[Poor prognostic factors in patients hospitalized for COVID-19].

BACKGROUND: The clinical spectrum of COVID-19 varies from no or mild symptoms to pneumonia with fatal complications. The aim of the study was to find predictors of mortality and admission in the intensive care unit (ICU) in patients hospitalized for COVID-19. METHODS: Retrospective study of a cohort of patients admitted for COVID-19 between March 2020 and February 2021. Demographic, clinical, radiological and laboratory variables were described at admission. Independent predictors of mortality and ICU admission were identified by means of backward stepwise logistic regression and described in terms of odds ratio (OR) and 95% confidence interval (95%CI). RESULTS: A total of 883 patients were included, 51.8% men with a mean age of 68; 1.8% readmissions. 17.6% of patients died (n=154). The independent predictors of mortality were age (OR=1.071; 95%CI: 1.046-1.095), percentage of oxygen saturation (SatO2) (OR=0.938; 95%CI: 0.903-0.974), diastolic blood pressure (DBP, OR= 0.972; 95%CI: 0.955-0.989), creatinine (OR=1.516; 95%CI: 1.088-2.113), INR (OR=1.199; 95%CI: 1.012-1.419) and sodium (OR=1.082; 95%CI: 1.037-1.128). Eight percent of patients were admitted to ICU; the independent predictors were: male sex (OR=2.079; 95%CI: 1.099-3.935), age (OR=0.960; 95%CI: 0.942-0.979), SatO2 (OR=0.925; 95%CI: 0.889-0.962), creatinine (OR=1.551; 95%CI: 1.118-2.152) and C-reactive protein (CRP, OR=1.003; 95%CI: 1.000-1.007). CONCLUSION: The identification of independent predictors of mortality (age, SatO2, DBP, creatinine, INR, sodium) and ICU admission (sex, age, SatO2, creatinine, and CRP) allowed for the stratification of patients to adapt clinical care protocols to these findings, thereby improving medical decisions.

Factores de mal pronóstico en pacientes hospitalizados por COVID-19 / Poor prognostic factors in patients hospitalized for COVID-19

Fundamento: El espectro clínico de la COVID-19 varía entre sintomatología leve o ausente hasta neumonías con complicaciones mortales. El objetivo del estudio fue determinar los factores predictivos de mortalidad e ingreso en cuidados intensivos (UCI) en pacientes hospitalizados por COVID-19. Metodología: Estudio retrospectivo de una cohorte de pacientes ingresados por COVID-19 entre marzo de 2020 y febrero de 2021. Se describieron las variables demográficas, clínicas, radiológicas y analíticas al ingreso. Los predictores independientes de mortalidad e ingreso en UCI se identificaron mediante regresión logística por pasos hacia atrás y se describieron como odds ratio (OR) e intervalo de confianza al 95% (IC95%). Resultados: Se incluyeron 883 pacientes, 51,8% varones y edad media 68 años; el 1,8% reingresó. Fallecieron 154 pacientes (17,6%); los predictores independientes de mortalidad fueron: edad (OR=1,071; IC95%: 1,046-1,095), porcentaje de saturación de oxígeno (SatO2) (OR=0,938; IC95%: 0,903-0,974), tensión arterial diastólica (PAD, OR=0,972; IC95%: 0,955-0,989), creatinina (OR=1,516; IC95%: 1,088-2,113), INR (OR=1,199; IC95%: 1,012-1,419) y sodio (OR=1,082; IC95%: 1,037-1,128). El 8% de los pacientes ingresaron en UCI; las variables predictoras independientes fueron: sexo masculino (OR=2,079; IC95%: 1,099-3,935), edad (OR=0,960; IC95%: 0,942-0,979), SatO2 (OR=0,925; IC95%: 0,889-0,962), creatinina (OR=1,551; IC95%: 1,118-2,152) y proteína C reactiva (PCR, OR=1,003; IC95%: 1,000-1,007). Conclusiones: La identificación de predictores independientes de mortalidad (edad, SatO2, PAD, creatinina, INR, sodio) y de ingreso en UCI (sexo, edad, SatO2, creatinina y PCR) permite estratificar a los pacientes y adaptar los protocolos de atención clínica a estos hallazgos, mejorando las decisiones médicas.(AU)

