proliferative and late proliferative/mid‐secretory phases of the menstrual cycle in association with the rise in estrogen. In summary, estrogen induced a rapid, divergent, and cell‐specific change in expression of angiostimulatory and angioinhibitory growth factors in the endometrium of the nonhuman primate. Mol. Reprod. Dev. 77: 430–438, 2010. © 2010 Wiley‐Liss, Inc.
Biological modification strategies following marrow ablative, high‐dose chemotherapy (HDCT) with autologous hematopoietic stem cell rescue (AHSCR) for pediatric brain tumors
Authors: Zacharoulis Stergios , Chi Susan , Kadota Richard , Kieran Mark
Published: February 2010

Maintenance biology‐based therapy following HDCT/AHSCR in pediatric brain tumors has not been tested as yet. Failure of the HDCT/AHSCR might be due to tumor‐immunity dysregulation, reactivation of the angiogenic switch and other mechanisms. Angiogenesis has been shown to be reactivated following chemotherapy. The angiogenic factors engaged in this process in childhood brain tumors following HDCT/AHSCR have not been tested in the clinic. Metronomic chemotherapy has been found to be safe and angiogenesis inhibitors are currently tested in children. Other good possible candidates for clinical trials in this setting include retinoic acid and immunotherapy. Pediatr Blood Cancer 2010;54:654–656. © 2010 Wiley‐Liss, Inc.
Beschichtungen für Life Science
Authors: Bucher Volker , Nisch Wilfried
Published: February 2010

In der Life Science (Medizintechnik, Pharmaforschung, Biologie) werden die aus der Halbleitertechnologie bekannten Dünnschicht‐Verfahren und die dazugehörigen Mikrostrukturierungsverfahren erfolgreich eingesetzt. Nur sie ermöglichen die Funktionen der komplexen und oft miniaturisierten Produkte. Die Life Science ist ein stark wachsender Teil in der Mikrosystemtechnik, der viele Innovationen wie z.B. das Cochlear‐Implantat als Ersatz für das menschliche Ohr hervorgebracht hat oder kurz vor der Markteinführung stehende Produkte wie das Retina‐Implantat ermöglicht.

Seit den 60‐er Jahren des letzten Jahrhunderts ist der Einsatz von Polymeren („Kunststoffen”︁) in dieser Branche rasant gewachsen und stellt auch heute noch ein Wachstumsfeld für Kunststoff‐Verarbeiter dar. Gründe hierfür sind die preiswerte Herstellung und die einfache Sterilisierbarkeit von Kunststoff‐Einwegartikeln. Oft aber fehlt Kunststoffen eine bestimmte Oberflächenfunktionalität, die jedoch durch eine nachträgliche (funktionale) Beschichtung erreicht werden kann. Die Niederdruck‐Plasmatechnologie als Untergruppe der Vakuumbeschichtungstechnik ist hierfür eine sehr gut geeignete Methode, da die Bearbeitungstemperaturen im Bereich zwischen 20 °C – 60 °C liegen können. Aber auch für keramische und metallische Produkte aus der Life Science – Branche bietet sich eine Fülle von Beschichtungsmöglichkeiten an, z. B. Thrombose‐hemmende diamantähnliche Schichten auf implantierbaren Stents.

In diesem Übersichts‐Artikel sollen die Grundlagen der dafür nötigen Vakuumbeschichtungstechnik und Plasmabehandlung und in einer exemplarischen Zusammenschau einige Aspekte und Anwendungsbeispiele aus der Life Science beschrieben werden.
Innovative Technik für die Molekulardestillation
Authors: Bethge Daniel
Published: February 2010

