bluuebunny/crossref_metadata_2025 huggingface dataset:
Understanding
DNA
Radicals Employing Theory and Electron Spin Resonance Spectroscopy
Authors: Adhikary Amitava , Kumar Anil , Becker David , Sevilla Michael D.
Published: March 2012

Ionizing radiation, such as γ‐rays, X‐rays, or ion beam radiation, results in the formation of cation and anion radicals in DNA and neutral radicals by secondary reactions. These DNA radicals are stable at low temperatures and, therefore, can be studied by electron spin resonance (ESR) spectroscopy. In these DNA radicals, the unpaired spin on the radical site interacts with nuclei with a magnetic moment, such as,
1
H,
2
H, and
14
N. This electron spin–nuclear spin interaction gives rise to hyperfine coupling, which is characterized by the hyperfine coupling constant (HFCC) values. The HFCC values along with the

g

‐values determine the ESR spectra of these radicals. Calculations based on density functional theory (DFT) allow for identification of these DNA radicals via the prediction of stabilization energies and, most importantly, accurate values of the HFCCs. These calculations elucidate radical conformational structures as well. Thus, the combination of ESR with DFT calculations is a powerful approach to the investigation of DNA radicals and is the main focus of this article. This is illustrated in this article by specific examples—such as the prediction of sites of deprotonation in the DNA base cation radicals, intra‐base pair proton transfer processes in DNA base radicals, and excited state‐induced reactions of the DNA base cation and anion radicals leading to sugar radical formation.
Reversible Addition Fragmentation Chain Transfer (
RAFT
) Polymerization: Mechanism, Process and Applications
Authors: Barner‐Kowollik Christopher , Blinco James P. , Destarac Mathias , Thurecht Kristofer J. , Perrier Sébastien
Published: March 2012

The present article gives an overview of the reversible addition fragmentation chain transfer (RAFT) process. RAFT is one of the most versatile living radical polymerization systems and yields polymers of predictable chain length and narrow molecular weight distribution. RAFT relies on the rapid exchange of thiocarbonyl thio groups between growing polymeric chains. The key strengths of the RAFT process for polymer design are its high tolerance of monomer functionality and reaction conditions, the wide range of well‐controlled polymeric architectures achievable, and its (in‐principle) non‐rate‐retarding nature. This article introduces the mechanism of polymerization, the range of polymer molecular weights achievable, the range of monomers in which polymerization is controlled by RAFT, the various polymeric architectures that can be obtained, the type of end‐group functionalities available to RAFT‐made polymers, and the process of RAFT polymerization.
Atom Transfer Radical Polymerization (ATRP) and Addition (ATRA) and Applications
Authors: Pintauer Tomislav , Matyjaszewski Krzysztof
Published: March 2012

Fundamentals of transition‐metal‐catalyzed atom transfer radical polymerization (ATRP) and mechanistically similar atom transfer radical addition (ATRA) are discussed. Both processes utilize transition‐metal complexes as halogen atom transfer agents. ATRP enables the synthesis of polymeric materials with well‐controlled molecular weight, molecular weight distribution, composition, molecular architecture, and chain‐end functionality. ATRA, on the other hand, is particularly suitable for the synthesis of small and highly functional organic molecules. Basic phenomenology, components (alkyl halide, monomer, solvent, and catalyst), as well as current and forthcoming applications are reviewed.
Spin Labels and Spin Probes
Authors: Bardelang David , Hardy Micaël , Ouari Olivier , Tordo Paul
Published: March 2012

The electron paramagnetic resonance (EPR) parameters of a free radical depend strongly on its microenvironment and stable radicals can be used as reporter molecules for the EPR probing of various chemical and biological systems. Nowadays, nitroxides and trityl radicals are the most important spin labels or spin probes and their use in various applications, spin labeling, spin trapping, oximetry, pH measurement, evaluation of redox status, interactions in supramolecular systems, and so on, are examined.
Polyradicals in Batteries
Authors: Oyaizu Kenichi , Nishide Hiroyuki
Published: March 2012

Organic robust radicals are susceptible to reversible 1e−transfer reactions to yield closed‐shell molecules, giving rise to an electrochemically reversible redox response. This property has been exploited for reversible charge storage by organic polymers, allowing energy storage with an excellent rate performance. Redox properties of the organic robust radicals, together with their roles in a rechargeable device called radical battery, are reviewed.
Radical Chemistry on Fullerenes
Authors: Tzirakis Manolis D. , Orfanopoulos Michael
Published: March 2012

The aim of this article is to provide a concise review mainly on the practical synthetic applications and to a lesser extent on the fundamentals of fullerenes' radical chemistry. From a practical point of view, we demonstrate that the employment of radical reactions in fullerene chemistry has led to the synthesis of a variety of structurally diverse fullerene derivatives which would be otherwise inaccessible. In this context, the major types of neutral or ion radical additions to C
60
are reported. Such reactions include the addition of radicals of different chemical nature, including C‐, Si‐, O‐, S‐, P‐, and metal‐centered radicals, to C
60
or C
70
. From a fundamental perspective, we report on some of the basic characteristics of the radical reactions of fullerenes, such as the tendency of free radicals to add, multiply, and fast to C
60
and the tendency of the resulting RC
60
·
to dimerize.
Drag force in discrete particle models—Continuum scale or single particle scale?
Authors: Kriebitzsch S. H. L. , van der Hoef M. A. , Kuipers J. A. M.
Published: March 2012

