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The DNA four-way (Holliday) junction is the central intermediate of genetic recombination, yet key aspects of its conformational and thermodynamic properties remain unclear. While multiple experimental approaches have been used to characterize the canonical X-shape conformers under specific ionic conditions, the complete conformational ensemble of this motif, especially at low ionic conditions, remains largely undetermined. In line with previous studies, our single-molecule Förster resonance energy transfer (smFRET) measurements of junction dynamics revealed transitions between two states under high salt conditions, but smFRET could not determine whether there are fast and unresolvable transitions between distinct conformations or a broad ensemble of related states under low and intermediate salt conditions. We therefore used an emerging technique, X-ray scattering interferometry (XSI), to directly probe the conformational ensemble of the Holliday junction across a wide range of ionic conditions. Our results demonstrated that the four-way junction adopts an out-of-plane geometry under low ionic conditions and revealed a conformational state at intermediate ionic conditions previously undetected by other methods. Our results provide critical information to build toward a full description of the conformational landscape of the Holliday junction and underscore the utility of XSI for probing conformational ensembles under a wide range of solution conditions.

The complex of the small molecule biotin and the homotetrameric protein streptavidin is key to a broad range of biotechnological applications. Therefore, the behavior of this extraordinarily high-affinity interaction under mechanical force is intensively studied by single-molecule force spectroscopy. Recently, steered molecular dynamics simulations have identified a low force pathway for the dissociation of biotin from streptavidin, which involves partial unfolding of the N-terminal β-sheet structure of monovalent streptavidin's functional subunit. Based on these results, we now introduced two mutations (T18C,A33C) in the functional subunit of monovalent streptavidin to establish a switchable connection (disulfide bridge) between the first two β-strands to prevent this unfolding. In atomic force microscopy-based single-molecule force spectroscopy experiments, we observed unbinding forces of about 350 pN (at a force-loading rate of 10 nN s-1) for pulling a single biotin out of an N-terminally anchored monovalent streptavidin binding pocket - about 1.5-fold higher compared with what has been reported for N-terminal force loading of native monovalent streptavidin. Upon addition of a reducing agent, the unbinding forces dropped back to 200 pN, as the disulfide bridge was destroyed. Switching from reducing to oxidizing buffer conditions, the inverse effect was observed. Our work illustrates how the mechanics of a receptor-ligand system can be tuned by engineering the receptor protein far off the ligand-binding pocket.

Significance The physiological function of proteins is often critically regulated by mechanical forces acting on them. Single-molecule manipulation techniques such as atomic force microscopy or optical tweezers have enabled unprecedented insights into the molecular mechanisms underlying such force regulation. Current limitations include the resolution at low forces and low throughput. We here introduce a versatile, modular approach for force measurements on proteins in magnetic tweezers that allows for probing dozens of single molecules in parallel, in a wide force range including very low forces, Single-molecule force spectroscopy has provided unprecedented insights into protein folding, force regulation, and function. So far, the field has relied primarily on atomic force microscope and optical tweezers assays that, while powerful, are limited in force resolution, throughput, and require feedback for constant force measurements. Here, we present a modular approach based on magnetic tweezers (MT) for highly multiplexed protein force spectroscopy. Our approach uses elastin-like polypeptide linkers for the specific attachment of proteins, requiring only short peptide tags on the protein of interest. The assay extends protein force spectroscopy into the low force (

Single-molecule cut-and-paste facilitates bottom-up directed assembly of nanoscale biomolecular networks in defined geometries and enables analysis with spatio-temporal resolution. However, arrangement of diverse molecules of interest requires versatile handling systems. The novel DNA-free, genetically encodable scheme described here utilises an orthogonal handling strategy to promote arrangement of enzymes and enzyme networks.

The small molecule biotin and the homotetrameric protein streptavidin (SA) form a stable and robust complex that plays a pivotal role in many biotechnological and medical applications. In particular, the SA-biotin linkage is frequently used in single-molecule force spectroscopy (SMFS) experiments. Recent data suggest that SA-biotin bonds show strong directional dependence and a broad range of multi-exponential lifetimes under load. Here, we investigate engineered SA variants with different valencies and a unique tethering point under constant forces using a magnetic tweezers assay. We observed orders-of-magnitude differences in the lifetimes under force, which we attribute to the distinct force-loading geometries in the different SA variants. Lifetimes showed exponential dependencies on force, with extrapolated lifetimes at zero force that are similar for the different SA variants and agree with parameters determined from constant-speed dynamic SMFS experiments. We identified an especially long-lived tethering geometry that will facilitate ultra-stable SMFS experiments.

