bluuebunny/crossref_metadata_2025 huggingface dataset:
Brain dynamic neurochemical changes in dystonic patients: A magnetic resonance spectroscopy study
Authors: Marjańska Malgorzata , Lehéricy Stéphane , Valabrègue Romain , Popa Traian , Worbe Yulia , Russo Margherita , Auerbach Edward J. , Grabli David , Bonnet Cecilia , Gallea Cécile , Coudert Mathieu , Yahia‐Cherif Lydia , Vidailhet Marie , Meunier Sabine
Published: December 2012

Measurements of the concentrations of γ‐aminobutyric acid (GABA) and glutamate in the motor cortices and lentiform nuclei of dystonic patients using single‐voxel 1H magnetic resonance spectroscopy (MRS) have yielded conflicting results so far. This study aimed to investigate dynamic changes in metabolite concentrations after stimulation of the motor cortices in patients with upper limb dystonia. Using single‐voxel MRS at 3 T, the concentrations of GABA, glutamate plus glutamine, and N‐acetylaspartate were measured bilaterally in the primary sensorimotor cortex, lentiform nucleus, and occipital region before and after 5‐Hz transcranial magnetic stimulation (TMS) over the dominant motor cortex. Data obtained from 15 patients with upper limb primary dystonia were compared with data obtained from 14 healthy volunteers. At baseline, there was no group difference in concentration of metabolites in any region. rTMS induced a local (in the stimulated motor cortex) decrease of N‐acetylaspartate (P < .006) to the same extent in healthy volunteers and patients. GABA concentrations were modulated differently, however, decreasing mildly in patients and increasing mildly in healthy volunteers (P = .05). There were no remote effects in the lentiform nucleus in either group. The stimulation‐induced changes in metabolite concentrations have been interpreted in view of the increased energy demand induced by rTMS. The dynamics of the GABA concentration were specifically impaired in dystonic patients. Whether these changes reflect changes in the extrasynaptic or synaptic GABA component is discussed. © 2012 Movement Disorder Society
Anti‐tumorigenicity of dietary α‐mangostin in an HT‐29 colon cell xenograft model and the tissue distribution of xanthones and their phase II metabolites
Authors: Chitchumroonchokchai Chureeporn , Thomas‐Ahner Jennifer M. , Li Jie , Riedl Kenneth M. , Nontakham Jannarin , Suksumrarn Sunit , Clinton Steven K. , Kinghorn A. Douglas , Failla Mark L.
Published: December 2012

Scope

This study investigated the in vivo and in vitro activity of α‐mangostin (α‐MG), the most abundant xanthone in mangosteen pericarp, on HT‐29 cell tumorigenicity, proliferation, and several markers of tumor cell activity, as well as the profile and amounts of xanthones in serum, tumor, liver, and feces.

Methods and results

Balb/c nu/nu mice were fed either control diet or diet containing 900 mg α‐MG/kg. After 1 week of acclimation to diet, mice were injected subcutaneously with HT‐29 cells and fed the same diets ad libitum for an additional 2 or 4 weeks. After 2 and 4 weeks, tumor mass and the concentrations of BcL‐2 and β‐catenin in tumors of mice fed diet with α‐MG were significantly less than in mice fed control diet. Xanthones and their metabolites were identified in serum, tumor, liver, and feces. In vitro treatment of HT‐29 cells with α‐MG also inhibited cell proliferation and decreased expression of BcL‐2 and β‐catenin.

Conclusion

Our data demonstrate that the anti‐neoplastic effect of dietary α‐MG is associated with the presence of xanthones in the tumor tissue. Further investigation of the impact of beverages and food products containing xanthones on the prevention of colon cancer or as complementary therapy is merited.
Z and E rotamers of N‐formyl‐1‐bromo‐4‐hydroxy‐3‐methoxymorphinan‐6‐one and their interconversion as studied by 1H/13C NMR spectroscopy and quantum chemical calculations
Authors: Sulima Agnieszka , Cheng Kejun , Jacobson Arthur E. , Rice Kenner C. , Gawrisch Klaus , Lee Yong‐Sok
Published: December 2012

N‐Formyl‐1‐bromo‐4‐hydroxy‐3‐methoxymorphinan‐6‐one (compound 2), an important intermediate in the NIH Opiate Total Synthesis, presumably exists as a mixture of two rotamers (Z and E) in both CHCl3 and DMSO at room temperature due to the hindered rotation of its N‐C18 bond in the amide moiety. By comparing the experimental 1H and 13C chemical shifts of a single rotamer and the mixture of compound 2 in CDCl3 with the calculated chemical shifts of the geometry optimized Z and E rotamers utilizing density functional theory, the crystalline rotamer of compound 2 was characterized as having the E configuration. The energy barrier between the two rotamers was also determined with the temperature dependence of 1H and 13C NMR coalescence experiments, and then compared with that from the reaction path for the interconversion of the two rotamers calculated at the level of B3LYP/6‐31G*. Detailed geometry of the ground state and the transition states of both rotamers are given and discussed. Copyright © 2012 This article is a US Government work and is in the public domain in the USA.
Estrus synchronization and ovarian hyper‐stimulation treatments have negligible effects on cumulus oocyte complex gene expression whereas induction of ovulation causes major expression changes
Authors: Agca Cansu , Yakan Akin , Agca Yuksel
Published: December 2012

