Biomedical subjects
Publications and source records attributed to R Herrero.
We investigate propagation of light pulses in photonic crystals in the vicinity of the zero diffraction point. We show that Gaussian pulses due to nonzero width of their temporal spectrum spread weakly in space and time during the propagation. We also find the family of nonspreading pulses, propagating invariantly in the vicinity of the zero diffraction point of photonic crystals.
The protonated alga Sargassum muticum was employed in batch desorption studies to find the most appropriate eluting agent for Cd(II)-laden biomass regeneration. Eleven types of eluting solutions at different concentrations were tested, finding elution efficiencies higher than 90% for most of the desorbents studied. Total organic carbon and biomass weight loss measurements were made. The reusability of the protonated alga was also studied using a fixed-bed column. Eleven consecutive sorption-regeneration cycles at a flow rate of 10 mL min(-1) were carried out for the removal of 50 mg L(-1) Cd(II) solution. A 0.1M HNO(3) solution was employed as desorbing agent. The column was operated during 605 h for sorption and 66 h for desorption, equivalent to a continuous use during 28 days, with no apparent loss of sorption performance. In these cycles, no diminution of the breakthrough time was found; although, a relative loss of sorption capacity, regarding the found in the first cycle, was observed. The slope of the breakthrough curves experiments a gradual increase reaching its maximum value for the last cycle tested (40% greater than for the first one). The maximum Cd(II) concentration elution peak was achieved in 5 min or less, and the metal effluent concentration was always lower than 0.9 mg L(-1) after 1 h of elution. The maximum concentration factor was determined to be between 55 and 109.
The protonated Sargassum muticum seaweed was studied as a possible biosorbent for cadmium removal in a fixed-bed column. The experiments were conducted in order to determine the effect of flow rate (0.42, 5, 10 and 20 mL min(-1)) and bed height (0.6 and 15.3 cm for the lowest flow rate or 7.4, 13 and 16.6 cm for the others) on breakthrough curves behaviour. The determined breakthrough and exhaustion times increased with the diminution in flow rate and with the increase in bed height. The maximum cadmium uptake capacity, obtained from the area below adsorbed cadmium concentration versus time curves, was found to remain practically constant with bed depth and flow rate. The bed depth service time (BDST) model was applied to analyse experimental data, determining the characteristic process parameters. The optimal lowest sorbent usage rate was evaluated at 2 min contact time and the minimum bed height values necessary to prevent the effluent solution concentration from exceeding 0.02 mg L(-1) at zero time were 5.3, 6.9 and 7.5 cm for flow rates of 5, 10 and 20 mL min(-1), respectively. Several empirical models proposed in the literature (Bohart-Adams, Yan, Belter and Chu models) were investigated in order to obtain the best fit of column data, describing in a simple manner the breakthrough curves. A correlation between model parameters and the variables implied in the process was attempted.
This work reports kinetic and equilibrium studies of cadmium(II) and lead(II) adsorption by the brown seaweed Cystoseira baccata. Kinetic experiments demonstrated rapid metal uptake. Kinetic data were satisfactorily described by a pseudo-second order chemical sorption process. Temperature change from 15 to 45 degrees C showed small variation on kinetic parameters. Langmuir-Freundlich equation was selected to describe the metal isotherms and the proton binding in acid-base titrations. The maximum metal uptake values were around 0.9 mmol g(-1) (101 and 186 mg g(-1) for cadmium(II) and lead(II), respectively) at pH 4.5 (raw biomass), while the number of weak acid groups were 2.2 mmol g(-1) and their proton binding constant, K(H), 10(3.67) (protonated biomass). FTIR analysis confirmed the participation of carboxyl groups in metal uptake. The metal sorption was found to increase with the solution pH reaching a plateau above pH 4. Calcium and sodium nitrate salts in solution were found to affect considerably the metal biosorption.
Protonated biomass of the seaweed Sargassum muticum was investigated for its ability to remove cadmium(II) from aqueous solutions. In this work, a nonideal, semiempirical, thermodynamically consistent (NICCA) isotherm was proposed to fit the experimental ion binding data obtained in NaNO3 0.05 mol L(-1). This model describes the competition between protons and metal ions satisfactorily. Moreover, it reflects the complexity of the macromolecular systems that take part in biosorption considering the heterogeneity of the sorbent. It was demonstrated in this work that the NICCA isotherm constitutes a great improvement with respect to a simpler Langmuir competitive equation, which was not able to describe all the experimental data satisfactorily. Potentiometric acid-base titrations in the absence of cadmium were made to estimate the maximum amount of acid functional groups (2.61 mmol g(-1)) and the conditional proton binding parameters, logK (H) (3.8) and m(H) (0.54). The values of the binding parameters for the cadmium ion were chosen to provide the best simultaneous description of the isotherm at pH 4.5, as well as the dependence of cadmium adsorption on pH. Values of logK (Cd) (3.1), n(Cd) (1.8), and p (0.19) in the case of the NICCA isotherm or logK(Cd) (2.94-3.4) for Langmuir competitive models were obtained. Kinetic experiments were performed at two different pH values (3.0 and 4.5), establishing the time dependence that represents the sorption of cadmium with a pseudo-second-order kinetic model. It was observed that 4 h is enough to ensure that the equilibrium uptake was reached.
