bluuebunny/crossref_metadata_2025 huggingface dataset:
Cell Biological and Biophysical Aspects of Lipid-mediated Gene Delivery
Authors: Rao N. Madhusudhana , Gopal Vijaya
Published: October 2006

Cationic lipids are conceptually and methodologically simple tools to deliver nucleic acids into the cells. Strategies based on cationic lipids are viable alternatives to viral vectors and are becoming increasingly popular owing to their minimal toxicity. The first-generation cationic lipids were built around the quaternary nitrogen primarily for binding and condensing DNA. A large number of lipids with variations in the hydrophobic and hydrophilic region were generated with excellent transfection efficiencies in vitro. These cationic lipids had reduced efficiencies when tested for gene delivery in vivo. Efforts in the last decade delineated the cell biological basis of the cationic lipid gene delivery to a significant detail. The application of techniques such as small angle X-ray spectroscopy (SAXS) and fluorescence microscopy, helped in linking the physical properties of lipid:DNA complex (lipoplex) with its intracellular fate. This biological knowledge has been incorporated in the design of the second-generation cationic lipids. Lipid-peptide conjugates (peptoids) are effective strategies to overcome the various cellular barriers along with the lipoplex formulations methodologies. In this context, cationic lipid-mediated gene delivery is considerably benefited by the methodologies of liposome-mediated drug delivery. Lipid mediated gene delivery has an intrinsic advantage of being a biomimetic platform on which considerable variations could be built to develop efficient in vivo gene delivery protocols.
Cloned Vero cell lines transfected with full‐length A‐segment or ORF1 cDNA sequence of IBDV
Authors: Ye Juxiu , Chen Qingxin , Zhou Jiyong , Li Lingyan
Published: October 2006

Recombinant plasmids containing the A‐segment or VP2/4/3 gene of infectious bursal disease virus (IBDV) were transfected into Vero cells. Monoclonal Vero cell lines were generated under G418 selection. Genomic (PCR/Southern blot) and transcriptional (RT‐PCR/Northern blot) analyses showed that one copy of A‐segment or VP2/4/3 or a partial gene of them was randomly and stably inserted into genomic DNA of Vero cells, and was able to transcribe corresponding mRNA. IFA/IPMA and Western blot analyses further confirmed that two of the monoclonal Vero cells with insertion of the A‐segment of IBDV into genomic DNA could stably express VP2, VP3 and VP5 proteins, one cell line only expressed VP2 protein, and three monoclonal Vero cell lines with genomic insertion of the VP2/4/3 gene of IBDV could express VP2, VP3 and VP4 proteins. Under G418 selection, integrated foreign genes can be inherited along with cellular genomic DNA during cell replications. Moreover, DNA fragmentation and caspase‐3 activity assays illustrated that cell apoptosis did not develop in monoclonal Vero cell lines expressing VP2 and VP5 proteins. The monoclonal IBDV gene‐inserted Vero cell lines developed in this study will facilitate better understanding of IBDV and other members of the Birnaviridae in an expression system that would enable investigation of virus‐host cell interactions on the cellular and molecular level.
Metabolic disturbances in chronic heart failure: A case for the “macho” approach with testosterone?!
Authors: Lainscak Mitja , Doehner Wolfram , Anker Stefan D.
Published: October 2006

Chronic heart failure (CHF) primarily affects the cardiovascular system. In addition, there is strong evidence that CHF is a complex metabolic disorder. Metabolic abnormalities include insulin resistance and lack of anabolic hormone activity. To date there have been few interventional trials targeting insulin sensitivity. A recent study suggests a link between testosterone therapy and improvements in insulin sensitivity, measured using the homeostatic model assessment (HOMA‐IR). We discuss this study in detail. Further studies are needed to substantiate this link and to generally explore the value of testosterone therapy in CHF patients.
Prescription of beta‐blockers in patients with advanced heart failure and preserved left ventricular ejection fraction. Clinical implications and survival
Authors: Dobre Daniela , van Veldhuisen Dirk J. , DeJongste Mike J.L. , Lucas Carolien , Cleuren Ger , Sanderman Robbert , Ranchor Adelita V. , Haaijer‐Ruskamp Flora M.
Published: October 2006

Background:

The effects of β‐blockers in patients with heart failure (HF) and preserved left ventricular ejection fraction (LVEF) are not well established.

Aims:

To assess the association between β‐blocker prescription at discharge and mortality in a cohort of patients with advanced HF and preserved LVEF.

Methods and results:

We prospectively studied a cohort of 443 patients with advanced HF and preserved LVEF (LVEF≥40%). Mean age was 78years, 56% female, 33% NYHA class IV. Overall, 227 patients (51%) had a β‐blocker prescribed at discharge. Mean duration of follow‐up was 25 (±18) months. Death (all cause) occurred in 40 patients (17.6%) who were receiving a β‐blocker at discharge and 73 patients (33.8%) who were not on a β‐blocker. In multivariate Cox analysis, including adjustment for propensity score, prescription of a β‐blocker remained associated with a 43% relative mortality risk reduction (HR 0.57, 95% CI 0.37 to 0.88, p=0.01).

