bluuebunny/crossref_metadata_2025 huggingface dataset:
Virtual reality myringotomy simulation with real‐time deformation: Development and validity testing
Authors: Ho Andrew K. , Alsaffar Hussain , Doyle Philip C. , Ladak Hanif M. , Agrawal Sumit K.
Published: May 2012

Objectives/Hypothesis:

Surgical simulation is becoming an increasingly common training tool in residency programs. The first objective was to implement real‐time soft‐tissue deformation and cutting into a virtual reality myringotomy simulator. The second objective was to test the various implemented incision algorithms to determine which most accurately represents the tympanic membrane during myringotomy.

Study Design:

Descriptive and face‐validity testing.

Methods:

A deformable tympanic membrane was developed, and three soft‐tissue cutting algorithms were successfully implemented into the virtual reality myringotomy simulator. The algorithms included element removal, direction prediction, and Delaunay cutting. The simulator was stable and capable of running in real time on inexpensive hardware. A face‐validity study was then carried out using a validated questionnaire given to eight otolaryngologists and four senior otolaryngology residents. Each participant was given an adaptation period on the simulator, was blinded to the algorithm being used, and was presented the three algorithms in a randomized order.

Results:

A virtual reality myringotomy simulator with real‐time soft‐tissue deformation and cutting was successfully developed. The simulator was stable, ran in real time on inexpensive hardware, and incorporated haptic feedback and stereoscopic vision. The Delaunay cutting algorithm was found to be the most realistic algorithm representing the incision during myringotomy (P < .05). The Likert and visual analog scales had strong correlations, suggesting good internal reliability.

Conclusions:

The first virtual reality myringotomy simulator is being developed and now integrates a real‐time deformable tympanic membrane that appears to have face validity. Further development and validation studies are necessary before the simulator can be studied with respect to training efficacy and clinical impact. Laryngoscope, 2012
Fabrication of Polylactide‐Based Biodegradable Thermoset Scaffolds for Tissue Engineering Applications
Authors: Sakai Reika , John Baiju , Okamoto Masami , Seppälä Jukka V. , Vaithilingam Jayasheelan , Hussein Husnah , Goodridge Ruth
Published: May 2012

The fabrication of tissue engineering scaffolds based on the polymerization of crosslinked polylactide using leaching and batch foaming to generate well‐controlled and interconnected biodegradable polymer scaffolds is reported. The scaffold fabrication parameters are studied in relation to the interpore connectivity, pore morphology, and structural stability of the crosslinked PLA scaffold. In vitro cell culture and in vitro degradation are used to analyze the biocompatibility and biodegradability of the scaffolds. The new crosslinked PLA thermoset scaffolds are highly suitable for bone tissue engineering applications due to their complex internal architecture, thermal stability, and biocompatibility.

magnified image
A trace inequality of Riesz potentials in variable exponent Orlicz spaces
Authors: Mizuta Yoshihiro , Shimomura Tetsu
Published: May 2012

Our aim in this paper is to deal with traces on the hyperplane for Riesz potentials of order α for functions f satisfying the Orlicz type condition

where p( · ) and q( · ) are variable exponents satisfying the log‐Hölder and the log log‐Hölder conditions, respectively.
Linearized stability analysis of surface diffusion for hypersurfaces with boundary contact
Authors: Depner Daniel
Published: May 2012

The linearized stability of stationary solutions for surface diffusion is studied. We consider hypersurfaces that lie inside a fixed domain, touch its boundary with a right angle and fulfill a no‐flux condition. We formulate the geometric evolution law as a partial differential equation with the help of a parametrization from Vogel 24, which takes care of a possible curved boundary. For the linearized stability analysis we identify as in the work of Garcke, Ito and Kohsaka 14 the problem as an H−1‐gradient flow, which will be crucial to show self‐adjointness of the linearized operator. Finally we study the linearized stability of some examples.
Desingularization of binomial varieties in arbitrary characteristic. Part I. A new resolution function and their properties
Authors: Blanco Rocío
Published: May 2012

In this paper we construct a resolution function that will provide an algorithm of resolution of singularities for binomial ideals, over a field of arbitrary characteristic. For us, a binomial ideal means an ideal generated by binomial equations without any restriction, including monomials andp‐th powers, wherepis the characteristic of the base field.

This resolution function is based in a modified order function, calledE‐order. TheE‐order of a binomial ideal is the order of the ideal along a normal crossing divisorE. The resolution function allows us to construct an algorithm ofE‐resolution of binomial basic objects, that will be a subroutine of the main resolution algorithm.
MOXE: A model of gas exchange for hyperpolarized 129Xe magnetic resonance of the lung
Authors: Chang Yulin V.
Published: May 2012

We present a model of gas exchange for hyperpolarized 129Xe in the lung, which we refer to as the Model of Xenon Exchange. The model consists of two expressions and characterizes uptake of dissolved xenon in the lung at two different resonance frequencies. The two expressions are governed by the following five critical pulmonary parameters that characterize both lung function and structure: the surface‐area‐to‐volume ratio, barrier‐to‐septum ratio (ratio between air–blood barrier thickness and septal thickness), hematocrit, gas‐exchange time constant, and pulmonary capillary transit time. The model is first validated by computer simulation. We show that Model of Xenon Exchange can be used to measure the pulmonary parameters mentioned above under various pathological or physiological conditions and is robust against moderate noise. Model of Xenon Exchange is further used to fit an existing data set of xenon uptake, thereby we demonstrate that the data can be well interpreted with Model of Xenon Exchange and reasonable parameters from the fitting routine. The good results obtained in both simulation and fitting to real data indicate that the model is sensitive to various functional and structural changes of the lung, and that it will allow for screening for a variety of pulmonary diseases by using hyperpolarized 129Xe of the lung. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.
Prospective motion correction using tracking coils
Authors: Qin Lei , Schmidt Ehud J. , Tse Zion Tsz Ho , Santos Juan , Hoge William S. , Tempany‐Afdhal Clare , Butts‐Pauly Kim , Dumoulin Charles L.
Published: May 2012

