bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adenylate‐Forming Enzymes of Rubradirin Biosynthesis: RubC1 Is a Bifunctional Enzyme with Aminocoumarin Acyl Ligase and Tyrosine‐Activating Domains
Authors: Boll Björn , Hennig Susanne , Xie Chunsong , Kyong Sohng Jae , Heide Lutz 
Published: March 2011

AbstractThe biosynthesis of aminocoumarin antibiotics requires two acyladenylate‐forming enzymes: one for the activation of L‐tyrosine as a precursor of the aminocoumarin moiety and another for the linkage of an acyl moiety to the aminocoumarin moiety. Unexpectedly, the biosynthetic gene cluster of the aminocoumarin antibiotic rubradirin was found to contain three genes for putative acyladenylate‐forming enzymes of aminocoumarin biosynthesis and conjugation. We expressed, purified, and investigated these three proteins. Orf4 (55 kDa) was shown to be an active aminocoumarin acyl ligase. RubF6 (56 kDa) was inactive, but could be converted into an active enzyme by site‐directed mutagenesis. RubC1 (138 kDa) was shown to be a unique bifunctional enzyme, comprising an aminocoumarin acyl ligase, and tyrosine‐adenylation and peptidyl‐carrier domains. This natural hybrid enzyme is unique among known proteins. A hypothesis is proposed as to how such an enzyme could offer a particularly effective machinery for aminocoumarin antibiotic biosynthesis.
Unsteady Mixing Characteristics in a Vessel with Forward‐Reverse Rotating Impeller
Authors: Woziwodzki S. 
Published: March 2011

AbstractUsually, mixing is carried out in a vessel with four baffles and a single impeller. In some applications, however, the use of a baffled vessel is not recommended. One of the stirring methods used instead is unsteady agitation with forward‐reverse rotating impellers. The aim of this work was to characterize the agitation characteristics in a baffled and an unbaffled vessel with a turbine impeller. Mixing time and mixing power were evaluated in relation to the presence of baffles and the frequency of forward‐reverse rotation. It was found that the frequency of oscillation does not affect either the mixing time and mixing power values or the drag and added mass coefficients. Power requirements and mixing time were higher compared to the steady mixing conditions in a baffled vessel. The results showed that it is not recommended to use baffles because they have no influence on unsteady mixing.
Synthesis, Structure, and Biological Activity of des‐Side Chain Analogues of 1α,25‐Dihydroxyvitamin D3 with Substituents at C18
Authors: Verlinden Lieve , Verstuyf Annemieke , Eelen Guy , Bouillon Roger , Ordóñez‐Morán Paloma , Larriba María Jesús , Muñoz Alberto , Rochel Natacha , Sato Yoshiteru , Moras Dino , Maestro Miguel , Seoane Samuel , Dominguez Fernando , Eduardo‐Canosa Silvina , Nicoletti Daniel , Moman Edelmiro , Mouriño Antonio 
Published: March 2011

AbstractAn improved synthetic route to 1α,25‐dihydroxyvitamin D3 des‐side chain analogues 2 a and 2 b with substituents at C18 is reported, along with their biological activity. These analogues display significant antiproliferative effects toward MCF‐7 breast cancer cells and prodifferentiation activity toward SW480‐ADH colon cancer cells; they are also characterized by a greatly decreased calcemic profile. The crystal structure of the human vitamin D receptor (hVDR) complexed to one of these analogues, 20(17→18)‐abeo‐1α,25‐dihydroxy‐22‐homo‐21‐norvitamin D3 (2 a) reveals that the side chain introduced at position C18 adopts the same orientation in the ligand binding pocket as the side chain of 1α,25‐dihydroxyvitamin D3.
The prediction of amino proton chemical shifts using optimally selected wave function
Authors: Shaghaghi Hoora , Iravani Maryam , Tafazzoli Mohsen 
Published: March 2011

