Small Stacks Research Articles

Influence of Multidimensional Graphene Oxide (GO) Sheets on Anti-Biofouling and Desalination Performance of Thin-Film Composite Membranes: Effects of GO Lateral Sizes and Oxidation Degree.

The influence of the lateral size and the content of graphene oxide (GO) flakes in specific oxygenate functional groups on the anti-biofouling properties and performance of thin-film composite membrane (TFC) was studied. Three different multidimensional GO samples were prepared with small (500–1200 nm), medium (1200–2300 nm), and large (2300–3600 nm) size distribution, and with different degrees of oxidation (GO3 > GO2 > GO1), varying the concentration of the hydrogen peroxide amount during GO synthesis. GO1 sheets’ length have a heterogeneous size distribution containing all size groups, whilst GO2 is contained in a medium-size group, and GO3 is totally contained within a small-size group. Moreover, GO oxygenate groups were controlled. GO2 and GO3 have hydroxyl and epoxy groups at the basal plane of their sheets. Meanwhile, GO1 presented only hydroxyl groups. GO sheets were incorporated into the polyamide (PA) layer of the TFC membrane during the interfacial polymerization reaction. The incorporation of GO1 produced a modified membrane with excellent bactericidal properties and anti-adhesion capacity, as well as superior desalination performance with high water flow (133% as compared with the unmodified membrane). For GO2 and GO3, despite the significant anti-biofouling effect, a detrimental impact on desalination performance was observed. The high content of large sheets in GO2 and small sheet stacking in GO3 produced an unfavorable impact on the water flow. Therefore, the synergistic effect due to the presence of large- and small-sized GO sheets and high content of OH-functional groups (GO1) made it possible to balance the performance of the membrane.

SAR Tomography at the Limit: Building Height Reconstruction Using Only 3–5 TanDEM-X Bistatic Interferograms

Multi-baseline interferometric synthetic aperture radar (InSAR) techniques are effective approaches for retrieving the 3-D information of urban areas. In order to obtain a plausible reconstruction, it is necessary to use more than twenty interferograms. Hence, these methods are commonly not appropriate for large-scale 3-D urban mapping using TanDEM-X data where only a few acquisitions are available in average for each city. This work proposes a new SAR tomographic processing framework to work with those extremely small stacks, which integrates the non-local filtering into SAR tomography inversion. The applicability of the algorithm is demonstrated using a TanDEM-X multi-baseline stack with 5 bistatic interferograms over the whole city of Munich, Germany. Systematic comparison of our result with TanDEM-X raw digital elevation models (DEM) and airborne LiDAR data shows that the relative height accuracy of two third buildings is within two meters, which outperforms the TanDEM-X raw DEM. The promising performance of the proposed algorithm paved the first step towards high quality large-scale 3-D urban mapping.

Fragmentation of the Golgi complex of dopaminergic neurons in human substantia nigra: New cytopathological findings in Parkinson's disease.

Fragmentation of the Golgi ribbon is a common feature of Parkinson´s disease and other neurodegenerative diseases. This alteration could be the consequence of the anterograde and retrograde transport imbalance, α-synuclein aggregates, and/or cytoskeleton alterations. Most information on this process has been obtained from cellular and animal experimental models, and as such, there is little information available on human tissue. If the information on human tissue was available, it may help to understand the cytopathological mechanisms of this disease. In the present study, we analyzed the morphological characteristics of the Golgi complex of dopaminergic neurons in human samples of substantia nigra of control and Parkinson's disease patients. We measured the expression levels of putative molecules involved in Golgi fragmentation, including α-synuclein, tubulin, and Golgi-associated regulatory and structural proteins. We show that, as a consequence of the disease, the Golgi complex is fragmented into small stacks without vesiculation. We found that only a limited number of regulatory proteins are altered. Rab1, a small GTPase regulating endoplasmic reticulum-to-Golgi transport, is the most dramatically affected, being highly overexpressed in the surviving neurons. We found that the SNARE protein syntaxin 5 forms extracellular aggregates resembling the amyloid plaques characteristic of Alzheimer's disease. These findings may help to understand the cytopathology of Parkinson's disease.

