Healthy human skin Kelvin-Voigt fractional and spring-pot biomarkers reconstruction using torsional wave elastography.

This paper presents a novel method for reconstructing skin parameters using Probabilistic Inverse Problem (PIP) techniques and Torsional Wave Elastography (TWE) rheological modeling. A comprehensive examination was conducted to compare and analyze the theoretical, time-of-flight (TOF), and full-signal waveform (FSW) approaches. The objective was the identification of the most effective method for the estimation of mechanical parameters. Initially, the most appropriate rheological model for the simulation of skin tissue behavior was determined through the application and comparison of two models, spring pot (SP) and Kevin Voigt fractional derivative (KVFD). A numerical model was developed using the chosen rheological models. The collection of experimental data from 15 volunteers utilizing a TWE sensor was crucial for obtaining significant information for the reconstruction process. The study sample consisted of five male and ten female subjects ranging in age from 25 to 60 years. The procedure was performed on the ventral forearm region of the participants. The process of reconstructing skin tissue parameters was carried out using PIP techniques. The experimental findings were compared with the numerical results. The three methods considered (theoretical, TOF, FSW) have been used. The efficacy of TOF and FSW was then compared with theoretical method. The findings of the study demonstrate that the FSW and TOF techniques successfully reconstructed the parameters of the skin tissue in all of the models. The SP model's the skin tissue η values ranged from 8 to 12 P a · s , as indicated by the TOF reconstruction parameters. η values found by the KVFD model ranged from 4.1 to 9.3 P a · s . The µ values generated by the KVFD model range between 0.61 and 96.86 kPa. However, FSW parameters reveal that skin tissue η values for the SP model ranged from 7.8 to 12 P a · s . The KVFD model determined η values between 6.3 and 9.5 P a · s . The KVFD model presents µ values ranging between 26.02 and 122.19 kPa. It is shown that the rheological model that best describes the nature of the skin is the SP model and its simplicity as it requires only two parameters, in contrast to the three parameters required by the KVFD model. Therefore, this work provides a valuable addition to the area of dermatology, with possible implications for clinical practice.

A quick method for identifying radiolytic hydrocarbons in low-fat-containing food.

BACKGROUND: As radiation-induced alterations of the lipid fraction of foods are related to their initial fat content, concentrations of fat degradation products used as irradiation markers are expected to be lower when irradiating low-fat-containing foods. Thus the sensitivity required when applying analytical methods for identifying irradiation markers in foods eventually depends on their respective amounts of fat. The aim of this study was to perform the qualitative analysis of characteristic hydrocarbons resulting from irradiation of samples with a fat content as low as 25 g kg(-1). RESULTS: A rapid extraction using a small amount of ethyl acetate was the unique sample pretreatment required to accomplish the analysis of radiolytic markers by using on-line coupling of reverse phase liquid chromatography and gas chromatography with mass spectrometry detection (RPLC/GC/MS). Efficient elimination of the large volumes (up to 2170 µL) directly transferred from LC to GC was achieved by optimising the operation mode of the through-oven transfer adsorption/desorption system used as interface. CONCLUSION: The reported procedure allowed confirmation, in less than 65 min, of the occurrence of up to five irradiation markers, namely n-pentadecane, 1-hexadecene, 1,7-hexadecadiene, n-heptadecane and 8-heptadecene, in cooked ham irradiated at doses as low as 2 kGy.

Factors influencing delay in the diagnosis of colorectal cancer: a study protocol.

