Perhaps more than any other “-omics” endeavor, the accuracy and level of detail obtained from mapping the major connection pathways in the living human brain with diffusion MRI depend on the ...capabilities of the imaging technology used. The current tools are remarkable; allowing the formation of an “image” of the water diffusion probability distribution in regions of complex crossing fibers at each of half a million voxels in the brain. Nonetheless our ability to map the connection pathways is limited by the image sensitivity and resolution, and also the contrast and resolution in encoding of the diffusion probability distribution.
The goal of our Human Connectome Project (HCP) is to address these limiting factors by re-engineering the scanner from the ground up to optimize the high b-value, high angular resolution diffusion imaging needed for sensitive and accurate mapping of the brain's structural connections. Our efforts were directed based on the relative contributions of each scanner component. The gradient subsection was a major focus since gradient amplitude is central to determining the diffusion contrast, the amount of T2 signal loss, and the blurring of the water PDF over the course of the diffusion time. By implementing a novel 4-port drive geometry and optimizing size and linearity for the brain, we demonstrate a whole-body sized scanner with Gmax=300mT/m on each axis capable of the sustained duty cycle needed for diffusion imaging. The system is capable of slewing the gradient at a rate of 200T/m/s as needed for the EPI image encoding. In order to enhance the efficiency of the diffusion sequence we implemented a FOV shifting approach to Simultaneous MultiSlice (SMS) EPI capable of unaliasing 3 slices excited simultaneously with a modest g-factor penalty allowing us to diffusion encode whole brain volumes with low TR and TE. Finally we combine the multi-slice approach with a compressive sampling reconstruction to sufficiently undersample q-space to achieve a DSI scan in less than 5min. To augment this accelerated imaging approach we developed a 64-channel, tight-fitting brain array coil and show its performance benefit compared to a commercial 32-channel coil at all locations in the brain for these accelerated acquisitions.
The technical challenges of developing the over-all system are discussed as well as results from SNR comparisons, ODF metrics and fiber tracking comparisons. The ultra-high gradients yielded substantial and immediate gains in the sensitivity through reduction of TE and improved signal detection and increased efficiency of the DSI or HARDI acquisition, accuracy and resolution of diffusion tractography, as defined by identification of known structure and fiber crossing.
•Approach for advancing the sensitivity of the diffusion connectivity measurement.•Optimization of Gmax=300mT/m gradient, RF coil and sequence.•Improved sensitivity and diffusion contrast in high quality DSI/Q Ball.
Because of its acidic and oxidative nature, iron gall ink promotes the endogenous degradation of paper manuscripts. Mechanical damage in areas of concentrated ink application or along mechanically ...stressed edges or folds results in problems during storage and handling. So far, such strongly degraded areas have usually been stabilized locally with thin Japanese paper and adhesives. A new and innovative material—nanocellulose—is being evaluated as a stabilizer for manuscripts that have been degraded by iron gall ink. The aim of this study is to integrate the nanocellulose application into a multi-stage calcium phytate/calcium hydrogencarbonate treatment to combine deacidification and stabilization, thus avoiding an additional stabilization and drying step. Two different types of fibrillated nanocelluloses were applied on manuscripts damaged by iron gall inks in different treatment steps. The newly formed, interlinked network of nanocellulose and paper was characterised before and after accelerated degradation in closed vials. The effects on the paper cellulose were studied by size exclusion chromatography and light scattering with carbonyl group profiling to follow cellulose hydrolysis and oxidation pathways. In addition, the migration behavior of iron ions was examined by laser ablation coupled with metal analysis (ICP-MS). This paper discusses the applicability and stability of nanocellulose on paper damaged by iron gall ink with regard to its long-term performance. Advantages and limitations are covered in detail.
► Six different single- and two-step carbohydrate derivatisation approaches compared. ► Reference compounds comprised 8 monosaccharides (C5–C6), GA and DHA. ► Ethoximation–trimethylsilylation was ...found to be superior to other approaches. ► Analysis of carbohydrate-rich matrices of different origin is possible. ► Calculation of a novel matrix impact value is proposed to evaluate matrix effects.