The effects of exogenous hormones, used for estrus synchronization and ovarian hyper stimulation, on cumulus oocyte complexes (COCs) gene expression in sexually mature rats were determined using microarrays. Gene expression in COCs collected from GnRH (Gtrt), GnRH + eCG (G + Etrt), and GnRH + eCG + hCG (G + E + Htrt) treatments were compared to COCs from naturally cycling (NC) rats before the preovulatory luteninizing hormone surge. There was no significant difference in gene expression among NC, Gtrt, and G + Etrt; however, over 2,600 genes were significantly different between NC and G + E + Htrt (P < 0.05). Genes upregulated in G + E + Htrt encode for: proteins that are involved in prostaglandin synthesis (Ptgs2, Pla2g4a, and Runx1) and cholesterol biosynthesis (Hmgcr, Sc4mol, and Dhcr24); receptors that allow cholesterol uptake (Ldlr and Scarb1), regulate progesterone synthesis (Star), and inactivate estrogen (Sult1e1); and downstream effectors of LH signal (Pgr, Cebpb, Creb3l1, Areg, Ereg, and Adamts1). Conversely, G + E + Htrt downregulated genes encoding proteins involved in: DNA replication and cell cycle progression (Ccne2, Orc5l, Rad50, and Mcm6); reproductive developmental process; and granulosa cell expansion (Gdf9, Bmp15, Amh, Amhr2, Bmpr1b, Tgfb2, Foxl2, Pde3a, Esr2, Fshr, Ybx2, Ccnd2, Ccnb1ip1, and Zp3); maternal effect genes required for embryo development (Zar1, Npm2, Nlrp5, Dnmt1, H1foo, and Zfp57); amino acid degradation; and ketogenesis (Hmgcs2, and Cpt1b). These results from the rat show that hormones used for estrus synchronization (Gtrt) and ovarian hyper stimulation (G + Etrt) had minimal effects on gene expression, whereas induction of ovulation (G + E + Htrt) caused major changes in gene expression of rat COCs. This study provides comprehensive information about regulated genes during late follicle development and ovulation induction. Mol. Reprod. Dev. © 2013 Wiley Periodicals, Inc.
The Effect of Pure Component Characteristic Parameters on Sanchez–Lacombe Equation‐of‐State Predictive Capabilities
Authors: Bashir Muhammad Ahsan , Al‐haj Ali Mohammad , Kanellopoulos Vasileios , Seppälä Jukka , Kokko Esa , Vijay Sameer
Published: December 2012

The dependence of predictive capabilities of SL EOS on the pure characteristic parameters of monomers and polymers is investigated. A sensitivity analysis study is carried out to understand the effect of these parameters on the predictive capability of SL EOS for different α‐olefin/polyolefins systems. Among all pure component characteristic parameters, the monomer characteristic temperature (T*monomer) has the largest impact on SL EOS predictive capability; whereas the polymer characteristic density (ρ*polymer) is found to have the smallest impact.

magnified image
Recognizing Global Burden of Cardiovascular Disease and Related Chronic Diseases
Authors: Kelly Bridget B. , Narula Jagat , Fuster Valentín
Published: December 2012

Cardiovascular disease is the leading cause of death worldwide, affecting not only high‐income but also low‐ and middle‐income countries. Nearly 80 percent of all estimated cardiovascular disease–related deaths worldwide now occur in low‐ and middle‐income countries, where nearly 30 percent of all deaths are attributable to cardiovascular disease. The health burden of cardiovascular disease and other chronic diseases is also accompanied by a significant deleterious economic impact at the level of both national economies and households. The global trends in the health and economic burden of cardiovascular disease provide a compelling argument in support of prioritizing urgent yet carefully planned efforts to prevent and control cardiovascular disease worldwide—and especially in low‐ and middle‐income countries. After decades of escalating efforts to draw attention to the high burden of cardiovascular disease and other chronic diseases, this critically important issue is now emerging as a more central part of the global health and development agenda. The breadth of behavioral, biological, social, environmental, and systems‐level factors that contribute to cardiovascular disease necessitates multisectoral approaches across the lifecourse that promote healthful lifestyles, reduce risk, and reduce cardiovascular‐disease morbidity and mortality through the delivery of quality health care services. Given that the complex interactions among the determinants of cardiovascular disease vary in different contexts, real progress in control efforts will come through approaches that are driven by a country's disease burden and risk profile, capacities, resources, and priorities—approaches that are led by a country's key decision‐makers and stakeholders, including governments, civil society, the private sector, and communities. Many countries are already establishing efforts to address chronic diseases. In addition to these locally driven efforts, success will require active engagement and sustained action from a wide array of stakeholders operating at global and regional levels. Mt Sinai J Med 79:632–640, 2012. © 2012 Mount Sinai School of Medicine
Should Your Family History of Coronary Heart Disease Scare You?
Authors: Prabhakaran Dorairaj , Jeemon Panniyammakal
Published: December 2012

