Cutaneous Cryptococcus Infection and Suspected Kaposi Sarcoma of the Hand in an Immunocompromised Patient.

Cryptococcal infection is well-documented in immunocompromised individuals. Cutaneous manifestations are not as common and are often difficult to diagnose due to variable presentations. Furthermore, there have been reports of coexisting cutaneous Cryptococcus and malignancy. We describe a patient that presented with a fast-growing mass (suspected sarcoma) in the hand that was ultimately treated for a Cryptococcus skin infection. We believe familiarity with the possibility of coexistence of these two conditions in an immunocompromised host could have brought about earlier diagnosis and possibly more effective treatment. Level of Evidence: Level V (Therapeutic).

Does Midcarpal Joint Structure Affect Development of Arthritis in the Wrist.

Background Degenerative wrist arthritis develops in specific patterns because of forces acting on existing structural configurations. The most common pattern of wrist osteoarthritis is scapholunate advanced collapse (SLAC). Other patterns include isolated scaphotrapezial trapezoid (STT) joint and isolated midcarpal or radiolunate joint arthritis. One predictor of degeneration pattern is the structure of the wrist. Questions/Purposes Our purpose was to evaluate the relationship between midcarpal joint structure and the pattern of degenerative arthritis. We hypothesized that a wrist type 2 will preferentially develop SLAC degeneration. Patients and Methods We retrospectively evaluated 195 degenerative wrist radiographs. Radiographs were reviewed for lunate/wrist type, degeneration pattern, ulnar variance, radial and volar tilt, inclination, carpal height, scapholunate angle, gap, and presence of thumb carpometacarpal (CMC) joint, STT joint, and midcarpal joint arthritis. Results We had 158 radiographs with SLAC degeneration and 37 with atypical patterns, 154 type 2 and 41 type 1 wrists. There was a significant correlation between wrist type and the pattern of wrist degeneration ( p = 0.02). SLAC degeneration developed in wrists with type 2 lunate while isolated midcarpal arthritis was associated with type 1 wrist. Isolated midcarpal joint arthritis was associated with STT arthritis, p < 0.01. Radial height, inclination, volar tilt, and ulnar variance, and scapholunate gap and angle were not associated with wrist type. Ulnar variance was associated with thumb CMC and STT joint arthritis while radial height was associated with isolated midcarpal joint arthritis. Conclusion This study found significant relationships between midcarpal joint structure and pattern of degeneration. This contributes to understanding the development of degeneration and can aid in future prevention of arthritis. Level of Evidence This is a Level IV, diagnostic study.

Are Orthopedic Hand Surgeons Undercompensated for Time Spent in the Operating Room? A Study of Relative Value Units.

BACKGROUND: This study aims to investigate whether compensation is equitable among the most commonly performed orthopedic hand surgeries and when compared with general orthopedic procedures. METHODS: The National Surgical Quality Improvement Program database was queried for all orthopedic procedures, from 2016 to 2018, performed more than 150 times using Current Procedural Terminology (CPT) codes. Physician work relative value unit (wRVU) data were obtained from the 2020 US Centers for Medicare and Medicaid Services fee schedule. Linear regressions were used to determine whether there was an association among wRVU, operative time, and wRVU per hour (wRVU/h). Reimbursement for hand surgery CPT codes was compared with that of nonhand orthopedic CPT codes. The CPT codes were stratified into quartile cohorts based on mean operative time, major complication rate, mortality rate, American Society of Anesthesiologists class, reoperation rate, and readmission rate. Student t tests were used to compare wRVU/h between cohorts. RESULTS: Forty-two hand CPT codes were identified from 214 orthopedic CPT codes, accounting for 32 333 hand procedures. The median wRVU/h was significantly lower for procedures in the longest operative time quartile compared with the shortest operative time quartile (P < .001). Compared with hand procedures, nonhand procedures were found to have significantly higher mean operative time (P < .001), mean complication rate (P < .001), mean wRVU (P = .001), and mean wRVU/h (P = .007). CONCLUSIONS: The 2020 Physician wRVU scale does not allocate proportional wRVUs to orthopedic hand procedures with longer mean operative times. There is a decrease in mean reimbursement rate for hand procedures with longer mean operative time. When compared with general orthopedic procedures, hand procedures have a lower mean wRVU/h and complication rate.

Wrist angle measurements in predicting the presence of a displaced scaphoid fracture.

