bluuebunny/crossref_metadata_2025 huggingface dataset:
NMR spectroscopy of citrate in solids: cross‐polarization kinetics in weakly coupled systems
Authors: Feng Jian , Lee Young J. , Kubicki James D. , Reeder Richard J. , Phillips Brian L.
Published: February 2008

Solid‐state NMR spectroscopy is a potentially powerful method for obtaining molecular level structural information crucial for understanding the specific relationship between calcite crystals and occluded organic molecules that are important in biomineralization and biomimetic materials. In this work, a method is developed based on cross‐polarization/magic angle spinning (CP/MAS) NMR to measure the heteronuclear distances and obtain structural information for large intracrystalline citrate defects in a synthetic calcite/citrate composite. Using compounds with well‐characterized crystal structures, Mg(II) citrate and Sr(II) citrate, a correlation is established between TIS, the CP time, and M2IS, the van Vleck heteronuclear dipolar second moment, which contains distance and structural information. This correlation is supported by peak assignments obtained from calculations of the 13C chemical shifts for crystalline Mg(II) citrate. On the basis of TIS−1 versus M2IS correlation, measurement of TIS for carbonate ions associated with citrate defects in a calcite(13C‐enriched)/citrate coprecipitate yields an estimate for the distance between citrate and the nearest carbonate carbon that indicates close spatial proximity and provides useful constraints for future computational study. The applicability of TIS−1 versus M2IS correlations to other weakly coupled spin‐1/2 systems is discussed in terms of the effects of 1H homonuclear dipolar coupling, using the CP kinetics of Zn(II) dihydroxybenzoate and kaolinite for comparison. The results suggest a limited range of correlation constants and indicate that quantitative information can be obtained from CP/MAS kinetics obtained under similar experimental conditions. Copyright © 2008 John Wiley & Sons, Ltd.
Stereochemistry and conformations of natural 1,2‐epoxy‐guaianolides based on 1D and 2D NMR data and semiempirical calculations
Authors: Trifunović Snežana , Milosavljević Slobodan , Vajs Vlatka , Macura Slobodan , Todorović Nina
Published: February 2008

From detailed study of 1D and 2D NMR spectra of ten natural 1,2‐epoxyguaianolides (bis‐1,2:3,4‐epoxyguaianolides and guaianolide‐1,2‐epoxychlorohydrins), we identified general spectral traits helpful for stereochemical assignment of such sesquiterpene lactones. We found that the chemical shifts of certain 1H and 13C nuclei are consistently dependent on the configuration of 1,2‐epoxy‐ring which could be used as a simple rule for establishing this configuration. Then, from 1D and 2D (COSY, NOESY, HMQC, HMBC) NMR data, applying the observed rule, the structure and stereochemistry of two new, diastereomeric guaianolide‐1,2‐epoxychlorohydrins, isolated from Achillea serbica, are determined. The NMR data, namely, nuclear overhauser enhancement (NOE) correlations, pointed out two conformations of guaianolide's cycloheptane ring. The semiempirical calculations (AM1 and PM3 methods), performed in order to gain additional information regarding conformations, resulted in three geometries of investigated lactones. Even so, the conformations derived from the NMR data agreed well with those calculated by semiempirical methods. Copyright © 2008 John Wiley & Sons, Ltd.
3D MR flow analysis in realistic rapid‐prototyping model systems of the thoracic aorta: Comparison with in vivo data and computational fluid dynamics in identical vessel geometries
Authors: Canstein C. , Cachot P. , Faust A. , Stalder A.F. , Bock J. , Frydrychowicz A. , Küffer J. , Hennig J. , Markl M.
Published: February 2008

The knowledge of local vascular anatomy and function in the human body is of high interest for the diagnosis and treatment of cardiovascular disease. A comprehensive analysis of the hemodynamics in the thoracic aorta is presented based on the integration of flow‐sensitive 4D MRI with state‐of‐the‐art rapid prototyping technology and computational fluid dynamics (CFD). Rapid prototyping was used to transform aortic geometries as measured by contrast‐enhanced MR angiography into realistic vascular models with large anatomical coverage. Integration into a flow circuit with patient‐specific pulsatile in‐flow conditions and application of flow‐sensitive 4D MRI permitted detailed analysis of local and global 3D flow dynamics in a realistic vascular geometry. Visualization of characteristic 3D flow patterns and quantitative comparisons of the in vitro experiments with in vivo data and CFD simulations in identical vascular geometries were performed to evaluate the accuracy of vascular model systems. The results indicate the potential of such patient‐specific model systems for detailed experimental simulation of realistic vascular hemodynamics. Further studies are warranted to examine the influence of refined boundary conditions of the human circulatory system such as fluid‐wall interaction and their effect on normal and pathological blood flow characteristics associated with vascular geometry. Magn Reson Med 59:535–546, 2008. © 2008 Wiley‐Liss, Inc.
Designing multichannel, multidimensional, arbitrary flip angle RF pulses using an optimal control approach
Authors: Xu Dan , King Kevin F. , Zhu Yudong , McKinnon Graeme C. , Liang Zhi‐Pei
Published: February 2008

