Disposable solid-contact ion-selective electrodes for environmental monitoring of lead with ppb

Solid-contact Pb2+-selective-electrodes and solid contact reference electrodes suitable for use as disposable sensing devices for environmental monitoring of lead have been prepared on screen-printed substrates. Accurate control over the fabrication procedures leads to excellent reproducibility of their calibration characteristics such as slope, offset and limit of detection. In particular, the limit of detection in the nanomolar range opens the possibility of their use for trace analysis of Pb2+ in environmental water samples. Significantly, the potentiometric measurements correlate well with data determined using inductively coupled plasma mass spectrometry (ICP-MS) in a number of real samples taken from local rivers. Ways in which these sensors might be employed in autonomous platforms for monitoring water quality in-situ are discussed. The possibility of including arrays of virtually identical sensors is highlighted as a possible route to achieve long-term deployments

Near infrared reflectance spectroscopy for the determination of free gossypol in cottonseed meal

Gossypol is a toxic polyphenolic compound produced by the pigment glands of the cotton plant. The free gossypol content of cottonseed meal (CSM) is commonly determined by the American Oil Chemists’ Society (AOCS) wet chemistry method. The AOCS method, however, laboratory-intensive, time-consuming, and therefore, not practical for quick field analyses. To determine if the free gossypol content of CSM could be predicted by near infrared reflectance spectroscopy (NIRS), CSM samples were collected from all over the world. All CSM samples were ground and a portion of each analyzed for free gossypol by the AOCS procedure (reference data) and by NIRS (reflectance data). Both reflectance and reference data were combined in calibration. The coefficient of determination (r2) and standard error of prediction (SEP) were used to assess the calibration accuracy. The r2 was 0.728, and the SEP was 0.034 for the initial calibration that included samples from all over the world. However, the r2 and SEP improved to 0.921 and 0.014, respectively, if the calibration was made using CSM samples only from the United States. These results indicate that a general prediction equation can be developed to predict the free gossypol content of CSM by NIRS. From a practical standpoint, NIRS technology provides a method for quickly assessing whether a particular batch of CSM has a free gossypol content low enough to be suitable for use in poultry diets.This research was supported in part by grant 05-635GA from the Georgian Cotton Commission, Perry, G

Stability of Liquid Bridges between Equal Disks in an Axial Gravity Field

The stability of axisymmetric liquid bridges spanning two equal-diameter solid disks subjected to an axial gravity field of arbitrary intensity is analyzed for all possible liquid volumes. The boundary of the stability region for axisymmetric shapes (considering both axisymmetric and nonaxisymmetric perturbations) have been calculated. It is found that, for sufficiently small Bond numbers, three different unstable modes can appear. If the volume of liquid is decreased from that of an initially stable axisymmetric configuration the bridge either develops an axisymmetric instability (breaking in two drops as already known) or detaches its interface from the disk edges (if the length is smaller than a critical value depending on contact angle), whereas if the volume is increased the unstable mode consists of a nonaxisymmetric deformation. This kind of nonaxisymmetric deformation can also appear by decreasing the volume if the Bond number is large enough. A comparison with other previous partial theoretical analyses is presented, as well as with available experimental results

Energetics of donor-doping, metal vacancies, and oxygen-loss in A-site Rare-Earth-doped BaTiO3

The energetics of La-doping in BaTiO3 are reported for both (electronic) donor-doping with the creation of Ti3+ cations and ionic doping with the creation of Ti vacancies. The experiments (for samples prepared in air) and simulations demonstrate that ionic doping is the preferred mechanism for all concentrations of La-doping. The apparent disagreement with electrical conduction of these ionic doped samples is explained by subsequent oxygen-loss, which leads to the creation of Ti3+ cations. Simulations show that oxygen-loss is much more favorable in the ionic-doped system than undoped BaTiO3 due to the unique local structure created around the defect site. These findings resolve the so-called “donor-doping” anomaly in BaTiO3 and explain the source of semiconductivity in positive temperature coefficient of resistance (PTCR) BaTiO3 thermistors.PostprintPeer reviewe

Magnetic resonance mammography in the evaluation of recurrence at the prior lumpectomy site after conservative surgery and radiotherapy

INTRODUCTION: The aim was to assess the value of magnetic resonance mammography (MRM) in the detection of recurrent breast cancer on the prior lumpectomy site in patients with previous conservative surgery and radiotherapy. METHODS: Between April 1999 and July 2003, 93 consecutive patients with breast cancer treated with conservative surgery and radiotherapy underwent MRM, when a malignant lesion on the site of lumpectomy was suspected by ultrasound and/or mammography. MRM scans were evaluated by morphological and dynamic characteristics. MRM diagnosis was compared with histology or with a 36-month imaging follow-up. Enhancing areas independent of the prior lumpectomy site, incidentally detected during the MRM, were also evaluated. RESULTS: MRM findings were compared with histology in 29 patients and with a 36-month follow-up in 64 patients. MRM showed 90% sensitivity, 91.6% specificity, 56.3% positive predictive value and 98.7% negative predictive value for detection of recurrence on the surgical scar. MRM detected 13 lesions remote from the scar. The overall sensitivity, specificity, positive predictive value and negative predictive value of MRM for detection of breast malignancy were 93.8%, 90%, 62.5% and 98.8%, respectively. CONCLUSION: MRM is a sensitive method to differentiate recurrence from post-treatment changes at the prior lumpectomy site after conservative surgery and radiation therapy. The high negative predictive value of this technique can avoid unnecessary biopsies or surgical treatments

Comparison of the success rate of inguinal approach with classical pubic approach for obturator nerve block in patients undergoing TURB

BACKGROUND: During transurethral resection of bladder tumors (TURB) under spinal anesthesia, electrical resection of the lateral wall mass may cause violent adductor contraction and possible inadvertent bladder perforation. Therefore, obturator nerve block (ONB) is mandatory after spinal anesthesia to avoid adductor muscle contraction. We compared the success rate and efficacy of an inguinal approach, to a pubic approach for ONB. METHODS: One hundred and two patients who required ONB undergoing TURB with spinal anesthesia were included in this study. After spinal anesthesia, ONB was performed with an inguinal approach (Group I, n = 51) or pubic approach (Group P, n = 51) using a nerve stimulator. In the pubic approach, a needle was inserted at a point 1.5 cm lateral and 1.5 cm inferior to the pubic tubercle. For the inguinal approach, a needle was inserted at the midpoint of the femoral artery and the inner margin of the adductor longus muscle 0.5 cm below the inguinal crease. If the adductor contracture had not occurred by the 3rd attempt, it was defined as a failed block. Puncture frequency, success rate, anatomical characteristics, and the presence of adductor muscle contraction during operation were evaluated. RESULTS: The success rate of ONB was higher in group I compared to group P (96.1% vs. 84.0%, P = 0.046) and the frequency of needle attempts was lower in group I than in group P (1.8 ± 0.9 vs. 1.3 ± 0.6, P = 0.01). CONCLUSIONS: The inguinal approach for ONB appears to be technically easier and offers certain anatomical advantages when compared to the pubic approach.ope

Theoretical Study on the Piezoelectric Performance of Lead-Free 1–3-Type Composites

The paper is devoted to the analysis of high-performance piezo-composites based on lead-free ferroelectric single crystals. The composite consists of parallelepiped-shaped single-crystal rods which are surrounded by a laminar polymer matrix, and the composite as a whole is described by 1–2–2 connectivity. Such a composite structure promotes high piezoelectric sensitivity and hydrostatic response. Of particular interest are piezoelectric coefficients g*33 and h*33, squared figure of merit d*33 g*33, electromechanical coupling factor k*t at the thickness-mode oscillation, and hydrostatic parameters g*h and d*h g*h. The influence of the laminar matrix on the aforementioned parameters is studied in a wide volume-fraction range. Examples of maxima and large anisotropy of some effective parameters are discussed for the 1–2–2 composites based on [Lix(K1−yNay)1−x](Nb1−zTaz)O3:Mn single crystals. The role of elastic properties of the laminar matrix in achieving large hydrostatic parameters and piezoelectric anisotropy of these composites is emphasised. Their effective parameters are compared to those of composites based on the lead-containing relaxor-ferroelectric single crystals and to specific parameters of poled textured ceramics. Advantages of the studied composites over the relaxor-ferroelectric-based composites and textured ceramics open up new possibilities to apply the 1–3-type lead-free composites as active elements of piezoelectric sensors, hydrophones, energy-harvesting, and transducer devices.</p

Domain switching energies: Mechanical versus electrical loading in La-doped bismuth ferrite-lead titanate

The mechanical stress-induced domain switching and energy dissipation in morphotropic phase boundary (1 - x)(Bi(1-y)La(y))FeO(3)-xPbTiO(3) during uniaxial compressive loading have been investigated at three different temperatures. The strain obtained was found to decrease with increasing lanthanum content, although a sharp increase in strain was observed for compositions doped with 7.5 and 10 at. % La. Increased domain switching was found in compositions with decreased tetragonality. This is discussed in terms of the competing influences of the amount of domain switching and the spontaneous strain on the macroscopic behavior under external fields. Comparison of the mechanically and electrically dissipated energy showed significant differences, discussed in terms of the different microscopic interactions of electric field and stress.open10