Traditional risk factors explain most of the risk associated with coronary heart disease, and after adjustment for risk factors family history was believed to contribute very little to population‐attributable risk of coronary heart disease. However, the INTERHEART study demonstrated an independent association of family history of coronary heart disease with acute myocardial infarction. To assess this relationship more comprehensively in multiple datasets in different populations, we carried out a detailed review of the available evidence. Case‐control studies involving 17,202 cases and 30,088 controls yielded a pooled unadjusted odds ratio (random‐effects model, overall I2 = 64.6%, P = 0.000) of 2.03 (95% confidence interval: 1.79–2.30), whereas cohort studies that included 313,837 individuals yielded an unadjusted relative risk for future coronary heart disease (random‐effects model, overall I2 = 88.7%, P = 0.000) of 1.60 (95% confidence interval: 1.44–1.77). Although the presence of family history of coronary heart disease indicates a cumulative exposure of shared genes and environment, the risk estimates for family history did not attenuate significantly after adjustment for conventional coronary heart disease risk factors in several studies. It is probably an oversimplification to dichotomize the family history variable into a simple “yes” or “no” risk factor, as the significance of family history is influenced by several variables, such as age, sex, number of relatives, and age at onset of disease in the relatives. Moreover, a quantitative risk‐assessment model for the family history variable, such as the “family risk score,” has a positive linear relationship with coronary heart disease. More studies are warranted to assess the benefits and risks of intensive interventions, both targeted individually and at the family level, among individuals with a valid family history and borderline elevated risk factors. Mt Sinai J Med 79:721–732, 2012. © 2012 Mount Sinai School of Medicine
Omnipresent Atherosclerotic Disease: Time to Depart From Analysis of Individual Vascular Beds
Authors: Otsuka Fumiyuki , Fuster Valentin , Narula Jagat , Virmani Renu
Published: December 2012

Atherosclerotic vascular disease not only remains the leading cause of death in the Western countries, but it has become the most common cause of morbidity and mortality in the low‐ and middle‐income countries as well. Therefore, better understanding of the pathogenesis of atherosclerotic disease and its prevention are of fundamental importance. It is well known that it affects sequentially the aorta followed by coronary, carotid, peripheral, and intracerebral arteries, with some individual variability. The mechanisms of progression are similar in each of the beds, with increasing lipid accumulation in the arterial wall along with macrophages and T‐cell infiltration, paucity of smooth‐muscle cell proliferation and collagen deposition, and endothelial‐cell dysfunction and hypercoagulability playing an important role at the time of acute manifestations of the disease. Fundamental to this inflammatory process is the presence of classic risk factors, regardless of the involved territory. Therefore, the concept of palliative treatment must be reserved for only those who have progressed beyond preventive measures. Mt Sinai J Med 79:641–653, 2012. © 2012 Mount Sinai School of Medicine
Novel Imaging Strategies for Assessment of Cerebrovascular Involvement
Authors: Tang Cheuk Ying , Narula Jagat , Friedman Joseph I.
Published: December 2012

There is an important correlation between vascular risk factors and nonspecific imaging findings in the brain such as white‐matter hyperintensities. These vascular risk factors are also associated with dementia and lesser forms of cognitive impairment. One hypothesis is that these vascular risk factors lead to disruption of connective networks in the central nervous system that are supported by myelinated white‐matter fibers, which in turn lead to deficits in functional signaling between various brain regions. Another possibility is an alteration of the neurovascular coupling due to vascular risk factors. This reduced functional signaling contributes to the cognitive deficits in persons harboring these vascular risk factors. Lifestyle changes may restore some of these functional deficits through brain plasticity. It is imperative that preclinical diagnostic techniques are developed to identify these early brain changes in persons harboring vascular risk factors, as such efforts may improve primary and secondary prevention efforts. Recently developed imaging techniques may provide objective imaging biomarkers to measure the structural and functional brain changes in persons with vascular risk factors and resulting subclinical atherosclerotic disease. This article reviews a few of these novel imaging techniques. Mt Sinai J Med 79:674–682, 2012. © 2012 Mount Sinai School of Medicine
Generation of large finite‐element matrices on multiple graphics processors
Authors: Dziekonski A. , Sypek P. , Lamecki A. , Mrozowski M.
Published: December 2012

This paper presents techniques for generating very large finite‐element matrices on a multicore workstation equipped with several graphics processing units (GPUs). To overcome the low memory size limitation of the GPUs, and at the same time to accelerate the generation process, we propose to generate the large sparse linear systems arising in finite‐element analysis in an iterative manner on several GPUs and to use the graphics accelerators concurrently with CPUs performing collection and addition of the matrix fragments using a fast multithreaded procedure. The scheduling of the threads is organized in such a way that the CPU operations do not affect the performance of the process, and the GPUs are idle only when data are being transferred from GPU to CPU. This approach is verified on two workstations: the first consists of two 6‐core Intel Xeon X5690 processors with two Fermi GPUs: each GPU is a GeForce GTX 590 with two graphics processors and 1.5 GB of fast RAM; the second workstation is equipped with two Tesla C2075 boards carrying 6 GB of RAM each and two 12‐core Opteron 6174s. For the latter setup, we demonstrate the fast generation of sparse finite‐element matrices as large as 10 million unknowns, with over 1 billion nonzero entries.

Comparing with the single‐threaded and multithreaded CPU implementations, the GPU‐based version of the algorithm based on the ideas presented in this paper reduces the finite‐element matrix‐generation time in double precision by factors of 100 and 30, respectively. Copyright © 2012 John Wiley & Sons, Ltd.
Investigation of elastic constants of polymer/nanoparticles composites using the brillouin spectroscopy and the mechanical homogenization modeling
Authors: Maurice Gérard , Rouxel Didier , Vincent Brice , Hadji Rachid , Schmitt Jean‐François , Taghite M'barek , Rahouadj Rachid
Published: December 2012

