Monitoring of threo-methylphenidate enantiomers in oral fluid by capillary electrophoresis with head-column field-amplified sample injection

Threo-methylphenidate is a chiral psychostimulant drug widely prescribed to treat attention-deficit hyperactivity disorder in children and adolescents. An enantioselective CE-based assay with head-column field-amplified sample stacking for analysis of threo-methylphenidate enantiomers in liquid/liquid extracts of oral fluid is described. Analytes are electrokinetically injected across a short water plug placed at the capillary inlet and become stacked at the interface between plug and buffer. Enantiomeric separation occurs within a few minutes in a pH 3.0 phosphate/triethanolamine buffer containing 20 mg/mL (2-hydroxypropyl)-β-CD as chiral selector. The assay with six point multilevel internal calibration provides a linear response for each enantiomer in the 10-200 ng/mL concentration range, is simple, inexpensive, and reproducible, and has an LOQ of 5 ng/mL. It was applied to oral fluid patient samples that were collected up to 12 h after intake of an immediate release tablet and two different extended release formulations with racemic methylphenidate. Drug profiles could thereby be assessed in a stereoselective way. Almost no levorotary threo-methylphenidate enantiomer was detected after intake of the two extended release formulations, whereas this enantiomer was detected during the first 2.5 h after intake of the immediate release preparation. The noninvasive collection of oral fluid is an attractive alternative to plasma for the monitoring of methylphenidate exposure in the pediatric community.

Influence of high-conductivity buffer composition on field-enhanced sample injection coupled to sweeping in CE

The aim of this work was to clarify the mechanism taking place in field-enhanced sample injection coupled to sweeping and micellar EKC (FESI-Sweep-MEKC), with the utilization of two acidic high-conductivity buffers (HCBs), phosphoric acid or sodium phosphate buffer, in view of maximizing sensitivity enhancements. Using cationic model compounds in acidic media, a chemometric approach and simulations with SIMUL5 were implemented. Experimental design first enabled to identify the significant factors and their potential interactions. Simulation demonstrates the formation of moving boundaries during sample injection, which originate at the initial sample/HCB and HCB/buffer discontinuities and gradually change the compositions of HCB and BGE. With sodium phosphate buffer, the HCB conductivity increased during the injection, leading to a more efficient preconcentration by staking (about 1.6 times) than with phosphoric acid alone, for which conductivity decreased during injection. For the same injection time at constant voltage, however, a lower amount of analytes was injected with sodium phosphate buffer than with phosphoric acid. Consequently sensitivity enhancements were lower for the whole FESI-Sweep-MEKC process. This is why, in order to maximize sensitivity enhancements, it is proposed to work with sodium phosphate buffer as HCB and to use constant current during sample injection.

Pleasant Events, Activity Restriction, and Blood Pressure in Dementia Caregivers

Objective: A combination of high engagement in pleasurable activities and low perceived activity restriction is potentially protective for a number of health and quality of life outcomes. This study tests the newly proposed Pleasant Events and Activity Restriction (PEAR) model to explain level of blood pressure (BP) in a sample of elderly dementia caregivers. Methods: This cross-sectional study included 66 caregivers, ≥55 years of age, providing in-home care to a relative with dementia. Planned comparisons were made to assess group differences in BP between caregivers reporting high engagement in pleasant events plus low perceived activity restriction (HPLR; n = 22) to those with low pleasure plus high restriction (LPHR; n = 23) or those with either high pleasure plus high restriction or low pleasure plus low restriction (HPHR/LPLR; n = 21). Results: After adjustments for age, sex, body mass index, use of antihypertensive medication, physical activity, and number of health problems, HPLR participants (86.78 mm|Hg) had significantly lower mean arterial pressure compared with LPHR participants (94.70 mm|Hg) (p = .01, Cohen's d = 0.89) and HPHR/LPLR participants (94.84 mm|Hg) (p = .023, d = 0.91). Similar results were found in post hoc comparisons of both systolic and diastolic BP. Conclusions: This study extends support for the PEAR model to physical health outcomes. Differences in BP between the HPLR group and other groups were of large magnitude and thus clinically meaningful. The findings may inform intervention studies aimed at investigating whether increasing pleasant events and lowering perceived activity restriction may lower BP. (PsycINFO Database Record (c) 2012 APA, all rights reserved).