Temperaturempfindliche Stoffgemische wie Öle, Fette, Pharmazeutika, Vitamine u.a. können mit Hilfe der Kurzweg‐ oder Molekulardestillation in einzelne Fraktionen getrennt werden. Wir stellen eine Neuentwicklung vor, die das Prinzip der kurzen (Brüden‐) Wege mit dem Plattenfallfilmverdampfer kombiniert. Der Betrieb einer Pilotanlage wird im Frühjahr 2010 aufgenommen.
C‐reactive Protein −717C>T Genetic Polymorphism Associates with Esophagectomy‐induced Stress Hyperglycemia
Authors: Motoyama Satoru , Miura Masatomo , Hinai Yudai , Maruyama Kiyotomi , Murata Katsuyuki , Ogawa Jun‐ichi
Published: February 2010

Background

Stress hyperglycemia refers to the transient hyperglycemia seen during illness and is usually restricted to patients without previous evidence of diabetes. The influence of genetics on surgery‐induced hyperglycemia remains only partially understood.

Methods

The study participants were Japanese patients treated for thoracic esophageal cancer with curative esophagectomy at Akita University Hospital between 2003 and 2007. We determined the associations between esophagectomy‐induced stress hyperglycemia (≥30 mg/dl increases in blood glucose during surgery) and genetic polymorphisms for C‐reactive protein (CRP), tumor necrosis factor (TNF)‐α, ‐β, interferon‐γ, transforming growth factor‐β1, interleukin (IL)‐1β, IL‐2, IL‐4, IL‐6, IL‐6 receptors, IL‐10, IL‐12β, adiponectin, and peroxisome proliferator‐activated receptor‐γ.

Results

In 28 (46%) patients, blood glucose levels increased more than 30 mg/dl during surgery. Among the genetic polymorphisms tested, CRP −717C>T was significantly associated with stress hyperglycemia during esophagectomy. Multivariate logistic regression revealed that patients with the CRP −717T/T genotype had a significantly greater risk of developing surgery‐induced hyperglycemia than those with the CRP −717C/T genotype. Stress hyperglycemia was also significantly associated with postoperative infectious complications and duration of intensive care unit stay.

Conclusions

It is suggested that CRP −717 C>T genetic polymorphism may be a predictive factor for stress hyperglycemia in patients receiving esophagectomy for thoracic esophageal cancer.
Palliative Resection in Noncurative Gastric Cancer Patients
Authors: Huang Kuo‐Hung , Wu Chew‐Wun , Fang Wen‐Liang , Chen Jen‐Hao , Lo Su‐Shun , Wang Ruei‐Fang , Li Anna Fen‐Yau
Published: February 2010

Background

Palliative resection for noncurable gastric cancer remains controversial, especially in the elderly. This retrospective study was designed to elucidate the clinicopathological factors and operative outcome in patients undergoing palliative gastric resection.

Methods

From January 1988 to December 2008, 365 patients received palliative gastrectomy while 151 underwent exploratory laparotomy or gastrojejunostomy for noncurative gastric cancer at the Department of Surgery, Taipei Veterans General Hospital. Among the 365 patients, 182 patients (Group A) were aged 70 or less and 183 patients (Group B) were older than 70 years of age. Clinicopathological characteristics and surgical morbidity and mortality were analyzed.

Results

The overall survival of patients who underwent resection was 10.2 months and that of patients without resection 4.48 months (p < 0.001). Compared to Group B, Group A patients were predominantly female (p < 0.001), had more advanced Borrmann‐type tumors (p = 0.004), more diffuse type of Lauren classification (p < 0.001), and poorer cell differentiation (p < 0.001). The median overall survival was 10.5 months in Group A and 9.7 months in Group B (p = 0.854). The surgical morbidity was significant higher if the patients had comorbidity (p = 0.028). Both surgical morbidity (13.8% vs. 26.8%, p = 0.028) and mortality (0.5% vs. 6.0%, p < 0.0001) were significantly higher in Group B.