Vinculin is a universal adaptor protein that transiently reinforces the mechanical stability of adhesion complexes. It stabilizes mechanical connections that cells establish between the actomyosin cytoskeleton and the extracellular matrix via integrins or to neighboring cells via cadherins, yet little is known regarding its mechanical design. Vinculin binding sites (VBSs) from different nonhomologous actin-binding proteins use conserved helical motifs to associate with the vinculin head domain. We studied the mechanical stability of such complexes by pulling VBS peptides derived from talin, α-actinin, and Shigella IpaA out of the vinculin head domain. Experimental data from atomic force microscopy single-molecule force spectroscopy and steered molecular dynamics (SMD) simulations both revealed greater mechanical stability of the complex for shear-like than for zipper-like pulling configurations. This suggests that reinforcement occurs along preferential force directions, thus stabilizing those cytoskeletal filament architectures that result in shear-like pulling geometries. Large force-induced conformational changes in the vinculin head domain, as well as protein-specific fine-tuning of the VBS sequence, including sequence inversion, allow for an even more nuanced force response., Biophysical Journal, 118 (6), ISSN:0006-3495, ISSN:1542-0086

Single-molecule force spectroscopy has provided unprecedented insights into protein folding, force-regulation, and function. Here, we present a modular magnetic tweezers force spectroscopy approach that uses elastin-like polypeptide linkers to provide a high yield of protein tethers. Our approach extends protein force spectroscopy into the low force (2+, and discover transitions in the VWF C-domain stem at low forces that likely constitute the first steps of VWF activation in vivo. Our modular attachment approach will enable precise and multiplexed force spectroscopy measurements for a wide range of proteins in the physiologically relevant force regime.

A finite element model with slip-oxidation is proposed for solving intergranular stress corrosion cracking (IGSCC) with duplex oxides replicating the cyclic physics of the slip oxidation. The purpose is to investigate the crack growth effect due to different rate, compositions and kinetics of the duplex oxide. The finite element model is based on a coupling between cohesive zone formulation, slip-oxidation model and a diffusion model. The cohesive zone formulation includes a degradation formulation which is linked to the slip-oxidation formulation. The environmental properties in the slip-oxidation were obtained from the diffusion modeled with Fick's second law in one-dimension. This was then coupled to the structural model by a segregated solution scheme. The mesh of the cohesive zone adapts to the oxide thickness of the duplex oxide during the crack growth. The duplex oxide has the mathematical form of a power law or a logarithmic form. The model showed matching results for all duplex oxide combinations in varying stress, but the inner logarithmical oxide gave higher crack growth rates than the power law. The power law with the thicker inner oxide showed good results for the change of stress intensity factor and gave the best results when the yield stress was varied. Grain misorientation effect was higher for the duplex oxides with thicker outer oxides.

Most avidin-based handles in force spectroscopy are tetravalent biotin binders. Tetravalency presents two issues: multiple pulling geometries as well as multiple targets bound simultaneously. Additionally, such tetravalent handles require elaborate purification protocols in order to reassemble. A stoichiometric, monomeric variant of streptavidin (mcSA2) had been engineered previously. It is readily expressed and purified, and it binds biotin with a nanomolar KD. For atomic force microscopy-based single-molecule force spectroscopy (AFM-SMFS), we fused the monomeric streptavidin with a small protein domain as an experimental fingerprint and to improve solubility. A ybbR-tag was additionally included for covalent site-specific tethering. Rupture forces of the mcSA2:biotin complex were found to be in a comparable range above 150 pN at force loading rates of 1E4 pN/s as for previously published, tetravalent streptavidin:biotin systems. Additionally, when tethering mcSA2 from its C-terminus, rupture forces were found to be slightly higher than when tethered N-terminally. Due to its monomeric nature, mcSA2 could also be chemically denatured and subsequently refolded - and thus regenerated during an experiment, in case the handle gets misfolded or clogged. We show that mcSA2 features a straightforward expression and purification with flexible tags, high stability, regeneration possibilities and an unambiguous pulling geometry. Combined, these properties establish mcSA2 as a reliable handle for single-molecule force spectroscopy.

