bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors involved in correct analysis of intracardiac electrograms captured by Medtronic Inc. pacemakers during tachycardias
Authors: Takagaki Masaru , Ikeguchi Shigeru , Yamada Tomoyuki , Katsuyama Kazuhiko , Takeuchi Yuzo , Takeda Shinsaku , Kawata Yoshitaka , Harita Takeshi , Morii Akio , Nanba Hiroaki , Hasegawa Shinichi , Sukenari Shinichiro , Terada Hiroshi
Published: November 2012

Background

To thoroughly investigate the diagnostic information obtained by pacemakers, it is important that the stored intracardiac electrograms (EGMs) are analyzed. However, in Medtronic pacemakers, only a single intracardiac recording channel is available and thus EGM channel selection is critical.

Methods

The study population comprised 150 patients who underwent implantation of Medtronic's dual chamber pacemakers with a single intracardiac EGM memory channel. We first set the electrogram channel to “summed,” and the automatic EGM diagnosis during the tachycardia was compared with the manual analysis findings. When the results were not identical for the 2 methods, the atrial EGM (AEGM) and ventricular EGM channels were sequentially selected and the results of each EGM selection were compared to conclude which channel was more valuable for diagnosis of high‐rate episodes. The post‐ventricular atrial blanking (PVAB) period was adjusted to the shortest interval with a relevant margin to avoid any far‐field R wave over‐sensing.

Results

A total of 130 patients were eventually enrolled. High‐rate episodes were observed in 115/130 patients (88%). The results of the automated tachycardia diagnosis obtained using the “summed” EGM differed from those obtained manually in 43/115 patients (37%). Changing the intracardiac EGM channel from “summed” to “AEGM” enabled a much better manual diagnosis with intracardiac EGMs because of improved atrial potential sensing, clearer manifestation of atrial electrograms within the PVAB, and more prominent atrial electrograms fused with the ventricular potentials. The ventricular EGM channel was not as useful as the AEGM channel for tachycardia diagnosis.

Conclusions

In Medtronic pacemakers with single intracardiac EGM channel recording capability, AEGM is the most useful of the 3 EGM channel settings; PVAB should also be set to a much shorter value to achieve a more accurate automatic diagnosis.
Early‐stage splenic diffuse large B‐cell lymphoma is highly associated with hepatitis C virus infection
Authors: Yu Shan‐Chi , Lin Chung‐Wu
Published: November 2012

Splenic marginal zone lymphoma (SMZL) and splenic diffuse large B‐cell lymphoma (DLBCL) are the most common types of lymphomas involving the spleen. Geographic variation in hepatitis C virus (HCV) seroprevalence is characteristic of splenic lymphomas. In Italy, HCV seroprevalence was higher in patients with SMZL and splenic DLBCL than in patients with all types of lymphoma. In Japan, HCV seroprevalence was higher in patients with splenic DLBCL than in patients with all types of lymphoma; however, HCV seroprevalence in patients with SMZL was similar to that in patients with all types of lymphoma. In this study, clinicopathological data of 74 splenic lymphoma cases between 1988 and 2011 collected from the Department of Pathology at National Taiwan University Hospital were analyzed. Serology for HCV infection was available for 41 cases. Splenic DLBCL and SMZL accounted for 36% (n = 27) and 42% (n = 31) of splenic lymphomas, respectively. Microscopically, most cases of DLBCL (26/27) presented with circumscribed tumor and most cases of SMZL (28/31) presented with white pulp expansion. HCV seroprevalence in patients with DLBCL and SMZL was 44% and 10%, respectively (7/16 vs. 2/20, p = 0.020). The pattern identified in this study is closer to that in Japan than in Italy. HCV seroprevalence in patients with early‐stage (I/II) and late‐stage (III/IV) DLBCL was 100% and 10%, respectively (6/6 vs. 1/10, p < 0.001). Early‐stage DLBCL is clinically considered a form of primary splenic lymphoma rather than a systemic lymphoma with splenic involvement. High HCV seroprevalence in patients with early‐stage DLBCL suggests a role of HCV in the pathogenesis of primary DLBCL.
Preventive Exercise in Sports
Authors: Finnoff Jonathan T.
Published: November 2012

Sports injuries are common and can result in significant problems, such as pain, social isolation, depression, disability (temporary or permanent), loss of income, or loss of scholarship. Further, sports injuries can predispose the athlete to future injury or degenerative disorders, for example, osteoarthritis. Therefore, a preventive approach is paramount, and exercise can be used as an effective tool to prevent sports‐related injuries. This article describes the process by which successful injury prevention programs can be developed and implemented by using noncontact anterior cruciate ligament injury programs as an example. The knowledge gained from this information can be used in the future to assist in the creation of new injury prevention programs for other common sports injuries.
The dominance of the individual in intergroup relations research: Understanding social change requires psychological theories of collective and structural phenomena
Authors: Paluck Elizabeth Levy
Published: November 2012

Dixon et al. suggest that the psychological literature on intergroup relations should shift from theorizing “prejudice reduction” to “social change.” A focus on social change exposes the importance of psychological theories involving collective phenomena like social norms and institutions. Individuals' attitudes and emotions may follow, rather than cause, changes in social norms and institutional arrangements.
Echoing the call to move “beyond prejudice” in search of intergroup equality
Authors: Wright Stephen C. , Bitacola Lisa M.
Published: November 2012