Limitations of the use of pressure waves to verify correct epidural needle position in dogs

The use of pressure waves to confirm the correct position of the epidural needle has been described in several domestic species and proposed as a valid alternative to standard methods, namely, control radiographic exam and fluoroscopy. The object of this retrospective clinical study was to evaluate the sensitivity of the epidural pressure waves as a test to verify the correct needle placement in the epidural space in dogs, in order to determine whether this technique could be useful not only in the clinical setting but also when certain knowledge of needle's tip position is required, for instance when performing clinical research focusing on epidural anaesthesia. Of the 54 client-owned dogs undergoing elective surgeries and enrolled in this retrospective study, only 45% showed epidural pressure waves before and after epidural injection. Twenty-six percent of the animals showed epidural pressure waves only after the injection, whereas 29% of the dogs showed epidural pressure waves neither before nor after injection and were defined as false negatives. Our results show that the epidural pressure wave technique to verify epidural needle position lacks sensitivity, resulting in many false negatives. As a consequence, the applicability of this technique is limited to situations in which precise, exact knowledge of the needle's tip position is not mandatory.

An MEKC assay for the therapeutic drug monitoring of cefepime

The development of a robust assay based on MEKC for cefepime in human serum and plasma with internal quality assurance is reported. Sample preparation comprises protein precipitation in the presence of SDS at pH 4.5. This is a gentle approach for which decomposition of cefepime during sample handling is negligible. After hydrodynamic sample injection of the supernatant, analysis occurs in a phosphate/borate buffer at pH 9.1 with 75 mM SDS using normal polarity and analyte detection at 257 nm. The MEKC run time interval and throughput are about 5 min and seven samples per hour, respectively. The calibration range for cefepime is 1-60 μg/mL, with 1 μg/mL being the LOQ. The performance of the assay with multilevel internal calibration was assessed with calibration and control samples. The assay is shown to be simple, inexpensive, reproducible, and robust. It was applied to determine cefepime levels in the sera of critically ill patients and to assess the instability of cefepime in patient and control samples. Our data revealed that serum containing cefepime can be stored at -20°C for a short time, whereas for long-term storage, samples have to be kept at -70°C.

Development of a computer-assisted high-pressure Injection device for vertebroplasty

A novel computer-assisted injection device for the delivery of highly viscous bone cements in vertebroplasty is presented. It addresses the shortcomings of manual injection systems ranging from low-pressure and poor level of control to device failure. The presented instrument is capable of generating a maximum pressure of 5000 kPa in traditional 6-ml syringes and provides an advanced control interface for precise cement delivery from outside radiation fields emitted by intraoperative imaging systems. The integrated real-time monitoring of injection parameters, such as flow-rate, volume, pressure, and viscosity, simplifies consistent documentation of interventions and establishes a basis for the identification of safe injection protocols on the longer term. Control algorithms prevent device failure due to overloading and provide means to immediately stop cement flow to avoid leakage into adjacent tissues.

Water isotopic ratios from a continuously melted ice core sample

A new technique for on-line high resolution isotopic analysis of liquid water, tailored for ice core studies is presented. We built an interface between a Wavelength Scanned Cavity Ring Down Spectrometer (WS-CRDS) purchased from Picarro Inc. and a Continuous Flow Analysis (CFA) system. The system offers the possibility to perform simultaneuous water isotopic analysis of δ18O and δD on a continuous stream of liquid water as generated from a continuously melted ice rod. Injection of sub μl amounts of liquid water is achieved by pumping sample through a fused silica capillary and instantaneously vaporizing it with 100% efficiency in a~home made oven at a temperature of 170 °C. A calibration procedure allows for proper reporting of the data on the VSMOW–SLAP scale. We apply the necessary corrections based on the assessed performance of the system regarding instrumental drifts and dependance on the water concentration in the optical cavity. The melt rates are monitored in order to assign a depth scale to the measured isotopic profiles. Application of spectral methods yields the combined uncertainty of the system at below 0.1‰ and 0.5‰ for δ18O and δD, respectively. This performance is comparable to that achieved with mass spectrometry. Dispersion of the sample in the transfer lines limits the temporal resolution of the technique. In this work we investigate and assess these dispersion effects. By using an optimal filtering method we show how the measured profiles can be corrected for the smoothing effects resulting from the sample dispersion. Considering the significant advantages the technique offers, i.e. simultaneuous measurement of δ18O and δD, potentially in combination with chemical components that are traditionally measured on CFA systems, notable reduction on analysis time and power consumption, we consider it as an alternative to traditional isotope ratio mass spectrometry with the possibility to be deployed for field ice core studies. We present data acquired in the field during the 2010 season as part of the NEEM deep ice core drilling project in North Greenland.