Discerning the timing and pattern of late Quaternary glacier variability in the tropical Andes is important for our understanding of global climate change. Terrestrial cosmogenic nuclide (TCN) ages (48) on moraines and radiocarbon-dated clastic sediment records from a moraine-dammed lake at Nevado Huaguruncho, Peru, document the waxing and waning of alpine glaciers in the Eastern Cordillera during the past ∼15 k.y. The integrated moraine and lake records indicate that ice advanced at 14.1 ± 0.4 ka, during the first half of the Antarctic Cold Reversal, and began retreating by 13.7 ± 0.4 ka. Ice retreated and paraglacial sedimentation declined until ca. 12 ka, when proxy indicators of glacigenic sediment increased sharply, heralding an ice advance that culminated in multiple moraine positions from 11.6 ± 0.2 ka to 10.3 ± 0.2 ka. Proxy indicators of glacigenic sediment input suggest oscillating ice extents from ca. 10 to 4 ka, and somewhat more extensive ice cover from 4 to 2 ka, followed by ice retreat. The lack of TCN ages from these intervals suggests that glaciers were less extensive than during the late Holocene. A final Holocene advance occurred during the Little Ice Age (LIA, ca. 0.4 to 0.2 ka) under colder and wetter conditions as documented in regional proxy archives. The pattern of glacier variability at Huaguruncho during the Late Glacial and Holocene is similar to the pattern of tropical Atlantic sea-surface temperatures, and provides evidence that prior to the LIA, ice extent in the eastern tropical Andes was decoupled from temperatures in the high-latitude North Atlantic.

A model is presented for the errors in small-angle X-ray scattering profiles that takes into account the physics of the measurement process. The model agrees quantitatively with the variations observed in experimental measurements and provides a straightforward prescription to add realistic errors to simulated scattering profiles., A new model is proposed for the measurement errors incurred in typical small-angle X-ray scattering (SAXS) experiments, which takes into account the setup geometry and physics of the measurement process. The model accurately captures the experimentally determined errors from a large range of synchrotron and in-house anode-based measurements. Its most general formulation gives for the variance of the buffer-subtracted SAXS intensity σ2(q) = [I(q) + const.]/(kq), where I(q) is the scattering intensity as a function of the momentum transfer q; k and const. are fitting parameters that are characteristic of the experimental setup. The model gives a concrete procedure for calculating realistic measurement errors for simulated SAXS profiles. In addition, the results provide guidelines for optimizing SAXS measurements, which are in line with established procedures for SAXS experiments, and enable a quantitative evaluation of measurement errors.

The widely used interaction of the homotetramer streptavidin with the small molecule biotin has been intensively studied by force spectroscopy and has become a model system for receptor ligand interaction. However, streptavidin's tetravalency results in diverse force propagation pathways through the different binding interfaces. This multiplicity gives rise to polydisperse force spectroscopy data. Here, we present an engineered monovalent streptavidin tetramer with a single cysteine in its functional subunit that allows for site-specific immobilization of the molecule, orthogonal to biotin binding. Functionality of streptavidin and its binding properties for biotin remain unaffected. We thus created a stable and reliable molecular anchor with a unique high-affinity binding site for biotinylated molecules or nanoparticles, which we expect to be useful for many single-molecule applications. To characterize the mechanical properties of the bond between biotin and our monovalent streptavidin, we performed force spectroscopy experiments using an atomic force microscope. We were able to conduct measurements at the single-molecule level with 1:1-stoichiometry and a well-defined geometry, in which force exclusively propagates through a single subunit of the streptavidin tetramer. For different force loading rates, we obtained narrow force distributions of the bond rupture forces ranging from 200 pN at 1,500 pN/s to 230 pN at 110,000 pN/s. The data are in very good agreement with the standard Bell-Evans model with a single potential barrier at Δx0 = 0.38 nm and a zero-force off-rate koff,0 in the 10-6 s-1 range.

Fission barrier height is one of the least known nuclear parameters, with experimental data, acquired decades ago, existing only close to beta-stability line. Availability of heavy radioactive beams offers possibility to investigate fission of more exotic nuclei and using the state of the art detection technique such as the active target we can even probe their fission barriers heights with precision has not been reached so far. The present status of fission barrier measurement is going to be explained in this paper. We are going to discuss the possibilities to stage experimental studies of fission barrier heights at new generation of ISOL facilities such as HIE-ISOLDE and active target ACTAR TPC. As an example we select the experiment IS581, being prepared for execution at the HIE-ISOLDE facility (CERN).