Conclusions:

In this cohort of patients with advanced HF and preserved LVEF, prescription of a β‐blocker was associated with a significant mortality reduction. This beneficial effect of β‐blocker use needs to be further confirmed in prospective, randomised clinical trials.
Switching feedback mechanisms realize the dual role of MCIP in the regulation of calcineurin activity
Authors: Shin Sung-Young , Choo Sang-Mok , Kim Dongsan , Baek Song Joon , Wolkenhauer Olaf , Cho Kwang-Hyun
Published: October 2006

Calcineurin (CaN) assists T‐cell activation, growth and differentiation of skeletal and cardiac myocytes, memory, and apoptosis. It also activates transcription of the nuclear factor of activated T‐cells (NFAT) family including hypertrophic target genes. It has been reported that the modulatory calcineurin‐interacting protein (MCIP) inhibits the CaN activity and thereby reduces the hypertrophic response. However, it has been shown that MCIP facilitates or permits the hypertrophic response under some stress conditions such as isoproterenol infusion or pressure overload by transverse aortic constriction. As there is no direct experimental evidence that can explain these paradoxical phenomena, there has been a controversy concerning the functional role of MCIP in developing the hypertrophic response. It is therefore crucial to establish a hypothesis that can clearly explain these phenomena. Towards this end, we propose in this paper a hypothesis that is based on available experimental evidence as well as mathematical modeling and computer simulations. We hypothesize that there is a threshold in the nuclear NFAT concentration above which MCIP is switched on. Below this threshold, the inhibition of active CaN by MCIP is negligible, while the activated protein kinase increases the dissociation rate of the CaN/MCIP complex. This leads to an augmentation of active CaN. This mechanism realizes the positive effect (i.e., removing any negative feedback) of MCIP in the hypertrophic response. On the other hand, the over‐expression of active CaN increases nuclear NFAT to values above the threshold, while CaN is inhibited through binding of MCIP (expressed by the nuclear NFAT). This mechanism realizes the introduction of a negative feedback mechanism. To unravel this switching feedback mechanism, we have developed a mathematical model for which computer simulations are in agreement with the existing experimental data. The simulations demonstrate how the apparently paradoxical behavior can emerge as a result of cellular conditions.
Antisocial conduct: whose concern?
Authors: Wolff Sula
Published: October 2006

The differing perceptions of practitioners in child psychiatry and general psychiatry of antisocial behaviour are outlined, and an account is given of the change of attitudes towards deviancy that has taken place in the U.K. over the past twenty years.

Attention is drawn to the fact that constitutional as well as experiential factors contribute to the causation of delinquent conduct, and the characteristics of “schizoid” antisocial young people are described.

A plea is made for strengthening the links in training, research and practice between the subspecialties of psychiatry, and for a renewal of psychiatric interest in the sociopathies.
Adolescent coping style and behaviors: conceptualization and measurement
Authors: Patterson Joan M. , McCubbin Hamilton I.
Published: October 2006

The developmental tasks associated with adolescence pose a unique set of stressors and strains. Included in the normative tasks of adolescence are developing an identity, differentiating from the family while still staying connected, and fitting into a peer group. The adolescent's adaptation to these and other, often competing demands is achieved through the process of coping which involves cognitive and behavioral strategies directed at eliminating or reducing demands, redefining demands so as to make them more manageable, increasing resources for dealing with demands, and/or managing the tension which is felt as a result of experiencing demands. In this paper, individual coping theory and family stress theory are reviewed to provide a theoretical foundation for assessing adolescent coping. In addition, the development and testing of an adolescent self‐report coping inventory, Adolescent Coping Orientation for Problem Experiences (A‐COPE) is presented. Gender differences in coping style are presented and discussed. These coping patterns were validated against criterion indices of adolescents' use of cigarettes, liquor, and marijuana using data from a longitudinal study of 505 families with adolescents. The findings are discussed in terms of coping theory and measurement and in terms of adolescent development and substance use.
World Englishes in language testing: a call for research
Authors: Kim Hyun-Ju
Published: October 2006

Native speakers of English are a minority; there are far more non-native speakers in the world (cf. Kachru 1997, Pennycook 2001). In addition, native speakers' standard or ‘correct’ English, in terms of its grammar and phonology, is not always useful or even appropriate in international contexts (cf. Gisborne 2000, Newbrook 1998, Shim 1999). However, despite global changes in the use of the language, the norms for ENL (English as a Native Language) remain dominant, most notably for the assessment of oral proficiency. Yet it is a major deficiency in the use of international oral tests that the proficiency of non-native speakers is measured against unrealistic and irrelevant standards (cf. Jenkins, 1996). The present paper focuses on the need to revisit the testing of English oral proficiency for non-native speakers, bearing in mind that English is used for world-wide communication and that being able to understand one another (cf. McKay, 2002) is the most important goal.
Towards the acceptability of China English at home and abroad
Authors: Meilin Chen , Xiaoqiong Hu
Published: October 2006

Is a vast new variety of the language emerging? As the learning of English becomes a hot issue in China, linguists there and elsewhere have become interested in ‘China English’ – a relatively new concept. However, whether English as used in China has yet acquired the status of a distinct new variety of the language remains an open question. This paper reviews the acceptability of such an English, both at home and abroad, which has the potential (it is argued) to be accepted as a standard variety.
Living Next Door to Germany: Denmark and the German Problem
Authors: LAMMERS KARL CHRISTIAN
Published: October 2006