Conclusions

Gastric cancer is less aggressive in the elderly. Palliative gastrectomy can be performed in both younger and older patients, but younger patients tolerate surgery better. More attention should be paid to the perioperative care of the elderly.
Modeling the Enceladus plume–plasma interaction
Authors: Fleshman B. L. , Delamere P. A. , Bagenal F.
Published: February 2010

We investigate the chemical interaction between Saturn's corotating plasma and Enceladus' volcanic plumes. We evolve a parcel of ambient plasma as it passes through a prescribed H2O plume using a physical chemistry model adapted for water‐group reactions. The flow field is assumed to be that of a plasma around an electrically‐conducting obstacle centered on Enceladus and aligned with Saturn's magnetic field, consistent with Cassini magnetometer data. We explore the effects on the physical chemistry due to: (1) a small population of hot electrons, (2) a plasma flow decelerated in response to the pickup of fresh ions, and (3) the source rate of neutral H2O. The model confirms that charge exchange dominates the local chemistry and that H3O+ dominates the water‐group composition downstream of the Enceladus plumes. We also find that the amount of fresh pickup ions depends heavily on both the neutral source strength and on the presence of a persistent population of hot electrons.
B3LYP calculations of cerium oxides
Authors: Kullgren Jolla , Castleton Christopher W. M. , Müller Carsten , Ramo David Muñoz , Hermansson Kersti
Published: February 2010

In this paper we evaluate the performance of density functional theory with the B3LYP functional for calculations on ceria (CeO2) and cerium sesquioxide (Ce2O3). We demonstrate that B3LYP is able to describe CeO2 and Ce2O3 reasonably well. When compared to other functionals, B3LYP performs slightly better than the hybrid functional PBE0 for the electronic properties but slightly worse for the structural properties, although neither performs as well as LDA+U(U=6 eV) or PBE+U(U=5 eV). We also make an extensive comparison of atomic basis sets suitable for periodic calculations of these cerium oxides. Here we conclude that there is currently only one type of cerium basis set available in the literature that is able to give a reasonable description of the electronic structure of both CeO2 and Ce2O3. These basis sets are based on a 28 electron effective core potential (ECP) and 30 electrons are attributed to the valence space of cerium. Basis sets based on 46 electron ECPs fail for these materials.
Surface changes on AlH3 during the hydrogen desorption
Authors: Kato Shunsuke , Bielmann Michael , Ikeda Kazutaka , Orimo Shin-ichi , Borgschulte Andreas , Züttel Andreas
Published: February 2010

Surface change of α-AlH3 during the hydrogen desorption was investigated by means of in situ x-ray photoelectron spectroscopy combined with thermal desorption spectroscopy. The surface of AlH3 covered by an oxide layer significantly changes upon hydrogen desorption and the hydrogen desorption rate increases remarkably. In this study, the role of the surface oxide layer on AlH3 in view of the hydrogen desorption kinetics was investigated. AlH3 only decomposes into Al and H2 at the free surface and not in the bulk. Therefore, a closed surface oxide layer prevents the thermodynamically unstable AlH3 from decomposition.
Contactless photoconductivity measurements on (Si) nanowires
Authors: Chepelianskii A. D. , Chiodi F. , Ferrier M. , Guéron S. , Rouviere E. , Bouchiat H.
Published: February 2010

Conducting nanowires possess remarkable physical properties unattainable in bulk materials. However our understanding of their transport properties is limited by the difficulty of connecting them electrically. In this letter we investigate phototransport in both bulk silicon and silicon nanowires using a superconducting multimode resonator operating at frequencies between 0.3 and 3 GHz. We find that whereas the bulk Si response is mainly dissipative, the nanowires exhibit a large dielectric polarizability. This technique is contactless and can be applied to other semiconducting nanowires and molecules.
Writer pole remanence of a tapered main pole head
Authors: Maeda Maki , Kobayashi Hiroki , Toda Junzo , Sato Yuichi , Eguchi Shin
Published: February 2010