We demonstrate the use of a molybdenum-anode-based in-house small-angle X-ray scattering (SAXS) setup to study biological macromolecules in solution. Our system consists of a microfocus X-ray tube delivering a highly collimated flux of 2.5 × 10(6) photons/s at a beam size of 1.2 × 1.2 mm(2) at the collimation path exit and a maximum beam divergence of 0.16 mrad. The resulting observable scattering vectors q are in the range of 0.38 A(-1) down to 0.009 A(-1) in SAXS configuration and of 0.26 A(-1) up to 5.7 A(-1) in wide-angle X-ray scattering (WAXS) mode. To determine the capabilities of the instrument, we collected SAXS data on weakly scattering biological macromolecules including proteins and a nucleic acid sample with molecular weights varying from ∼12 to 69 kDa and concentrations of 1.5-24 mg/ml. The measured scattering data display a high signal-to-noise ratio up to q-values of ∼0.2 A(-1) allowing for an accurate structural characterization of the samples. Moreover, the in-house source data are of sufficient quality to perform ab initio 3D structure reconstructions that are in excellent agreement with the available crystallographic structures. In addition, measurements for the detergent decyl-maltoside show that the setup can be used to determine the size, shape, and interactions (as characterized by the second virial coefficient) of detergent micelles. This demonstrates that the use of a Mo-anode based in-house source is sufficient to determine basic geometric parameters and 3D shapes of biomolecules and presents a viable alternative to valuable beam time at third generation synchrotron sources.

Nano letters 16(8), 4871 - 4879(2016). doi:10.1021/acs.nanolett.6b01338, Self-assembled DNA origami nanostructures enable the creation of precisely defined shapes at the molecular scale. Dynamic DNA devices that are capable of switching between defined conformations could afford completely novel functionalities for diagnostic, therapeutic, or engineering applications. Developing such objects benefits strongly from experimental feedback about conformational changes and 3D structures, ideally in solution, free of potential biases from surface attachment or labeling. Here, we demonstrate that small-angle X-ray scattering (SAXS) can quantitatively resolve the conformational changes of a DNA origami two-state switch device as a function of the ionic strength of the solution. In addition, we show how SAXS data allow for refinement of the predicted idealized three-dimensional structure of the DNA object using a normal mode approach based on an elastic network model. The results reveal deviations from the idealized design geometries that are otherwise difficult to resolve. Our results establish SAXS as a powerful tool to investigate conformational changes and solution structures of DNA origami and we anticipate our methodology to be broadly applicable to increasingly complex DNA and RNA devices., Published by ACS Publ., Washington, DC

Commercially viable manufacturing of cellulosic ethanol requires high titers of product from both hexose and pentose fermentation. This article reports inhibition of initial specific xylose consumption rates and ethanol generation in batch fermentations of xylose using S. cerevisiae 424A (LNH-ST), a genetically modified strain capable of co-fermenting glucose and xylose. The fermentations were carried out in yeast extract peptone (YEP) medium in the presence of varying concentrations of ethanol (0% to 9% w/v) either added in a single dose or generated in situ by the yeast from glucose prior to xylose fermentation. The Levenspiel inhibition function was used to model inhibition of initial specific xylose consumption rates by ethanol. When ethanol was added in a single dose, the yeast ceased xylose fermentation when ethanol concentration reached 90 g L-1. However, when ethanol was generated in situ from glucose, the maximum final titer of ethanol was 110 g L-1. Comparing the effect of ethanol on xylose fermentation to the effect of ethanol on HXT transport of xylose in non-xylose-fermenting yeast suggests that inhibition of xylose transport into the cell is rate-limiting for fermentation.

Exercise is an important treatment for diabetes. In our study, we evaluated the acceptance of an exercise program and investigated the long-term effects of exercise on metabolic control and body mass index in older, insulin-treated type 2-diabetic patients.A total of 72 type 2 diabetic patients, agedor=50 years, participated in an exercise program. At the beginning of the study and after 3 and 12 months, patients completed a questionnaire concerning current activity. Finally, the patients were divided into two groups: those with and without regular exercise. Metabolic control was compared in both groups.Even during the first workout, blood glucose levels fell. No patient suffered from severe hypoglycemia. Motivation for regular exercise increased from 33 to 77%, decreasing slightly to 65% at 12 months. The mean HbA 1c levels were similar in both groups. However, in the exercise group no weight gain was observed in contrast to 2.5% weight gain in the other group. Moreover, insulin requirements were considerably lower in the exercise group.The acceptance of regular exercise is also high in older patients with newly insulin-treated type 2 diabetes. Metabolic control was significantly improved in patients with and without regular exercise; however, in the exercise group, body weight did not increase and insulin requirements were significantly lower.