Unresolved discrete particle (DP) models, where a Lagrangian method is used for the solid phase, and a Eulerian method for the fluid phase, have become increasingly popular. The fluctuations of the drag force on individual particles in a homogeneous random array obtained from fully resolved simulations using a lattice Boltzmann method were analysed; such fluctuations are by construction ignored in the unresolved DP model. The drag on individual particles in the array can differ up to 40% with the drag that would be used in DP type simulations was found. A detailed analysis shows that the drag on an individual particle depends strongly on all its surrounding neighbors within a distance of at least two particle diameters. As in DP models, the local flow field is unresolved, the conclusion is that this root mean square (RMS) deviation in the drag force is inherent to the model. © 2012 American Institute of Chemical Engineers AIChE J, 59: 316–324, 2013
Predictors of breast milk macronutrient composition in filipino mothers
Authors: Quinn Elizabeth A. , Largado Fe , Power Michael , Kuzawa Christopher W.
Published: March 2012

Objectives:

There is increasing evidence that breastfeeding has long‐term effects on offspring biology and health, which has heightened interest in understanding the extent of variation in breast milk composition and its underlying determinants. Here, we report variation in milk macronutrient composition in a well‐characterized cohort of young Filipino mothers and test underlying maternal predictors of this variation.

Methods:

Morning breast milk samples, anthropometrics, dietary recalls, and other interview data were collected in 102 Filipino young breastfeeding mothers (age range 24.6–25.4 years) living in Cebu City, Philippines. Milk samples were analyzed for protein, fat, sugar, and milk energy density. Regression models were used to test associations between milk macronutrient composition and maternal diet, body composition, breastfeeding duration, and feeding frequency.

Results:

Consistent with past studies, milk fat and energy increased with duration of breastfeeding; there were no associations between maternal diet or percent body fat and milk composition with the exception of a modest, inverse association between maternal adiposity and milk sugar content.

Conclusions:

The relative lack of associations between maternal diet or body composition and milk composition at Cebu is consistent with past studies and suggests that milk composition may be buffered against fluctuations in maternal dietary intake or nutritional status. We speculate that the tendency for milk composition to vary between populations faced with different nutritional ecologies, but to show minimal responsiveness to intake during lactation, may enhance the reliability of milk composition as a stable intergenerational cue of typical local environmental quality. Am. J. Hum. Biol. 2012. © 2012 Wiley Periodicals, Inc.
Helper effects on breeder allocations to direct care
Authors: Kushnick Geoff
Published: March 2012

Introduction:

Mothers receive childcare and productive assistance from allomaternal helpers in many societies. Although much effort has been aimed toward showing helper effects on maternal reproductive success, less has been directed toward highlighting the full range of potential effects on breeder behavior. I present a model of optimal maternal care with helpers, and tests of derived hypotheses with data collected among the Karo Batak—a group of Indonesian agriculturalists.

Methods:

To test the model's predictions I compared the effect of women receiving help from patrilateral versus matrilateral kin because those kin may provide help with different maternal responsibilities. The model predicts a decrease in maternal allocation to care that is substitutable with the helper contribution and the helper assists with that type of care; it predicts an increase in care that is nonsubstitutable with the helper contribution or substitutable care when the helper assists with other responsibilities. With the exception of one other, most models have failed to account for an increase.

Results/Conclusions:

Analyses of time spent carrying children supported the model. With matrilateral helpers, women increased carrying; with patrilateral helpers, they decreased it. Time spent farmworking showed the opposite pattern, suggesting that matrilateral helpers effectively decrease costs, nudging optimal maternal care upward. Patterns of breastfeeding provided little support for the model. The results do, however, suggest potential proximate mechanisms by which helpers influence maternal reproductive success in cooperative breeding societies. Am. J. Hum. Biol. 2012. © 2012 Wiley Periodicals, Inc.
Organization of the gymnotiform fish pallium in relation to learning and memory: III. Intrinsic connections
Authors: Giassi Ana C.C. , Ellis William , Maler Leonard
Published: March 2012

The present article reports on the telencephalic connections of regions of the dorsal telencephalon of the weakly electric fish Apteronotus leptorhynchus and Gymnotus sp. that are involved in learning and memory: the lateral (DL), central (DC), and dorsal (DD) regions of the pallium and the intermediate region between DL and DC (Dx). We find that the main route of transmission consists of diencephalic (preglomerular complex; PG) glutamatergic input to DL; glutamatergic projections from DL to DC and Dx; and glutamatergic output from DC/Dx to di‐, mes‐, and rhombencephalic nuclei. Although PG efferents to DL are spatially organized, the projection from DL to DC appears to be diffuse. The connections of DD are entirely intrinsic to the pallium: DL projects to DD (glutamatergic) and DD feeds back to DL (glutamatergic); DD also projects to DC and has strong contralateral connections. In addition, DL and DD receive input from subpallial regions; we suggest that these are associated with the previously identified γ‐aminobutyric acid (GABA)‐ergic, dopaminergic, and somatostatin‐positive input to these regions. The DL/DD connections are very complex, because DL projects to and receives input from different subdivisions of DD. These subdivisions are linked by circuitry intrinsic to DD itself. DL and DD both contain recurrent putatively excitatory (glutamatergic) connections as well as local putatively inhibitory (GABAergic) interneurons. In contrast, recurrent excitatory connections appears to be absent in DC, and local inhibition is also barely present. Finally, we speculate on the implications of this pattern of connectivity for theories of short‐term memory and long‐term associative memory. J. Comp. Neurol. 520:3333–3358, 2012. © 2012 Wiley Periodicals, Inc.
The upstream boundary condition influences the leaflet opening dynamics in the numerical FSI simulation of an aortic BMHV
Authors: Annerel Sebastiaan , Degroote Joris , Claessens Tom , Segers Patrick , Verdonck Pascal , Vierendeels Jan
Published: March 2012

