Changes In Peak Width Research Articles

Assessing the occurrence of barley starch annealing under heat, moisture and time conditions relevant for kilning: An experimental design approach

In this work, the possible occurrence of barley starch annealing under kilning conditions was investigated. Using an I-optimal response surface methodology, the impact of temperature (45–55 °C), moisture content (30–50%) and time (1–5h) on the gelatinisation behaviour of starch in green malt was studied. An increase in onset (0.5–4.3 °C) and peak temperature (0.5–2.7 °C) and a change in peak width (+0.5 to - 3.2 °C) of the starch gelatinisation endotherm showed the extent of annealing that occurred within an industrially relevant design space. Temperature was the main driver behind the observed changes, but also interaction effects between temperature, moisture content and time contributed. Combined with increasingly high starch gelatinisation temperatures in barley, the observed increases in peak gelatinisation temperature due to annealing could hamper fermentable sugar production during brewing.

Changes in the Electrically Evoked Compound Action Potential over time After Implantation and Subsequent Deafening in Guinea Pigs

The electrically evoked compound action potential (eCAP) is a direct measure of the responsiveness of the auditory nerve to electrical stimulation from a cochlear implant (CI). CIs offer a unique opportunity to study the auditory nerve’s electrophysiological behavior in individual human subjects over time. In order to understand exactly how the eCAP relates to the condition of the auditory nerve, it is crucial to compare changes in the eCAP over time in a controlled model of deafness-induced auditory nerve degeneration. In the present study, 10 normal-hearing young adult guinea pigs were implanted and deafened 4 weeks later, so that the effect of deafening could be monitored within-subject over time. Following implantation, but before deafening, most examined eCAP characteristics significantly changed, suggesting increasing excitation efficacy (e.g., higher maximum amplitude, lower threshold, shorter latency). Conversely, inter-phase gap (IPG) effects on these measures – within-subject difference measures that have been shown to correlate well with auditory nerve survival – did not vary for most eCAP characteristics. After deafening, we observed an initial increase in excitability (steeper slope of the eCAP amplitude growth function (AGF), lower threshold, shorter latency and peak width) which typically returned to normal-hearing levels within a week, after which a slower process, probably reflecting spiral ganglion cell loss, took place over the remaining 6 weeks (e.g., decrease in maximum amplitude, AGF slope, peak area, and IPG effect for AGF slope; increase in IPG effect for latency). Our results suggest that gradual changes in peak width and latency reflect the rate of neural degeneration, while peak area, maximum amplitude, and AGF slope reflect neural population size, which may be valuable for clinical diagnostics.

Metabolomic profiling in small vessel disease identifies multiple associations with disease severity.

Cerebral small vessel disease is a major cause of vascular cognitive impairment and dementia. There are few treatments, largely reflecting limited understanding of the underlying pathophysiology. Metabolomics can be used to identify novel risk factors to better understand pathogenesis and to predict disease progression and severity.We analysed data from 624 patients with symptomatic cerebral small vessel disease from two prospective cohort studies. Serum samples were collected at baseline and patients underwent MRI scans and cognitive testing at regular intervals with up to 14 years of follow-up. Using ultra-performance liquid chromatography–mass spectrometry and nuclear magnetic resonance spectroscopy, we obtained metabolic and lipidomic profiles from 369 annotated metabolites and 54 764 unannotated features and examined their association with respect to disease severity, assessed using MRI small vessel disease markers, cognition and future risk of all-cause dementia.Our analysis identified 28 metabolites that were significantly associated with small vessel disease imaging markers and cognition. Decreased levels of multiple glycerophospholipids and sphingolipids were associated with increased small vessel disease load as evidenced by higher white matter hyperintensity volume, lower mean diffusivity normalized peak height, greater brain atrophy and impaired cognition. Higher levels of creatine, FA(18:2(OH)) and SM(d18:2/24:1) were associated with increased lacune count, higher white matter hyperintensity volume and impaired cognition. Lower baseline levels of carnitines and creatinine were associated with higher annualized change in peak width of skeletonized mean diffusivity, and 25 metabolites, including lipoprotein subclasses, amino acids and xenobiotics, were associated with future dementia incidence.Our results show multiple distinct metabolic signatures that are associated with imaging markers of small vessel disease, cognition and conversion to dementia. Further research should assess causality and the use of metabolomic screening to improve the ability to predict future disease severity and dementia risk in small vessel disease. The metabolomic profiles may also provide novel insights into disease pathogenesis and help identify novel treatment approaches.