This article analyses Danish relations with the two German states. After 1949 Denmark found itself in a special position as the only West European country that was neighbour to both Germanys, having a land border with the Federal Republic and a sea border and important communications links with the German Democratic Republic. But Denmark recognised only the Federal Republic as the legitimate representative of Germany. Germany had historically constituted a serious problem for Denmark, and even in the after-war period Danish relations with its big neighbour were beset with problems. After 1955, when the minority question was settled and Denmark and the FRG were both members of NATO, relations with West Germany improved. Relations with the GDR were much more troubled because Denmark was to an extent forced to bow to West German interests, but could not ignore the existence of the East German neighbour state.
Lernstörungen
Authors: Hasselhorn Marcus , Schuchardt Kirsten
Published: October 2006

Zusammenfassung. Eine Sichtung vorliegender epidemiologischer Studien zur Prävalenz und Stabilität von Lese-Rechtschreibstörungen (LRS) und/oder Rechen- bzw. Mathematikstörungen (MS) gemäß der Definition von Lernstörungen in internationalen Klassifikationssystemen psychischer Störungen ergibt, dass LRS häufiger als MS auftritt, und dass die Prävalenz der Störungen zwischen Primarschulalter und jungem Erwachsenenalter abnimmt. Jungen haben ein erhöhtes LRS-Risiko, Mädchen ein erhöhtes Risiko zur kombinierten Lernstörung von LRS und MS. Die zeitliche Stabilität der Lernstörungen ist abhängig von den realisierten Fördermaßnahmen. Die Höhe der Prävalenz- und Stabilitätsschätzungen hängt ab von der Strenge der festgelegten Mindestkriterien und der curricularen Validität der verwendeten Leistungstests.
Die mittelfristige Entwicklung von Schülern mit Teilleistungsschwierigkeiten im Bereich der Lese- und Rechtschreibschwierigkeiten
Authors: Klicpera Christian , Schabmann Alfred , Gasteiger-Klicpera Barbara
Published: October 2006

Zusammenfassung. Die vorliegende Untersuchung geht dem Entwicklungsverlauf von Teilleistungsschwierigkeiten beim Lesen und Schreiben nach. In einer ländlichen Region in Niederösterreich wurden 600 unterschiedlich leistungsfähige Schüler von der ersten bis zum Ende der vierten Klassenstufe in mehreren Kohorten in ihren Lese- und Rechtschreibkompetenzen untersucht. Es wird geprüft, ob sich die verschiedenen Teilfertigkeiten im Verlauf des Schulbesuches auseinander entwickeln oder aber angleichen. Ferner wird der Leistungsverlauf von anfänglich schwachen und leistungsstärkeren Schülern untersucht. Dabei werden die Teilbereiche Lesesicherheit, Lesegeschwindigkeit, Rekodieren, Rechtschreibfähigkeit und unterschiedliche Fehlerarten beim Rechtschreiben sowie die Gesamtleistung betrachtet. Im Ergebnis zeigt sich, dass es während der ersten Schuljahre zu einer Annäherung von schwächeren und besseren Lesern kommt. Für die schwächeren Leser stellt das phonologische Rekodieren eine besondere Schwierigkeit dar. Ein Strukturgleichungsmodell weist der Lesegeschwindigkeit eine zentrale Rolle in der Entwicklung der Lesekompetenz zu.
Emotionale Ambivalenz, Körperbeschwerden, Depressivität und soziale Interaktion
Authors: Deighton Russell M. , Traue Harald C.
Published: October 2006

Zusammenfassung. Es wurde eine deutsche Version (AEQ-G18) des Ambivalence over Emotional Expressiveness Questionnaire (AEQ) von King und Emmons (1990) mit 18 Items erarbeitet. In drei voneinander unabhängigen Studien wurden korrelative Zusammenhänge zwischen emotionaler Ambivalenz, Krankheitsverhalten, Depressivität und sozialer Unterstützung untersucht. In der ersten Studie ergab die Faktorenanalyse der übersetzten AEQ-Items eine Faktorenstruktur mit zwei Faktoren: Kompetenzambivalenz und Effektambivalenz. Kompetenzambivalenz bezieht sich auf Zweifel und Unsicherheiten hinsichtlich der Fähigkeit positive Emotionen zu zeigen, und Effektambivalenz erfasst Befürchtungen über die Auswirkungen von negativ emotionaler Expressivität. In allen Studien (mit Stichproben aus der Allgemeinbevölkerung, von Studenten und von Patienten der Allgemeinmedizin) korrelierten Körpersymptome, Depressivität und soziale Unterstützung differenziert mit beiden Ambivalenzfaktoren des AEQ-G18. Diese Zusammenhänge schwächten sich jedoch nach Herauspartialisierung von Neurotizismus ab.
Ekman transport along the Galician coast (northwest Spain) calculated from forecasted winds
Authors: Gomez‐Gesteira Moncho , Moreira Camilo , Alvarez Ines , deCastro Maite
Published: October 2006