Background: The clinical spectrum of COVID-19 varies from no or mild symptoms to pneumonia with fatal complications. The aim of the study was to find predictors of mortality and admis-sion in the intensive care unit (ICU) in patients hospitalized for COVID-19. Methods: Retrospective study of a cohort of patients admitted for COVID-19 between March 2020 and February 2021. Demographic, clinical, radiological and laboratory variables were described at admission. Independent predictors of mortality and ICU admission were identified by means of backward stepwise logistic regression and described in terms of odds ratio (OR) and 95% confidence interval (95%CI). Results: A total of 883 patients were included, 51.8% men with a mean age of 68; 1.8% readmissions. 17.6% of patients died (n=154). The independent predictors of mortality were age (OR=1.071; 95%CI: 1.046-1.095), percentage of oxygen saturation (SatO2) (OR=0.938; 95%CI: 0.903-0.974), diastolic blood pressure (DBP, OR= 0.972; 95%CI: 0.955-0.989), creatinine (OR=1.516; 95%CI: 1.088-2.113), INR (OR=1.199; 95%CI: 1.012-1.419) and sodium (OR=1.082; 95%CI: 1.037-1.128). Eight percent of patients were admitted to ICU; the independent predictors were: male sex (OR=2.079; 95%CI: 1.099-3.935), age (OR=0.960; 95%CI: 0.942-0.979), SatO2 (OR=0.925; 95%CI: 0.889-0.962), creatinine (OR=1.551; 95%CI: 1.118-2.152) and C-reactiveprotein (CRP, OR=1.003; 95%CI: 1.000-1.007). Conclusion: The identification of independent predictors of mortality (age, SatO2, DBP, creatinine, INR, sodium) and ICU admission (sex, age, SatO2, creatinine, and CRP) allowed for the stratification of patients to adapt clinical care protocols to these findings, thereby improving medical decisions.(AU)

Altered Expression of ORAI and STIM Isoforms in Activated Human Cardiac Fibroblasts.

Cardiac fibrotization is a well-known process characteristic of many cardiac pathological conditions. The key element is excessive activation of cardiac fibroblasts, their transdifferentiation into myofibroblasts, increased production, and accumulation of extracellular matrix proteins, resulting in cardiac stiffness. The exact cellular mechanisms and molecular components involved in the process are not fully elucidated, but the SOCE mechanism could play an important role. Its key molecules are the molecular sensor of calcium in ER/SR - STIM and the highly selective calcium channels Orai located in the plasma membrane. This study aims to evaluate selected SOCE-associated genes in the activation of HCF cell culture by several known substances (phenylephrine, isoprenaline) that represent cardiovascular overload. After cell cultivation, cell medium was collected to measure the soluble collagen content. From the harvested cells, qRT-PCR was performed to determine the mRNA levels of the corresponding genes. The activation of cells was based on changes in the relative expression of collagen genes as well as the collagen content in the medium of the cell culture. We detected an increase in the expression of the Orai2 isoform, a change in the Orai1/Orai3 ratio and also an increase in the expression of the STIM2 isoform. These results suggest an increased activation of the SOCE mechanism under stress conditions of fibroblasts, which supports the hypothesis of fibroblast activation in pathological processes by altering calcium homeostasis through the SOCE mechanism.

Altered Expression of ORAI and STIM Isoforms in Activated Human Cardiac Fibroblasts.

Cardiac fibrotization is a well-known process characteristic of many cardiac pathological conditions. The key element is excessive activation of cardiac fibroblasts, their transdifferentiation into myofibroblasts, increased production, and accumulation of extracellular matrix proteins, resulting in cardiac stiffness. The exact cellular mechanisms and molecular components involved in the process are not fully elucidated, but the SOCE mechanism could play an important role. Its key molecules are the molecular sensor of calcium in ER/SR - STIM and the highly selective calcium channels Orai located in the plasma membrane. This study aims to evaluate selected SOCE-associated genes in the activation of HCF cell culture by several known substances (phenylephrine, isoprenaline) that represent cardiovascular overload. After cell cultivation, cell medium was collected to measure the soluble collagen content. From the harvested cells, qRT-PCR was performed to determine the mRNA levels of the corresponding genes. The activation of cells was based on changes in the relative expression of collagen genes as well as the collagen content in the medium of the cell culture. We detected an increase in the expression of the Orai2 isoform, a change in the Orai1/Orai3 ratio and also an increase in the expression of the STIM2 isoform. These results suggest an increased activation of the SOCE mechanism under stress conditions of fibroblasts, which supports the hypothesis of fibroblast activation in pathological processes by altering calcium homeostasis through the SOCE mechanism.