We also critique the myopic focus on prejudice reduction, but we do not support the call for a reconceptualization of prejudice. Redefining key psychological constructs is unproductive. Also, we point to interpersonal dynamics in cross-group interaction as a key mechanism in the prejudice reduction/collective action paradox and point to solutions involving intrapersonal/interpersonal processes, as well as broader structural intergroup relations.
Are attitudes the problem, and do psychologists have the answer? Relational cognition underlies intergroup relations
Authors: Waldzus Sven , Schubert Thomas W. , Paladino Maria-Paola
Published: November 2012

The focus on negative attitudes toward other groups has led to a dichotomy between the prejudice reduction and the collective action approach. To solve the resulting problems identified by Dixon et al., we suggest analyzing the psychological processes underlying the construction of relationships (and their alternatives) between own and other groups.
The emergent modes of dementia activism
Authors: BARTLETT RUTH
Published: November 2012

After decades of silencing and discrimination, people with dementia are beginning to join forces, take action and campaign for social change. Drawing on data obtained from ‘activists’ with dementia using diary interview method and participant observation, this paper considers the emergent modes of dementia activism in the context of the social movement literature, and in particular, work emphasising the role of networks in health social movements. The study identified three emergent modes of dementia activism; these were the ‘protecting-self against decline’ mode, ‘(re) gaining respect’ mode, and ‘creating connections with other people with dementia’ mode. Taken together, these modes show how a sense of elapsing time pervades this form of activism. The investigation reinforces the contention that time is a dominated force that structures human motivation and goals. Furthermore, it raises the possibility that activism can protect against decline amongst people with dementia given the appropriate temporal space.
“To Immerse their Wives”: Communal Identity and the “Kahalishe” Mikveh of Altona
Authors: Kaplan Debra
Published: November 2012

On Sunday, the twelfth of Adar, March 2, 1681, theparnasim, the lay leaders of Altona, recorded an enactment in their communal logbook, thepinkas kehillah, regulating women's use of the localmikva'ot. Designating two privately-owned ritual baths as the only approved immersion locations for most of the women in the community, they decreed that defiance of this decree was to be punished with some of the most severe weapons in the arsenal of the communal leaders. Four years later, theparnasimreversed their policy and, with the permission of the community's rabbinic leadership, required the women to use only the newly builtkahalishe, or community,mikveh, banning the use of the two previously approvedmikva'ot. This article examines the construction and reconstruction of these policies regulating women's use ofmikva'ot, offering insight into how designated communal institutions were developed in the early modern period as well as how these institutions were used both to finance the community and to forge communal identity. Moreover, consideration of themikvehas a locus for building communal institutions and, in particular, communal identity, offers insight into how the growing bureaucratization of Jewish communal life in the early modern period affected women's lives.
“Their Eyes Shall Behold Strange Things”: Abraham Ben Elijah of Vilna encounters the Spirit of Mr. Buffon
Authors: Idelson-Shein Iris
Published: November 2012

The turn of the nineteenth century saw the publication of an abundance of travel narratives and texts in natural history written by maskilic Jews in Hebrew, Yiddish, and German in Hebrew characters. Several of these were maskilic translations of German children's books such as Georg Christian Raff'sNaturgeschichte für Kinderor Joachim Heinrich Campe's travel stories for children. Others were fragmentary translations of German science books such as Anton Friedrich Büsching'sNeue Erdbeschreibung. These translations were inspired by the maskilim's desire to acculturate their fellow Jews according to the standards of the European “high culture” of their time. The scientific, geographical, and philosophical knowledge offered by the source texts, combined with the rhetoric of voyage and discovery, as well as the stories of domesticating and acculturating “savage” peoples and wild animals, provided the maskilim with a compelling platform for disseminating maskilic knowledge, ideology, and goals.
Environmental factors influencing Pyrenophora semeniperda-caused seed mortality in Bromus tectorum
Authors: Finch Heather , Allen Phil S. , Meyer Susan E.
Published: November 2012

Temperature and water potential strongly influence seed dormancy status and germination of Bromus tectorum. As seeds of this plant can be killed by the ascomycete fungus Pyrenophora semeniperda, this study was conducted to learn how water potential and temperature influence mortality levels in this pathosystem. Separate experiments were conducted to determine: (1) if P. semeniperda can kill dormant or non-dormant seeds across a range of water potentials (0 to − 2 MPa) at constant temperature (20°C); and (2) how temperature (5–20°C) and duration at reduced water potentials (0–28 days) affect the outcome. When inoculated with the fungus at 20°C, all dormant seeds were killed, but fungal stromata appeared more quickly at higher water potentials. For non-dormant seeds, decreasing water potentials led to reduced germination and greater seed mortality. Results were similar at 10 and 15°C. Incubation at 5°C prevented stromatal development on both non-dormant and dormant seeds regardless of water potential, but when seeds were transferred to 20°C, dormant seeds evidenced high mortality. For non-dormant seeds, exposure to low water potential at 5°C resulted in secondary dormancy and increased seed mortality. Increasing incubation temperature, decreasing water potential and increasing duration at negative water potentials all led to increased mortality for non-dormant seeds. The results are consistent with field observations that pathogen-caused mortality is greatest when dormant seeds imbibe, or when non-dormant seeds experience prolonged or repeated exposure to low water potentials. We propose a conceptual model to explain the annual cycle of interaction in the Bromus tectorum–Pyrenophora semeniperda pathosystem.
Determinants of physical activity in young adults with tetralogy of Fallot
Authors: Buys Roselien , Budts Werner , Delecluse Christophe , Vanhees Luc
Published: November 2012

Background

Although sports participation is allowed to most adult patients with corrected tetralogy of Fallot, a reduced exercise tolerance and reduced perceived physical functioning is often present in these patients. We aimed to investigate daily physical activity in adults with tetralogy of Fallot and to investigate the underlying determinants of physical activity in daily life.