Tunnelled versus straight intravitreal injection: intraocular pressure changes, vitreous reflux, and patient discomfort

PURPOSE: To compare tunnelled scleral intravitreal injection with straight scleral intravitreal injection concerning short-term intraocular pressure (IOP) changes, occurrence and amount of vitreous reflux, and patient discomfort. METHODS: Sixty patients were randomly allocated to two groups (tunnelled intravitreal injection and straight intravitreal injection). IOP was measured before and directly (<1 minute) after the injection of 0.05 mL of an antivascular endothelial growth factor agent and then every 5 minutes until IOP was <30 mmHg. Occurrence and amount of vitreous reflux were recorded. Patient discomfort during injection was assessed with a Wong-Baker faces pain rating scale. RESULTS: IOP (mmHg +/- SD) increased significantly directly after injection to 35.97 +/- 8.13 (tunnelled intravitreal injection) and 30.19 +/- 12.14 (straight intravitreal injection). These pressure spikes differed significantly between both groups (P = 0.01, mean difference: -7.11). Five minutes after injection, there was no significant difference in IOP increase between the groups. All IOP measurements were <30 mmHg after 15 minutes. Occurrence and amount of vitreous reflux were significantly higher with straight intravitreal injection. There was no significant difference in Wong-Baker faces pain rating scale score between both groups. CONCLUSION: Tunnelled intravitreal injection seems to be the technique of choice for low-volume intravitreal injection (0.05 mL). There is neither a difference in patient discomfort nor a difference in IOP increase 5 minutes after injection between both groups. Significantly less vitreous reflux with tunnelled intravitreal injection should lead to less postinjectional drug loss.

Genotyping of Francisella tularensis strains by pulsed-field gel electrophoresis, amplified fragment length polymorphism fingerprinting, and 16S rRNA gene sequencing

We evaluated three molecular methods for identification of Francisella strains: pulsed-field gel electrophoresis (PFGE), amplified fragment length polymorphism (AFLP) analysis, and 16S rRNA gene sequencing. The analysis was performed with 54 Francisella tularensis subsp. holarctica, 5 F. tularensis subsp. tularensis, 2 F. tularensis subsp. novicida, and 1 F. philomiragia strains. On the basis of the combination of results obtained by PFGE with the restriction enzymes XhoI and BamHI, PFGE revealed seven pulsotypes, which allowed us to discriminate the strains to the subspecies level and which even allowed us to discriminate among some isolates of F. tularensis subsp. holarctica. The AFLP analysis technique produced some degree of discrimination among F. tularensis subsp. holarctica strains (one primary cluster with three major subclusters and minor variations within subclusters) when EcoRI-C and MseI-A, EcoRI-T and MseI-T, EcoRI-A and MseI-C, and EcoRI-0 and MseI-CA were used as primers. The degree of similarity among the strains was about 94%. The percent similarities of the AFLP profiles of this subspecies compared to those of F. tularensis subsp. tularensis, F. tularensis subsp. novicida, and F. philomiragia were less than 90%, about 72%, and less than 24%, respectively, thus permitting easy differentiation of this subspecies. 16S rRNA gene sequencing revealed 100% similarity for all F. tularensis subsp. holarctica isolates compared in this study. These results suggest that although limited genetic heterogeneity among F. tularensis subsp. holarctica isolates was observed, PFGE and AFLP analysis appear to be promising tools for the diagnosis of infections caused by different subspecies of F. tularensis and suitable techniques for the differentiation of individual strains.

Anisotropic diffusion at the field scale in a 4-year multi-tracer diffusion and retention experiment – I: Insights from the experimental data

Abstract Claystones are considered worldwide as barrier materials for nuclear waste repositories. In the Mont Terri underground research laboratory (URL), a nearly 4-year diffusion and retention (DR) experiment has been performed in Opalinus Clay. It aimed at (1) obtaining data at larger space and time scales than in laboratory experiments and (2) under relevant in situ conditions with respect to pore water chemistry and mechanical stress, (3) quantifying the anisotropy of in situ diffusion, and (4) exploring possible effects of a borehole-disturbed zone. The experiment included two tracer injection intervals in a borehole perpendicular to bedding, through which traced artificial pore water (APW) was circulated, and a pressure monitoring interval. The APW was spiked with neutral tracers (HTO, HDO, H2O-18), anions (Br, I, SeO4), and cations (Na-22, Ba-133, Sr-85, Cs-137, Co-60, Eu-152, stable Cs, and stable Eu). Most tracers were added at the beginning, some were added at a later stage. The hydraulic pressure in the injection intervals was adjusted according to the measured value in the pressure monitoring interval to ensure transport by diffusion only. Concentration time-series in the APW within the borehole intervals were obtained, as well as 2D concentration distributions in the rock at the end of the experiment after overcoring and subsampling which resulted in �250 samples and �1300 analyses. As expected, HTO diffused the furthest into the rock, followed by the anions (Br, I, SeO4) and by the cationic sorbing tracers (Na-22, Ba-133, Cs, Cs-137, Co-60, Eu-152). The diffusion of SeO4 was slower than that of Br or I, approximately proportional to the ratio of their diffusion coefficients in water. Ba-133 diffused only into �0.1 m during the �4 a. Stable Cs, added at a higher concentration than Cs-137, diffused further into the rock than Cs-137, consistent with a non-linear sorption behavior. The rock properties (e.g., water contents) were rather homogeneous at the centimeter scale, with no evidence of a borehole-disturbed zone. In situ anisotropy ratios for diffusion, derived for the first time directly from field data, are larger for HTO and Na-22 (�5) than for anions (�3�4 for Br and I). The lower ionic strength of the pore water at this location (�0.22 M) as compared to locations of earlier experiments in the Mont Terri URL (�0.39 M) had no notable effect on the anion accessible pore fraction for Cl, Br, and I: the value of 0.55 is within the range of earlier data. Detailed transport simulations involving different codes will be presented in a companion paper.

