Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 114
Filter
1.
Meat Sci ; 214: 109523, 2024 Aug.
Article in English | MEDLINE | ID: mdl-38692013

ABSTRACT

Salt content standardization in dry-cured ham production is complex as there are many factors that influence salt uptake. The aim of this work was to study and model salt uptake as a function of salting time and the characteristics of green ham in two different ham types using a large amount of data obtained from an inline non-invasive characterization technology. The usefulness of these models to standardize the salt content of the industrial production was also evaluated. Magnetic induction technology was used to characterize lean and fatty hams in order to further model the salt uptake using different statistical methods. Salt content increased with the salting time showing an asymptotic behaviour which was lower in fatty hams. The best models were those that considered the salting time, weight, and fat content of hams as model independent variables. These models are helpful for salt content standardization within the industry and can be used to simulate process modifications and avoid the time-consuming and costly trial and error tests.


Subject(s)
Food Handling , Meat Products , Sodium Chloride, Dietary , Animals , Meat Products/analysis , Meat Products/standards , Sodium Chloride, Dietary/analysis , Food Handling/methods , Swine
2.
Spectrochim Acta A Mol Biomol Spectrosc ; 284: 121776, 2023 Jan 05.
Article in English | MEDLINE | ID: mdl-36070673

ABSTRACT

Ammonia borane, as a source of hydrogen, has attracted much attention due to its high hydrogen content, low molecular weight, and high stability in solution. However, the process and enhancement of hydrogen release must be done practically under ambient conditions. For this work, Raman spectroscopy, principal component analysis (PCA), and molecular simulation were applied to study the hydrogen release process of ammonia borane. Three stages of release were observed from room temperature to 1300 °C. The shift, the appearance, and the disappearance of the Raman bands were evident in the whole process. In-situ monitoring of Raman and PCA, with four different heating rates between 70 and 130 °C, was done; ammonia borane showed visible variations in its first release step, in which a fast rate helped reduce distortion in the release process. Finally, molecular simulation of ammonia borane using the Density Functional Theory (DFT) in calculations showed that dihedral rotation and stretching of the hydrogen bonds can occur before the first release step.


Subject(s)
Boranes , Ammonia , Boranes/chemistry , Heating , Hydrogen/chemistry , Spectrum Analysis, Raman
3.
Nat Commun ; 13(1): 72, 2022 01 10.
Article in English | MEDLINE | ID: mdl-35013232

ABSTRACT

The use of facemasks by the general population is recommended worldwide to prevent the spread of SARS-CoV-2. Despite the evidence in favour of facemasks to reduce community transmission, there is also agreement on the potential adverse effects of their prolonged usage, mainly caused by CO2 rebreathing. Herein we report the development of a sensing platform for gaseous CO2 real-time determination inside FFP2 facemasks. The system consists of an opto-chemical sensor combined with a flexible, battery-less, near-field-enabled tag with resolution and limit of detection of 103 and 140 ppm respectively, and sensor lifetime of 8 h, which is comparable with recommended FFP2 facemask usage times. We include a custom smartphone application for wireless powering, data processing, alert management, results displaying and sharing. Through performance tests during daily activity and exercise monitoring, we demonstrate its utility for non-invasive, wearable health assessment and its potential applicability for preclinical research and diagnostics.


Subject(s)
Biosensing Techniques/instrumentation , COVID-19/prevention & control , Carbon Dioxide/analysis , Masks , Personal Protective Equipment , Wearable Electronic Devices , Biosensing Techniques/methods , COVID-19/transmission , COVID-19/virology , Equipment Design , Humans , Reproducibility of Results , SARS-CoV-2/physiology
4.
Meat Sci ; 172: 108362, 2021 Feb.
Article in English | MEDLINE | ID: mdl-33161218

ABSTRACT

The aim of this study was to quantify the effects of different processing parameters on texture development and the incidence of white film and tyrosine crystals in dry-cured ham. Hams were dry-salted for 0.65, 0.8 or 1.0 days/kg. After drying for 45 days at 5 °C, they were dried at 10, 15 or 20 °C until reaching 33% weight loss and, thereafter, dried at 25 °C until reaching 36 or 40% weight loss. The salting time, drying temperature and target weight loss significantly affected the texture and incidence of white film and tyrosine crystals. A beneficial effect of drying at 20 °C on texture was found, which was especially important for low target weight loss (33%). Besides, hams dried at 20 °C and those with 40% weight loss showed higher incidence of tyrosine crystals. Contour plots and predictive models for texture can be used to define optimal processing parameters.


Subject(s)
Food Handling/methods , Meat Products/analysis , Tyrosine/analysis , Animals , Desiccation , Sodium Chloride , Sus scrofa , Temperature , Time Factors
5.
Meat Sci ; 172: 108334, 2021 Feb.
Article in English | MEDLINE | ID: mdl-33059180

ABSTRACT

The end of the elaboration process of dry-cured ham is currently decided by product weight loss and/or by an expert who carries out an evaluation of the tactile texture on the surface. The objective of this study was to define the optimal measurement conditions of an instrumental texture analysis on the surface of the dry-cured ham (ITAS), to define the end of process. 120 dry-cured hams were classified by experts into Hard (appropriate) or Soft (non-appropriate) texture groups and used to perform compression tests using different probes on three anatomical positions. Results showed that the small probe in position 2 gave the most discriminant conditions, providing representative information of the internal texture. Although classification using only weight loss was possible with an accuracy rate of 80.4% or 66.7% depending on the weight loss, the maximum classification accuracy was obtained when using ITAS in combination with weight loss. Further studies at industrial level are needed.


Subject(s)
Food Handling/instrumentation , Meat Products/analysis , Animals , Food Handling/methods , Food Preservation/methods , Meat Products/standards , Muscle, Skeletal , Sodium Chloride/analysis , Sus scrofa , Tomography, X-Ray Computed
6.
Rev. esp. investig. quir ; 24(2): 47-51, 2021. tab, ilus
Article in Spanish | IBECS | ID: ibc-219153

ABSTRACT

La oclusión parcial de la arteria celiaca o tronco celiaco es una patología generalmente de origen ateroscleroso que puede ocasionar isquemia a nivel de las vísceras digestivas de la cavidad abdominal y especialmente del intestino. Tradicionalmente se ha considerado que para tener repercusión clínica debería de afectarse por lo menos dos de las tres arterias digestivas en mayor o menor grado y esta situación es la que se mostraba como base de la actuación quirúrgica terapéutica. Con la llegada de la era endovascular, con la posibilidad de realización de procedimientos quirúrgicos menos agresivos se han incrementado las indicaciones terapéuticas realizándose los procedimientos de forma preventiva para evitar el cierre u oclusión total del vaso arterial. Se realiza un estudio prospectivo de la experiencia del servicio con la utilización de procedimeintos endovasculares. (AU)


The partial occlusion of the celiac artery or celiac trunk is a disease generally of atherosclerosis origin that can cause ischemia at the level of the digestive viscera of the abdominal cavity and especially the intestine. Traditionally, it has been considered that in order to have clinical repercussion, at least two of the three digestive arteries should be affected to a greater or lesser degree and this situation is the one that was shown as the basis of therapeutic surgical action. With the arrival of the endovascular era, with the possibility of performing less aggressive surgical procedures, the therapeutic indications have increased, with the procedures being carried out preventively to avoid the closure or total occlusion of the arterial vessel. A prospective study of the service’s experience with the use of endovascular procedures is carried out. (AU)


Subject(s)
Humans , Constriction, Pathologic , Celiac Artery , Endovascular Procedures , Celiac Artery/surgery , Retrospective Studies
7.
Arch Virol ; 165(12): 3003-3006, 2020 Dec.
Article in English | MEDLINE | ID: mdl-33025198

ABSTRACT

A significant number of new members of the genus Vitivirus have been identified recently, mainly due to the advent of high-throughput sequencing (HTS). Grapevine virus I (GVI), which was identified in New Zealand in 2018, is one of these viruses. RNAseq HTS analysis of a Greek grapevine (cv. Daphnia), revealed the presence of a GVI-like isolate (D2-1/19). Sequence analysis confirmed the classification of D2-1/19 as GVI. However, both sequence and phylogenetic data exhibited high levels of variability between D2-1/19 and the previously characterized GVI isolates. This study provides the full-length sequence of a divergent GVI isolate, adding knowledge to the limited information available about this recently identified virus.


Subject(s)
Flexiviridae/genetics , Genome, Viral , Phylogeny , Vitis/virology , Flexiviridae/isolation & purification , Greece , High-Throughput Nucleotide Sequencing , Plant Diseases/virology , Whole Genome Sequencing
8.
Talanta ; 208: 120387, 2020 Feb 01.
Article in English | MEDLINE | ID: mdl-31816777

ABSTRACT

A portable device based on a colorimetric sensor to determine the atmospheric level of CO2 gas is presented in this work. The system is based on a low-cost, low-power System on a Chip (SoC) microcontroller with integrated Wi-Fi. A user-friendly application was developed to monitor and log the CO2 measurements when the system is connected to a Wi-Fi network. The sensing membrane is directly deposited on the surface of the colour detector, thus reducing the complexity of the system. This sensing membrane is formed by a pH indicator α-naphtholphthalein, tetramethylammonium hydroxide pentahydrate, 1-ethyl-3-methylimidazolium tetrafluoroborate, Tween 20 and hydroxypropyl methylcellulose as the hydrophilic polymer. The system has been fully characterized, obtaining response and recovery times of 1.3 and 2.5 s, respectively, a limit of detection of 51 ppm, and an average resolution of 6.3 ppm. This portable device was applied for the in-situ determination of CO2 gas in the atmosphere inside classrooms in several secondary schools. The measurements were taken during complete workdays and the results were statistically compared with the same measurements taken using a commercially available non-dispersive infra-red (NDIR) device. No significant statistical differences were found between the results obtained using both devices. A complete statistical treatment of the measurements made with the proposed portable device was carried out. The obtained results show that the concentration of CO2 gas in some schools was higher than the desired concentration, with regard to influencing the student's health, safety, productivity and comfort. This demonstrates the need to control this parameter to ensure appropriate indoor environmental quality (IEQ).

11.
Benef Microbes ; 8(4): 635-643, 2017 Aug 24.
Article in English | MEDLINE | ID: mdl-28726509

ABSTRACT

Food allergies represent a serious problem affecting human health and soy proteins rank among the most allergenic proteins from food origin. The proteolytic enzymes produced by lactic acid bacteria (LAB) can hydrolyse the major allergens present in soybean, reducing their immunoreactivity. Many studies have reported the ability of LAB to ferment soy-based products; while the majority of them focus on the improvement of the sensory characteristics and functionality of soy proteins, a lack of information about the role of lactic fermentation in the reduction of immunoreactivity of these proteins exists. The aim of the present study was to evaluate the capability of the proteolytic strain Enterococcus faecalis VB43 to hydrolyse the main allergenic proteins present in soymilk and to determine the immunoreactivity of the obtained hydrolysates. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) results of fermented soymilk demonstrated complete hydrolysis of the ß-subunit from ß-conglycinin and the acidic polypeptide from glycinin. Reversed phase high performance liquid chromatography (RP-HPLC) analysis of the peptides released after hydrolysis revealed the appearance of new peptides and the disappearance of non-hydrolysed proteins, indicating extensive hydrolysis of the substrate. Results from competitive enzyme-linked immunosorbent assay (ELISA) tests clearly indicated a reduction in the immunoreactivity (more than one logarithmic unit) in the fermented sample as compared to the non-fermented control. Our results suggest that the soymilk fermented by E. faecalis VB43 may induce lower allergic responses in sensitive individuals. The strain E. faecalis VB43 may be considered as an excellent candidate to efficiently reduce the immunoreactivity of soymilk proteins.


Subject(s)
Antigens, Plant/immunology , Enterococcus faecalis/metabolism , Globulins/immunology , Seed Storage Proteins/immunology , Soy Milk/metabolism , Soybean Proteins/immunology , Antigens, Plant/chemistry , Antigens, Plant/metabolism , Chromatography, High Pressure Liquid , Electrophoresis, Polyacrylamide Gel , Enzyme-Linked Immunosorbent Assay , Fermentation , Globulins/chemistry , Globulins/metabolism , Seed Storage Proteins/chemistry , Seed Storage Proteins/metabolism , Soy Milk/chemistry , Soybean Proteins/chemistry , Soybean Proteins/metabolism , Glycine max/chemistry , Glycine max/immunology , Glycine max/metabolism , Glycine max/microbiology
12.
Anal Chem ; 89(3): 1697-1703, 2017 02 07.
Article in English | MEDLINE | ID: mdl-28208249

ABSTRACT

In this work we present a full-passive flexible multigas sensing tag for the determination of oxygen, carbon dioxide, ammonia, and relative humidity readable by a smartphone. This tag is based on near field communication (NFC) technology for energy harvesting and data transmission to a smartphone. The gas sensors show an optic response that is read through high-resolution digital color detectors. A white LED is used as the common optical excitation source for all the sensors. Only a reduced electronics with very low power consumption is required for the reading of the optical responses and data transmission to a remote user. An application for the Android operating system has been developed for the power supplying and data reception from the tag. The responses of the sensors have been calibrated and fitted to simple functions, allowing a fast prediction of the gases concentration. Cross-sensitivity has also been evaluated, finding that in most of the cases it is negligible or easily correctable using the rest of the readings. The election of the target gases has been due to their importance in the monitoring of modified atmosphere packaging. The resolutions and limits of detection measured are suitable for such kinds of applications.

13.
Article in English | MEDLINE | ID: mdl-26803750

ABSTRACT

The mole is a unit of measurement that expresses amounts of a chemical substance. Its importance lies in that the mass and the number of molecules of a substance can be determined with this value. In this work, we suggest a mathematical expression that relates the number of moles of the sample studied with the Raman signal and the experimental parameters used. In other words, with this mathematical expression it is possible to obtain quantitative information in a simple manner from Raman spectra. We have applied this method to different samples and we have observed an excellent correlation between the experimental and expected data.

14.
Int J Food Microbiol ; 196: 16-23, 2015 Mar 02.
Article in English | MEDLINE | ID: mdl-25498472

ABSTRACT

The use of solid fermentation substrate (SSF) has been appreciated by the demand for natural and healthy products. Lactic acid bacteria and bifidobacteria play a leading role in the production of novel functional foods and their behavior is practically unknown in these systems. Soy is an excellent substrate for the production of functional foods for their low cost and nutritional value. The aim of this work was to optimize different parameters involved in solid state fermentation (SSF) using selected lactic cultures to improve soybean substrate as a possible strategy for the elaboration of new soy food with enhanced functional and nutritional properties. Soy flour and selected lactic cultures were used under different conditions to optimize the soy SSF. The measured responses were bacterial growth, free amino acids and ß-glucosidase activity, which were analyzed by applying response surface methodology. Based on the proposed statistical model, different fermentation conditions were raised by varying the moisture content (50-80%) of the soy substrate and temperature of incubation (31-43°C). The effect of inoculum amount was also investigated. These studies demonstrated the ability of selected strains (Lactobacillus paracasei subsp. paracasei and Bifidobacterium longum) to grow with strain-dependent behavior on the SSF system. ß-Glucosidase activity was evident in both strains and L. paracasei subsp. paracasei was able to increase the free amino acids at the end of fermentation under assayed conditions. The used statistical model has allowed the optimization of fermentation parameters on soy SSF by selected lactic strains. Besides, the possibility to work with lower initial bacterial amounts to obtain results with significant technological impact was demonstrated.


Subject(s)
Bifidobacterium/metabolism , Fermentation , Food Microbiology , Glycine max/microbiology , Lactobacillus/metabolism , Functional Food/microbiology , Lactobacillaceae/metabolism , Soybean Proteins/metabolism
15.
Eur J Clin Microbiol Infect Dis ; 33(8): 1391-9, 2014 Aug.
Article in English | MEDLINE | ID: mdl-24599708

ABSTRACT

Reliable, quick and low-cost methods are needed for the early detection of multidrug-resistant and highly virulent high-risk B2 and D Escherichia coli clones or clonal complexes (HiRCC). Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) seems to have a good discriminatory potential at different subspecies levels, but it was never evaluated for the discrimination of E. coli clones. We assessed the potential of MALDI-TOF MS coupled to multivariate data analysis to discriminate representative E. coli B2 and D HiRCC. Seventy-three E. coli isolates from B2 (including ST131 and B2 non-ST131 clones) and D (ST69, ST393, ST405) with variable pulsed-field gel electrophoresis (PFGE) patterns, origins and dates (1980-2010) were tested. MS spectra were acquired from independent extracts obtained from different plate cultures in two different Microflex LT MALDI-TOF devices (Bruker) after a standard extraction procedure. MALDI-TOF MS fingerprinting analysis revealed a good discriminatory ability between the four HiRCC analysed (ST131, ST69, ST405, ST393) and between B2 ST131 and other B2 non-ST131 isolates. Clusters defined by MALDI-TOF MS were consistent with the clonal complexes assigned by multilocus sequence typing (MLST), although differences were detected regarding the composition of clusters obtained by the comparison of PFGE profiles. We demonstrate, for the first time, that characteristic mass fingerprints of different E. coli HiRCC are sufficiently discriminatory and robust to enable their differentiation by MALDI-TOF MS, which might represent a promising tool for the optimisation of infection control, individual patient management and large-scale epidemiological studies of public health relevance. The good correlation between phenotypic and genotypic features further corroborates phylogenetic relationships delineated by MLST.


Subject(s)
Escherichia coli Infections/diagnosis , Shiga-Toxigenic Escherichia coli/genetics , Animals , Bacterial Typing Techniques , Cluster Analysis , Diagnosis, Differential , Early Diagnosis , Escherichia coli Infections/microbiology , Humans , Multilocus Sequence Typing , Phylogeny , Risk , Shiga-Toxigenic Escherichia coli/isolation & purification , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
16.
Anal Chem ; 85(22): 11098-105, 2013 Nov 19.
Article in English | MEDLINE | ID: mdl-24116378

ABSTRACT

In this work, a radiofrequency identification (RFID) tag with an optical indicator for the measurement of gaseous oxygen is described. It consists of an O2 sensing membrane of PtOEP together with a full electronic system for RFID communication, all printed on a flexible substrate. The membrane is excited by an LED at 385 nm wavelength and the intensity of the luminescence generated is registered by means of a digital color detector. The output data corresponding to the red coordinate of the RGB color space is directly related to the concentration of O2, and it is sent to a microcontroller. The RFID tag is designed and implemented by screen printing on a flexible substrate for the wireless transmission of the measurement to a remote reader. It can operate in both active and passive mode, obtaining the power supply from the electromagnetic waves of the RFID reader or from a small battery, respectively. This system has been fully characterized and calibrated including temperature drifts, showing a high-resolution performance that allows measurement of very low values of oxygen content. Therefore this system is perfectly suitable for its use in modified atmosphere packaging where the oxygen concentration is reduced below 2%. As the reading of the O2 concentration inside the envelope is carried out with an external RFID reader using wireless communication, there is no need for perforations for probes or wires, so the packaging remains completely closed. With the presented device, a limit of detection of 40 ppm and a resolution as low as 0.1 ppm of O2 can be reached with a low power consumption of 3.55 mA.


Subject(s)
Light , Luminescence , Oxygen/analysis , Radio Frequency Identification Device/methods , Printing
17.
Eur J Clin Microbiol Infect Dis ; 32(6): 769-72, 2013 Jun.
Article in English | MEDLINE | ID: mdl-23271676

ABSTRACT

The purpose of the study was to describe the microbiological and clinical features of ten cases of lower respiratory tract infection due to Corynebacterium striatum, Corynebacterium propinquum and Corynebacterium pseudodiphtheriticum. Respiratory samples were recovered from hospitalised patients who were diagnosed of pneumonia and exacerbations of chronic respiratory infections. The samples were Gram-stained and seeded on conventional bacterial growing media. Bacteria were identified by matrix-assisted linear desorption/ionisation-time-of-flight mass spectrometry (MALDI-TOF MS). Antibiotic susceptibility was tested by the disk diffusion method. All patients presented an acute respiratory onset, most of them in the context of an underlying disease and/or immunosuppression. In all patients, the microscopical examination of Gram-stained respiratory samples showed numerous polymorphonuclear cells and Gram-positive bacilli, suggestive of the Corynebacterium morphotype. A pure culture growth of Corynebacterium was obtained in the majority (72 %) of samples. The conclusions are that non-diphtheriae Corynebacterium species are an emerging cause of respiratory infection among patients with chronic respiratory disease and/or immunosuppression, and cannot always be considered as mere colonisers. The microorganism's predominance in Gram-stained purulent respiratory samples together with abundant growth in the culture is the key for the microbiological diagnosis.


Subject(s)
Communicable Diseases, Emerging/diagnosis , Communicable Diseases, Emerging/microbiology , Corynebacterium Infections/diagnosis , Corynebacterium/classification , Respiratory Tract Infections/diagnosis , Respiratory Tract Infections/microbiology , Aged , Aged, 80 and over , Communicable Diseases, Emerging/complications , Corynebacterium/isolation & purification , Corynebacterium Infections/complications , Databases, Factual , Female , Humans , Male , Middle Aged , Respiratory Tract Infections/complications , Retrospective Studies , Sputum/cytology , Sputum/microbiology
18.
Am J Transplant ; 13(1): 184-91, 2013 Jan.
Article in English | MEDLINE | ID: mdl-23126562

ABSTRACT

Over the last decade the age of liver transplant (LT) recipients and the likelihood of coronary artery disease (CAD) in this population have increased. There are no multicenter studies that have examined the impact of CAD on LT outcomes. In this historical cohort study, we identified adult LT recipients who underwent angiography prior to transplantation at seven institutions over a 12-year period. For each patient we recorded demographic data, recipient and donor risk factors, duration of follow-up, the presence of angiographically proven obstructive CAD (≥50% stenosis) and post-LT survival. Obstructive CAD was present in 151 of 630 patients, the CAD(+) group. Nonobstructive CAD was found in 479 patients, the CAD(-) group. Patient survival was similar for the CAD(+) group (adjusted HR 1.13, CI = [0.79, 1.62], p = 0.493) compared to the CAD(-) group. The CAD(+) patients were further stratified into severe (CADsev, >70% stenosis, n = 96), and moderate CAD (CADmod, 50-70% stenosis, n = 55) groups. Survival for the CADsev (adjusted HR = 1.26, CI = [0.83, 1.91], p = 0.277) and CADmod (adjusted HR = 0.93, CI = [0.52, 1.66], p = 0.797) groups were similar to the CAD(-) group. We conclude that when current CAD treatment strategies are employed prior to transplant, post-LT survival is not significantly different between patients with and without obstructive CAD.


Subject(s)
Coronary Angiography , Coronary Artery Disease/complications , Liver Transplantation , Treatment Outcome , Aged , Coronary Artery Disease/diagnosis , Female , Humans , Male , Middle Aged , Risk Factors
19.
J Clin Microbiol ; 50(3): 1096-8, 2012 Mar.
Article in English | MEDLINE | ID: mdl-22170922

ABSTRACT

Clonal isolates identified as various nonfermentative Gram-negative bacilli over a 5-year period from sputum cultures of a 30-year-old cystic fibrosis patient were successfully reidentified as Pandoraea sputorum by combining 16S rRNA sequencing and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Decreased lung function improved after 1 year of azithromycin and inhaled 7%-hypertonic saline treatment.


Subject(s)
Burkholderiaceae/classification , Burkholderiaceae/isolation & purification , Cystic Fibrosis/complications , Gram-Negative Bacterial Infections/diagnosis , Gram-Negative Bacterial Infections/microbiology , Adult , Anti-Bacterial Agents/therapeutic use , Azithromycin/therapeutic use , Burkholderiaceae/chemistry , Burkholderiaceae/genetics , Cluster Analysis , DNA Fingerprinting , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , DNA, Ribosomal/chemistry , DNA, Ribosomal/genetics , Electrophoresis, Gel, Pulsed-Field , Female , Gram-Negative Bacterial Infections/drug therapy , Humans , Lung/physiopathology , Mass Spectrometry , Molecular Sequence Data , Phylogeny , RNA, Ribosomal, 16S/genetics , Respiratory Function Tests , Sequence Analysis, DNA , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization , Sputum/microbiology
20.
Phys Med Biol ; 56(12): 3535-50, 2011 Jun 21.
Article in English | MEDLINE | ID: mdl-21606552

ABSTRACT

New thermal compensation methods suitable for p-channel MOSFET (pMOS) dosimeters with the usual dose readout procedure based on a constant drain current are presented. Measuring the source-drain voltage shifts for two or three different drain currents and knowing the value of the zero-temperature coefficient drain current, I(ZTC), the thermal drift of source-drain or threshold voltages can be significantly reduced. Analytical expressions for the thermal compensation have been theoretically deduced on the basis of a linear dependence on temperature of the parameters involved. The proposed thermal modelling has been experimentally proven. These methods have been applied to a group of ten commercial pMOS transistors (3N163). The thermal coefficients of the source-drain voltage and the threshold voltage were reduced from -3.0 mV °C(-1), in the worst case, down to -70 µV °C(-1). This means a thermal drift of -2.4 mGy °C(-1) for the dosimeter. When analysing the thermal drifts of all the studied transistors, in the temperature range from 19 to 36 °C, uncertainty was obtained in the threshold voltage due to a thermal drift of ±9 mGy (2 SD), a commonly acceptable value in most radiotherapy treatments. The procedures described herein provide thermal drift reduction comparable to that of other technological or numerical strategies, but can be used in a very simple and low-cost dosimetry sensor.


Subject(s)
Electric Conductivity , Metals/chemistry , Oxides/chemistry , Radiometry/instrumentation , Temperature , Transistors, Electronic , Artifacts , Reproducibility of Results
SELECTION OF CITATIONS
SEARCH DETAIL
...