AbstractGas phase amino proton chemical shifts in the 54 of amines have been predicted using Gauge‐independent atomic orbital (GIAO) method and optimally selected wave function. The effects of electron correlation, triple‐ξ valance shell, diffuse function, and polarization function on calculated amino proton chemical shifts have been investigated using factorial design as a multivariate technique. Different optimized wave functions for different groups of amines were recommended. A wave function as the best level of the theory is proposed for homologue amines covered. In this context, B3LYP/6‐311+G and HF/6‐311+G wave functions have been recommended as the best and the most efficient level of theory for calculating amino proton chemical shifts of alkylamines and arylamines respectively. © 2011 Wiley Periodicals, Inc. Concepts Magn Reson Part A 38A: 25–32, 2011.
NMR signal detection using inductive coupling: Applications to rotating microcoils
Authors: Jacquinot Jacques‐François , Sakellariou Dimitris 
Published: March 2011

AbstractSensitivity in solid‐state nuclear magnetic resonance can be improved by the use of rotating microcoils (1). The connection to the rest of the electronics is performed through resonant inductive coupling. This mode of detection of nuclear induction has major advantages as it provides a wireless way to obtain extremely high radio‐frequency amplitudes per unit current under sample rotation and thus improved sensitivity for size‐limited samples. We review the circuit electronics and discuss experimental optimization of the probe and coil parameters. We also present alternative geometries for coupling between rotating coils and we explicitly calculate the signal enhancement. Two practical cases are presented, namely a standard magic angle sample spinning probe and a double sample rotation probe. We conclude with a theoretical discussion about the limits of detection attainable with coil miniaturization. © 2011 Wiley Periodicals, Inc. Concepts Magn Reson Part A 38A: 33–51, 2011.
Regularization in parallel MR image reconstruction
Authors: Omer Hammad , Dickinson Robert 
Published: March 2011

AbstractParallel MRI has brought forward new applications by reducing the scan time in MR image acquisition. The acceleration is achieved by reducing the number of phase encode steps acquired during the image acquisition thus giving aliased images. Sensitivity encoding (SENSE) is a widely used method to unwrap the aliased images. One major problem is the noise amplification during the process of reconstruction as well as the artifacts, which may arise during the reconstruction process. Regularization is an important tool to reduce this noise amplification (measured by geometry factor [g‐factor]) and the artifacts, but it is computationally expensive. This work aims at exploring an alternative to regularization that would not be computationally expensive. The alternative suggested uses wavelet denoising of the coil sensitivity maps before applying standard SENSE reconstruction algorithm. The results of this reconstruction are compared with the reconstruction obtained by Tikhonov regularization. The results show that for lower acceleration factors (AFs; 2 and 3), the wavelet denoising of sensitivity maps before applying standard SENSE produces comparable results to those of Tikhonov regularization at much lesser computational cost but for higher AFs Tikhonov regularization is a better choice to acquire good quality images. © 2011 Wiley Periodicals, Inc. Concepts Magn Reson Part A 38A: 52–60, 2011.
Three‐dimensional quadrature array coil elements for improved parallel magnetic resonance imaging performance at 1.5 Tesla
Authors: Mueller Matthias F. , Lanz Titus , Breuer Felix , Griswold Mark A. , Jakob Peter M. 
Published: March 2011

AbstractIn this study, a special concept of 3D quadrature array coil elements is presented. It allows for doubling the number of phased‐array coil elements over a localized region of interest (ROI) without the necessity of reducing the sizes of the elements below optimal dimensions and thus losing performance due to domination of the noise of the elements. In this study, a 3D quadrature array coil element is formed of a planar coil element in combination with a perpendicular orientated, geometrically decoupled, second coil element. Simulation results of such a perpendicular arrangement of single coil elements are presented demonstrating the improvement in spatial sensitivity distribution and signal‐to‐noise ratio (SNR) over the localized ROI. In addition, an eight‐channel prototype array coil was built out of 3D quadrature array elements approving the advantageous encoding capabilities and SNR performance of the presented concept by in vivo T2‐weighted spin‐echo imaging studies on the thoracic human spinal cord. © 2011 Wiley Periodicals, Inc. Concepts Magn Reson Part A 38A: 61–73, 2011.
Configuring large‐scale storage using a middleware with machine learning
Authors: Eyers David M. , Routray Ramani , Zhang Rui , Willcocks Douglas , Pietzuch Peter 
Published: March 2011