Intracavity imaging coils provide higher signal‐to‐noise than surface coils and have the potential to provide higher spatial resolution in shorter acquisition times. However, images from these coils suffer from physiologically induced motion artifacts, as both the anatomy and the coils move during image acquisition. We developed prospective motion‐correction techniques for intracavity imaging using an array of tracking coils. The system had <50 ms latency between tracking and imaging, so that the images from the intracavity coil were acquired in a frame of reference defined by the tracking array rather than by the system's gradient coils. Two‐dimensional gradient‐recalled and three‐dimensional electrocardiogram‐gated inversion‐recovery‐fast‐gradient‐echo sequences were tested with prospective motion correction using ex vivo hearts placed on a moving platform simulating both respiratory and cardiac motion. Human abdominal tests were subsequently conducted. The tracking array provided a positional accuracy of 0.7 ± 0.5 mm, 0.6 ± 0.4 mm, and 0.1 ± 0.1 mm along the X, Y, and Z directions at a rate of 20 frames‐per‐second. The ex vivo and human experiments showed significant image quality improvements for both in‐plane and through‐plane motion correction, which although not performed in intracavity imaging, demonstrates the feasibility of implementing such a motion‐correction system in a future design of combined tracking and intracavity coil. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.
Normokalemic periodic paralysis is not a distinct disease
Authors: Song Young‐Wha , Kim Sung‐Jo , Heo Tae‐Hwe , Kim Man‐Ho , Kim June‐Bum
Published: May 2012

Introduction: Recent molecular studies of the original cases of normokalemic periodic paralysis (normoKPP) have raised suspicions that these families actually had hyperkalemic periodic paralysis (hyperKPP) due to mutations in the skeletal muscle sodium channel gene SCN4A. However, there is still a debate about the existence of normoKPP. Methods: We screened 230 individuals with primary periodic paralysis for mutations in the SCN4A, CACNA1S, and KCNJ2 genes. All patients had either a hyperKPP or a hypoKPP phenotype, and none had a normoKPP phenotype. Results: In 4 hyperKPP patients from 2 families, molecular analyses revealed Arg675Gly and Arg675Gln mutations of SCN4A, which were previously reported to cause normoKPP. Each patient exhibited the characteristic clinical and laboratory features (including hyperkalemia during spontaneous attacks) of hyperKPP. Conclusion: Our findings support the notion that normoKPP is not a distinct disease. Muscle Nerve, 2012
Relating applied strain to the type and severity of structural damage in the rat median nerve using second harmonic generation microscopy
Authors: Sinclair Elaine B. , Andarawis‐Puri Nelly , Ros Stephen J. , Laudier Damien M. , Jepsen Karl J. , Hausman Michael R.
Published: May 2012

Introduction: Stretch injuries in peripheral nerves can cause pain, paralysis, and loss of sensation. Although optimal treatment depends on the degree of injury, it is difficult to determine the severity of induced nerve damage. Methods: The load–deformation curves of rat median nerves were generated from monotonic load‐to‐failure experiments to determine low, medium, and high strain levels. Additional excised median nerves were then elongated to induce damage at low (4%), medium (10% and 12%), and high (14% and 20%) tensile strains and the resulting structural damage was evaluated using second harmonic generation (SHG) imaging and light microscopy. Results: No substantial structural changes occurred at 4% strain, but higher strain values resulted in disruption of the normal collagen architecture. Conclusions: The results demonstrate a spectrum of structural damage that can be monitored using SHG, a non‐destructive imaging modality, and that the pattern of damage may correspond to functional deficit. Muscle Nerve, 2012
Myasthenic crisis patients who require intensive care unit management
Authors: Sakaguchi Hideya , Yamashita Satoshi , Hirano Teruyuki , Nakajima Makoto , Kimura En , Maeda Yasushi , Uchino Makoto
Published: May 2012

The purpose of this report was to investigate predictive factors that necessitate intensive care in myasthenic crisis (MC). We retrospectively reviewed MC patients at our institution and compared ICU and ward management groups. Higher MG‐ADL scale scores, non‐ocular initial symptoms, infection‐triggered findings, and higher MGFA classification were observed more frequently in the ICU group. In patients with these prognostic factors, better outcomes may be obtained with early institution of intensive care. Muscle Nerve 46: 440–442, 2012
Cell surface complement regulators moderate experimental myasthenia gravis pathology
Authors: Kusner Linda L. , Halperin Jose A. , Kaminski Henry J.
Published: May 2012

Introduction:

Intrinsic mouse complement regulators influence the severity of passively induced experimental acquired myasthenia gravis (EAMG). To assess the potential influence of CD59b in the absence of CD59a background, we used the mCD59ab−/− mouse model to re‐evaluate mCD59 in protecting the neuromuscular junction (NMJ).

Methods:

EAMG was induced with monoclonal antibody to the acetylcholine receptor (AChR) in Daf1−/−, CD59ab−/−, Daf1−/−CD59ab−/−, and wild‐type C57Bl/6 mice. Animals were monitored throughout the experiment. Diaphragms were analyzed for NMJ injury.