Numerical and Experimental Investigation of the Through-Thickness Strength Properties of Woven Glass Fiber Reinforced Polymer Composite Laminates under Combined Tensile and Shear Loading

The purpose of this paper is to investigate the through-thickness stresses of woven glass fiber reinforced polymer (GFRP) composite laminates under combined tensile and shear loading. Tensile tests were carried out with cross specimens at room temperature under various stacking angles, and the through-thickness strength properties of the woven GFRP laminates were evaluated. The failure characteristics of the woven GFRP laminates were also studied by optical microscopy observations. A three-dimensional finite element analysis (FEA) was carried out to calculate the stress distributions in the cross specimens, and the failure conditions of the specimens were examined. The numerically determined interlaminar tensile and shear stresses at failure location were consistent with Hoffman and Mohr-Coulomb failure criteria when the stacking angle was relatively small. This work is the first attempt to quantify the relation between interlaminar tensile and shear strengths of GFRP composite laminates under tensile and shear loading simultaneously using a combined numerical and experimental approach. A method based on finite element stress analysis was developed for estimating the through-thickness strength of the composite laminates using the experimentally determined fracture load and location. The results suggest that the through-thickness strength under combined tensile and shear loading can be determined effectively by this approach for relatively small stacking angles.

Strengthening CoCrNi medium-entropy alloy by tuning lattice defects

The CrCoNi medium-entropy alloy is not fully utilized at room temperature circumstance due to its low strength, despite excellent cryogenic mechanical properties. Here we report that, a superior room temperature strength (1.6 GPa and 407.6 Hv) has been obtained in the single phase CoCrNi medium-entropy alloy, by carefully tuning the formation of multiple lattice defects. Electron microscopy characterizations show that such high-strength CoCrNi alloy contains favorable heterostructures of coarsening grains (~30 μm) and ultrafine grains (~1 μm), together with the high density of dislocation cells, small stacking faults, ultrafine nanotwins (~9 nm in thickness) and Lomer–Cottrell locks.

Fixed air flow-rate selection by considering the self-regulating function of low power air-cooled PEMFC stack

In this study, it is found that the air-cooled proton exchange membrane fuel cell (PEMFC) has a self-regulating function in terms of its thermal and water balances within the fuel cell. Such a function enables the fuel cell's operation to be stable and efficient without any electronic controlling circuit to control the operating parameters. A small air-cooled PEMFC stack (15 cells with a rate power of 60 W) integrated with an axial fan is used for this experimental study to verify the self-regulating feature. The results show that the air-cooled open-cathode PEMFC stack can run stably and efficiently under a wide range of load currents at a fixed air flow rate. The best fuel cell performance and maximum system net power output are achieved at an air flow of 55.7 SLPM. To further validate the results, the temperature distribution and cell voltage distribution of the stack are simultaneously measured under different loads. The results demonstrate that the temperature and cell voltage of the stack are evenly distributed at the air flow of 55.7 SLPM. The present study may provide guidance in the design of a cooling subsystem of a small and compact fuel cell system incorporating an air-cooled open-cathode PEMFC.

Characterizing Stack Degradation in Proton-Conducting Ceramic Fuel Cells and Electrolyzers