Dose-dependent effects of high intensity focused ultrasound on compound action potentials in an ex vivo rodent peripheral nerve model: comparison to local anesthetics

BackgroundIn animal models, focused ultrasound can reversibly or permanently inhibit nerve conduction, suggesting a potential role in managing pain. We hypothesized focused ultrasound’s effects on action potential parameters may be...

Atomic structure and electronic properties of planar defects in SrFeO3−δ thin films

Extended planar defects found in epitaxially grown $\mathrm{SrFe}{\mathrm{O}}_{3\text{\ensuremath{-}}\ensuremath{\delta}}$ thin films are expected to exhibit distinct conductivity properties. Here, we use a combination of scanning transmission electron microscopy techniques and electron energy-loss spectroscopy (EELS) to uncover the peculiar structure of these planar defects and to explore their electronic properties. We find that the defects are formed by $\mathrm{F}{\mathrm{e}}_{2}{\mathrm{O}}_{2+\ensuremath{\alpha}}$ layers consisting of $\mathrm{Fe}{\mathrm{O}}_{5}$ polyhedra alternating with SrO and $\mathrm{Fe}{\mathrm{O}}_{2}$ perovskite-type layers, analogous to the $\mathrm{S}{\mathrm{r}}_{4}\mathrm{F}{\mathrm{e}}_{6}{\mathrm{O}}_{12+\ensuremath{\delta}}$ crystal structure. Our experimental and theoretical EELS data, combined with projected density of states calculations, reveal peak width changes and energies shifts, which suggest an increased electron doping of the Fe $3d{e}_{g}$ band in the $\mathrm{F}{\mathrm{e}}_{2}{\mathrm{O}}_{2+\ensuremath{\alpha}}$ layers as compared to the $\mathrm{SrFe}{\mathrm{O}}_{3\ensuremath{-}\ensuremath{\delta}}$ film. Thus we show that the presence of $\mathrm{F}{\mathrm{e}}_{2}{\mathrm{O}}_{2+\ensuremath{\alpha}}$ planar defects indeed can effectively modify the electron-hole conductivity in $\mathrm{SrFe}{\mathrm{O}}_{3\text{\ensuremath{-}}\ensuremath{\delta}}$ films.

High pressure study of magnetocaloric effect in Ho3Co and Tb3Co

The magnetocaloric effect of intermetallic compounds of Tb3Co and Ho3Co is studied under high pressures up to ∼1 GPa using pressure dependent dc magnetisation and specific heat measurements at ambient conditions. The magnetic entropy change (−ΔSM) obtained from magnetisation data and adiabatic change in temperature (ΔTad) determined from zero-field specific heat and magnetisation data are found to be nearly identical within error limits with those deduced from purely field dependent specific heat experiments. With increasing hydrostatic pressure to ∼1 GPa, the −ΔSM and ΔTad, both show a significant enhancement of about 37% and 13%, respectively for 9 T field change in case of Tb3Co. On the other hand, Ho3Co exhibits a decrease of about 8% in both −ΔSM and ΔTad with increasing pressure. The refrigerant capacity (RC) also increases from 650 J kg−1 to 847 J kg−1 in the case of Tb3Co and it goes down from 665 J kg−1 to 615 J kg−1 for Ho3Co for an increase of pressure to 1 GPa. With increasing pressure, the peak widths of both −ΔSM and ΔTad increase in case of Tb3Co, although the increase is more in −ΔSM. However, such noticeable changes in peak widths with pressure were not observed in Ho3Co. At ambient pressure, peak of −ΔSM () scales with for both the compounds, consistent with the prediction of mean field theory (MFT) for second order magnetic transition. However, deviation from MFT was noticed at high pressures as was found to scale with instead of for both the alloys. Further, normalised −ΔSM curves for different ΔH and pressures collapse on a single universal curve in both the compounds thereby indicating that the second order magnetic transition persists even up to ∼1 GPa pressure.

