Wetting phenomena are studied for a fibre bundle consisting of three parallel cylinders of radius b. Two types of long liquid column (a disintegrated and a channel-filling column) and a state akin to the unduloid can form, depending on whether the cylinder-cylinder separation, 2d, is larger or smaller than certain critical values. The dimensionless threshold values d/b have been calculated, when gravity can be neglected and the liquid-fibre contact angle is zero. The threshold value for the morphological transition between disintegrated columns and channel-filling columns occurs for (d/b)tr1 = 0.07869, and the transition between channel-filling column and unduloid sets in when (d/b)tr2 = 2.85337. The existence of the first type of morphological transition is validated by computer simulation based on the Ising model and the Monte Carlo method, as well as by experiments carried out with steel cylinders and epoxy resin.

• MeSH
• absorpce MeSH
• hygienické absorpční vložky * MeSH
• počítačová simulace MeSH
• povrchové vlastnosti MeSH
• reologie metody   MeSH
• smáčivost MeSH
• teoretické modely * MeSH
• testování materiálů metody   MeSH
• textilie * MeSH
• vyrobené materiály * MeSH
• Publikační typ
• časopisecké články MeSH
• hodnotící studie MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH
• validační studie MeSH

The transport of 3H+ (as HTO) and 36Cl- (as Na36Cl) was investigated in the dynamic system, i.e., in the columns filled with crushed pure granite and fracture infill of various grain sizes. The aim of column experiments was to determine important transport parameter, such as the retardation, respectively distribution coefficients, Peclet numbers and hydrodynamic dispersion coefficients. Furthermore, the research was focused to quantification of the effect of grain size on migration of studied radionuclides. The experimental breakthrough curves were fitted by a model based on the erfc-function, assuming a linear reversible equilibrium sorption/desorption isotherm, and the above mentioned transport parameters were determined. The results showed that influence of grain size on sorption of 3H+ and 36Cl- was negligible. Retardation and distribution coefficients of both tracers converged to one and zero, respectively, in case of all fractions of crushed granite and infill material. Generally, the presumed ion exclusion of 36Cl in anionic form was proved under given conditions, only very weak one seems to exist in a case of infill material. In principal, both radionuclides behaved as non-sorbing, conservative tracers. On the other hand, the influence of grain size on Peclet numbers value and on dispersion coefficient was observed for both crystalline materials, namely in agreement with theoretical suppositions that the values of Peclet numbers decrease with increasing grain size and values of dispersion coefficient increase.

• Klíčová slova
• Crushed granite, Dynamic conditions, Groundwater, HTO, Modeling, Na36Cl,
• Publikační typ
• časopisecké články MeSH

The identification of a suitable stationary phase in supercritical fluid chromatography (SFC) is a major source of difficulty for those with little experience in this technique. Several protocols have been suggested for column classification in high-performance liquid chromatography (HPLC), gas chromatography (GC), and SFC. However, none of the proposed classification schemes received general acceptance. A fair way to compare columns was proposed with the sum of ranking differences (SRD). In this project, we used the retention data obtained for 86 test compounds with varied polarity and structure, analyzed on 71 different stationary phases encompassing the full range in polarity of commercial packed columns currently available to the SFC chromatographer, with a single set of mobile phase and operating conditions (carbon dioxide-methanol mobile phase, 25°C, 150bar outlet pressure, 3ml/min). First, a reference column was selected and the 70 remaining columns were ranked based on this reference column and the retention data obtained on the 86 analytes. As these analytes previously served for the calculation of linear solvation energy relationships (LSER) on the 71 columns, SRD ranks were compared to LSER methodology. Finally, an external comparison based on the analysis of 10 other analytes (UV filters) related the observed selectivity to SRD ranking. Comparison of elution orders of the UV filters to the SRD rankings is highly supportive of the adequacy of SRD methodology to select similar and dissimilar columns.