We present our efforts to scale-up proton-conducting ceramic fuel cells (PCFC) for integration into small multi-cell stacks. Proton-conducting ceramics are an exciting new class of materials that are now emerging from research laboratories to address societal challenges in electricity generation, energy storage, and fuels synthesis. While there are many technologies under investigation, intermediate temperature proton-conducting fuel cells (PCFC) have been drawing attention due to their high performance at low temperatures in fuel cell mode (up to ~2 Wcm2 at 600 ºC) and their high efficiency (90 – 98 % Faradic efficiency) when operated in electrolysis mode. However despite the impressive achievements at lab-scale PCFC technology limited investments have been made on the scaling up process due to the challenges that the PCFC fabrication procedure represents. In fact, there are no stack demonstrations reported to date in the archival literature. In this presentation we will review our efforts at Colorado School of Mines to increase the size of PCFCs beyond the button-cell level, and to integrate these cells into multi-cell stack assemblies. The stability of our PCFC stack reached the degradation rates of 3.5% and 2.1% per 1000 hours, respectively, under fuel cell and electrolysis modes.An illustration of our stack design is shown in Figure 1, and includes a photograph of a fully assembled three-cell stack after performance testing. The design is centered on three repeating components: the protonic-ceramic electrolysis cells, the composite-ceramic frames in which the cells are bonded, and the thin metallic interconnect / bipolar plates that conduct electricity between adjacent cells. The cells feature a dense, 20 μm-thick BaCe0.4Zr0.4Y0.1Yb0.1O3- d (BCZYYb4411) electrolyte on a porous Ni-BCZYYb4411 anode fabricated through reactive-sintering methods. The cathode is a novel BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY) atop of the BCZYYb4411 electrolyte with the maximum active area of ~ 7cm2 per single unit cell. Reactive gases are fed through fuel and oxidizer ports machined into the frame. The metallic interconnect is a ferritic steel developed for intermediate-temperature solid-oxide fuel cells and electrolyzers, and is compression sealed to the frame. Metallic meshes (not shown) electrically connect the electrodes to the interconnects.High protonic-ceramic cell performance operating at 550 0C has been previously demonstrated at Colorado School of Mines. While the lower operating temperature should present benefits for the long-term stability of the stack it also brings questions regarding the behavior of stack materials such as the interconnects which represent a source of degradation in performance depending on the composition of the scale that is grown on them. In an effort to better understand the root causes behind performance degradation processes in our protonic-ceramic stacks, we have integrated numerous voltage-taps throughout the stack shown in Figure 1. In this presentation, we will review our results for long-term protonic-ceramic stack operation under both fuel cell and electrolysis mode, discuss after-test interconnects analysis showing high-iron-content scale and present strategies for reducing degradation rates and extending stack life. Figure 1

Antibacterial and mechanical properties of reduced graphene-silver nanoparticle nanocomposite modified glass ionomer cements

ObjectivesGlass ionomer cements (GIC) are widely recognized as important dental restorative materials whilst they often suffer from restoration failures due to the poor mechanical properties and secondary caries. Reduced graphene-silver nanoparticle (R-GNs/Ag) nanocomposite exhibits excellent antibacterial activities. This study aimed to evaluate the antibacterial and mechanical properties of GIC modified by incorporation of different proportion of R-GNs/Ag. MethodsR-GNs/Ag nanoparticles were incorporated into conventional glass ionomer powder at 0–2.00 wt.% concentration and cement specimen were prepared. The antibacterial properties of R-GNs/Ag modified GIC materials were investigated by direct contact test (DCT), scanning electron microscopy (SEM) observation, XTT assay and bacteria live/dead assay. Flexural strength and surface microhardness were measured by a universal testing machine and a microhardness tester, respectively. ResultsThe DCT demonstrated an obvious decrease of S. mutans quantity with incorporation of 2.00 wt.% nanoparticles (p < 0.05). SEM images showed fewer bacteria and smaller stacks on the surface of modified specimens. No significant difference was found in the metabolic activity of S. mutans according to the XTT assay (p < 0.05). The addition of 1.00 and 2.00 wt.% R-GNs/Ag significantly decreased the percentage of viable bacteria (p < 0.05). There was no significant decrease of flexural strength and surface microhardness with incorporation of up to 2.00 wt.% nanocomposite (p < 0.05). ConclusionsR-GNs/Ag nanocomposite might be a promising agent to improve the antibacterial activity of dental restorative GIC without compromising its mechanical properties. Clinical significanceR-GNs/Ag nanocomposite can serve as a potential modifier for dental restorative materials.

Development of Metallic Contaminant Inspection System Using High-Tc rf-SQUID for Li-ion Battery Liquid Components

The use of a high-Tc (HTS) rf-superconducting quantum interference device (SQUID) for inspecting the liquid component of lithium-ion (Li-ion) batteries is proposed. It is possible that a small amount of metal can become mixed in with components of Li-ion batteries during the manufacturing process and contaminate them, with a resultant fire risk, Thus, the development of a highly sensitive inspection system is required. In this article we describe a test system, we developed using a single channel HTS rf-SQUID consisting of a cryostat, a polyethylene tube, and a permanent magnet. The SQUID needs to be installed as close to the battery liquid as possible to obtain more sensitive readings. Therefore, we designed a microscope-type SQUID cryostat in which the SQUID can approach the target as close as 1 mm. In the system, the liquid was not flowed through the polyethylene tube, but a small metallic sample stack on a fishing line was moved by a motor. A stainless steel cut wire with a nominal size of φ 50 μm was prepared. After magnetizing the sample, the stray magnetic field of the sample was measured by the SQUID. The peak-to-peak signal scaled inversely with the cube of the stand-off distance. It was found that a signal of the sample with φ 50 μm at a distance of 26 mm could be detected if the signal-to-noise ratio ( SNR ) > 3 was supposed as the threshold of the inspection. The dependence on the sample size was also investigated, using stainless steel samples with different sizes (φ 50–φ 160 μm). The peak-to-peak signal scaled with the cube of the diameter.