Five different brown seaweeds, Bifurcaria bifurcata, Saccorhiza polyschides, Ascophyllum nodosum, Laminaria ochroleuca and Pelvetia caniculata were studied for their ability to remove cadmium from aqueous solution. Kinetics of cadmium adsorption by all the algae were relatively fast, with 90% of total adsorption occurring in less than 1h. These experiments could be accurately described by a pseudo-second-order rate equation, obtaining values between 1.66x10(-3) and 9.92x10(-3) g/mgmin for the sorption rate constant k. Several equilibrium adsorption isotherms were obtained for the quantitative description of cadmium uptake. The use of the Langmuir isotherm led to values between 64 and 95 mg/g for qmax and between 0.036 and 0.094 L/mg for b. The effect of pH on biosorption was also studied. Acid-base properties of algae were studied by potentiometry to determine pK values (from 3.54 to 3.98) and the total number of acid groups.
Human leukocyte antigen (HLA) variations may affect immune response to human papillomavirus infection and subsequent cervical neoplasia risk. We investigated the frequency and relationship between HLA-A-B and HLA-A-B-DR haplotypes among women with cervical cancer/high-grade lesions (n=365) and cytologically normal population controls (n=681) within three cervical neoplasia studies in the US and Costa Rica. Notable differences in haplotype frequencies were observed; the HLA-A*01-B*08 haplotype occurred in >5% of US Caucasians but in <1% of Costa Ricans. The most prevalent HLA-A*24-B*40-DR*04 haplotype in Costa Rica (5%) was found in <1% of US Caucasians. No HLA haplotype was significantly associated with cervical neoplasia, suggesting that individual allele associations reported to date (e.g. HLA-DR*13) are not likely explained by underlying haplotypes.
In recent years, there has been a significant increase in the studies concerning brown seaweed as biosorbents for metal removal owing to their high binding ability and low cost. This work reports the results of a study regarding the cadmium binding equilibria of dead biomass from the seaweed Sargassum muticum; this alga is a pest fouling organism that competes with the local fucalean species and may also interfere with the "sea industry"; therefore, it would constitute an ideal material to be used as biosorbent. Seven different treatments were tested in order to obtain a stable biomass that could be suitable for industrial use under a broad range of operational conditions. The treatments employed were protonation, chemical cross-linking with formaldehyde, KOH, Ca(OH)(2) and CaCl(2) or physical treatments with acetone and methanol. The equilibrium adsorption isotherms of Langmuir, Freundlich, and Langmuir-Freundlich were obtained for the quantitative description of the cadmium uptake. The effect of pH on biosorption equilibrium was studied at values ranging from 1 to 6, demonstrating the importance of this parameter for an accurate evaluation of the biosorption process. Maximum biosorption was found pH higher than 4.5. The maximum biosorption uptake for the raw biomass was 65 mg g(-1), while for formaldehyde cross-linking biomass the uptake increases to 99 mg g(-1) and for protonated biomass to 95 mg g(-1). Potentiometric titrations were carried out to estimate the total number of weak acid groups and to obtain their apparent pK value, 3.85, using the Katchalsky model. Kinetic studies varying cadmium concentration, algal dose, and ionic strength were carried out. Over 95% of the maximum cadmium uptake was achieved within 45 min, so the process can be considered relatively fast. A pseudo-second-order model, for the kinetics of cadmium biosorption, was shown to be able to reproduce experimental data points with accuracy.
Determinants of human papillomavirus (HPV)-16 serological conversion and persistence were assessed in a population-based cohort of 10 049 women in Guanacaste, Costa Rica. Serologic responses to HPV-16 were measured in 7986 women by VLP-based enzyme-linked immunosorbent assay at both study enrollment (1993/94) and at 5-7 years of follow-up. Seropositive women were defined as >/=5 standard deviations above the mean optical density obtained for studied virgins at enrollment (n=573). Seroconnversion (n=409), persistence (n=675), and clearance (n=541) were defined based on enrollment and follow-up serology measurements. Age-specific distributions revealed that HPV-16 seroconversion was highest among 18- to 24-year-old women, steadily declining with age; HPV-16 seropersistence was lowest in women 65+ years. In age-adjusted multivariate logistic regression models, a 10-fold risk increase for HPV-16 seroconversion was associated with HPV-16 DNA detection at enrollment and follow-up; two-fold risk of seroconversion to HPV-16 was associated with increased numbers of lifetime and recent sexual partners and smoking status. Determinants of HPV-16 seropersistence included a 1.5-fold risk increase associated with having one sexual partner during follow-up, former oral contraceptive use, and a 3-fold risk increase associated with HPV-16 DNA detection at both enrollment and follow-up. Higher HPV-16 viral load at enrollment was associated with seroconversion, and higher antibody titres at enrollment were associated with seropersistence.