We used a micromagnetic model to study the head remanence of a perpendicular tapered main pole head. To reduce the head pole tip remanence, a single magnetic domain structure forming a vortex state from the pole tip to the tapered region is preferred. A tapered main pole structure with a trailing gap depth less than about 30 nm and a tapered angle (TGθ) equal to about 30° improved the writing efficiency. This was achieved with a head field value more than 1.3 times higher and with a head field gradient about 1.15 times higher than that of the conventional structure. Moreover, the pole tip remanence was reduced to a value closer to that of the conventional structure. The reduction in the throat height had less effect on the reduction in the head remanence in the tapered head than in the conventional head. We also discuss both single pole heads and shielded heads.
The influence of Fermi level pinning/depinning on the Schottky barrier height and contact resistance in Ge/CoFeB and Ge/MgO/CoFeB structures
Authors: Lee Donkoun , Raghunathan Shyam , Wilson Robert J. , Nikonov Dmitri E. , Saraswat Krishna , Wang Shan X.
Published: February 2010

We demonstrated that an ultrathin MgO layer between CoFeB and Ge modulated the Schottky barrier heights and contact resistances of spin diodes. We confirmed that, surprisingly, an insulating MgO layer significantly decreased the Schottky barrier heights and contact resistances of spin diodes on N+Ge, opposite to the increase observed for P+Ge. A 0.5 nm thick MgO layer on N+Ge decreases the Schottky barrier height from 0.47 to 0.05 eV and lowers the minimum contact resistance 100-fold to 1.5×10−6 Ω m2. These results open a pathway for high efficient spin injection from ferromagnetic materials and semiconductors.
Interaction of vacuum ultraviolet excimer laser radiation with fused silica: II. Neutral atom and molecule emission
Authors: George Sharon R. , Langford S. C. , Dickinson J. T.
Published: February 2010

We report mass-resolved time-of-flight measurements of neutral Si, O, and SiO from ultraviolet-grade fused silica during pulsed 157-nm irradiation at fluences well below the threshold for optical breakdown. Although the emission intensities are strongly affected by thermal treatments that affect the density of strained bonds in the lattice, they are not consistently affected by mechanical treatments that alter the density of point defects, such as polishing and abrasion. We propose that the absorption of single 157 nm photons cleave strained bonds to produce defects that subsequently diffuse to the surface. There they react with dangling bonds to release neutral atoms and molecules. Hartree–Fock calculations on clusters containing these defects support the contention that defect interactions can yield emission. More direct emission by the photoelectronic excitation of antibonding chemical states is also supported.
Space charge limited electron emission from a Cu surface under ultrashort pulsed laser irradiation
Authors: Wendelen W. , Autrique D. , Bogaerts A.
Published: February 2010

In this theoretical study, the electron emission from a copper surface under ultrashort pulsed laser irradiation is investigated using a one-dimensional particle in cell model. Thermionic emission as well as multiphoton photoelectron emission were taken into account. The emitted electrons create a negative space charge above the target; consequently the generated electric field reduces the electron emission by several orders of magnitude. The simulations indicate that the space charge effect should be considered when investigating electron emission related phenomena in materials under ultrashort pulsed laser irradiation of metals.
Critical behavior of interacting monomers adsorbed on one-dimensional channels arranged in a triangular cross-sectional structure: Mixed interactions along and across the channels
Authors: Pasinetti P. M. , Romá F. , Riccardo J. L. , Ramirez-Pastor A. J.
Published: February 2010

Monte Carlo simulations and finite-size scaling analysis have been carried out to study the critical behavior in a submonolayer lattice-gas which mimics a nanoporous environment. In this model, the adsorbent is modeled as one-dimensional channels of equivalent adsorption sites arranged in a triangular cross-sectional structure. Two kinds of lateral interaction energies have been considered: (1) wL interaction energy between nearest-neighbor particles adsorbed along a single channel and (2) wT interaction energy between particles adsorbed across nearest-neighbor channels. We focus on the case of repulsive transverse (wT>0) and attractive longitudinal (wL<0) lateral interactions, where a rich variety of structural orderings are observed in the adlayer depending on the value of the parameters kBT/wT (being kB the Boltzmann constant) and wL/wT. The results reveal the existence of a first-order phase transition in the adlayer between a low-temperature “condensed” phase and a high-temperature “disordered” phase.
Bit patterned media based on block copolymer directed assembly with narrow magnetic switching field distribution
Authors: Hellwig O. , Bosworth J. K. , Dobisz E. , Kercher D. , Hauet T. , Zeltzer G. , Risner-Jamtgaard J. D. , Yaney D. , Ruiz R.
Published: February 2010