Ekman transport is studied close to the Galician coast by means of forecasted winds provided by METEOGALICIA from November 2001 to October 2004. Three different coastal zones are identified: western coast from Miño River to Cape Finisterre, middle coast from Cape Finisterre to Cape Ortegal and northern coast, from Cape Ortegal to Cape Peñas. In addition to existence of long‐term variations, the periodicity of the transport signal is characterized by an annual component (365 days), a seasonal fluctuation (50 to 80 days) and a timescale related to passing storms (15–20 days). Although the periodicity of the signal is similar at the three zones owing to external meteorological forcing, the Ekman transport is modulated by the presence of the coast, in such a way that seasonal patterns vary in intensity and direction along the coast. Thus the autumn‐winter pattern is characterized by high transport at the northern and middle coast, pointing landward perpendicular to the shoreline, and moderate values at the western coast, pointing landward and oblique to the shoreline. On the other hand, the spring‐summer pattern is characterized by high transport at the western coast, pointing seaward perpendicular to the shoreline. The same orientation is observed at the middle coast although with a lower magnitude. Finally, Ekman transport at the northern coast points landward and oblique to the shoreline. The different transport orientations are shown to be responsible for the upwelling probability variation along the coast.
Characteristics of 2–6 MeV electrons in the slot region and inner radiation belt
Authors: Zheng Yihua , Lui Anthony T. Y. , Li Xinlin , Fok Mei‐Ching
Published: October 2006

In this paper, the long‐term relativistic electron behavior in the often overlooked “slot” region and the inner belt was studied using the 2–6 MeV electron data from the SAMPEX satellite during 1992–2004. In particular, we investigated the penetration of the 2–6 MeV electrons to the slot region, their flux enhancement in the inner belt, and how these two processes are related to magnetospheric activity levels and solar wind parameters. It is found that the 2–6 MeV electron penetration (L < 3) usually takes place after those intense storms whose Dstmin is less than −130 nT. The penetration distance has a good correlation with the daily Dst minimum delayed by 3 days. However, it has little or no correlation with any of the individual daily solar wind parameters. A superposed epoch analysis shows a similar time lag between the peak values of the solar wind parameters/Dst index and the flux peak in the slot region at L = 2.5. Although the inner belt has fewer variations compared to the outer belt, it has its own response to different conditions. Analysis of the inner belt indicates that the flux enhancement is associated with high solar wind speed (>550 km s−1) as well as low solar wind density (∼4.4 cm−3). Either a couple of very extreme storms or recurrent intense storms will create conditions favorable for the MeV electron enhancement in the inner belt. However, without high‐speed solar wind on average, a series of intense storms alone are not sufficient to create inner belt electron flux enhancement.
Explosive photodissociation of methane induced by ultrafast intense laser
Authors: Kong Fanao , Luo Qi , Xu Huailiang , Sharifi Mehdi , Song Di , Chin See Leang
Published: October 2006

A new type of molecular fragmentation induced by femtosecond intense laser at the intensity of 2×1014W∕cm2 is reported. For the parent molecule of methane, ethylene, n-butane, and 1-butene, fluorescence from H (n=3→2), CH (AΔ2, BΣ−2, and CΣ+2→XΠ2), or C2 (dΠg3→aΠu3) is observed in the spectrum. It shows that the fragmentation is a universal property of neutral molecule in the intense laser field. Unlike breaking only one or two chemical bonds in conventional UV photodissociation, the fragmentation caused by the intense laser undergoes vigorous changes, breaking most of the bonds in the molecule, like an explosion. The fragments are neutral species and cannot be produced through Coulomb explosion of multiply charged ion. The laser power dependence of CH (A→X) emission of methane on a log-log scale has a slope of 10±1. The fragmentation is thus explained as multiple channel dissociation of the superexcited state of parent molecule, which is created by multiphoton excitation.
Ultrafast vectorial and scalar dynamics of ionic clusters: Azobenzene solvated by oxygen
Authors: Paik D. Hern , Baskin J. Spencer , Kim Nam Joon , Zewail Ahmed H.
Published: October 2006

The ultrafast dynamics of clusters of trans-azobenzene anion (A−) solvated by oxygen molecules was investigated using femtosecond time-resolved photoelectron spectroscopy. The time scale for stripping off all oxygen molecules from A− was determined by monitoring in real time the transient of the A− rise, following an 800nm excitation of A− (O2)n, where n=1–4. A careful analysis of the time-dependent photoelectron spectra strongly suggests that for n>1 a quasi-O4 core is formed and that the dissociation occurs by a bond cleavage between A− and conglomerated (O2)n rather than a stepwise evaporation of O2. With time and energy resolutions, we were able to capture the photoelectron signatures of transient species which instantaneously rise (<100fs) then decay. The transient species are assigned as charge-transfer complexes: A∙O2− for A−O2 and A∙O4−∙(O2)n−2 for A−(O2)n, where n=2–4. Subsequent to an ultrafast electron recombination, A− rises with two distinct time scales: a subpicosecond component reflecting a direct bond rupture of the A−-(O2)n nuclear coordinate and a slower component (1.6–36ps, increasing with n) attributed to an indirect channel exhibiting a quasistatistical behavior. The photodetachment transients exhibit a change in the transition dipole direction as a function of time delay. Rotational dephasing occurs on a time scale of 2–3ps, with a change in the sign of the transient anisotropy between A−O2 and the larger clusters. This behavior is a key indicator of an evolving cluster structure and is successfully modeled by calculations based on the structures and inertial motion of the parent clusters.
The calculated infrared spectrum of Cl−H2O using a new full dimensional ab initio potential surface and dipole moment surface
Authors: Rheinecker Jaime , Bowman Joel M.
Published: October 2006