Methods

We studied 73 patients with tetralogy of Fallot (53 male; mean age 27.3 ± 7.9 years) who underwent echocardiography and cardiopulmonary exercise testing, and who completed questionnaires about physical activity and perceived health status. All variables were compared with data from a general population. Relationships were studied by Pearson or Spearman correlation coefficients with correction for multiple testing.

Results

Patients were significantly less active compared with the general population (p > 0.05), 55% of all patients were sedentary, 27% had an active or moderately active lifestyle, and 18% of the group had a vigorously active lifestyle. Peak oxygen uptake (71 ± 16%; p < 0.0001) was significantly reduced and related to reduced physical activity levels (r = 0.229; p = 0.017) and perceived physical functioning (r = 0.361; p = 0.002).

Conclusions

Adult patients with tetralogy of Fallot have a sedentary lifestyle and are less active than the general population. Inactivity significantly contributes to reduced exercise capacity, in addition to the impairment based on the cardiac condition. Moreover, reduced exercise capacity and the intensity of sports performed in daily life are related to perceived physical functioning. Individual patient counselling on physical activity might be a low-cost, high-benefit measure to be taken in this patient population.
Speech rhythm of monolingual and bilingual children at age 2;6: Cantonese and English
Authors: MOK PEGGY P. K.
Published: November 2012

Previous studies have showed that at age 3;0, monolingual children acquiring rhythmically different languages display distinct rhythmic patterns while the speech rhythm patterns of the languages of bilingual children are more similar. It is unclear whether the same observations can be found for younger children, at 2;6. This study compared five Cantonese–English simultaneous bilingual children with five monolingual children in each language using both rhythmic metrics and qualitative data on syllable structure complexity and lexical stress. Results show that while the speech rhythms of monolingual children are different at 2;6, the rhythmic patterns of bilingual children are less distinct.
Using rewards-based incentives to increase purchase of fruit and vegetables in lower-income households: design and start-up of a randomized trial
Authors: Phipps Etienne J , Wallace Samantha L , Stites Shana D , Uplinger Nadine , Brook Singletary S , Hunt Lacy , Axelrod Saul , Glanz Karen , Braitman Leonard E
Published: November 2012

Objective

To report the design and baseline results of a rewards-based incentive to promote purchase of fruit and vegetables by lower-income households.

Design

A four-phase randomized trial with wait-listed controls. In a pilot study, despite inadequate study coupon use, purchases of fresh fruit (but not vegetables) increased, but with little maintenance. In the present study, credits on the study store gift card replace paper coupons and a tapering phase is added. The primary outcome is the number of servings of fresh and frozen fruit and vegetables purchased per week.

Setting

A large full-service supermarket located in a predominantly minority community in Philadelphia, Pennsylvania, USA.

Subjects

Fifty-eight households, with at least one child living in the home.

Results

During the baseline period, households purchased an average of 3·7 servings of fresh vegetables and an average of less than 1 serving of frozen vegetables per week. Households purchased an average of 1·9 servings of fresh fruit per week, with little to no frozen fruit purchases. Overall, the range of fresh and frozen produce purchased during this pre-intervention period was limited.

Conclusions

At baseline, produce purchases were small and of limited variety. The study will contribute to understanding the impact of financial incentives on increasing the purchases of healthier foods by lower-income populations.
Using Cathodoluminescence Spectroscopy of Cretaceous Calcareous Microfossils to Distinguish Biogenic from Early-Diagenetic Calcite
Authors: Wendler Jens E. , Wendler Ines , Rose Timothy , Huber Brian T.
Published: November 2012

A comparative cathodoluminescence (CL) spectroscopic study of extraordinarily well-preserved versus diagenetically altered Turonian (∼92 Ma before present) calcitic and aragonitic microfossils was performed to document the cathodoluminescence characteristics of two common Cretaceous carbonate producers, foraminifera and calcareous dinoflagellates. Unaltered specimens reveal a conspicuous peak in the blue CL band at ∼400 nm that has rarely been previously reported for biogenic carbonates. We interpret this luminescence as an indicative feature of the primary bio-mineralized shells of calcareous dinoflagellates and foraminifera. Orange luminescence as the second important CL emission band (∼620 nm) in calcite generally increases with diagenetic cement overgrowth and recrystallization but can also be present in unaltered material. Thus, orange CL of biogenic calcite is not an unequivocal diagenetic indicator. Accordingly, spectroscopic investigation of both the ∼400 and ∼620 nm peaks represents a more objective criterion to evaluate the degree of diagenetic alteration. The ratio of relative intensities of the blue CL versus orange CL can provide a semiquantitative measure with relative intensity ratios blue:orange >2 occurring in the least diagenetically altered microfossils. Comparison of unaltered specimens of separate species reveals elemental differences that potentially indicate species-specific biomineralization or habitats.
Cathodoluminescence Microanalysis of Irradiated Microcrystalline and Nanocrystalline Samarium Doped BaFCl
Authors: Stevens-Kalceff Marion A. , Liu Zhiqiang , Riesen Hans
Published: November 2012

