High-resolution STEM imaging with a quadrant detector--conditions for differential phase contrast microscopy in the weak phase object approximation.

Differential phase contrast is a contrast mechanism that can be utilized in the scanning transmission electron microscope (STEM) to determine the distribution of magnetic or electric fields. In practice, several different detector geometries can be used to obtain differential phase contrast. As recent high resolution differential phase contrast experiments with the STEM are focused on ring quadrant detectors, we evaluate the contrast transfer characteristics of different quadrant detector geometries, namely two ring quadrant detectors with different inner detector angles and a conventional quadrant detector, by calculating the corresponding phase gradient transfer functions. For an ideal microscope and a weak phase object, this can be done analytically. The calculated phase gradient transfer functions indicate that the barely illuminated ring quadrant detector setup used for imaging magnetic fields in the specimen reduces the resolution limit to about 2.5Å for an aberration corrected STEM. Our results show that the resolution can be drastically improved by using a conventional quadrant detector instead.

Physical fitness measures among children and adolescents: are they all necessary?

AIM: The aim of this paper was to investigate the relationship among health and skill-related physical fitness variables, and with anthropometric measures in a sample of children and adolescents. METHODS: A cross-sectional study was conducted with 526 Brazilian students aged 7-15 years. Physical fitness abilities/skills were assessed through a battery of eight tests: sit-and-reach, standing long jump, 1-minute curl-up, modified pull-up, medicine-ball throw, 9-minute run, 20-meter run and 4 meter shuttle-run. Anthropometric measures considered were weight, height, body mass index (BMI) and wingspan. Analyses included descriptive statistics, Pearson correlations, multiple linear regression and principal component analysis. RESULTS: Anthropometric measures were directly associated between each other. Weight and BMI were negatively associated with the performance in all physical tests requiring propulsion or lifting of the body mass. Direct associations between tests persisted after adjustments for sex, age, type of school and geographic region of school. CONCLUSION: Results from the principal component analysis evidenced that all physical abilities/motor skills, except flexibility, are strongly associated with each other, suggesting that one test can reflect the overall fitness among youth. Although it is unclear from these analyses which test would be the single choice indicator, previous work on the health impact of cardiorespiratory fitness would suggest that.

Health-related quality of life, BMI and physical activity among US adults (>/=18 years): National Physical Activity and Weight Loss Survey, 2002.

OBJECTIVE: To examine the association between health-related quality of life (HRQOL) and physical activity (PA). METHODS: Cross-sectional data were obtained via a national telephone survey from 9173 respondents (30.9% response rate; 51.4% cooperation rate). Four indicators of HRQOL were measured: self-rated health, physically unhealthy days, mentally unhealthy days and activity limitation days. Prevalence estimates were calculated by body mass index (BMI) category and PA level. Logistic regression evaluated BMI as an effect modifier of the relationship between HRQOL and PA. RESULTS: Inactive adults reported more fair to poor HRQOL than active adults, regardless of BMI category (P<0.001). BMI did not modify the association between PA and any of the four HRQOL indicators. CONCLUSION: Prevalence of low HRQOL is inversely related to PA participation, and the relationship is not altered by BMI status. Regardless of their weight status, adults should be encouraged to engage in PA.

Interactive effects of tunnel dilation on the mechanical properties of hamstring grafts fixed in the tibia with interference screws.

The effect of dilation of the tibial tunnel on the strength of hamstring graft fixation using interference screws was evaluated. In all, 28 RCI screws were tested in male human tibia-hamstring constructs with tibial tunnels reamed or dilated to the respective size of the graft diameter. Dilation of the tibial tunnel failed to significantly enhance hamstring fixation. Grafts secured in dilated tunnels displayed an 11% greater resistance to the initiation of graft slippage (174+/-112 N) compared to their undilated controls (156+/-77 N, P=0.63). Dilation of the tibial tunnel increased the failure load by an average of 4%, independent of screw diameter (dilated specimens: 360+/-120 N, controls: 345+/-88 N, P=0.74). Biomechanical research on the effect of tibial tunnel dilation in hamstring fixation has not provided satisfactory evidence as to the benefits of this additional surgical step during anterior cruciate ligament (ACL) reconstruction.

Quantitative analyses of the biomineralization of different hard tissues.