The vast majority of parallel transmission RF pulse designs so far are based on small‐tip‐angle (STA) approximation of the Bloch equation. These methods can design only excitation pulses with small flip angles (e.g., 30°). The linear class large‐tip‐angle (LCLTA) method is able to design large‐tip‐angle parallel transmission pulses through concatenating a sequence of small‐excitation pulses when certain k‐space trajectories are used. However, both STA and LCLTA are linear approximations of the nonlinear Bloch equation. Therefore, distortions from the ideal magnetization profiles due to the higher order terms can appear in the final magnetization profiles. This issue is addressed in this work by formulating the multidimensional multichannel RF pulse design as an optimal control problem with multiple controls based directly on the Bloch equation. Necessary conditions for the optimal solution are derived and a first‐order gradient optimization algorithm is used to iteratively solve the optimal control problem, where an existing pulse is used as an initial “guess.” A systematic design procedure is also presented. Bloch simulation and phantom experimental results using various parallel transmission pulses (excitation, inversion, and refocusing) are shown to illustrate the effectiveness of the optimal control method in improving the spatial localization or homogeneity of the magnetization profiles. Magn Reson Med 59:547–560, 2008. © 2008 Wiley‐Liss, Inc.
Deriving blood‐oxygen‐level‐dependent contrast in MRI with T‐weighted, T2‐prepared and phase‐cycled SSFP methods: Theory and experiment
Authors: Arumana Jain Mangalathu , Li Debiao , Dharmakumar Rohan
Published: February 2008

The objectives of this work were: 1) to perform a comparative evaluation of the oxygen‐sensitive contrast (OC) derived from the phase‐cycled steady‐state free precession (SSFPPC) method against T*2‐weighted gradient recalled echo (GRE) and T2‐prepared (T2‐prep) methods with theoretical simulations and imaging studies using an ischemic leg cuff model at 1.5T and 3.0T; and 2) to investigate the dependence of SSFPPC‐based OC on imaging parameters. Results showed that the SSFPPC method (repetition time (TR) = 6.3 ms; flip angle (α) = 90°) provides significantly higher OC compared to T2‐prep (at both field strengths) and GRE (3.0T) (P < 0.05). The OC of low TR SSFP (TR = 3.5 ms at 1.5T; TR = 4.5 ms at 3.0T; α = 90°) was significantly lower compared to GRE (P < 0.05) at 1.5T and 3.0T and to T2‐prep methods at 1.5T (P < 0.05). In summary, the findings from this study are the following: 1) SSFP‐based OC is directly dependent on TR and α at 1.5T and 3.0T; and 2) OC derived with SSFPPC can be increased above GRE and T2‐prep methods with an appropriate choice of imaging parameters. Magn Reson Med 59:561–570, 2008. © 2008 Wiley‐Liss, Inc.
Joint estimation of water/fat images and field inhomogeneity map
Authors: Hernando D. , Haldar J. P. , Sutton B. P. , Ma J. , Kellman P. , Liang Z.‐P.
Published: February 2008

Water/fat separation in the presence ofB0field inhomogeneity is a problem of considerable practical importance in MRI. This article describes two complementary methods for estimating the water/fat images and the field inhomogeneity map from Dixon‐type acquisitions. One is based on variable projection (VARPRO) and the other on linear prediction (LP). The VARPRO method is very robust and can be used in low signal‐to‐noise ratio conditions because of its ability to achieve the maximum‐likelihood solution. The LP method is computationally more efficient, and is shown to perform well under moderate levels of noise and field inhomogeneity. These methods have been extended to handle multicoil acquisitions by jointly solving the estimation problem for all the coils. Both methods are analyzed and compared and results from several experiments are included to demonstrate their performance. Magn Reson Med 59:571–580, 2008. © 2008 Wiley‐Liss, Inc.
Synthesis of poly(glycidol)‐block‐poly(N‐isopropylacrylamide) copolymers using new hydrophilic poly(glycidol) macroinitiator
Authors: Mendrek Sebastian , Mendrek Aleksandra , Adler Hans‐Jürgen , Walach Wojciech , Dworak Andrzej , Kuckling Dirk
Published: February 2008

New, water soluble poly(glycidol) (PGl) macroinitiators for atom transfer radical polymerization (ATRP) were synthesized. This new class of macroinitiators were prepared in a three‐step process. First, series of well‐defined ω‐hydroxyl functional poly(glycidol acetal)s with different molecular weights was synthesized via anionic polymerization followed by quantitative termination of anionically growing active sites. End capping was achieved by treatment of living chain ends with water. The living nature of the system and termination reaction is discussed. In the second stage, monofunctional poly(glycidol acetal)s were functionalized by esterification with 2‐chloropropionyl chloride. Finally, selective deprotection (hydrolysis) of acetal protective groups was performed. As simultaneous partial cleavage of ester bond of attached ATRP moieties was unavoidable, the final functionality of macroinitiator calculated from 1H NMR varied in the range 85–95%. The obtained (2‐chloropropionyl) poly(glycidol) macroinitiator with DP = 55 and 90% functionality was successfully used in ATRP polymerization of N‐isopropylacrylamide (NIPAAm) at room temperature in the DMF/water mixture. Linear block copolymers with relatively narrow molecular weight distribution and controlled composition were obtained and characterized with 1H NMR and SEC‐MALLS measurements. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2488–2499, 2008
Local chemical state change in Co–O resistance random access memory
Authors: Shima Hisashi , Takano Fumiyoshi , Muramatsu Hidenobu , Yamazaki Masashi , Akinaga Hiroyuki , Kogure Akinori
Published: February 2008

Kelvin probe force microscopy (KFM) and conductive atomic force microscopy (C‐AFM) together with micro X‐ray photoelectron spectroscopy (XPS) were performed for the stacking structure comprising of the transition metal oxide Co–O and metal electrode, which exhibits large reproducible resistance switching. The application of the external voltage by the C‐AFM cantilever decreases the resistance of Co–O, which well accords with the non‐polar forming process observed in the Pt/Co–O/Pt trilayer, known as the candidate of resistance random access memory (ReRAM). Furthermore, the KFM and micro XPS experimentally revealed that the local reductive reaction of Co–O possibly nucleates the defect related energy levels which dominates the current conduction in the low resistance state. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Antecedent alluvial morphology and sea‐level controls on form‐process transition zones in the lower Trinity river, Texas
Authors: Phillips J. D. , Slattery M. C.
Published: February 2008