BaFCl:Sm3+ is an efficient photoluminescent storage phosphor for ionizing radiation. Cathodoluminescence (CL) microanalysis enables the Sm2+ and Sm3+ oxidation states of samarium doped BaFCl to be easily identified, provides information about electron-beam and X-ray induced modification of BaFCl:Sm, and enables the synthesis dependent spatial distribution of samarium dopants of <100 ppm concentration to be determined with sub-100 nm resolution at 295 K. CL spectroscopy of BaFCl:Sm particles reveals broad CL emissions at ∼360 and ∼500 nm associated with Vk(Cl−) and oxygen-vacancy defects in the BaFCl host lattice and fine structure CL emissions associated with major 4GJ → 6HJ (Sm3+) and 5DJ → 7FJ (Sm2+) transitions. CL microanalysis shows samarium dopants are uniformly distributed in conventional sintered microcrystalline BaFCl:Sm. In contrast, CL investigations reveal that for BaFCl:Sm nanoparticles, which have been prepared using a co-precipitation method, with greatly improved Sm3+ → Sm2+ conversion efficiency, the samarium dopants are concentrated near the particle surface resulting in a BaFCl:Sm3+ shell surrounding the BaFCl core, which is stable to energetic irradiation.
Mean Atomic Number Quantitative Assessment in Backscattered Electron Imaging
Authors: Sánchez E. , Deluigi M. Torres , Castellano G.
Published: November 2012

A method for obtaining quantitative mean atomic number images in a scanning electron microscope for different kinds of samples has been developed. The backscattered electron signal is monotonically increasing with the mean atomic number Z, and accordingly Z can be given as a function of the image gray levels. From results obtained from Monte Carlo simulations, an exponential function is fitted to convert the backscattered registered gray levels into a Z image map. Once this fitting was performed, the reproducibility of the Z determination was checked through the acquisition of backscattered electron images from metal and mineral standards. The developed method can be applied to any unknown sample, always controlling the experimental conditions, as shown here for a thin section of a rock in which several unknown mineral phases are present; the results obtained herein are compared to quantitative assessments performed with X-ray spectra from each mineral phase.
Strain accumulation controls failure of a plate boundary zone: Linking deformation of the Central Andes and lithosphere mechanics
Authors: Oncken O. , Boutelier D. , Dresen G. , Schemmann K.
Published: November 2012

We make use of observations on orogenic strain accumulation and deformation partitioning in the Central Andes to explore the backarc strength evolution at the lithospheric scale. In plan view, the Altiplano‐Puna plateaux experienced rapid initial increase of surface area undergoing active deformation during the Cenozoic. Beyond the maximum lateral extent reached around 10–15 Ma (40–50% of entire proto‐Andes undergoing deformation) at 10–20% total strain, rapid localization initiated at the eastern flank of the Altiplano (Inter‐ and Subandean thrust belt) but not at the Puna latitude. Localization was associated with a significant increase in bulk shortening rate. Average fault slip rates equally increased by an order of magnitude following a protracted period of stable average rates. Estimates of strength evolution based on force balance calculations and critical wedge analysis suggest significant backarc weakening driving this change after the Middle Miocene. Strain accumulation led to localization and weakening with development of a detachment propagating through crust and upper mantle. We find that lithosphere‐scale failure resulting from strain weakening beyond a critical strain threshold (c. 20%) and fault coalescence with formation of a weak detachment in shales (effective coefficient of friction < 0.1) plays a key role in the evolution of the Andes. Strain‐related lithosphere weakening appears to dominate over the impact of external forcing mechanisms, such as variations of plate convergence, mantle‐assisted processes, or erosion. Comparison of these orogen‐scale observations with experimental rock rheology indicates substantial similarity of deformation behavior with similar weakening thresholds across a wide range of scales.
P38 and JNK have opposing effects on persistence of in vivo leukocyte migration in zebrafish
Authors: Taylor Harriet B , Liepe Juliane , Barthen Charlotte , Bugeon Laurence , Huvet Maxime , Kirk Paul DW , Brown Simon B , Lamb Jonathan R , Stumpf Michael PH , Dallman Margaret J
Published: November 2012

The recruitment and migration of macrophages and neutrophils is an important process during the early stages of the innate immune system in response to acute injury. Transgenic pu.1:EGFP zebrafish permit the acquisition of leukocyte migration trajectories during inflammation. Currently, these high‐quality live‐imaging data are mainly analysed using general statistics, for example, cell velocity. Here, we present a spatio‐temporal analysis of the cell dynamics using transition matrices, which provide information of the type of cell migration. We find evidence that leukocytes exhibit types of migratory behaviour, which differ from previously described random walk processes. Dimethyl sulfoxide treatment decreased the level of persistence at early time points after wounding and ablated temporal dependencies observed in untreated embryos. We then use pharmacological inhibition of p38 and c‐Jun N‐terminal kinase mitogen‐activated protein kinases to determine their effects on in vivo leukocyte migration patterns and discuss how they modify the characteristics of the cell migration process. In particular, we find that their respective inhibition leads to decreased and increased levels of persistent motion in leukocytes following wounding. This example shows the high level of information content, which can be gained from live‐imaging data if appropriate statistical tools are used.
Pulsed laser deposition to synthesize the bridge structure of artificial nacre: Comparison of nano- and femtosecond lasers
Authors: Melaibari Ammar A. , Molian Pal
Published: November 2012