The primary crystallites of the different developing hard tissues have an apatite structure. However, they have crystal lattice distortions representing an intermediate state between amorphous and fully crystalline. We have applied energy-filtering transmission electron microscopy in the selected area electron diffraction mode to analyse different stages of crystal formation in dentine, bone, enamel and inorganic apatite mineral. We have obtained quantitative information on the degree of crystal lattice distortion using the paracrystal theory of Hosemann and Bagchi. We have found that the early formed crystallites of the hard tissues being analysed have a paracrystalline character comparable to biopolymers. However, with maturation, the lattice fluctuations of the crystallites of the hard tissues bone, enamel and dentine decrease to form a typical (para)crystalline character. Also the decrease of the organic proportion in the matrix corresponds to the decrease of the lattice fluctuation of the crystallites in the different hard tissues during maturation.

Biomechanical evaluation of the origin of the long head of the biceps tendon.

PURPOSE: Lesions of the superior glenoid labrum extending anterior and posterior (SLAP) have recently been recognized as important sources of shoulder pain and dysfunction. Among the 4 described types of SLAP lesions, the type II SLAP involves detachment of the superior labrum from the bony glenoid and destabilization of the origin of the long head of the biceps tendon (LHBT). The purpose of this cadaveric biomechanical study was to evaluate the relative contribution regarding linear stiffness and displacement under load of the 2 origins of the LHBT: the superior glenoid labrum and the supraglenoid tubercle (the biceps anchor). TYPE OF STUDY: Cadaveric biomechanical study. METHODS: Seven pairs of fresh-frozen cadaveric shoulders were dissected free of all soft tissue except for the glenoid labrum and LHBT. Tension from 0 to 55 N was applied to the LHBT while keeping the tendon perpendicular to the face of the glenoid. Each specimen was tested for linear stiffness and biceps tendon displacement in the intact state, after releasing 1 of the LHBT origins, and after releasing the remaining origin. RESULTS: The average stiffness of the LHBT origin was 103 N/mm. Sectioning the anchor alone resulted in a 52% reduction in linear stiffness, whereas only detaching the superior glenoid labrum from the 10 o'clock to the 2 o'clock position resulted in a 15% reduction in linear stiffness. Maximum displacement of the biceps tendon origin in the intact state at the 55 N load averaged 0.99 mm. With a minimum load applied, displacement changed less than 1 mm unless both origins were released. CONCLUSIONS: The results indicate that the biceps anchor is the primary restraint of the LHBT and that the superior labrum is a secondary restraint in regard to linear stiffness. However, disruption of both restraints is required to produce the laxity typically seen in a type II SLAP lesion.

Field evaluation of energy expenditure from continuous and intermittent walking in women.

RATIONALE: Recent physical activity recommendations suggest that comparable amounts of prescribed physical activity, done as a single continuous bout or as a set of intermittent bouts, will produce equal amounts of energy expenditure (EE) during the prescribed activity as well as throughout the day. HYPOTHESES: In a field setting, we tested two hypotheses: (1) continuous and intermittent walking conditions will result in significantly greater total daily EE than a control condition, and (2) continuous and intermittent walking conditions will result in similar total daily METHODS: Thirty women (mean age [yr] = 43.7+/-5.8; mean body mass index [kg x m(-2)]= 24.7+/-4.0) participated in a repeated-measures design so that each woman participated in three walking conditions on successive days of the week: a single 30-min brisk walk (continuous): three 10-min brisk walks (intermittent); and no activity (control). Throughout the study protocol, women wore a TRITRAC-R3D accelerometer programmed to estimate EE in 2-min intervals. RESULTS: Mean total EE estimates (kcal) for the three walking conditions were as follows: continuous: 2181+/-308; intermittent: 2121+/-305; and control: 1948+/-270. A repeated-measures analysis of variance omnibus test indicated that EE differed significantly by experimental condition [F(2,58) = 40.2, P < 0.001). To test the first hypothesis, contrasts were examined revealing that EE in the continuous and intermittent conditions was significantly greater than EE in the control condition [F(1,29) = 58.2, P < 0.001]. To test the second hypothesis, contrasts revealed that EE in the continuous condition was significantly greater than EE in the intermittent condition [F(1,29) = 7.0, P = 0.013]. CONCLUSION: For the purposes of total EE, selecting a continuous mode of walking may offer additional benefit over an intermittent mode, given the same total prescribed duration.

Pelvic fracture among polytrauma decedents. Trauma-based mortality with pelvic fracture--a case series of 74 patients.