Clinical Faceoff: Suprapatellar Tibial Nailing for Tibia Fractures.

Clinical Faceoff: Suprapatellar Tibial Nailing for Tibia Fractures.

Robustness Improvement on PMU Based Dynamic Equivalent Modeling of Distributed Small Hydropower Generator Stacks

Due to the geographic features and fruitful water resources, the distributed generation of Small Hydropower Generator Stack (SHGS) are vigorously developed in southwest China. As the more concerns about security and stability of power grids with the large amount of SHGS feed into the grid, the accurate models are critical to analyze those potential impacts. With the development of online monitoring technologies in smart grid, PMU based dynamic equivalent modeling for SHGS drawn many attentions. However, field applications reveal that traditional SHGS equivalent model may not be robustness enough to adapt the different disturbances. To overcome this deficiency, method to improve the robustness of SHGS dynamic equivalent modeling is proposed. In the paper, a coherency identification based multi-machine modeling method is introduced to enhance the accuracy of equivalent model. Sensitivity and correlation analysis based key parameters selection scheme is implemented to select the critical parameters, meanwhile avoiding the multiple solutions problem. Moreover, multi-objective optimization algorithm is designed for key parameters identification of the equivalent model. Additionally, hybrid dynamic simulation has adopted into the equivalent process to improve the computational efficiency. The effectiveness of the proposed method has been validated with an actual case from China Southwest grids.

A novel simplified model for measuring the twinnability of face-centred-cubic metals

ABSTRACTTwinnability is a unique property describing the ease with which a metal plastically deforms by twinning relative to dislocation-mediated slip. Based on first-principles calculations, a simple and effective model, including two calculational supercells with three typical generalised stacking fault structures, is proposed to measure the twinnability of face-centred-cubic metals. Here, we investigated the interaction of alloying atoms with generalised stacking faults and their impact on the twinnability of aluminium alloys. It is found that the twin propensity of Al alloy increases with the increasing concentration of Sc and Ti, and a small increase with Y, while the addition of Sr, Zn, Sn and Ga exhibits opposite trends. It is predicted that twins will remain stable once they were formed in Al–Sc alloys on account of the small extrinsic stacking fault energy.

Building 3-D Reconstruction With a Small Data Stack Using SAR Tomography

Synthetic aperture radar (SAR) tomography (TomoSAR) has been well established for the 3-D reconstruction of urban buildings. Many methods have been proposed in the literature for TomoSAR inversion. These methods usually require fairly large data stacks (more than 20 images) for reliable reconstruction. Hence, they cannot be applied to the 3-D reconstruction of urban buildings using Gaofen-3 (GF-3) data directly, because there are few images available on average in each city. This article proposes a novel workflow for the 3-D reconstruction of high-rise buildings using small data stacks. In this workflow, we combine the methods of contour line extraction (CLE) and reference-elevation multilooking relaxation (RM-RELAX) for the 3-D reconstruction of high-rise buildings. The CLE method extracts contour lines of buildings relying on a data-driven approach and does not need to rely on any external data, which can provide prior knowledge for subsequent processing. The RM-RELAX method is an extension of RELAX, which can obtain more precise 3-D inversion with multilooking and reject outliers with the reference elevation (which can be obtained by the prior knowledge of contour lines) of each pixel. The applicability of this workflow is demonstrated by using simulated data and real data with six SAR images acquired by the GF-3 satellite over an area in Beijing, China.

Sodium(I)-doped graphitic carbon nitride with appropriate interlayer distance as a highly selective sorbent for strontium(II) prior to its determination by ICP-OES.