We report a full dimensional, ab initio-based global potential energy surface (PES) and dipole moment surface for Cl−H2O. Both surfaces are symmetric with respect to interchange of the H atoms. The PES is a fit to thousands of electronic energies calculated using the coupled-cluster method [CCSD(T)] with a moderately large basis (aug-cc-pVTZ). Vibrational energies and wave functions are accurately obtained using MULTIMODE. The wave function and dipole moment surface are used to calculate and analyze the pure infrared spectrum at 0K which is compared with experiment. Vibrational energies and the infrared spectra for DOD and HOD/DOH are also presented.
A mass and time-of-flight spectroscopy study of the formation of clusters in free-jet expansions of normal D2
Authors: Ekinci Y. , Knuth E. L. , Toennies J. P.
Published: October 2006

The mass spectra in the range of 2(D+)–38(D19+)amu of clusters formed in a supersonic free-jet expansion of normal D2 are investigated as functions of source temperature in the range of 95–220K and of source pressure in the range of 10–120bars. For some of the small ion fragments, time-of-flight distributions are also measured. For large clusters (n>200) the intensities of the odd-numbered ion fragments exhibit magic numbers at D9+ and D15+ in accordance with previous experiments and calculations. The even-numbered ion fragments have much smaller intensities and exhibit new magic numbers at D10+ and D14+. For source conditions such that large clusters are formed, the intensities of the various different ion fragments are observed to saturate beyond a certain source pressure. At lower source pressures, where only small clusters are formed, the terminal mole fractions of the neutral dimers are analyzed in the light of available theories which take into account both the thermodynamics and the kinetics of the expansion. At higher source pressures and lower temperatures, where larger clusters are formed, the sizes of the neutral clusters are estimated using scaling laws and are found to be consistent with the mass spectra and measured time-of-flight distributions. By using a variety of techniques it has been possible to obtain reliable conclusions about the neutral cluster sizes for the present free-jet expansion conditions.
The time scale for electronic reorganization upon sudden ionization of the water and water-methanol hydrogen bonded dimers and of the weakly bound NO dimer
Authors: Remacle F. , Levine R. D.
Published: October 2006

When the valence molecular orbital is localized sudden ionization can cause the nascent hole to move rapidly even before any relaxation of the geometry occurs. Hydrogen bonded clusters offer suitable test systems where the hole is initially localized on one moiety. Computational studies are reported for the water dimer and water-methanol bimer. The local ionization potential of water is different in the methanol-water and water-methanol conformers and this difference is very clearly reflected in the dynamics of charge migration. For the NO dimer the results are that its structure is symmetric so that the two NO molecules are equivalent and do not exhibit the required localization. The role of symmetry is also evident in the charge propagation for holes created in different orbitals. Localization of the initial hole distribution even if absent in the bare molecule can still be induced by the intense electric field of a sudden photoionization. This effect is computationally studied for the NO dimer in the presence of a static electric field.
Diagnostics on the COBRA pulsed power generator
Authors: Shelkovenko T. A. , Chalenski D. A. , Chandler K. M. , Douglass J. D. , Greenly J. B. , Hammer D. A. , Kusse B. R. , McBride R. D. , Pikuz S. A.
Published: October 2006

The COBRA pulsed power generator has a variable current pulse wave form and amplitude (95–180ns rise time, up to 1MA peak current). It was designed to study wire array Z pinches and X pinches, including plasma formation, pinch implosion dynamics, and pinch plasma parameters as a function of current rise time. These loads have been studied using an extensive set of diagnostics with spatial and/or temporal resolution. The set of electrical diagnostics on the COBRA generator includes Rogowski coils to monitor the total load current and the current through individual return current posts, and there is also an inductive voltage monitor. A set of extreme ultraviolet and x-ray detectors is used to study the load radiation. Wire array and X pinch plasma formation and dynamics are studied using two-frame, point projection X-pinch x-ray imaging as well as with multiframe laser probing. Flat potassium acid phtalate crystal (KAP), convex, extreme luminosity imaging conical spectrograph, and focusing spectrograph with spatial resolution with mica crystal, pinhole cameras, and a camera with a slit and a step filter set (slip step-wedge camera) can be used in each pulse to monitor the x-ray emission from the X pinch(es) and arrays in several spectral bands.
Large-aperture switchable thin diffractive lens with interleaved electrode patterns
Authors: Li Guoqiang , Valley Pouria , Giridhar M. S. , Mathine David L. , Meredith Gerald , Haddock Joshua N. , Kippelen Bernard , Peyghambarian N.
Published: October 2006

The authors report on a high-performance large-aperture switchable diffractive lens using nematic liquid crystal that can be used as an adaptive eyewear. The odd- and even-numbered ring electrodes are separated in two layers, avoiding the gaps between the neighboring electrodes and allowing high diffraction efficiency. It is easier to avoid shorts between neighboring conductive electrodes and fabricate lenses with larger aperture and smaller feature size. With a four-level phase modulation, a 15mm aperture, 2dpt lens with small aberrations and diffraction efficiency of above 75% could be demonstrated with low operating voltages. The thickness of the liquid crystal is only 5μm. The lens switching time is about 180ms. The on and off states of the electrically controlled lens allows near and distance vision, respectively. The focusing power of the lens can be adjusted to be either positive or negative. This structure can be extended to higher-level phase modulation with even higher efficiencies.
Reexamining the 3-omega technique for thin film thermal characterization
Authors: Tong Tao , Majumdar Arun
Published: October 2006