Nature offers inspiration to new adaptive technologies that allow us to build amazing shapes and structures such as nacre using synthetic materials. Consequently, we have designed a pulsed laser ablation manufacturing process involving thin film deposition and micro-machining to create hard/soft layered “brick-bridge-mortar” nacre of AlMgB14 (hard phase) with Ti (soft phase). In this paper, we report pulsed laser deposition (PLD) to mimic brick and bridge structures of natural nacre in AlMgB14. Particulate formation inherent in PLD is exploited to develop the bridge structure. Mechanical behavior analysis of the AlMgB14/Ti system revealed that the brick is to be 250 nm thick, 9 μm lateral dimensions while the bridge (particle) is to have a diameter of 500 nm for a performance equivalent to natural nacre. Both nanosecond (ns) and femtosecond (fs) pulsed lasers were employed for PLD in an iterative approach that involves varying pulse energy, pulse repetition rate, and target-to-substrate distance to achieve the desired brick and bridge characteristics. Scanning electron microscopy, x-ray photoelectron spectroscopy, and optical profilometer were used to evaluate the film thickness, particle size and density, stoichiometry, and surface roughness of thin films. Results indicated that both ns-pulsed and fs-pulsed lasers produce the desired nacre features. However, each laser may be chosen for different reasons: fs-pulsed laser is preferred for much shorter deposition time, better stoichiometry, uniform-sized particles, and uniform film thickness, while ns-pulsed laser is favored for industrial acceptance, reliability, ease of handling, and low cost.
Excess protons in mesoscopic water-acetone nanoclusters
Authors: Semino Rocío , Martí Jordi , Guàrdia Elvira , Laria Daniel
Published: November 2012

We carried out molecular dynamics simulation experiments to examine equilibrium and dynamical characteristics of the solvation of excess protons in mesoscopic, [m:n] binary polar clusters comprising m = 50 water molecules and n = 6, 25, and 100 acetone molecules. Contrasting from what is found in conventional macroscopic phases, the characteristics of the proton solvation are dictated, to a large extent, by the nature of the concentration fluctuations prevailing within the clusters. At low acetone contents, the overall cluster morphology corresponds to a segregated aqueous nucleus coated by an external aprotic phase. Under these circumstances, the proton remains localized at the surface of the water core, in a region locally deprived from acetone molecules. At higher acetone concentrations, we found clear evidence of the onset of the mixing process. The cluster structures present aqueous domains with irregular shape, fully embedded within the acetone phase. Still, the proton remains coordinated to the aqueous phase, with its closest solvation shell composed exclusively by three water molecules. As the relative concentration of acetone increases, the time scales characterizing proton transfer events between neighboring water molecules show considerable retardations, stretching into the nanosecond time domain already for n ∼ 25. In water-rich aggregates, and similarly to what is found in the bulk, proton transfers are controlled by acetone/water exchange processes taking place at the second solvation shell of the proton. As a distinctive feature of the transfer mechanism, translocation pathways also include diffusive motions of the proton from the surface down into inner regions of the underlying water domain.
Multi-particle states of semiconductor hexagonal rings: Artificial benzene
Authors: Ballester Ana , Planelles Josep , Bertoni Andrea
Published: November 2012

We present a theoretical and numerical investigation of correlated multi-electron states of hexagonal semiconductor rings. Both single-particle and correlated states show localization patterns in the six corners and energy spectra degeneracies corresponding to a hexagonal benzene ring. Thus, our results can aid the interpretation of energy-loss or near-field experiments that, in turn, shed light on the nature of molecular few-particle orbitals of artificial benzene. Surprisingly, we find that charges get more localized in the corners as the number of electrons increases, up to six, this indicating the deficiency of a picture based on orbitals delocalized on the whole ring. We also expose the presence of several spin-correlated states and the effect of an asymmetry of the system.
Binary and ternary recombination of ${\rm D}_3^+$D3+ ions at 80–130 K: Application of laser absorption spectroscopy
Authors: Dohnal Petr , Hejduk Michal , Rubovič Peter , Varju Jozef , Roučka Štěpán , Plašil Radek , Glosík Juraj
Published: November 2012

