The physiological stress response to high-intensity sprint exercise following the ingestion of sodium bicarbonate

The purpose of this study was to investigate the effects of pre-exercise alkalosis on the physiological stress response to high-intensity exercise. Seven physically active males (age 22 ± 3 years, height 1.82 ± 0.06 m, mass 81.3 ± 8.4 kg and peak power output 300 ± 22 W) performed a repeated sprint cycle exercise following a dose of 0.3 g kg^?1 body mass of sodium bicarbonate (NaHCO₃) (BICARB), or a placebo of 0.045 g kg^?1 body mass of sodium chloride (PLAC). Monocyte-expressed heat shock protein 72 (HSP72) and plasma thiobarbituric acid reactive substances (TBARS) were significantly attenuated in BICARB compared to PLAC (p = 0.04 and p = 0.039, respectively), however total anti-oxidant capacity, the ratio of oxidised to total glutathione, cortisol, interleukin 6 and interleukin 8 were not significantly induced by the exercise. In conclusion, monocyte-expressed HSP72 is significantly increased following high-intensity anaerobic exercise, and its attenuation following such exercise with the ingestion of NaHCO₃ is unlikely to be due to a decreased oxidative stress.     

Kinetic investigation of the hydrolysis of uranium hexafluoride gas

UF₆ is commonly employed in enrichment technologies and is known to react rapidly with water vapor to form radioactive particulates and hydrofluoric acid vapor. The kinetics of the UF₆ hydrolysis reaction have been observed directly for the first time. The rate appears to be half order and second order for UF₆ and water, respectively, with a rate constant of 1.19 ± 0.22 Torr^−3/2 s⁻¹. The proposed mechanism involves formation of the [UF₆·2H₂O] adduct via two separate reactions.

Direct observation of the hydrolysis reaction kinetics of gaseous UF₆ have been measured under low-pressure conditions.

Uranium hexafluoride (UF₆) is a key compound in the nuclear fuel cycle as the material employed in commercial enrichment, enabling production of the fuel for electricity production in nuclear power reactors. Studies evaluating the safety implications of small or large releases of UF₆ within a processing facility have been performed previously,^1–3 as it is well known that this material undergoes a hydrolysis reaction in ambient air according to the simplified reaction:UF₆(g) + 2H₂O(g) → UO₂F₂(s) + 4HF(g)producing both uranium particulates and hydrofluoric acid vapor. Recent work⁴ has explored the formation of the uranium particulate materials but the precise molecular mechanism of the initiating reaction has yet to be verified. Previous efforts to characterize this reaction have focused on spectroscopic measurements^5–7 and computational studies.^8–13 The experimental studies have focused on the spectroscopic detection of uranium species but lacked the temporal resolution to observe the reaction or identify any transient species. Unfortunately, there are major discrepancies between the experimentally observed reaction and computationally predicted mechanisms. For example, the computational studies suggest large thermodynamic energy barriers that would likely prevent the reaction of UF₆ and water vapor,^9–13 yet the hydrolysis reaction is known to occur quickly and completely under ambient conditions.^5–7 Additionally, one of the long-suspected intermediates of this reaction, UOF₄, has not been successfully identified under extreme conditions designed to optimize its production such as reacting water with a 5000-fold excess of UF₆.¹⁴ Relevant spectroscopy measurements need to be performed to inform computational modelling because the mechanism may not be driven by a stepwise reaction of UF₆ and water molecules.One prior study performed an indirect measurement of the rate of the UF₆ hydrolysis by monitoring the ingrowth of hydrogen fluoride with a laser-based analyzer.¹⁵ The reported rate constant of 4 ± 4 × 10⁻¹⁸ cm³ s⁻¹ remains questionable as limited experimental details were reported. Based on their findings, and assuming pseudo-first order kinetics under these reaction conditions in excess water vapor, the reaction half-life is calculated to be on the order of 1 ms or less. Standard infrared spectroscopy instrumentation cannot scan with submillisecond temporal resolution, requiring specialized instrumentation that has only recently become available.This work focused on observing the disappearance of UF₆ under low pressure conditions by probing the most sensitive infrared (ν₃ antisymmetric stretching) vibrational band,¹⁶ located at 625 cm⁻¹, using a 5 m long-path length cell. The long path length combined with the sensitivity of the band allow the reaction rate to be investigated at sub-Torr partial pressures. The reaction is slow enough at these pressures to allow direct kinetic measurements of the hydrolysis to be made using a typical infrared spectrometer.Experiments were performed in a 5 m long-path length gas cell fitted to an ABB MB3000 Fourier transform infrared spectrometer. The chamber was exposed to fluorine gas to passivate materials of construction and remove water from surfaces within the spectroscopy cell before each experiment. The UF₆ was then introduced into the evacuated cell at pressures between 10 and 30 mTorr and ambient temperature (22.5 ± 0.5 °C). (Warning: UF₆ is a radioactive gas that forms highly toxic hydrogen fluoride in the presence of water.) After initial infrared spectroscopy measurements were made, 60 or 80 mTorr of water vapor was injected into the system and allowed to react. Typical infrared spectra collected during the hydrolysis reaction occurred during 0.5–2 min for these conditions, as shown in Fig. 1A. Note, the reactions that occurred when water vapor was introduced at these partial pressures were approximately an order of magnitude faster than any reactions of UF₆ with materials of construction. The observed rates (Fig. 1B) were significantly slower than those expected from diffusion-limited reactivity, suggesting that mixing occurred rapidly from the injection method.Open in a separate windowFig. 1(A) Select infrared spectra showing the 625 cm⁻¹ band of UF₆ just before introducing water vapor (red) and every 10 s after (blue) for 1 min. (B) Example of absorbance change of the 625 cm⁻¹ band over time during a typical hydrolysis experiment. The rate of disappearance of the UF₆ increased about a factor of 10 when H₂O was introduced.Typical changes in the absorbance due to the reaction are shown in Fig. 2 after correction for reaction with materials of construction. Each figure is the average of three experiments and the data are corrected using a linear regression of the absorbance before time zero extrapolated through the points used for initial rate determination. The initial slope of the decay was fit using a linear regression on the first five data points for each reaction condition. The data were converted from absorbance units to mTorr, and the resulting conditional reaction rates in mTorr s⁻¹ are shown in Open in a separate windowFig. 2The normalized absorbance of the 625 cm⁻¹ band in a 5 m path length cell for various partial pressures of UF₆ and water vapor. Water vapor was injected at time = 0 s.Conditional reaction rates of the hydrolysis of gaseous UF₆ in the presence of H₂O vapor

Gender differences in gait kinematics in runners with iliotibial band syndrome

Atypical running gait biomechanics are considered a primary factor in the etiology of iliotibial band syndrome (ITBS). However, a general consensus on the underpinning kinematic differences between runners with and without ITBS is yet to be reached. This lack of consensus may be due in part to three issues: gender differences in gait mechanics, the preselection of discrete biomechanical variables, and/or relatively small sample sizes. Therefore, this study was designed to address two purposes: (a) examining differences in gait kinematics for male and female runners experiencing ITBS at the time of testing and (b) assessing differences in gait kinematics between healthy gender‐ and age‐matched runners as compared with their ITBS counterparts using waveform analysis. Ninety‐six runners participated in this study: 48 ITBS and 48 healthy runners. The results show that female ITBS runners exhibited significantly greater hip external rotation compared with male ITBS and female healthy runners. On the contrary, male ITBS runners exhibited significantly greater ankle internal rotation compared with healthy males. These results suggest that care should be taken to account for gender when investigating the biomechanical etiology of ITBS.     

Hemostatic gene polymorphisms and the prevalence of thrombotic complications in polycythemia vera and essential thrombocythemia.

Patients with polycythemia vera and essential thrombocythemia are at risk for thrombotic and bleeding complications. Currently, no diagnostic test can predict thrombohemorrhagic complications. In a prospective study of 86 patients with polycythemia vera (43 patients) or essential thrombocythemia (43 patients), we examined the possible role of polymorphisms of platelet adhesion receptors [glycoprotein (GP) Ibalpha, GPIa, GPIIIa) and clotting factor II (prothrombin's G20210A mutation) and clotting factor V (Leiden mutation) in determining the risk of thrombotic or bleeding complications. Except for an association between vasomotor symptoms and prothrombin mutation (P < 0.001), no significant correlation between polymorphism of clotting factors and thrombohemorrhagic complications was identified. When the entire patient cohort was considered, the polymorphisms of platelet adhesion receptors were not associated with the risk for thrombotic or bleeding complications. However, among patients with polycythemia vera, the presence of the PlA2 allele of GPIIIa was associated with an increased risk of arterial thrombosis. In view of previous studies linking the presence of the PlA2 allele of GPIIIa to a higher risk for coronary artery thrombosis, our data have physiologic relevance. However, they need to be confirmed in a larger study.     

