bluuebunny/crossref_metadata_2025 huggingface dataset:
Stereochemistry of 2,6‐Diaminoadamantane Salts: Transannular Interactions
Authors: Glaser Robert , Steinberg Avital , Šekutor Marina , Rominger Frank , Trapp Oliver , Mlinarić‐Majerski Kata
Published: May 2011

A series of bisprimary, bistertiary, and bisquaternary adamantane‐2,6‐diammonium salts were synthesized from adamantane‐2,6‐dione starting material. Conversion of the dione to a dioxime followed by H2/PtO2 hydrogenation afforded 2,6‐diaminoadamantane dihydrochloride 2a. Reductiveamination of 2a with aqueous formaldehyde (H2/PtO2) gave rac‐N,N,N′,N′‐tetramethyl‐2,6‐diaminoadamantane dihydrochloride salt 3. Diffusion of acetone into a solution of 3 in methanol gave 2.5 hydrate crystals in a triclinic P$\bar {1}$ cell, which had two molecules of opposite handedness and five water molecules in the asymmetric unit. Diamine 2a with excess CH3I yielded rac‐N,N,N,N′,N′,N′‐hexamethyladamantane‐2,6‐diaminium diiodide quaternary salt 4a. Diiodide 4a with molecular bromine gave the corresponding dibromide 4b. Acetone diffusion into a solution of 4a (or 4b) in methanol gave isostructural monohydrate crystals in orthorhombic Pnma cells. An enantiomeric pair of 4a,4b (2RS,6RS)‐diaminium ions is disordered about the mirror plane, since chiral cation occupancy of this location requires symmetry that cannot be fulfilled. In solution, all the cations had C2 symmetry, as detected by NMR spectroscopy, whereas an approximate C2 symmetry was observed in crystals. RmS(G) quantification of crystallographic pseudo‐symmetry shows high fidelity for pseudo‐inversion symmetry between cations of opposite handedness in crystal 3, and for pseudo‐C2 symmetry within adamantane skeletons of crystals 3, 4a, and 4b. Axial NMe3 or NHMe2 groups on adamantane‐2 (or ‐6‐)‐positions suffer cis‐1,3‐diaxial repulsion, very similar to that involving axial tBu or iPr groups and H(axial) protons on cyclohexane. These transannular steric interactions tilt the NMe3 units outward by about 19°, while NHMe2 groups slant outward by a smaller and more usual 7°.
Synthesis of Phosphonylated and Thiolated Indenones by Manganese(III)‐Mediated Addition of Phosphorus‐ and Sulfur‐Centered Radicals to 1,3‐Diarylpropynones
Authors: Zhou Jun , Zhang Guang‐Liang , Zou Jian‐Ping , Zhang Wei
Published: May 2011

Phosphorus‐ or sulfur‐centered radicals generated from the reaction of manganese(III) acetate with dialkyl phosphonates or arylthiols undergo selective additions to conjugated alkynes followed by cyclization and rearomatization to afford 2‐phosphonyl‐ or 2‐thioaryl‐substituted indenones in fair to good yields.
Amino acid analog toxicity in primary rat neuronal and astrocyte cultures: Implications for protein misfolding and TDP‐43 regulation
Authors: Dasuri Kalavathi , Ebenezer Philip J. , Uranga Romina M. , Gavilán Elena , Zhang Le , Fernandez‐Kim Sun O.K. , Bruce‐Keller Annadora J. , Keller Jeffrey N.
Published: May 2011

Amino acid analogs promote translational errors that result in aberrant protein synthesis and have been used to understand the effects of protein misfolding in a variety of physiological and pathological settings. TDP‐43 is a protein that is linked to protein aggregation and toxicity in a variety of neurodegenerative diseases. This study exposed primary rat neurons and astrocyte cultures to established amino acid analogs (canavanine and azetidine‐2‐carboxylic acid) and showed that both cell types undergo a dose‐dependent increase in toxicity, with neurons exhibiting a greater degree of toxicity compared with astrocytes. Neurons and astrocytes exhibited similar increases in ubiquitinated and oxidized protein following analog treatment. Analog treatment increased heat shock protein (Hsp) levels in both neurons and astrocytes. In neurons, and to a lesser extent astrocytes, the levels of TDP‐43 increased in response to analog treatment. Taken together, these data indicate that neurons exhibit preferential toxicity and alterations in TDP‐43 in response to increased protein misfolding compared with astrocytes. © 2011 Wiley‐Liss, Inc.
The Challenges of Marketing Tourism Destinations in the Central African Subregion: the Cameroon Example
Authors: Kimbu Albert Nsom
Published: May 2011

During the last decade, sub‐Saharan Africa has consistently posted one of the highest tourism growth rates averaging approximately 6% per annum between 2007 and 2010. However, not all countries have profited from this growth. Countries in the Central African subregion, even though recognized internationally as potential hot spots for sustainable ecotourism development, are still lagging behind those located in Western, Eastern and Southern Africa. This paper identifies some challenges inhibiting the development and marketing tourism destinations in the Central African subregion in general and Cameroon in particular and proposes some concise measures whose implementation would help in redressing the situation. Copyright © 2011 John Wiley & Sons, Ltd.
Measurement error and survey design in sightability model development
Authors: Walsh Daniel P. , Campa Henry , Beyer Dean E. , Winterstein Scott R.
Published: May 2011