A numerical model using homogenization techniques is proposed to simulate the evolution of elastic properties of nanocomposite polymer‐nanoparticles, depending on the concentration of nanoparticles and the rigidity of the particle–matrix interface. To validate this model, it was confronted to several physical systems having different interface behavior, the nanocomposite systems: poly(vinylidene fluoride trifluoroethylene)/Al2O3 (alumina nanoparticles incorporated into copolymer of vinylidene difluoride and trifluoroethylene to form nanocomposite), PMMA/CNT (carbon nanotube/poly(methyl methacrylate) composite) and PMMA/SiO2 with nanoparticles with or without surface treatment of silanization. For all these systems, the Young's modulus (nanoparticles and matrix) has been obtained experimentally from the elastic modulus C11 obtained by Brillouin spectroscopy. These macroscopic measurements coupled with the theoretical model allow a multiscale approach of the elastic behavior of nanocomposite systems, providing information on the global elastic properties of polymer‐nanoparticle material, and also indications about the strength of physical and chemical bonds between the nanoparticles and the matrix. Our results validate the hypothesis of the crucial role of the interface module, provided by numerical simulation which shows that incorporation of nanoparticles may lead to a strengthening or a weakening of the matrix. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers.
Effect of molding condition and pellets material on the weld property of injection molded jute/polylactic acid
Authors: Wang Cuntao , Uawongsuwan Putinun , Yang Yuqiu , Hamada Hiroyuki
Published: December 2012

Natural fibers such as jute fiber and biodegradable poly(lactic acid) (PLA) polymer are very good choices for environmental friendly material. Multi‐gate injection is often used to meet the demand of mass production of injection moldings, therefore weld line is inevitable. The presence of weld lines not only detracts from the surface quality but also significantly reduces the mechanical strength of injection‐molded parts. Although it is not always easy to completely eliminate weld lines, the weld strength could be improved through suitable adjustment of molding conditions such as melt temperature, mold temperature, hold pressure, injection speed, and so on. In this study, three kinds of pellets materials were prepared: long fiber pellets (LFT), the re‐compounding pellets (RP), and LFT50:RP50 hybrid mixtures (LFT/RP). Tensile test was carried out to investigate the effect of different pellets and holding pressures on the mechanical property of welded jute/PLA specimens. And the interfacial shear strength of non‐welded jute/PLA specimens was calculated with Kelly‐Tyson Formula. Fiber separation and fiber dispersion in RP became better than that of LFT which resulted in a better interfacial property. Weld strength of RP and hybrid LFT/RP specimens was improved by 43.34% and 16.46% than that of LFT specimen, respectively. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Color changes due to thermal ageing and artificial weathering of pigmented and textured ABS
Authors: Iannuzzi Giovanna , Mattsson Britta , Rigdahl Mikael
Published: December 2012

Acrylonitrile–butadiene–styrene copolymers (ABS) are known to be sensitive towards ageing which can lead to color changes, primary interest in this study. The color changes were expressed in terms of the CIELAB color system. ABS plaques were subjected to heat ageing and artificial weathering. Uncolored ABS and dark gray colored specimens were employed. The pigmented ABS plaques were also imposed with different surface textures. In general, the uncolored material suffered from the most severe discoloration and the artificial weathering produced the strongest effect. For both types of specimens, a clear yellowing took place. Both the pigment system and the surface texture affected the color development during the ageing test. The latter can be of significant importance in certain applications when components with different surface textures are placed adjacent to each other. The surface micro‐hardness increased with increasing ageing time and its change followed that of the discoloration. Chemical changes of the surface layers were characterized by FTIR and were in accordance with results reported in the literature; i.e., an increase of the bands associated with carbonyl groups with increasing ageing time and a decrease of the bands associated with the polybutadiene phase clearly indicated chemical degradation due to ageing treatments. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Sensitization of zinc oxide photoanode with an indoline dye
Authors: Onwona‐Agyeman Boateng , Nakao Motoi , Kumara Gamaralalege Rajanya Asoka , Karunarathne Sedari Mudiyanselage Migara Lakshitha , Anuradha Sepalage Gaveshana , Dematage Nilupulee
Published: December 2012

A dye‐sensitized solar cell (DSC) made of nanoporous ZnO film on aluminum‐doped zinc oxide (ZnO/AZO) transparent substrate has higher solar‐to‐electric energy conversion efficiency than a DSC consisting of nanoporous ZnO film deposited on conventional fluorine‐doped tin oxide (ZnO/FTO) transparent substrate. The ZnO/AZO DSC gave an overall conversion efficiency of 7.2% whereas the ZnO/FTO yielded a conversion efficiency of 4.5%. The film‐substrate orientation and higher light harvesting of the nanoporous ZnO film on the AZO after heating in air are mainly attributed to the higher energy conversion efficiency of the ZnO/AZO DSC. Copyright © 2012 John Wiley & Sons, Ltd.
IDENTIFYING STUDENTS WITH EMOTIONAL DISTURBANCE: SCHOOL PSYCHOLOGISTS’ PRACTICES AND PERCEPTIONS
Authors: Hanchon Timothy A. , Allen Ryan A.
Published: December 2012

From its inception as a disability category in the Education for All Handicapped Children Act, serving students under the special education category Emotional Disturbance (ED) has been a challenging task for school psychologists. In particular, the vague and ambiguous federal definition has created an environment in which inconsistent assessment practices and decision making are almost inevitable. In this study, we examined school psychologists’ (N = 214) assessment practices when determining initial eligibility for ED, as well as their perceptions regarding the language contained within the federal ED definition. Findings indicated that although school psychologists recognize the need for a multimethod, multisource assessment model when ED is a classification consideration, in many instances, their actual assessments are missing commonly recommended sources of data for making eligibility decisions, including classroom observations; parent, teacher, and student interviews; and behavior rating scales. The results from the study provide a useful overview of school psychologists’ assessment practices and are couched within the questions and confusion that have surrounded the federal ED definition since its codification into law.
Photostimulated detection of defect formation in BaF2 under irradiation of synchrotron radiation
Authors: Watanabe Masayuki , Azuma Junpei , Asaka Shuji , Tsujibayashi Toru , Arimoto Osamu , Nakanishi Shunsuke , Itoh Hiroshi , Kamada Masao
Published: December 2012