[Collagenase injection in Dupuytren's disease, evaluation of the ultrasound assisted technique].

Since October 2011, the enzymatic lysis of Dupuytren's cord was introduced in Switzerland (Xiapex(®), Auxilium Pharmaceuticals, Pfizer). Here we present our first university experience and underline the major role of ultrasound during the injection. Between December 2011 and February 2013, 52 injections were performed to eliminate 43 Dupuytren's cords in 33 patients. The mean age of the patients was 64.4 ± 8.5 years. Complications were documented for each patient. Before, directly after and after a minimum of 6 months post-injection, the contracture of the treated joint was measured with use of a goniometer. The DASH score was evaluated after a minimum of 6 months and the patients were asked to subjectively evaluate the outcome of the treatment (very good, good, mild, poor) and whether they would reiterate it if necessary. Four skin defects, one lymphangitis, and one CRPS were responsible for a complication rate of 18%. There was no infection and no tendon rupture in the series. The mean MCP joint contracture was respectively 36.8 ± 27.4°, 3.5 ± 7.8° (gain of mobility compared to the preoperative situation 33.3°, P<0.001), and 8.4 ± 13.9° (gain 28.4°, P<0.001) respectively before, just after and at the long-term clinical control. The mean PIP joint contracture was respectively 36.5 ± 29.1°, 5.9 ± 6.7° (gain 30.6°, P<0.001), and 15.1 ± 13.8° (gain 21.4°, P<0.001) respectively before injection, just after and at the long-term clinical control. The DASH score decreased from 24 ± 14 to 7 ± 9 (P<0.001). Eighty-one per cent of the patients were satisfied or very satisfied of the treatment. All but two would reiterate the treatment if necessary. Ultrasound is able to target the injection of collagenase in order to reduce complications. The short-term results of this non-invasive therapy are very promising however comparison with conventional procedures is difficult as the long-term results are lacking.

Time-lapse pressure tomography for characterizing CO2 plume evolution in a deep saline aquifer

A time-lapse pressure tomography inversion approach is applied to characterize the CO2 plume development in a virtual deep saline aquifer. Deep CO2 injection leads to flow properties of the mixed-phase, which vary depending on the CO2 saturation. Analogous to the crossed ray paths of a seismic tomographic experiment, pressure tomography creates streamline patterns by injecting brine prior to CO2 injection or by injecting small amounts of CO2 into the two-phase (brine and CO2) system at different depths. In a first step, the introduced pressure responses at observation locations are utilized for a computationally rapid and efficient eikonal equation based inversion to reconstruct the heterogeneity of the subsurface with diffusivity (D) tomograms. Information about the plume shape can be derived by comparing D-tomograms of the aquifer at different times. In a second step, the aquifer is subdivided into two zones of constant values of hydraulic conductivity (K) and specific storage (Ss) through a clustering approach. For the CO2 plume, mixed-phase K and Ss values are estimated by minimizing the difference between calculated and “true” pressure responses using a single-phase flow simulator to reduce the computing complexity. Finally, the estimated flow property is converted to gas saturation by a single-phase proxy, which represents an integrated value of the plume. This novel approach is tested first with a doublet well configuration, and it reveals a great potential of pressure tomography based concepts for characterizing and monitoring deep aquifers, as well as the evolution of a CO2 plume. Still, field-testing will be required for better assessing the applicability of this approach.

Numerical study of the laser-tip coupling in surface plasmon assisted stacked-double-gate field emitter arrays

Recently, sub-wavelength-pitch stacked double-gate metal nanotip arrays have been proposed to realize high current, high brightness electron bunches for ultrabright cathodes for x-ray free-electron laser applications. With the proposed device structure, ultrafast field emission of photoexcited electrons is efficiently driven by vertical incident near infrared laser pulses, via near field coupling of the surface plasmon polariton resonance of the gate electrodes with the nanotip apex. In this work, in order to gain insight in the underlying physical processes, the authors report detailed numerical studies of the proposed device. The results indicate the importance of the interaction of the double-layer surface plasmon polariton, the position of the nanotip, as well as the incident angle of the near infrared laser pulses.