Measurement error of explanatory variables used in sightability models can result in biased population estimates and associated measures of precision. We developed a Monte Carlo simulation procedure that can be implemented within the sightability model framework when measurement error is present. Additionally, we developed simulation and sample survey methods, for determining the optimal allocation of survey effort to maximize precision of population estimates for a fixed survey cost, when a complete survey of a study area is not feasible. We used data from aerial surveys of elk during 2004–2006 in Michigan to demonstrate the application of these techniques. By accounting for measurement error and applying appropriate survey design practices, managers employing sightability models may be able to generate more accurate and cost‐effective population estimates and accompanying measures of precision than is possible if these techniques are ignored. © 2011 The Wildlife Society.
SALINE WETLANDS' FATE IN INLAND DESERTS: AN EXAMPLE OF 80 YEARS' DECLINE IN MONEGROS, SPAIN
Authors: Domínguez‐Beisiegel M. , Herrero J. , Castañeda C.
Published: May 2011

Wetlands inventory is one of the goals of conservation plans on a national scale and a global scale. Inventories are needed for long‐term monitoring or for identifying lost wetlands and those where restoration is feasible. In this article, we present an updated inventory of the saline wetlands of Southern Monegros, Spain. We depicted the evolution of these saline wetlands, locally named saladas with a unique long‐term retrospective study based on aerial photographs from 1927. Their inventory has been accomplished through a map analysis based on a geographical information system using aerial photographs and orthophotographs, topographic maps, unpublished local studies and field surveys. Remaining vegetation, changes in soil moisture and colour, and geomorphology have been the key features in identifying the saladas. Their changes in number, size and shape have been driven by human pressure, the main modifier of landscape in the last 80 years. The information gathered will contribute to the awareness of stakeholders and decision makers for their conservation as natural resources. Moreover, our large retrospective approach is a consistent base from which to propose the inclusion of the saladas of Monegros in the Ramsar list of Wetlands of International Importance. Copyright © 2011 John Wiley & Sons, Ltd.
Measurement of absolute arterial cerebral blood volume in human brain without using a contrast agent
Authors: Hua Jun , Qin Qin , Pekar James J. , van Zijl Peter C. M.
Published: May 2011

Arterial cerebral blood volume (CBVa) is a vital indicator of tissue perfusion and vascular reactivity. We extended the recently developed inflow vascular‐space‐occupancy (iVASO) MRI technique, which uses spatially selective inversion to suppress the signal from blood flowing into a slice, with a control scan to measure absolute CBVa using cerebrospinal fluid (CSF) for signal normalization. Images were acquired at multiple blood nulling times to account for the heterogeneity of arterial transit times across the brain, from which both CBVa and arterial transit times were quantified. Arteriolar CBVa was determined separately by incorporating velocity‐dependent bipolar crusher gradients. Gray matter (GM) CBVa values (n = 11) were 2.04 ± 0.27 and 0.76 ± 0.17 ml blood/100 ml tissue without and with crusher gradients (b = 1.8 s/mm2), respectively. Arterial transit times were 671 ± 43 and 785 ± 69 ms, respectively. The arterial origin of the signal was validated by measuring its T2, which was within the arterial range. The proposed approach does not require exogenous contrast agent administration, and provides a non‐invasive alternative to existing blood volume techniques for mapping absolute CBVa in studies of brain physiology and neurovascular diseases. Copyright © 2011 John Wiley & Sons, Ltd.
Real time spectroscopic ellipsometry of CuInSe2: Growth dynamics, dielectric function, and its dependence on temperature
Authors: Begou Thomas , Walker James D. , Attygalle Dinesh , Ranjan Vikash , Collins R. W. , Marsillac Sylvain
Published: May 2011

This Letter reports real time spectroscopic ellipsometry studies of copper indium diselenide (CuInSe2; CIS). A Volmer‐Weber nucleation process was identified from the measured thickness dynamics, and accurate dielectric functions were obtained in‐situ, avoiding oxidation while correcting for surface roughness. The energy and broadening parameters of the critical points in the dielectric functions obtained versus measurement temperature (including three previously unreported ones) yield a database that is valuable for on‐line materials analysis. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ISO/IEC 17025 Accreditation: Between the Desired Gains and the Reality
Authors: Abdel‐Fatah Hesham Tawfik M.
Published: May 2011

In this study, the implementation of the ISO/IEC 17025 standard in a Transformer Oil Testing Laboratory (TOTL) for performing the Electrical Breakdown Voltage was evaluated. The application of such a QA system involves a great deal of human resources, top management commitment, organizational effort, expertise and expense. Three years of experience of working under the ISO/IEC 17025 compliant quality system is described. The enhanced reliability of the test results, the technical competence of TOTL staff, the increased trust and satisfaction of established customers and the improved reputation of the TOTL are important gains that are attained from the application of the ISO/IEC 17025 standard. Conversely, the drawbacks that resulted from implementing and maintaining the ISO/IEC 17025 QA system were enormous costs, time‐consuming efforts, and increased documentation of test procedures. In addition, no new customers or contracts were generated as had been expected. Therefore, the author does not recommend that laboratories pursue ISO/IEC 17025 accreditation unless the requirement is necessitated by customer needs and only when the test for accreditation is entirely appropriate. Moreover, significant benefits covering the costs of establishing, implementation, accreditation and maintaining of this standard should be identified. Copyright © 2011 John Wiley & Sons, Ltd.
Endometrial cancer and ultrasound: why measuring endometrial thickness is sometimes not enough
Authors: Naftalin J. , Nunes N. , Hoo W. , Arora R. , Jurkovic D.
Published: May 2011

