Tracking dynamic structural changes in catalysis by rapid 2D-XANES microscopy

Many processes and materials in heterogeneous catalysis undergo dynamic structural changes depending on their chemical environment. Monitoring such dynamic changes can be challenging using conventional spectroscopic characterization tools, due to the high time resolution required. Here, a high-resolution 2D X-ray camera operating at 50 Hz full-frame rate was synchronized with a QEXAFS monochromator, enabling rapid spectro-microscopic imaging with chemical contrast over individual pixels. This was used to monitor chemical gradients within a model Pt/Al2O3 catalyst during catalytic partial oxidation of methane to synthesis gas. The transition from methane combustion (partly oxidized Pt) to combustion-reforming and partial oxidation (fully reduced Pt) was observed by a characteristic reduction front, which progressed from the end of the catalyst bed towards its beginning on the second time scale. The full-field QEXAFS imaging method applied here allows acquisition of entire XANES spectra `on the fly' in a rapid and spatially resolved manner. The combination of high spatial and temporal resolution with spectroscopic data offers new opportunities for observing dynamic processes in catalysts and other functional materials at work. The methodology is flexible and can be applied at beamlines equipped with a QEXAFS or other fast-scanning monochromators and a suitable sample environment for gas phase analytics to allow for catalytic studies at the same time.

Tomographic reconstruction with a generative adversarial network

This paper presents a deep learning algorithm for tomographic reconstruction (GANrec). The algorithm uses a generative adversarial network (GAN) to solve the inverse of the Radon transform directly. It works for independent sinograms without additional training steps. The GAN has been developed to fit the input sinogram with the model sinogram generated from the predicted reconstruction. Good quality reconstructions can be obtained during the minimization of the fitting errors. The reconstruction is a self-training procedure based on the physics model, instead of on training data. The algorithm showed significant improvements in the reconstruction accuracy, especially for missing-wedge tomography acquired at less than 180° rotational range. It was also validated by reconstructing a missing-wedge X-ray ptychographic tomography (PXCT) data set of a macroporous zeolite particle, for which only 51 projections over 70° could be collected. The GANrec recovered the 3D pore structure with reasonable quality for further analysis. This reconstruction concept can work universally for most of the ill-posed inverse problems if the forward model is well defined, such as phase retrieval of in-line phase-contrast imaging.

A versatile nanoreactor for complementary in situ X-ray and electron microscopy studies in catalysis and materials science

Two in situ `nanoreactors' for high-resolution imaging of catalysts have been designed and applied at the hard X-ray nanoprobe endstation at beamline P06 of the PETRA III synchrotron radiation source. The reactors house samples supported on commercial MEMS chips, and were applied for complementary hard X-ray ptychography (23 nm spatial resolution) and transmission electron microscopy, with additional X-ray fluorescence measurements. The reactors allow pressures of 100 kPa and temperatures of up to 1573 K, offering a wide range of conditions relevant for catalysis. Ptychographic tomography was demonstrated at limited tilting angles of at least ±35° within the reactors and ±65° on the naked sample holders. Two case studies were selected to demonstrate the functionality of the reactors: (i) annealing of hierarchical nanoporous gold up to 923 K under inert He environment and (ii) acquisition of a ptychographic projection series at ±35° of a hierarchically structured macroporous zeolite sample under ambient conditions. The reactors are shown to be a flexible and modular platform for in situ studies in catalysis and materials science which may be adapted for a range of sample and experiment types, opening new characterization pathways in correlative multimodal in situ analysis of functional materials at work. The cells will presently be made available for all interested users of beamline P06 at PETRA III.

The efficacy of thermocoagulation of the tibial nerve and a polypropylene ankle-foot orthosis on spasticity of the leg in stroke patients: results of a randomized clinical trial

Objective: To investigate the efficacy of thermocoagulation of the tibial nerve and a polypropylene ankle-foot orthosis (AFO) on spasticity of the leg in stroke patients with a spastic equinus or equinovarus foot.

Design: A placebo-controlled randomized clinical trial with a 2 x 2 factorial design.

Setting: Outpatient clinic, Department of Rehabilitation Medicine, Academisch Ziekenhuis Vrije Universiteit Amsterdam.

Subjects: 60 stroke patients (17 women, 43 men), with a median age of 58 years and a median period of 34 months poststroke, with at least independent walking capacities at home.