Individual and structural barriers to Latin American refugees and asylum seekers' access to primary and mental healthcare in Chile: A qualitative study.

BACKGROUND: Since 2010 there has been a growing population of refugees and asylum seekers in Latin America. This study sought to investigate the perceived experiences and healthcare needs of refugees and asylum seekers of Latin American origin in Chile in order to identify main barriers to healthcare and provide guidance on allied challenges for the public healthcare system. METHODS: Descriptive qualitative case study with semi-structured interviews applied to refugees and asylum seekers (n = 8), healthcare workers (n = 4), and members of Non-Governmental Organizations and religious foundations focused on working with refugees and asylum seekers in Chile (n = 2). RESULTS: Although Chilean law guarantees access to all levels of healthcare for the international migrant population, the specific healthcare needs of refugees and asylum seekers were not adequately covered. Primary care and mental healthcare were the most required types of service for participants, yet they appeared to be the most difficult to access. Difficulties in social integration -including access to healthcare, housing, and education- upon arrival and lengthy waiting times for legal status of refugees also presented great barriers to effective healthcare provision and wellbeing. Healthcare workers and members of organizations indicated the need for more information about refugee and asylum-seeking populations, their rights and conditions, as well as more effective and tailored healthcare interventions for them, especially for emergency mental healthcare situations. CONCLUSIONS: All participants perceived that there was disinformation among institutional actors regarding the healthcare needs of refugees and asylum seekers in Chile. They also perceived that there were barriers to access to primary care and mental healthcare, which might lead to overuse of emergency services. This study highlights a sense of urgency to protect the social and healthcare needs of refugees and asylum seekers in Latin America.

Changes in STIM isoforms expression and gender-specific alterations in Orai expression in human heart failure.

Store-operated calcium entry (SOCE) is one of regulatory mechanisms which regulates Ca2+ cycling in the heart. SOCE alterations in pathological conditions contribute to progression of heart failure and cardiac hypertrophy by multiple signaling pathways such as Cn/NFAT and CaMKII/MEF2. Several components mediating SOCE have been identified, such as STIM and Orai. Different isoforms of both Orai and STIM have been detected in animal studies, exhibiting distinct functional properties. This study is focused on the analysis of STIM and Orai isoforms expression in the end-stage human failing myocardium. Left ventricle samples isolated from 43 explanted hearts from patients undergoing heart transplant and from 5 healthy donor hearts were used to determine the mRNA levels of Orai1, Orai2 and Orai3, STIM1, STIM2 and STIM2.1 by qRT-PCR. The expression was further analyzed for connection with gender, related co-morbidities, pathoetiology, clinical data and biochemical parameters. We show that Orai1 expression is decreased by 30 % in failing myocardium, even though we detected no significant changes in expression of Orai2 or Orai3. Interestingly, this decrease in Orai1 was gender-specific and was present only in men, with no change in women. The ratio Orai1/Orai3 was significantly lower in males as well. The novel STIM2.1 isoform was detected both in healthy and failing human myocardium. In the end-stage heart failure, the expression of STIM2.1 was significantly decreased. The lower ratio of STIM2.1/STIM2 in failing hearts indicates a switch from SOCE-inhibiting STIM2.1 isoform to stimulatory STIM2.2. STIM1 mRNA levels were not significantly changed. These observed alterations in Orai and STIM expression were independent of functional heart parameters, clinical or biochemical patient characteristics. These results provide detailed insight into the alterations of SOCE regulation in human failing myocardium. Gender-specific change in Orai1 expression might represent a possible mechanism of cardioprotective effects of estrogens. The switch from STIM2.1 to STIM2.2 indicates an amplification of SOCE and could contribute to the hypertrophy development in the filing heart.

The Solar Spectrum in the Atacama Desert.