In this paper, the influence of the upstream boundary condition in the numerical simulation of an aortic bileaflet mechanical heart valve (BMHV) is studied. Three three‐dimensional cases with different upstream boundary conditions are compared. The first case consists of a rigid straight tube with a velocity profile at its inlet. In the second case, the upstream geometry is a contracting left ventricle (LV), positioned symmetrically with respect to the valve. In the last case, the LV is positioned asymmetrical with respect to the valve. The cases are used to simulate the same three‐dimensional BMHV. The change in time of the LV volume is calculated such that the flow rate through the valve is identical in each case. The opening dynamics of the BMHV are modelled using fluid–structure interaction. The simulations show that differences occur in the leaflet movement of the three cases. In particular, with the asymmetric LV, one of the leaflets impacts the blocking mechanism at its open position with a 34% higher velocity than when using the velocity profile, and with an 88% higher velocity than in the symmetric LV case. Therefore, when simulating such an impact, the upstream boundary condition needs to be chosen carefully. Copyright © 2012 John Wiley & Sons, Ltd.
Depolymerization and Hydrodeoxygenation of Switchgrass Lignin with Formic Acid
Authors: Xu Weiyin , Miller Stephen J. , Agrawal Pradeep K. , Jones Christopher W.
Published: March 2012

Organosolv switchgrass lignin is depolymerized and hydrodeoxygenated with a formic acid hydrogen source, 20 wt % Pt/C catalyst, and ethanol solvent. The combination of formic acid and Pt/C is found to promote production of higher fractions of lower molecular weight compounds in the liquid products. After 4 h of reaction, all of the switchgrass lignin is solubilized and 21 wt % of the biomass is shown to be converted into seven prominent molecular species that are identified and quantified. Reaction time is shown to be an important variable in affecting changes in product distributions and bulk liquid product properties. At 20 h of reaction, the lignin is significantly depolymerized to form liquid products with a 76 % reduction in the weighted average molecular weight. Elemental analysis also shows that the resultant liquid products have a 50 % reduction in O/C and 10 % increase in H/C molar ratios compared to the switchgrass lignin after 20 h.
Horseshoe chaos and subharmonic orbits in the nanoelectromechanical Casimir nonlinear oscillator
Authors: Bonnin Michele
Published: March 2012

The progressive miniaturization of electronic components today makes feasible to exploit the nanoscale level. At this scale, phenomena peculiar of the quantum world arise, which can be exploited to realize innovative and potential breakthrough devices. In this paper, the dynamic behavior of one such device, the Casimir nonlinear oscillator is analyzed. Using the Melnikov's method, we prove that under the effect of a weak damping and a weak periodic forcing, complex behaviors in the form of Smale's horseshoes arise, and the mechanism leading to their birth is revealed. Copyright © 2012 John Wiley & Sons, Ltd.
Power durability dependence on temperature, input power, and structure of electrodes in SAW filters
Authors: Takayama Ryoichi , Nakanishi Hidekazu
Published: March 2012

The dependence of power durability on temperature and input power has been studied in detail by using SAW filters with AlMgCu/Ti/AlMgCu/Ti four‐layered electrodes. In SAW filters, acceleration factors of degradation are temperature and input power. These two factors are not independent in actual SAW filters, but it is necessary to control the conditions to keep the independence of these two factors in accelerated deterioration tests. As the results of power durability estimation of four‐layered electrodes taking account of the above point, the activation energy of diffusion showed the value of the bulk diffusion level in tests using 800‐MHz‐band filters, and the dependence of the input power increased in proportion to the frequency of the input power. We also successfully improved the power durability of four‐layered electrodes by modifying the layered structure and increasing the Mg content of the AlMgCu alloy layers. In the former case, the dependence on input power did not change but the absolute level versus the input power was improved. In the latter case the dependence on input power and the absolute level versus the input power did not change but the dependence on temperature increased. © 2012 Wiley Periodicals, Inc. Electron Comm Jpn, 95(4): 33‐40, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10413
A simple, high sensitivity mutation screening using Ampligase mediated T7 endonuclease I and Surveyor nuclease with microfluidic capillary electrophoresis
Authors: Huang Mo Chao , Cheong Wai Chye , Lim Li Shi , Li Mo‐Huang
Published: March 2012