Main outcome measures: Change in spasticity, muscle tone, ankle clonus, Achilles tendon reflex, ankle range of motion (ROM), motor function of the leg, and balance, measured six and 15 weeks after randomization.

Results: Thermocoagulation, rather than the AFO, reduced spasticity, muscle tone, Achilles tendon hyperexcitability, and ankle clonus. At six-week follow- up, the effects on Achilles tendon reflex and ankle clonus were the most pronounced; reflex excitability was reduced in 59% of the patients treated with thermocoagulation, as compared to 14% of the placebo-treated patients, whereas ankle clonus was reduced in 55% and 0% of the patients, respectively. Reduced spasticity was found in 35% of the actively treated, as compared to 10% of the placebo-treated patients. For muscle tone, the percentages of improved patients in each group were 45% and 24%, respectively. After 15 weeks the differences between the groups were smaller. No clinically relevant improvement was found with regard to ROM, the Fugl-Meyer lower extremity and balance scores, walking ability and walking speed.

Conclusion: Thermocoagulation is effective for the reduction of spasticity in stroke patients with a spastic equinus or equinovarus foot. No effect on spasticity of the AFO could be demonstrated. When the efficacy of thermocoagulation and the AFO are judged in terms of functional abilities, however, the effects seem of little value.

Chondroitin sulfate and sulfated hyaluronan-containing collagen coatings of titanium implants influence peri-implant bone formation in a minipig model

An improved osseous integration of dental implants in patients with lower bone quality is of particular interest. The aim of this study was to evaluate the effect of artificial extracellular matrix implant coatings on early bone formation. The coatings contained collagen (coll) in conjunction with either chondroitin sulfate (CS) or sulfated hyaluronan (sHya). Thirty-six screw-type, grit-blasted, and acid-etched titanium implants were inserted in the mandible of 6 minipigs. Three surface states were tested: (1) uncoated control (2) coll/CS (3) coll/sHya. After healing periods of 4 and 8 weeks, bone implant contact (BIC), bone volume density (BVD) as well as osteoid related parameters were measured. After 4 weeks, control implants showed a BIC of 44% which was comparable to coll/CS coated implants (48%) and significantly higher compared to coll/sHya coatings (37%, p = 0.012). This difference leveled out after 8 weeks. No significant differences could be detected for BVD values after 4 weeks and all surfaces showed reduced BVD values after 8 weeks. However, at that time, BVD around both, coll/CS (30%, p = 0.029), and coll/sHya (32%, p = 0.015), coatings was significantly higher compared to controls (22%). The osteoid implant contact (OIC) showed no significant differences after 4 weeks. After 8 weeks OIC for controls was comparable to coll/CS, the latter being significantly higher compared to coll/sHya (0.9% vs. 0.4%, p = 0.012). There were no significant differences in osteoid volume density. In summary, implant surface coatings by the chosen organic components of the extracellular matrix showed a certain potential to influence osseointegration in vivo.

[Is family history dispensable?]

As an element of risk assessment in applications for life insurance, family medical history has a particular significance since given impairments can occur more frequently within families. Family history is not only genetic in nature. Depending on the impairment, it is also explained by external factors. There has been little literature on this topic so far, although the spectrum of family history-related impairments is very large, and their effect is highly dependent on the type of product. This paper presents a new method for assessing the effects of information contained in family history on claims, based on typical age patterns for German life insurance products (life, disability and long term care insurance), using the example of breast cancer and schizophrenia. This method helps life insurers to better understand what impact questions on family history during the stage of application have on the risk. Thus, the study contributes to the often discussed question on how essential questions on family history are.

[Decision analysis--a novel approach for calculating the cost-efficiency of medical tests]

Before issuing an insurance policy (e.g. life, disability, critical illness), insurers will usually carry out a medical risk assessment in order to prevent adverse selection. Often, the health questions in the application form will not be sufficient for this purpose since most applicants are not well-versed in medical science and terminology. If the insurer needs additional medical information such as a private medical attendant's report or current laboratory tests, however, costs will be incurred, which usually have to be paid by the insurer. What is the minimum sum insured which makes it worthwhile for the insurer to conduct certain screening tests, for example? Both the costs of medical screening and the associated savings are difficult to measure and involve a variety of different factors. Moreover, most parameters can only be estimated with limited accuracy. Therefore, we have developed a new calculation model using a decision-analysis approach. The new model makes it possible to analyse complex situations while taking into account the uncertainty of parameter estimation. Our findings show that in Germany, for instance, current sum thresholds for older applicants could in many cases be lowered and would still be cost-effective.