• Klíčová slova
• Column classification, Method development, Selectivity, Stationary phases, Supercritical fluid chromatography,
• MeSH
• methanol MeSH
• oxid uhličitý MeSH
• superkritická fluidní chromatografie metody   MeSH
• tlak MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• methanol MeSH
• oxid uhličitý MeSH

A bubble column fitted with an ejector has been tested for its physical and biological performance. The axial diffusion coefficient of the liquid phase in the presence of electrolytes and ethanol was measured by a stimulus-response technique with subsequent evaluation by means of a diffusion model. In contrast to ordinary bubble columns, the coefficient of axial mixing is inversely dependent on the superficial air velocity. The liquid velocity acts in an opposite direction to the backmixing flow in the column. The measurement of volumetric oxygen transfer coefficient in the presence of electrolytes and ethanol was performed using a dynamic gassing-in method adapted for a column. The data were correlated with the superficial air and liquid velocities, total power input, and power for aeration and mixing; the economy coefficient of oxygen transfer was used for finding an optimum ratio of power for aeration and pumping. Growth experiments with Candida utilis on ethanol confirmed some of the above results. Biomass productivity of 2.5 g L(-1) h(-1) testifies about a good transfer capability of the column. Columns fitted with pneumatic and/or hydraulic energy input may be promising for aerobic fermentations considering their mass transfer and mixing characteristics.

• Publikační typ
• časopisecké články MeSH

Laboratory column experiments were conducted to evaluate the effect of previously described silica coating method on the transport of nanoscale zero-valent iron (nZVI) in porous media. The silica coating method showed the potential to prevent the agglomeration of nZVI. Transport experiments were conducted using laboratory-scale sand-packed columns at conditions that were very similar of natural groundwater. Transport properties of non-coated and silica-coated nZVI are investigated in columns of 40 cm length, which were filled with porous media. A suspension was injected in three different Fe particle concentrations (100, 500, and 1000 mg/L) at flow 5 mL/min. Experimental results were compared using nanoparticle attachment efficiency and travel distances which were calculated by classical particle filtration theory. It was found that non-coated particles were essentially immobile in porous media. In contrast, silica-coated particles showed significant transport distances at the tested conditions. Results of this study suggest that silica can increase nZVI mobility in the subsurface.

• Klíčová slova
• Nanoscale zero-valent iron, column experiments, mobility, porous media, remediation,
• MeSH
• nanočástice chemie   MeSH
• oxid křemičitý chemie   MeSH
• poréznost MeSH
• regenerace a remediace životního prostředí metody   MeSH
• teoretické modely MeSH
• velikost částic MeSH
• železo chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• oxid křemičitý MeSH
• železo MeSH

The remediation of legacy metal(loid) contaminated soils in-situ relies on the addition of [organic] amendments to reduce the mobility and bioavailability of metal(loid)s, improve soil geochemical parameters and restore vegetation growth. Two vermicomposts of food and animal manure waste origin (V1 and V2) were amended to an arsenic (As) and copper (Cu) contaminated mine soil (≤1500 mg kg-1). Leaching columns and pot experiments evaluated copper and arsenic in soil pore waters, as well as pH, dissolved organic carbon (DOC) and phosphate (PO43-) concentrations. The uptake of As and Cu to ryegrass was also measured via the pot experiment, whilst recovered biochars from the column leaching test were measured for metal sorption at the termination of leaching. Vermicompost amendment to soil facilitated ryegrass growth which was entirely absent from the untreated soil in the pot test. All amendment combinations raised pore water pH by ∼4 units. Copper concentrations in pore waters from columns and pots showed steep reductions (∼1 mg L-1), as a result of V1 & V2 compared to untreated soil (∼500 mg L-1). Combined with an increase in DOC and PO43-, As was mobilised an order of magnitude by V1. Biochar furthest reduced Cu in pore waters from the columns to <0.1 mg L-1, as a result of surface sorption. The results of this study indicate that biochar can restrict the mobility of Cu from a contaminated mine soil after other amendment interventions have been used to promote revegetation. However, the case of As, biochar cannot counter the profound impact of vermicompost on arsenic mobility.