Gas chromatographic analysis of complex carbohydrate mixtures requires highly effective and reliable derivatisation strategies for successful separation, identification, and quantitation of all constituents. Different single-step (per-trimethylsilylation, isopropylidenation) and two-step approaches (ethoximation–trimethylsilylation, ethoximation–trifluoroacetylation, benzoximation–trimethylsilylation, benzoximation–trifluoroacetylation) have been comprehensively studied with regard to chromatographic characteristics, informational value of mass spectra, ease of peak assignment, robustness toward matrix effects, and quantitation using a set of reference compounds that comprise eight monosaccharides (C5–C6), glycolaldehyde, and dihydroxyacetone. It has been shown that isopropylidenation and the two oximation-trifluoroacetylation approaches are least suitable for complex carbohydrate matrices. Whereas the former is limited to compounds that contain vicinal dihydroxy moieties in cis configuration, the latter two methods are sensitive to traces of trifluoroacetic acid which strongly supports decomposition of ketohexoses. It has been demonstrated for two “real” carbohydrate-rich matrices of biological and synthetic origin, respectively, that two-step ethoximation–trimethylsilylation is superior to other approaches due to the low number of peaks obtained per carbohydrate, good peak separation performance, structural information of mass spectra, low limits of detection and quantitation, minor relative standard deviations, and low sensitivity toward matrix effects.
The qualitative and quantitative analysis of complex carbohydrate mixtures is a challenging problem. When tackled by GC/MS, close retention times and largely similar mass spectra with no specific ...features complicate unambiguous identification, especially of monosaccharides. An optimized pre-capillary ethoximation-silylation GC/MS method for determination of monosaccharides and disaccharides was applied to a wide range of analytes (46 compounds). The two-step derivatization resulted in a pair of syn and anti peaks with specific retention and intensity ratio. The resulting dataset of mass spectra was subjected to a PCA-based pattern recognition. An oxime peak identifier (OPI) of the carbohydrate analytes, based on the combination of an internal standard and the corresponding syn/anti peak ratios, increased the reliability of the identification of reducing carbohydrates. Finally, the introduced EtOx-TMS derivatization method was applied to four different carbohydrate matrices (agave sirup, maple sirup, palm sugar, and honey).
•Optimization of an EtOx/TMS derivatisation method for GC/MS analysis.•Evaluation of chromatographic and mass spectra characteristics of 46 carbohydrates.•Parameters were syn/anti peaks ratio, elution order and time shift between the peaks.•Dataset of mass spectra was subject to a PCA-based pattern recognition.•An oxime peak identifier (OPI) improves carbohydrate identification.
In this study, a novel approach for isolation and purification of lignosulfonates from spent sulfite liquor was established. This approach involves sorption onto macroreticular non-ionic poly(methyl ...methacrylate) beads (XAD-7 resin) and subsequent desorption with organic solvents to obtain lignosulfonates of high purity. The method was optimized, verified and tested on four industrial lignosulfonate liquors from different processes and compared with an established ultrafiltration protocol. The method proved to be reproducible, robust and significantly faster than ultrafiltration.
In this study, a novel approach for isolation and purification of lignosulfonates from spent sulfite liquor was established.
Previous studies have shown that under some conditions, noise fluctuations in an fMRI time-course are dominated by physiological modulations of the image intensity with secondary contributions from ...thermal image noise and that these two sources scale differently with signal intensity, susceptibility weighting (TE) and field strength. The SNR of the fMRI time-course was found to be near its asymptotic limit for moderate spatial resolution measurements at 3 T with only marginal gains expected from acquisition at higher field strengths. In this study, we investigate the amplitude of image intensity fluctuations in the fMRI time-course at magnetic field strengths of 1.5 T, 3 T, and 7 T as a function of image resolution, flip angle and TE. The time-course SNR was a similar function of the image SNR regardless of whether the image SNR was modulated by flip angle, image resolution, or field strength. For spatial resolutions typical of those currently used in fMRI (e.g., 3 × 3 × 3 mm
3), increases in image SNR obtained from 7 T acquisition produced only modest increases in time-course SNR. At this spatial resolution, the ratio of physiological noise to thermal image noise was 0.61, 0.89, and 2.23 for 1.5 T, 3 T, and 7 T. At a resolution of 1 × 1 × 3 mm
3, however, the physiological to thermal noise ratio was 0.34, 0.57, and 0.91 for 1.5 T, 3 T and 7 T for TE near T2*. Thus, by reducing the signal strength using higher image resolution, the ratio of physiologic to image noise could be reduced to a regime where increased sensitivity afforded by higher field strength still translated to improved SNR in the fMRI time-series.
