Homogeneous water nucleation in carbon dioxide-nitrogen mixtures: Experimental study on pressure and carrier gas effects.

New homogeneous nucleation experiments are presented at 240 K for water in carrier gas mixtures of nitrogen with carbon dioxide molar fractions of 5%, 15%, and 25%. The pulse expansion wave tube is used to test three different pressure conditions, namely, 0.1, 1, and 2 MPa. In addition, a restricted series of nucleation experiments is presented for 25% carbon dioxide mixtures at temperatures of 234 and 236 K at 0.1 MPa. As pressure and carbon dioxide content are increased, the nucleation rate increases accordingly. This behavior is attributed to the reduction in the water surface tension by the adsorption of carrier gas molecules. The new data are compared with theoretical predictions based on the classical nucleation theory and on extrapolations of empirical surface tension data to the supercooled conditions at 240 K. The extrapolation is carried out on the basis of a theoretical adsorption/surface tension model, extended to multi-component mixtures. The theoretical model appears to strongly overestimate the pressure and composition dependence. At relatively low pressures of 0.1 MPa, a reduction in the nucleation rates is found due to an incomplete thermalization of colliding clusters and carrier gas molecules. The observed decrease in the nucleation rate is supported by the theoretical model of Barrett, generalized here for water in multi-component carrier gas mixtures. The temperature dependence of the nucleation rate at 0.1 MPa follows the scaling model proposed by Hale [J. Chem. Phys. 122, 204509 (2005)].

Homogeneous water nucleation: Experimental study on pressure and carrier gas effects.

Homogeneous nucleation of water is investigated in argon and in nitrogen at about 240 K and 0.1 MPa, 1 MPa, and 2 MPa by means of a pulse expansion wave tube. The surface tension reduction at high pressure qualitatively explains the observed enhancement of the nucleation rate of water in argon as well as in nitrogen. The differences in nucleation rates for the two mixtures at high pressure are consistent with the differences in adsorption behavior of the different carrier gas molecules. At low pressure, there is not enough carrier gas available to ensure the growing clusters are adequately thermalized by collisions with carrier gas molecules so that the nucleation rate is lower than under isothermal conditions. This reduction depends on the carrier gas, pressure, and temperature. A qualitative agreement between experiments and theory is found for argon and nitrogen as carrier gases. As expected, the reduction in the nucleation rates is more pronounced at higher temperatures. For helium as the carrier gas, non-isothermal effects appear to be substantially stronger than predicted by theory. The critical cluster sizes are determined experimentally and theoretically according to the Gibbs-Thomson equation, showing a reasonable agreement as documented in the literature. Finally, we propose an empirical correction of the classical nucleation theory for the nucleation rate calculation. The empirical expression is in agreement with the experimental data for the analyzed mixtures (water-helium, water-argon, and water-nitrogen) and thermodynamic conditions (0.06 MPa-2 MPa and 220 K-260 K).

Co(II)-Based single-ion magnets with 1,1'-ferrocenediyl-bis(diphenylphosphine) metalloligands.

Herein, we report on investigations of magnetic and spectroscopic properties of three heterobimetallic Fe(ii)-Co(ii) coordination compounds based on the tetracoordinate {CoP2X2} core encapsulated by dppf metalloligand, where X = Cl (1), Br (2), I (3), dppf = 1,1'-ferrocenediyl -bis(diphenylphosphine). The analysis of static magnetic data has revealed the presence of axial magnetic anisotropy in compounds (1) and (2) and this was further confirmed by high-frequency electron spin resonance (HF-ESR) spectroscopy. Dynamic magnetic data confirmed that (1) and (2) behave as field-induced Single-Ion Magnets (SIMs). Together with bulk studies, we have also tested the possibility of depositing (2) as thick films on Au(111), glass, and polymeric acetate by drop-casting as well as thermal sublimation, a key aspect for the development of future devices embedding these magnetic objects.

Relative density and isobaric expansivity of cold and supercooled heavy water from 254 to 298 K and up to 100 MPa.