Mutation and polymorphism detection is of increasing importance for a variety of medical applications, including identification of cancer biomarkers and genotyping for inherited genetic disorders. Among various mutation‐screening technologies, enzyme mismatch cleavage (EMC) represents a great potential as an ideal scanning method for its simplicity and high efficiency, where the heteroduplex DNAs are recognized and cleaved into DNA fragments by mismatch‐recognizing nucleases. Thereby, the enzymatic cleavage activities of the resolving nucleases play a critical role for the EMC sensitivity. In this study, we utilized the unique features of microfluidic capillary electrophoresis and de novo gene synthesis to explore the enzymatic properties of T7 endonuclease I and Surveyor nuclease for EMC. Homoduplex and HE DNAs with specific mismatches at desired positions were synthesized using PCR (polymerase chain reaction) gene synthesis. The effects of nonspecific cleavage, preference of mismatches, exonuclease activity, incubation time, and DNA loading capability were systematically examined. In addition, the utilization of a thermostable DNA ligase for real‐time ligase mediation was investigated. Analysis of the experimental results has led to new insights into the enzymatic cleavage activities of T7 endonuclease I and Surveyor nuclease, and aided in optimizing EMC conditions, which enhance the sensitivity and efficiency in screening of unknown DNA variations.
Application of new room‐temperature catalytic oxidation material on indoor formaldehyde control
Authors: Xing Yi , Chen Bei , Guo Tianpeng , Ying Gaoxiang
Published: March 2012

This study has developed a new material for indoor formaldehyde control, room‐temperature catalytic oxidation (RCO) and RCO‐coated media. In order to optimize the adsorption capacity of RCO material on indoor formaldehyde, four impacting factors, including active/assistant component ratio, ingredient ratio (KMnO4/MnSO4), RCO/GAC ratio, and pH, are investigated for both preparation procedure and performance testing of RCO material and RCO coated media. Results show that the RCO material gets the best mechanical strength (level 5) when the molar ratio of two main ingredients (MnSO4/KMnO4) is 3:2, and the pH in the solution is 7. Results also indicate that with the ratio of 3:7 between RCO material and active carbon appears to get the best adsorption capacity for indoor formaldehyde. RCO‐coated media with impregnated 1% of Pt and 5% of Ce is the best regarding the removal efficiency and breakthrough time for formaldehyde. © 2011 American Institute of Chemical Engineers Environ Prog, 32: 115–119, 2013.
Degradation of antibiotics amoxicillin by Co3O4‐catalyzed peroxymonosulfate system
Authors: Guo Weilin , Su Shengnan , Yi Chunliang , Ma Zhenmin
Published: March 2012

Sulfate radical‐based advanced oxidation processes (SR‐AOPs) are attracting considerable attention due to the high oxidizing ability of sulfate radical to degrade organic pollutants in aqueous environments. In this study, the degradation of antibiotics amoxicillin using SR‐AOPs was investigated. This process is based on the generation of sulfate radicals through Co3O4‐mediated activation of peroxymonosulfate (PMS). Several parameters affecting antibiotics degradation such as Co3O4, PMS, pH, and temperature were investigated. The optimal conditions were found to be as follows: oxone concentration 0.01 mol·L −1, Co3O4 dosage 0.06 g, pH 6.0, reaction temperature 60°C, and reaction time 45 min. Under these optimum conditions, it was found that the chemical oxygen demand (COD) removal efficiency of 91.01% was achieved. The effect of ultrasound in the Co3O4/PMS system for amoxicillin degradation was also studied. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 193‐197, 2013
Delta‐tocotrienol suppresses Notch‐1 pathway by upregulating miR‐34a in nonsmall cell lung cancer cells
Authors: Ji Xiangming , Wang Zhiwei , Geamanu Andreea , Goja Arvind , Sarkar Fazlul H , Gupta Smiti V.
Published: March 2012

MicroRNAs (miRNAs) are small noncoding RNAs that play critical roles in regulating various cellular functions by transcriptional silencing. miRNAs can function as either oncogenes or tumor suppressors (oncomirs), depending on cancer types. In our study, using miRNA microarray, we observed that downregulation of the Notch‐1 pathway, by delta‐tocotrienol, correlated with upregulation of miR‐34a, in nonsmall cell lung cancer cells (NSCLC). Moreover, re‐expression of miR‐34a by transfection in NSCLC cells resulted in inhibition of cell growth and invasiveness, induction of apoptosis and enhanced p53 activity. Furthermore, cellular mechanism studies revealed that induction of miR‐34a decreased the expression of Notch‐1 and its downstream targets including Hes‐1, Cyclin D1, Survivin and Bcl‐2. Our findings suggest that delta‐tocotrienol is a nontoxic activator of mir‐34a which can inhibit NSCLC cell proliferation, induce apoptosis and inhibit invasion, and thus offering a potential starting point for the design of novel anticancer agents.
Claudin 18 is a novel negative regulator of bone resorption and osteoclast differentiation
Authors: Linares Gabriel R , Brommage Robert , Powell David R , Xing Weirong , Chen Shin-Tai , Alshbool Fatima Z , Lau K-H William , Wergedal Jon E , Mohan Subburaman
Published: March 2012