To investigate the prevalence of and the risk factors for cervical infection with human papillomavirus (HPV) in an inner-city area of Ibadan, Nigeria, we interviewed and obtained a sample of cervical cells from 932 sexually active women aged 15 years or older. A total of 32 different HPV types were identified with an HPV prevalence of 26.3% overall and 24.8% among women without cervical lesions; or age-standardised to the world standard population of 28.3 and 27.3%, respectively. High-risk HPV types predominated, most notably HPV 16, 31, 35 and 58. In all, 33.5% of infections involved more than one HPV type. Unlike most populations studied so far, HPV prevalence was high not only among young women, but also in middle and old age. Single women (odds ratio, OR=2.1; 95% confidence interval, CI=1.1-3.9) and illiterate women (OR=1.7; 95%CI=1.1-2.5) showed increased HPV positivity. Associations were also found with anti-Herpes simplex-2 antibodies (OR=1.6; 95% CI: 1.1-2.1) and with the husband's extramarital relationships (OR=1.6: 95% CI: 1.0-2.6). High prevalence of HPV in all age groups may be a distinctive feature of populations where HPV transmission continues into middle age and cervical cancer incidence is very high.
Both parity and oral contraceptive use are associated with elevated circulating levels of sex hormones, at least transiently, and with increased risk of cervical cancer in human papillomavirus (HPV)-infected women. We directly evaluated whether elevations in the physiologic levels of these hormones predispose to the development of cervical neoplasia. We identified 67 premenopausal and 43 postmenopausal women with cervical intraepithelial neoplasia 2, 3, or cervical cancer (>/=CIN2) diagnosed during enrollment of a population-based cohort of 10 077 women. Four controls, two chosen randomly and two chosen from women testing positive for cancer-associated HPV, were matched to each case on menopausal status, age, days since last menses (pre), or years since menopause (post). Sex hormone-binding globulin, oestradiol, oestrone, oestrone-sulphate, dehydroepiandrosterone sulphate, and progesterone were measured in enrollment plasma. There was no consistent association between the sex hormones and risk of >/=CIN2. Excluding cases with invasive disease had a minimal impact on results. Though this case-control study was based on a well-defined population, it was limited by reliance on a single measure of hormone levels taken at the time of diagnosis. Nonetheless, our results do not support the hypothesis that plasma levels of sex hormones have an important bearing on the risk of cervical neoplasia in HPV-infected women.
The influence of body mass index (BMI) on oral cancer risk was evaluated in 375 incident cases and 375 age-gender-matched hospital-based controls. Low BMIs at diagnosis and 2 years before diagnosis were associated with significantly elevated odds ratios (OR for BMI < or =22 vs >26 kg m(-2); 3.64; 95% confidence interval, CI: 2.27-5.82 and 3.31; 95% CI: 2.04-5.39, respectively). The association with low BMI, however, tended to be weaker and nonsignificant among never smokers and never drinkers.
Human papillomavirus (HPV) seroprevalence and determinants of seropositivity were assessed in a 10049-woman population-based cohort in Guanacaste, Costa Rica. Serologic responses based on VLP-based ELISA were obtained from the plasma collected at study enrollment in 1993/1994 for HPV-16 (n=9949), HPV-18 (n=9928), HPV-31 (n=9932), and HPV-45 (n=3019). Seropositivity was defined as five standard deviations above the mean optical density obtained for studied virgins (n=573). HPV-16, -18, -31, and -45 seroprevalence was 15, 15, 16, and 11%, respectively. Of women DNA-positive for HPV-16, -18, -31, or -45, seropositivity was 45, 34, 51, and 28%, respectively. Peak HPV seroprevalence occurred a decade after DNA prevalence; lifetime number of sexual partners was the key determinant of seropositivity independent of DNA status and age. DNA- and sero-positive women showed the highest risk for concurrent CIN3/cancer, followed by DNA-positive, sero-negative women.