Multilayered and porous sodium-doped graphitic carbon nitride (GCN-Na) was prepared and employed to the solid-phase extraction of Sr(II). The sorbent exhibits high adsorption capacity and excellent selectivity for Sr(II). This is due to its small interplanar stacking distance caused by doping with Na(I) which matches the size of Sr(II) better than blank GCN. An original solid-phase extraction method based on GCN-Na coupled with ICP-OES was established for Sr(II), the calibration plots are linear ranging from 0.05-10mg·kg-1 with the correlation coefficients (R2) above 0.999, the limits of detection are in the range of 0.57-1.52μg·kg-1 and the preconcentration factor of 80 is achieved using 48mL sample. It was successfully applied in the extraction and detection of trace Sr(II) in tap water, rice and sea fish. Graphical abstractA multilayer porous sodium(I) doped graphitic carbon nitride nanosheet (GCN-Na) was synthesized and exhibited excellent adsorption capability and selectivity for Sr(II).

Histological and ultrastructural studies on the effect of amoxicillin on the liver of mice foetuses

Introduction: In spite of the beneficial role of the beta-lactam antibiotics in the treatment of many cases of urinary tract infections, acute otitis media, and pneumonia, yet some medical reports incriminating it in producing certain adverse consequences following its use. Antibiotics remain important in pregnancy and may be second to only iron and food supplement.Aim of Work: Hence, the present investigation was carried out to evaluate the effect of two doses of the beta-lactam antibiotic amoxicillin on the liver of maternally treated foetuses.Materials and Methods: The pregnant female mice were allocated into three groups. The pregnant mothers of the first group served as control group (injected intra peritoneally with the drug solvent) and those of the other two groups were injected intra peritoneally for 8 days from day 7 till day14 during gestation with the low dose (205 mg/ kg body weight) and high dose (820 mg/ kg body weight) of the beta-lactam antibiotics amoxicillin.Results: The histological examination of the foetal liver sections of amoxicillin-treated groups showed vacuolar and fatty degenerations in the cytoplasm of the hepatocytes, as well as inflammatory cell infiltration. At the ultrastructure level, the hepatocytes of maternally treated foetuses revealed conspicuous alternations, represented by devastations of mitochondria that displayed loss of their cristae and their internal matrices materials. Fragmentation of the cisternae of rough endoplasmic reticulum into smaller stacks was also observed.Conclusion: The use of such doses of the beta-lactam antibiotic amoxicillin induces morphological alterations in fotal liver of mice subjected to this antibiotic during the period of gestation

Size-Dependent Local Ordering in Melanin Aggregates and Its Implication on Optical Properties.

We present atomic scale models of differently sized eumelanin nanoaggregates from molecular dynamics simulations combined with a simulated annealing procedure. The analysis reveals the formation of secondary structures due to π-stacking on one hand, but on the other hand a broad distribution of stack geometries in terms of stack size, horizontal displacement angles, and relative torsion angles. The displacement angle distribution, which is a measure of the occurrence of zigzag and linear stacking motives, respectively, strongly depends on the aggregate size-and is hence controlled by the interplay of surface and bulk energy terms. Semiempirical spectra calculations of small stacks (up to five protomolecules) reveal a strong dependence on the precise stack structure and allow for a direct structure-property correlation. The observed spectral shifts result in an overall spectral broadening and, hence, further support the geometric disorder model, which complements the chemical disorder model in the interpretation of eumelanin's monotonically increasing broad-band absorption.

Misplaced Golgi Elements Produce Randomly Oriented Microtubules and Aberrant Cortical Arrays of Microtubules in Dystrophic Skeletal Muscle Fibers