An important aspect of river science and management is the identification of key boundaries, transition zones and hinge points. Such critical areas are likely to be important foci or indicators of the effects of environmental change on river systems. While geological controls on such features are widely recognized in upland streams, inherited or antecedent forms may also be important controls of key transitional points or reaches in alluvial coastal plain rivers. The critical zone of the lower Trinity River, Texas marks an important transition in river channel and valley forms, dominant processes and resulting geomorphological, hydrological and ecological characteristics. Its location is not a transient result of upstream or downstream propagation of effects. Rather, the location marks the contemporary upstream extent of the effects of Holocene sea‐level rise, which in turn coincides with the point at which the Pleistocene upper Deweyville alluvial terrace surface is encountered. A more rapid rate of change and relatively sudden upstream displacement of this zone is likely when the upper Deweyville surface is flooded. Antecedent fluvial and alluvial topography inherited from previous aggradation, degradation and lateral migration episodes is likely to be an important control over modern fluvial forms and processes in other alluvial coastal plain rivers as well. Identification and mapping of such features may be extremely useful in pinpointing critical transition zones for water resource managers. Copyright © 2008 John Wiley & Sons, Ltd.
Ultrasound‐guided culdotomy for vaginal ovarian cystectomy using a renal balloon dilator catheter
Authors: Tanaka M. , Sagawa T. , Hashimoto M. , Mizumoto Y. , Yoshimoto H. , Yamazaki R. , Kasai T. , Inoue M.
Published: February 2008

Objectives

To evaluate the feasibility and utility of performing ultrasound‐guided culdotomy using a renal balloon dilator catheter for transvaginal ovarian cystectomies.

Methods

Culdotomy using transvaginal sonography and a Nephromax™ balloon dilator catheter was performed in 16 patients for the vaginal removal of benign ovarian cysts located in the cul‐de‐sac. Each ovarian cyst was punctured under transvaginal ultrasound guidance and the punctured site on the vaginal wall was enlarged with a dilator. The cyst was then enucleated through this vaginal wound. Preoperative characteristics of the patients, outcome, operating time, blood loss and complications of each culdotomy, and the histology of the cysts, were recorded and examined.

Results

We used this method on 14 patients with unilateral ovarian cysts and two with bilateral cysts. Culdotomy was performed successfully in 15 cases (94%). The mean ± SD operating time for culdotomy was 22 ± 11 min, and blood loss during the procedure was less than 10 mL in all cases. There were no complications including rectal injury or febrile morbidity.

Conclusions

Culdotomy assisted by ultrasound imaging and a dilator is a safe, reliable and effective method for removal of benign ovarian cysts via a vaginal approach. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.
Cross‐layer design for energy efficient communication in wireless sensor networks
Authors: Lin Xiao‐Hui , Kwok Yu‐Kwong , Wang Hui
Published: February 2008

There is a plethora of recent research on high performance wireless communications using a cross‐layer approach in that adaptive modulation and coding (AMC) schemes at wireless physical layer are used for combating time varying channel fading and enhance link throughput. However, in a wireless sensor network, transmitting packets over deep fading channel can incur excessive energy consumption due to the usage of stronger forwarding error code (FEC) or more robust modulation mode. To avoid such energy inefficient transmission, a straightforward approach is to temporarily buffer packets when the channel is in deep fading, until the channel quality recovers. Unfortunately, packet buffering may lead to communication latency and buffer overflow, which, in turn, can result in severe degradation in communication performance. Specifically, to improve the buffering approach, we need to address two challenging issues: (1) how long should we buffer the packets? and (2) how to choose the optimum channel transmission threshold above which to transmit the buffered packets? In this paper, by using discrete‐time queuing model, we analyze the effects of Rayleigh fading over AMC‐based communications in a wireless sensor network. We then analytically derive the packet delivery rate and average delay. Guided by these numerical results, we can determine the most energy‐efficient operation modes under different transmission environments. Extensive simulation results have validated the analytical results, and indicates that under these modes, we can achieve as much as 40% reduction in energy dissipation. Copyright © 2008 John Wiley & Sons, Ltd.
Involvement of PPARα in the growth inhibitory effect of arachidonic acid on breast cancer cells
Authors: Bocca Claudia , Bozzo Francesca , Martinasso Germana , Canuto Rosa Angela , Miglietta Antonella
Published: February 2008

Epidemiological studies suggest that dietary PUFA may influence breast cancer progression.n-3 PUFA are generally known to exert antitumour effects, whereas reports relative ton-6 PUFA anti-carcinogen effects are controversial. Arachidonic acid (AA; 20 : 4n − 6) and its metabolites have been shown to inhibit the growth of human breast cancer cell lines, even if the downstream mechanisms by which AA may influence carcinogenesis remain unresolved. We explored the molecular basis for AA influence on proliferation, signal transduction and apoptosis in two human breast cancer cell lines, MCF-7 and MDA-MB-231. In both cell lines AA inhibited cell growth in a dose-dependent manner, even if MDA-MB-231 was somewhat more growth-inhibited than MCF-7. AA decreased extracellular signal-regulated protein kinase 1/2 phosphorylation level, and positively modulated PPARγ and PPARα expression, with only a slight effect against PPARβ/δ. In addition, AA increased Bak (an apoptosis-regulating protein) expression and reduced procaspase-3 and -9 levels only in MDA-MB-231 cells, thus indicating that the growth inhibitory effect can be correlated with apoptosis induction. In both cell lines the use of a specific antagonist made it possible to establish a relationship between AA growth inhibitory effect and PPARα involvement. AA decreases cell proliferation most likely by inducing apoptosis in MDA-MB-231 cells, while in the MCF-7 cell line the growth inhibitory activity can be attributed to the inhibition of the signal transduction pathway involved in cell proliferation. In both cases, the results here presented suggest PPARα as a possible contributor to the growth inhibitory effect of AA.
How Much Can a Victor Force the Vanquished to Pay? France under the Nazi Boot
Authors: OCCHINO FILIPPO , OOSTERLINCK KIM , WHITE EUGENE N.
Published: February 2008