SUMMARYThe proliferation of cloud services and other forms of service‐oriented computing continues to accelerate. Alongside this development is an ever‐increasing need for storage within the data centres that host these services. Management applications used by cloud providers to configure their infrastructure should ideally operate in terms of high‐level policy goals, and not burden administrators with the details presented by particular instances of storage systems. One common technology used by cloud providers is the Storage Area Network (SAN). Support for seamless scalability is engineered into SAN devices. However, SAN infrastructure has a very large parameter space: their optimal deployment is a difficult challenge, and subsequent management in cloud storage continues to be difficult.parindent = 10pt In this article, we discuss our work in SAN configuration middleware, which aims to provide users of large‐scale storage infrastructure such as cloud providers with tools to assist them in their management and evolution of heterogeneous SAN environments. We propose a middleware rather than a stand‐alone tool so that the middleware can be a proxy for interacting with, and informing, a central repository of SAN configurations. Storage system users can have their SAN configurations validated against a knowledge base of best practices that are contained within the central repository. Desensitized information is exported from local management applications to the repository, and the local middleware can subscribe to updates that proactively notify storage users should particular configurations be updated to be considered as sub‐optimal, or unsafe. Copyright © 2011 John Wiley & Sons, Ltd.
Specifying and enforcing the principle of least privilege in role‐based access control
Authors: Ma Xiaopu , Li Ruixuan , Lu Zhengding , Lu Jianfeng , Dong Meng 
Published: March 2011

AbstractThe principle of least privilege in role‐based access control is an important area of research. There are two crucial issues related to it: the specification and the enforcement. We believe that the existing least privilege specification schemes are not comprehensive enough and few of the enforcement methods are likely to scale well. In this paper, we formally define the basic principle of least privilege problem and present different variations, called the delta‐approx principle of least privilege problem and the minimizing‐approx principle of least privilege problem. Since there may be more than one result to enforce the same principle of least privilege, we introduce the notation about weights of permissions and roles to optimize the results. Then we prove that all least privilege problems are NP‐complete. As an important contribution of the paper, we show that the principle of least privilege problem can be reduced to minimal cost set covering (MCSC) problem. We can borrow the existing solutions of MCSC to solve the principle of least privilege problems. Finally, different algorithms are designed to solve the proposed least privilege problems. Experiments on performance study prove the superiority of our algorithms. Copyright © 2011 John Wiley & Sons, Ltd.
Effects of Spatial Constraints and Brønsted Acid Site Locations on para‐Terphenyl Ionization and Charge Transfer in Zeolites
Authors: Belhadj Fatima , Moissette Alain , Brémard Claude , Hureau Matthieu , Derriche Zoubir 
Published: March 2011

AbstractThe locations of Brønsted acid sites (BAS) in the channels of medium‐pore zeolites have a significant effect on the spontaneous ionization of para‐terphenyl (PP3) insofar as spatial constraints determine the stability of transition states and charge‐transfer complexes relevant to charge separation. The ionization rates and ionization yield values demonstrate that a strong synergy exists between the H+ polarization energy and spatial constraints imposed by the channel topology. Spectroscopic and modeling results show that PP3 incorporation, charge separation, charge transfer and charge recombination differ dramatically among zeolites with respect to channel structure (H‐FER, H‐MFI, H‐MOR) and BAS density in the channel. Compartmentalization of ejected electrons away from the initial site of ionization decreases dramatically the propensity for charge recombination. The main mode of PP3.+ decay is hole transfer to form AlO4H.+⋅⋅⋅PP3 charge‐transfer complexes characterized by intense absorption in the visible range. According to the nonadiabatic electron‐transfer theory, the small reorganization energy in constrained channels explains the slow hole‐transfer rate.
High‐Resolution Electronic Spectroscopy Studies of meta‐Aminobenzoic Acid in the Gas Phase Reveal the Origins of its Solvatochromic Behavior
Authors: Fleisher Adam J. , Morgan Philip J. , Pratt David W. 
Published: March 2011

AbstractA theoretical and experimental investigation of meta‐aminobenzoic acid (MABA) in the gas phase is presented, with the goal of understanding counterintuitive observations on the solvatochromism of this “push‐pull” molecule. The adiabatic excitation energies, transition moments, and excited‐state structures are examined using the complete active space self‐consistent field approach (CASSCF and CASPT2), which shows the first excited electronic state of MABA to be of greater charge transfer character than was found in the para‐isomer (PABA). The rotationally resolved electronic spectrum of MABA reveals the existence of two rotamers, owing to asymmetry in the carboxylic acid functional group. Stark measurements in a molecular beam show the change in permanent dipole moment upon excitation to be Δμ≈3.5 D for both rotamers, more than three times larger than that found in PABA. The excited state measurements reported here, along with supporting data from theory, clearly demonstrate how the meta‐directing effects of asymmetric substitution in aniline derivatives can drive charge transfer pathways in the isolated molecule.
A class of digitally programmable nth‐order filters
Authors: Alzaher Hussain , Tasadduq Noman , Al‐Ees Osama 
Published: March 2011

SUMMARYA family of new high‐order filters capable of providing all filter functions without changing the circuit topology is proposed for integrated circuit applications. The proposed filters are based on simple active elements, namely, digitally controlled current amplifiers (DCCAs) and unity gain voltage buffers (VBs). Gains of DCCAs are digitally programmed to adjust the coefficients of transfer functions. R2R ladders are also utilized to increase the tuning flexibility of the proposed filters. A filter replicating the famous KHN biquad is extended to realize general nth‐order filters. Comparison with the recent works shows that the proposed approach results in more efficient realizations compared with its counterparts based on other current‐mode active elements. Experimental results obtained from a fourth‐order filter implemented using devices fabricated in a 0.35‐µm CMOS process are provided. Copyright © 2011 John Wiley & Sons, Ltd.
Cytometric solutions in veterinary andrology: Developments, advantages, and limitations
Authors: Petrunkina A. M. , Harrison R. A. P. 
Published: March 2011

AbstractCytometric methodologies are becoming increasingly important in veterinary andrology as means of assessing sperm function. However, as yet, flow cytometric techniques in veterinary andrology have not kept up in sophistication with those in other areas of biology and medicine. In this brief review, we consider the present state of cytometry in andrological procedures for evaluating the fertility of domestic animal sires. We outline the aspects of sperm physiology, paying particular attention to the changes that take place during the process known as capacitation, which prepares the sperm for interaction with the egg. We then examine briefly but critically the cytometric techniques that are currently in commercial use or are being established in research laboratories for testing sperm characteristics. Current limitations and potential developments in semen assessment are discussed. Recent research knowledge offers possibilities for applying more subtle flow cytometric approaches to distinguish different levels of fertilizing potential in semen samples. For example, linking field fertility data to multiparametric kinetic studies of sperm capacitational changes rather than “single parameter—single time point” estimations may reveal that slower rather than rapid changes indicate high fertility. Moreover, the development of multicolor flow cytometric procedures as a means of evaluating multiple functional parameters in individual cells would reduce the uncertainties always inherent in predicting fertility from in vitro sperm evaluation tests. © 2011 International Society for Advancement of Cytometry
Scheduling of frequently communicating tasks
Authors: Papazachos Zafeirios C. , Karatza Helen D. 
Published: March 2011