Binding Studies between Tetrathiafulvalene Derivatives and Cyclobis(paraquat-p-phenylene)

The complexation between a number of different pi-electron donating TTF derivatives and the pi-electron accepting tetracationic cyclophane cyclobis(paraquat-p-phenylene) (CBPQT(4+)) has been studied by (1)H NMR and UV-vis spectroscopy. The results demonstrate that the strength of association between the donors (TTF derivatives) and acceptor (CBPQT(4+)) is strongly dependent on the pi-electron donating properties (measured by the first redox potential ) of the TTF derivatives. However, the first redox potential () is not the only factor of importance. The extended pi-surface of the TTF derivatives also exerts a stabilizing influence upon complexation. The kinetics for the complexation-decomplexation were studied using (1)H NMR spectroscopy and are related to the bulkiness of the TTF derivatives. These effects may serve to improve the design of interlocked molecular systems, especially (bistable) molecular switches, in which CBPQT(4+) and a derivatized TTF unit are incorporated.

[Significance of medical statistics in insurance medicine]

Knowledge of medical statistics is of great benefit to every insurance medical officer as they facilitate communication with actuaries, allow officers to make their own calculations and are the basis for correctly interpreting medical journals. Only about 20% of original work in medicine today is published without statistics or only with descriptive statistics--and this trend is falling. The reader of medical publications should be in a position to make a critical analysis of the methodology and content, since one cannot always rely on the conclusions drawn by the authors: statistical errors appear very frequently in medical publications. Due to the specific methodological features involved, the assessment of meta-analyses demands special attention. The number of published meta-analyses has risen 40-fold over the last ten years. Important examples for the practical use of statistical methods in insurance medicine include estimating extramortality from published survival analyses and evaluating diagnostic test results. The purpose of this article is to highlight statistical problems and issues of relevance to insurance medicine and to establish the bases for understanding them.

Tetrathiafulvalene crowns: redox-switchable ligands

A series of redox-responsive ligands that associate the electroactive tetrathiafulvalene core with polyether subunits of various lengths has been synthesized. X-ray structures are provided for each of the free ligands. The requisite structural criteria for reaching switchable ligands are satisfied for the largest macrocycles, that is, planarity of the 1,1',3,3'-tetrathiafulvalene (TTF) pi system and correctly oriented coordinating atoms. The ability of these ligands to recognize various metal cations as a function of the cavity size has been investigated by various techniques (LSIMS, 1H NMR, and UV/Vis spectroscopy, cyclic voltammetry). These systems exhibit an unprecedented high coordination ability among TTF crown ethers. Their switchable ligating properties have been confirmed by cyclic voltammetry, and metal-cation complexation has been illustrated by X-ray structures of three of the corresponding metal complexes (Pb2+, Sr2+, and Ba2+). Solid-state structures of these complexes display original packing modes with channel-like arrangements.

Resummation of QED perturbation series by sequence transformations and the prediction of perturbative coefficients

We propose a method for the resummation of divergent perturbative expansions in quantum electrodynamics and related field theories. The method is based on a nonlinear sequence transformation and uses as input data only the numerical values of a finite number of perturbative coefficients. The results obtained in this way are for alternating series superior to those obtained using Pade approximants. The nonlinear sequence transformation fulfills an accuracy-through-order relation and can be used to predict perturbative coefficients. In many cases, these predictions are closer to available analytic results than predictions obtained using the Pade method.

A flexible cyclophane: design, synthesis, and structure of a multibridged tris-tetrathiafulvalene (TTF) macrocycle

The tris-tetrathiafulvalene (TTF) macrocycles 3 with a large end-cavity were effectively synthesized from the readily available tetrakis(cyanoethylthio)TTF by means of a selective deprotection/realkylation sequence followed by an intramolecular coupling reaction. Crystar structure analyses revealed that the neutral molecules include two (3a) or one chloroform molecule (3b) as solvent of crystallization inside the cavity, whereas the I3- salt of 3b, obtained by electrocrystallization, has a molecular structure which is different from that of the neutral molecule in that the cavity has completely collapsed.

Outbreak of type A botulism and development of a botulism surveillance and antitoxin release system in Argentina

CONTEXT

Botulism is an important public health problem in Argentina, but obtaining antitoxin rapidly has been difficult because global supplies are limited. In January 1998, a botulism outbreak occurred in Buenos Aires.

OBJECTIVES

To determine the source of the outbreak, improve botulism surveillance, and establish an antitoxin supply and release system in Argentina.

DESIGN, SETTING, AND PARTICIPANTS

Cohort study in January 1998 of 21 drivers of a specific bus route in urban Buenos Aires.

MAIN OUTCOME MEASURE

Occurrence of botulism and implication of a particular food as the vehicle causing this outbreak.

RESULTS

Nine (43%) of 21 bus drivers developed botulism, presenting with gastroenteritis, symptoms of acute cranial nerve dysfunction including ptosis, dysphagia, blurred vision, and motor weakness. One driver experienced respiratory failure. Type A toxin was detected from 3 of 9 patients' serum samples. All drivers received botulism antitoxin; there were no fatalities. Consumption of matambre (Argentine meat roll) was significantly associated with illness. Among 11 persons who ate matambre, 9 developed illness, compared with none of those who did not eat it (P<.001). The matambre had been cooked in water at 78 degrees C to 80 degrees C for 4 hours, sealed in heat-shrinked plastic wrap, and stored in refrigerators that did not cool adequately. Subsequently, a botulism surveillance and antitoxin release system was established.

CONCLUSIONS

Insufficient cooking time and temperatures, storage in heat-shrinked plastic wrap, and inadequate refrigeration likely contributed to Clostridium botulinum spore survival, germination, and toxin production. A rapid-response botulism surveillance and antitoxin release system in Argentina should provide more timely distribution of antitoxin to patients and may serve as a model for other nations.

Interobserver variability among faculty in evaluations of residents' clinical skills

OBJECTIVE

To describe interobserver variability among emergency medicine (EM) faculty when using global assessment (GA) rating scales and performance-based criterion (PBC) checklists to evaluate EM residents' clinical skills during standardized patient (SP) encounters.

METHODS

Six EM residents were videotaped during encounters with SPs and subsequently evaluated by 38 EM faculty at four EM residency sites. There were two encounters in which a single SP presented with headache, two in which a second SP presented with chest pain, and two in which a third SP presented with abdominal pain, resulting in two parallel sets of three. Faculty used GA rating scales to evaluate history taking, physical examination, and interpersonal skills for the initial set of three cases. Each encounter in the second set was evaluated with complaint-specific PBC checklists developed by SAEM's National Consensus Group on Clinical Skills Task Force.

RESULTS

Standard deviations, computed for each score distribution, were generally similar across evaluation methods. None of the distributions deviated significantly from that of a Gaussian distribution, as indicated by the Kolmogorov-Smirnov goodness-of-fit test. On PBC checklists, 80% agreement among faculty observers was found for 74% of chest pain, 45% of headache, and 30% of abdominal pain items.

CONCLUSIONS

When EM faculty evaluate clinical performance of EM residents during videotaped SP encounters, interobserver variabilities are similar, whether a PBC checklist or a GA rating scale is used.

Reliability of performance-based clinical skill assessment of emergency medicine residents

OBJECTIVE

To test the overall reliability of a performance-based clinical skill assessment for entering emergency medicine (EM) residents. Also, to investigate the reliability of separate reporting of diagnostic and management scores for a standardized patient case, subjective scoring of patient notes, and interstation exercise scores.

METHODS

Thirty-four first-year EM residents were tested using a 10-station standardized patient (SP) examination. Following each 10-minute encounter, the residents completed a patient note that included differential diagnosis and management. The residents also were asked to read an ECG or chest x-ray (CXR) associated with each case. History, physical examination, and interpersonal skills were scored by the SPs. The patient note, CXR, and ECG readings were scored by faculty emergency physicians. Intercase reliability was determined for the residents.

RESULTS

Global score reliability, Cronbach's alpha = 0.85. Reliabilities for the other components were: history, 0.77; physical examination, 0.83; and interpersonal skills, 0.80. Differential diagnosis and management reliabilities were 0.61 and 0.66, respectively. Subjective scoring of the patient note resulted in acceptable reliability for legibility (0.80), history completeness (0.80), and history organization (0.81). Physical examination completeness and organization reliabilities were 0.74 and 0.73. For ECG and CXR readings, alpha = 0.74 and 0.34, respectively.

CONCLUSIONS

SPs can be used to reliably assess bedside clinical skills of EM residents. While component reliability levels are slightly lower than the global clinical skill reliability coefficient, they are still high enough to use for identification of individual strengths and weaknesses.