Results:

Daf1−/−CD59ab−/− mice required euthanasia 24 hours after disease induction because of severe weakness. Histological assessment demonstrated reduced AChR density, simplification of synaptic folds, and disrupted mitochondria. CD59ab‐deficient mice demonstrated mild weakness and reduction in weight after 24 hours. In contrast, Daf1−/− had more severe weakness at 60 hours. The NMJ of EAMG‐induced Daf1−/− and CD59ab−/− mice demonstrated similar AChR density.

Conclusion:

NMJs of CD59 and DAF mice are protected from complement‐mediated injury of passive EAMG. Muscle Nerve, 2013
Capturing cases of distal symmetric polyneuropathy in a community
Authors: Callaghan Brian , Kerber Kevin , Longoria Ruth , Feldman Eva , Lisabeth Lynda
Published: May 2012

Introduction:

Little is known about what constitutes appropriate diagnostic testing in patients with distal symmetric polyneuropathy (DSP).

Methods:

Utilizing an ICD‐9 screening method and medical record abstraction, we determined the number of new cases of DSP within community neurology practices in Nueces County, Texas. We then compared 2 case capture methods (ICD‐9 vs. all‐case review screening).

Results:

The ICD‐9 case capture method identified 52 cases over a 3‐month period. Comparing case capture methods, the ICD‐9 method identified 16 of 17 cases identified by the all‐case review method (94%). The ICD‐9 method required screening of 84% fewer charts compared with the all‐case review.

Conclusions:

Many new cases of DSP occur each month within Nueces County. The ICD‐9 screening technique combined with medical abstraction is an efficient method to identify new DSP cases in this community. These findings are critical for future epidemiological investigations into patients with DSP. Muscle Nerve, 2012
Diabetes increases mechanical sensitivity and causes morphological abnormalities in the sural nerve that are prevented by treadmill training
Authors: Severo Do Nascimento Patrícia , Lovatel Gisele Agustini , Ilha Jocemar , Schaan Beatriz D'agord , Achaval Matilde
Published: May 2012

Introduction:

In this investigation we evaluated the effects of treadmill training on mechanical sensitivity and sural nerve morphology in diabetic rats.

Methods:

Rats were divided into 3 groups: control (C); diabetic (D); and trained diabetic (TD). Training was performed for 8 weeks. Mechanical sensitivity was evaluated using von Frey filaments. Sural nerve analysis included fiber area, diameter, density of myelinated fibers, area occupied by connective tissue, myelin sheath thickness, and g‐ratio.

Results:

Animals in the D group had a reduced mechanical sensitivity threshold. Morphometric study showed that the D group had a smaller myelinated fiber area and diameter, higher density of fibers and area occupied by connective tissue, thinner myelin sheath, and higher g‐ratio. The D group had a higher percentage of small myelinated fibers and a lower percentage of large‐diameter myelinated fibers than the C and TD groups.

Conclusion:

Training prevents functional and morphological abnormalities in the sural nerve caused by diabetes. Muscle Nerve, 2013
Use of hand diagrams in screening for ulnar neuropathy: Comparison with electrodiagnostic studies
Authors: Werner Robert A. , Chiodo Tony , Spiegelberg Teresa , Franzblau Alfred
Published: May 2012

Introduction:

The objective of this study was to determine whether a hand diagram could be used to predict ulnar mononeuropathy.

Methods:

This was a prospective study of 117 consecutive patients referred for hand symptoms. Each subject filled out a hand diagram of symptoms and had median and ulnar sensory and motor nerve conduction studies, including ulnar conduction across the elbow.

Results:

The best model for predicting an ulnar mononeuropathy included hand diagram scores of definite or possible. The model had a sensitivity of 50% and specificity of 93% with an ROC area of 0.90.

Conclusions:

The ulnar hand diagram scoring system can be useful as a screening tool in the electrodiagnostic laboratory or for epidemiologic studies. Muscle Nerve, 2012
Discharge rates in electromyography distinguish early between peripheral and central paresis
Authors: Jürgens Tim P. , Puchner Christoph , Schulte‐Mattler Wilhelm J.
Published: May 2012

Introduction:

Abnormally increased discharge rates (DRs) of motor unit potentials on concentric needle electromyography (CNEMG) indicate a loss of motor units in peripheral neurogenic lesions.

Methods:

To determine when increased DRs occur during the course of a peripheral nerve lesion, we retrospectively analyzed CNEMG recordings of 19 patients with acute weakness of peripheral origin.

Results:

The initial CNEMG studies took place from 3.7 hours to 10 days after the onset of the lesion. Abnormally increased DRs (≥20/s) were found in all but 1 of the muscles in which MRC grade was <4. Peripheral neurogenic damage was confirmed in all patients thereafter. The DRs depended on neither the kind of lesion nor the time between onset and CNEMG examination.

Conclusions:

The measurement of DRs of motor unit potentials is helpful immediately after a sudden paresis of MRC grade 3 or worse to differentiate between a central and a peripheral lesion. Muscle Nerve 46: 596–598, 2012
Neurophysiological examination of dorsal sural nerve
Authors: Frigeni Barbara , Cacciavillani Mario , Ermani Mario , Briani Chiara , Alberti Paola , Ferrarese Carlo , Cavaletti Guido
Published: May 2012

Introduction:

Nerve conduction study of the dorsal sural nerve (DSN) has been reported to be a sensitive method for early detection of peripheral neuropathies. However, normal reference values are scarce and vary greatly among the different studies.