Endometrial cancer is the commonest cancer of the female genital tract in the developed world. Ultrasound measurement of endometrial thickness is commonly used to triage patients with postmenopausal bleeding for histological sampling. The sensitivity of ultrasound in diagnosing endometrial cancer is high, but it has a small, well‐defined false‐negative rate. In this report we describe two cases, with histological confirmation, of postmenopausal women without any vaginal bleeding, who were subsequently diagnosed with advanced endometrial cancer. They were found to have a thin, normal endometrium on ultrasound. In both cases, histological examination was suggestive of endometrial cancer originating from foci of adenomyosis. These findings suggest that a proportion of the false‐negative diagnoses of endometrial cancer on ultrasound could be caused by the disease being confined to the myometrium rather than as a result of suboptimal performance of ultrasound examination. Copyright © 2011 ISUOG. Published by John Wiley & Sons, Ltd.
Transitions Between Lanthanum Cuprates: Crystal Structures of T′, Orthorhombic, and K2NiF4‐type La2CuO4
Authors: Hord Roland , Cordier Gerhard , Hofmann Kathrin , Buckow Alexander , Pascua Gwendolyne , Luetkens Hubertus , Alff Lambert , Albert Barbara
Published: May 2011

Through low‐temperature synthesis in CsOH flux, lanthanum cuprate La2CuO4 can be obtained in a metastable form, the so‐called T′ modification (tetragonal, I4/mmm, no. 139, a = 400.95(2) pm, c = 1254.08(7) pm). When heated, this T′ phase transforms into a K2NiF4‐type modification, whose crystal structure was now refined from X‐ray powder data (tetragonal, I4/mmm, no. 139, a = 383.29(3) pm, c = 1331.3(2) pm at T = 1073 K). The well‐known orthorhombic phase (s.g. Cmce, no. 64, a = 536.14(3) pm, b = 1315.53(8) pm, c = 540.20(3) pm) – usually obtained via conventional solid state synthesis – was observed to form upon cooling from the K2NiF4‐type modification. High‐temperature powder diffractometry allowed crystal structure refinements for all of the three phases.
Single operator peroral cholangioscopic guided therapy of bile duct stones
Authors: Seelhoff Alexander , Schumacher Brigitte , Neuhaus Horst
Published: May 2011

Since the introduction of endoscopic sphincterotomy, stone clearance of the bile duct can be achieved by conventional endoscopic means in up to 90% of patients with stone disease. Several endoscopic therapies for difficult bile duct stones have been introduced. Laser therapy for stone fragmentation under direct visual control via the peroral insertion of a cholangioscope (POCS) in the bile duct has proven to be highly effective, further raising the success rate of endoscopic biliary stone clearance. However, conventional POCS has not gained wide acceptance because of several technical limitations such as fragility, impaired steerability and the need for two endoscopists. These limitations may be overcome with a newly developed single operator peroral cholangioscope, the SpyGlass® Direct Visualization System. First clinical data of SpyGlass guided intraductal stone fragmentation with EHL or laser fibers report high safety and efficacy of the procedure.
Association between prodromal pain and the severity of acute herpes zoster and utilization of health care resources
Authors: Benbernou Atika , Drolet Mélanie , Levin Myron J. , Schmader Kenneth E. , Oxman Michael N. , Johnson Robert , Patrick David , Camden Stéphanie , Mansi James A. , Brisson Marc
Published: May 2011

Background: Herpes zoster results from the reactivation of the varicella‐zoster virus, which is often accompanied by a prodrome of dermatomal pain. Little is known about the burden of prodromal pain.

Objectives: (1) Describe the frequency, severity and duration of prodromal pain; (2) determine the relationship between prodromal pain and the characteristics of herpes zoster at recruitment and the utilization of health care resources.

Methods: Between 10/2005 and 07/2006, 251 subjects ≥50 years old, seeking care for herpes zoster within 14 days of rash onset, were recruited across Canada. Severity and duration of prodromal pain were measured retrospectively using the Initial Zoster Impact Questionnaire. The burden of prodromal pain was obtained by the product of pain severity and duration. The severity of acute herpes zoster pain was measured using the Zoster Brief Pain Inventory.

Results: The majority of participants reported prodromal pain (74%). Mean pain duration and severity were 4.7 days and 6/10, respectively. Subjects aged 61–70 years old were more likely to report prodromal pain (RR = 1.14, p‐value = 0.02). The burden of prodromal pain was greater in subjects not working (p‐value = 0.02) or immunosuppressed (p‐value = 0.04). Prodromal pain was associated with more severe acute pain (6.2 vs. 4.3, p‐value < 0.0001). Compared to subjects who did not report prodromal pain, those with this pain were more likely to receive antivirals (RR = 1.18, p‐value = 0.04) and to visit the emergency room (RR = 2.56, p‐value = 0.04).