We have investigated the defect formation processes of BaF2 single crystals under vacuum ultraviolet radiation with the use of combination spectroscopy of synchrotron radiation (SR) and laser. The defect formation efficiency was measured as a function of excitation photon energy of SR by means of a laser‐induced luminescence method. It was found that the efficiency depends significantly on the excitation photon energy. We show that the dependence can be explained in terms of the diffusive motion of hot conduction electrons generated by the photoexcitation. The relationship between the defect formation and the energy relaxation of core excitons is also discussed.
Effect of external pressure on Tc of as‐grown and thermally treated superconducting Rbx Fe2–ySe2 single crystals
Authors: Kanagaraj M. , Krzton‐Maziopa A. , Kalai Selvan G. , Pomjakushina E. , Conder K. , Weyeneth S. , Puzniak R. , Arumugam S.
Published: December 2012

We report on the effect of external pressure on the superconducting transition temperature (Tc) of as‐grown and thermally treated single crystals of superconducting iron chalcogenide Rb0.85Fe1.9Se2. The superconducting transition temperature of 27.1 K at ambient pressure for the as‐grown sample was found to increase up to 33.2 K for the sample annealed for 3 h at 215 °C in vacuum. An increase of Tc up to 28.2 K was observed for the as‐grown sample at a pressure of 0.83 GPa. For all the studied crystals, annealed in the temperature range between 215 °C and 290 °C, the external pressure seems to decrease the superconducting transition temperature and a negative pressure coefficient of Tc was observed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Gate‐controlled metal–insulator transition in the LaAlO3/SrTiO3 system with sub‐critical LaAlO3 thickness
Authors: Lee Joon Sung , Seung Sang Keun , Lee Seung Ran , Chang Jung‐Won , Noh Hyunho , Baasandorj Lkhagvasuren , Shin Hyun Sup , Shim Seung‐Bo , Song Jonghyun , Kim Jinhee
Published: December 2012

We studied the electrical conduction in the LaAlO3/SrTiO3 (LAO/STO) interface electron system with a sub‐critical LAO layer thickness of ∼3.5 unit cells (uc). It was found that the true dividing point between metallic and insulating behaviour without gating lies near the LAO thickness of 3.5 uc. Our marginally metallic 3.5 uc sample showed a sharp transition to insulating state at temperatures which strongly depended on the applied negative back‐gate voltage. The superior gate‐controllability of the sample was attributed to its sheet carrier density which was an order of magnitude lower than those of conducting LAO/STO samples with 4 uc or more of LAO layers. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Measurement of δ18O values in arsenic and selenium oxyanions
Authors: Larese‐Casanova Philip , Blake Ruth E.
Published: December 2012

RATIONALE

Past stable isotopic studies of selenium and arsenic oxyanions within a biogeochemistry context have focused solely on selenium isotopes due to monoisotopic nature of arsenic and lack of attention to oxygen. A modern quantification method of δ18O values in selenate, selenite, arsenate, and arsenite is presented here, similar to methods for other inorganic oxyanions such as phosphate.

METHODS

Dissolved oxyanions were recovered after precipitation with silver or barium cations within controlled pH ranges and purified by drying and roasting under vacuum. Oxygen isotope ratio measurements were performed on 250–450 micrograms of solids using continuous flow high‐temperature conversion elemental analyzer/isotope ratio mass spectrometry (CF‐TCEA/IRMS). Each Se and As solid was evaluated for reproducibility and stability of δ18O values and the usefulness of this method for evaluating aqueous phase Se and As oxyanion reactions was addressed.

RESULTS

Only silver arsenate and barium selenate were shown to have stable, reproducible δ18O values over 5 months and were calibrated to the VSMOW scale. The method was applied to confirm complete exchange of oxygen isotopes between arsenate and solvent water at pH 7 which produced an O‐isotope fractionation between arsenate and water of 6.0‰. Furthermore, the method revealed the ability of oxygen in selenate to kinetically fractionate during reduction to elemental selenium by a green rust compound which produced a fractionation (20.9‰) larger than reported δ80/76Se values for similar reactions.

CONCLUSIONS

The experimental and analytical conditions for δ18O analysis of Se and As oxyanions were detailed. δ18O analyses of As and Se oxyanions may be useful in biogeochemical studies for tracing chemical reaction pathways, determining environmental sources of Se, or diagnosing specific reaction mechanisms for As and Se oxyanions. Copyright © 2012 John Wiley & Sons, Ltd.
Discrimination of cyclic and linear oligosaccharides by tandem mass spectrometry using collision‐induced dissociation (CID), pulsed‐Q‐dissociation (PQD) and the higher‐energy C‐trap dissociation modes
Authors: Przybylski Cédric , Bonnet Véronique
Published: December 2012

RATIONALE

Carbohydrates have essential functions in living organisms and cells, but, due to the presence of numerous linkage combinations, substituent sites and possible conformations, they are the class of biomolecules which exhibits the huge structural diversity found in nature. Thereby, due to such diversity and poor ionization, their structural deciphering by mass spectrometry is still a very challenging task.