Electron-beam (E-beam) directed assembly, which combines the long-range phase and placement registration of e-beam lithography with the sharp dot size and spacing uniformity of block copolymer self assembly, is considered highly promising for fabricating templates that meet the tight magnetic specifications required for write synchronization in bit patterned media magnetic recording systems. In our study, we show that this approach also yields a narrower magnetic switching field distribution (SFD) than e-beam patterning or block copolymer self-assembly alone. We demonstrate that the pattern uniformity, i.e., island diameter and placement distributions are also important for achieving tight magnetic SFDs.
In situ synchrotron x-ray studies of strain and composition evolution during metal-organic chemical vapor deposition of InGaN
Authors: Richard M.-I. , Highland M. J. , Fister T. T. , Munkholm A. , Mei J. , Streiffer S. K. , Thompson Carol , Fuoss P. H. , Stephenson G. B.
Published: February 2010

Composition and strain inhomogeneities strongly affect the optoelectronic properties of InGaN but their origin has been unclear. Here we report real-time x-ray reciprocal space mapping that reveals the development of strain and composition distributions during metal-organic chemical vapor deposition of InxGa1−xN on GaN. Strong, correlated inhomogeneities of the strain state and In fraction x arise during growth in a manner consistent with models for instabilities driven by strain relaxation.
Overcharging and charge reversal in the electrical double layer around the point of zero charge
Authors: Guerrero-García G. Iván , González-Tovar Enrique , Chávez-Páez Martín , Lozada-Cassou Marcelo
Published: February 2010

The ionic adsorption around a weakly charged spherical colloid, immersed in size-asymmetric 1:1 and 2:2 salts, is studied. We use the primitive model (PM) of an electrolyte to perform Monte Carlo simulations as well as theoretical calculations by means of the hypernetted chain/mean spherical approximation (HNC/MSA) and the unequal-radius modified Gouy–Chapman (URMGC) integral equations. Structural quantities such as the radial distribution functions, the integrated charge, and the mean electrostatic potential are reported. Our Monte Carlo “experiments” evidence that near the point of zero charge, the smallest ionic species is preferentially adsorbed onto the macroparticle, independently of the sign of the charge carried by this tiniest electrolytic component, giving rise to the appearance of the phenomena of charge reversal (CR) and overcharging (OC). Accordingly, colloidal CR, due to an excessive attachment of counterions, is observed when the macroion is slightly charged and the coions are larger than the counterions. In the opposite situation, i.e., if the counterions are larger than the coions, the central macroion acquires additional like-charge (coions) and hence becomes “overcharged,” a feature theoretically predicted in the past [F. Jiménez-Ángeles and M. Lozada-Cassou, J. Phys. Chem. B 108, 7286 (2004)]. In other words, here we present the first simulation data on OC in the PM electrical double layer, showing that close to the point of zero charge, this novel effect surges as a consequence of the ionic size asymmetry. We also find that the HNC/MSA theory captures well the CR and OC phenomena exhibited by the computer experiments, especially as the macroion’s charge increases. On the contrary, even if URMGC also displays CR and OC, its predictions do not compare favorably with the Monte Carlo data, evidencing that the inclusion of hard-core correlations in Monte Carlo and HNC/MSA enhances and extends those effects. We explain our findings in terms of the energy-entropy balance. In the field of electrophoresis, it has been generally agreed that the charge of a colloid in motion is partially decreased by counterion adsorption. Depending on the location of the macroion’s slipping surface, the OC results of this paper could imply an increase in the expected electrophoretic mobility. These observations aware about the interpretation of electrokinetic measurements using the standard Poisson–Boltzmann approximation beyond its validity region.
Reduced initial degradation of bulk heterojunction organic solar cells by incorporation of stacked fullerene and lithium fluoride interlayers
Authors: Kawano Kenji , Adachi Chihaya
Published: February 2010