Claudin 18 (Cldn-18) belongs to a large family of transmembrane proteins that are important components of tight junction strands. Although several claudin members are expressed in bone, the functional role for any claudin member in bone is unknown. Here we demonstrate that disruption of Cldn-18 in mice markedly decreased total body bone mineral density, trabecular bone volume, and cortical thickness in Cldn-18−/− mice. Histomorphometric studies revealed that bone resorption parameters were increased significantly in Cldn-18−/− mice without changes in bone formation. Serum levels of tartrate-resistant acid phosphatase 5b (TRAP5b) and mRNA expression levels of osteoclast specific markers and signaling molecules were also increased. Loss of Cldn-18 further exacerbated calcium deficiency induced bone loss by influencing bone resorption, thereby resulting in mechanically weaker bone. In vitro studies with bone marrow macrophages revealed Cldn-18 disruption markedly enhanced receptor activator of NF-κB ligand (RANKL)-induced osteoclast differentiation but not macrophage colony-stimulating factor (MCSF)-induced bone marrow macrophage (BMM) proliferation. Consistent with a direct role for Cldn-18 in regulating osteoclast differentiation, overexpression of wild type but not PDZ binding motif deleted Cldn-18 inhibited RANKL-induced osteoclast differentiation. Furthermore, our findings indicate that Cldn-18 interacts with Zonula occludens 2 (ZO-2) to modulate RANKL signaling in osteoclasts. In conclusion, we demonstrate that Cldn-18 is a novel negative regulator of bone resorption and osteoclast differentiation. © 2012 American Society for Bone and Mineral Research.
Low fluence–high repetition rate diode laser hair removal 12‐month evaluation: Reducing pain and risks while keeping clinical efficacy
Authors: Barolet Daniel
Published: March 2012

Background and Objective

High fluence diode lasers with contact cooling have emerged as the mainstay modality for hair removal. However, the use of these devices is associated with pain and side effects, especially in patients with dark or tanned skin. A novel concept of depilation at low fluence using 810 nm diode laser has been introduced as a solution to these shortcomings. The purpose of this study was to evaluate the lasting efficacy and safety of low‐level fluence 810 nm (15 J/cm2) and high repetition rate (5 Hz) F1 Diode Laser™ therapy on hair reduction in patients with various skin types.

Study Design/Materials and Methods

This randomised, controlled, bilaterally paired within‐patient, double‐blind study compared low level fluence 810 nm (15 Joules/cm2) laser diode therapy to nontreated shaved control areas on long‐term hair reduction. Seventeen patients with skin type II–V were treated four times at 1 month intervals. Hair count was assessed monthly over 10 months using an objective computerised method. Safety and tolerability were assessed by adverse reactions monitoring.

Results

Statistically significant differences in hair count between treated and control sites were observed at each follow‐up visit. The majority of patients reported a slight but bearable sensation of heat during the laser treatment, and transient erythema post‐treatment.

Conclusions

This study showed that laser hair removal with the F1 Diode Laser™ system was generally well tolerated, safe, and efficacious in this small sample study of patients with various skin types. After just four treatments, permanent hair reduction following one complete hair cycle has been shown. Controlled studies on larger groups of patients within each skin phototype are needed to confirm these promising results. Lasers Surg. Med. 44:277–281, 2012. © 2012 Wiley Periodicals, Inc.
Psychogenic palatal tremor may be underrecognized: Reappraisal of a large series of cases
Authors: Stamelou Maria , Saifee Tabish A. , Edwards Mark J. , Bhatia Kailash P.
Published: March 2012

Background:

Palatal tremor is characterized by rhythmic movements of the soft palate and can be essential or symptomatic. Some patients can have palatal movements as a special skill or due to palatal tics. Psychogenic palatal tremor is recognized but rarely reported in the literature.

Methods:

We retrospectively evaluated all patients with palatal tremor seen in our center over a period of 10 years.

Results:

Of 17 patients with palatal tremor, we identified 10 patients with isolated palatal tremor. In 70% of those the diagnosis of psychogenic palatal tremor could be made. Of the remainder, 2 had palatal tics and 1 essential palatal tremor.

Conclusions:

We suggest that psychogenic palatal tremor may be underrecognized and propose that targeted clinical examination of positive signs for psychogenic movement disorders in these patients is essential. The correct identification of such patients has important clinical and scientific implications. © 2012 Movement Disorder Society
Can regenerated nerve fibers return to normal size? A long‐term post‐traumatic study of the rat median nerve crush injury model
Authors: Muratori Luisa , Ronchi Giulia , Raimondo Stefania , Giacobini‐Robecchi Maria G. , Fornaro Michele , Geuna Stefano
Published: March 2012

Whether post‐traumatic regeneration can eventually result in rat peripheral nerve fibers regaining their pretrauma size is still an open question. While it has been shown that, after a sufficient duration in post‐traumatic time, the number of regenerated rat peripheral nerve fibers can return to pretrauma numbers and the animal can regain normal prelesion function, no information regarding long‐term changes in the size parameters of the regenerated nerve fibers is available. To fill this gap, we have investigated the post‐traumatic changes in myelinated axon and nerve fiber diameter, myelin thickness, and g‐ratio (the ratio of the inner axonal diameter to the fiber diameter) at three different time points following nerve injury: week‐6, week‐8, and week‐24. A standardized nerve crush injury of the rat median nerve obtained using a nonserrated clamp was used for this study. The results showed that, consistent with previous studies, fiber number returned to normal values at week‐24, but both axon and fiber diameter and myelin thickness were still significantly lower at week‐24 than prelesion, and the g‐ratio, which remained unchanged during the regeneration process, was significantly reduced at week‐24 in comparison to the prelesion value. On the basis of these results, the hypothesis that regenerated rat peripheral nerve fibers are able to return spontaneously to their normal pretrauma state, provided there is a sufficiently long recovery time postaxonotmesis, is not supported. © 2012 Wiley Periodicals, Inc. Microsurgery, 2012.
Group‐averaged anatomical connectivity mapping for improved human white matter pathway visualisation
Authors: Cercignani Mara , Embleton Karl , Parker Geoffrey J M , Bozzali Marco
Published: March 2012