The degree of polymerization and structural disorder in (Mg,Fe)SiO3 glasses and melts: Insights from high-resolution 29Si and 17O solid-state NMR

Probing the degree of polymerization and structural disorder of (Mg,Fe)SiO3 glasses and melts remains a challenging problem, despite their strong implications for the properties of natural volcanic glasses and dense melts in Earth’s surface and interior. Here, we explore the iron-induced changes in silicon and the oxygen configurations of (Mg1−XFeX)SiO3 glasses (Fe3+/ƩFe = 0.22 ± 0.07) with varying XFe [=Fe/(Mg + Fe), containing up to 13.5 wt% FeO] using high-resolution 29Si and 17O MAS, and 2D 17O 3QMAS NMR, unveiling the effect of Fe2+ on the extent of disorder in these glasses. The 29Si MAS NMR spectra show the apparent peak broadening in less polymerized species (i.e., Q1) and an increase in the fraction of highly polymerized (i.e., Q3) species with increasing XFe. These changes imply the selective decrease in NMR signal intensity of Q1 and Q2 due to their spatial proximity to Fe2+ (i.e., paramagnetic effect), and slight increase in the degree of polymerization due to the presence of minor fraction of Fe3+. The 2D 17O NMR spectra revealed that the fraction of Si-O-Si apparently increases with XFe and more significant changes in peak width for Mg-O-Si are observed with varying XFe. The results indicate that Mg-O-Si is more strongly affected by Fe2+ than Si-O-Si, suggesting a moderate degree of preferential proximity between Fe2+ and non-bridging oxygen. The results allow us to conceptualize the scheme to account for paramagnetic interaction between the nuclear spins and Fe2+. The scheme provides a systematic protocol to interpret the NMR spectra of diverse iron-bearing silicate glasses. The current NMR results, in conjunction with the results in the previous study for Fe3+-dominant sodium silicate glasses, suggest that paramagnetic effect depends on the valence state of Fe, indicating the presence of a moderate degree of preferential interaction between Fe2+ and NBO and less polymerized Si units as well as that between Fe3+ and highly polymerized Si units and BO. Though qualitative, the current NMR results for (Mg,Fe)SiO3 glasses shed light on an opportunity to explore the detailed structures of iron-bearing natural volcanic glasses and can improve understanding of the transport properties of the basaltic melts.

Eu Activation in β-Ga2O3 MOVPE Thin Films by Ion Implantation

In this work, we have established the effects of Eu implantation and annealing on β-Ga2O3 thin films grown by metal organic vapor phase epitaxy (MOVPE) on sapphire substrate. The study is based on the combined information from structural and optical techniques: X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), cathodoluminescence (CL), photoluminescence (PL), and photoluminescence excitation (PLE). The thin films were implanted with a fluence of 1 × 1015 Eu·cm−2 and annealed at 900°C. Neither significant changes in peak width or position nor additional peaks related to Eu complexes were detected in the XRD 2θ-ω scans. RBS results and SRIM simulation are in good agreement, revealing that no Eu diffusion to the surface occurs during annealing. For the used implantation/annealing conditions, the Eu ion penetration depth reached ∼130 nm, with a maximum concentration at ∼50 nm. Furthermore, CL and PL/PLE results evidenced the optical activation of the Eu3+ in the β-Ga2O3 host. The detailed study of the Eu3+ intra-4f shell transitions revealed that at least one active site is created by the Eu implantation/annealing in β-Ga2O3 thin films grown on sapphire. Independently of the β-Ga2O3 film thickness, well controlled optical activation of implanted Eu was achieved.

Profiling the N-Glycan Composition of IgG with Lectins and Capillary Nanogel Electrophoresis.