Reduced initial degradation of bulk heterojunction organic solar cells (OSCs) was achieved by inclusion of stacked fullerene (C60) and lithium fluoride interlayers. By inserting a 3 nm C60 layer and a 0.5 nm LiF layer between the photoactive layer and Al cathode in an OSC, the device lifetime calculated after an initial 8 h continuous illumination period was dramatically improved, with a decrease of only 5% in the power conversion efficiency. The 3 nm C60 layer forms a unique surface pattern of microscopic domes, and the combination of this layer with a 0.5 nm LiF layer formed an Ohmic-like contact between the photoactive layer and the Al cathode, resulting in a significant reduction in the degradation of the OSC.
A simple strategy to realize biomimetic surfaces with controlled anisotropic wetting
Authors: Wu Dong , Chen Qi-Dai , Yao Jia , Guan Yong-Chao , Wang Jian-Nan , Niu Li-Gang , Fang Hong-Hua , Sun Hong-Bo
Published: February 2010

The study of anisotropic wetting has become one of the most important research areas in biomimicry. However, realization of controlled anisotropic surfaces remains challenging. Here we investigated anisotropic wetting on grooves with different linewidth, period, and height fabricated by laser interference lithography and found that the anisotropy strongly depended on the height. The anisotropy significantly increased from 9° to 48° when the height was changed from 100 nm to 1.3 μm. This was interpreted by a thermodynamic model as a consequence of the increase of free energy barriers versus the height increase. According to the relationship, controlled anisotropic surfaces were rapidly realized by adjusting the grooves’ height that was simply accomplished by changing the resin thickness. Finally, the perpendicular contact angle was further enhanced to 131°±2° by surface modification, which was very close to 135°±3° of a common grass leaf.
Calibrating the single-wall carbon nanotube resonance Raman intensity by high resolution transmission electron microscopy for a spectroscopy-based diameter distribution determination
Authors: Pesce P. B. C. , Araujo P. T. , Nikolaev P. , Doorn S. K. , Hata K. , Saito R. , Dresselhaus M. S. , Jorio A.
Published: February 2010

We study a single-wall carbon nanotube (SWNT) sample grown by water-assisted chemical vapor deposition with both resonance Raman scattering (RRS) and high resolution transmission electron microscopy. High resolution transmission electron microscopy measurements of 395 SWNTs determined the diameter distribution of the sample, allowing us to calibrate an RRS radial breathing mode (RBM) map obtained with 51 laser excitation energies from 1.26 to 1.73 eV. Thus, we determined the diameter dependence of the RRS RBM cross-section, which in turn allows the determination of the diameter distribution of any SWNT sample by measuring the RBM Raman signal.
Demonstration of an air-slot mode-gap confined photonic crystal slab nanocavity with ultrasmall mode volumes
Authors: Gao Jie , McMillan James F. , Wu Ming-Chung , Zheng Jiangjun , Assefa Solomon , Wong Chee Wei
Published: February 2010

We demonstrate experimentally an air-slot mode-gap photonic crystal cavity with quality factor of 104 and modal volume of 0.02 cubic wavelengths, based on the design of an air-slot in a width-modulated line-defect in a photonic crystal slab. The origin of the high Q air-slot cavity mode is the mode-gap effect from the slotted PhCWG mode with negative dispersion. The high Q cavities with ultrasmall mode volume are important for applications such as cavity quantum electrodynamics, nonlinear optics, and optical sensing.
Enhanced optical power and low forward voltage of GaN-based light-emitting diodes with Ga-doped ZnO transparent conducting layer
Authors: Park Tae-Young , Choi Yong-Seok , Kang Jang-Won , Jeong Jae-Ho , Park Seong-Ju , Jeon Dong Min , Kim Je Won , Kim Yong Chun
Published: February 2010