Methods:

A comprehensive neurophysiological study, including nerve conduction velocity (NCV) and sensory nerve action potential (SNAP) recording, was performed in 294 healthy subjects (21–86 years) with no evidence of neuropathy.

Results:

The amplitude of the DSN SNAP ranged from 2.50 to 15.90 μV, and NCV ranged from 28.9 to 52.8 m/s. A significant age‐related decrease in DSN SNAP amplitude and NCV was observed. The mean ratio of sural NCV to DSN NCV was 1.33 ± 0.19, and the mean ratio of sural nerve SNAP amplitude to DSN SNAP amplitude was 3.17 ± 1.33.

Conclusion:

These normative data of the DSN might be used as reference values for the study of this very distal peripheral nerve. Muscle Nerve, 2012
Use of in vivo bioluminescence and MRI to determine hyperthermia‐induced changes in luciferase activity under the control of an hsp70 promoter
Authors: Hundt Walter , Schink Christian , Steinbach Silke , O'Connell‐Rodwell Caitlin E. , Mayer Dirk , Burbelko Mykhaylo , Kießling Andreas , Guccione Samira
Published: May 2012

We investigated the in vivo effect of hyperthermia on the expression of heat shock proteins and MRI changes in three tumor cell lines. Three tumor cell lines (SCCVII, NIH3T3, M21) were transfected with a plasmid containing the heat shock protein 70 gene (hsp70) promoter fragment and the luciferase reporter gene, and injected into mice. Tumors of 1100 mm3 in size were exposed to five different temperatures (38, 40, 42, 44 and 46 °C) in a water bath. Bioluminescence and MRI were performed at set time intervals. The MRI scan protocol was as follows: T1‐weighted spin echo ± contrast medium, T2‐weighted fast spin echo, dynamic contrast‐enhanced MRI, diffusion‐weighted stimulated echo acquisition mode sequence, T2 time obtained on a 1.5T General Electric MRI scanner. Immunoblotting was also performed. hsp70 transcription was strongly induced at 42 and 44 °C, reaching values as high as 8531.5 ± 432.1‐fold above baseline in NIH3T3 tumors. At these temperatures, significant increases in the uptake of contrast medium, slope of initial enhancement, Akep values and apparent diffusion coefficient (ADC) were observed in the 8‐h scan of the NIH3T3 cell line. In SCCVII tumors, ADC increased by about 23% (p = 0.010) in the scans performed at 8, 24, 48 and 96 h. At 46 °C, luciferase activity was reduced significantly in the three cell lines. In all tumor types, a significant increase in ADC was observed, which was highest in SCCVII tumors (33.8%; p < 0.01). In accordance with the bioluminescence results, significant Hsp70 protein production was shown by immunoblot analysis. The best correlation coefficient between luciferase activity and immunoblotting results was found for M21 tumors (r = 0.93, p < 0.0001). Different tissue types display distinct patterns of hsp70 transcription. MRI can be used, in combination with optical imaging, to provide information on hsp70 transcription and protein production. The major finding of the present study was that heat‐related biochemical changes in tumor tissue can be determined by MRI. Copyright © 2012 John Wiley & Sons, Ltd.
Prediction of the experimental regioselectivity of C60 fullerene bis‐adducts
Authors: Chaker Leila , Yongye Austin B. , Nefzi Adel , Martínez‐Mayorga Karina
Published: May 2012

Regiochemical control of multiple additions to the fullerene core of C60 is attractive and feasible but not fully understood. Specifically, the second nucleophilic addition of bis‐adducts produces unpredicted products. Here, we sought to elucidate the extent to which the first addition influenced, electronically and structurally, the regioselectivity of the second nucleophilic attack on C60 fullerene by exploring three combinations of N‐(diphenyl‐methylene)glycinate and malonate addends connected through 1,3‐benzenedimethanol. Molecular orbitals of C60 and the N‐(diphenyl‐methylene)glycinate and malonate mono‐adducts were determined at the B3LYP/6‐31G**/B3LYP/3‐21G* level of theory. We observed that employing only the lowest unoccupied molecular orbital (LUMO) coefficients was not sufficient to understand the regioselectivity of the tethered second addend. Also, structural perturbations due to the presence of the first addend were largely local. These findings suggested that the selectivity should be explained by the combination of the orbital coefficient and the thermodynamic factors. Thus, the structure and the stability of 21 bis‐adducts of C60 fullerene, containing bis‐methano, bis‐dihydropyrrole, or methanodihydropyrrole, were optimized at the PCM/B3LYP/6‐31G*//PCM/B3LYP/3‐21G*//B3LYP/3‐21G* level of theory. In all cases, the relative energies and Boltzmann populations of the bis‐adducts were in agreement with the main regioisomers obtained experimentally. This study showed that the regioselectivity of the second addition is governed by electronic contributions (LUMO coefficients) and by the strong effect of the strain produced by the linker and the addends (three‐membered and/or five‐membered rings). This insight should be taken into consideration when designing the synthesis of functionalized fullerenes. Copyright © 2012 John Wiley & Sons, Ltd.
Synthesis of branch‐ring‐branch tadpole‐shaped [linear‐poly(ε‐caprolactone)]‐b‐[cyclic‐poly(ethylene oxide)]‐b‐ [linear‐poly(ε‐caprolactone)] by combination of glaser coupling reaction with ring‐opening polymerization
Authors: Fan Xiaoshan , Tang Tingting , Huang Kun , Wang Guowei , Huang Junlian
Published: May 2012