Glycosylated human IgG contains fucosylated biantennary N-glycans with different modifications including N-acetylglucosamine, which bisects the mannose core. Although only a limited number of IgG N-glycan structures are possible, human IgG N-glycans are predominantly biantennary and fucosylated and contain varying levels of α2–6-linked sialic acid, galactose, and bisected N-acetylglucosamine. Monitoring the relative abundance of bisecting N-acetylglucosamine is relevant to physiological processes. A rapid, inexpensive, and automated method is used to successfully profile N-linked IgG glycans and is suitable to distinguish differences in bisection, galactosylation, and sialylation in N-glycans derived from different sources of human IgG. The separation is facilitated with self-assembled nanogels that also contain a single stationary zone of lectin. When the lectin specificity matches the N-glycan, the peak disappears from the electropherogram, identifying the N-glycan structure. The nanogel electrophoresis generates separation efficiencies of 500 000 plates and resolves the positional isomers of monogalactosylated biantennary N-glycan and the monogalactosylated bisected N-glycan. Aleuria aurantia lectin, Erythrina cristagalli lectin (ECL), Sambucus nigra lectin, and Phaseolus vulgaris Erythroagglutinin (PHA-E) are used to identify fucose, galactose, α2–6-linked sialic acid, and bisected N-acetylglucosamine, respectively. Although PHA-E lectin has a strong binding affinity for bisected N-glycans that also contain a terminal galactose on the α1–6-linked mannose branch, this lectin has lower affinity for N-glycans containing terminal galactose and for agalactosylated bisected biantennary N-glycans. The lower affinity to these motifs is observed in the electropherograms as a change in peak width, which when used in conjunction with the results from the ECL lectin authenticates the composition of the agalactosylated bisected biantennary N-glycan. For runs performed at 17 °C, the precision in migration time and peak area was less than or equal to 0.08 and 4% relative standard deviation, respectively. The method is compatible with electrokinetic and hydrodynamic injections, with detection limits of 70 and 300 pM, respectively.

(Allen J. Bard Award in Electrochemical Science Address) Electroanalytical Techniques Coupled with in-Situ Structural Characterization of Electrodes in Devices for Energy Storage and Conversion

Inspired by the seminal work of A. J. Bard in electroanalytical chemistry during more than half of a century, we are trying to apply novel electroanalytical tools in conjunction with in-situ spectro-electrochemical techniques for the study of the most reactive electrochemical systems, related to energy storage and conversion. A variety of electroanalytical methods are widely used in advanced batteries and super-capacitors research for screening and optimization of electrode materials including their characteristic electrochemical windows, onset potentials of ions insertion and extraction, formation of protective surface-solution interphases etc. These parameters affect the electrodes stability, capacity retention, cycling efficiency and rate capability. Electroanalytical methods have their own intrinsic accessible time windows and different amplitude of electric perturbation (potential or current). Among these methods electrochemical impedance spectroscopy (EIS) has the widest time window from ca. 10-5 to 103 s and small potential amplitude which enables the probing the kinetics of a large variety of processes accompanying electrochemical insertion of Li , Na and Mg ions into battery electrodes separating them by the characteristic time constants of these processes. In contrast, cyclic voltammetry (CV) effectively probes kinetic steps in the long time window (from 102 to 105 s) close to either quasi-equilibrium intercalation or intercalation process in the form of first-order phase transition. CV is a large-amplitude technique, and attempts to apply it for a shorter time domain, e.g. corresponding to characteristic solid-state diffusion time constants inevitably results in lack of their resolution with respect to electrode potential (or intercalation level). The niche between EIS and CV is effectively bridged by intermittent titration techniques (PITT, GITT) ensuring highly resolved separation between the different sequential phase transitions in the long time domain, and potential-resolved chemical diffusion coefficients of intercalated ions. [1] The area-averaged responses of battery electrodes obtained by electroanalytical techniques depend on the local chemical or porous electrode structure: very often this information is required for correct interpretation of the electrochemical characteristics (e.g. chemical diffusion coefficients).Recent progress in electroanalytical methods adapted for application in LIB , NIB and Mg batteries research relates to development of non-gravimetric EQCM-D (electrochemical quartz-crystal microbalance with dissipation monitoring) techniques , which in contrast to classical EQCM, tracks not only resonant frequency change DF/n (n is overtone order) but also dissipation of the oscillation energy (or equivalently, resonance peak width change, DW/n). Tracking complex frequency change, DF*/n = DF/n + iDW/n, for rigid porous battery electrodes as a function of the penetration depth of transverse oscillation wave in the electrolyte solution, d (dependent on the overtone order and liquid’s density and viscosity) over multiple harmonics ,allows the characterization of the complex electric and mechanical properties of thin electrode coatings in electrolyte solutions (using the most relevant materials for advanced rechargeable batteries and super-capacitors) under applied potential. Intercalation-induced changes of dimensional and porous electrodes’ structure can be quantified in terms of hydrodynamic admittance models by fitting well developed models for momentum transfer to the experimental RQCM-D data retrieving structural parameters in way similar to fitting experimental EIS data (e.g. Nyquist plots) by equivalent electrical circuit analogs. Validation of the extracted parameters for their internal consistency and comparison with the results from complimentary other in-situ techniques (e.g. scanning probe microscopes) is required. The methodology of hydrodynamic spectroscopy of porous solids and composite electrodes that we develop in recent years is inexpensive, noninvasive and highly useful in a broad spectrum of applications including deeper insights into the dynamic build-up and subsequent development of solid-electrolyte interfaces in Li and Na battery electrodes and stresses-volume changes-stability interrelation of ion intercalation electrodes.[3] References [1] M.D. Levi and D. Aurbach, Electrochim. Acta 45 (1999) 167-185. [2] N. Shpigel, M.D. Levi, S. Sigalov, O. Girshevitz, D. Aurbach, L. Daikhin, P. Pikma, M. Marandi, A. Janes, E. Lust, N. Jackel, V. Presser, Nat. Mater. 15 (2016) 570-575.[3] S. Sigalov, N. Shpigel, M. D. Levi, M. Feldberg, L. Daikhin, D. Aurbach, Anal. Chem. 88, (2016) 10151–10157.