Right arm ischemia following intentional stent-graft coverage of an anomalous right subclavian artery.

PURPOSE: To report thoracic aortic stent-graft repair in a patient with abnormal aortic arch anatomy. CASE REPORT: An anomalous right subclavian artery was covered with a stent-graft in a 38-year-old woman being treated for a false aneurysm after coarctation repair. The right arm became relatively ischemic, but was viable and managed conservatively. CONCLUSIONS: Aneurysms close to left or aberrant right subclavian arteries can be safely and effectively treated by endoluminal repair without the need for revascularization procedures; ischemic symptoms that develop are often mild and transient.     

The Effect of Radiation on Complication Rates and Patient Satisfaction in Breast Reconstruction using Temporary Tissue Expanders and Permanent Implants

The optimal method of reconstruction following mastectomy for breast cancer patients receiving radiation therapy (RT) is controversial. This study evaluated patient satisfaction and complication rates among patients who received implant‐based breast reconstruction. The specific treatment algorithm analyzed included patients receiving mastectomy and immediate temporary tissue expander (TE), followed by placement of a permanent breast implant (PI). If indicated, RT was delivered to the fully expanded TE. Records of 218 consecutive patients with 222 invasive (85%) or in situ (15%) breast lesions from the Salt Lake City region treated between 1998 and 2009 were retrospectively reviewed, 28% of whom received RT. Median RT dose was 50.4 Gy, and 41% received a scar boost at a median dose of 10 Gy. Kaplan–Meier analyses were performed to evaluate the cumulative incidence of surgical complications, including permanent PI removal. Risk factors associated with surgical events were analyzed. To evaluate cosmetic results and patient satisfaction, an anonymous survey was administered. Mean follow‐up was 44 months (range 6–144). Actuarial 5‐year PI removal rates for non‐RT and RT patients were 4% and 22%, respectively. On multivariate analysis (MVA), the only factor associated with PI removal was RT (p = 0.009). Surveys were returned describing the outcomes of 149 breasts. For the non‐RT and RT groups, those who rated their breast appearance as good or better were 63% versus 62%, respectively. Under 1/3 of each group was dissatisfied with their reconstruction. RT did not significantly affect patient satisfaction scores, but on MVA RT was the only factor associated with increased PI removal. This reconstruction technique may be considered an acceptable option even if RT is needed, but the increased complication risk with RT must be recognized.     

Surgery versus radioiodine therapy as definitive management for graves' disease: the role of patient preference.

BACKGROUND: Thyroidectomy is an option for the definitive management of Graves' disease. The aim of this study was to examine the role of patient preference for selecting surgery as definitive treatment. PATIENTS AND METHODS: This is a retrospective cohort study comprising all patients (n = 63) presenting to a single surgeon for surgical management of Graves' disease over 3 years. Documented reasons for surgery were compared with accepted indications, as well as patients' perceptions as assessed by questionnaire. RESULTS: The most frequent absolute indication was the presence of a large goiter (n = 8; 13%) or associated thyroid nodule (n = 6; 10%). Ophthalmopathy, a relative indication, comprised the largest single group overall (n = 18; 29%); however, a significant number of patients (n = 17; 27%) elected surgery in the absence of a recognized indication. There was strong concordance (73%) between the recorded indication and the patients' survey response. Overall, there was a high level of satisfaction with surgery with 88% of respondents giving a satisfaction score of 7 or greater on a visual analog scale (VAS) (0-10). CONCLUSIONS: One-third of all patients electing surgery as definitive management do so in the absence of a specific indication. Overall, there is a high level of satisfaction with the decision for surgery as definitive management of Graves' disease.