The 3-omega method is widely used to measure thermal properties of thin films and interfaces. Generally, one-dimensional heat conduction across the film is assumed and the film capacitance is neglected. The change in the in-phase (real part) temperature response for the film-on-substrate case relative to the substrate-only case is, therefore, attributed to the sum of the bulk thermal resistance of the film and the thermal boundary resistance between the film and the substrate. Based on a rigorous and intuitive mathematical derivation, it is shown that this approach represents a limiting case, and that its use can cause significant errors in rather realistic situations when the underlying assumptions are not met. This article quantifies the error by introducing a new parameter called the ratio function R, which modifies the film thermal resistance and mathematically shows that it depends only on three dimensionless parameters that combine thermal properties and geometries of the film and the heated linewidth. A new data reduction scheme is suggested accordingly to determine the film thermal conductivity (cross-plane), anisotropic thermal conductivity ratio between the in-plane direction and the cross-plane direction, and the interface thermal conductance.
Towards the textile transistor: Assembly and characterization of an organic field effect transistor with a cylindrical geometry
Authors: Maccioni Maurizio , Orgiu Emanuele , Cosseddu Piero , Locci Simone , Bonfiglio Annalisa
Published: October 2006

Cylindrical organic field effect transistors have been obtained starting from a metallic fiber used in textile processes. The metal core of the yarn, covered with a thin polyimide layer, is the gate of the structure. A top-contact device can be obtained by depositing a layer of organic semiconductor followed by the deposition of source and drain top contacts, made by metals or conductive polymers, deposited by evaporation or soft lithography. Thanks to the flexibility of the structure and the low cost of technologies, this device is a meaningful step towards innovative applications of textile electronics.
Hot-core assembly in cryogenic D2 direct-drive spherical implosions
Authors: Smalyuk V. A. , Dumanis S. B. , Delettrez J. A. , Glebov V. Yu. , Meyerhofer D. D. , Regan S. P. , Sangster T. C. , Stoeckl C.
Published: October 2006

The temperature-density profiles of imploded cryogenic D2 capsules are inferred for a low-adiabat (α∼6) drive using a Monte Carlo technique described earlier [V. A. Smalyuk et al., Phys. Plasmas 12, 052706 (2005)]. The analysis has been improved by incorporating differential x-ray imaging using narrowband channels at ∼4.5 and ∼6.5keV. The inferred compression is significantly higher with the low-adiabat drive than with reported previously high-adiabat (α∼25) drive.
Transport study of a single bismuth nanowire fabricated by the silver and silicon nanowire shadow masks
Authors: Choi D. S. , Balandin A. A. , Leung M. S. , Stupian G. W. , Presser N. , Chung S. W. , Heath J. R. , Khitun A. , Wang K. L.
Published: October 2006

The authors have carried out measurements of the electrical conductivity of single bismuth nanowires fabricated by the low energy electron beam lithography using the silver/silicon nanowire shadow masks. The examined nanowires had cross-sectional dimensions of 40×30 and 40×50nm2. The chosen nanowire sizes had been slightly below the critical diameter D (∼50nm) at which a semimetal to semiconductor phase transition was predicted to occur. The results reveal a semiconductorlike temperature dependence of the electrical conductivity of a bismuth nanowire, which is strikingly different from that of the bulk bismuth.
Resonance energy transfer based on shallow and deep energy levels of biotin-polyethylene glycol/polyamine stabilized CdS quantum dots
Authors: Lü W. , Tokuhiro Y. , Umezu I. , Sugimura A. , Nagasaki Y.
Published: October 2006

Fluorescent resonance energy transfer between the poly(ethylene glycol)-b-poly(2-(N,N-dimethylamino)ethyl methacrylate) stabilized CdS quantum dots (QDs) and texas-red streptavidin was observed. We propose a four-state model to explain photoluminescence (PL) process of CdS QDs and suggest that there are two emission processes originated from shallow and deep trap energy levels corresponding to fast and slow components of PL decay, respectively. Energy transfer mechanism was discussed based on Dexter theory [J. Chem. Phys. 21, 863 (1953)] and the proposed four-state model. It is found that the energy transfer efficiency of deep energy level is higher than that of shallow energy level. The calculated distance between QD and texas red with the parameters of shallow energy level is the same with that of deep level, which indicates that the proposed model is reasonable for explaining the PL dynamics of CdS QDs.
Demonstration of net gain at 1550nm in an erbium-doped polymersingle mode rib waveguide
Authors: Le Quang Anh Quoc , Hierle Rolland , Zyss Joseph , Ledoux Isabelle , Cusmai Giuseppe , Costa Raffaella , Barberis Angelo , Pietralunga Silvia Maria
Published: October 2006

A polymer-based waveguide optical amplifier doped with Er3+ ions has been modeled, fabricated, and characterized. Propagation losses have been measured using both cutback and Fabry-Pérot methods, resulting in similar, reasonable loss values that do not exceed 1.31dBcm−1 at 1540nm. By accounting for overall propagation loss, a net gain of 1.34dB at 1540nm is demonstrated for a 1.6cm long single mode waveguide amplifier.
Nanocomposites with very large electro-optic effect and widely tunable refractive index
Authors: Chen Q. , Lin M. R. , Lee J. E. , Zhang Q. M. , Yin S.
Published: October 2006