Walking ability of stroke patients: efficacy of tibial nerve blocking and a polypropylene ankle-foot orthosis

OBJECTIVE

To investigate the efficacy of tibial nerve blocking by percutaneous radiofrequency thermocoagulation and an ankle-foot orthosis on the walking ability of stroke patients with a spastic equinus or equinovarus foot.

DESIGN

A placebo-controlled randomized clinical trial with a 2 x 2 factorial design and with a 3-month follow-up.

SETTING

Outpatient clinic of a department of rehabilitation medicine.

SUBJECTS

Sixty stroke patients (17 women, 43 men) with a median age of 58 years and a median period of 34 months poststroke were allocated to one of four treatment groups.

MAIN OUTCOME MEASURES

Changes in walking ability (measured with the Sickness Impact Profile category "ambulation"; possible score range, 0% to 100%) and walking speed after 3 months.

RESULTS

With respect to walking ability, the efficacy of thermocoagulation as compared with placebo thermocoagulation was .56% (95% confidence interval [CI] -3.01% to 4.13%), whereas the efficacy of the ankle-foot orthosis as compared with the placebo ankle-foot orthosis was 2.72% (95% CI -.94% to 6.38%). To study the potential synergistic effect of both treatments, a multivariate model was used; interaction between both treatments was small, .83% (95% CI -6.73% to 8.40%). Analysis restricted to the compliers (n = 30) showed an increased efficacy of thermocoagulation and a decreased efficacy of the ankle-foot orthosis. The changes in comfortable and maximal safe walking speed were less than .10m/sec and were neither clinically nor statistically significant (the median baseline values for the total group were .42m/sec and .56m/sec, respectively).

CONCLUSION

No support was found for the beneficial effects of either thermocoagulation of the tibial nerve or a polypropylene ankle-foot orthosis in 5 degrees of dorsiflexion on the walking ability of stroke patients.

Treatment of ectoparasitic infections: review of the English-language literature, 1982-1992

We reviewed the English-language literature of 1982-1992 for papers concerning scabies, pediculosis, and their treatments; this information was supplemented with opinions of workers in the field of ectoparasitic disease. Six treatment trials for scabies, one study of the treatment of pediculosis pubis, and additional studies on the treatment of pediculosis capitis were included. Both lindane 1% and permethrin 5% are effective treatments for scabies, although resistance to lindane does exist. Lindane 1%, permethrin 1%, and pyrethrins with piperonyl butoxide are all effective treatments for pediculosis. Severe reactions to lindane therapy may occur when increased skin absorption of lindane occurs. Permethrin 5% or lindane 1% is recommended for the treatment of scabies. Lindane should be used with precautions to avoid excess skin penetration and should not be used to treat infants, young children, or pregnant or lactating women. Permethrin 1%, lindane 1%, or pyrethrins with piperonyl butoxide is recommended for the treatment of pediculosis pubis. Pregnant and lactating women should be treated with either permethrin or with pyrethrins containing piperonyl butoxide.

The effectiveness of vibratory stimulation in anejaculatory men with spinal cord injury. Review article

Most spinal cord injury (SCI) men have fertility problems caused by anejaculation and a decreased fertility of the ejaculate. There are several methods to induce ejaculation, such as vibratory stimulation and transrectal electrostimulation. In order to investigate the current state of knowledge about the effectiveness of vibratory stimulation and to prepare a controlled clinical trial we reviewed the available literature. Ten articles met our inclusion criteria. Articles were found by various strategies, such as computer searches and screening of relevant journals. We used a structured approach to evaluate these articles. In total 428 patients had been treated with vibration. Sixty percent (257) of the patients responded to treatment, ie produced ejaculate. Because of methodological shortcomings in most studies it remains unclear whether there is a relationship between injury type, such as level and completeness of the injury, and the response rate. Semen analyses showed a large intersubject variation. From the data available, it could be concluded that the semen volume is usually normal, whereas sperm motility and morphology of spermatozoa were in most cases far from normal. Side effects of vibratory stimulation were reported in 6% of the patients. Semen could be used for various (assisted) reproductive technologies, eg artificial insemination, in vitro fertilisation and microinsemination. Therefore, it is very important to know which stimulation method is most effective in treating anejaculatory SCI men. This review of the literature shows that the effectiveness of vibratory stimulation remains unclear. New, well designed clinical trials as well as basic research activities might clarify the effectiveness of vibratory stimulation and transrectal electrostimulation.