Thermal contact resistance (TCR) plays an important role in the heat transfer during injection molding. However, there is no consensus on the magnitude of TCR to be used in simulation as most of the reported results are based on steady state experiments. A numerical simulation of the heat transfer in injection molding is used in studying its effect and significance. The TCR is shown to attain its maximum magnitude in the postfilling period, and more accurate values than those available in literature are required for a better simulation of the postfilling stage. The effect of interface gap formation between the plastic and the mold on the contact resistance is also studied. This shows that the gap may have contributed to the high magnitude of TCR reported from the one experimental study of TCR in injection molding. However, the gap formation is shown to be dependent on the part geometry as well as processing conditions—in terms of shrinkage and warpage effects. The gap is both a function of time and space (location on the part surface) and this makes any experimental determination of the gap and TCR difficult. [S1087-1357(00)01404-0]

A 3G network is a magnificently complex object embedded in a highly heterogeneous and ever-changing usage environment. It combines the functional complexity of the wireless cellular paradigm with the protocol dynamics of TCP/IP networks. Understanding such an environment is more urgent and at the same time more difficult than for legacy 2G networks. Continuous traffic monitoring by means of an advanced system, coupled with routine expert-driven traffic analysis, provides an in-depth understanding of the status and performances of the network as well as of the statistical behaviour of the user population. Such knowledge allows for a better engineering and operation practice of the whole network, and specifically the early detection of hidden risks and emerging troubles. Furthermore, the exploitation of certain TCP/IP dynamic behaviour, particularly the TCP control-loop, coupled with information extracted from the 3GPP layers, provides a cost-effective means to monitor the status of the whole network without requiring access to all network elements. In this article the main lessons are summarized learned from a two-year research activity on traffic monitoring and analysis on top of an operational 3G network.

This report is a progress report by the Generator Subcommittee of the Electrical Machinery Committee of the IEEE Power and Energy Society, Working Group No. 8 (“IEEE C50.13 Review & Compare”). The working group is comparing the 2005 revision of the IEEE C50.13 standard for large round rotor synchronous generators with recent revisions of comparable International Electrotechnical Commission (IEC) 60034 standards. In this paper the working group reports progress made since starting in 2007, summarizes completed results, and outlines plans for next steps. Included are highlights of an incrementally improved C50.13 that is to be submitted for balloting in 2013 and highlights of future improvements that will be pursued after 2013. Also included is a synopsis of suggestions provided to the IEC for harmonization of IEC 60034 with IEEE C50.13. Finally, the paper includes an overview of a 2012 PES panel session to discuss grid code impacts on electric machine design and performance.

Objecives: The clinical and histological diagnosis (gold standard) of diabetic nephropathy (dNP) and vascular nephropathy (vNP) were compared in type 2 diabetic patients with end-stage renal disease (ESRD). Aim: The aim of the study was to investigate indication for renal biopsy in type 2 diabetic patients with renal disease. Design: Retrospective study in diabetic patients with clinical and histological diagnosis of renal disease. Patients and methods: Eighty-four patients with type 2 diabetes and ESRD were investigated. Histological findings of the kidneys were available in all patients, 14 had undergone a renal biopsy before their first dialysis while a post-mortem kidney investigation was performed in 70 subjects. According to the histological findings, 66 patients had dNP and 18 subjects had vNP. The histological diagnosis was compared with the clinical diagnosis, and the sensitivity as well as the specificity of the clinical diagnosis of dNP and vNP were calculated. Results: The clinical diagnosis was not identical with the histological diagnosis in 10 cases. In the dNP group the diagnosis was 4 false positive and 3 false negative as in the vNP group 1 false positive and 2 false negative. The sensitivity of clinical diagnosis was 95% for dNP and 89% for vNP. Specificity was 78% for dNP and 97% for vNP. Conclusion: The sensitivity of the clinical diagnosis is very high for dNP as well as vNP. A renal biopsy is not required in the majority of type 2 diabetic patients with ESRD, especially in patients who exhibit all criteria for clinical diagnosis.