A novel amphiphilic branch‐ring‐branch tadpole‐shaped [linear‐poly(ε‐caprolactone)]‐b‐[cyclic‐poly(ethylene oxide)]‐b‐[linear‐poly(ε‐caprolactone)] [(l‐PCL)‐b‐(c‐PEO)‐b‐(l‐PCL)] was synthesized by combination of glaser coupling reaction with ring‐opening polymerization (ROP) mechanism. The self‐assembling behaviors of (l‐PCL)‐b‐(c‐PEO)‐b‐(l‐PCL) and their π‐shaped analogs of poly(ε‐caprolactone)/poly(ethylene oxide)]‐b‐poly(ethylene oxide)‐b‐[poly(ε‐caprolactone)/poly(ethylene oxide) with comparable molecular weight in water were preliminarily investigated. The results showed that the micelles formed from the former took a fiber look, however, that formed from the latter took a spherical look. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Bioactive mesoglobules of poly(di(ethylene glycol) monomethyl ether methacrylate)–peptide conjugate
Authors: Trzcinska Roza , Szweda Dawid , Rangelov Stanislav , Suder Piotr , Silberring Jerzy , Dworak Andrzej , Trzebicka Barbara
Published: May 2012

This study describes the synthesis and aggregation behavior of thermosensitive poly(di(ethylene glycol) monomethyl ether methacrylate) (P(DEGMA‐ME)) conjugated with the fluorescently labeled pentapeptide glycine‐arginine‐lysine‐phenylalanine‐glycine‐dansyl (GRKFG‐Dns). The GRKFG‐Dns was obtained using Fmoc solid‐phase peptide synthesis and was modified with 2‐bromopropionic acid to initiate an atom transfer radical polymerization of di(ethylene glycol) monomethyl ether methacrylate (DEGMA‐ME). The polymerization led to a well‐defined P(DEGMA‐ME)–GRKFG‐Dns conjugate with a number average molar mass of 108,000 g/mol. The pentapeptide acted as a hydrophilic moiety that increased the phase transition temperature compared to the P(DEGMA‐ME) homopolymer of similar molar mass. The bioconjugate macromolecules aggregated in dilute aqueous solution into spherical particles (mesoglobules). The sizes of aggregates were easily controlled by changing the concentration and heating rate of the P(DEGMA‐ME)‐GRKFG‐Dns solution. The weight average molar masses and sizes of mesoglobules were determined based on light scattering measurements. Enzymatic hydrolysis of the bioconjugate in dilute solution was performed at temperatures below and above the cloud point temperature of the bioconjugate. The peptides were fully accessible to enzymatic digestion even when the macromolecules were aggregated to mesoglobules, indicating that the peptide segments in mesoglobules formed the external shell of the nanoparticles and could be easily released by enzymes. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Postfunctionalization of polyoxanorbornene via sequential Michael addition and radical thiol‐ene click reactions
Authors: Durmaz Hakan , Butun Muge , Hizal Gurkan , Tunca Umit
Published: May 2012

We demonstrated the successful postfunctionalization of poly(oxanorbornene imide) (PONB) with two types of double bonds using sequential orthogonal reactions, nucleophilic thiol‐ene coupling via Michael addition and radical thiol‐ene click reactions. First, the synthesis of PONB with side chain acrylate groups is carried out via ring‐opening metathesis polymerization and nitroxide radical coupling reaction, respectively. Subsequently, the resulting polymer having two different orthogonal functionalities, main chain vinyl and side chain acrylate, is selectively modified via two sequential thiol‐ene click reactions, nucleophilic thiol‐ene coupling via Michael addition and photoinduced radical thiol‐ene. The orthogonal reactivity of two diverse double bonds, vinyl and acrylate functionalities, for the abovementioned consecutive thiol‐ene click reactions was first demonstrated on the model compound. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Formation of a crosslinked POSS network by an unusual hydrosilylation: Thermo‐oxidative stabilization of the α‐cristobalite phase in its amorphous regions
Authors: Kolel‐Veetil Manoj K. , Fears Kenan P. , Qadri Syed B. , Klug Christopher A. , Keller Teddy M.
Published: May 2012

A semicrystalline inorganic–organic hybrid crosslinked network containing polyhedral oligomeric silsesquioxane (POSS) cores was constructed by the unusual hydrosilylation of the terminal vinyl groups of an internal acetylene‐containing silane linker by a POSS monomer. Products from the thermal treatments of this network in either argon or air at 250, 550, and 1000 °C, respectively, were characterized by Fourier transform infrared, Solid‐state 13C and 29Si magic angle spinning NMR, X‐ray diffraction and XPS analyses. The highly symmetrically functionalized POSS silica clusters, in the fluorite silica phase, in the network were found to remain unchanged on thermal treatment possibly due to the shielding of the silica core by the functionalities and a cancellation of thermal stresses on the silica core. Stabilization of the metastable α‐cristobalite phase, which is typically formed on cooling by a β‐ to α‐transition of the β‐cristobalite phase formed above 1400 °C, was observed in the amorphous regions in the network sample treated only to 1000 °C in air. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Phospha‐Michael addition to enone‐containing triglyceride derivatives as an efficient route to flame retardant renewable thermosets
Authors: Moreno Maryluz , Lligadas Gerard , Ronda Joan C. , Galià Marina , Cádiz Virginia
Published: May 2012

A novel phosphorus‐containing vegetable oil (PETR) was prepared through phospha‐Michael addition of a diphenyl phosphine oxide to the enone derivative of high‐oleic sunflower oil (ETR). The reaction was investigated using the enone derivative of methyl oleate under conventional thermal heating and microwave irradiation. The kinetic study showed a great enhancement of reaction rate for the microwave‐initiated addition. The crosslinking of ETR with diaminodiphenylmethane (DDM) via aza‐Michael addition was also investigated under microwave irradiation, showing a noticeable acceleration of the curing. The new phosphorus‐containing triglyceride was crosslinked with DDM to obtain phosphorus‐containing vegetable oil‐based thermosets of different phosphorus contents. Limiting oxygen index values from 26.4 to 35.0 for the final materials were obtained, demonstrating that the flame retardant properties of vegetable oil‐based thermosets can be improved by adding covalently bonded phosphorus to the polymer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
In situ formation of Sn(IV) catalyst with increased activity in ε‐caprolactone and L‐lactide polymerization using stannous(II) 2‐ethylhexanoate
Authors: Chen Hsuan‐Ying , Fang Hsin‐Jou , Chen Yen‐Jen , Hsu Sodio C. N. , Lai Yi‐Chun , Ou Hsiu‐Wei , Peng Wei‐Te , Chang Ya‐Ju , Tsou Yu‐Chi , Wu Ting‐Yi , Chung Hsuan , Chen Yun , Huang Ta Chou , Wu Bo Sheng
Published: May 2012

Ring‐opening polymerization (ROP) of ε‐caprolactone and L‐lactide (LA) was studied using stannous(II) 2‐ethylhexanoate (Sn(Oct)2) with N,N‐dimethylformamide‐dimethyl acetal (DMF‐DMA). DMF‐DMA showed a tenfold improvement in catalytic activity over that of Sn(Oct)2 under the same conditions. It also enhanced the capability to control molecular weight in the synthesis of small molecular weight polymers of polycaprolactone and polylactide (PLA). The high molecular weight polymerization demonstrated a strong capability to control molecular weight for the polymerization of LA: a molecular weight of PLA exceeding 400,000 was obtained at very low catalytic loadings. The individual polymerization rates of other tin reagents with DMF‐DMA also clearly increased. Applying this methodology could drastically reduce the time and cost required for the fabrication of these products to increase the competitive advantage of manufacturers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Fabrication and proton conductivity of sulfonated silica composites prepared by postoxidization of mercaptomethoxysilane
Authors: Yasumoto Kazuhiro , Norisuye Tomohisa , Teranishi Yusuke , Tran‐Cong‐Miyata Qui , Nomura Shigeki
Published: May 2012

Sol–gel derived organic–inorganic hybrids containing phosphotungstic acid (PWA) have been prepared previously to obtain proton conductive membranes. However, leaking of PWA was a serious problem to achieve the higher proton conductivity. In this study, polyelectrolyte membranes functionalized with sulfonic acid groups were fabricated by the sol–gel method. Proton conductivity measurements were performed on an impedance analyzer at 80°C/95% RH. The functionalized polyelectrolyte membranes exhibited the proton conductivity σ ∼ 0.9 (S/cm) which was much higher than the previously reported hybrids containing PWA. Although the hybrids exhibited fairly high proton conductivity irrespective to the catalysts used, that under the low relative humidity strongly depends on the catalysts. Among the hybrids prepared in this study, the membrane synthesized with HCl showed outstanding proton conductive properties even at the low humidity thanks to the proton transport channel formed by the swelling of ionic clusters. This fact was confirmed by measuring the ion exchange capacity, water uptake, swelling rate, Fourier transform infrared spectroscopy, atomic force microscopy, and thermogravimetric analysis. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Novel approaches to flexible visible transparent hybrid films for ultraviolet protection
Authors: Calvo Mauricio E. , Castro Smirnov José R. , Míguez Hernán
Published: May 2012

Herein, we present an overview of the most recent achievements and innovations regarding the development of flexible visible transparent films for selective ultraviolet (UV) shielding, with focus on those based on hybrid inorganic–organic materials. The main synthetic paths used nowadays to ensure a high degree of protection are reviewed. Polymers containing organic UV absorbing molecules, hybrid mixtures of polymers and nanoparticles, and the recently introduced series of structures displaying structural color, are identified as the three main types of materials used for this purpose. The use of biocompatible and flexible films to achieve spectrally selective UV protection can find applications in a wide diversity of fields such as photo‐treatment of skin diseases, food and beverage packing, and storage of cosmetics. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
Martensitic structure and magnetic domain transformation in melt‐spun Ni–Mn–Ga ferromagnetic ribbons
Authors: Chen Fenghua , Zhang Mingang , Chai Yuesheng , Gong Changwei
Published: May 2012

Ni53Mn23.8Ga23.2 ribbons were fabricated by melt‐spinning and subsequent high vacuum annealing process. The structure and magnetic properties of the as‐spun and annealed ribbons were investigated by X‐ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimeter (DSC), and vibrating sample magnetometer. All the samples exhibit an orthorhombic structure of a seven‐layered modulation at room temperature. The martensitic and its reverse transformation were clearly observed on all the samples. With increasing annealing temperature, the saturation magnetization increases while the coercivity decreases. It was found that the transformation becomes drastic in the sample annealed at 1073 K. In addition, an in situ observation on the evolution of magnetic domain patterns with temperature was carried out by means of magnetic force microscopy (MFM).
Strain–polarisation coupling and elastic constant determined from polarisation and strain curves in order–disorder uniaxial ferroelectrics
Authors: Gałązka Mirosław , Zieliński Piotr
Published: May 2012