Pelvic fractures (PF) sustained from accidents are commonly believed to be a major cause of mortality in polytraumatized patients. The purpose of this paper is to determine whether PF are usually the primary cause or a contributing cause of mortality in these patients. A 10-year retrospective review was performed of all polytrauma patients with PF who were admitted to, and died, at a large, level-I trauma center. The pelvic injury was graded according to Schatzker and Tile into stable (type A), partially stable (type B), and unstable (type C). The injury severity score (ISS), which incorporates associated injuries and their potential impact on mortality, was calculated for all patients. For each patient, a separate subjective designation of the probable cause of death was determined. We identified 74 decedents with PF following deceleration trauma. The pelvic fractures were classified as 12 type A (16%), 36 type B (49%), and 26 type C (35%). The mean ISS was extremely high, 40.6 +/- 1.4 (range 18-75), more than four times the score for simply a severe PF. The ISS was also not significantly different among the three pelvic fracture groups (P = 0.613). The records subjectively identified PF as the precipitating cause of death in only 13% of the patients. In this study, patients who died with PF had an ISS that implicated at least one or two additional major visceral injuries. These data do not support the hypothesis that PF, regardless of its complexity, is the usual primary cause or the major precipitating event of death in the polytraumatized patient. In these patients, mortality appears to be a function of the associated injuries based on the ISS calculation.

Work ability, physical activity, and cardiorespiratory fitness: 2-year results from Project Active.

An adequate level of physical activity may maintain or promote work ability in aging workers. Project Active is a randomized trial comparing a Lifestyle physical activity program with a Structured exercise program in sedentary but healthy adults aged 35 to 60 years. Subjects in both groups received 6 months of intensive intervention followed by 18 months of active follow-up. The total number of subjects was 235, from which 80 subjects participated in the work ability assessment. Primary outcome measures were energy expenditure (kcal.kg-1.day-1), cardiorespiratory fitness (peak oxygen uptake in ml.min-1.kg-1), and the Work Ability Index. At 6 months, daily energy expenditure had increased significantly over baseline (mean +/- SD, from 33.0 +/- 0.9 to 34.4 +/- 1.8 kcal.kg-1.day-1) and was maintained over baseline at 24 months (34.0 +/- 2.5 kcal.kg-1.day-1). The significant increase in energy expenditure was observed particularly in moderate levels of activity. The average percentage of body fat was significantly higher at baseline compared with 6 months and 24 months. Peak oxygen uptake increased from baseline significantly during the first 6 months (from 29.6 +/- 5.7 to 30.6 +/- 6.3 ml.min-1.kg-1) and decreased to the baseline level (29.1 +/- 5.5 ml.min-1.kg-1) at 24 months. At baseline, the average Work Ability Index was 44.2 +/- 4.0, and it remained unchanged at 6 months (44.4 +/- 3.9) and at 24 months (44.2 +/- 3.1). In conclusion, a 2-year physical activity intervention increased daily energy expenditure, reduced body fat, and maintained peak oxygen uptake in healthy, middle-aged, sedentary subjects. The average Work Ability Index score at baseline was excellent and did not change during the 2-year physical activity interventions.

Reliability of the Lichtman classification of Kienböck's disease.

The purpose of this study was to establish the interobserver reliability and intraobserver reproducibility of the staging of Kienböck's disease according to Lichtman's classification. Posteroanterior and lateral wrist radiographs of 64 patients with a diagnosis of Kienböck's disease and 10 control subjects were reviewed independently by 4 observers on 2 separate occasions. The reviewers included 3 hand fellowship-trained surgeons and 1 orthopedist who was not fellowship-trained in hand surgery. A stage was assigned to each set of radiographs according to the Lichtman classification. Paired comparisons for reliability among the 4 observers showed an average absolute percentage agreement of 74% and an average paired weighted kappa coefficient of 0.71. Furthermore, all the controls were correctly classified as stage I, which is in accordance with the Lichtman system. With regard to reproducibility, observers duplicated their initial readings 79% of the time with an average weighted kappa coefficient of 0.77. These results indicate substantial reliability and reproducibility of the Lichtman classification for Kienböck's disease.