This report is an annual progress report by the Generator Subcommittee of the Electrical Machinery Committee of the IEEE Power and Energy Society, Working Group No. 8 (“IEEE C50.13 Review & Compare”). This working group is tasked to compare the 2005 revision of the IEEE C50.13 standard for large round rotor synchronous generators with recent revisions of comparable International Electrotechnical Commission (IEC) 60034 standards. The intention of this paper is to report the progress this working group had made, highlight some significant comparison findings, outline the next step planning of this project and call for more industry support.

Ethanol is an effective, environmentally friendly, nonfossil, transportation biofuel that produces far less pollution than gasoline. Furthermore, ethanol can be produced from plentiful, domestically available, renewable, cellulosic biomass. However, cellulosic biomass contains two major sugars, glucose and xylose, and a major obstacle in this process is that Saccharomyces yeasts, traditionally used and still the only microorganisms currently used for large scale industrial production of ethanol from glucose, are unable to ferment xylose to ethanol. This makes the use of these safest, most effective Saccharomyces yeasts for conversion of biomass to ethanol economically unfeasible. Since 1980, scientists worldwide have actively been trying to develop genetically engineered Saccharomyces yeasts to ferment xylose. In 1993, we achieved a historic breakthrough to succeed in the development of the first genetically engineered Saccharomyces yeasts that can effectively ferment both glucose and xylose to ethanol. This was accomplished by carefully redesigning the yeast metabolic pathway for fermenting xylose to ethanol, including cloning three xylose-metabolizing genes, modifying the genetic systems controlling gene expression, changing the dynamics of the carbon flow, etc. As a result, our recombinant yeasts not only can effectively ferment both glucose and xylose to ethanol when these sugars are present separately in the medium, but also can effectively coferment both glucose and xylose present in the same medium simultaneously to ethanol. This has made it possible because we have genetically engineered the Saccharomyces yeasts as such that they are able to overcome some of the natural barrier present in all microorganisms, such as the synthesis of the xylose metabolizing enzymes not to be affected by the presence of glucose and by the absence of xylose in the medium. This first generation of genetically engineered glucose-xylose-cofermenting Saccharomyces yeasts relies on the presence of a high-copy-number 2 mu-based plasmid that contains the three cloned genetically modified xylose-metabolizing genes to provide the xylose-metabolizing capability. In 1995, we achieved another breakthrough by creating the super-stable genetically engineered glucose-xylose-cofermenting Saccharomyces yeasts which contain multiple copies of the same three xylose-metabolizing genes stably integrated on the yeast chromosome. This is another critical development which has made it possible for the genetically engineered yeasts to be effective for cofermenting glucose and xylose by continuous fermentation. It is widely believed that the successful development of the stable glucose-xylose-cofermenting Saccharomyces yeasts has made the biomass-to-ethanol technology a step much closer to commercialization. In this paper, we present an overview of our rationales and strategies as well as our methods and approaches that led to the ingenious design and successful development of our genetically engineered Saccharomyces yeasts for effective cofermentation of glucose and xylose to biofuel ethanol.

We analyzed 128 cardiopulmonary exercise tests (CPX), performed in normal subjects (n = 31), in patients with coronary artery disease (n = 41), with chronic heart failure before (n = 14) and after (n = 14) application of oral PDE-inhibitors and in patients with HIV-infection on a bicycle-ergometer in semi-supine position using a ramp-program (dependent on study-population with 15, 20 or 35 Watt/min increases) with respect to the ability to determine the respiratory anaerobic threshold non-invasively, using the main criteria described by Wasserman et al.: the V-slope-method according to Beaver, the increase of the ventilatory equivalent for O2 (VE/VO2), the increase of the end-tidal PO2 (PETO2) and the increase of the respiratory quotient (RQ) during exercise. In the different study-populations we calculated the detection rates of the AT for each criteria separately. The typical changes in the end-tidal PO2 (124/128 = 96.9%) and the V-slope-method (119/128 = 92.9%) were the most reliable parameters to detect the anaerobic threshold. The characteristic changes of the ventilatory equivalent for O2 (VE/VO2) and of the respiratory quotient (RQ) we found in 100/128 (= 78.1%) and in 107/128 (= 83.6%) of the tests respectively. 86/128 tests (67.2%) showed typical changes in all four mentioned criteria. In another 24/128 tests (19.8%) three of four criteria were fulfilled. Therefore, our investigations showed that in 110/128 cases (85.9%) the AT could be determined by typical changes by means of at least three of the four described parameters. In 15/128 (11.7%) tests only two of four criteria were fulfilled.(ABSTRACT TRUNCATED AT 250 WORDS)