A dual-capillary apparatus was developed for highly accurate measurements of density of liquids, including the supercooled liquid region. The device was used to determine the density of supercooled heavy water in the temperature range from 254 K to 298 K at pressures ranging from atmospheric to 100 MPa, relative to density at reference isotherm 298.15 K. The measurements of relative density were reproducible within 10 ppm, and their expanded (k = 2) uncertainty was within 50 ppm. To obtain absolute values of density, thermodynamic integration was performed using recent accurate speed of sound measurements in the stable liquid region. An empirical equation of state (EoS) was developed, giving specific volume as a rational function of pressure and temperature. The new experimental data are represented by EoS within their experimental uncertainty. Gibbs energy was obtained by EoS integration allowing computation of all thermodynamic properties of heavy water using Gibbs energy derivatives. Although based on data in relatively narrow temperature and pressure ranges, the developed EoS shows an excellent agreement with literature data for densities, isothermal compressibilities, and isobaric expansivities of deeply supercooled heavy water. The curvature of the thermodynamic surface steeply increases toward low temperatures and low pressures, thus supporting the existence of the hypothesized liquid-liquid coexistence boundary in a close vicinity of existing experimental data.

Surgical pleth index: prospective validation of the score to predict moderate-to-severe postoperative pain.

BACKGROUND: Reported outcome benefits after surgical pleth index (SPI, GE Healthcare, Helsinki, Finland) guided anaesthesia are conflicting. One potential explanation may be the lack of evidence for the selection of meaningful SPI target values. A recently published trial found an SPI cut-off of 30 as a 'best-fit' to predict moderate-to-severe acute postoperative pain. This prospective trial was designed to validate this target and to investigate the influence of patient age on SPI in this context. METHODS: After ethics approval, 200 patients undergoing non-emergency surgery were enrolled. Data related to SPI, heart rate (HR), and mean arterial pressure (MAP) were recorded for the last 5 min of surgery, just before arousal. After admission to recovery, pain scores (numeric rating scale [NRS], 0-10) were obtained every 5 min for 15 min. RESULTS: The data of 196 patients were analysed. Receiver-operating curve analysis showed a cut-off SPI value of 29 to be the optimum intraoperative target to discriminate between NRS 0-3 and 4-10. This confirms the 'best fit' cut-off for SPI published previously. Though still superior to HR and MAP, the sensitivity and specificity of the SPI were only poor. Age had no influence on the predictive accuracy of SPI. CONCLUSIONS: An SPI of approximately 30 was confirmed as having the best sensitivity/specificity to predict moderate-to-severe pain in the postanaesthesia care unit. However, the predictive accuracy was overall poor and not influenced by patient age. CLINICAL TRIAL REGISTRATION: ACTRN12617001475336.

Branched pedal bypass in the treatment of critical limb ischemia - a single center experience.

INTRODUCTION: Pedal bypass is a therapeutic option for limb salvage in critical limb ischemia. METHOD: Retrospective analysis of 20 patients who underwent either simple (14 patients) or branched (6 patients) pedal bypass in a single center and had at least one postoperative follow-up. In patients with branched pedal bypass, the main trunk was connected to the pedal artery of better quality and the side branch to an artery on the opposite side of the foot. The main trunk was constructed as a reverse saphenous bypass in all patients with branched bypass. From patients with simple bypass, nine had reverse saphenous graft, three had an allograft, one patient had in situ saphenous graft, and one PTFE prosthesis. RESULTS: The difference in the operation time was not significant. One patient with simple bypass required reoperation for wound bleeding and there was one case of perioperative mortality in the same group. The difference between the groups in the primary or secondary patency rates, limb salvage and overall survival was not significant. CONCLUSIONS: We did not find any significant difference in patency rates, limb salvage, or perioperative complications between patients with simple and branched pedal bypass in our cohort. We believe that the anticipated benefits of constructing an additional branch are masked by the disadvantageous presence of an additional anastomosis. Adoption of a branched pedal bypass may therefore require further improvements - perhaps the utilization of a branched saphenous graft. Key words:  critical limb ischemia - peripheral arterial disease - bypass - revascularization - amputation.

Surgical pleth index: prediction of postoperative pain and influence of arousal.

BACKGROUND: There are conflicting reports concerning the outcome after anaesthesia guided by the surgical pleth index (SPI; GE Healthcare, Helsinki, Finland). One potential explanation may be the lack of evidence for the selection of SPI cut-off values. The aim of this trial was to investigate the correlation between SPI, arousal, and postoperative pain and to define a cut-off value for SPI to predict moderate-to-severe pain. METHODS: After obtaining ethical approval and written informed consent, 70 patients undergoing non-emergency surgery were enrolled. Data relating to SPI, heart rate, mean arterial pressure, and state entropy were recorded every 10 s for the last 10 min of surgery (state entropy <60 at all times). Subsequently, recordings continued during the phase of arousal. After recovery room admission, pain scores (numerical rating scale 0-10) were obtained every 3 min for 15 min. RESULTS: Data from 65 patients were analysed. Receiver-operating characteristic curve analysis revealed an optimal intraoperative cut-off SPI value of 30 to discriminate between numerical rating scale scores 0-3 and 4-10. For this value, the negative and positive predictive values to discriminate between numerical rating scale scores 0-3 and 4-10 were 50 and 89.7%, respectively. The SPI was significantly affected by arousal, and SPI scores obtained during this phase were not predictive of postoperative pain. CONCLUSIONS: Surgical pleth index values are predictive of postoperative pain only if obtained before patient arousal. In contrast to previous studies, a relatively low SPI, >30, appears to predict pain with a high positive predictive value and may therefore be suggested for future studies of SPI-guided anaesthesia. CLINICAL TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry: ACTRN12615000804583.

A Mn(iii) single ion magnet with tridentate Schiff-base ligands.

Single ion magnet behaviour is reported for a mononuclear Mn(iii) ion with tridentate Schiff-base ligands which exhibits a tetragonal Jahn-Teller elongation along the Namine-Mn-Namine axis and crystallises with two crystallographically distinct Mn(iii) cations (unit A and unit B). While magnetic measurements show a large and negative axial zero-field splitting (D = -4.73 cm(-1)), HF-EPR reveal two distinct large axial Ds (D = -4.60 cm(-1) for unit A and D = -4.18 cm(-1) for unit B), thus resulting in the largest D known to date for a Mn(iii) single ion magnet. AC magnetic measurements at 2000 Oe allowed determination of the energy barrier for spin reversal (10.19 K) and spin reversal relaxation time (1.476 × 10(-6) s) for the Mn(iii) ion. Computational studies were used to characterise the electronic structure and substantiate the zero field splitting in the Mn(iii) complex.

Photoelectric detection of electron spin resonance of nitrogen-vacancy centres in diamond.

The readout of negatively charged nitrogen-vacancy centre electron spins is essential for applications in quantum computation, metrology and sensing. Conventional readout protocols are based on the detection of photons emitted from nitrogen-vacancy centres, a process limited by the efficiency of photon collection. We report on an alternative principle for detecting the magnetic resonance of nitrogen-vacancy centres, allowing the direct photoelectric readout of nitrogen-vacancy centres spin state in an all-diamond device. The photocurrent detection of magnetic resonance scheme is based on the detection of charge carriers promoted to the conduction band of diamond by two-photon ionization of nitrogen-vacancy centres. The optical and photoelectric detection of magnetic resonance are compared, by performing both types of measurements simultaneously. The minima detected in the measured photocurrent at resonant microwave frequencies are attributed to the spin-dependent ionization dynamics of nitrogen-vacancy, originating from spin-selective non-radiative transitions to the metastable singlet state.

On the effect of pressure and carrier gas on homogeneous water nucleation.

Homogeneous nucleation rates of water droplets were measured at a nucleation temperature close to 240 K in a Pulse-Expansion Wave Tube (PEWT). Several measures were taken to improve the data obtained with the PEWT. For instance, the molar water vapor fraction was determined with three independent techniques. The resulting standard uncertainty of the supersaturation was within 1.8%. Results are given for water nucleation in helium at 100 kPa and at 1000 kPa and in nitrogen at 1000 kPa. Two trends were observed: (i) the values of the nucleation rate of water in helium at 1000 kPa are slightly but significantly higher (factor 3) than its values at 100 kPa and (ii) nucleation rates of water in nitrogen at 1000 kPa are clearly higher (factor 10) than in helium at the same pressure. It is argued that the explanation of the two observed trends is different. For case (i), it is the insufficient thermalization of the growing water clusters in helium at the lowest pressure that has a reducing effect on the nucleation rate, although a full quantitative agreement has not yet been reached. For case (ii), thermal effects being negligible, it is the pressure dependency of the surface tension, much stronger for nitrogen than for helium, that explains the trends observed, although also here a full quantitative agreement has not yet been achieved.

[Multiple sequence revascularization of infrapopliteal arteries in the management of critically ischemic extremity]. / Vícenásobná sekvencní revaskularizace infrapopliteálních tepen pri záchrane kriticky ischemick koncetiny.

AIM OF THE STUDY: Most cases of distal bypasses closures are caused by reduced blood flow within the affected peripheral vasculature, resulting in corresponding reduction in the graft's blood supply. The authors use multiple, sequence, Y grafting and bridge grafting procedures on crural and pedal arteries, in order to improve the above hemodynamic features. Furthermore, the techniques facilitate better circulation within larger extremity regions. METHODS: From April 2007 to January 2009, the authors completed a total of 38 sequence bypass procedures. The procedures included 30 Y graft procedures with peripheral anastomoses with crural arteries, 4 Y graft procedures with peripheral anastomoses with pedal arteries and 4 bridge graft procedures. Y grafting is a technique, in which a classical distal bypass is formed, to which another bypass is attached end-to-side in an acute angle. The composite bypasses form a reversed letter Y. Its distal branches anastomose with crural or pedal arteries. Bridge grafting is a technique, where a short bypass between crural arteries is formed, using a venous graft with removed valves, allowing for a two-way flow. The distal anastomosis is attached end-to-side. All the above vascular reconstructions were indicated for critical extremity ischemia, some patients had a history of endovascular reinterventions. In the patient group, autologous veins were used in 20 reconstructions, while PTFE prostheses were used in 10 reconstructions. Clinical and sonographic examinations were performed on discharge, followed by check ups at 1,3, 6 and 12 months. RESULTS: The follow up period in patients with Y graft reconstructions was 6-20 months (mean duration of 12 months). Two patients underwent major amputation, required for bypass closures, 3 subjects exited with patent vascular reconstructions, their deaths were not related to the procedure. The authors recorded 4 bypass closures, with the main trunk patency. Primary/secondary 30-day patency rate was 90%/97%, the long-term patency rate was 93%. CONCLUSION: The vascular reconstructions results are similar to those presented in literature. In order to perform more accurate assessment of individual revascularization variants, long- term follow up studies, including randomized studies, are required.

[Outcomes of combined surgical and endovascular treatment of the venous thoracic outlet syndrome during 2000-2007 in the IInd Surgical Clinic of the VFN (General Faculty Hospital) and 1. LF UK (First Medical Faculty, Charles University) in Prague]. / Výsledky kombinované chirurgické a endovaskulární lécby zilního thoracic outlet syndromu v letech 2000-2007 na II. chirurgické klinice VFN a 1. LF UK v Praze.

OBJECTIVES: Between 2000-2007 we performed 31 surgical procedures for thoracic outlet syndrome, two patients underwent bilateral procedure. METHODS AND RESULTS: 26 patients had venous TOS, 4 neurovascular and 1 arterial TOS. Rib resection and scalenotomy were performed at 23 patients, rib resection, scalenotomy and deliberation at 9 patients, in one case re-operation. CONCLUSION: 76% patients were without difficulties after combined endovascular and surgical procedures.

Gradient theory computation of the radius-dependent surface tension and nucleation rate for n-nonane clusters.

The Van der Waals-Cahn-Hilliard gradient theory (GT) is applied to determine the structure and the work of formation of clusters in supersaturated n-nonane vapor. The results are analyzed as functions of the difference of pressures of the liquid phase and vapor phase in chemical equilibrium, which is a measure for the supersaturation. The surface tension as a function of pressure difference shows first a weak maximum and then decreases monotonically. The computed Tolman length is in agreement with earlier results [L. Granasy, J. Chem. Phys. 109, 9660 (1998)] obtained with a different equation of state. A method based on the Gibbs adsorption equation is developed to check the consistency of GT results (or other simulation techniques providing the work of formation and excess number of molecules), and to enable an efficient interpolation. A cluster model is devised based on the density profile of the planar phase interface. Using this model we analyze the dependency of the surface tension on the pressure difference. We find three major contributions: (i) the effect of asymmetry of the density profile resulting into a linear increase of the surface tension, (ii) the effect of finite thickness of the phase interface resulting into a negative quadratic term, and (iii) the effect of buildup of a low-density tail of the density profile, also contributing as a negative quadratic term. Contributions (i)-(iii) fully explain the dependency of the surface tension on the pressure difference, including the range relevant to nucleation experiments. Contributions (i) and (ii) can be predicted from the planar density profile. The work of formation of noncritical clusters is derived and the nucleation rate is computed. The computed nucleation rates are closer to the experimental nucleation rate results than the classical Becker-Döring theory, and also the dependence on supersaturation is better predicted.

Effects of in-season (5 weeks) creatine and pyruvate supplementation on anaerobic performance and body composition in American football players.

The purpose of this investigation was to study the efficacy of two dietary supplements on measures of body mass, body composition, and performance in 42 American football players. Group CM (n = 9) received creatine monohydrate, Group P (n = 11) received calcium pyruvate, Group COM (n = 11) received a combination of calcium pyruvate (60%) and creatine (40%), and Group PL received a placebo. Tests were performed before (T1) and after (T2) the 50 week supplementation period, during which the subjects continued their normal training schedules. Compared to P and PL, CM and COM showed significantly greater increases for body mass, lean body mass, 1 repetition maximum (RM) bench press, combined 1 RM squat and bench press, and static vertical jump (SVJ) power output. Peak rate of force development for SVJ was significantly greater for CM compared to P and PL. Creatine and the combination supplement enhanced training adaptations associated with body mass/composition, maximum strength, and SVJ; however, pyruvate supplementation alone was ineffective.