METHODS

Here, we studied a series of linear and cyclic neutral oligosaccharides using electrospray with collision‐induced dissociation (CID), pulsed‐Q‐dissociation (PQD) and the higher‐energy C‐trap dissociation (HCD) feature of a linear ion trap Orbitrap hybrid mass spectrometer (LTQ‐Orbitrap). The collision energy necessary to obtain 50% fragmentation (CE50 values) in CID, PQD and HCD was used to correlate both size and structures.

RESULTS

The default settings for activation time and/or activation Q are the most appropriate, except for HCD, where 100 ms instead of 30 ms gave more intense fragment ions. PQD exhibits a 2–8‐fold lower sensitivity than CID. HCD provides signals closer or slightly superior by 1.5‐fold than PQD, and offers a more balanced ion distribution through the spectrum. Furthermore, HCD offers the possibility to make fine adjustments of the energy via the eV scale to further increase the yield of low‐mass fragments.

CONCLUSIONS

The complementarity of CID, PQD and HCD was clearly demonstrated by obtaining structural information on hexa‐, hepta‐ and octasaccharides. Together, these results clearly indicate the usefulness of the CID/HCD pair for further structural deciphering, and analysis of more complex structures such as multi‐antennary carbohydrates or glycoconjuguates alone or in mixture. Copyright © 2012 John Wiley & Sons, Ltd.
Study on noncovalent complexes of alkaloids with DNA duplex using electrospray ionization mass spectrometry
Authors: Ma Lei , Song Fengrui , Liu Zhiqiang , Liu Shuying
Published: December 2012

RATIONALE

DNA is an important molecular target in modern medicine research. Some DNA‐binding ligands have been used to treat numerous diseases. Therefore, understanding the interactions of different ligands with DNA and looking for new DNA agents are necessary to develop new drugs.

METHODS

Electrospray ionization mass spectrometry (ESI‐MS) in the negative ion mode was used to screen the noncovalent complexes between 11 alkaloids with double helix oligonucleotides at molar ratios 1:1 to 1:4. The relative binding affinities based on the fraction of bound DNA and sequence selectivities of alkaloids towards the duplex were also investigated by ESI‐MS. Moreover, tandem mass spectrometry of 5‐charged complex ions was used to try to determine DNA‐binding modes.

RESULTS

Six alkaloids showed complexation with the selected DNA duplex, i.e., berberine, coptisine, peimine, aconitine, oxysophoridine and cytisine. They showed their binding affinities with d(AACTCCCGGCACAC/GTGTGCCGGGAGTT) in the order of berberine > coptisine > peimine > aconitine, oxysophoridine > cytosine; additional experiments involving collision energy proved this result. Sequence selectivities were not apparent for coptisine, peimine, aconitine and oxysophoridine with four DNA duplexes. The complexes containing berberine and coptisine underwent the predominant loss of the G base. However, for complexes containing the other four alkaloids, they dissociated via the loss of neutral drug. The results confirmed that they may have different binding modes.

CONCLUSIONS

According to experiment data and structural information, the binding mode of individual drugs with DNA was speculated. It was noted that the bindings of alkaloids peimine, aconitine and oxysophoridine with DNA are discovered firstly. This may give a clue to design duplex‐binding ligands and be helpful for understanding biological activities of these alkaloids. Copyright © 2012 John Wiley & Sons, Ltd.
Development of high‐pressure probe electrospray ionization for aqueous solution
Authors: Rahman Md. Matiur , Chen Lee Chuin , Hiraoka Kenzo
Published: December 2012

RATIONALE

Probe electrospray ionization (PESI) is a recently developed method that uses a sharp solid needle as electrospray emitter and the sample is loaded to the needle tip by repetitive movement of the needle probe. This method has been previously used for the analysis of sample with high salt concentration and real‐world samples without sample pretreatment. Although PESI is also applicable to aqueous solution, the ion signal stability and reproducibility were not satisfactory due to the spontaneous occurrence of corona discharge taking place on the metallic needle tip.

METHODS

In the previous version of PESI, the ionization was performed under an open environment, thus ambient condition such as humidity and the presence of environmental contaminant also affected the performance of PESI. In this paper, we report a modified version of PESI in which the electrospray and the desolvation of charged droplets are performed inside an enclosed chamber which is pressurized to >1 atm with dry air.

RESULTS

Under a super atmospheric condition, the dielectric strength of the ambient gas was enhanced and stable electrospray could to be initiated without the occurrence of corona discharge even for liquid sample with high surface tension such as pure water. A comparative study of atmospheric‐pressure PESI and high‐pressure PESI (HP‐PESI) had been performed to demonstrate the improvement of PESI in sensitivity and signal stability for the detection analytes in aqueous solution.

CONCLUSIONS

HP‐PESI offers a higher sensitivity and signal stability over PESI due to the absence of gaseous breakdown, better desolvation, and higher ion sampling rate by the mass spectrometer. Copyright © 2012 John Wiley & Sons, Ltd.
Identification of low molecular weight organic acids by ion chromatography/hybrid quadrupole time‐of‐flight mass spectrometry during Uniblu‐A ozonation
Authors: Amorisco Apollonia , Locaputo Vito , Pastore Carlo , Mascolo Giuseppe
Published: December 2012

RATIONALE

The balance of organic nitrogen and sulfur during ozonation of organic pollutants often shows a lack of complete mineralization. It follows that polar and ionic by‐products are likely to be present that are difficult to identify by liquid chromatography/mass spectrometry (LC/MS).