A practical method is developed to determine the strain dependence of the pseudospin–pseudospin interaction parameters in discrete models of the continuous order–disorder improper ferroelastic phase transitions from experimental data on the primary order parameter (polarisation). The temperature dependence of the mechanical strain can be then deduced from the spontaneous polarisation data only. It is also shown that the dependence of the elastic constant on the temperature can be obtained from the polarisation and the strain data. The temperature dependences of the coupling constant and the elastic constant between the molecular dipoles of the methylammonium ions in the uniaxial ferroelectrics (CH3NH3)5Bi2Cl11(MAPCB) and (CH3NH3)5Bi2Br11(MAPBB) are determined and shown to be at the origin of the particular shape of the polarisation and the strain curves.
Progress in growth, fabrication, and characterization of semiconductor photonic crystal nanocavities [Phys. Status Solidi B 248, No. 4, 892–896 (2011)]
Authors: Richards B. C. , Hendrickson J. , Olitzky J. D. , Gibson R. , Gehl M. , Kieu K. , Polynkin P. , Khitrova G. , Gibbs H. M. , Khankhoje U. K. , Homyk A. , Scherer A. , Kim J.‐Y. , Lee Y.‐H.
Published: May 2012

An error was made in the calculation of the photonic crystal mode volume. Fixing this error increases our mode volume by a factor of 2 and makes our claim of highest Q/V invalid.
Investigation of absolute and relative response for three different liquid chromatography/tandem mass spectrometry systems; the impact of ionization and detection saturation
Authors: Nilsson Lars B. , Skansen Patrik
Published: May 2012

RATIONALE

The investigations in this article were triggered by two observations in the laboratory; for some liquid chromatography/tandem mass spectrometry (LC/MS/MS) systems it was possible to obtain linear calibration curves for extreme concentration ranges and for some systems seemingly linear calibration curves gave good accuracy at low concentrations only when using a quadratic regression function.

METHODS

The absolute and relative responses were tested for three different LC/MS/MS systems by injecting solutions of a model compound and a stable isotope labeled internal standard. The analyte concentration range for the solutions was 0.00391 to 500 μM (128 000×), giving overload of the chromatographic column at the highest concentrations. The stable isotope labeled internal standard concentration was 0.667 μM in all samples.

RESULTS

The absolute response per concentration unit decreased rapidly as higher concentrations were injected. The relative response, the ratio for the analyte peak area to the internal standard peak area, per concentration unit was calculated. For system 1, the ionization process was found to limit the response and the relative response per concentration unit was constant. For systems 2 and 3, the ion detection process was the limiting factor resulting in decreasing relative response at increasing concentrations.

CONCLUSIONS

For systems behaving like system 1, simple linear regression can be used for any concentration range while, for systems behaving like systems 2 and 3, non‐linear regression is recommended for all concentration ranges. Another consequence is that the ionization capacity limited systems will be insensitive to matrix ion suppression when an ideal internal standard is used while the detection capacity limited systems are at risk of giving erroneous results at high concentrations if the matrix ion suppression varies for different samples in a run. Copyright © 2012 John Wiley & Sons, Ltd.
A simplified method for busulfan monitoring using dried blood spot in combination with liquid chromatography/tandem mass spectrometry
Authors: Ansari Marc , Uppugunduri Chakradhara Rao S. , Déglon Julien , Théorêt Yves , Versace François , Gumy‐Pause Fabienne , Ozsahin Hulya , Dayer Pierre , Desmeules Jules , Daali Youssef
Published: May 2012

RATIONALE

Busulfan (Bu) is an important component of the myeloablative conditioning regimen prior to hematopoietic stem cell transplantation (HSCT) especially in children. Intravenously administered Bu exhibits a therapeutic window phenomenon requiring therapeutic drug monitoring. Analytical methods developed for Bu routine monitoring were aimed at using low volumes of biological fluids and development of simple procedures to facilitate the dosage adjustment. In this report, we describe a simple, rapid method for Bu measurement using dried blood spots (DBS) from only 5 μL of whole blood.

METHODS

Bu extracted from DBS with methanol was measured by high‐performance liquid chromatography with electrospray ionization and tandem mass spectrometry in multiple reaction monitoring mode using D8‐Bu as an internal standard. The method was in‐house validated evaluating trueness, repeatability, within‐laboratory reproducibility, specificity and the lower limit of quantification (LLOQ).

RESULTS

The method was linear in the calibration range of 100–2000 ng mL–1 (r2 >0.99) encompassing the therapeutic concentrations of Bu. A good trueness (<14%), precision (<10%), and recovery (100%) were observed during validation of the method with quality controls of 300, 600 and 1400 ng mL–1. The LLOQ was determined as 50 ng mL–1 and no matrix or carryover effects were observed. The validated method was applied to measure Bu levels in four children receiving infusion of Bu prior to HSCT. A good correlation was observed between the Bu levels measured by DBS and dried plasma spot (DPS) (r2 = 0.96) and between DPS and the GC/MS method (r2 = 0.92). Bu was found to be stable in DBS up to 6 h at room temperature and for 24 h at 4°C.

CONCLUSIONS

The new DBS method facilitates earlier dosage adjustment during Bu therapy by its specific and simple procedure using 5 μL of whole blood. Copyright © 2012 John Wiley & Sons, Ltd.
Active capillary plasma source for ambient mass spectrometry
Authors: Nudnova Maryia M. , Zhu Liang , Zenobi Renato
Published: May 2012

RATIONALE

Imaging mass spectrometry with high spatial resolution has become a rapidly developing area of mass spectrometric research. Many scientific and industrial problems deal with mass spectrometric analysis at ambient pressures. This requires efficient transport and ionization of small amounts of substance.