The ammonium ion in a silicate under compression: infrared spectroscopy and powder X-ray diffraction of NH4AlSi3O8—buddingtonite to 30 GPa

The behavior of the ammoniated feldspar buddingtonite, NH4AlSi3O8, has been studied using infrared (IR) spectroscopy up to ~30 GPa and using synchrotron powder X-ray diffraction to 10 GPa at room temperature. We examine the bonding of the ammonium ion under pressure and in particular whether hydrogen bonding is enhanced by compaction, as well as probe how the ammonium ion affects the elasticity and behavior of the aluminosilicate framework at pressure. Powder diffraction data yield a bulk modulus of 49 GPa for a pressure derivative of 4, implying that the ammonium ion substitution may induce a modest softening of the feldspar lattice relative to the potassium ion. Under compression, the N–H vibrations are remarkably insensitive to pressure throughout the pressure range of these experiments. However, the vibrations of the aluminosilicate framework of buddingtonite undergo changes in their slope at ~13 GPa, implying that a change in compressional mechanism occurs near this pressure, but the vibrational modes of the ammonium molecule show little response to this change. These results show that (1) there is little, if any, enhancement of hydrogen bonding between the ammonium ion and the oxygen ions of the silica and aluminum tetrahedral framework under pressure, as manifested by the slight (and mostly positive) shifts in the N–H stretching vibrations of the ammonium ion; (2) ordering of the ammonium ion is not observed under compression, as no changes in peak width or in the general appearance of the spectra are observed under compression; and (3) structural changes induced by pressure in the aluminosilicate framework do not produce significant changes in the bonding of the ammonium ion. Hence, it appears that the ammonium ion interacts minimally with its surrounding lattice, even at high pressures: Its behavior is compatible with it being, aside from Coulombic attraction to the oxygen-dominated matrix, a largely non-interactive guest molecule within the silicate framework. This lack of interaction with the surrounding oxide lattice under compression may impact the stability of ammoniated minerals at high pressures and temperatures and ultimately likely favors nitrides or fluid phases as the dominant nitrogen carriers within the deeper mantle.