Anatomical connectivity mapping (ACM) is a measure of anatomical connectivity obtained by initiating streamline diffusion tractography from all parenchymal voxels and then counting the number of streamlines passing through each voxel of the brain. ACM highlights WM structures that present multiple connections to the rest of the brain but not necessarily strong microstructural orientation coherence. In this study, ACM was used to develop an atlas of the human brain. The ACM template was constructed from 3 T diffusion‐weighted data from 19 healthy adults. To account for multiple diffusion directions in a voxel, a high angular resolution diffusion imaging (HARDI) technique, namely Q‐ball, was used to model diffusion. To bring data from different subjects into a common space, an algorithm for rotating and averaging the principal directions was implemented, which can be generalized to any application requiring algebraic operations on principal directions derived from any HARDI method. ACM from the average dataset was computed and several white matter connections of interest were identified and highlighted. Fractional anisotropy (FA) from standard diffusion tensor modelling was also derived and FA‐modulated colour coded images obtained from the mean tensor were also shown for comparison, highlighting differences and similarities. The ACM template can serve for educational purposes and as future reference for studies based on the evaluation of ACM in subjects affected by neurological and psychiatric disorders. Copyright © 2012 John Wiley & Sons, Ltd.
Effects of aromatic carboxylic dianhydrides on thermomechanical properties of polybenzoxazine‐dianhydride copolymers
Authors: Jubsilp Chanchira , Ramsiri Boonthariga , Rimdusit Sarawut
Published: March 2012

Enhanced thermomechanical properties of bisphenol‐A based polybenzoxazine (PBA‐a) copolymers obtained by reacting bisphenol‐A‐aniline‐type benzoxazine (BA‐a) resin with three different aromatic carboxylic dianhydrides, i.e., pyromellitic dianhydride (PMDA), 3,3′,4,4′ biphenyltetracarboxylic dianhydride (s‐BPDA), or 3,3′,4,4′ benzophenonetetracarboxylic dianhydride (BTDA) were reported. Glass transition temperature (Tg), of the copolymers was found to be in the order of PBA‐a:PMDA>PBA‐a:s‐BPDA>PBA‐a:‐BTDA. The difference in the Tg of the copolymers is related to the rigidity of the dianhydride components. Furthermore, the Tg of PBA‐a:BTDA, PBA‐a:s‐BPDA, and PBA‐a:BTDA films was observed to be significantly higher than that of the neat PBA‐a owing to the enhanced crosslink density by the dianhydride addition. This greater crosslink density results from additional ester linkage formation between the hydroxyl group of PBA‐a and the anhydride group of dianhydrides formed by thermal curing. Moreover, the copolymers exhibit enhanced thermal stability with thermal degradation temperature (Td) ranging from 410°C to 426°C under nitrogen atmosphere. The char yield at 800°C of the copolymers was found to be remarkably greater than that of the neat PBA‐a with a value up to 60% vs. that of about 38% of the PBA‐a. Toughness of the copolymer films was greatly improved compared to that of the neat PBA‐a. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
Characterization of poly(vinyl alcohol)/potassium chloride polymer electrolytes for electrochemical cell applications
Authors: Pavani Y. , Ravi M. , Bhavani S. , Sharma A.K. , Narasimha Rao V.V.R.
Published: March 2012

A solid polymer electrolyte system based on poly(vinyl alcohol) (PVA) complexed with potassium chloride (KCl) salt was prepared by using solution cast technique. The complexation of KCl salt with the polymer was confirmed by X‐ray diffractrometer and Fourier transform infrared spectroscopy. Differential scanning calorimetry was used to determine the melting temperatures and crystallinity of the pure PVA and complexed films. Ionic conductivities of the electrolytes have been determined by AC impedance studies in the temperature range 303–373 K. The conductivity was found to increase with the increase in dopant concentration and temperature. Transference number data suggests that the charge transport in this polymer electrolyte system is mainly due to ions. Optical absorption studies were made in the wavelength range 200–800 nm on pure and KCl doped PVA films. The absorption edge, direct band, and indirect band gap values were evaluated. It was found that the energy gaps and band edge values shifted to lower energies on doping. Electrochemical cells were fabricated with the configuration of K/(PVA + KCl)/(I2 + C + electrolyte) and discharge characteristics were studied under a constant load of 100 kΩ. Various cell parameters, such as open circuit voltage, short circuit current, power density, and energy density were determined. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
Viscoelastic constitutive model for uniaxial time‐dependent ratcheting of polyetherimide polymer
Authors: Pan Douxing , Kang Guozheng , Jiang Han
Published: March 2012

Based on the experimental observations, a cyclic nonlinear viscoelastic constitutive model was proposed to describe the uniaxial time‐dependent ratcheting of polyetherimide (PEI) polymer under tension–compression and tension–tension cyclic loading. The model was constructed by extending the nonlinear viscoelastic Schapery model (Schapery, Polym. Eng. Sci., 9, 295 (1969)). The extension emphasized the changes of parameter functions used in the original model, which enabled the model to describe the ratcheting of polymer material. Comparing the simulations with corresponding experimental results, the capability of the extended model to predict the uniaxial time‐dependent ratcheting of PEI was verified. It is shown that the extended model can reasonably describe the uniaxial time‐dependent ratcheting of the polymer under the tension–compression and tension–tension cyclic loading with different peak‐holdings, stress rates, and stress levels. POLYM. ENG. SCI., 52:1874–1881, 2012. © 2012 Society of Plastics Engineers
Effects of mixing protocol on the performance of nanocomposites based on polyamide 6/acrylonitrile–butadiene–styrene blends
Authors: Oliveira A.D. , Larocca N.M. , Paul D.R. , Pessan L.A.
Published: March 2012