Ga-doped ZnO (ZnO:Ga) films were grown by metalorganic chemical vapor deposition as transparent conducting layers for GaN light-emitting diodes (LEDs). The forward voltage of LEDs with ZnO:Ga was 3.3 V at 20 mA. The low forward voltage was attributed to the removal of a resistive ZnGa2O4 phase, decreased resistivity of ZnO:Ga films, and increased hole concentration in p-GaN by thermal annealing process. The light output power of LEDs with ZnO:Ga was increased by 25% at 20 mA compared to that of LEDs with Sn-doped indium oxide due to the enhanced transmittance and the increased hole concentration in p-GaN.
Electric potential and bending rigidity of a wormlike particle in electrolyte solution
Authors: Andreev V. A. , Victorov A. I.
Published: February 2010

Using the linearized Poisson–Boltzmann equation (LPB) we derive an asymptotic expansion for the electrostatic potential of charged torus immersed in solution of an electrolyte in the limit of high salinity and large major radius of the torus. The small parameter of this expansion is the ratio of the Debye length to the minor radius of the torus. We derive asymptotic expressions for the electrostatic free energy and for the electrostatic persistence length of a polyion of a finite thickness. We propose a simple interpolation formula, ξel=lB(σ¯0/e)2bκD[1+κD/(4b)], that gives the electrostatic persistence length in terms of the Debye length κD, the linear charge density (σ¯0/e), and the thickness of the polyion, 2b. This formula reproduces the exact results from the LPB theory in the limits of high and low salt concentrations. For the entire range of salinities, our formula is in excellent agreement with the numerical LPB results for wormlike particles of varying thickness. For particles of vanishing thickness, this formula reduces to the classical Odijk–Skolnick–Fixman expression.
Isomer identification and resolution in small gold clusters
Authors: Huang Wei , Pal Rhitankar , Wang Lei-Ming , Zeng Xiao Cheng , Wang Lai-Sheng
Published: February 2010

A variety of experimental techniques are used to resolve energetically close isomers of Au7− and Au8− by combining photoelectron spectroscopy and ab initio calculations. Two structurally distinct isomers are confirmed to exist in the cluster beam for both clusters. Populations of the different isomers in the cluster beam are tuned using Ar-tagging, O2-titration, and isoelectronic atom substitution by Cu and Ag. A new isomer structure is found for Au7−, which consists of a triangular Au6 unit with a dangling Au atom. Isomer-specific photoelectron spectra of Au8− are obtained from O2-titration experiment. The global minimum and low-lying structures of Au7−, Au8−, and MAun− (n=6,7; M=Ag,Cu) are obtained through basin-hopping global minimum searches. The results demonstrate that the combination of well-designed photoelectron spectroscopy experiments (including Ar-tagging, O2-titration, and isoelectronic substitution) and ab initio calculation is not only powerful for obtaining the electronic and atomic structures of size-selected clusters, but also valuable in resolving structurally and energetically close isomers of nanoclusters.
A translational nanoactuator based on carbon nanoscrolls on substrates
Authors: Shi Xinghua , Cheng Yuan , Pugno Nicola M. , Gao Huajian
Published: February 2010

Inspired by recent experimental studies on the fabrication of carbon nanoscrolls (CNSs) on solid substrates, we perform theoretical study and molecular dynamics simulations to investigate the translational rolling/unrolling of a CNS on rigid substrate. We show that a substrate-supported CNS can be controlled to roll forward and backward by tuning its interlayer interaction energy via an external field. The typical energy release rate per unit area of rolling for such controllable and reversible linear motion is estimated to be in the range of (−0.06)–0.08 nN/nm, indicating promising applications as actuators and motors in nanomechanical systems.
Mixed conduction and chemical diffusion in a Pb(Zr0.53,Ti0.47)O3 buried capacitor structure
Authors: Donnelly Niall J. , Randall Clive A.
Published: February 2010