Conclusion: The burden of prodromal pain is significant and should be considered when evaluating the overall benefit of herpes zoster vaccination.
Ten years after: Interference of hospital slack in process performance benefits of quality practices
Authors: Goldstein Susan Meyer , Iossifova Albena R.
Published: May 2011

We investigate the long‐term relationship between an organization's quality management practices and process‐level performance. Further, we examine whether availability of organizational slack over the study interval interferes with the relationship between quality practices and process performance. Organizational slack consists of the available and accessible resources in an organization; we focus here on unabsorbed slack in the form of financial resources. We investigate the quality practices of U.S. general acute care hospitals, measured by their depth of implementation of practices characterizing a total quality management system, and use them to predict process performance related to four medical conditions. Analysis reveals differing effects that are dependent on hospital slack conditions. In hospitals with high slack, quality practices significantly predict three of four studied process performance measures. In contrast, in hospitals with low slack, quality practices predict only one of the four process performance measures, while other factors outweigh the effects of quality practices. This study lends support to management taking a long‐term perspective related to implementation of quality management systems, and highlights the relevance of slack conditions in garnering the benefits of such systems.
Steady flow in a rapidly rotating sphere with weak precession
Authors: KIDA SHIGEO
Published: May 2011

The flow field of an incompressible viscous fluid in a precessing sphere is investigated by the asymptotic analysis for large Reynolds numbers and small Poincaré numbers. The long-standing unsolved equation (Roberts & Stewartson Astrophys. J., vol. 137, 1963, p. 777) for the velocity in the critical region of the boundary layer is solved for the first time in the literature, which enables us to describe explicitly the structure of the conical shear layers spawned from the critical regions into the interior inviscid region. Most of the flux between the boundary layer and the interior is taking place through these conical shear layers. The velocity field in the whole sphere, expanded in a power series of the Poincaré number, is quantitatively determined up to the first order, leaving the solid-body-rotation component to the next-order analysis.
The templates of non-singular Smale flows on three manifolds
Authors: YU BIN
Published: May 2011

In this paper, we first discuss some connections between template theory and the description of basic sets of Smale flows on 3-manifolds due to F. Béguin and C. Bonatti. The main tools we use are symbolic dynamics, template moves and some combinatorial surgeries. Secondly, we obtain some relationship between the surgeries and the number of S1×S2 factors of M for a non-singular Smale flow on a given closed orientable 3-manifold M. We also prove that any template T can model a basic set Λ of a non-singular Smale flow on nS1×S2 for some positive integer n.
China's attempts to minimize non-CO2 emissions from coal: evidence of declining emission intensity
Authors: SHI XUNPENG
Published: May 2011

This paper argues that the use of coal can be reconciled with the environment. In the empirical work, three environmental pollutants are considered, using two alternative methods with two sets of Chinese data. CO2 emissions could not be studied because of data limitations. The hypothesis that the use of coal can be reconciled with the environment through declined emission intensity is confirmed by the empirical tests. The decreases in emission intensity are driven by the application of clean coal technologies, which can be encouraged by appropriate regulations and incentives and have both environmental and economic benefits. Therefore it is critical that appropriate legal and fiscal regimes be formulated and that the development and utilization of high-efficiency and clean coal technologies be promoted. The paper also suggests that the use of coal could continue to be reconciled with concern for the environment, even while considering CO2 emissions.
Participation in environmental organizations: an empirical analysis
Authors: TORGLER BENNO , GARCÍA-VALIÑAS MARÍA A. , MACINTYRE ALISON
Published: May 2011

The literature on volunteering has increased over the last few years. However, despite the importance of active environmental participation for solving public good and externality problems, there is still a lack of substantial empirical evidence regarding several interesting factors that influence this form of volunteering. This empirical study investigates the area by analyzing a cross-section of individuals from 38 countries using micro-data from wave III of the World Values Survey (1995–1997). The results suggest that individuals' active participation in environmental organizations is related not only to socioeconomic factors but also to political interest. We also find that a higher level of corruption is related to participation in environmental organizations. However, the situation is different for transition countries in which there was a collapse of institutional structures. The energy required to negotiate the ensuing chaos may have crowded out other forms of engagement.
Fermented soyabean and vitamin C-rich fruit: a possibility to circumvent the further decrease of iron status among iron-deficient pregnant women in Indonesia
Authors: Wijaya-Erhardt Maria , Muslimatun Siti , Erhardt Juergen G
Published: May 2011

Objective

Increasing the consumption of Fe-rich foods and thus improving Fe bioavailability without significantly increasing diet cost is the most sustainable intervention for improving Fe intake. We assessed the effect of supplementary food consisting of fermented soyabean (tempeh) and vitamin C-rich fruit consumed during pregnancy on maternal iron deficiency (ID).

Design

Pregnant women were randomly allocated by village into optimized diet and control groups. Supplementary food was given 6 d/week at home. The average weekly food provided comprised 600 g of tempeh, 30 g of meat, 350 g of guava, 300 g of papaya and 100 g of orange. Hb, ferritin and transferrin receptor (TfR) concentrations were measured at 12–20 and at 32–36 weeks of gestation.

Setting

Thirty-nine villages in Indonesia.

Subjects

Pregnant women (12–20 weeks of gestation, n 252).

Results

At baseline, mean Hb, ferritin and TfR concentrations and body Fe concentration were within the normal range and did not differ between groups. At near term, mean Hb, ferritin and body Fe decreased, whereas mean TfR increased significantly in both groups. The mean changes in Fe status were similar in both groups. In Fe-deficient women, consumption of an optimized diet was associated with smaller decreases in Hb (1·02 (95 % CI 0·98, 1·07) g/l; P = 0·058), ferritin (1·42 (95 % CI 1·16, 1·75) μg/l; P = 0·046) and body Fe (2·57 (95 % CI 1·71, 3·43) mg/kg; P = 0·073) concentrations, compared with a state of no intervention. Fe-deficient women at baseline benefited more from supplementary food compared with Fe-replete women.

Conclusions

Daily supplementary food containing tempeh and vitamin C-rich fruits during pregnancy might have positive effects on maternal ID.
HIV‐specific CD8+ T‐cell proliferation is prospectively associated with delayed disease progression
Authors: McKinnon Lyle R , Kaul Rupert , Kimani Joshua , Nagelkerke Nico J , Wachihi Charles , Fowke Keith R , Ball Terry Blake , Plummer Francis A
Published: May 2011

Human immunodeficiency virus (HIV)‐specific CD8+ T‐cell proliferation is consistently correlated with enhanced host HIV immune control, but whether proliferative responses are a cause or consequence of immune protection is unclear. We measured Env‐specific CD8+ T‐cell proliferation and interferon (IFN)‐γ secretion in HIV‐infected participants with CD4 counts >200, who then completed 121 person‐years of prospective follow‐up to monitor HIV disease progression. In all, 13 of 31 participants (42%) reached end point during longitudinal follow‐up. Strong Env‐specific CD8+ T‐cell proliferation (>10% of CD8+ T cells) was observed in 14/31 participants at baseline, and this was associated with a longer time to HIV disease progression end point, stratified baseline CD4 count (P=0.016). No associations were observed for IFN‐γ ELISPOT responses and progression (P>0.2). Strong proliferation remained significant in multivariate Cox regression analyses (P=0.044) as an independent predictor of delayed HIV disease progression, along with baseline CD4 count (P=0.04). Duration of HIV infection was associated with more rapid progression in univariate, but not multivariate, analysis (P=0.112). Age and baseline viral load were not predictive of progression. HIV‐specific CD8+ T‐cell proliferation was a correlate of protective immunity in this prospective study; such responses may be important for HIV vaccine protection.
Extension of Dirac's chord method to the case of a nonconvex set by the use of quasi-probability distributions
Authors: Vlasov Alexander Yu.
Published: May 2011

The Dirac's chord method may be suitable in different areas of physics for the representation of certain six-dimensional integrals for a convex body using the probability density of the chord length distribution. For a homogeneous model with a nonconvex body inside a medium with identical properties an analogue of the Dirac's chord method may be obtained, if to use so-called generalized chord distribution. The function is defined as normalized second derivative of the autocorrelation function. For nonconvex bodies this second derivative may have negative values and could not be directly related with a probability density. An interpretation of such a function using alternating sums of probability densities is considered. Such quasi-probability distributions may be used for Monte Carlo calculations of some integrals for a single body of arbitrary shape and for systems with two or more objects and such applications are also discussed in this work.
Rate of convergence in nonlinear Hartree dynamics with factorized initial data
Authors: Chen Li , Lee Ji Oon
Published: May 2011

The mean field dynamics of an N-particle weekly interacting Boson system can be described by the nonlinear Hartree equation. In this paper, we present estimates on the 1/N rate of convergence of many-body Schrödinger dynamics to the one-body nonlinear Hartree dynamics with factorized initial data with two-body interaction potential V in \documentclass[12pt]{minimal}\begin{document}$L^3 (\mathbb {R}^3)+ L^{\infty } (\mathbb {R}^3)$\end{document}L3(R3)+L∞(R3).
Combined effects of metal complexation and size expansion in the electronic structure of DNA base pairs
Authors: Brancolini Giorgia , Felice Rosa Di
Published: May 2011

Novel DNA derivatives have been recently investigated in the pursuit of modified DNA duplexes to tune the electronic structure of DNA-based assemblies for nanotechnology applications. Size-expanded DNAs (e.g., xDNA) and metalated DNAs (M-DNA) may enhance stacking interactions and induce metallic conductivity, respectively. Here we explore possible ways of tailoring the DNA electronic structure by combining the aromatic size expansion with the metal-doping. We select the salient structures from our recent study on natural DNA pairs complexed with transition metal ions and consider the equivalent model configurations for xDNA pairs. We present the results of density functional theory electronic structure calculations of the metalated expanded base-pairs with various localized basis sets and exchange-correlation functionals. Implicit solvent and coordination water molecules are also included. Our results indicate that the effect of base expansion is largest in Ag-xGC complexes, while Cu-xGC complexes are the most promising candidates for nanowires with enhanced electron transfer and also for on-purpose modification of the DNA double-helix for signal detection.
Simulations of a lattice model of two-headed linear amphiphiles: Influence of amphiphile asymmetry
Authors: Jackson Douglas R. , Mohareb Amir , MacNeil Jennifer , Razul M. Shajahan G. , Marangoni D. Gerrard , Poole Peter H.
Published: May 2011

Using a 2D lattice model, we conduct Monte Carlo simulations of micellar aggregation of linear-chain amphiphiles having two solvophilic head groups. In the context of this simple model, we quantify how the amphiphile architecture influences the critical micelle concentration (CMC), with a particular focus on the role of the asymmetry of the amphiphile structure. Accordingly, we study all possible arrangements of the head groups along amphiphile chains of fixed length N = 12 and 16 molecular units. This set of idealized amphiphile architectures approximates many cases of symmetric and asymmetric gemini surfactants, double-headed surfactants, and boloform surfactants. Consistent with earlier results, we find that the number of spacer units s separating the heads has a significant influence on the CMC, with the CMC increasing with s for s < N/2. In comparison, the influence of the asymmetry of the chain architecture on the CMC is much weaker, as is also found experimentally.
Energy gap tuning in uniaxial strained zigzag graphene nanoribbons
Authors: Liu Fei , Liu Xiaoyan , Kang Jinfeng
Published: May 2011

The band structures of zigzag graphene nanoribbons under uniaxial strain are investigated within the mean-field Hubbard model. In addition to the intrinsic gap modification, the strain can induce two additional gaps in the conduction and valence bands when the compressive strain along the armchair direction or the tensile strain along the zigzag direction is greater than 13%. These band gap variations can be attributed to uniaxial strain which causes the breaking of the lattice symmetry and two different hopping energies. The ratio of the two different hopping energies impacts on the intrinsic and the strain induced gaps.
Improve growth rate of Smith–Purcell free-electron laser by Bragg reflector
Authors: Li D. , Yang Z. , Tsunawaki Y. , Asakawa M. R. , Hangyo M. , Miyamoto S. , Imasaki K.
Published: May 2011

Grating with Bragg reflectors for the Smith–Purcell free-electron laser is proposed to improve the reflection coefficient, resulting in enhancing the interaction of the surface wave with the electron beam and, consequently, relax the requirements to the electron beam. With the help of particle-in-cell simulations, it has been shown that the usage of Bragg reflectors may improve the growth rate, shorten the time for the device to reach saturation, and lower the start current for the operation of a Smith–Purcell free-electron laser.
Forces guiding assembly of light-harvesting complex 2 in native membranes
Authors: Liu Lu-Ning , Duquesne Katia , Oesterhelt Filipp , Sturgis James N. , Scheuring Simon
Published: May 2011

Interaction forces of membrane protein subunits are of importance in their structure, assembly, membrane insertion, and function. In biological membranes, and in the photosynthetic apparatus as a paradigm, membrane proteins fulfill their function by ensemble actions integrating a tight assembly of several proteins. In the bacterial photosynthetic apparatus light-harvesting complexes 2 (LH2) transfer light energy to neighboring tightly associated core complexes, constituted of light-harvesting complexes 1 (LH1) and reaction centers (RC). While the architecture of the photosynthetic unit has been described, the forces and energies assuring the structural and functional integrity of LH2, the assembly of LH2 complexes, and how LH2 interact with the other proteins in the supramolecular architecture are still unknown. Here we investigate the molecular forces of the bacterial LH2 within the native photosynthetic membrane using atomic force microscopy single-molecule imaging and force measurement in combination. The binding between LH2 subunits is fairly weak, of the order of
k
B
T
, indicating the importance of LH2 ring architecture. In contrast LH2 subunits are solid with a free energy difference of 90
k
B
T
between folded and unfolded states. Subunit α-helices unfold either in one-step, α- and β-polypeptides unfold together, or sequentially. The unfolding force of transmembrane helices is approximately 150 pN. In the two-step unfolding process, the β-polypeptide is stabilized by the molecular environment in the membrane. Hence, intermolecular forces influence the structural and functional integrity of LH2.
Naturally occurring aminoacyl-tRNA synthetases editing-domain mutations that cause mistranslation in
Mycoplasma
parasites
Authors: Li Li , Boniecki Michal T. , Jaffe Jacob D. , Imai Brian S. , Yau Peter M. , Luthey-Schulten Zaida A. , Martinis Susan A.
Published: May 2011

Mycoplasma
parasites escape host immune responses via mechanisms that depend on remarkable phenotypic plasticity. Identification of these mechanisms is of great current interest. The aminoacyl-tRNA synthetases (AARSs) attach amino acids to their cognate tRNAs, but occasionally make errors that substitute closely similar amino acids. AARS editing pathways clear errors to avoid mistranslation during protein synthesis. We show here that AARSs in
Mycoplasma
parasites have point mutations and deletions in their respective editing domains. The deleterious effect on editing was confirmed with a specific example studied in vitro. In vivo mistranslation was determined by mass spectrometric analysis of proteins produced in the parasite. These mistranslations are uniform cases where the predicted closely similar amino acid replaced the correct one. Thus, natural AARS editing-domain mutations in
Mycoplasma
parasites cause mistranslation. We raise the possibility that these mutations evolved as a mechanism for antigen diversity to escape host defense systems.
Gain of chromosome band 7q11 in papillary thyroid carcinomas of young patients is associated with exposure to low-dose irradiation
Authors: Heß Julia , Thomas Gerry , Braselmann Herbert , Bauer Verena , Bogdanova Tatjana , Wienberg Johannes , Zitzelsberger Horst , Unger Kristian
Published: May 2011

The main consequence of the Chernobyl accident has been an increase in papillary thyroid carcinomas (PTCs) in those exposed to radioactive fallout as young children. Our aim was to identify genomic alterations that are associated with exposure to radiation. We used array comparative genomic hybridization to analyze a main (
n
= 52) and a validation cohort (
n
= 28) of PTC from patients aged <25 y at operation and matched for age at diagnosis and residency. Both cohorts consisted of patients exposed and not exposed to radioiodine fallout. The study showed association of a gain on chromosome 7 (7q11.22–11.23) with exposure (false discovery rate = 0.035). Thirty-nine percent of the exposed group showed the alteration; however, it was not found in a single case from the unexposed group. This was confirmed in the validation set. Because only a subgroup of cases in the exposed groups showed gain of 7q11.22–11.23, it is likely that different molecular subgroups and routes of radiation-induced carcinogenesis exist. The candidate gene CLIP2 was specifically overexpressed in the exposed cases. In addition, the expression of the genes PMS2L11, PMS2L3, and STAG3L3 correlated with gain of 7q11.22–11.23. An enrichment of Gene Ontology terms “DNA repair” (PMS2L3, PMS2L5), “response to DNA damage stimulus” (BAZ1B, PMS2L3, PMS2L5, RFC2), and “cell–cell adhesion” (CLDN3, CLDN4) was found. This study, using matched exposed and unexposed cohorts, provides insights into the radiation-related carcinogenesis of young-onset PTC and, with the exposure-specific gain of 7q11 and overexpression of the CLIP2 gene, radiation-specific molecular markers.
Structure of a bacterial cell surface decaheme electron conduit
Authors: Clarke Thomas A. , Edwards Marcus J. , Gates Andrew J. , Hall Andrea , White Gaye F. , Bradley Justin , Reardon Catherine L. , Shi Liang , Beliaev Alexander S. , Marshall Matthew J. , Wang Zheming , Watmough Nicholas J. , Fredrickson James K. , Zachara John M. , Butt Julea N. , Richardson David J.
Published: May 2011

Some bacterial species are able to utilize extracellular mineral forms of iron and manganese as respiratory electron acceptors. InShewanella oneidensisthis involves decaheme cytochromes that are located on the bacterial cell surface at the termini of trans-outer-membrane electron transfer conduits. The cell surface cytochromes can potentially play multiple roles in mediating electron transfer directly to insoluble electron sinks, catalyzing electron exchange with flavin electron shuttles or participating in extracellular intercytochrome electron exchange along “nanowire” appendages. We present a 3.2-Å crystal structure of one of these decaheme cytochromes, MtrF, that allows the spatial organization of the 10 hemes to be visualized for the first time. The hemes are organized across four domains in a unique crossed conformation, in which a staggered 65-Å octaheme chain transects the length of the protein and is bisected by a planar 45-Å tetraheme chain that connects two extended Greek key split β-barrel domains. The structure provides molecular insight into how reduction of insoluble substrate (e.g., minerals), soluble substrates (e.g., flavins), and cytochrome redox partners might be possible in tandem at different termini of a trifurcated electron transport chain on the cell surface.
Glucocorticoids target suppressor of cytokine signaling 1 (SOCS1) and type 1 interferons to regulate Toll-like receptor–induced STAT1 activation
Authors: Bhattacharyya Sandip , Zhao Yuxing , Kay Thomas W. H. , Muglia Louis J.
Published: May 2011

Endogenous and pharmacologic glucocorticoids (GCs) limit inflammatory cascades initiated by Toll-like receptor (TLR) activation. A long-standing clinical observation has been the delay between GC administration and the manifestation of GC's anti-inflammatory actions. We hypothesized that the GCs would have inhibitory effects that target late temporal pathways that propagate proinflammatory signals. Here we interrogated signal transducer and activator of transcription 1 (STAT1) regulation by GC and its consequences for cytokine production during activation of macrophages with TLR-specific ligands. We found that robust STAT1 activation does not occur until 2–3 h after TLR engagement, and that GC suppression of STAT1 phosphorylation first manifests at this time. GC attenuates TLR4-mediated STAT1 activation only through induction of suppressor of cytokine signaling 1 (SOCS1), which increases throughout the 6-h period after treatment. Inhibition of TLR3-mediated STAT1 activation occurs via two mechanisms, impairment of type I IFN secretion and induction of SOCS1. Our data show that SOCS1 and type I interferons are critical GC targets for regulating STAT1 activity and may account for overall GC effectiveness in inflammation suppression in the clinically relevant time frame.
Isotopic Ag–Cu–Pb record of silver circulation through 16th–18th century Spain
Authors: Desaulty Anne-Marie , Telouk Philippe , Albalat Emmanuelle , Albarède Francis
Published: May 2011

Estimating global fluxes of precious metals is key to understanding early monetary systems. This work adds silver (Ag) to the metals (Pb and Cu) used so far to trace the provenance of coinage through variations in isotopic abundances. Silver, copper, and lead isotopes were measured in 91 coins from the East Mediterranean Antiquity and Roman world, medieval western Europe, 16th–18th century Spain, Mexico, and the Andes and show a great potential for provenance studies. Pre-1492 European silver can be distinguished from Mexican and Andean metal. European silver dominated Spanish coinage until Philip III, but had, 80 y later after the reign of Philip V, been flushed from the monetary mass and replaced by Mexican silver.
Cholinergic chemosensory cells in the trachea regulate breathing
Authors: Krasteva Gabriela , Canning Brendan J. , Hartmann Petra , Veres Tibor Z. , Papadakis Tamara , Mühlfeld Christian , Schliecker Kirstin , Tallini Yvonne N. , Braun Armin , Hackstein Holger , Baal Nelli , Weihe Eberhard , Schütz Burkhard , Kotlikoff Michael , Ibanez-Tallon Ines , Kummer Wolfgang
Published: May 2011

In the epithelium of the lower airways, a cell type of unknown function has been termed “brush cell” because of a distinctive ultrastructural feature, an apical tuft of microvilli. Morphologically similar cells in the nose have been identified as solitary chemosensory cells responding to taste stimuli and triggering trigeminal reflexes. Here we show that brush cells of the mouse trachea express the receptors (Tas2R105, Tas2R108), the downstream signaling molecules (α-gustducin, phospholipase C
β2
) of bitter taste transduction, the synthesis and packaging machinery for acetylcholine, and are addressed by vagal sensory nerve fibers carrying nicotinic acetylcholine receptors. Tracheal application of an nAChR agonist caused a reduction in breathing frequency. Similarly, cycloheximide, a Tas2R108 agonist, evoked a drop in respiratory rate, being sensitive to nicotinic receptor blockade and epithelium removal. This identifies brush cells as cholinergic sensors of the chemical composition of the lower airway luminal microenvironment that are directly linked to the regulation of respiration.
Paul trapping of charged particles in aqueous solution
Authors: Guan Weihua , Joseph Sony , Park Jae Hyun , Krstić Predrag S. , Reed Mark A.
Published: May 2011