BACKGROUND: Colorectal cancer (CRC) is the second most frequent tumor in developed countries. Since survival from CRC depends mostly on disease stage at the time of diagnosis, individuals with symptoms or signs suspicious of CRC should be examined without delay. Many factors, however, intervene between symptom onset and diagnosis. This study was designed to: 1) Describe the diagnostic process of CRC from the onset of first symptoms to diagnosis and treatment. 2) Establish the time interval from initial symptoms to diagnosis and treatment, globally and considering patient's and doctors' delay, with the latter due to family physician and/or hospital services. 3) Identify the factors related to defined types of delay. 4) Assess the concordance between information included in primary health care and hospital clinical records regarding onset of first symptoms. METHODS: Descriptive study, coordinated, with 5 participant groups of 5 different Spanish regions (Balearic Islands, Galicia, Catalunya, Aragon and Valencia Health Districts), with a total of 8 acute public hospitals and 140 primary care centers. Incident cases of CRC during the study period, as identified from pathology services at the involved hospitals. A sample size of 896 subjects has been estimated, 150 subjects for each participant group. Information will be collected through patient interviews and primary health care and hospital clinical records. Patient variables will include sociodemographic variables, family history of cancer, symptom perception, and confidence in the family physician; tumor variables will include tumor site, histological type, grade and stage; symptom variables will include date of onset, type and number of symptoms; health system variables will include number of patient contacts with family physician, type and content of the referral, hospital services attending the patient, diagnostic modalities and results; and delay intervals, including global delays and delays attributed to the patient, family physician and hospital. DISCUSSION: To obtain a nonrestricted sample of patients with CRC we have minimized selection risk by identifying the patients from pathology services. A greater constraint may be associated with information sources based on clinical records. Due to inherent features of coordinated studies, it is important to standardize the collection of information.

Automated determination of pesticide residues in olive oil by on-line reversed-phase liquid chromatography-gas chromatography using the through oven transfer adsorption desorption interface with electron-capture and nitrogen-phosphorus detectors operating simultaneously.

A rapid method for the multiresidue analysis of pesticides in olive oil is presented. Pesticides are analyzed by on-line coupling reversed-phase liquid chromatography-gas chromatography using the through oven transfer adsorption desorption (TOTAD) interface with subsequent simultaneous electron-capture and nitrogen-phosphorus detection by post-column splitter. An autosampler is employed and the olive oil is simply filtered before the chromatographic analysis. Organophosphorus, organochlorine and triazine pesticides are determined in one run. The limits of detection are below the required maximum residue levels and calibration curves are linear in the range tested. Repeatabilities (intra-day and inter-days) are good. The method was satisfactory applied to the routine analysis of numerous olive oil samples.

Large volume GC injection for the analysis of organophosphorus pesticides in vegetables using the through oven transfer adsorption desorption (TOTAD) interface.

A simple, rapid and sensitive multiresidue method has been developed for the determination in vegetables of organophosphorus pesticides commonly used in crop protection. Pesticide residues are extracted from samples with a small amount of ethyl acetate and anhydrous sodium sulfate. No additional concentration and cleanup steps are necessary. Analyses are performed by large volume GC injection using the through oven transfer adsorption desorption (TOTAD) interface. The calculated limits of detection for each pesticide injecting 50 microL of extract and using an NPD are lower than 0.35 microg/kg which is much lower than the maximum residues levels (MRLs) established by European legislation. Repeatability studies yielded a relative standard deviation lower than 10% in all cases. The method was applied to the analysis of eggplant, lettuce, pepper, cucumber, and tomato.

Determination of organophosphorus and triazine pesticides in olive oil by on-line coupling reversed-phase liquid chromatography/gas chromatography with nitrogen-phosphorus detection and an automated through-oven transfer adsorption-desorption interface.

A method is described for the simultaneous determination of organophosphorus and triazine pesticides in olive oil, whereby reversed-phase liquid chromatography (LC) is coupled to gas chromatography by means of an automated through-oven transfer adsorption-desorption (TOTAD) interface. The olive oil needs to be filtered only before it is loaded into the liquid chromatograph, where preseparation of the pesticide residues from the other olive oil components is carried out by using methanol-water as the eluant. The LC fraction containing the pesticides is automatically transferred to the gas chromatograph by using the TOTAD interface, which almost totally eliminates the solvent, so that water-sensitive detectors such as the nitrogen-phosphorus detector can be used. Detection limits range from 0.07 to 0.38 microg/L for organophosphorus pesticides and from 6.0 to 7.0 microg/L for triazines. The results were compared with those obtained by flame ionization detection.