Toughening of polyamide 6 (PA6) can be achieved by appropriate addition of an elastomeric matrix phase; however, this leads to a loss of rigidity and mechanical strength. As a result, much research has been directed at obtaining an optimal balance between toughness and rigidity for these thermoplastics. The approach explored here is the formation of nanocomposites from PA6/acrylonitrile–butadiene–styrene (ABS) blends prepared by melt mixing with a modified montmorillonite (Cloisite® 30B) and styrene/maleic anhydride copolymer as a compatibilizer. The effect of the mixing sequence of the components on the morphology and properties is a primary focus. The morphology and mechanical properties of the materials were characterized by X‐ray diffraction, electron microscopy, and tensile and impact testing. Incorporation of the compatibilizer in the PA6/ABS blend increased toughness but decreased rigidity. A significant increase of modulus was observed for the nanocomposite blend compared with the blend or the matrix. This increase was attributed to the exfoliation of organoclay layers in the PA6 matrix phase. It was also observed that the morphology of the ABS dispersed phase was considerably influenced by the mixture sequence. POLYM. ENG. SCI., 52:1909–1919, 2012. © 2012 Society of Plastics Engineers
Post‐buckling of simply supported column made of nonlinear elastic materials obeying the generalized Ludwick constitutive law
Authors: Saetiew W. , Chucheepsakul S.
Published: March 2012

In this article, the post‐buckling behavior of a simply supported column made of nonlinear elastic materials subjected to an end axial force is investigated. The column has a uniform rectangular cross‐section in which the stress–strain relationship of such materials is represented by the generalized Ludwick constitutive law. To derive the governing equations, both geometrical and material nonlinearities have been considered. Further, a set of highly nonlinear simultaneous first‐order differential equations with boundary conditions is established and numerically solved by the shooting method. Several numerical results are carried out and discussed highlighting the significant influences of the material nonlinearity parameter n on the equilibrium configurations and the equilibrium paths. From the results, there are many interesting features associated with the nonlinear hardening column such as a non‐monotonic bifurcation curve, the limit load point, snap‐through phenomenon, and hysteresis loop. Furthermore, the numerical results are compared with previous studies in order to test the validity and accuracy of the present method.
Comparing the impact of cloudiness on carbon dioxide exchange in a grassland and a maize cropland in northwestern China
Authors: Bai Yanfen , Wang Jian , Zhang Baocheng , Zhang Zhihui , Liang Ji
Published: March 2012

Light quantity and quality strongly influence plant growth. However, different ecosystems have different capabilities to assimilate solar radiation. In this study, the effects of cloudiness intensity on the net ecosystem exchange of carbon dioxide (NEE) were compared between an alpine grassland (with lower leaf area index) at A'Rou and an oasis maize cropland (with higher leaf area index) at Yingke, using flux data obtained during the middle of the growing season (July–August) in 2008 and 2009. The results showed that the response of NEE to photosynthetically active radiation (PAR) was more negative (carbon uptake) under cloudy than under clear skies at both sites. The maximum NEE occurred when the clearness index (CI) ranged from 0.4 to 0.7 under cloudy skies. The maximum enhancements were 11.9% for solar elevation angles of 60–65° in the grassland, and 34.9% for solar elevation angles of 60–65° and 10.3% for angles of 35–40° in the maize cropland before the irrigation period. The response of NEE to CI changed slightly with solar elevation angle in the grassland compared to the maize cropland. The results indicate that enhanced NEE under cloudy skies can be attributed to increasingly diffuse PAR and interactions with environmental factors (air temperature and vapor pressure deficit).
Exponential asymptotic stability of a class of dynamical systems with applications to models of turbulent flow in two and three dimensions
Authors: Avrin Joel
Published: March 2012

We consider a class of dynamical systems of the form du/dt + Bu + F(u) = b on a Hilbert space H where the self-adjoint linear operator B is positive with a strictly positive first eigenvalue and b = b0 + b1 such that (b0, Bv) = 0 for all v ∈ H. Given two solutions u and v, we set u − v = w and show that if u(t) → 0 and v(t) → 0 as t → ∞, then in fact eventually w(t) → 0 at an exponential rate. We apply these results to the two-dimensional Navier–Stokes equations (NSEs), the three-dimensional hyperviscous NSEs and the three-dimensional NS-α equations on bounded domains and also establish stability in the sense of Lyapunov; for these systems we assume a condition on b1 to impose decaying turbulence. We also show for the case of decaying turbulence that Leray solutions of the three-dimensional NSEs on bounded domains eventually become regular in addition to decaying to zero. In particular, they eventually satisfy the conditions needed for the abstract stability results.
Diverse norovirus genotypes identified in sewage-polluted river water in South Africa
Authors: MANS J. , NETSHIKWETA R. , MAGWALIVHA M. , VAN ZYL W. B. , TAYLOR M. B.
Published: March 2012