Computation of contrasts in atomic resolution electron spectroscopic images of planar defects in crystalline specimens

The image obtained in a conventional transmission electron microscope contains contributions from elastically and from inelastically scattered electrons. The electron spectroscopic imaging mode of an energy-filtering transmission electron microscope allows us to separate these two different contributions by inserting an energy-selecting slit in the energy-dispersive plane of an imaging energy filter. Selecting a specific energy loss corresponding to the ionization of the inner shell of a particular element one can obtain information on the distribution of the element within the specimen. The contrast is then caused by inelastically scattered electrons. For crystalline specimens, however, the contrast will be influenced additionally by the elastic contrast. This elastic contrast arises from electron diffraction and increases with increasing crystal thickness. Therefore the intensity distribution in the image cannot directly be interpreted as an elemental map. For a reliable interpretation of contrast formation in elemental maps it is therefore necessary to compute theoretical energy-loss images for various crystal thicknesses and compare these images with the experimental images. As an example we discuss the influence of electron diffraction effects on energy-loss images of two crystals with planar defects. Linescans are computed for various thicknesses of these crystals. Our calculations are performed using first-order perturbation theory to describe the transitions between the Bloch-wave states of the incident electron. The computed linescans for various crystal thicknesses show clearly that the influence of the elastic contrast on an image increases when we investigate thicker specimens. Furthermore, the comparison between elastic and energy-loss images demonstrates the partial preservation of the elastic contrast as a function of thickness. We find that for specimens thicker than about one third of the extinction length (here approximately 80-100 A) it is impossible to interpret an energy-loss image directly as elemental map.

Methods for ELNES-quantification: characterization of the degree of inversion of Mg-Al-spinels

The energy loss near-edge structures in electron energy-loss spectra contain information about bonding characteristics, the electronic structure and coordinations of the excited atoms. We have calculated sets of reference spectra for the normal and for the inverse Mg-Al-spinel using a full multiple scattering approach. By a quantitative comparison of these reference spectra with experimental data ELNES-quantification becomes possible. We characterized the degree of inversion lambda by the analysis of the relative peak-intensities and the relative peak-positions within 35 eV beyond the edge onset. The results demonstrate that by using the provided methods ELNES-quantification will become possible when uncertainties in the experiment are reduced and a better fit of the simulations to the experiment is achieved.

Effect of quadriceps contraction on tangential patellar radiography.

This study examined whether the addition of quadriceps contraction to standard Merchant views provides additional useful information in the evaluation of patients with extensor mechanism malalignment. Fifteen patients (23 knees) with anterior knee pain due to lateral patellar compression syndrome and 22 control patients (44 knees) underwent standard Merchant views with the quadriceps relaxed and with an isometric isotonic contraction. Congruence and lateral patellar angles were measured for all groups. Although the congruence angle differed significantly between the control and symptomatic groups with the quadriceps contracted (P< or = .001), this difference also was seen without quadriceps contraction. There was also no significant difference within each group on addition of quadriceps contraction. No significant difference existed between the two groups for lateral patellar angle with quadriceps contraction. The addition of a controlled isometric quadriceps contraction did not add to the diagnostic yield of the standard Merchant view in terms of a predictable change in measured radiographic parameters.

Physical training as a substance abuse prevention intervention for youth.

Program evaluation data from school and community applications of a physical fitness drug prevention program is presented. A train-the-trainer methodology was applied to install the program in twenty-two settings within the state of Illinois. The physical training program consisted of exercise and educational modules delivered over a twelve-week time period that focused on learning values and life skills through exercise. Complete pre-post data were obtained on 329 participating youth at six school and community based sites. Significant increases were demonstrated in physical activity and physical fitness (cardiovascular endurance, strength, and flexibility). Youth self-report data indicated significant decreases in risk factors such as low self-concept, poor school attendance, anxiety, depression, and number of friends who use alcohol and drugs. There were significant reductions in the percentage of youth who used cigarettes, smokeless tobacco, and alcohol. It was concluded that a strong relationship was demonstrated for increased fitness leading to lowered risk factors and usage patterns. Likewise, the train-the-trainer model was shown to be an effective installation approach to expand fitness programming within prevention settings.

Long-term functional and radiographic follow-up of surgically treated isthmic spondylolisthesis.

We studied patients treated surgically for isthmic spondylolisthesis since 1968, with special emphasis on a detailed functional assessment. We followed up 22 patients for an average of 15 years, with a mean age at time of surgery of 18 years. All patients underwent a thorough physical examination and were evaluated with radiographs at baseline and at follow-up. The functional status of patients at the time of follow-up was assessed with 2 self-report pain and function instruments. All surgical procedures included spinal fusion, 12 of which included internal fixation by using Harrington distraction rods with sacral bars. At final follow-up, there was no statistically significant difference in mean slip percentage or mean slip angle compared with baseline radiographs. Functional evaluation was compared with a control group consisting of 52 patients. We conclude that the long-term radiographic and functional outcome is excellent for patients treated surgically for isthmic spondylolisthesis.

Cyclic pull-out strength of hamstring tendon graft fixation with soft tissue interference screws. Influence of screw length.