METHODS

The structural elucidation of low molecular weight organic acids arising from Uniblu‐OH ozonation has been investigated by ion chromatography/electrospray tandem mass spectrometry (IC/ESI‐MS/MS) employing a quadrupole time‐of‐flight mass spectrometer. Unequivocal elemental composition of the by‐products was determined by a combination of mass accuracy and high spectral accuracy.

RESULTS

The employed identification strategy was demonstrated to be a powerful method of unequivocally assigning a single chemical composition to each identified compound. The exact mass measurements of [M–H]– ions allowed the elemental formulae and related structures of eighteen by‐products to be determined confidently. The main degradation pathways were found to be decarboxylation and oxidation. The experimental procedure allowed the identification of both nitrogen‐ and sulfur‐containing organic acid by‐products arising from Uniblu‐OH ozonation.

CONCLUSIONS

The obtained results are of environmental relevance for the balance of organic nitrogen and sulfur during the ozonation of organic pollutants due to the lack of complete mineralization of the compounds containing these atoms. Copyright © 2012 John Wiley & Sons, Ltd.
Exploration of CP12 conformational changes and of quaternary structural properties using electrospray ionization traveling wave ion mobility mass spectrometry
Authors: Kaaki Wassim , Woudstra Mireille , Gontero Brigitte , Halgand Frédéric
Published: December 2012

RATIONALE

CP12 is a small chloroplast protein involved in the Benson‐Calvin cycle. Since it was demonstrated that the CP12 protein shared different conformational properties between reduced and oxidized states we took advantage of the segregational properties of the Traveling Wave Ion Mobility (TWIM) guide to study subtle conformational changes related to redox changes.

METHODS

Electrospray ionization mass (ESI‐MS) spectra of the CP12 protein were recorded in the positive ion mode using an ESI source fitted on a quadrupole time‐of‐flight (QToF) hybrid mass spectrometer equipped with a TWIM cell (Synapt HDMS G1, Waters Corp., Manchester) under non‐denaturing conditions. Non‐covalent experiments were performed using the same instrument without the use of the TWIM device.

RESULTS

Whatever the CP12 form studied, our results showed that CP12 protein was represented by two conformers in equilibrium that displayed very slight differences. These observations led us to propose that CP12 protein structure is rather undergoing transient subtle structural changes than having two different conformational populations in solution. In addition, using non‐denaturing experiments, NAD and CP12 stoichiometry were determined with respect to the GAPDH tetramer and the redox state of CP12.

CONCLUSIONS

In this study we showed that the use of the segregational property of the ion mobility (TWIM, Synapt G1 HDMS, Waters, Manchester, UK) allowed differentiation of subtle conformational changes between redox states of the CP12 protein. Standard non‐denaturing experiments revealed different binding stoichiometry according to the redox state of the CP12 protein. Copyright © 2012 John Wiley & Sons, Ltd.
Laser desorption/ionization mediated by bionanostructures from microalgae
Authors: Jaschinski Tino , Svatoš Aleš , Pohnert Georg
Published: December 2012

RATIONALE

Organic matrices are the state‐of‐the‐art ionization mediators in Laser Desorption/Ionization Mass Spectrometry (LDI‐MS). Despite improvements in understanding matrix chemistry, interfering matrix‐related signals complicate the analysis. Surface‐assisted LDI techniques like desorption/ionization on silicon (DIOS) or nanostructure initiator mass spectrometry (NIMS) provide promising alternatives but rely often on elaborate materials.

METHODS

We introduce nanopatterned biomineralized cell walls of microalgae as easily accessible biological surfaces that support the ionization of embedded molecules in LDI‐MS. Microalgae cell walls were cleaned through oxidation and washing before pipetting on a stainless‐steel matrix‐assisted laser desorption/ionization (MALDI) target. Added molecules were efficiently ionized in positive and negative ionization mode in common MALDI sources. The method was rigorously validated by comparison with established MALDI experiments.

RESULTS

Ionization of PEG600, D‐sphingosine and raffinose was successfully mediated by nanostructured cell wall preparations from two different microalgae. Without any change in protocol, steric acid could be detected in the negative ionization mode. Ionization is also supported by commercially available celite, a material containing mineralized diatom cell walls. Characteristic ingredients of fresh coffee were detected in LDI‐MS after pipetting it on celite without further sample preparation. Caffeine and saccharose were detected in positive and characteristic fatty acids in negative ionization mode. Detection limits were comparable to established MALDI experiments.

CONCLUSIONS

Bionanostructure‐enhanced ionization allows the analysis of a diverse selection of analytes including polymers, sugars, amino alcohols, and organic acids without interfering matrix signals. We also show that celite, a commercially available porous material containing mineralized algal bionanostructures, supports LDI‐MS. Copyright © 2012 John Wiley & Sons, Ltd.
Laser desorption/ionization mass spectrometric analysis of surfactants on functionalized carbon nanotubes
Authors: Cegłowski Michał , Schroeder Grzegorz
Published: December 2012

RATIONALE

Recently, unmodified and carboxylated carbon nanotubes have been used as assisting surfaces laser desorption/ionization (LDI) in mass spectrometry. The functionalization of carbon nanotubes with organic compounds should lead to a gamut of other promising LDI‐assisting surfaces.

METHODS

Carboxylated carbon nanotubes were functionalized with sinapinic acid either covalently or by creating an ionic macro‐complex. Polyether‐based surfactants were used as analytes to examine the properties of these new matrices. Mass spectrometric analysis was conducted on a LDI‐quadrupole time‐of‐flight (QTOF) mass spectrometer. Carbon nanotube surfaces were deposited from suspension using the dried‐droplet method.