Non-viral factors contribute to human papillomavirus (HPV)-related cervical carcinogenesis. We investigated the role of paan chewing and dietary habits among 205 women with invasive cervical cancer (ICC) and 213 age-matched control women in Chennai, India. Odds ratios (OR) and 95% confidence intervals (CI) were computed by means of unconditional multiple regression, taking into account major correlates of ICC risk. Paan chewing showed a dose-dependent direct association with ICC (OR for >/=5 paan day(-1)=4.0; 95% CI 1.2-13.3). Among dietary habits, the highest vs lowest intake tertile for vegetables and fruit was associated with an OR of 0.5 (95% CI 0.2-1.0). Low education level and low body weight were also risk factors for ICC, but they did not account for the associations of paan chewing and low vegetable and fruit intake. In the analyses restricted to HPV-positive cases and controls, the inverse association with vegetable and fruit intake was confirmed. Conversely, the adverse influence of paan chewing on ICC risk seemed to be attributable to a higher prevalence of cervical HPV infection in women who chewed.
We report on the observation of superlattices that occur spontaneously in a nonlinear optical system with O(2) symmetry. A secondary bifurcation from hexagons yields patterns formed by twelve wave vectors. Besides irregular patterns these may either be quasiperiodic patterns or superlattices built from two classes of wave vectors differing slightly in their length. Both classes of wave vectors stem from only one pattern-forming instability. The wave vectors fit on a hexagonal or a square grid. In the former case the set of wave vectors can be decomposed into two hexagonal triads, whereas in the case of the square grid squeezed triads occur.
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BACKGROUND: The multiple injection technique for axillary block, in which the four distal nerves of the plexus are located by a nerve stimulator and separately injected, has been shown to provide a high success rate and a short onset time. This randomized double-blind study was conducted to compare the effectiveness of three different volumes of mepivacaine 10 mg x ml(-1) in patients undergoing elective distal upper limb surgery under axillary brachial plexus block with the four-nerve approach. The number of complete sensory blocks was the primary efficacy variable. METHODS: A total of 114 adult patients were randomly allocated to receive 36 (n=38), 28 (n=38), and 20 ml (n=38) of mepivacaine 10 mg x ml(-1). In each group, volumes were equally distributed in the four nerve territories. In all patients, performance time, latency time, block characteristics, need of supplementary blocks, tourniquet tolerance, duration of analgesia, and complications were recorded. RESULTS: Complete sensory block was obtained in 97% of patients receiving a volume of 36 ml, 97% of those receiving 28 ml, and 94% of those receiving 20 ml. One patient in the group of 28 ml and five patients in the group of 20 ml experienced pain on inflation of the tourniquet. Two months after surgery, no case of postoperative neurological dysfunction was observed. CONCLUSIONS: The three volumes (38, 28, and 20 ml) of mepivacaine 10 mg x ml(-1) ensured a similar and high percentage of complete sensory blocks in axillary brachial plexus anaesthesia with nerve stimulation involving the location of four motor responses.
The effect of smoking, drinking, diet, dental care and sexual habits on the risk of oral and pharyngeal cancer was investigated in a case-control study conducted in Warsaw, Poland. The study comprised 122 patients (including 44 females) aged 23-80 years with histologically confirmed cancer of oral cavity and pharynx. Controls were 124 subjects (including 52 females) admitted to the hospital for different non-neoplastic conditions unrelated to tobacco and alcohol consumption, with frequency matched to cases by age and sex. Smoking and drinking were strongly associated with an increased risk of oral cancer. Among consumers of both products, risks of oral cancer tended to combine in a multiplicative fashion and were increased more than 14-fold among those who consumed more than 15 cigarettes and seven or more drinks per day. Cessation of smoking was associated with reduced risk of this cancer. The risks varied by type of cigarettes smoked, being lower among those consuming filtered cigarettes only (OR = 1.6) than nonfilter (OR = 6.5) or mixed (OR = 4.2) cigarettes. High fruit intake was associated with significantly decreased risk (OR = 0.4) with the strongest significant inverse association found for fruit juices and citrus fruits ( < 0.01). After adjustment for tobacco smoking and alcohol drinking, poor dentition as evidenced by missing teeth, frequency of dental check-ups and frequency of teeth brushing emerged as a strong risk factor. Number of missing teeth and frequency of dental check-ups and frequency of tooth brushing showed increased ORs of 9.8, 11.9 and 3.2, respectively. Denture wearing did not affect oral cancer risk. No differences were detected in sexual practices (including oral sex and intercourse with prostitutes). In terms of attributable risk, smoking accounted for 57% of oral cancer cases in Poland, alcohol for 31% and low fruit intake for 12%. Attributable risks for low frequency of tooth brushing and dental check-ups were 56% and 47%, respectively. In conclusion, smoking and drinking cessation and increase of fresh fruit intake are likely to be effective preventive measures against oral cancer. These findings indicate also that poor oral hygiene may be an independent risk factor.