Analysis of polycyclic aromatic hydrocarbons in aqueous samples by large volume injection gas chromatography-mass spectrometry using the through oven transfer adsorption desorption interface.

A new procedure for the determination of 17 polycyclic aromatic hydrocarbons (PAHs) in aqueous samples by large volume injection-gas chromatography-mass spectrometry (LVI-GC-MS) using the Through Oven Transfer Adsorption Desorption (TOTAD) interface with nitrogen for solvent elimination is developed and validated. Up to 75mL of aqueous samples were injected to be sure that good solvent elimination were achieved, although 500µL were sufficient to achieve the required sensitivity.The performance of the developed method can be considered good: the relative standard deviation (RSD), (n=3) was lower than 13.8% for all the target analytes, the concentration of each PAH being 0.25µgL(-1), the limit of detection and limit of quantitation ranged from 21.5 to 211.0 ng L(-1) and from 71.7 to 703.3ngL(-1) respectively, and the correlation coefficients (R(2)) were all higher than 0.9764 in the 1-16µgL(-1) range.

Use of nitrogen to remove solvent from through oven transfer adsorption desorption interface during analysis of polycyclic aromatic hydrocarbons by large volume injection in gas chromatography.

The through oven transfer adsorption desorption (TOTAD) interface allows large volume injection (LVI) in gas chromatography and the on-line coupling of liquid chromatography and gas chromatography (LC-GC), enabling the LC step to be carried out in normal as well as in reversed phase. However, large amounts of helium, which is both expensive and scarce, are necessary for solvent elimination. We describe how slight modification of the interface and the operating mode allows nitrogen to be used during the solvent elimination steps. In order to evaluate the performance of the new system, volumes ranging from 20 to 100µL of methanolic solutions of four polycyclic aromatic hydrocarbons (PAHs) were sampled. No significant differences were found in the repeatability and sensitivity of the analyses of standard PAH solutions when using nitrogen or helium. The performance using the proposed modification was similar and equally satisfactory when using nitrogen or helium for solvent elimination in the TOTAD interface. In conclusion, the use of nitrogen will make analyses less expensive.

Large volume injection in gas chromatography using the through oven transfer adsorption desorption interface operating under vacuum.

The present work describes a modification of the Through Oven Transfer Adsorption Desorption (TOTAD) interface, consisting of coupling a vacuum system to reduce the consumption of the helium needed to totally remove the eluent for large volume injection (LVI) in gas chromatography (GC). Two different retention materials in the liner of the TOTAD interface were evaluated: Tenax TA, which was seen to be unsuitable for working under vacuum conditions, and polydimethylsiloxane (PDMS), which provided satisfactory repeatability as well as a good sensitivity. No variability was observed in the retention times in either case. Solutions containing organophosphorous pesticides in two different solvents, a polar (methanol/water) and a non-polar (hexane) solvent, were used to evaluate the modification. The vacuum system coupled to the TOTAD interface allowed up to 90% helium to be saved without affecting the performance.

Age-period-cohort effect on lung cancer mortality in southern Spain.

The aim of this study was to evaluate the age-period-cohort effects on lung cancer mortality in Andalusia (southern Spain) as a whole as well as in each of its eight provinces during the period between 1981 and 2008. A population-based ecological study was conducted. In all, 74 255 deaths from lung cancer were analysed for individuals aged between 40 and 84 years who died in Andalusia during the period of study. A nonlinear regression model was estimated for both sexes and each geographical area. The effects of age, year of death and birth cohort were parameterized using B-spline smoothing functions. There is an upward trend in mortality by age until around the age of 75 years, from which point the trend turns downwards for men and remains stable for women. The analysis of the cohort effect revealed a steady fall in the lung cancer mortality risk for male generations born after 1950. The mortality risk for women is increasing for the generations born after 1932. The death rates for men declined from 1995 until the end of the study period. For women, the death rates increased from the end of the 1990s. There is a similar age-period-cohort effect on lung cancer mortality in all the provinces of Andalusia and for Andalusia as a whole. If the current trends continue, it can be expected that these effects will continue to reduce male mortality and increase female mortality.