Blunt-threaded interference screws used for fixation of hamstring tendons in anterior cruciate ligament reconstructions provide aperture fixation and may provide a biomechanically more stable graft than a graft fixed further from the articular surface. It is unknown if soft tissue fixation strength using interference screws is affected by screw length. We compared the cyclic and time-zero pull-out forces of 7 x 25 mm and 7 x 40 mm blunt-threaded metal interference screws for hamstring graft tibial fixation in eight paired human cadaveric specimens. A four-stranded autologous hamstring tendon graft was secured by a blunt-threaded interference screw into a proximal tibial tunnel with a diameter corresponding to the graft width. Eight grafts were secured with a 25-mm length screw while the other eight paired grafts were secured with a 40-mm length screw. During cyclic testing, slippage of the graft occurred as the force of pull became greater with each cycle until the graft-screw complex ultimately failed. All grafts failed at the fixation site, with the tendon being pulled past the screw. There were no measurable differences in the mean cyclic failure strength, pull-out strength, or stiffness between the two sizes of screws. Although use of the longer screw would make removal technically easier should revision surgery be necessary, it did not provide stronger fixation strength than the shorter, standard screw as had been postulated.

Detecting bouts of physical activity in a field setting.

The purposes of this study were to assess the TRITRAC and CSA for: (a) interaccelerometer agreement; (b) agreement in detecting patterns of moderate-intensity physical activity; and (c) agreement in detecting walking patterns recorded in a diary. Thirty-one women wore both the TRITRAC and CSA accelerometers for three consecutive days. Interaccelerometer agreement (measured with generalizability coefficients) ranged from .88 to .99. In total, 71.3% of the accelerometers' patterns agreed in length, with CSA patterns being on average significantly longer. Interaccelerometer agreement in detecting patterns of brisk walking, as recorded in a diary, was comparable (69.4%). Interaccelerometer discrepancies may be related in part to the threshold employed by each instrument for classifying moderate intensity patterns.

Quantitative electron spectroscopic diffraction analyses of the crystal formation in dentine.

Newly formed apatitic crystallites of different hard tissues consist, according to our investigations, of chains composed of nanometre-sized particles (islands, dots) arising at nucleating sites of the collagenous and noncollagenous matrix macromolecules. In dentine these islands coalesce rapidly in longitudinal direction to form needle-like crystallites which further coalesce to ribbon-like crystallites. We have concluded that the centre-to-centre distances between these islands represent the distances between the nucleating sites of the matrix macromolecules. We have applied energy-filtering transmission electron microscopy in the selected area electron diffraction mode at different stages of crystal formation in dentine and have obtained quantitative information of the degree of crystal disorder on the basis of the paracrystal theory. The fluctuation of the lattice plane distances in c-axis direction decreases, proceeding from the region near the dentine/predentine border to the dentine/enamel border.

Helicobacter pylori increases the risk of peptic ulcer bleeding: a case-control study.

AIM: Aim of the present case-control study was to establish whether Helicobacter pylori increases the risk of ulcer bleeding. PATIENTS AND METHODS: All patients presenting with upper gastrointestinal bleeding between November 1994 and November 1995 were prospectively investigated and compared with hospital controls matched for age, sex, and race. We evaluated the frequency of Helicobacter pylori infection, intake of aspirin or non-steroidal anti-inflammatory drugs, use of alcohol, and smoking habits in patients and controls. RESULTS: Included in the study were 128 patients. In 72 patients, the source of bleeding was a peptic ulcer (duodenal ulcer: n = 33; gastric ulcer: n = 39). Ulcer patients were more frequently infected by Helicobacter pylori than controls (72% vs 42%; p < 0.001) while the incidence of infection was similar in patients with non-ulcer bleeding and controls (52% vs 46%; p = 0.59). Conditional multiple logistic regression analysis showed that Helicobacter pylori infection (odds ratio, 3.3 [Confidence interval, 1.5 to 7.0]; p = 0.002) and regular use of alcohol (odds ratio, 3.1 [Confidence interval, 1.0 to 9.0]; p = 0.041) increased the risk of peptic ulcer bleeding while previous intake of aspirin (> 100 mg) or non-steroidal anti-inflammatory drugs independently increased the risk of bleeding only in the case of gastric ulcer (odds ratio, 8.1 [Confidence interval 1.2 to 56.6]; p = 0.034). CONCLUSIONS: Helicobacter pylori infection increases the risk of peptic ulcer bleeding. Our results suggest that Helicobacter pylori and non-steroidal anti-inflammatory drugs are independent risk factors for peptic ulcer bleeding.