Comparison of spinal and epidural anesthesia for patients younger than 50 years of age.

To evaluate the respective clinical value of spinal anesthesia with 24-gauge Sprotte needles and epidural anesthesia for younger subjects, 202 patients younger than 50 yr were assigned randomly to undergo one of these two techniques for orthopedic, vascular, urologic, or plastic surgery. Failed blocks occurred in 5% in each group. Spinal anesthesia resulted in significantly less time to achieve sufficient spread of block; a significantly lower incidence of incomplete sensory block at level L5/S1, incomplete motor block, and pain during surgery; and a significantly lower incidence of postlumbar puncture backache (11% vs 30% after epidural anesthesia). The incidence of postdural puncture headache (PDPH) in the spinal and epidural groups was 7% and 4%, respectively (P = not significant), and patient satisfaction was 97% and 93% (P = not significant). Our results demonstrate the effectiveness of both techniques in younger patients, but show that the spinal technique is associated with fewer limitations, suggesting that factors other than PDPH should be considered when choosing between these two techniques.

Different regulation of adrenocorticotropin and cortisol secretion in young, mentally healthy elderly and patients with senile dementia of Alzheimer's type.

Previous studies suggest that an alteration of the neuroendocrine system may particularly occur in senile dementia of Alzheimer's type (SDAT). In the present study the reactivity of the hypophyseal-adrenocortical axis (HPA) in the elderly was assessed by hormonal stimulation of the hypophysis. Twelve young men (aged 21-24 yr), 15 mentally healthy elderly (aged 65-90 yr), and 12 patients with SDAT (aged 60-84 yr) received an iv bolus injection containing 50 micrograms CRH and 0.5 IU lysine vasopressin after a baseline period of 2 h. ACTH, cortisol, and dehydroepiandrosterone secretion was monitored over a period of 2 h before and after the injection. The baseline ACTH concentrations were increased in both groups of elderly, the baseline cortisol levels were not different in either group. The peak ACTH and cortisol levels were significantly elevated in the mentally healthy elderly, whereas senile demented patients showed a rise comparable with that in the young subjects. Moreover, in the demented patients the post-stimulus decline in plasma ACTH levels seemed to be delayed. Dehydroepiandrosterone was significantly lowered in subjects of all ages. Our results demonstrate an enhanced reactivity of the HPA in mentally healthy elderly. This is possibly due to a diminished sensitivity of the feedback regulation to glucocorticoids. However, SDAT patients had, compared to healthy elderly subjects, an attenuated response to CRH/lysine vasopressin and a prolonged ACTH secretion, indicating alterations of the HPA in this disease.

[An adapter for the intratracheal administration of a bronchodilator in intubated patients]. / Adapter zur intratrachealen Applikation eines Bronchodilatators bei intubierten Patienten.

To relieve intraoperative bronchospasm, bronchodilators are often given via endotracheal tube. Most anesthetic adapters for dose-metered inhalers deliver the agent into the anesthesia circuit outside the tube. An unpredictable loss of drug due to sedimentation on the inner wall of the tube results. A simple and cost-effective device for delivering the agent near the tip of the tube is presented.

Surgical procedure and results of implantation of the Czech cochlear neuroprosthesis.

A special surgical procedure was developed for the implantation of the Czech single-channel extracochlear neuroprosthesis. The implantation was performed in four adult, postlingually deaf subjects. In one patient a successful reimplantation was performed. The authors assess the implant patients' ability to differentiate changes in simple stimulation signals.

[The present state of implantations of cochlear neuroprostheses worldwide]. / Soucasný stav implantací kochleárních neuroprotéz ve svete.

Cochlear implants provide the patient with acoustic perceptions. The quality of these perceptions varies individually and a technically more complicated implant does not imply a better quality of the achieved acoustic perceptions. The authors submit an account of the present state of cochlear implants on a world-wide scale as well as on the electrophysiological background of implantations, the type of electrodes, processing of the acoustic signal and surgical procedures. Development of the implant is an interdisciplinary problem in which otologists, audiologists, experts in electronics, electrophysiologists, phoniatrists and psychologists participate. The work was implemented during the preparation of the Czech single-channel electrocochlear neuroprosthesis.