The Atacama Desert has been pointed out as one of the places on earth where the highest surface irradiance may occur. This area is characterized by its high altitude, prevalent cloudless conditions and relatively low columns of ozone and water vapor. Aimed at the characterization of the solar spectrum in the Atacama Desert, we carried out in February-March 2015 ground-based measurements of the spectral irradiance (from the ultraviolet to the near infrared) at seven locations that ranged from the city of Antofagasta (on the southern pacific coastline) to the Chajnantor Plateau (5,100 m altitude). Our spectral measurements allowed us to retrieve the total ozone column, the precipitable water, and the aerosol properties at each location. We found that changes in these parameters, as well as the shorter optical path length at high-altitude locations, lead to significant increases in the surface irradiance with the altitude. Our measurements show that, in the range 0-5100 m altitude, surface irradiance increases with the altitude by about 27% in the infrared range, 6% in the visible range, and 20% in the ultraviolet range. Spectral measurements carried out at the Izaña Observatory (Tenerife, Spain), in Hannover (Germany) and in Santiago (Chile), were used for further comparisons.

[Higher risk for health care associated infections in hospitalized children with special health needs]. / Mayor riesgo de infecciones asociadas a atención en salud en niños con necesidades especiales hospitalizados.

BACKGROUND: Nosocomial infections (NIs) represent an important public health issue, being associated with high morbidity, mortality and costs. OBJECTIVES: To identify risk factors of NIs in a cohort of hospitalized pediatric patients, with emphasis in children with special health care needs (CSHCN). PATIENTS AND METHODS: We studied patients hospitalized in Sótero del Río Pediatric Hospital at Santiago-Chile, between September and December, 2009. Relative Risk (RR) was calculated between CSHCN-3 (children attended by three or more health care professionals) versus non CSHCN-3, and between children with medical complexity (CMC) versus non CMC, using log-binomial models. RESULTS: 920 patients were included. Prevalence of NIs was 12.7%. The most frequent diagnoses were gastrointestinal and respiratory viral infections. Both crude and adjusted by confounders (age and sex), CSHCN-3 and CMC presented significantly higher risk of NIs compared to patients without these conditions (RR 2.91 and RR 2.16, respectively). CONCLUSION: CSHCN-3 and CMC represent independent conditions associated to a 2-3 fold risk of NIs.

Mayor riesgo de infecciones asociadas a atención en salud en niños con necesidades especiales hospitalizados / Higher risk for health care associated infections in hospitalized children with special health needs

Background: Nosocomial infections (NIs) represent an important public health issue, being associated with high morbidity, mortality and costs. Objectives: To identify risk factors of NIs in a cohort of hospitalized pediatric patients, with emphasis in children with special health care needs (CSHCN). Patients and Methods: We studied patients hospitalized in Sótero del Río Pediatric Hospital at Santiago-Chile, between September and December, 2009. Relative Risk (RR) was calculated between CSHCN-3 (children attended by three or more health care professionals) versus non CSHCN-3, and between children with medical complexity (CMC) versus non CMC, using log-binomial models. Results: 920 patients were included. Prevalence of NIs was 12.7%. The most frequent diagnoses were gastrointestinal and respiratory viral infections. Both crude and adjusted by confounders (age and sex), CSHCN-3 and CMC presented significantly higher risk of NIs compared to patients without these conditions (RR 2.91 and RR 2.16, respectively). Conclusion: CSHCN-3 and CMC represent independent conditions associated to a 2-3 fold risk of NIs.

Introducción: Las infecciones asociadas a atención en salud (IAAS) representan un problema frecuente, el cual se asocia a una mayor morbimortalidad y costos. Objetivos: Evaluar factores de riesgo de IAAS en una cohorte de niños hospitalizados, con énfasis en el grupo de niños y adolescentes con necesidades especiales de atención en salud (NANEAS). Materiales y Métodos: Estudio realizado en el Hospital Sótero del Río, Santiago-Chile, entre septiembre y diciembre de 2009. Se calculó riesgo relativo (RR) de IAAS entre pacientes NANEAS-3 (niños controlados por tres o más profesionales de la salud) versus no NANEAS-3, y entre niños con complejidad médica (NCM) versus no NCM, a través de modelos log-binomial. Resultados: Se obtuvo información de 920 pacientes. Un 12,7% presentó IAAS; las más frecuentes fueron infecciones virales gastrointestinales y respiratorias. Tanto en forma cruda como ajustada por variables confundentes (edad y sexo), los pacientes NANEAS-3 y NCM presentaron significativamente mayor riesgo de IAAS versus aquellos que no cumplían estas definiciones (RR 2,91 y RR 2,16, respectivamente). Conclusiones: Los pacientes NANEAS-3 y NCM representan condiciones independientes asociadas a un riesgo dos a tres veces mayor de IAAS.