Recombination of ${\rm D}_3^+$D3+ ions with electrons at low temperatures (80–130 K) was studied using spectroscopic determination of ${\rm D}_3^+$D3+ ions density in afterglow plasmas. The use of cavity ring-down absorption spectroscopy enabled an in situ determination of the abundances of the ions in plasma and the translational and the rotational temperatures of the recombining ions. Two near infrared transitions at (5792.70 ± 0.01) cm−1 and at (5793.90 ± 0.01) cm−1 were used to probe the number densities of the lowest ortho state and of one higher lying rotational state of the vibrational ground state of ${\rm D}_3^+$D3+ ion. The results show that ${\rm D}_3^+$D3+ recombination with electrons consists of the binary and the third-body (helium) assisted process. The obtained binary recombination rate coefficients are in agreement with a recent theoretical prediction for electron-ion plasma in thermodynamic equilibrium with αbin(80 K) = (9.2 ± 2.0) × 10−8 cm3 s−1. The measured helium assisted ternary rate coefficients KHe are in agreement with our previously measured flowing afterglow data giving a value of KHe(80 K) = (1.2 ± 0.3) × 10−25 cm6 s−1.
Impact of grating spacing and electric field on real time updatable holographic recording in nanoscale ZnSe film assisted liquid crystal cells
Authors: Zhao Hua , Lian Chao , Huang Feng , Xue Tingyu , Sun Xiudong , Zou Yingyin K. , Zhang Jingwen
Published: November 2012

Real time updatable holographic recording was demonstrated in C60 doped 4,4′-n-pentylcyanobiphenyl liquid crystal cells made of indium tin oxide glass plates covered with nanoscale ZnSe thin films, without aligning layers required. Possible governing mechanism behind the associated findings was proposed and supported experiments were presented, based on the excellent charge carrier generation/migration in the ZnSe and liquid crystal layers and near the ZnSe/liquid crystal interfaces.
Structure and optical properties of a-plane ZnO/Zn0.9Mg0.1O multiple quantum wells grown on r-plane sapphire substrates by pulsed laser deposition
Authors: Li Y. , Pan X. H. , Zhang Y. Z. , He H. P. , Jiang J. , Huang J. Y. , Ye C. L. , Ye Z. Z.
Published: November 2012

A series of 10-period ZnO/Zn0.9Mg0.1O multiple quantum wells (MQWs) with well widths varying from 2.2 to 5.6 nm have been grown on r-plane sapphire substrates by pulsed laser deposition. A good periodic structure with clear interfaces was observed by transmission electron microscopy. In a-plane ZnO/Zn0.9Mg0.1O MQWs, the luminescence was dominated by localized exciton emissions at low temperatures, while the free exciton (FE) transition was dominating emissions at temperatures above 100 K. The thermal quenching behavior of exciton emission has been analyzed. A rate equation assuming two nonradiative recombination channels is used to describe the quenching of the transitions observed. Moreover, the FE emission energy in the MQWs shows a systematic blueshift with decreasing well width, which is consistent with a quantum confinement effect.
A frequency-bandgap waveguide controlled with metafilms composed of cubic particles
Authors: Kim Sung , Holloway Christopher L. , Kumley Kendra L. , Janezic Michael D. , Baker-Jarvis James , Kuester Edward F.
Published: November 2012

We describe, both numerically and experimentally, a rectangular S-band waveguide having electromagnetic bandgap properties (stopbands) controlled with sheets of metafilms composed of ceramic particles. Metafilms composed of TiO2 ceramic cubes are fabricated for the waveguide loading, and 2, 3, or 4 layers are inserted. The dispersion analysis estimates the frequency ranges of the stopbands to be 2.49−2.66 GHz, 3.34−3.40 GHz, and 3.66−3.79 GHz. The field patterns at a resonance around the stopband are presented and discussed. We find that more metafilm layers provide stronger attenuation, broader stopbands, and steeper roll-offs and that the effective refractive index extracted from the reflection and transmission coefficients explains those characteristics adequately.
Mapping Greenland’s mass loss in space and time
Authors: Harig Christopher , Simons Frederik J.
Published: November 2012

The melting of polar ice sheets is a major contributor to global sea-level rise. Early estimates of the mass lost from the Greenland ice cap, based on satellite gravity data collected by the Gravity Recovery and Climate Experiment, have widely varied. Although the continentally and decadally averaged estimated trends have now more or less converged, to this date, there has been little clarity on the detailed spatial distribution of Greenland’s mass loss and how the geographical pattern has varied on relatively shorter time scales. Here, we present a spatially and temporally resolved estimation of the ice mass change over Greenland between April of 2002 and August of 2011. Although the total mass loss trend has remained linear, actively changing areas of mass loss were concentrated on the southeastern and northwestern coasts, with ice mass in the center of Greenland steadily increasing over the decade.
Perceptual convergence of multi-component mixtures in olfaction implies an olfactory white
Authors: Weiss Tali , Snitz Kobi , Yablonka Adi , Khan Rehan M. , Gafsou Danyel , Schneidman Elad , Sobel Noam
Published: November 2012