SUMMARYGang scheduling is an efficient resource management scheme for distributed systems which combines elements of time sharing and space sharing. It is a suitable technique particularly in the case when parallel tasks have to be running concurrently to make progress in communication. This paper studies the impact on scheduling performance when dynamically generated sequential gangs exist in the workload. In the case of sequential gangs, a subsequent gang can be dynamically generated after the execution of the initial gang based on affinity information which resides on the caches of the previously seized processors. The performance of different gang‐scheduling algorithms is examined for various cases of workload compositions which range from cases with a low demand for dynamically generated gangs to cases with a high ratio of sequential gangs to solitary gangs. A simulation model is implemented to address associated performance issues. Copyright © 2011 John Wiley & Sons, Ltd.
Intravascular pillars and pruning in the extraembryonic vessels of chick embryos
Authors: Lee Grace S. , Filipovic Nenad , Lin Miao , Gibney Barry C. , Simpson Dinee C. , Konerding Moritz A. , Tsuda Akira , Mentzer Steven J. 
Published: March 2011

AbstractTo investigate the local mechanical forces associated with intravascular pillars and vessel pruning, we studied the conducting vessels in the extraembryonic circulation of the chick embryo. During the development days 13–17, intravascular pillars and blood flow parameters were identified using fluorescent vascular tracers and digital time‐series video reconstructions. The geometry of selected vessels was confirmed by corrosion casting and scanning electron microscopy. Computational simulations of pruning vessels suggested that serial pillars form along pre‐existing velocity streamlines; blood pressure demonstrated no obvious spatial relationship with the intravascular pillars. Modeling a Reynolds number of 0.03 produced 4 pillars at approximately 20‐μm intervals matching the observed periodicity. In contrast, a Reynolds number of 0.06 produced only 2 pillars at approximately 63‐μm intervals. Our modeling data indicated that the combination of wall shear stress and gradient of shear predicted the location, direction, and periodicity of developing pillars. Developmental Dynamics 240:1335–1343, 2011. © 2011 Wiley‐Liss, Inc.
Conditional deletion of N‐Myc disrupts neurosensory and non‐sensory development of the ear
Authors: Kopecky Benjamin , Santi Peter , Johnson Shane , Schmitz Heather , Fritzsch Bernd 
Published: March 2011

AbstractEar development requires interactions of transcription factors for proliferation and differentiation. The proto‐oncogene N‐Myc is a member of the Myc family that regulates proliferation. To investigate the function of N‐Myc, we conditionally knocked out N‐Myc in the ear using Tg(Pax2‐Cre) and Foxg1KiCre. N‐Myc CKOs had reduced growth of the ear, abnormal morphology including fused sensory epithelia, disrupted histology, and disorganized neuronal innervation. Using Thin‐Sheet Laser Imaging Microscopy (TSLIM), 3D reconstruction and quantification of the cochlea revealed a greater than 50% size reduction. Immunochemistry and in situ hybridization showed a gravistatic organ‐cochlear fusion and a “circularized” apex with no clear inner and outer hair cells. Furthermore, the abnormally developed cochlea had cross innervation from the vestibular ganglion near the basal tip. These findings are put in the context of the possible functional relationship of N‐Myc with a number of other cell proliferative and fate determining genes during ear development. Developmental Dynamics 240:1373–1390, 2011. © 2011 Wiley‐Liss, Inc.
Representations and beliefs about eating disorders in a sample of french adolescents
Authors: Rousseau Amélie , Callahan Stacey , Chabrol Henri 
Published: March 2011

AbstractObjective:Body dissatisfaction and psychological problems are cited as the major cause of anorexia nervosa (AN) and bulimia nervosa (BN). Behavioral characteristics most often associated with AN and BN are food restriction, vomiting, and excessive exercise. The objective of this study was to examine representations and beliefs about AN and BN in a sample of French adolescents.Method:The sample was composed of 942 adolescents (16.4 years ± 1.2; 59.1% girls and 40.9% boys).Results:Excessive thinness and health problems were the physical characteristics most often associated with eating disorders (ED). A majority of the adolescents believe that ED most often manifest in adolescent females and were conscious of the gravity and chronic nature of ED; thinness was appropriately associated with AN, but many had erroneous beliefs regarding BN.Discussion:The results of this study provide insight into what young people in France believe and understand about the two major ED and advocate for more available information concerning BN for this population. © 2011 Wiley Periodicals, Inc. (Int J Eat Disord 2012)