PURPOSE: Early diagnosis and treatment of scaphoid fractures is critical to achieve union and prevent wrist degenerative arthritis. Plain radiographic measurements can guide the early approach to suspected fractures. Specifically, the ability to predict fracture or fracture stability from plain radiographs may allow the traumatologist to expand initial referral to three-dimensional imaging. We evaluated the ability of four measured angles to predict presence of a scaphoid fracture and stability. METHODS: Fifty patients with a scaphoid fracture and 50 patients without fracture were evaluated for the cortical ring sign, scapho-lunate gapping, lateral scapholunate (SL), radio-scaphoid (RS), radio-lunate (RL), and radio-capitate (RC) angles by two-blinded observers. RESULTS: Measurement of an increased SL interval was associated with the presence of a scaphoid fracture as diagnosed on three-dimensional imaging [odds ratio (OR) 3.0, confidence interval (CI) 1.53-5.87, p = < 0.01]. The measured RL angle was associated with fracture displacement (OR 1.13, 95% CI 1.02-1.25, p = 0.02). CONCLUSIONS: Scapholunate gapping on plain radiographs in the context of a clinically suspected scaphoid fracture should increase suspicion for a fracture and may prompt earlier 3-dimensional imaging, while the presence of an abnormal radiolunate angle should increase wariness for instability and can be used in preoperative planning.

Global trends in ozone concentration and attributable mortality for urban, peri-urban, and rural areas between 2000 and 2019: a modelling study.

BACKGROUND: Data on long-term trends of ozone exposure and attributable mortality across urban-rural catchment areas worldwide are scarce, especially for low-income and middle-income countries. This study aims to estimate trends in ozone concentrations and attributable mortality for urban-rural catchment areas worldwide. METHODS: In this modelling study, we used a health impact function to estimate ozone concentrations and ozone-attributable chronic respiratory disease mortality for urban areas worldwide, and their surrounding peri-urban, peri-rural, and rural areas. We estimated ozone-attributable respiratory health outcomes using a modified Global Burden of Diseases, Injuries, and Risk Factors 2019 Study approach. We evaluate long-term trends with linear regressions of annual ozone concentrations and ozone-attributable mortality against time in years, and examined the influence of each health impact function input parameter to temporal changes in ozone-attributable disease burden estimates for 12 946 cities worldwide by region, from 2000 to 2019. FINDINGS: Ozone-attributable mortality worldwide increased by 46% from 2000 (290 400 deaths [95% CI 151 800-457 600]) to 2019 (423 100 deaths [95% CI 223 200-659 400]). The fraction of global ozone-attributable mortality occurring in peri-urban areas remained unchanged from 2000 to 2019 (56%), whereas urban areas gained in their share of global ozone-attributable burden (from 35% to 37%; 54 000 more deaths). Across all cities studied, average population-weighted mean ozone concentration increased by 11% (46 parts per billion [ppb] to 51 ppb). The number of cities with concentrations above the WHO peak season ozone standard (60 µg/m3) increased from 11 568 (89%) of 12 946 cities in 2000 to 12 433 (96%) cities in 2019. Percent change in ozone-attributable mortality averaged across 11 032 cities within each region from 2000 to 2019 ranged from -62% in eastern Europe to 350% in tropical Latin America. The contribution of ozone concentrations, population size, and baseline chronic respiratory disease rates to the change in ozone-attributable mortality differed regionally. INTERPRETATION: Ozone exposure is increasing worldwide, contributing to disproportionate ozone mortality in peri-urban areas and increasing ozone exposure and attributable mortality in urban areas worldwide. Reducing ozone precursor emissions in areas affecting urban and peri-urban exposure can yield substantial public health benefits. FUNDING: NASA Health and Air Quality Applied Sciences Team, the National Institute for Occupational Safety and Health, and the NOAA Co-operative Agreement with the Cooperative Institute for Research in Environmental Sciences.

Are Orthopaedic Trauma Surgeons Adequately Compensated for Longer Procedures? An Analysis of Relative Value Units and Operative Times From the American College of Surgeons National Surgical Quality Improvement Program Database.

BACKGROUND: The physician work relative value unit (wRVU) scale is the primary determinant of compensation. Operative time, technical skill, effort, and surgical complexity contribute to wRVU allocation. The aim of this study was to identify the relationship between these factors and reimbursement for trauma procedures. METHODS: The National Surgical Quality Improvement Program database was queried for orthopaedic trauma procedures from 2016 to 2018. Physician wRVU data were obtained from the 2020 Centers for Medicare & Medicaid Services fee schedule. The primary outcome measured was mean wRVU per minute of operative time (wRVU/min). Wilcoxon rank sum test and quantile regression were used to determine the association between wRVU, operative time, complication rate, upper or lower extremity procedure, and wRVU/min. RESULTS: Sixty-three current procedural terminology codes or 107,171 cases were queried. Median wRVU/min was significantly lower for longest 50% of procedures (0.119 vs. 0.160, P < 0.001) and higher for the top 50% with regard to complication rate (0.161 vs. 0.124, P < 0.001). Upper extremity procedures were reimbursed less than lower extremity (0.110 vs. 0.145, P < 0.001). Quintile regression showed that adjusted for complication rate, median wRVU/min decreased by 0.0005 (95% confidence interval: 0.0007-0.0003, R1 = 0.27, P < 0.001) for every additional minute of operative time. CONCLUSIONS: The 2020 wRVU scale does not allocate sufficient wRVUs to orthopaedic trauma procedures with longer mean operative time or to procedures performed on the upper extremity. There is a negative correlation between operative time and hourly reimbursement, equating to a decrease of $64.96/h per hour of operation.

Improved Implant Positioning of Cephalomedullary Nail for Trochanteric Fractures Using the Stryker ADAPT Navigation System.

BACKGROUND: Tip-apex distance (TAD) of greater than 25 mm increases the risk of cephalomedullary nail (CMN) cutout for trochanteric hip fractures. The Stryker ADAPT navigation system provides intraoperative feedback to guide implant positioning. This study compares lag screw positioning using the ADAPT to conventional methods and investigates if the use of ADAPT impacts operating room efficiency. METHODS: Retrospective review of 82 consecutive patients who underwent Stryker Gamma3 CMN for a peritrochanteric hip fracture. Study groups were assigned based on use of ADAPT navigation. Primary outcome was TAD. Secondary outcomes were lag screw position, operative time, and radiation dose. Univariate analysis of covariance was used to compare primary outcome measures, controlling for fracture classification. RESULTS: 41 patients were assigned to each group. When comparing ADAPT and conventional groups mean TAD was 14.45±3.68 and 16.41±3.78 mm (p = 0.023). A higher portion of ADAPT nails (85.4% vs 63.4%, p = 0.024) were center- center within the femoral head compared to conventional methods. There were no significant differences with regards to operative time, fluoroscopy time, or radiation dose. CONCLUSION: ADAPT navigation provides intraoperative feedback to achieve improved lag screw positioning, leading to improved TAD. The overall improvement in TAD does not likely reach clinical significance. The system requires minimal setup in the operating room, does not impact workflow, and the user interface is straight forward.

Mapping Yearly Fine Resolution Global Surface Ozone through the Bayesian Maximum Entropy Data Fusion of Observations and Model Output for 1990-2017.

Estimates of ground-level ozone concentrations are necessary to determine the human health burden of ozone. To support the Global Burden of Disease Study, we produce yearly fine resolution global surface ozone estimates from 1990 to 2017 through a data fusion of observations and models. As ozone observations are sparse in many populated regions, we use a novel combination of the M3Fusion and Bayesian Maximum Entropy (BME) methods. With M3Fusion, we create a multimodel composite by bias-correcting and weighting nine global atmospheric chemistry models based on their ability to predict observations (8834 sites globally) in each region and year. BME is then used to integrate observations, such that estimates match observations at each monitoring site with the observational influence decreasing smoothly across space and time until the output matches the multimodel composite. After estimating at 0.5° resolution using BME, we add fine spatial detail from an additional model, yielding estimates at 0.1° resolution. Observed ozone is predicted more accurately (R2 = 0.81 at the test point, 0.63 at 0.1°, and 0.62 at 0.5°) than the multimodel mean (R2 = 0.28 at 0.5°). Global ozone exposure is estimated to be increasing, driven by highly populated regions of Asia and Africa, despite decreases in the United States and Russia.

Fellowship Training Is a Significant Predictor of Sports Medicine Physician Social Media Presence.

PURPOSE: To quantify social media use of professional sports team physicians on popular platforms and analyze differences between users and nonusers. METHODS: Team physicians for professional sports teams in the National Football League, National Hockey League, Major League Baseball, and National Basketball Association were identified and characterized based on training background, practice setting, and geographic location. Rates of social media presence on Facebook, Twitter, LinkedIn, Instagram, and ResearchGate were determined. Differences between social media users and nonusers were analyzed. RESULTS: In total, 505 professional team physicians were identified across 4 major professional sports; 64.6% of physicians were orthopaedic surgeons. Of 505 physicians, 65.7% had a social media presence. More specifically, 21.8% had a professional Facebook page, 22.6% a professional Twitter page, 52.1% a LinkedIn profile, 21.4% a ResearchGate profile, and 9.1% an Instagram account. Fellowship-trained physicians (P = .008) had greater odds of having a social media presence. CONCLUSIONS: Nearly two-thirds of professional team physicians have a social media presence, most commonly LinkedIn. Fellowship training is a significant predictor of sports medicine physician social media presence. Sports league affiliation, training background, practice setting, and geographic location are unrelated to social media presence. LEVEL OF EVIDENCE: IV, cross-sectional study.

The Effects of Space Microgravity on Hip and Knee Cartilage: A New Frontier in Orthopaedics.

INTRODUCTION: Given the expansion of commercial and recreational space exploration, orthopaedic surgeons will need to understand the implications of microgravity on cartilaginous damage and to anticipate the resulting pathology from accelerated chondrolysis. The purpose of this systematic review is to evaluate the effects of space and microgravity on hip and knee articular cartilage, including its impact on joint mobility and functional status. MATERIALS AND METHODS: A review of the current literature was performed utilizing the terms "joints," "joint mobility," "articular cartilage," "knee," "hip," "space," "microgravity," and "osteoarthritis" in PubMed and Google Scholar from 1990 to 2018, yielding a total of 1,400 citations following the removal of 500 duplicates. Following screening by eligibility criteria, five reports were included. RESULTS: Dysregulation of osteogenesis and weakened structural integrity of hip and knee cartilage were demonstrated secondary to microgravity. Adequate cartilage repair requires Earth-like conditions as signified by a statistically significant increase in serum cartilage oligomeric matrix protein concentrations in astronauts. Reduced loading led to the degradation of knee ligaments and menisci which may pose a risk for subluxation or dislocation. Murine studies demonstrated decreased articular cartilage thickness in the medial femoral condyle and patella as assessed by ultrasound. Additionally, glycosaminoglycan levels in unloaded rats were lower than weight-bearing rats, with a concomitant increase in matrix metalloproteinase-13 protein, degrading collagen. Return to weight-bearing demonstrated partial recovery of cartilaginous degeneration. CONCLUSIONS: Space and associated microgravity conditions adversely impact articular cartilage as demonstrated in murine and human studies. The pathogenetic process occurs due to the mechanically responsive nature of cartilage, with an increase in cartilage metabolism in microgravity. There remains a marked paucity of literature regarding the gravitational force necessary for adequate cartilage survival and the impact of space-related radiation on cartilage repair. Additionally, further studies should assess pharmacologic interventions, such as recombinant human fibroblast growth factor to stimulate cartilaginous growth.

Accurate charge densities from powder X-ray diffraction - a new version of the Aarhus vacuum imaging-plate diffractometer.

In recent years powder X-ray diffraction has proven to be a valuable alternative to single-crystal X-ray diffraction for determining electron-density distributions in high-symmetry inorganic materials, including subtle deformation in the core electron density. This was made possible by performing diffraction measurements in vacuum using high-energy X-rays at a synchrotron-radiation facility. Here we present a new version of our custom-built in-vacuum powder diffractometer with the sample-to-detector distance increased by a factor of four. In practice this is found to give a reduction in instrumental peak broadening by approximately a factor of three and a large improvement in signal-to-background ratio compared to the previous instrument. Structure factors of silicon at room temperature are extracted using a combined multipole-Rietveld procedure and compared with ab initio calculations and the results from the previous diffractometer. Despite some remaining issues regarding peak asymmetry, the new diffractometer yields structure factors of comparable accuracy to the previous diffractometer at low angles and improved accuracy at high angles. The high quality of the structure factors is further assessed by modelling of core electron deformation with results in good agreement with previous investigations.

Effect of hydrothermal liquefaction aqueous phase recycling on bio-crude yields and composition.

Hydrothermal liquefaction (HTL) is a promising thermo-chemical processing technology for the production of biofuels but produces large amounts of process water. Therefore recirculation of process water from HTL of dried distillers grains with solubles (DDGS) is investigated. Two sets of recirculation on a continuous reactor system using K2CO3 as catalyst were carried out. Following this, the process water was recirculated in batch experiments for a total of 10 rounds. To assess the effect of alkali catalyst, non-catalytic HTL process water recycling was performed with 9 recycle rounds. Both sets of experiments showed a large increase in bio-crude yields from approximately 35 to 55wt%. The water phase and bio-crude samples from all experiments were analysed via quantitative gas chromatography-mass spectrometry (GC-MS) to investigate their composition and build-up of organic compounds. Overall the results show an increase in HTL conversion efficiency and a lower volume, more concentrated aqueous by-product following recycling.

Hydrothermal Synthesis of TiO2@SnO2 Hybrid Nanoparticles in a Continuous-Flow Dual-Stage Reactor.

TiO2@SnO2 hybrid nanocomposites were successfully prepared in gram scale using a dual-stage hydrothermal continuous-flow reactor. Temperature and pH in the secondary reactor were found to selectively direct nucleation and growth of the secondary material into either heterogeneous nanocomposites or separate intermixed nanoparticles. At low pH, 2 nm rutile SnO2 nanoparticles were deposited on 9 nm anatase TiO2 particles; the presence of TiO2 was found to suppress formation of larger SnO2 particles. At high pH SnO2 formed separate particles and no deposition on TiO2 was observed. Ball-milling of TiO2 and SnO2 produced no TiO2@SnO2 composites. This verifies that the composite particles must be formed by nucleation and growth of the secondary precursor on the TiO2 . High concentration of secondary precursor led to formation of TiO2 particles embedded in aggregates of SnO2 nanoparticles. The results demonstrate how nanocomposites may be produced in high yield by green chemistry.

Using design of experiments to optimize derivatization with methyl chloroformate for quantitative analysis of the aqueous phase from hydrothermal liquefaction of biomass.

Hydrothermal liquefaction is a promising technique for the production of bio-oil. The process produces an oil phase, a gas phase, a solid residue, and an aqueous phase. Gas chromatography coupled with mass spectrometry is used to analyze the complex aqueous phase. Especially small organic acids and nitrogen-containing compounds are of interest. The efficient derivatization reagent methyl chloroformate was used to make analysis of the complex aqueous phase from hydrothermal liquefaction of dried distillers grains with solubles possible. A circumscribed central composite design was used to optimize the responses of both derivatized and nonderivatized analytes, which included small organic acids, pyrazines, phenol, and cyclic ketones. Response surface methodology was used to visualize significant factors and identify optimized derivatization conditions (volumes of methyl chloroformate, NaOH solution, methanol, and pyridine). Twenty-nine analytes of small organic acids, pyrazines, phenol, and cyclic ketones were quantified. An additional three analytes were pseudoquantified with use of standards with similar mass spectra. Calibration curves with high correlation coefficients were obtained, in most cases R (2) > 0.991. Method validation was evaluated with repeatability, and spike recoveries of all 29 analytes were obtained. The 32 analytes were quantified in samples from the commissioning of a continuous flow reactor and in samples from recirculation experiments involving the aqueous phase. The results indicated when the steady-state condition of the flow reactor was obtained and the effects of recirculation. The validated method will be especially useful for investigations of the effect of small organic acids on the hydrothermal liquefaction process.

Synchrotron powder diffraction of silicon: high-quality structure factors and electron density.

Crystalline silicon is an ideal compound to test the current state of experimental structure factors and corresponding electron densities. High-quality structure factors have been measured on crystalline silicon with synchrotron powder X-ray diffraction. They are in excellent agreement with benchmark Pendellösung data having comparable accuracy and precision, but acquired in far less time and to a much higher resolution (sin θ/λ < 1.7 Å(-1)). The extended data range permits an experimental modelling of not only the valence electron density but also the core deformation in silicon, establishing an increase of the core density upon bond formation in crystalline silicon. Furthermore, a physically sound procedure for evaluating the standard deviation of powder-derived structure factors has been applied. Sampling statistics inherently account for contributions from photon counts as well as the limited number of diffracting particles, where especially the latter are particularly difficult to handle.

The formation mechanism of bimetallic PtRu alloy nanoparticles in solvothermal synthesis.

An understanding of the nucleation and growth mechanism of bimetallic nanoparticles in solvothermal synthesis is important for further development of nanoparticles with tailored nanostructures and properties. Here the formation of PtRu alloy nanoparticles in a solvothermal synthesis using metal acetylacetonate salts as precursors and ethanol as both the solvent and reducing agent has been studied by in situ synchrotron radiation powder X-ray diffraction (SR-PXRD). Unlike the classical mechanism for the synthesis of monodisperse sols, the nucleation and growth processes of bimetallic PtRu nanoparticles occur simultaneously under solvothermal conditions. In the literature co-reduction of Pt and Ru is often assumed to be required to form PtRu bimetallic nanocrystals, but it is shown that monometallic Pt nanocrystals nucleate first and rapidly grow to an average size of 5 nm. Subsequently, the PtRu bimetallic alloy is formed in the second nucleation stage through a surface nucleation mechanism related to the reduction of Ru. The calculated average crystallite size of the resulting PtRu nanocrystals is smaller than that of the primary Pt nanocrystals due to the large disorder in the PtRu alloyed structure.

Analysis of organic gas phase compounds formed by hydrothermal liquefaction of Dried Distillers Grains with Solubles.

This work provides a comprehensive characterization of the gas phase from hydrothermal liquefaction of Dried Distillers Grains with Solubles (DDGS) collected during a 24-h continuous experiment. The gas consisted mainly of CO2, CO, H2, CH4 and C2H6 accounting for 96 v/v% while further analysis by gas chromatography coupled to mass spectrometry (GC-MS) showed additionally 62 compounds of which 54 were tentatively identified. These products included methanethiol, dimethyl sulfide, various olefins and several aromatic compounds. The composition provided clear indication of the steady state of the system. Apart from CO2, olefins were the most abundant compound class and could provide a source of revenue.

Experimental determination of core electron deformation in diamond.

Synchrotron powder X-ray diffraction data are used to determine the core electron deformation of diamond. Core shell contraction inherently linked to covalent bond formation is observed in close correspondence with theoretical predictions. Accordingly, a precise and physically sound reconstruction of the electron density in diamond necessitates the use of an extended multipolar model, which abandons the assumption of an inert core. The present investigation is facilitated by negligible model bias in the extraction of structure factors, which is accomplished by simultaneous multipolar and Rietveld refinement accurately determining an atomic displacement parameter (ADP) of 0.00181 (1) Å(2). The deconvolution of thermal motion is a critical step in experimental core electron polarization studies, and for diamond it is imperative to exploit the monatomic crystal structure by implementing Wilson plots in determination of the ADP. This empowers the electron-density analysis to precisely administer both the deconvolution of thermal motion and the employment of the extended multipolar model on an experimental basis.

Model-independent structure factors from powder X-ray diffraction: a novel approach.

Under the experimental condition that all Bragg peaks in a powder X-ray diffraction (PXRD) pattern have the same shape, one can readily obtain the Bragg intensities without fitting any parameters. This condition is fulfilled at the P02.1 beamline at PETRA III using the seventh harmonic from a 23 mm-period undulator (60 keV) at a distance of 65 m. For grain sizes of the order of 1 µm, the Bragg peak shape in the PXRD is entirely determined by the diameter of the capillary containing the powder sample and the pixel size of the image plate detector, and consequently it is independent of the scattering angle. As an example, a diamond powder has been chosen and structure factors derived which are in accordance with those calculated from density functional theory methods of the WIEN2k package to within an accuracy that allows a detailed electron density analysis.

The Debye-Scherrer camera at synchrotron sources: a revisit.

In a powder diffraction pattern one measures the intensity of Miller-indexed Bragg peaks versus the wavevector transfer sinθ/λ. With increasing wavevector transfer the density of occurrence of Bragg peaks increases while their intensity decreases until they vanish into the background level. The lowest possible background level is that due to Compton scattering from the powder. A powder diffraction instrument has been designed and tested that yields this ideal low-background level, obtainable by having the space between sample and detector all in vacuum with the entrance window so far upstream that scattering from it is negligible. To minimize overlap of Bragg peaks the combination of fine collimation of synchrotron radiation, a thin cylindrical sample and a high-resolution imaging plate detector is taken advantage of.