Validation of the vascular pedicle width as a diagnostic aid in critically ill patients with pulmonary oedema by novice non-radiology physicians-in-training.

Assessing intravascular volume status in the critically ill patient remains a challenge for intensivists, and the accuracy of such estimation based on bedside examination alone is reported to be nearly a coin toss. In this retrospective study we sought to validate a previously recommended chest radiographic vascular pedicle width (VPW) ≥70 mm for identifying cardiogenic pulmonary oedema (CPO). We additionally assessed whether novice physicians-in-training can reliably measure the VPW. The study included intensive care patients with an existing pulmonary artery catheter. Three independent raters performed measurements of VPW from chest radiographs obtained within three hours of pulmonary artery occlusion pressure measurements. In 80 patients enrolled, a VPW cut-off of ≥70 mm had a 55% sensitivity, 88% specificity, 81% positive predictive value, 69% negative predictive value and 73% accuracy for identifying patients with CPO. Receiver operating characteristic curve analysis showed an area under the curve of 0.72 (95% confidence interval 0.61 to 0.84) for VPW in discriminating CPO from non-cardiogenic pulmonary oedema. Kappa statistics for inter-rater reliability showed Kappa=0.41, 0.42 and 0.85 for each pair of the three raters. In conclusion, the previously accepted VPW cut-off of ≥70 mm is reasonably accurate in discriminating CPO from non-cardiogenic pulmonary oedema. VPW can be measured by physicians-in-training with a comparable performance to previous studies utilising expert radiologists.

Pleiotropic effects of simvastatin are associated with mitigation of apoptotic component of cell death upon lethal myocardial reperfusion-induced injury.

Although statins exert non-lipid cardioprotective effects, their influence on cell death is not fully elucidated. For this purpose, we investigated whether simvastatin treatment (S, 10 mg/kg, 5 days) is capable of mitigating ischemia/reperfusion-induced (IR) apoptosis in the isolated rat hearts, which was examined using immunoblotting analysis. In addition, the content of signal transducer and activator of transcription 3 (STAT3) and its active form, phosphorylated STAT3 (pSTAT3-Thr(705)), was analyzed. Simvastatin induced neither variations in the plasma lipid levels nor alterations in the baseline content of analysed proteins with the exception of upregulation of cytochrome C. Furthermore, simvastatin significantly increased the baseline levels of pSTAT3 in contrast to the control group. In the IR hearts, simvastatin reduced the expression of Bax and non-cleaved caspase-3. In these hearts, phosphorylation of STAT3 did not differ in comparison to the non-treated IR group, however total STAT3 content was slightly increased. The improved recovery of left ventricular developed pressure co-existed with the increased Bcl-2/Bax ratio. In conclusion, pleiotropic action of statins may ameliorate viability of cardiomyocytes by favouring the expression of anti-apoptotic Bcl-2 and downregulating the pro-apoptotic markers; however STAT3 does not seem to be a dominant regulator of this anti-apoptotic action of simvastatin.

Environmental pediatrics: an emerging issue.

OBJECTIVE: To review the most relevant articles regarding environmental pediatrics, its potential effects on health, and especially its advances in prevention. SOURCES: A literature search was conducted using MEDLINE/PubMed and SciELO databases. Articles from 1990 to 2010 were reviewed, in addition to book chapters related to environmental pediatrics. SUMMARY OF THE FINDINGS: There is a significant variety of factors that make children highly vulnerable to environmental hazard exposure, which are mainly associated with children's comparatively greater consumption of water, food, and air in relation to body weight. According to the World Health Organization, every year more than 3 million children under the age of 5 die because of environment-related conditions. Approximately 30 to 40% of pediatric diseases are related to environmental factors. Children are constantly exposed to various environmental health hazards, among which the following stand out: contaminated water, lack of adequate sanitation facilities, air pollution, disease vectors, chemical hazards, injuries, and accidents. CONCLUSIONS: Nowadays, pediatricians are challenged to address environmental pediatrics health care needs. The pediatric health history needs to be more comprehensive by adding pointed questions to help identify potential environmental risks. Awareness and understanding of the noxious effects of various environmental conditions and knowledge of the related prevention measures will result in timely and adequate interventions that will improve our children's health and development.