Impedance spectroscopy is performed on a buried capacitor structure composed of a PZT-0.75% Nb ceramic with platinum electrodes. The ionic and electronic conductivities (σion,σelec) are extracted from the impedance spectra using an equivalent circuit based on the premise of mixed conduction. In the temperature range 500–700 °C, a change in local pO2 mainly affects σelec, suggesting that the samples are ionically compensated, i.e., [VO••]=[VPb″]. The chemical diffusion coefficient, D̃, is obtained by a conductivity relaxation technique assuming two-dimensional diffusion geometry. In comparison to BaTiO3, or SrTiO3, the chemical diffusivity is found to be relatively high, D̃=2.0×10−4 cm2 s−1 (700 °C, in air).
Reduced photocurrent lag using unipolar solid-state photoconductive detector structures: Application to stabilized n-i-p amorphous selenium
Authors: Goldan A. H. , Tousignant O. , Laperrière L. , Karim K. S.
Published: February 2010

Memory effects in direct detection solid-state photoconductors are attributed to interrupted charge transport by traps in the bulk and result in persistent photocurrent lag and ghosting. The identified sources for image lag following the cessation of x-ray exposure are the inhomogeneous electric field’s spatial distribution and the detrapping of the bulk space charge. This work shows that the latter is the dominant mechanism for the persistent photocurrent lag in stabilized n-i-p amorphous selenium photoconductors and proposes unipolar charge-sensing detector design for reducing image lag and improving the temporal performance of direct conversion x-ray imagers.
Evidence of substrate induced charge order quenching, insulator metal transition, and colossal magnetoresistance in polycrystalline Pr0.58Ca0.42MnO3 thin films
Authors: Agarwal Vasudha , Prasad R. , Singh M. P. , Siwach P. K. , Srivastava Amit , Fournier P. , Singh H. K.
Published: February 2010

We report the magnetoelectrical properties of polycrystalline Pr0.58Ca0.42MnO3 thin films (thickness∼300 nm) deposited on single crystal LaAlO3 (LAO) and SrTiO3 (STO) substrates. The films on LAO show charge ordering (CO) at TCO≈240 K, with a metamagnetic ground state akin to the cluster glass (CG). In PCMO/STO films the CO is quenched and enhanced magnetic moment in the CG state suggests stronger ferromagnetic component. The resistivity of the films on LAO and STO differ drastically, the former has temperature dependence typical to the CO state, while the later show thermal cycling dependent insulator-metal transition (IMT). The large hysteresis in the temperature dependent resistivity provides the evidence of cluster coexistence. The films on STO also exhibit colossal magnetoresistance (CMR∼91%) at moderate magnetic field (∼10 kOe). The CO quenching, IMT, and CMR are explained in terms of the substrate induced magnetoelectrical phase coexistence.
Fast thermally assisted switching at low current density in (Ga,Mn)As magnetic tunnel junctions
Authors: Li Zhen , Lagae Liesbet , Borghs Gustaaf , Mertens Robert , Van Roy Willem
Published: February 2010

(Ga,Mn)As based magnetic tunnel junctions have potential advantages compared to metal based junctions. In magnetic memory applications, spin-torque switching is the main approach to write information. In addition to the spin-torque effect, the current through the junction also increases the temperature, which can change the coercive fields and switch the magnetization of the (Ga,Mn)As layers in suitable bias fields. Using pulsed currents, we control the temperature increase and switch the junction states with critical current density as low as 3×103 A/cm2 for 100 ns pulses, or with pulses as short as 300 ps at current densities of 5×104 A/cm2.