Occupation charges paid by France to Nazi Germany represent one of the largest international transfers and contributed significantly to the German war effort. We employ a neoclassical growth model that incorporates essential features of the occupied economy to assess the welfare costs of the policies that managed the payments to Germany. Our lower bound estimates show that occupation payments required a severe cut in consumption. A draft of labor to Germany and a reduction of real wages added to this burden. Management of the accumulated domestic debt required large budget surpluses; but post-Liberation inflation slashed the real debt.

“Ils ne nous ont rien enlevé de vive force; ils ont toujours tout acheté correctement; mais ils nous ont tout payé avec de l'argent qu'ils nous avaient volé.”1
Can Civil Law Countries Get Good Institutions? Lessons from the History of Creditor Rights and Bond Markets in Brazil
Authors: MUSACCHIO ALDO
Published: February 2008

Does a legal tradition adopted in the distant past constrain a country's ability to provide the protection that investors need for financial markets to develop? I look at the relationship between legal origin and the development of bond markets and find too much variation over time in bond market size, creditor protections, and court enforcement of bond contracts to assume that the adoption of a legal system constrains future financial development. I examine the evolution of bond markets in Brazil, a French civil law country, and provide preliminary results of similar variation for a small cross-section of countries.
Mechanismen der Interferenz in Doppelaufgaben
Authors: Koch Iring
Published: February 2008

Zusammenfassung. Wenn man zwei Aufgaben gleichzeitig bearbeitet, dann kommt es im Vergleich zur Bearbeitung nur einer Aufgabe zumeist zu einer Leistungsverschlechterung (Interferenz). Die vorliegende Arbeit befasst sich mit den Mechanismen der Doppelaufgaben-Interferenz bei der zeitlich überlappenden Bearbeitung von recht elementaren kognitiven Aufgaben (z.B. auf einen Ton eine Taste drücken). Diese Mechanismen werden typischerweise mit dem “Psychologische Refraktärperioden“ (PRP)-Paradigma untersucht. Traditionelle Erklärungen für Doppelaufgaben-Interferenz gehen von einem zentralen Verarbeitungsengpass auf der Ebene der Entscheidung und Reaktionsauswahl aus. Neuere empirische Befunde legen jedoch nahe, dass Doppelaufgaben-Interferenz auch in bezug auf andere Verarbeitungsprozesse auftritt, wie etwa das Enkodieren und Abrufen von Information im Kurzzeitgedächtnis sowie die kognitive Steuerung der Aufgabenabfolge. Diese Vielfalt der Mechanismen der Doppelaufgaben-Interferenz erfordert eine deutliche Erweiterung traditioneller theoretischer Rahmenvorstellung. Diese Erweiterung lässt auch den Umgang mit angewandten Doppelaufgaben-Problemen (z.B. Telefonieren beim Autofahren) in einem neuen Licht erscheinen.
Vertrauensgenese in virtuellen Netzwerken:
Authors: Vollmer Albert , Wehner Theo , Clases Christoph
Published: February 2008

Zusammenfassung. In diesem Beitrag berichten wir auf der Basis einer empirischen Studie über die Bedeutsamkeit von vertrauensrelevanten Charakteristika in einem virtuellen Netzwerk. Aufbauend auf eine Repertory-Grid-Studie von Clases, Bachmann und Wehner (2003) zur Erhebung von persönlichen Konstrukten über die Vertrauensgenese, wurde ein Fragebogen mit Aussagen über vertrauensrelevante Charakteristika von Netzwerken entwickelt. Damit wurde untersucht, inwieweit diese Charakteristika für die Eintritts- und Austrittsentscheidung sowie für den Prozess der Beteiligung am Netzwerk relevant sind. Die Ergebnisse zeigen, dass vertrauensrelevante Netzwerkcharakteristika, die bei der Eintrittsentscheidung eine wichtige Rolle spielen, auch potenzielle Austrittsgründe darstellen. Zudem kann gezeigt werden, dass die Netzwerkpartner sich in hohem Maße darauf verlassen, dass vertrauensrelevante Netzwerkcharakteristika erst im Prozess der Beteiligung tatsächlich auftreten. Im Hinblick auf die Vertrauensgenese bedeutet dies, dass Vertrauen zwar erst im Rahmen der konkreten Beteiligung entstehen kann, aber bereits bei der Eintrittsentscheidung eine Rolle spielt, und dass nicht eingelöstes Vertrauen zur Beendigung der Zusammenarbeit führen kann. In methodologischer Hinsicht wurden mit der Studie neue Wege zur Untersuchung von Vertrauen in virtuellen Unternehmensnetzwerken exploriert, welche kritisch zu reflektieren sind.
Impact of ice temperature on microwave emissivity of thin newly formed sea ice
Authors: Hwang Byong Jun , Ehn Jens K. , Barber David G.
Published: February 2008

This study examines the impact of ice temperature on microwave emissivity over thin, newly formed sea ice at 6, 19, and 37 GHz during October 2003 in the southern Beaufort Sea, where the physical properties of newly formed sea ice were coincidently measured with microwave emissions. Six ice stations with distinct properties were selected and divided according to ice surface temperature into warm (above –3°C) or cold (below –3°C) stations. The warm stations had a lower emissivity at the vertical polarization by 0.1 than the cold stations and a corresponding difference in brine volume and dielectric properties. Significant correlations were observed between brine volume and ice emissivity (R2 = 0.8, p value < 0.05). A sensitivity study showed that decreasing ice temperatures from −2.1° to −5.0°C explained the observed difference of 0.1 in ice emissivity between warm and cold stations. The results suggest that the temperature of thin bare ice could be the critical factor in determining ice emissivity near the melting point (about −2°C). Furthermore, a slight decrease in ice temperature (i.e., from −2° to −5°C) significantly reduces the brine volume, thus resulting in high ice emissivity. Finally, we demonstrate the potential of newly formed ice to cause errors in estimating sea ice concentrations using Advanced Microwave Scanning Radiometer–E data.
Pop‐up tectonics of the Shillong Plateau in the great 1897 earthquake (Ms8.7): Insights from the gravity in conjunction with the recent seismological results
Authors: Nayak Goutam Kumar , Rao V. K. , Rambabu H. V. , Kayal J. R.
Published: February 2008

It was reported that a hidden 110‐km‐long south‐dipping fault, named Oldham Fault, was responsible for the 1897 great earthquake (Ms8.7) in the Shillong Plateau by reverse faulting due to ‘pop‐up’ tectonics of the plateau in northeast India. Here we report the results of our geophysical investigations, where we critically examine the crustal structure of the plateau on the basis of gravity modeling and attempt to shed light on the hitherto debated hidden Oldham Fault at the northern boundary of the Shillong Plateau. Our gravity model, constrained by broadband seismological data, suggests that the Moho beneath the Shillong Plateau is at a shallower depth of about 35 km when compared to the Bengal basin to the south and the Assam valley to the north, which is about 42 km. Thinning of the crust under the plateau may be a consequence of the ‘pop‐up’ mechanism. To examine the possible ‘pop‐up’ of the plateau during the great 1897 earthquake, we have estimated the energy released by this earthquake and compared it with the energy required for the ‘pop‐up’ of the plateau, using a simplistic rigid model. It is found that the Shillong Plateau between the Oldham Fault and Dauki‐Dapsi Thrust would require an energy of 4.5 × 1019J, which does match well with the energy released by the great earthquake of Ms= 8.7.
Spring to summer northward migration of high O3 over the western North Atlantic
Authors: Choi Yunsoo , Wang Yuhang , Yang Qing , Cunnold Derek , Zeng Tao , Shim Changsub , Luo Ming , Eldering Annmarie , Bucsela Eric , Gleason James
Published: February 2008

Tropospheric O3 columns retrieved from OMI and MLS measurements, NO2 columns from OMI, and upper tropospheric O3 concentrations from TES over North America and the western North Atlantic from April to August 2005 are analyzed using the Regional chEmical and trAnsport Model (REAM). Large enhancements of column and upper tropospheric O3 over the western North Atlantic comparable to those over the eastern United States are found in the satellite measurements and REAM simulations. The O3 enhancement region migrates northward from spring to summer. Model analysis indicates that the northward migration is driven by seasonal shifts of O3 transported from the stratosphere and that produced through photochemistry from surface emissions and lightning NOx. As their uncertainties improve, satellite measurements of O3 and its precursors will be able to provide more quantitative constraints on pollutant outflow from the continents.
Structure and growth of the Izu‐Bonin‐Mariana arc crust: 2. Role of crust‐mantle transformation and the transparent Moho in arc crust evolution
Authors: Tatsumi Y. , Shukuno H. , Tani K. , Takahashi N. , Kodaira S. , Kogiso T.
Published: February 2008

Evolution of arc crust and subarc mantle in the Izu‐Bonin‐Mariana (IBM) intraoceanic arc‐trench system is examined by petrological modeling of arc magma generation and differentiation. Characteristic seismic structural features of the IBM arc highlighted in this modeling include the presence of (1) a middle crust with a P wave velocity (Vp) of 6.0–6.5 km/s, (2) a 6.5–6.8 km/s Vp layer at the top of the lower crust, (3) a high‐velocity (Vp = 6.8–7.2 km/s) lower crust, and (4) an uppermost mantle exhibiting rather low velocities (Vp = 7.4–7.7 km/s). The formation of the middle crust, which is considered to have an intermediate composition, is examined by (1) the mantle‐derived basalt model including anatexis of the initial mafic lower crust or mixing of mantle‐melting‐derived basaltic magma with crust‐melting‐derived felsic magma and (2) the mantle‐derived andesite model including differentiation of boninitic magma. The Vp calculated for the inferred compositions for each layer of the IBM crust on the basis of the basalt model is consistent with the observed values, whereas the andesite model cannot account for the characteristic Vp of the middle crust, the uppermost lower crust, and the uppermost mantle. The results further suggest that the volume of mafic restite and cumulates that are “crustal residues” resulting from the evolution of middle and upper arc crust is, at least, 3 to 9 times greater than that of the seismically defined IBM lower crust. One possible explanation to overcome this apparent dilemma is that the mafic to ultramafic crustal components are transformed to subarc mantle. During this process the subarc Moho is chemically transparent and permeable to the crustal components. This crust‐mantle transformation could play the major role in the creation of mature arc crust with intermediate compositions similar to continental crust.
Large‐eddy simulation of oscillating boundary layers: Model comparison and validation
Authors: Radhakrishnan Senthilkumaran , Piomelli Ugo
Published: February 2008

Large‐eddy simulations of oscillating boundary layers over smooth and rough walls in the fully turbulent regime have been carried out. Several models for the unresolved subgrid‐scale (SGS) stresses are compared, as well as different approximate treatments of the wall layer, where none of the momentum‐transporting eddies is resolved. The simulations show that the use of advanced SGS models coupled with approximate boundary conditions can predict the flow successfully. Dynamic SGS eddy‐viscosity models yield more accurate results than the fixed‐coefficient one, which yields an excessively large SGS eddy viscosity, damping the wall‐normal fluctuations. The shifted logarithmic‐law approximate boundary condition, which accounts for the inclination of the near‐wall eddies, results in prediction of the wall stress within 3% of the experimental data throughout the cycle. The standard logarithmic law also gives adequate results, with a maximum error of 6%. A modification of the rough‐wall logarithmic law that accounts for transitional roughness effects was also tested; at this Reynolds number, however, this correction made little difference in the numerical results.
Description and validation of a limb scatter retrieval method for Odin/OSIRIS
Authors: Tukiainen S. , Hassinen S. , Seppälä A. , Auvinen H. , Kyrölä E. , Tamminen J. , Haley C. S. , Lloyd N. , Verronen P. T.
Published: February 2008

In this paper we present the Modified Onion Peeling (MOP) inversion method, which is for the first time used to retrieve vertical profiles of stratospheric trace gases from Odin/OSIRIS limb scatter measurements. Since the original publication of the method in 2002, the method has undergone major modifications discussed here. The MOP method now uses a spectral microwindow for the NO2 retrieval, instead of the wide UV‐visible band used for the ozone, air, and aerosol retrievals. We give a brief description of the algorithm itself and show its performance with both simulated and real data. Retrieved ozone and NO2 profiles from the OSIRIS measurements were compared with data from the GOMOS and HALOE instruments. No more than 5% difference was found between OSIRIS daytime and GOMOS nighttime ozone profiles between 21 and 45 km. The difference between OSIRIS and HALOE sunset NO2 mixing ratio profiles was at most 25% between 20 and 40 km. The neutral air density was compared with the ECMWF analyzed data and around 5% difference was found at altitudes from 20 to 55 km. However, OSIRIS observations yield as much as 80% greater aerosols number density than GOMOS observations between 15 and 35 km. These validation results indicate that the quality of MOP ozone, NO2, and neutral air is good. The new version of the method introduced here is also easily expanded to retrieve additional species of interest.
Simulations of Arctic mixed‐phase clouds in forecasts with CAM3 and AM2 for M‐PACE
Authors: Xie Shaocheng , Boyle James , Klein Stephen A. , Liu Xiaohong , Ghan Steven
Published: February 2008

Simulations of mixed‐phase clouds in forecasts with the NCAR Atmosphere Model version 3 (CAM3) and the GFDL Atmospheric Model version 2 (AM2) for the Mixed‐Phase Arctic Cloud Experiment (M‐PACE) are performed using analysis data from numerical weather prediction centers. CAM3 significantly underestimates the observed boundary layer mixed‐phase cloud fraction and cannot realistically simulate the variations of liquid water fraction with temperature and cloud height due to its oversimplified cloud microphysical scheme. In contrast, AM2 reasonably reproduces the observed boundary layer cloud fraction while its clouds contain much less cloud condensate than CAM3 and the observations. The simulation of the boundary layer mixed‐phase clouds and their microphysical properties is considerably improved in CAM3 when a new physically based cloud microphysical scheme is used (CAM3LIU). The new scheme also leads to an improved simulation of the surface and top of the atmosphere longwave radiative fluxes. Sensitivity tests show that these results are not sensitive to the analysis data used for model initialization. Increasing model horizontal resolution helps capture the subgrid‐scale features in Arctic frontal clouds but does not help improve the simulation of the single‐layer boundary layer clouds. AM2 simulated cloud fraction and LWP are sensitive to the change in cloud ice number concentrations used in the Wegener‐Bergeron‐Findeisen process while CAM3LIU only shows moderate sensitivity in its cloud fields to this change. This paper shows that the Wegener‐Bergeron‐Findeisen process is important for these models to correctly simulate the observed features of mixed‐phase clouds.
Environmental drivers of spatial variation in whole‐tree transpiration in an aspen‐dominated upland‐to‐wetland forest gradient
Authors: Loranty Michael M. , Mackay D. Scott , Ewers Brent E. , Adelman Jonathan D. , Kruger Eric L.
Published: February 2008

Assumed representative center‐of‐stand measurements are typical inputs to models that scale forest transpiration to stand and regional extents. These inputs do not consider gradients in transpiration at stand boundaries or along moisture gradients and therefore potentially bias the large‐scale estimates. We measured half‐hourly sap flux (JS) for 173 trees in a spatially explicit cyclic sampling design across a topographically controlled gradient between a forested wetland and upland forest in northern Wisconsin. Our analyses focused on three dominant species in the site: quaking aspen (Populus tremuloides Michx), speckled alder (Alnus incana (DuRoi) Spreng), and white cedar (Thuja occidentalis L.). Sapwood area (AS) was used to scale JS to whole tree transpiration (EC). Because spatial patterns imply underlying processes, geostatistical analyses were employed to quantify patterns of spatial autocorrelation across the site. A simple Jarvis type model parameterized using a Monte Carlo sampling approach was used to simulate EC (EC−SIM). EC−SIM was compared with observed EC(EC−OBS) and found to reproduce both the temporal trends and spatial variance of canopy transpiration. EC−SIM was then used to examine spatial autocorrelation as a function of environmental drivers. We found no spatial autocorrelation in JS across the gradient from forested wetland to forested upland. EC was spatially autocorrelated and this was attributed to spatial variation in AS which suggests species spatial patterns are important for understanding spatial estimates of transpiration. However, the range of autocorrelation in EC−SIM decreased linearly with increasing vapor pressure deficit, implying that consideration of spatial variation in the sensitivity of canopy stomatal conductance to D is also key to accurately scaling up transpiration in space.
Escherichia colitranscription factor YncC (McbR) regulates colanic acid and biofilm formation by repressing expression of periplasmic protein YbiM (McbA)
Authors: Zhang Xue-Song , García-Contreras Rodolfo , Wood Thomas K
Published: February 2008

Quorum-sensing signal autoinducer 2 (AI-2) stimulates Escherichia coli biofilm formation through the motility regulator MqsR that induces expression of the putative transcription factor encoded by yncC. Here, we show that YncC increases biofilm formation by repressing overproduction of the exopolysaccharide identified as colanic acid (corroborated by decreasing mucoidy and increased sensitivity to bacteriophage P1 infection). Differential gene expression and gel shift assays demonstrated that YncC is a repressor of the predicted periplasmic protein-encoding gene, ybiM, which was corroborated by the isogenic yncC ybiM double mutation that repressed the yncC phenotypes (biofilm formation, colanic acid overproduction, mucoidy and bacteriophage resistance). Through nickel-enrichment DNA microarrays and additional gel shift assays, we found that the putative transcription factor B3023 (directly upstream of mqsR) binds the yncC promoter. Overexpressing MqsR, AI-2 import regulators LsrR/LsrK and AI-2 exporter TqsA induced yncC transcription, whereas the AI-2 synthase LuxS and B3023 repressed yncC. MqsR has a toxic effect on E. coli bacterial growth, which is partially reduced by the b3023 mutation. Therefore, AI-2 quorum-sensing control of biofilm formation is mediated through regulator MqsR that induces expression of the transcription factor YncC. YncC inhibits the expression of periplasmic YbiM, which prevents overproduction of colanic acid (excess colanic acid causes mucoidy) and prevents YbiM from inhibiting biofilm formation.
Substrate-induced growth and isolation of Acidobacteria from acidic Sphagnum peat
Authors: Pankratov Timofei A , Serkebaeva Yulia M , Kulichevskaya Irina S , Liesack Werner , Dedysh Svetlana N
Published: February 2008

Fluorescence in situ hybridization (FISH) was applied to estimate the population size of the poorly characterized phylum Acidobacteria in acidic peat sampled from nine different Sphagnum-dominated wetlands of Northern Russia. The cell numbers of these bacteria in oxic peat layers ranged from 0.4 × 106 to 1.3 × 107 cells per g of wet peat, comprising up to 4% of total bacterial cells. Substrate-induced growth of acidobacteria was observed after amendment of peat samples with glucose, pectin, xylan, starch, ethanol and methanol, while weak or no response was obtained for acetate, pyruvate, mannitol and cellobiose. Using low-nutrient media and FISH-mediated monitoring of the isolation procedure, we succeeded in obtaining nine strains of acidobacteria in pure cultures. These strains belonged to subdivisions 1 and 3 of the Acidobacteria and represented strictly aerobic, heterotrophic organisms. Except for methanol, the substrate utilization patterns of these isolates matched the results obtained in our substrate-amendment experiments with native peat. All strains were also capable of utilizing galacturonic acid, a characteristic component of the cell wall in Sphagnum spp, which is released during moss decomposition. Most isolates from subdivision 1 were truly acidophilic organisms with the growth optimum at pH 3.5–4.5, while the isolates from subdivision 3 grew optimally at pH 5.5–6.5. Another important phenotypic trait of novel strains was their capability of active growth at low temperatures. Both acidophily and low-temperature growth are consistent with the occurrence of acidobacteria in cold and acidic northern wetlands.
Effects of Gastric Electric Stimulation on Gastric Distention Responsive Neurons and Expressions of CCK in Rodent Hippocampus
Authors: Xu Luo , Sun Xiangrong , Lu Jiang , Tang Ming , Chen J.D.Z.
Published: February 2008

Objective: Gastric electrical stimulation (GES) has been introduced for treating obesity. The hippocampus is known to be involved in the regulation of gastrointestinal motility. Changes in hypathalumus cholecystokinin (CCK) have been observed in genetically obese rodents. This experiment was to study the effect of GES on the activities of neurons and the expression of CCK in the hippocampus.

Methods and Procedures: We investigated the effect of GES (GES‐I: pulse train of standard parameters; GES‐2: reduced train‐on time; GES‐3: increased pulse width; GES‐4: reduced pulse frequency) on neurons responsive to gastric distention (GD) by recording extracellular potentials of single neurons and observing the expression of CCK in the rodent hippocampus by immunohistochemistry staining, radioimmunoassay, and real‐time PCR.

Results: 92.1% of neurons in the CA2‐3 region responded to GD, 53.2% of which showed excitation (GD‐E), and 46.8% showed inhibition (GD‐I). 64.8% GD‐responsive neurons were excited by GES. The response was associated with stimulation strength, pulse width, and frequency; 70.6, 57.1, 94.4, and 66.7% of GD‐E and 72.7, 57.1, 86.4, and 50% of GD‐I neurons showed excitatory responses to GES‐I, −2, −3, and −4, respectively. CCK immunoreactive positive neurons (P < 0.001), the content of CCK‐like materials (P < 0.05) and the amount of CCK mRNA were significantly increased after GES (P < 0.05).

Discussion: These findings suggest the central, neuronal, and hormonal mechanisms of GES. GES may excite the activity of GD‐sensitive neurons and increase the expression of CCK in the hippocampus. These excitatory effects of GES seem to be related to the parameters of stimulation.
The inflection point in the pressure dependence of viscosity under high pressure: A comprehensive study of the temperature and pressure dependence of the viscosity of propylene carbonate
Authors: Casalini R. , Bair S.
Published: February 2008

The pressure dependence of the prototypical glass-former propylene carbonate has been investigated over a broad range of temperature and pressure that were inaccessible in previous investigations using dielectric spectroscopy. We find that the viscosity measurements validate the scaling relation, η(T,V)=I(TVγ), with a scaling parameter γ close to that found from dielectric relaxation measurements. In the pressure dependence of the viscosity, we observe an inflection point in the log(η) versus P response, similar to that found previously for other materials. However, this inflection has never been observed in dielectric relaxation measurements. Using the scaling property above, it is possible to determine the behavior of the dielectric relaxation time in this otherwise inaccessible experimental range and compare it with the viscosity measurements. We find that the behaviors of η and τ are very similar, and a very good agreement between the function ϕP calculated for these two quantities is found. Starting from the validity of the scaling properties, we show that the inflection point in the pressure dependence of the viscosity can be attributed to the convolution of the pressure dependences of the compressibility κT and the apparent activation energy at constant volume EV.
Nonadiabatic effects in the photodetachment of ClH2−
Authors: Alexander Millard H. , Kłos Jacek , Manolopoulos David E.
Published: February 2008

The photoelectron spectra of the ClH2− and ClD2− anions have been simulated using a Franck–Condon model involving vertical excitation to the four coupled quasidiabatic potential energy surfaces that correlate with Cl(P2)+H2(Σg+1). A careful analysis of the excitation process is presented. All electrostatic, spin-orbit, and Coriolis couplings in the photodetached ClH2 (ClD2) neutral are included. At a resolution of 1meV, the resulting spectra are dominated by the bound and resonant states of the Cl⋯H2 and Cl⋯D2 van der Waals complexes, along with contributions from the associated continua. Only small differences occur between these spectra and those simulated under the assumption that each of the three electronically adiabatic Cl(P2)+H2 states can be treated separately. In particular, photodetachment to form the Cl*(P1∕22)H2 complex leads to very low intensity of spectral features associated with Cl(P3∕22)H2. This clearly implies that, while nonadiabatic effects do have some influence on the bound and resonance state energies of both complexes as shown recently by Garand et al. [Science 319, 72 (2008)], nonadiabatic transitions between the two complexes are extremely rare.
Metamagnetic transition and extremely large low field magnetocaloric effect in La0.7Ca0.3MnO3 manganite
Authors: Ulyanov A. N. , Kang Y. M. , Yoo S. I.
Published: February 2008

Metamagnetic transition was observed in low magnetic field for La0.7Ca0.3MnO3−δ lanthanum manganite prepared by solid-state technology. Magnetization shape causes giant low field magnetocaloric effect at Curie temperature TC=242K. Magnetic entropy changes ΔSm, deduced with isothermal magnetization curves, are equal to 7.0 and 8.0J∕kgK in the field change from 0 to 1.0 and 2.0T, respectively. The obtained ΔSm are essentially higher than that reported before for lanthanum manganites with similar TC. The observation shows the way for the construction the magnetic refrigerants, working in the field of permanent magnets, which is beneficial for household and automotive applications.
Inhomogeneity in Co doped ZnO diluted magnetic semiconductor
Authors: Sanyal B. , Knut R. , Grånäs O. , Iuşan D. M. , Karis O. , Eriksson O.
Published: February 2008

Here, we have studied the chemical and magnetic interactions in Co doped ZnO diluted magnetic semiconductor by ab initio density functional calculations. The calculated chemical pair interaction parameters suggest a strong tendency of clustering between Co atoms. Both chemical and magnetic pair interaction parameters are short ranged with a large first neighbor interaction. Monte Carlo simulations show that the Curie temperature for a homogeneous sample is low, whereas allowing for an inhomogeneous growth results in very high Curie temperatures. It is argued that these inhomogeneities may be the reason for the observation of high Curie temperatures in Co doped ZnO. It is also demonstrated that the electronic structure is modified significantly in presence of Co clusters.
Molecular dynamics simulation of binary mixture lubricant films
Authors: Chung Pil Seung , Chen Haigang , Jhon Myung S.
Published: February 2008

Due to the requirements for ultra-small head-media spacing hard disk drives (HDDs), the mixture of lubricants may become feasible and promising alternative for future HDD. In this paper, molecular dynamics simulations with a bead-spring model were employed to examine the detailed structure, conformation, and dynamics of binary mixture lubricant films by analyzing the anisotropic radius of gyration and the self-diffusion coefficient as a function of volume fraction. Our simulation results indicate that the binary mixture monolayer can be more suitable as a disk lubricant in comparison with the single component. The conformation and mobility change by tuning the volume fraction was discussed in conjunction with the optimal lubricant selection.
Acoustic resonance of outer-rotor brushless dc motor for air-conditioner fan
Authors: Lee Hong-Joo , Chung Shi-Uk , Hwang Sang-Moon
Published: February 2008

Generation of acoustic noise in electric motor is an interacting combination of mechanical and electromagnetic sources. In this paper, a brushless dc motor for air-conditioner fan is analyzed by finite element method to identify noise source, and the analysis results are verified by experiments, and sensitivity analysis is performed by design of experiments.