• Klíčová slova
• Arsenic, Biochar, Copper, Mining soil, Vermicompost,
• MeSH
• arsen * analýza   MeSH
• dřevěné a živočišné uhlí MeSH
• hornictví MeSH
• jílek * MeSH
• kovy MeSH
• látky znečišťující půdu * analýza   MeSH
• měď analýza   MeSH
• půda MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• arsen * MeSH
• dřevěné a živočišné uhlí MeSH
• kovy MeSH
• látky znečišťující půdu * MeSH
• měď MeSH
• půda MeSH

The fate of pesticides in tropical soils is still not understood as well as it is for soils in temperate regions. In this study, water flow and transport of bromide tracer and five pesticides (atrazine, imazaquin, sulfometuron methyl, S-metolachlor, and imidacloprid) through an undisturbed soil column of tropical Oxisol were analyzed using a one-dimensional numerical model. The numerical model is based on Richards' equation for solving water flow, and the advection-dispersion equation for solving solute transport. Data from a laboratory column leaching experiment were used in the uncertainty analysis using a global optimization methodology to evaluate the model's sensitivity to transport parameters. All pesticides were found to be relatively mobile (sorption distribution coefficients lower than 2 cm(3) g(-1)). Experimental data indicated significant non-conservative behavior of bromide tracer. All pesticides, with the exception of imidacloprid, were found less persistent (degradation half-lives smaller than 45 days). Three of the five pesticides (atrazine, sulfometuron methyl, and S-metolachlor) were better described by the linear kinetic sorption model, while the breakthrough curves of imazaquin and imidacloprid were more appropriately approximated using nonlinear instantaneous sorption. Sensitivity analysis suggested that the model is most sensitive to sorption distribution coefficient. The prediction limits contained most of the measured points of the experimental breakthrough curves, indicating adequate model concept and model structure for the description of transport processes in the soil column under study. Uncertainty analysis using a physically-based Monte Carlo modeling of pesticide fate and transport provides useful information for the evaluation of chemical leaching in Hawaii soils.

• Klíčová slova
• Flow interruption, Herbicides, Latin hypercube sampling, Miscible displacement experiment, Monte Carlo, Parameter sensitivity,
• MeSH
• bromidy chemie   MeSH
• chemické látky znečišťující vodu analýza   MeSH
• herbicidy chemie   MeSH
• insekticidy chemie   MeSH
• látky znečišťující půdu chemie   MeSH
• pohyb vody MeSH
• teoretické modely * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Havajské ostrovy MeSH
• Názvy látek
• bromidy MeSH
• chemické látky znečišťující vodu MeSH
• herbicidy MeSH
• insekticidy MeSH
• látky znečišťující půdu MeSH

A programmed temperature vaporizer (PTV) injection technique has been recently implemented in our laboratory. In present paper its performance is compared with other GC injection techniques commonly used in trace analysis of organic contaminants. Twenty-six pesticides representing different chemical classes were selected for the study. This group comprised compounds typically subjected to discrimination in the injection port of the gas chromatograph, e.g., polar organophosphorus pesticides and thermolabile carbamates. In the first set of experiments standards in pure solvent were injected into GC systems employing different types of injection, i.e., (i) on-column, (ii) pulsed splitless, (iii) PTV solvent split, (iv) PTV splitless, and the responses of analytes were compared. Discrimination of troublesome compounds was significantly decreased with the application of PTV solvent split injection. In the second set of experiments repetitive injections of purified wheat samples were performed, with aims to evaluate the long-term stability of responses, as well as matrix effects in different stages of system contamination for each injection technique. The tolerance of the GC system to co-injected matrix components was increased in the order: on-column

• MeSH
• chromatografie plynová metody   MeSH
• pšenice chemie   MeSH
• rezidua pesticidů analýza   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• rezidua pesticidů MeSH

Recent clinical studies have demonstrated that a midline lesion of the dorsal columns (DC, limited midline myelotomy) reduces pain of visceral origin in patients with pelvic cancer. Animal experiments showed that a DC lesion leads to decreased activation of thalamic neurons by visceral stimuli, lowers the impact of noxious colon stimulation in behavioral tests and suggested that the effect is mediated mainly by postsynaptic DC neurons. In the present experiments we examined the effect of bilateral DC or ventrolateral (VL) spinal cord lesions on visceromotor reflex EMG activity evoked by graded colorectal distention (30, 60, 80 mmHg) under control conditions and after colon inflammation with mustard oil. The colon inflammation increased significantly the visceromotor responses so that the response to a 30 mmHg distention was larger than that produced by 80 mmHg before inflammation. The DC lesion did not affect the visceromotor reflex response under control conditions but reduced the increased responses after colon inflammation back to control levels and prevented the potentiation of the reflex responses by colon inflammation when performed before the inflammation. Our results suggest that the role of the DC pathway in transmission of visceral pain is augmented under inflammatory conditions when symptoms of visceral allodynia and hyperalgesia may be present. The VL lesions eliminated the visceromotor reflex, presumably by interrupting a facilitatory pathway that involves the brain stem.