We experimentally demonstrate the feasibility of an aqueous Paul trap using a proof-of-principle planar device. Radio frequency voltages are used to generate an alternating focusing/defocusing potential well in two orthogonal directions. Individual charged particles are dynamically confined into nanometer scale in space. Compared with conventional Paul traps working in frictionless vacuum, the aqueous environment associated with damping forces and thermally induced fluctuations (Brownian noise) exerts a fundamental influence on the underlying physics. We investigate the impact of these two effects on the confining dynamics, with the aim to reduce the rms value of the positional fluctuations. We find that the rms fluctuations can be modulated by adjusting the voltages and frequencies. This technique provides an alternative for the localization and control of charged particles in an aqueous environment.
p53 binding to nucleosomes within the p21 promoter in vivo leads to nucleosome loss and transcriptional activation
Authors: Laptenko Oleg , Beckerman Rachel , Freulich Ella , Prives Carol
Published: May 2011

It is well established that p53 contacts DNA in a sequence-dependent manner in order to transactivate its myriad target genes. Yet little is known about how p53 interacts with its binding site/response element (RE) within such genes in vivo in the context of nucleosomal DNA. In this study we demonstrate that both distal (5′) and proximal (3′) p53 REs within the promoter of the
p21
gene in unstressed HCT116 colon carcinoma cells are localized within a region of relatively high nucleosome occupancy. In the absence of cellular stress, p53 is prebound to both
p21
REs within nucleosomal DNA in these cells. Treatment of cells with the DNA-damaging drug doxorubicin or the p53 stabilizing agent Nutlin-3, however, is accompanied by p53-dependent subsequent loss of nucleosomes associated with such p53 REs. We show that in vitro p53 can bind to mononucleosomal DNA containing the distal
p21
RE, provided the binding site is not close to the diad center of the nucleosome. In line with this, our data indicate that the p53 distal RE within the
p21
gene is located close to the end of the nucleosome. Thus, low- and high-resolution mapping of nucleosome boundaries around p53 REs within the
p21
promoter have provided insight into the mechanism of p53 binding to its sites in cells and the consequent changes in nucleosome occupancy at such sites.
Relating domain size distribution to line tension and molecular dipole density in model cytoplasmic myelin lipid monolayers
Authors: Lee Dong Woog , Min Younjin , Dhar Prajnaparamitra , Ramachandran Arun , Israelachvili Jacob N. , Zasadzinski Joseph A.
Published: May 2011

We fit the size distribution of liquid-ordered (
L
o
) domains measured from fluorescence images of model cytoplasmic myelin monolayers with an equilibrium thermodynamic expression that includes the competing effects of line tension,
λ
, dipole density difference, Δ
m
, and the mixing entropy. From these fits, we extract the line tension,
λ
, and dipole density difference, Δ
m
, between the
L
o
and liquid-disordered (
L
d
) phases. Both
λ
and Δ
m
decrease with increasing surface pressure,

, although
λ
/Δ
m
2
remains roughly constant as the monolayer approaches the miscibility surface pressure. As a result, the mean domain size changed little with surface pressure, although the polydispersity increased significantly. The most probable domain radius was significantly smaller than that predicted by the energy alone, showing that the mixing entropy promotes a greater number of smaller domains. Our results also explain why domain shapes are stable; at equilibrium, only a small fraction of the domains are large enough to undergo theoretically predicted shape fluctuations. Monolayers based on the composition of myelin from animals with experimental allergic encephalomyelitis had slightly lower values of
λ
and Δ
m
, and a higher area fraction of domains, than control monolayers at all

. While it is premature to generalize these results to myelin bilayers, our results show that the domain distribution in myelin may be an equilibrium effect and that subtle changes in surface pressure and composition can alter the distribution of material in the monolayer, which will likely also alter the interactions between monolayers important to the adhesion of the myelin sheath.
One collagen shipment, ready for delivery
Authors: Leslie Mitch
Published: May 2011

An ER membrane protein helps load collagen into vesicles.
Polyubiquitin binding to ABIN1 is required to prevent autoimmunity
Authors: Nanda Sambit K. , Venigalla Ram K.C. , Ordureau Alban , Patterson-Kane Janet C. , Powell David W. , Toth Rachel , C. Arthur J. Simon , Cohen Philip
Published: May 2011

The protein ABIN1 possesses a polyubiquitin-binding domain homologous to that present in nuclear factor κB (NF-κB) essential modulator (NEMO), a component of the inhibitor of NF-κB (IκB) kinase (IKK) complex. To address the physiological significance of polyubiquitin binding, we generated knockin mice expressing the ABIN1[D485N] mutant instead of the wild-type (WT) protein. These mice developed all the hallmarks of autoimmunity, including spontaneous formation of germinal centers, isotype switching, and production of autoreactive antibodies. Autoimmunity was suppressed by crossing to MyD88−/− mice, demonstrating that toll-like receptor (TLR)–MyD88 signaling pathways are needed for the phenotype to develop. The B cells and myeloid cells of the ABIN1[D485N] mice showed enhanced activation of the protein kinases TAK, IKK-α/β, c-Jun N-terminal kinases, and p38α mitogen-activated protein kinase and produced more IL-6 and IL-12 than WT. The mutant B cells also proliferated more rapidly in response to TLR ligands. Our results indicate that the interaction of ABIN1 with polyubiquitin is required to limit the activation of TLR–MyD88 pathways and prevent autoimmunity.