In vision, two mixtures, each containing an independent set of many different wavelengths, may produce a common color percept termed “white.” In audition, two mixtures, each containing an independent set of many different frequencies, may produce a common perceptual hum termed “white noise.” Visual and auditory whites emerge upon two conditions: when the mixture components span stimulus space, and when they are of equal intensity. We hypothesized that if we apply these same conditions to odorant mixtures, “whiteness” may emerge in olfaction as well. We selected 86 molecules that span olfactory stimulus space and individually diluted them to a point of about equal intensity. We then prepared various odorant mixtures, each containing various numbers of molecular components, and asked human participants to rate the perceptual similarity of such mixture pairs. We found that as we increased the number of nonoverlapping, equal-intensity components in odorant mixtures, the mixtures became more similar to each other, despite not having a single component in common. With ∼30 components, most mixtures smelled alike. After participants were acquainted with a novel, arbitrarily named mixture of ∼30 equal-intensity components, they later applied this name more readily to other novel mixtures of ∼30 equal-intensity components spanning stimulus space, but not to mixtures containing fewer components or to mixtures that did not span stimulus space. We conclude that a common olfactory percept, “olfactory white,” is associated with mixtures of ∼30 or more equal-intensity components that span stimulus space, implying that olfactory representations are of features of molecules rather than of molecular identity.
Inhibition of Glutamate Carboxypeptidase II (GCPII) activity as a treatment for cognitive impairment in multiple sclerosis
Authors: Rahn Kristen A. , Watkins Crystal C. , Alt Jesse , Rais Rana , Stathis Marigo , Grishkan Inna , Crainiceau Ciprian M. , Pomper Martin G. , Rojas Camilo , Pletnikov Mikhail V. , Calabresi Peter A. , Brandt Jason , Barker Peter B. , Slusher Barbara S. , Kaplin Adam I.
Published: November 2012

Half of all patients with multiple sclerosis (MS) experience cognitive impairment, for which there is no pharmacological treatment. Using magnetic resonance spectroscopy (MRS), we examined metabolic changes in the hippocampi of MS patients, compared the findings to performance on a neurocognitive test battery, and found that
N
-acetylaspartylglutamate (NAAG) concentration correlated with cognitive functioning. Specifically, MS patients with cognitive impairment had low hippocampal NAAG levels, whereas those with normal cognition demonstrated higher levels. We then evaluated glutamate carboxypeptidase II (GCPII) inhibitors, known to increase brain NAAG levels, on cognition in the experimental autoimmune encephalomyelitis (EAE) model of MS. Whereas GCPII inhibitor administration did not affect physical disabilities, it increased brain NAAG levels and dramatically improved learning and memory test performance compared with vehicle-treated EAE mice. These data suggest that NAAG is a unique biomarker for cognitive function in MS and that inhibition of GCPII might be a unique therapeutic strategy for recovery of cognitive function.
Stochastic geometry and topology of non-Gaussian fields
Authors: Beuman Thomas H. , Turner Ari M. , Vitelli Vincenzo
Published: November 2012

Gaussian random fields pervade all areas of science. However, it is often the departures from Gaussianity that carry the crucial signature of the nonlinear mechanisms at the heart of diverse phenomena, ranging from structure formation in condensed matter and cosmology to biomedical imaging. The standard test of non-Gaussianity is to measure higher-order correlation functions. In the present work, we take a different route. We show how geometric and topological properties of Gaussian fields, such as the statistics of extrema, are modified by the presence of a non-Gaussian perturbation. The resulting discrepancies give an independent way to detect and quantify non-Gaussianities. In our treatment, we consider both local and nonlocal mechanisms that generate non-Gaussian fields, both statically and dynamically through nonlinear diffusion.
Biomimetic peptoid oligomers as dual-action antifreeze agents
Authors: Huang Mia L. , Ehre David , Jiang Qi , Hu Chunhua , Kirshenbaum Kent , Ward Michael D.
Published: November 2012

The ability of natural peptides and proteins to influence the formation of inorganic crystalline materials has prompted the design of synthetic compounds for the regulation of crystal growth, including the freezing of water and growth of ice crystals. Despite their versatility and ease of structural modification, peptidomimetic oligomers have not yet been explored extensively as crystallization modulators. This report describes a library of synthetic
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-substituted glycine peptoid oligomers that possess “dual-action” antifreeze activity as exemplified by ice crystal growth inhibition concomitant with melting temperature reduction. We investigated the structural features responsible for these phenomena and observed that peptoid antifreeze activities depend both on oligomer backbone structure and side chain chemical composition. These studies reveal the capability of peptoids to act as ice crystallization regulators, enabling the discovery of a unique and diverse family of synthetic oligomers with potential as antifreeze agents in food production and biomedicine.
Cardiac myosin binding protein-C restricts intrafilament torsional dynamics of actin in a phosphorylation-dependent manner
Authors: Colson Brett A. , Rybakova Inna N. , Prochniewicz Ewa , Moss Richard L. , Thomas David D.
Published: November 2012

We have determined the effects of myosin binding protein-C (MyBP-C) and its domains on the microsecond rotational dynamics of actin, detected by time-resolved phosphorescence anisotropy (TPA). MyBP-C is a multidomain modulator of striated muscle contraction, interacting with myosin, titin, and possibly actin. Cardiac and slow skeletal MyBP-C are known substrates for protein kinase-A (PKA), and phosphorylation of the cardiac isoform alters contractile properties and myofilament structure. To determine the effects of MyBP-C on actin structural dynamics, we labeled actin at C374 with a phosphorescent dye and performed TPA experiments. The interaction of all three MyBP-C isoforms with actin increased the final anisotropy of the TPA decay, indicating restriction of the amplitude of actin torsional flexibility by 15–20° at saturation of the TPA effect. PKA phosphorylation of slow skeletal and cardiac MyBP-C relieved the restriction of torsional amplitude but also decreased the rate of torsional motion. In the case of fast skeletal MyBP-C, its effect on actin dynamics was unchanged by phosphorylation. The isolated C-terminal half of cardiac MyBP-C (C5–C10) had effects similar to those of the full-length protein, and it bound actin more tightly than the N-terminal half (C0–C4), which had smaller effects on actin dynamics that were independent of PKA phosphorylation. We propose that these MyBP-C-induced changes in actin dynamics play a role in the functional effects of MyBP-C on the actin–myosin interaction.
Public good dynamics drive evolution of iron acquisition strategies in natural bacterioplankton populations
Authors: Cordero Otto X. , Ventouras Laure-Anne , DeLong Edward F. , Polz Martin F.
Published: November 2012