Raman spectroscopic study of structural transformation in ordered double perovskites La2CoMnO6 bulk and epitaxial film

Abstract Raman spectra of polycrystalline bulk compound and epitaxial thin films of La2CoMnO6 grown on (001) oriented SrTiO3 substrates have been measured between 300 K and 823 K. The polarization dependence of the spectra collected on films provides clear evidence for ordered P21/n structure at room temperature. The high temperature spectra showed appearance of two new modes and simultaneous disappearance of couple of modes above 523 K for bulk and above 583 K in films which is close to previously reported P21/n to R-3 structural transition temperature. The structural transition is seen to accompany softening and anomalous changes in peak widths of stretching and anti-stretching modes indicating significant changes in the tilts in oxygen octahedra around the cations.

Reinterpretation of the expected electronic density of states of semiconductor nanowires.

One-dimensional semiconductor nanowires hold the promise for various optoelectronic applications since they combine the advantages of quantized in-plane energy levels (as in zero-dimensional quantum dots) with a continuous energy spectrum along the growth direction (as in three-dimensional bulk materials). This dual characteristic is reflected in the density of states (DOS), which is thus the key quantity describing the electronic structures of nanowires, central to the analysis of electronic transport and spectroscopy. By comparing the DOS derived from the widely used "standard model", the effective mass approximation (EMA) in single parabolic band mode, with that from direct atomistic pseudopotential theory calculations for GaAs and InAs nanowires, we uncover significant qualitative and quantitative shortcomings of the standard description. In the EMA description the nanowire DOS is rendered as a series of sharply rising peaks having slowly decaying tails, with characteristic peak height and spacing, all being classifiable in the language of atomic orbital momenta 1S, 1P, 1D, etc. Herein we find in the thinner nanowires that the picture changes significantly in that not only does the profile of each DOS peak lose its pronounced asymmetry, with significant changes in peak width, height, and spacing, but also the origin of the high-energy peaks changes fundamentally: below some critical diameter, the region of atomic orbital momentum classified states is occupied by a new set of DOS peaks folded-in from other non-Γ-valleys. We describe explicitly how distinct physical effects beyond the conventional EMA model contribute to these realistic DOS features. These results represent a significant step toward understanding the intriguing electronic structure of nanowires reflecting the coexistence of discrete and continuum states. Experimental examinations of the predicted novel DOS features are called for.

Molecular Structure and Organization of Starch Granules from Developing Wheat Endosperm

ABSTRACTWheat starches isolated from seeds harvested between 7 and 49 days after anthesis (DAA) were fractionated into large (>8 μm) and small (<8 μm) granules and studied for starch structure and architecture. Starch granules at 7 DAA possessed unimodal size distribution, whereas it was bimodal at later maturity stages. The apparent amylose fraction of starch granules at early maturity (7 and 14 DAA) consisted of intermediate‐type materials, whereas starch at later maturity stages (28 and 49 DAA) contained branched amylose. Wide‐angle X‐ray scattering (WAXS) revealed a well‐developed polymorphic structure already at 7 DAA. Although the presence of a small proportion of B‐type crystallites mixed with A‐type crystallites was observed in the X‐ray diffractogram of starches at early maturation (7 and 14 DAA), it was masked by the A‐type crystallites at later maturity stages. However, the large granules had a higher proportion of B‐type crystallites and lower relative crystallinity (RC) than their small‐granule counterpart. The iodine absorption properties of the starch granules demonstrated different levels of mobility of the starch polymers at different stages of maturity and the mobility of more glucan polymers in the large granule population compared with the small granules at the same maturity stage. Iodine did not change the characteristic A‐type crystalline pattern of starch, but it increased RC. Changes in peak width at half height based on WAXS data further suggested the possible interaction of iodine with amylopectin intercluster chain segments and branch chains in formation of inclusion complexes.

Pressure-induced spin transition and evolution of the electronic excitations of FeBO3: Resonant inelastic x-ray scattering results

A high-pressure resonant inelastic x-ray scattering (RIXS) of at the Fe K pre-edge has been carried out to study the evolution of electronic excitations through the pressure-induced spin transition. Systematic peak shifts with insignificant peak width change are observed with increasing pressure in the high-spin state. An electronic transition occurs in tandem with the high-spin to low-spin transition, observed as the emergence of multiple new low-energy peaks in the spectra. The energy gap is reduced due to these low-energy peaks, not a peak width broadening. The observed electronic excitations are associated with dd excitations, which are calculated using a full-multiplet theory. We consider changes in crystal-field splitting and covalency to explain the observed peak shifts in the high-spin state. The new peaks that emerge upon the high-to low-spin transition are compared with dd excitations for the low-spin configuration.