A very large electro-optic effect has been observed in relaxor ferroelectric poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer. By adding a small amount of zinc sulfide nanoparticles, the refractive index of the nanocomposite can be tuned between 1.4 and 1.5 while retaining a large electro-optic effect and high transparency. Tunable long-period fiber gratings have been fabricated with the polymer nanocomposite as the second cladding, and a resonance wavelength shift of over 50nm has been achieved when electric field changed by 30V∕μm. This magnitude of shift corresponds to pure refractive index change of Δn∕n≈0.4% in the nanocomposite.
Atomic and electronic structure of the CoFeB∕MgO interface from first principles
Authors: Burton J. D. , Jaswal S. S. , Tsymbal E. Y. , Mryasov O. N. , Heinonen O. G.
Published: October 2006

First-principles calculations of the atomic and electronic structure of crystalline CoFeB∕MgO∕CoFeB magnetic tunnel junctions (MTJs) are performed to understand the effect of B on spin-dependent transport in these junctions. The authors find that it is energetically favorable for B atoms to reside at the crystalline CoFeB∕MgO interface rather than remain in the bulk of the crystalline CoFeB electrode. The presence of B at the interfaces is detrimental to tunneling magnetoresistance (TMR) because it significantly suppresses the majority-channel conductance through states of Δ1 symmetry. Preventing B segregation to the interfaces during annealing should result in an enhanced TMR in CoFeB∕MgO∕CoFeB MTJs.
Internal and external polarization memory loss in single semiconductor quantum dots
Authors: Wang Q. Q. , Muller A. , Bianucci P. , Shih C. K. , Cheng M. T. , Zhou H. J. , Han J. B.
Published: October 2006

By using nonlinear resonant optical control and polarized photoluminescence, the authors studied the intensity dependence of exciton spin relaxation and photoluminescence polarization in single self-assembled InGaAs quantum dots. Data from dots with different dipole moments reveal two distinctive channels for polarization memory loss: (i) an external pathway due to carrier escape and capture to and from the wetting layer that is responsible for memory loss increasing with intensity and (ii) an internal loss channel due to intrinsic spin relaxation. The values obtained rule out a universal freezing of exciton spin relaxation in single self-assembled quantum dots related to the wetting layer.
Real-time terahertz imaging over a standoff distance (>25meters)
Authors: Lee Alan W. M. , Qin Qi , Kumar Sushil , Williams Benjamin S. , Hu Qing , Reno John L.
Published: October 2006

The authors demonstrate the use of a terahertz quantum cascade laser (QCL) for real-time imaging in transmission mode at a standoff distance of 25meters. Lasing frequency was selected for optimum transmission within an atmospheric window at ∼4.9THz. Coarse frequency selection was made by design of the QCL gain medium. Finer selection (to within 0.1THz) was made by judicious choice of laser cavity length to adjust facet losses and therefore lasing threshold bias, in order to overlap the peak frequency of the Stark-shifted gain spectrum with the atmospheric window. Images are shown using an uncooled 320×240 microbolometer camera.
High resolution determination of ferromagnetic metallic limit in epitaxial La1−xCaxMnO3 films on NdGaO3
Authors: Sánchez D. , Hueso L. E. , Granja L. , Levy P. , Mathur N. D.
Published: October 2006

The physical properties of manganites depend strongly on sample morphology, probably due to strain. The authors investigate the influence of NdGaO3 substrates on the limit of the ferromagnetic-metallic phase field in La1−xCaxMnO3, doping with x=1% resolution. Films with x=0.40 show a metal-insulator transition, but the ferromagnetic volume fraction is half the spin aligned value. Films with x=0.41 are similar but the metal-insulator transition is not always seen. Films with 0.42⩽x⩽0.45 are insulating, and the magnetization is dramatically reduced. The observed phase boundary indicates where to search for enhanced phase separation effects that may be exploited in thin films and devices.
Anchoring and memory of the azimuthal nematic orientation
Authors: Pires David , Galerne Yves
Published: October 2006

The authors show that the azimuthal anchoring properties, strength and memory, of nematic liquid crystals on glass surfaces are intrinsically weak, contrary to what is generally asserted. They are, however, largely increased when adding residual impurities that further deposit onto the substrate, the polymers being more efficient than small molecules. The gliding of the easy axis, when submitted to a torque, may thus be significantly reduced, and consequently, the quality of the orientational memory may be considerably increased. This property is interesting since it allows one to replicate nonuniform alignment patterns by means of an imprinting method.
Influence of electron injection on the photoresponse of ZnO homojunction diodes
Authors: Lopatiuk-Tirpak O. , Chernyak L. , Mandalapu L. J. , Yang Z. , Liu J. L. , Gartsman Konstantin , Feldman Yishay , Dashevsky Zinovy
Published: October 2006

Forward bias electron injection into the p side of a p-n homojunction was shown to result in an improved response of the ZnO photodiodes. Injection of about 25C of charge yielded a nearly 2.5-fold increase of photocurrent at 350nm. This improvement was correlated with the increase of the diffusion length of minority electrons in p-type ZnO:Sb as determined by electron beam induced current measurements. It is suggested that the increase of the diffusion length is related to the carrier trapping on nonionized acceptor levels.
Low-frequency nonlinear magnetoelectric effects in a ferrite-piezoelectric multilayer
Authors: Kamentsev K. E. , Fetisov Y. K. , Srinivasan G.
Published: October 2006