Differentiated mammalian cells and tissues, such as skeletal muscle fibers, acquire an organization of Golgi complex and microtubules profoundly different from that in proliferating cells and still poorly understood. In adult rodent skeletal muscle, the multinucleated muscle fibers have hundreds of Golgi elements (GE), small stacks of cisternae that serve as microtubule-organizing centers. We are interested in the role of the GE in organizing a peculiar grid of microtubules located in the fiber cortex, against the sarcolemma. Modifications of this grid in the mdx mouse model of Duchenne muscular dystrophy have led to identifying dystrophin, the protein missing in both human disease and mouse model, as a microtubule guide. Compared to wild-type (WT), mdx microtubules are disordered and more dense and they have been linked to the dystrophic pathology. GE themselves are disordered in mdx. Here, to identify the causes of GE and microtubule alterations in the mdx muscle, we follow GFP-tagged microtubule markers in live mdx fibers and investigate the recovery of GE and microtubules after treatment with nocodazole. We find that mdx microtubules grow 10% faster but in 30% shorter bouts and that they begin to form a tangled network, rather than an orthogonal grid, right after nucleation from GE. Strikingly, a large fraction of microtubules in mdx muscle fibers seem to dissociate from GE after nucleation. Moreover, we report that mdx GE are mispositioned and increased in number and size. These results were replicated in WT fibers overexpressing the beta-tubulin tubb6, which is elevated in Duchenne muscular dystrophy, in mdx and in regenerating muscle. Finally, we examine the association of GE with ER exit sites and ER-to-Golgi intermediate compartment, which starts during muscle differentiation, and find it persisting in mdx and tubb6 overexpressing fibers. We conclude that GE are full, small, Golgi complexes anchored, and positioned through ER Exit Sites. We propose a model in which GE mispositioning, together with the absence of microtubule guidance due to the lack of dystrophin, determines the differences in GE and microtubule organization between WT and mdx muscle fibers.

Structural control on karst water circulation and speleogenesis in a lithological contact zone: The Bossea cave system (Western Alps, Italy)

Geological surveys, structural mapping, and thin section analysis helped to unravel the speleogenesis and water circulation in the Bossea cave (Northern Italy), an unconventional karst system at the contact between carbonates and underlying insoluble rocks. The surveys within the cave and in the surrounding surface outcrops revealed a complex structural setting caused by the coupling of lithological-mechanical heterogeneities with two major regional left-lateral ESE-WNW strike-slip faults. Transpression associated with the faults led to a disharmonic deformation, accommodated by a detachment surface, between the buckled basement meta-volcanics and the disharmonically-folded-marble sequence laying on top. Low-angle shear zones, recumbent or drag folds, and small stacks of duplexes are localized next to this detachment. The preferential pathways for water circulation inside the vadose zone are the folded bedding interfaces in the meta-carbonate sequence. Fracture clusters at slipping bed terminations, on the other hand, provide through-sequence connectivity. Once underground stream water flow reached the cataclastic and highly deformed meta-volcanics of the detachment core and damage zones, erosion started, removing large volumes of rocks. The downward erosion of the Permian basement rocks caused gravitational instability and subsequent roof collapses, aided by structural control in the damage zone above the detachment surface (slip surfaces in between duplexes or drag folds). This gravitational instability ultimately led to the formation of the giant halls that are characteristic of the downstream part of the Bossea cave.

Comparative Microstructural Analysis of Nongraphitic Carbons by Wide-Angle X-ray and Neutron Scattering

Non-graphitic carbons (NGCs) represent the most abundant class of sp2-hybridized carbon, materials (coal char coal, activated carbon, etc.). These carbons consist of small graphene layer stacks pos...

Dielectric and flash DSC investigations on an epoxy based nanocomposite system with MgAl layered double hydroxide as nanofiller

Nanocomposites based on MgAL layered double hydroxides (LDH) and an epoxy resin were prepared and investigated by a combination of complementary methods. As epoxy resin Bisphenol A diglycidyl ether (DGEBA) was used with Diethylenetriamine as curing agent. The LDH was modified with taurine, which acts as an additional crosslinking agent due to its amine groups. The epoxy resin was cured in a presence of the nanofiller, which was added to the system in various concentrations. X-ray scattering, by combination of SAXS and WAXS was used to characterize the morphology of the obtained nanocomposites. These investigations show that the filler is distributed in the matrix as small stacks of ca. 10 layers. The molecular dynamics of the system, as probe for structure, was investigated by broadband dielectric spectroscopy. In addition to the β- and α-relaxation (dynamic glass transition), characteristic for the unfilled materials, a further process was found which was assigned to localized fluctuations of segments physically adsorbed or chemically bonded to the nanoparticles. The dielectric α-relaxation is shifted to higher temperatures for the nanocomposites in comparison to the pure material but depends weakly on the content of nanoparticles. Further, for the first time Flash DSC was employed to a thermosetting system to investigate the glass transition behavior of the nanocomposites. The heating rates were converted in to relaxation rates. For low concentrations of the nanofiller the thermal data overlap more or less with that of the pure epoxy. For higher concentrations the thermal data are shifted significantly to higher temperatures. This is discussed in terms the cooperativity approach to the glass transition.