• MeSH
• buňky zadních rohů míšních fyziologie   MeSH
• elektromyografie metody   MeSH
• katetrizace MeSH
• kolitida patofyziologie   MeSH
• kolon inervace   patologie   patofyziologie   MeSH
• krysa rodu Rattus MeSH
• nuclei ventrales thalami MeSH
• potkani Sprague-Dawley MeSH
• rektum inervace   patologie   patofyziologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, P.H.S. MeSH

PURPOSE OF THE STUDY: Percutaneous fluoroscopy-assisted fixation of acetabular fractures is not a widely used technique. Its advantage lies particularly in percutaneous placement of screws in the anterior column of the acetabulum. The operative procedure is described and the first experience of the authors with this minimally invasive technique at their department is reported. MATERIAL: Between December 2007 and April 2009, 10 fractures of the anterior column of the acetabulum were treated by percutaneous stabilisation in 10 patients. There were six men and four women aged 25 to 76 (average, 46) years. Retrograde screw fixation was used in three, anterograde screw fixation in two and anterograde screw placement following retrograde guide wire insertion in five patients. METHODS: The minimally invasive method of acetabular stabilization using 6.5-mm or 7.3-mm cannulated screws was facilitated by the use of intra-operative fluoroscopic imaging. Following fracture reduction, a percutaneous guide wire, aided by a C-arm, was placed in the upper pubic ramus and the anterior column of the acetabulum in either an anterograde or a retrograde mode. Subsequently, a traction cannulated screw was inserted. When anterograde guide wire placement was difficult to do, the retrograde guide wire placement was used for anterograde screw insertion. The quality of fracture reduction and the placement of screw were evaluated by a post-operative CT examination. RESULTS: The average follow-up was 11 (range, 2-19) months. The average operative time necessary for percutaneous screw insertion in the anterior column of the acetabulum was 26.4 (range, 15-45) min, and the average X-ray exposure time for the screw placement was 3 min and 13 sec (range, 40-448 sec). The average time needed for screw insertion following the retrograde guide wire was 2 min and 30 sec (range, 40-242 sec). The average post-operative fragment dislocation leading to incongruency was 1.3 mm (range, 0-4 mm). The results of reduction assessed as excellent (<2 mm) and poor (>or=2 mm) were achieved in six and four patients, respectively. No screw malplacement was recorded. Post-operative infectious complications occurred in one (10 %) patient. DISCUSSION: Important factors for avoidance of intra-operative complications included a thorough pre-operative planning on the basis of CT diagnostic examination, meeting the indication criteria and using a safe stabilisation technique. However, the percu- taneous fluoroscopy-assisted method requires a longer exposure to X-ray than do the techniques utilising computerised navigation. The occurrence of infectious complications was not lower than with the use of open reduction and internal fixation methods. CONCLUSIONS: After the operative technique has been mastered, the minimally invasive method of osteosynthesis is likely to become a method of choice for certain kinds of acetabular fractures. The current, most frequent indications are minimally displaced transverse fractures, T-shaped fractures and anterior column acetabular fractures. A limiting factor of this technique is reduction. It is certain that further evolution of this technique and its more frequent use will be associated with computerised navigation.

• MeSH
• acetabulum diagnostické zobrazování   zranění   chirurgie   MeSH
• dospělí MeSH
• fluoroskopie MeSH
• fraktury kostí diagnostické zobrazování   chirurgie   MeSH
• intervenční radiografie MeSH
• lidé středního věku MeSH
• lidé MeSH
• senioři MeSH
• vnitřní fixace fraktury metody   MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH