Compact and autonomous multiwavelength microanalyzer for in-line and in situ colorimetric determinations

Nowadays, the attainment of microsystems that integrate most of the stages involved in an analytical process has raised an enormous interest in several research fields. This approach provides experimental set-ups of increased robustness and reliability, which simplify their application to in-line and continuous biomedical and environmental monitoring. In this work, a novel, compact and autonomous microanalyzer aimed at multiwavelength colorimetric determinations is presented. It integrates the microfluidics (a three-dimensional mixer and a 25 mm length "Z-shape" optical flow-cell), a highly versatile multiwavelength optical detection system and the associated electronics for signal processing and drive, all in the same device. The flexibility provided by its design allows the microanalyzer to be operated either in single fixed mode to provide a dedicated photometer or in multiple wavelength mode to obtain discrete pseudospectra. To increase its reliability, automate its operation and allow it to work under unattended conditions, a multicommutation sub-system was developed and integrated with the experimental set-up. The device was initially evaluated in the absence of chemical reactions using four acidochromic dyes and later applied to determine some key environmental parameters such as phenol index, chromium(VI) and nitrite ions. Results were comparable with those obtained with commercial instrumentation and allowed to demonstrate the versatility of the proposed microanalyzer as an autonomous and portable device able to be applied to other analytical methodologies based on colorimetric determinations.

A Low Power CMOS Voltage Regulator for a Wireless Blood Pressure Biosensor

This paper describes a CMOS implementation of a linear voltage regulator (LVR) used to power up implanted physiological signal systems, as it is the case of a wireless blood pressure biosensor. The topology is based on a classical structure of a linear low-dropout regulator. The circuit is powered up from an RF link, thus characterizing a passive radio frequency identification (RFID) tag. The LVR was designed to meet important features such as low power consumption and small silicon area, without the need for any external discrete components. The low power operation represents an essential condition to avoid a high-energy RF link, thus minimizing the transmitted power and therefore minimizing the thermal effects on the patient's tissues. The project was implemented in a 0.35-mu m CMOS process, and the prototypes were tested to validate the overall performance. The LVR output is regulated at 1 V and supplies a maximum load current of 0.5 mA at 37 degrees C. The load regulation is 13 mV/mA, and the line regulation is 39 mV/V. The LVR total power consumption is 1.2 mW.

A New Method of Current Switching for Linear Wide-Range Measurement Systems

This new and general method here called overflow current switching allows a fast, continuous, and smooth transition between scales in wide-range current measurement systems, like electrometers. This is achieved, using a hydraulic analogy, by diverting only the overflow current, such that no slow element is forced to change its state during the switching. As a result, this approach practically eliminates the long dead time in low-current (picoamperes) switching. Similar to a logarithmic scale, a composition of n adjacent linear scales, like a segmented ruler, measures the current. The use of a linear wide-range system based on this technique assures fast and continuous measurement in the entire range, without blind regions during transitions and still holding suitable accuracy for many applications. A full mathematical development of the method is given. Several computer realistic simulations demonstrated the viability of the technique.

Effect of passive ultrassonic instrumentation as a final irrigation protocol on debris and smear layer removal

This study sought to evaluate the efficacy of passive ultrasonic irrigation (PUI) on removing the smear layer and debris from root dentin using scanning electron microscopy (SEM). Twenty-five bovine incisors were manually prepared and divided into three groups according to the final irrigation protocol: EDTA, final irrigation with 12 mL of 17% EDTA for 3 minutes followed by 5 mL of 2.5% NaOCl; EDTA=PUI, final flush with 4 mL of 17% EDTA and PUI for 30 seconds. These procedures were repeated three times to standardize the volume of the irrigant. Control group, after preparation, the specimens were irrigated only with 17 mL of 2.5% NaOCl. The roots were fractured and analyzed using SEM. The intragroup analysis revealed that the EDTA=PUI protocol removed a higher amount of debris at the cervical third (P 5 0.03). The intergroup analysis revealed that EDTA=PUI presented the lowest amount of debris at the cervical third (P 5 0.007). Smear layer scores were higher in the control group compared with the EDTA and EDTA=PUI groups, but only at the cervical third (P 50.02). None of the final irrigant protocols completely removed the smear layer and debris. EDTA=PUI only improved the removal of debris at the cervical third.

Influence of apical foramen lateral opening and file size on cemental canal instrumentation

Since instrumentation of the apical foramen has been suggested for cleaning and disinfection of the cemental canal, selection of the file size and position of the apical foramen have challenging steps. This study analyzed the influence of apical foramen lateral opening and file size can exert on cemental canal instrumentation. Thirty-four human maxillary central incisors were divided in two groups: Group 1 (n=17), without flaring, and Group 2 (n=17), with flaring with LA Axxess burs. K-files of increasing diameters were progressively inserted into the canal until binding at the apical foramen was achieved and tips were visible and bonded with ethyl cyanoacrylate adhesive. Roots/files set were cross-sectioned 5 mm from the apex. Apices were examined by scanning electron microscopy at ×140 and digital images were captured. Data were analyzed statistically by Student’s t test and Fisher’s exact test at 5% significance level. SEM micrographs showed that 19 (56%) apical foramina emerged laterally to the root apex, whereas 15 (44%) coincided with it. Significantly more difficulty to reach the apical foramen was noted in Group 2. Results suggest that the larger the foraminal file size, the more difficult the apical foramen instrumentation may be in laterally emerged cemental canals.

Influence of effective number of pulses on the morphological structure of teeth and bovine femur after femtosecond laser ablation

Femtosecond lasers have been widely used in laser surgery as an instrument for contact-free tissue removal of hard dental, restorative materials, and osseous tissues, complementing conventional drilling or cutting tools. In order to obtain a laser system that provides an ablation efficiency comparable to mechanical instruments, the laser pulse rate must be maximal without causing thermal damage. The aim of this study was to compare the different morphological characteristics of the hard tissue after exposure to lasers operating in the femtosecond pulse regime. Two different kinds of samples were irradiated: dentin from human extracted teeth and bovine femur samples. Different procedures were applied, while paying special care to preserving the structures. The incubation factor S was calculated to be 0.788 +/- 0.004 for the bovine femur bone. These results indicate that the incubation effect is still substantial during the femtosecond laser ablation of hard tissues. The plasma-induced ablation has reduced side effects, i.e., we observe less thermal and mechanical damage when using a superficial femtosecond laser irradiation close to the threshold conditions. In the femtosecond regime, the morphology characteristics of the cavity were strongly influenced by the change of the effective number of pulses. (C) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.JBO.17.4.048001]

Quantification of terbinafine in pharmaceutical tablets using capillary electrophoresis with contactless conductivity detection and batch injection analysis with amperometric detection

Terbinafine hydrochloride (TerbHCl) is an allylamine derivative with fungicidal action, especially against dermatophytes. Different analytical methods have been reported for quantifying TerbHCl in different samples. These procedures require time-consuming sample preparation or expensive instrumentation. In this paper, electrochemical methods involving capillary electrophoresis with contactless conductivity detection, and amperometry associated with batch injection analysis, are described for the determination of TerbHCl in pharmaceutical products. In the capillary electrophoresis experiments, terbinafine was protonated and analyzed in the cationic form in less than 1 min. A linear range from 1.46 to 36.4 mu g mL(-1) in acetate buffer solution and a detection limit of 0.11 mu g mL(-1) were achieved. In the amperometric studies, terbinafine was oxidized at +0.85 V with high throughput (225 injection h(-1)) and good linear range (10-100 mu mol L-1). It was also possible to determine the antifungal agent using simultaneous conductometric and potentiometric titrations in the presence of 5% ethanol. The electrochemical methods were applied to the quantification of TerbHCl in different tablet samples; the results were comparable with values indicated by the manufacturer and those found using titrimetry according to the Pharmacopoeia. The electrochemical methods are simple, rapid and an appropriate alternative for quantifying this drug in real samples. (C) 2012 Elsevier B.V. All rights reserved.

Effect of pre-flaring and file size on the accuracy of two electronic apex locators

Objective: This ex vivo study evaluated the effect of pre-flaring and file size on the accuracy of the Root ZX and Novapex electronic apex locators (EALs). Material and methods: The actual working length (WL) was set 1 mm short of the apical foramen in the palatal root canals of 24 extracted maxillary molars. The teeth were embedded in an alginate mold, and two examiners performed the electronic measurements using #10, #15, and #20 K-files. The files were inserted into the root canals until the "0.0" or "APEX" signals were observed on the LED or display screens for the Novapex and Root ZX, respectively, retracting to the 1.0 mark. The measurements were repeated after the pre-flaring using the S1 and SX Pro-Taper instruments. Two measurements were performed for each condition and the means were used. Intra-class correlation coefficients (ICCs) were calculated to verify the intra-and inter-examiner agreement. The mean differences between the WL and electronic length values were analyzed by the three-way ANOVA test (p<0.05). Results: ICCs were high (>0.8) and the results demonstrated a similar accuracy for both EALs (p>0.05). Statistically significant accurate measurements were verified in the pre-flared canals, except for the Novapex using a #20 K-file. Conclusions: The tested EALs showed acceptable accuracy, whereas the pre-flaring procedure revealed a more significant effect than the used file size.

Optical transition radiation used in the diagnostic of low energy and low current electron beams in particle accelerators

Optical transition radiation (OTR) plays an important role in beam diagnostics for high energy particle accelerators. Its linear intensity with beam current is a great advantage as compared to fluorescent screens, which are subject to saturation. Moreover, the measurement of the angular distribution of the emitted radiation enables the determination of many beam parameters in a single observation point. However, few works deals with the application of OTR to monitor low energy beams. In this work we describe the design of an OTR based beam monitor used to measure the transverse beam charge distribution of the 1.9-MeV electron beam of the linac injector of the IFUSP microtron using a standard vision machine camera. The average beam current in pulsed operation mode is of the order of tens of nano-Amps. Low energy and low beam current make OTR observation difficult. To improve sensitivity, the beam incidence angle on the target was chosen to maximize the photon flux in the camera field-of-view. Measurements that assess OTR observation (linearity with beam current, polarization, and spectrum shape) are presented, as well as a typical 1.9-MeV electron beam charge distribution obtained from OTR. Some aspects of emittance measurement using this device are also discussed. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4748519]

Quantitative assessment of the intensity of palmar and plantar sweating in patients with primary palmoplantar hyperhidrosis

Objective: To compare individuals with and without hyperhidrosis in terms of the intensity of palmar and plantar sweating. Methods: We selected 50 patients clinically diagnosed with palmoplantar hyperhidrosis and 25 normal individuals as controls. We quantified sweating using a portable noninvasive electronic device that has relative humidity and temperature sensors to measure transepidermal water loss. All of the individuals had a body mass index of 20-25 kg/cm(2). Subjects remained at rest for 20-30 min before the measurements in order to reduce external interference. The measurements were carried out in a climate-controlled environment (21-24 degrees C). Measurements were carried out on the hypothenar region on both hands and on the medial plantar region on both feet. Results: In the palmoplantar hyperhidrosis group, the mean transepidermal water loss on the hands and feet was 133.6 +/- 51.0 g/m(2)/h and 71.8 +/- 40.3 g/m(2)/h, respectively, compared with 37.9 +/- 18.4 g/m(2)/h and 27.6 +/- 14.3 g/m(2)/h, respectively, in the control group. The differences between the groups were statistically significant (p < 0.001 for hands and feet). Conclusions: This method proved to be an accurate and reliable tool to quantify palmar and plantar sweating when performed by a trained and qualified professional.

Comparative study of the proton beam effects between the conventional and Circular-Gate MOSFETs

The study of ionizing radiation effects on semiconductor devices is of great relevance for the global technological development and is a necessity in some strategic areas in Brazil. This work presents preliminary results of radiation effects in MOSFETs that were exposed to 3.2 Grad radiation dose produced by a 2.6-MeV proton beam. The focus of this work was to electrically characterize a Rectangular-Gate MOSFET (RGT) and a Circular-Gate MOSFET (CGT), manufactured with the On Semiconductor 0.5 mu m standard CMOS fabrication process and to verify a suitable geometry for space applications. During the experiment, I-DS x V-GS curves were measured. After irradiation, the RGT off-state current (I-OFF) increased approximately two orders of magnitude reaching practically the same value of the I-OFF in the CGT, which only doubled its value. (C) 2011 Elsevier B.V. All rights reserved.

Performance of electronic devices submitted to X-rays and high energy proton beams

In this work we have studied the radiation effects on MOSFET electronic devices. The integrated circuits were exposed to 10 key X-ray radiation and 2.6 MeV energy proton beam. We have irradiated MOSFET devices with two different geometries: rectangular-gate transistor and circular-gate transistor. We have observed the cumulative dose provokes shifts on the threshold voltage and increases or decreases the transistor's off-state and leakage current. The position of the trapped charges in modern CMOS technology devices depends on radiation type, dose rate, total dose, applied bias and is a function of device geometry. We concluded the circular-gate transistor is more tolerant to radiation than the rectangular-gate transistor. (C) 2011 Elsevier B.V. All rights reserved.

Laboratory and in situ studies on a compacted clayey silt fill

This paper presents laboratory and in situ studies carried out on a 200 000 m(3) large clayey silt compacted embankment. Laboratory studies carried out on undeformed block samples included index tests, strength tests and water retention curves using the filter paper technique. Grain size analyses with and without a deflocculating agent clearly showed the existence of grain clusters, which appear to be naturally formed. Field instrumentation installed at depths from 0.25 m to 1.0 m included tensiometers, equitensiometers, time domain reflectometry and geothermometers. Pluviometer data from a nearby weather station are also used to analyse the field data. The ranges of water content and suction values were measured, both of which correlated well with the pluviometer data. The water retention curves including laboratory and field data showed a bimodal shape, consistent with the presence of microand macropores shown in the grain size analysis.

Debris and smear removal in flattened root canals after use of different irrigant agitation protocols

Scanning electron microscopy (SEM) can be used to analyze the presence of debris and smear layer on the internal walls of root canal. This study evaluated the debris and smear removal in flattened root canals using SEM after use of different irrigant agitation protocols. Fifty mandibular incisors were distributed into five groups (n = 10) according to the irrigant agitation protocol used during chemomechanical preparation: conventional syringe irrigation with NaviTip needle (no activation), active scrubbing of irrigant with brush-covered NaviTip FX needle, manual dynamic irrigation, continuous passive ultrasonic irrigation, and apical negative pressure irrigation (EndoVac system). Canals were irrigated with 5 mL of 2.5% NaOCl at each change of instrument and received a final flush with 17% EDTA for 1 min. After instrumentation, the roots were split longitudinally and SEM micrographs at x 100 and x 1,000 were taken to evaluate the amount of debris and smear layer, respectively, in each third. Data were analyzed by KruskalWallis and Dunn's post-hoc tests (a = 5%). Manual dynamic activation left significantly (p < 0.05) more debris inside the canals than the other protocols, while ultrasonic irrigation and EndoVac were the most effective (p < 0.05) for debris removal. Regarding the removal of smear layer, there was no statistically significant difference (p > 0.05) either among the irrigant agitation protocols or between the protocolcanal third interactions. Although none of the irrigant agitation protocols completely removed debris and smear layer from flattened root canals, the machine-assisted agitation systems (ultrasound and EndoVac) removed more debris than the manual techniques. Microsc. Res. Tech. 75:781790, 2012. (C) 2011 Wiley Periodicals, Inc.

Measurement of the concentration and size of aerosol particles and identification of the sources in orthopedic surgeries

In this study, the measurement of the concentration and size of particles and the identification of their sources were carried out at five orthopedic surgeries. The aerosol concentration and particle size distribution, ranging from 0.3 mu m 10 mu m, were measured and related to the type of indoor activity. The handling of surgical linen and gowns, handling of the patient, use of electrosurgical apparatus, use of a bone saw, handling of equipment, and cleaning of the room were identified as the most important sources of particles, with each of these activities posing different risks to the health of the patients and workers. The results showed that most of the particles were above 0.5 mu m and that there was a strong correlation among all particles of sizes above 1 mu m. Particles with diameters in the range of 0.3 mu m-0.5 mu m had a good correlation only with particles in the ranges of 0.5 mu m-1.0 mu m and 1.0 mu m-3.0 mu m in three of the surgeries analyzed. Findings led to the conclusion that most of the events responsible for generating aerosol particles in an orthopedic surgery room are brief, intermittent, and highly variable, thus requiring the use of specific instrumentation for their continuous identification and characterization.