Evaluation of recent very efficient wide-pore stationary phases for the reversed-phase separation of proteins

In the present contribution, columns packed with fully porous widepore 1.7μm particles (Acquity BEH300) and widepore core–shell 3.6μm particles (Aeris WP) were evaluated for the separation of model and therapeutic proteins of varying sizes, hydrophobicity and isoelectric points. Two types of bonding were compared, namely C4 and C18 in a systematic way. The kinetic performance of these stationary phases was evaluated in a previous paper hence this new work focuses on their retention behaviour, loading capacity and selectivity. Using the Tanaka tests, model proteins, and other confirmatory experiments, it is highly probable that with proteins, strong interaction mechanisms were predominant on the Aeris WP while the hydrophobic interaction was the driving force of the retention on the Acquity BEH300 material. This explained why, despite the lower pore volume of the Aeris WP material, the apparent retention factors of proteins possessing both hydrophobic and charged amino acids residues were very close on the four investigated columns. In terms of peak widths, values for proteins were similar for all the tested stationary phases, despite the probable strong ion exchange mechanisms of Aeris WP column. This could be explained by the excellent mass transfer characteristics afforded by the thin porous layer (∼0.2μm) at the surface of the particle which probably compensates for the slow secondary ionic interaction kinetics. The loading capacity was also evaluated on all the four widepore columns, using model proteins. On average, approximately 2–4 times higher amount of proteins can be injected on the fully porous BEH300 compared to the core–shell Aeris WP columns when avoiding 10% change in peak width or in tailing. However, this result could be strongly influenced by the nature and shape of the protein, its hydrophobicity, folding, size and number of charges. Finally, all of these columns were employed for the highly efficient separation of a therapeutic protein (interferon-α-2A) and some closely related proteins and showed excellent performance and selectivity. This result confirms that RPLC gained interest in the biopharmaceutical field as it provides significantly better peak widths than size-exclusion or ion-exchange and inherent compatibility with MS.

Hyperthermically induced changes in high spectral and spatial resolution MR images of tumor tissue—a pilot study

This pilot study investigated the feasibility of using MRI based on BOLD (blood–oxygen-level-dependent) contrast to detect physiological effects of locally induced hyperthermia in a rodent tumor model. Nude mice bearing AT6.1 rodent prostate tumors inoculated in the hind leg were imaged using a 9.4 T scanner using a multi-gradient echo pulse sequence to acquire high spectral and spatial resolution (HiSS) data. Temperature increases of approximately 6 °C were produced in tumor tissue using fiber-optic-guided light from a 250 W halogen lamp. HiSS data were acquired over three slices through the tumor and leg both prior to and during heating. Water spectra were produced from these datasets for each voxel at each time point. Time-dependent changes in water resonance peak width were measured during 15 min of localized tumor heating. The results demonstrated that hyperthermia produced both significant increases and decreases in water resonance peak width. Average decreases in peak width were significantly larger in the tumor rim than in normal muscle (p = 0.04). The effect of hyperthermia in tumor was spatially heterogeneous, i.e. the standard deviation of the change in peak width was significantly larger in the tumor rim than in normal muscle (p = 0.005). Therefore, mild hyperthermia produces spatially heterogeneous changes in water peak width in both tumor and muscle. This may reflect heterogeneous effects of hyperthermia on local oxygenation. The peak width changes in tumor and muscle were significantly different, perhaps due to abnormal tumor vasculature and metabolism. Response to hyperthermia measured by MRI may be useful for identifying and/or characterizing suspicious lesions as well as guiding the development of new hyperthermia protocols.