A common strategy among microbes living in iron-limited environments is the secretion of siderophores, which can bind poorly soluble iron and make it available to cells via active transport mechanisms. Such siderophore–iron complexes can be thought of as public goods that can be exploited by local communities and drive diversification, for example by the evolution of “cheating.” However, it is unclear whether bacterial populations in the environment form stable enough communities such that social interactions significantly impact evolutionary dynamics. Here we show that public good games drive the evolution of iron acquisition strategies in wild populations of marine bacteria. We found that within nonclonal but ecologically cohesive genotypic clusters of closely related Vibrionaceae, only an intermediate percentage of genotypes are able to produce siderophores. Nonproducers within these clusters exhibited selective loss of siderophore biosynthetic pathways, whereas siderophore transport mechanisms were retained, suggesting that these nonproducers can act as cheaters that benefit from siderophore producers in their local environment. In support of this hypothesis, these nonproducers in iron-limited media suffer a significant decrease in growth, which can be alleviated by siderophores, presumably owing to the retention of transport mechanisms. Moreover, using ecological data of resource partitioning, we found that cheating coevolves with the ecological specialization toward association with larger particles in the water column, suggesting that these can harbor stable enough communities for dependencies among organisms to evolve.
Chemogenomic approach identified yeast YLR143W as diphthamide synthetase
Authors: Su Xiaoyang , Lin Zhewang , Chen Wei , Jiang Hong , Zhang Sheng , Lin Hening
Published: November 2012

Many genes are of unknown functions in any sequenced genome. A combination of chemical and genetic perturbations has been used to investigate gene functions. Here we present a case that such “chemogenomics” information can be effectively used to identify missing genes in a defined biological pathway. In particular, we identified the previously unknown enzyme diphthamide synthetase for the last step of diphthamide biosynthesis. We found that yeast protein YLR143W is the diphthamide synthetase catalyzing the last amidation step using ammonium and ATP. Diphthamide synthetase is evolutionarily conserved in eukaryotes. The previously uncharacterized human gene ATPBD4 is the ortholog of yeast YLR143W and fully rescues the deletion of YLR143W in yeast.
Cryo-EM structure of a 3D DNA-origami object
Authors: Bai Xiao-chen , Martin Thomas G. , Scheres Sjors H. W. , Dietz Hendrik
Published: November 2012

A key goal for nanotechnology is to design synthetic objects that may ultimately achieve functionalities known today only from natural macromolecular complexes. Molecular self-assembly with DNA has shown potential for creating user-defined 3D scaffolds, but the level of attainable positional accuracy has been unclear. Here we report the cryo-EM structure and a full pseudoatomic model of a discrete DNA object that is almost twice the size of a prokaryotic ribosome. The structure provides a variety of stable, previously undescribed DNA topologies for future use in nanotechnology and experimental evidence that discrete 3D DNA scaffolds allow the positioning of user-defined structural motifs with an accuracy that is similar to that observed in natural macromolecules. Thereby, our results indicate an attractive route to fabricate nanoscale devices that achieve complex functionalities by DNA-templated design steered by structural feedback.
Predicted structure of agonist-bound glucagon-like peptide 1 receptor, a class B G protein-coupled receptor
Authors: Kirkpatrick Andrea , Heo Jiyoung , Abrol Ravinder , Goddard William A.
Published: November 2012

The glucagon-like peptide 1 receptor (GLP1R) is a G protein-coupled receptor (GPCR) involved in insulin synthesis and regulation; therefore, it is an important drug target for treatment of diabetes. However, GLP1R is a member of the class B1 family of GPCRs for which there are no experimental structures. To provide a structural basis for drug design and to probe class B GPCR activation, we predicted the transmembrane (TM) bundle structure of GLP1R bound to the peptide Exendin-4 (Exe4; a GLP1R agonist on the market for treating diabetes) using the MembStruk method for scanning TM bundle conformations. We used protein–protein docking methods to combine the TM bundle with the X-ray crystal structure of the 143-aa N terminus coupled to the Exe4 peptide. This complex was subjected to 28 ns of full-solvent, full-lipid molecular dynamics. We find 14 strong polar interactions of Exe4 with GLP1R, of which 8 interactions are in the TM bundle (2 interactions confirmed by mutation studies) and 6 interactions involve the N terminus (3 interactions found in the crystal structure). We also find 10 important hydrophobic interactions, of which 4 interactions are in the TM bundle (2 interactions confirmed by mutation studies) and 6 interactions are in the N terminus (6 interactions present in the crystal structure). Thus, our predicted structure agrees with available mutagenesis studies. We suggest a number of mutation experiments to further validate our predicted structure. The structure should be useful for guiding drug design and can provide a structural basis for understanding ligand binding and receptor activation of GLP1R and other class B1 GPCRs.