RESULTS

The functionalization of the carbon nanotubes was confirmed with Fourier transform infrared (FTIR) spectroscopy. The usefulness of each material was examined with two poly(ethylene glycol) hexadecyl ether amphiphiles (Brij® 52 and Brij® 56) and a poly(ethylene glycol) monomethyl ether as analytes. Generally, the mass spectra obtained with carbon nanotubes covalently functionalized with sinapinic acid as a matrix had peaks with higher intensities than those obtained with carbon nanotubes functionalized by ionic macro‐complex formation.

CONCLUSIONS

The presented new materials based on functionalized carbon nanotubes are effective in the LDI mass analysis of polyether amphiphiles and poly(ethylene glycol) monomethyl ether. This type of assisting surfaces can be highly modified by appropriate functionalization procedures. Copyright © 2012 John Wiley & Sons, Ltd.
Matrix effect in matrix‐assisted laser desorption/ionization mass spectra of derivatized oligomeric polyols
Authors: Borisov Roman S. , Polovkov Nikolai Yu. , Zhilyaev Dmitry I. , Zaikin Vladimir G.
Published: December 2012

RATIONALE

Herein we describe a strong matrix effect observed in the matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐ToF) mass spectra of silylated glycerol alkoxylates and manifested in the loss of the silyl groups in the presence of carboxyl‐containing matrices.

METHODS

Commercially available glycerol alkoxylates containing three end OH groups as well as three matrices – 2,5‐dihydroxybenzoic acid (DHB), 3‐indoleacrylic acid (IAA) and 1,8,9‐anthracenetriol (dithranol) – were chosen for the investigation. N,O‐Bis(trimethylsilyl)trifluoroacetamide containing 1% trimethylchlorosilane, acetic anhydride and a formylation mixture (formic acid/acetyl chloride) were used for derivatization. Initial oligomers and derivatized products were analyzed by MALDI‐ToF‐mass spectrometry (MS) on an Autoflex II instrument, equipped with a nitrogen laser (λ 337 nm), in positive ion reflectron mode.

RESULTS

Only [M + Na]+ ions were observed for underivatized polymers and for completely derivatized polymers in the presence of DHB and dithranol, respectively. In the case of IAA the mass spectra revealed sets of peaks for underivatized, and for partially and completely derivatized oligomers. No similar 'matrix effect' was observed in the case of acylated glycerol alkoxylates (acyl = formyl, acetyl): only peaks for completely derivatized oligomers were obtained in all matrices: DHB, IAA and dithranol. Using 1,9‐nonandiol, we showed that the 'matrix effect' was due to trans‐silylation of carboxyl‐containing matrices (DHB and IAA) during co‐crystallization of silylated oligomers and matrices.

CONCLUSIONS

The obtained results show that matrix molecules can participate as reactive species in MALDI‐ToF‐MS experiments. The matrix should be carefully chosen when a derivatization approach is applied because the analysis of spectra of the completely derivatized products is particularly desirable in the quantitative determination of functional end‐groups. Copyright © 2012 John Wiley & Sons, Ltd.
Characterization of Sky‐region Morphological‐temporal Airborne Collision Detection
Authors: Lai John , Ford Jason J. , Mejias Luis , O'Shea Peter
Published: December 2012

Automated airborne collision‐detection systems are a key enabling technology for facilitating the integration of unmanned aerial vehicles (UAVs) into the national airspace. These safety‐critical systems must be sensitive enough to provide timely warnings of genuine airborne collision threats, but not so sensitive as to cause excessive false alarms. Hence, an accurate characterization of detection and false‐alarm sensitivity is essential for understanding performance tradeoffs, and system designers can exploit this characterization to help achieve a desired balance in system performance. In this paper, we experimentally evaluate a sky‐region, image‐based, aircraft collision‐detection system that is based on morphological and temporal processing techniques. (Note that the examined detection approaches are not suitable for the detection of potential collision threats against a ground clutter background.) A novel collection methodology for collecting realistic airborne collision‐course target footage in both head‐on and tail‐chase engagement geometries is described. Under (hazy) blue sky conditions, our proposed system achieved detection ranges greater than 1540 m in three flight test cases with no false‐alarm events in 14.14 h of nontarget data (under cloudy conditions, the system achieved detection ranges greater than 1170 m in four flight test cases with no false‐alarm events in 6.63 h of nontarget data). Importantly, this paper is the first documented presentation of detection range versus false‐alarm curves generated from airborne target and nontarget image data. © 2012 Wiley Periodicals, Inc.
Surface modification of carbon fiber via electron‐beam irradiation grafting
Authors: Zhenjuan Zang , Yuansheng Wang , Qinyi Deng , Siliang Wang , Te He
Published: December 2012

In this paper, the surface properties of polyacrylonitrile‐based carbon fibers is improved by electron‐beam (EB) irradiation in maleic anhydride/acetone solution at 100, 150, 200 and 150 KGy. Experimental study of this paper is carried out to identify surface topography, surface chemical composition and functional groups, adsorption ability and interface properties of CF/epoxy composites. The results reveal that the roughness of carbon fiber surface is increased obviously after modification by EB irradiation grafting technology. The ratio value of O/C and the relative content of oxygen functional groups on fiber surface are improved effectively, comparing with the unmodified carbon fiber. Besides, adsorption of carbon fiber on epoxy and the mechanical performance of CF/epoxy composites are clearly enhanced after irradiation grafting modification. Copyright © 2012 John Wiley & Sons, Ltd.