METHODS

An active sampling capillary based on a dielectric barrier discharge was constructed for ambient mass spectrometry. The capillary serves as an ionization source as well as an atmospheric interface of the mass spectrometer. The analyzed samples are transported through the sampling capillary due to the pressure difference between the atmospheric environment and the vacuum in the mass spectrometer. Ionization of the transported samples is provided by a low‐temperature dielectric barrier discharge. This active capillary was shown to work in a robust fashion for ionizing both gas‐phase and laser‐ablated solid‐phase samples.

RESULTS

The geometry of the electrodes was found to play a crucial role in ionization efficiency. The capillary was optimized in order to perform surface analysis of solid samples. Sensitivity tests were carried out to characterize different active capillary constructions. The sensitivity of the constructed active capillary was 0.1 ppb (relative concentration of a gaseous sample in ambient air). The active capillary was able to detect samples evaporated from a solid surface. With the active capillary source, it was possible to detect anthracene traces evaporated from a surface located 3 cm from the capillary inlet.

CONCLUSIONS

A plasma‐based active capillary ionization source was constructed. This concept of an active sample inlet should broaden the range of applications of ambient mass spectrometry. Copyright © 2012 John Wiley & Sons, Ltd.
Isomerization of cannabidiol and Δ9‐tetrahydrocannabinol during positive electrospray ionization. In‐source hydrogen/deuterium exchange experiments by flow injection hybrid quadrupole‐time‐of‐flight mass spectrometry
Authors: Broecker Sebastian , Pragst Fritz
Published: May 2012

RATIONALE

Liquid chromatography/tandem mass spectrometry (LC/MS/MS) is frequently used for analysis of cannabinoids in drug abuse control. Despite differences in structure, the isomers Δ9‐tetrahydrocannabinol (THC) and cannabidiol (CBD) provide identical fragment spectra after positive electrospray ionization (ESI). For elucidation of the reason, hydrogen/deuterium (H/D) exchange experiments were performed.

METHODS

Solutions of THC and CBD in D2O/acetonitrile (50:50, v/v) were flow‐injected into acetonitrile as the mobile phase and measured by hybrid quadrupole‐time‐of‐flight mass spectrometry (FI‐QTOF‐MS) in targeted MS/MS mode. The MS and collision‐induced dissociation (CID) spectra at 10, 20 and 40 eV were interpreted with respect to number and position of exchanged hydrogen atoms. For comparison the same measurements were preformed in H2O, after addition of 0.5% formic acid and with negative ESI.

RESULTS

Depending on injected volume and position in the response curve, up to 7 or 8 hydrogen atoms were exchanged by deuterium in THC or CBD. Positive ESI CID spectra were available for precursors with up to 4 exchanged D‐atoms and showed that besides the OH groups also an H/D exchange at carbon atoms of the non‐aromatic part of the molecules occurred for both THC and CBD. After negative ESI, no H/D exchange in addition to the OH groups and different CID spectra of both substances was found.

CONCLUSIONS

Injection of the investigated substances in D2O and measurement by FI‐QTOF‐MS proved to be an efficient way to perform H/D exchange experiments. The results were interpreted as an acid‐catalyzed in‐source equilibration between THC and CBD leading to the same precursor ions and to an H/D exchange in the methyl groups under the increased acidic conditions in the positive ESI droplets. Therefore, in positive LC/ESI‐MS/MS, peak identification by CID spectra or by abundance ratio of multiple reaction monitoring (MRM) transitions is not sufficient for unambiguous discrimination between THC and CBD and must be supported by retention time or other experimental evidence. Copyright © 2012 John Wiley & Sons, Ltd.
Analysis of plasma nucleotides in rat by micellar electrokinetic capillary chromatography/electrospray ionization mass spectrometry
Authors: Bhowmik Salil Kumar , Jung Byung Hwa
Published: May 2012

RATIONALE

The aim of this study was to establish a simultaneous quantitative analysis method of nine endogenous nucleotides in rat plasma using micellar electrokinetic capillary chromatography/electrospray ionization mass spectrometry (MEKC/ESI‐MS).

METHODS

To select the optimum conditions for separation of the nucleotides, various pH, concentrations of running buffers and surfactants were tested. Ammonium acetate (20 mM) containing the surfactant dodecyltrimethylammonium bromide (2 mM, pH 3.5) was selected as the micellar running buffer. The plasma samples were prepared by precipitating the proteins with 2 mM EDTA in 60% ethanol. The samples were analyzed using capillary electrophoresis (CE)/MS and selected ion monitoring (SIM) mode with positive ionization. CE was performed using a silica capillary column in reversed polarity mode.

RESULTS

The limits of detection (LODs) and limits of quantification (LOQs) of the nucleotides ranged from 0.05–5 and 2.0–20 μM, respectively. The calibration curves were linear (R2 >0.99) for all analytes, and the accuracy and precision were within ±15%. The developed method was applied to the analysis of nucleotides in rat plasma that was collected after oral administration of acetaminophen (1000 mg/kg/day) to evaluate the changes in plasma nucleotide levels under hepatotoxic conditions.

CONCLUSIONS

Decreased level of GTP and increased level of cytosine nucleotides were found to be associated with liver toxicity, which led to the conclusion that liver toxicity is closely related to changes in nucleotide levels in plasma. Copyright © 2012 John Wiley & Sons, Ltd.