► The study first time demonstrated the formation of oxidized functional groups along oat β-glucan chain during selected food processes. ► Oat β-glucan oxidized, when its solutions were treated with ...ascorbic acid, heat (120°C) or high pressure homogenisation. ► Oxidation was obtained as the conversion of the hydroxyl groups of the β-glucan to the carbonyl groups, cleavage of β-glucan chain and viscosity loss of β-glucan solutions. In addition, the degraded chains formed highly compact high molar mass species.
The study investigated carbonyl group formation along the chain and the chain cleavage of cereal β-glucan during heat treatments, high pressure homogenisation, cold storage and ascorbic acid treatment of aqueous solutions of this soluble dietary fibre. The carbonyl group content and its distribution along the chain were simultaneously determined with the chain cleavage using a HPSEC/labelling method, originally developed for water-insoluble cellulose. Ascorbic acid treatment resulted in a relatively high degree of carbonyl content and extensive degradation of β-glucan, even in concentrations typically found in foods. The thermal oxidation of the β-glucan was considerable at 120°C in a β-glucan solution with co-extracted compounds from oat ingredient, and in the highly purified solutions in presence of ferrous ions. Oxidation also probably contributed to the molecular properties during high pressure homogenisation, even thou the main degradation mechanism is the hydrolysis caused by mechanical energy. In addition to the cleavage of the β-glucan chain, the formation of compact, high molar mass species or molecule clusters were obtained in the study after ascorbic acid, heat (120°C) and homogenisation treatments.
The detection of individual chromophores that contribute to the overall discoloration of paper or pulp (“yellowing”) is a challenge because these substances are only present in extremely small ...amounts (ppm to ppb range). In this work, paper spray (PS) coupled with mass spectrometry was used to detect a low-concentrated cellulosic key-chromophore, 2,5-dihydroxyacetophenone (DHAP). Sensitivity was enhanced by derivatization with Girard's reagent T (GT). DHAP was successfully detected in historic paper samples and also was applied to model papers in order to investigate different factors that influence its generation: temperature, time, relative humidity, and the presence of iron ions, by means of a full factorial design. The main factors, temperature and relative humidity, have the most impact on the generation of DHAP, but the interactions between the factors are also significant and are therefore important for the degradation process. The historical papers containing DHAP were then compared to the artificially aged samples. The results were confirmed by independent, accurate mass measurements.
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•Online derivatization of a keychromophore.•Quantitative method for measurement of a specific cellulosic degradation product.•Monitoring artificial ageing process while varying parameters.•Fast and reliable method.
Historical papers are often locally damaged by exogenous influences and/or have endogenously degraded paper areas. The stabilization of such papers is very important because further use of the object ...can cause additional damage. Different types of nanocellulose are interesting as a novel stabilizing materials for paper due to their close structural relation to the paper matrix. Therefore, the present study investigated whether the treatment of historical papers with nanocellulose suspensions is a novel method for paper stabilization. Two different types of nanocelluloses, bacterial cellulose and a mechanically nanofibrillated cellulose based on wood pulp, were tested with regard to their performance in stabilizing fragile papers. Concerning material handling and application in conservation steps, different ways to modify the suspensions were tested. The resulting suspensions were applied to historical papers from several centuries with different extents of damage. The paper-nanocellulose composites were characterized with regard to their optical and microscopic integrity and by physical and chemical analyses. The treatment of mechanical damage and the consolidation of weakened paper areas could be realized by the application of a nanocellulose suspension without an additional adhesive. The results of the treatment depend on the type of nanocellulose, on the paper material, on processing and application techniques. The paper discusses the applicability and stability of the differently prepared nanocellulose suspensions, also with regard to their mode of application and long-term performance. Advantages and limitations are addressed in detail.
Graphical abstract
Bacterial nanocellulose and nano-fibrillated cellulose from pulp can be used to consolidate damaged historic papers without the application of additional adhesives
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