Flexible H2O2 in Water: Electronic Structure from Photoelectron Spectroscopy and Ab Initio Calculations

The effect of hydration on the electronic structure of H(2)O(2) is investigated by liquid-jet photoelectron spectroscopy measurements and ab initio calculations. Experimental valence electron binding energies of the H(2)O(2) orbitals in water are, on average, 1.9 eV red-shifted with respect to the gas-phase molecule. A smaller width of the first peak was observed in the photoelectron spectrum from the solution. Our experiment is complemented by simulated photoelectron spectra, calculated at the ab initio level of theory (with EOM-IP-CCSD and DFT methods), and using path-integral sampling of the ground-state density. The observed shift in ionization energy upon solvation is attributed to a combination of nonspecific electrostatic effects (long-range polarization) and of the specific interactions between H(2)O(2) and H(2)O molecules in the first solvation shell. Changes in peak widths are found to result from merging of the two lowest ionized states of H(2)O(2) in water due to conformational changes upon solvation. Hydration effects on H(2)O(2) are stronger than on the H(2)O molecule. In addition to valence spectra, we report oxygen 1s core-level photoelectron spectra from H(2)O(2)(aq), and observed energies and spectral intensities are discussed qualitatively.

Characterization of copolymerization of acrylonitrile with the functionalized comonomers in dimethyl sulfoxide solvent and copolymers suitable for carbon fibers

AbstractFree-radical solution copolymerization of acrylonitrile (AN) with four comonomers including itaconic acid (IA), acrylamide (AM), methyl acrylate (MA) and ammonium salt of itaconic acid (AIA) were carried out respectively. Every copolymerization process has been named as AN/IA system, AN/AM system, AN/MA system and AN/AIA system respectively, and the attained polymer is regarded as AN/IA, AN/AM, AN/MA and AN/AIA copolymer respectively. Effect of different comonomers on the polymerization kinetics and viscosity of the spinning drop are discussed in detail. The exothermic reaction of polyacrylonitrile (PAN) precursors is determined by differential scanning calorimetry (DSC), and effect of the different comonomers on the stabilization exotherm properties of PAN precursors were also studied. It has been shown that the rate of polymerization decreases distinctly with an increase of IA content, the ammonium modification can obviously increase the hydrophilicity of copolymer. The falling ball viscosity of AN/IA system is lower when compared with the other three systems, but when under the low concentration of monomer, AN/MA system has the highest viscosity. Electron paramagnetic resonance (EPR) indicates that the peak width change for the different copolymer be mainly caused by the spin-spin interaction. The copolymer of AN/AM has the lowest starting-exothermal reaction temperature and AM can alleviate the exothermic reaction and moderate the stabilization exotherm

X-ray Absorption Spectroscopy of Aqueous Aluminum-Organic Complexes

Aqueous-phase X-ray absorption near-edge structure (XANES) spectra were collected on dissolved Al complexes with organic ligands, including desferrioxamine B, EDTA, acetohydroxamate, malate, oxalate, and salicylate. Spectral interpretations were made using the density functional theory-based modeling package StoBe. The goals of this work were to study the geometric and electronic structural characteristics of these complexes relative to Al(H(2)O)(6)(3+) and to examine the utility of the aqueous Al XANES technique as a tool for probing Al speciation and structure. In the case of EDTA, aqueous Fourier-transform infrared spectroscopy was also used to corroborate the structures of the Al(EDTA)(-) and AlOH(EDTA)(2-) complexes. Synthetic XANES spectra calculated with StoBe reproduced the observed spectral differences between Al(H(2)O)(6)(3+), Al(dfoB)(+), and Al(EDTA)(-). The narrower XANES feature observed for Al(dfoB)(+) relative to Al(H(2)O)(6)(3+) can be attributed to a weaker splitting of the Al 3p-O 2p interactions in the former, while Al(EDTA)(-) exhibits split Al 3p-ligand interactions that likely result from the mixed O/N coordination. In complexes with mixed aqua/organic-oxygen ligation (Al-acetohydroxamate, Al-malate, Al-oxalate, and Al-salicylate), spectra exhibit linear, systematic changes in peak width as a function of H(2)O to organic ligand ratio in the Al coordination sphere. These results highlight the sensitivity of the aqueous Al K-edge XANES spectrum to coordination environment and demonstrate its utility as an experimental probe for future studies of Al speciation in complex solutions.