This study aimed to assess norovirus (NoV) contamination and genotype diversity in surface water in Gauteng, South Africa. Between January 2008 and December 2010, three rivers, namely Klip, Suikerbosrant, and Rietspruit were monitored for NoV genogroup (G)I and GII. Viruses were recovered using the glass wool adsorption-elution technique and detected by real-time reverse transcription–polymerase chain reaction. From 2008 to 2010, NoVs were detected in 66% (70/106) of Klip river samples. The Rietspruit and Suikerbosrant rivers were contaminated with NoV in 95% (20/21) and 21% (5/24) of samples, respectively. NoV-positive samples comprised of 33% GI, 29% GII and 38% of both GI and GII strains. Based on partial capsid gene analysis (region C), 16 NoV genotypes (6 GI, 10 GII) were identified. The major genotypes detected were GI.4, GI.5 and GII.4. These rivers could be a potential source of NoV infection for communities using the water for domestic or recreational purposes.
Improved Focused Ion Beam Target Preparation of (S)TEM Specimen—A Method for Obtaining Ultrathin Lamellae
Authors: Lechner Lorenz , Biskupek Johannes , Kaiser Ute
Published: March 2012

Specimen quality is vital to (scanning) transmission electron microscopy (TEM) investigations. In particular, thin specimens are required to obtain excellent high-resolution TEM images. Conventional focused ion beam (FIB) preparation methods cannot be employed to reliably create high quality specimens much thinner than 20 nm. We have developed a method forin situtarget preparation of ultrathin TEM lamellae by FIB milling. With this method we are able to routinely obtain large area lamellae with coplanar faces, thinner than 10 nm. The resulting specimens are suitable for low kV TEM as well as scanning TEM. We have demonstrated atomic resolution byCs-corrected high-resolution TEM at 20 kV on a FIB milled Si specimen only 4 nm thick; its amorphous layer measuring less than 1 nm in total.
Electron Diffraction Based Analysis of Phase Fractions and Texture in Nanocrystalline Thin Films, Part III: Application Examples
Authors: Lábár J.L. , Adamik M. , Barna B.P. , Czigány Zs. , Fogarassy Zs. , Horváth Z.E. , Geszti O. , Misják F. , Morgiel J. , Radnóczi G. , Sáfrán G. , Székely L. , Szüts T.
Published: March 2012

In this series of articles, a method is presented that performs (semi)quantitative phase analysis for nanocrystalline transmission electron microscope samples from selected area electron diffraction (SAED) patterns. Volume fractions and degree of fiber texture are determined for the nanocrystalline components. The effect of the amorphous component is minimized by empirical background interpolation. First, the two-dimensional SAED pattern is converted into a one-dimensional distribution similar to X-ray diffraction. Volume fractions of the nanocrystalline components are determined by fitting the spectral components, calculated for the previously identified phases with a priori known structures. These Markers are calculated not only for kinematic conditions, but the Blackwell correction is also applied to take into account dynamic effects for medium thicknesses. Peak shapes and experimental parameters (camera length, etc.) are refined during the fitting iterations. Parameter space is explored with the help of the Downhill-SIMPLEX. The method is implemented in a computer program that runs under the Windows operating system. Part I presented the principles, while part II elaborated current implementation. The present part III demonstrates the usage and efficiency of the computer program by numerous examples. The suggested experimental protocol should be of benefit in experiments aimed at phase analysis using electron diffraction methods.
Did we see the 2011 summer heat wave coming?
Authors: Luo Lifeng , Zhang Yan
Published: March 2012

A series of climate extreme events affected many parts of the US during 2011, including the severe drought in Texas, the spring tornado outbreak in the southern states, and the weeklong summer heat wave in the Central Plains. Successful prediction of these events can better inform and prepare the general public to cope with these extremes. In this study, we investigate the operational capability of the new NCEP Climate Forecast System (CFSv2) in predicting the 2011 summer heat wave. We found that starting from April 2011, the operational CFSv2 forecast consistently suggested an elevated probability of extremely hot days during the forthcoming summer over the Central Plains, and as the summer was approaching the forecast became more certain about the summer heat wave in its geographic location, intensity and timing. This study demonstrates the capability of the new seasonal forecast system and its potential usefulness in decision making process.
A first principles molecular dynamics study of the solvation structure and migration kinetics of an excess proton and a hydroxide ion in binary water-ammonia mixtures
Authors: Bankura Arindam , Chandra Amalendu
Published: March 2012

We have investigated the solvation structure and migration kinetics of an excess proton and a hydroxide ion in water-ammonia mixed liquids of varying composition by means of ab initio molecular dynamics simulations. The excess proton is always found to be attached to an ammonia molecule to form the ammonium ion. Migration of the excess proton is found to occur very occasionally from one ammonia to the other but no proton transfer to a water molecule is observed during the entire simulations. Also, when the ammonium ion is solvated in water only, its hydrogen bond dynamics and rotation are found to occur at a faster rate than those in water-ammonia mixtures. For water-ammonia mixtures containing a proton less, the defect is found to stay like the hydroxide ion. For these systems, occasional proton transfer is found to occur only through the hydrogen bonded chains of water molecules in these water-ammonia mixtures. No proton transfer is found to take place from an ammonia molecule. The presence of ammonia molecules makes the realization of proper presolvated state of the hydroxide ion to accept a proton a more difficult process and, as a result, the rate of proton transfer and migration kinetics of the hydroxide ion in water-ammonia mixtures are found to be slower than that in liquid water and these rates are found to slow down further with increase of ammonia concentration.