The cochlear implant as a tinnitus treatment.

INTRODUCTION AND OBJECTIVES: Tinnitus is a symptom of high prevalence in patients with cochlear pathology. We studied the evolution of tinnitus in patients undergoing unilateral cochlear implantation for treatment of profound hearing loss. METHODS: This was a longitudinal, retrospective study of patients that underwent unilateral cochlear implantation and who had bilateral tinnitus. Tinnitus was assessed quantitatively and qualitatively before surgery and at 6 and 12 months after surgery. RESULTS: We evaluated 20 patients that underwent unilateral cochlear implantation with a Nucleus(®) CI24RE Contour Advance™ electrode device. During the periods in which the device was in operation, improvement or disappearance of tinnitus was evidenced in the ipsilateral ear in 65% of patients, and in the contralateral ear, in 50%. In periods in which the device was disconnected, improvement or disappearance of tinnitus was found in the ipsilateral ear in 50% of patients, and in the ear contralateral to the implant in 45% of the patients. In 10% of the patients, a new tinnitus appeared in the ipsilateral ear. CONCLUSIONS: The patients with profound hearing loss and bilateral tinnitus treated with unilateral cochlear implantation improved in a high percentage of cases, in the ipsilateral ear and in the contralateral ear.

On-line derivatization with on-line coupled normal phase liquid chromatography-gas chromatography using the through oven transfer adsorption desorption interface: application to the analysis of total sterols in edible oils.

In the present work on-line derivatization is combined with on-line normal phase liquid chromatography-gas chromatography (NPLC-GC) to analyze total sterols in edible oils. The method uses the TOTAD interface with an additional LC injection valve to automatically introduce the derivatization reagent. The derivatization reaction takes place in the adsorbent material located inside the liner of the TOTAD interface. The samples were saponified with potassium hydroxide in an ethanolic solution and the unsaponifiable fraction was extracted with diethyl ether. The extract was then analyzed by on-line derivatization with on-line NPLC-GC, avoiding the laborious thin layer chromatography and off-line derivatization steps used in the Official European Union (EU) method. The relative standard deviations (RSDs) from the absolute peak area were lower than 14% except for campestanol. No variability in retention time was observed. Limits of detection (LODs) were less than 8.82 mg/kg. Different edible oils were analyzed using the proposed method and the results obtained were compared with those obtained using the Official EU method. There was good agreement between both methods for all the sterols analyzed.

Analysis of free and esterified sterols in edible oils by online reversed phase liquid chromatography-gas chromatography (RPLC-GC) using the through oven transfer adsorption desorption (TOTAD) interface.

An online reversed phase liquid chromatography-gas chromatography (RPLC-GC) method is proposed to quantify free, total and esterified sterols of edible oils. To determine free sterols the diluted oils are injected into the liquid chromatograph, where free sterols are separated from triglycerides and the sterol fraction is automatically transferred to the gas chromatograph to be analysed. To determine total sterols the samples were saponified with potassium hydroxide in ethanolic solution and the unsaponifiable fraction was extracted with diethyl ether. The extract was then analysed by RPLC-GC, avoiding the laborious thin layer chromatography step used in the Official European Union (EU) Method. The relative standard deviations (RSDs) from the absolute peak area varied from 7.6% to 15.8%. Limits of detection (LODs) were less than 8.5 mg/kg. No variability in retention time was observed. The method was applied to the determination of total sterols in edible oil samples and the results were compared with those obtained with the Official EU Method. Good agreement was found between both methods, except in the case of campesterol.

Analysis of steroids in human urine by on line liquid chromatography-gas chromatography-mass spectrometry using the Through Oven Transfer Adsorption Desorption interface and a fraction collector.