The O2-uptake at the anaerobic threshold ( \(\dot V\) O2 AT), as detected by gas exchange measurements during an incremental exercise test on a semi-supine bicycle, is an objective parameter for the estimation of cardiopulmonary exercise capacity. It was used to assess the severity of cardiopulmonary and cardiovasculary diseases in patients with coronary heart disease (CAD, N = 22, mean age 54.05 ± 7.88 years) and chronic heart failure (CHF, n = 15, mean age 57.73 ± 12.61 years). According to \(\dot V\) O2 AT, we found a high distinction between the subjective and the objective evaluation of exercise capacity, using the Weber- and the NYHA-classes. The NYHA-classes provide insufficient criteria for exercise capacity (i.e. 14 CAD-patients NYHA II were individually assigned to very different Weber-classes: 2/14 Weber A, 2/14 Weber B, 4/14 Weber C, 5/14 Weber D, 1/14 Weber E). Our investigations showed that the O2-uptake of every pedaled watt (Δ \(\dot V\) O2/ΔWR) should be a parameter to estimate the exercise capacity, but seems to be very insufficient in patients with severe heart failure and low values of maximum work rate (WR). Oscillations of the respiratory variables during rest, exercise, and recovery were reported in 4/22 CAD-patients (18.2%) and in 9/15 CHF-patients (60%). A constant value for O2-pulse, the O2-uptake of every heart beat ( \(\dot V\) O2/HR), was reached in 10/ 22 CAD-patients (45.5%) and in 8/15 CHF-patients (53.3%). The computerized ergospirometry is a feasible, secure, accurate, and well-tolerated method to objectively evaluate the functional disability of patients with CAD of CHF. The present study offers new insights in the evaluation of critically ill patients using non-invasive procedures.

The kinetics of dehydration of amorphous calcium phosphate (ACP) has been studied by the temperature programmed desorption technique (TPD) of Cvetanovic and Amenomiya. Each water desorption spectrum for ACP exhibited a single, but fairly narrow, peak. Peak temperatures varied from 65–100°C for sample heating rates ranging from 3–32°C/min. Narrowness of the desorption spectra lends some support to its earlier characterization as an agglomerate of hydrated Ca 2+ and PO 4 3− ions. In contrast, a water desorption spectrum for crystalline hydroxyapatite (HA) showed several broad overlapping peaks with maxima at 120, 250, and 305°C which is typical of a heterogeneous surface. The desorption spectra for ACP when compared to those for HA indicate very different states of bound water in these two substances. Plotted kinetic data for ACP revealed two linear segments with different activation energies, namely 10.5 and 20.0 kcal/mole. A plausible explanation for this finding is that there are two types of bound water in ACP: (i) loosely held water and (ii) tightly bound hydrate water held inside the amorphous particles. The possibility that hydrate water loss is involved in the rate determining step in the in vitro conversion of ACP to HA is tentatively suggested.

A study of the dehydration kinetics of a model system, cupric sulfate pentahydrate, was made using the temperature programmed desorption technique. The three decomposition steps from the pentahydrate to the anhydrous salt were clearly resolved into distinct spectral peaks even at sample heating rates in excess of 10 K. min −1 . A linear relationship between spectral peak temperature and square root of heating rate was observed for each dehydration step. The kinetic data revealed different activation enthalpies and entropies for each dehydration sequence for heating rates above and below approximately 8 K min −1 . These latter findings are interpreted in terms of crystalline to amorphous pseudo-phase changes in the solid hydrate during decomposition which become apparent only at fast sample heating rates. Enthalpy and entropy changes associated with these structural alterations are evaluated. The results also help to clarify earlier work on the dehydration mechanism in calcium phosphates.

A new method for the quantitative analysis of sub-ppm and high ppm levels of hydrogen sulphide is reported. The technique is based on the electrochemieal oxidation of hydrogen sulphide at a potentiostatically-controlled. Teflon-bonded diffusion electrode. Two instruments (one portable and one a fixed-location instrument) were constructed and their operating characteristics evaluated. They were sensitive and selective, responded rapidly to the gas. and gave a linear relationship between steady-state signal and gas concentration. Excellent zero and signal stability indicate that the electrochemical sensor is not poisoned by the H2S.