Nonlinear magnetoelectric (ME) effects have been investigated in a multilayer of nickel zinc ferrite and lead zirconate titanate. The ME voltage has been measured under ac magnetic field amplitudes H of up to 1kOe over the frequency range f=1mHz–1Hz. Frequency doubling is observed for the ME voltage V generated across the multilayer and Fourier analysis of V shows harmonics of f. As H is increased or f is decreased, the shape of V is distorted and its magnitude decreases due to nonlinearity of the magnetostriction and the sample conductivity.
Biosynthesis of polyunsaturated fatty acids in lower eukaryotes
Authors: Uttaro Antonio D.
Published: October 2006

Polyunsaturated fatty acids have important structural roles in cell membranes. They are also intermediates in the synthesis of biologically active molecules such as eicosanoids, which mediate fever, inflammation, blood pressure and neurotransmission. Arachidonic and docosahexaenoic acids are essential components of brain tissues and, through their involvement in the development of neural and retinal functions, important dietary nutrients for neonatal babies. Lower eukaryotes are particularly rich in C20‐22 polyunsaturated fatty acids. Fungi and marine microalgae are currently used to produce nutraceutic oils. Other protists and algae are being studied because of the variability in their enzymes involved in polyunsaturated fatty acid biosynthesis. Such enzymes could be used as source for the production of transgenic organisms able to synthesize designed oils for human diet or, in the case of parasitic protozoa, they might be identified as putative chemotherapeutic targets. Polyunsaturated fatty acids can be synthesized by two different pathways: an anaerobic one, by using polyketide synthase related enzymes, and an aerobic one, which involves the action of elongases and oxygen dependent desaturases. Desaturases can be classified into three main types, depending on which of the consecutive steps of polyunsaturated fatty acid synthesis they are involved with. The enzymes may be specialized to act on: saturated substrates (type I); mono‐ and di‐unsaturated fatty acids by introducing additional double bonds at the methyl‐end site of the existing double bonds (type II); or the carboxy half ('front‐end') of polyunsaturated ones (type III). Type III desaturases require the alternating action of elongases. A description of the enzymes that have been isolated and functionally characterized is provided, in order to highlight the different pathways found in lower eukaryotes.
iubmb Life, 58: 563‐571, 2006
Concentration dependence of vibrational properties of bioprotectant/water mixtures by inelastic neutron scattering
Authors: Magazù S , Migliardo F , Ramirez-Cuesta A.J
Published: October 2006

Neutron scattering has been demonstrated to be a powerful tool for characterizing the structure and dynamics of biological molecules and for investigating the physical and chemical mechanisms of biophysical processes. The aim of the present work is to investigate by inelastic neutron scattering (INS) the vibrational behaviour of a class of bioprotectant systems, such as homologous disaccharides, trehalose, maltose and sucrose, in water mixtures. INS measurements have been performed on trehalose/H
2
O, maltose/H
2
O and sucrose/H
2
O mixtures at very low temperature as a function of concentration by using the thermal original spectrometer with cylindrical analyzers (TOSCA) spectrometer at the ISIS Facility (DRAL, UK).

The findings allow the analyses of the vibrational features of the INS spectra in order to study the effect of disaccharides on the H
2
O hydrogen-bonded tetrahedral network. The obtained neutron scattering findings point out that disaccharides, and in particular trehalose, have a destructuring effect on the water tetrahedral network, as emphasized by the analysis of the librational modes region from 50 to 130 meV energy transfer. On the other hand, the analysis of the bending modes region (130–225  meV) shows a locally ordered structure in the disaccharide/H
2
O mixtures.

Finally, the observed experimental evidences are linked to the different bioprotective effectiveness of disaccharides as a function of concentration.
Vaccination and the dynamics of immune evasion
Authors: Restif Olivier , Grenfell Bryan T
Published: October 2006

Vaccines exert strong selective pressures on pathogens, favouring the spread of antigenic variants. We propose a simple mathematical model to investigate the dynamics of a novel pathogenic strain that emerges in a population where a previous strain is maintained at low endemic level by a vaccine. We compare three methods to assess the ability of the novel strain to invade and persist: algebraic rate of invasion; deterministic dynamics; and stochastic dynamics. These three techniques provide complementary predictions on the fate of the system. In particular, we emphasize the importance of stochastic simulations, which account for the possibility of extinctions of either strain. More specifically, our model suggests that the probability of persistence of an invasive strain (i) can be minimized for intermediate levels of vaccine cross-protection (i.e. immune protection against the novel strain) and (ii) is lower if cross-immunity acts through a reduced infectious period rather than through reduced susceptibility.
An interface model of a graded three-dimensional anisotropic curved interphase
Authors: Benveniste Y , Baum G
Published: October 2006

A three-dimensional, generally curved, constant thickness interphase whose properties vary across its thickness is considered. This graded interphase is modelled by an interface that is located at its mid-surface and which comes now into direct contact with the media that were adjacent to it. The derivation is carried out in the setting of heat conduction, and appropriate jump conditions for the temperature and normal heat flux across the interface are derived, which characterize the interface model. The inhomogeneity of the interphase becomes a major motivation for its replacement by an interface. This representation is expected to simplify significantly the solution of boundary-value problems that involve thin inhomogeneous regions separating two media. Analytical solutions that are not available for a large class of graded interphases can become readily accessible with the derived interface model.