Anti-doping laboratories accredited by the WADA (World Anti-Doping Agency) must have available methods capable of detecting synthetic steroids at concentrations below 10 ng mL(-1) and, at the same time, be able to quantify endogenous steroids with accuracy. The unequivocal identification of the steroids must be carried out by GC-MS. In this manuscript we describe a new method by on-line coupled liquid chromatography-gas chromatography (LC-GC) using the Through Oven Transfer Adsorption Desorption (TOTAD) interface and mass spectrometer (MS) detector. By this means, all the analyte eluted in the LC stage are automatically transferred to the GC, avoiding the contamination associated with manipulation of the sample. A newly designed fraction collector is described for the first time. The collector permits the different fractions eluted in LC to be stored and sent individually to the GC by means of the TOTAD interface. The detection limits attained, measured in gas chromatography-mass spectrometry (GC-MS) in SCAN mode, vary between 0.5 and 3.4 ng mL(-1), and the method, once the sample is derivatized, is completely automatic.

Analysis of wax esters in edible oils by automated on-line coupling liquid chromatography-gas chromatography using the through oven transfer adsorption desorption (TOTAD) interface.

An automated method for the direct analysis of wax esters in edible oils is presented. The proposed method uses the TOTAD (through oven transfer adsorption desorption) interface for the on-line coupling of normal phase liquid chromatography and gas chromatography. In this fully automated system, the oil with C32 wax ester as internal standard and diluted with heptane is injected directly with no sample pre-treatment step other than filtration. The proposed method allows analysis of different wax esters, and is simpler and faster than the European Union Official Method, which is tedious and time-consuming. The obtained results closely match the certified values obtained from the median of the analytical results of the inter-labs certification study. Relative standard deviations of the concentrations are less than 5%. The method is appropriate for routine analysis as it is totally automated.

Large volume injection of water in gas chromatography­mass spectrometry using the Through Oven Transfer Adsorption Desorption interface: Application to multiresidue analysis of pesticides.

In the present work, the potential of the Through Oven Transfer Adsorption Desorption (TOTAD) interface for the large volume injection (LVI) of aqueous samples in gas chromatography (GC) using a mass spectrometry (MS) detector is demonstrated. To this end, a new method for the determination of pesticides in water is presented, being the first developed method in which injection of large amounts of polar solvents using the TOTAD interface and an MS detector are combined, is applied to the determination of pesticides in water. Water samples, as large as 5 ml, were directly injected into a capillary GC. No sample pre-treatment step other than simple filtration was needed. The TOTAD interface allows the introduction of several millilitres of water, while maintaining good chromatographic characteristics. The water is almost entirely eliminated, so that LVI of aqueous samples and an MS detector can be used without problems. Organophosphorus, organochlorine, and triazine pesticides were determined in one run. Calibration curves were linear in the range tested and the sensitivity achieved injecting 5 ml of water sample was sufficient for most of the target pesticides but not for all of them. Sensitivity of the analysis can be improved by increasing the sample volume. No variability was observed in the retention times and relative standard deviations from absolute peak areas were good, considering that they corresponded to the overall analysis. The method was applied to the analysis of pesticide residues in real water samples.

Analysis of pesticides in nuts by online reversed-phase liquid chromatography-gas chromatography using the through-oven transfer adsorption/desorption interface.

A new method to determine pesticide residues in nuts is presented, in which the pesticides are extracted from samples with a small amount of ethyl acetate and anhydrous sodium sulfate. No additional cleanup or concentration steps are necessary. The extract is directly injected into the high-pressure liquid chromatograph, where preseparation of the pesticide residues from other components coextracted from the nuts is carried out using methanol/water as the eluent. The selected liquid chromatography fraction containing the pesticides is automatically transferred to the gas chromatograph using the through-oven transfer adsorption/desorption interface. The calculated limits of detection for each pesticide varied from 0.1 to 61.3 microg/kg. The repeatabilities of the analysis and the overall procedure (extraction and analysis) were satisfactory. No variations in the retention time were observed. The method was applied to the analysis of pistachio nut, peanut, walnut, hazelnut, and sunflower seed.