Pediatria ambiental: um tema emergente / Environmental pediatrics: an emerging issue

OBJETIVO: Revisar os artigos mais relevantes sobre a pediatria ambiental, seus efeitos potenciais para a saúde e, especialmente, seus avanços na prevenção. FONTES DOS DADOS: Foi realizada uma pesquisa utilizando as bases de dados MEDLINE/PubMed e SciELO. Foram revisados artigos de 1990 a 2010, além de capítulos de livros relacionados à pediatria ambiental. SÍNTESE DOS DADOS: Há uma variedade significativa de fatores que tornam as crianças altamente vulneráveis à exposição a riscos ambientais, associados principalmente ao consumo comparativamente maior de água, comida e ar por parte da criança, em relação ao seu peso corporal. De acordo com a Organização Mundial de Saúde, mais de 3 milhões de crianças menores de 5 anos morrem devido a doenças relacionadas ao meio ambiente. Aproximadamente 30-40 por cento das doenças pediátricas estão relacionadas a fatores ambientais. As crianças estão constantemente expostas a vários riscos ambientais para a saúde, dentre os quais se destacam: água contaminada, falta de condições adequadas de saneamento, poluição do ar, vetores de doenças, perigos químicos, injúrias e acidentes. CONCLUSÕES: Atualmente, os pediatras são desafiados a tratar das necessidades de saúde ligadas à pediatria ambiental. A história pediátrica deve ser mais abrangente, acrescentando-se questões pontuais que ajudem a identificar potenciais riscos ambientais. A conscientização e o entendimento sobre os efeitos nocivos das várias condições ambientais e o conhecimento sobre as medidas de prevenção relacionadas resultarão em intervenções oportunas e adequadas que melhorarão a saúde e o desenvolvimento das nossas crianças.

OBJECTIVE: To review the most relevant articles regarding environmental pediatrics, its potential effects on health, and especially its advances in prevention. SOURCES: A literature search was conducted using MEDLINE/PubMed and SciELO databases. Articles from 1990 to 2010 were reviewed, in addition to book chapters related to environmental pediatrics. SUMMARY OF THE FINDINGS: There is a significant variety of factors that make children highly vulnerable to environmental hazard exposure, which are mainly associated with children’s comparatively greater consumption of water, food, and air in relation to body weight. According to the World Health Organization, every year more than 3 million children under the age of 5 die because of environment-related conditions. Approximately 30 to 40 percent of pediatric diseases are related to environmental factors. Children are constantly exposed to various environmental health hazards, among which the following stand out: contaminated water, lack of adequate sanitation facilities, air pollution, disease vectors, chemical hazards, injuries, and accidents. CONCLUSIONS: Nowadays, pediatricians are challenged to address environmental pediatrics health care needs. The pediatric health history needs to be more comprehensive by adding pointed questions to help identify potential environmental risks. Awareness and understanding of the noxious effects of various environmental conditions and knowledge of the related prevention measures will result in timely and adequate interventions that will improve our children’s health and development.

Relevance of symmetry for the synchronization of chaotic optical systems and the related Lang-Kobayashi model limitations.

Synchronization of chaotic semiconductor lasers has now been demonstrated experimentally in a variety of coupling schemes. Coupling methods include configurations where the transmitter laser system is itself chaotic and drives a receiver system, both lasers are individually chaotic, and both lasers induce the chaos through mutual coupling. The dynamics for each of these scenarios is in many cases adequately captured by the Lang-Kobayashi rate equation model. Such a simplified model, however, ignores fundamental aspects of the laser dynamics, such as the frequency and carrier density material susceptibility dependence, spatial hole burning effects, proper boundary conditions, and the fact that lasers may exhibit pronounced multilongitudinal dynamic behavior with and without the presence of a weak external feedback or injection. The model also cannot distinguish between many of the possible coupling geometries realizable in experiments. Using an interactive simulator based on the rigorous microscopic description of the light-matter interaction, we explore the unidirectionally coupled configuration, the relevance of symmetry for the synchronization achieved between two identical lasers, and the differences that arise when the traditional analysis through the Lang-Kobayashi model is compared to the full nonlinear partial differential equation model results.

Achronal generalized synchronization in mutually coupled semiconductor lasers.

Heil et al. [Phys. Rev. Lett. 86, 795 (2001)] recently discovered achronal synchronization of chaos in mutually coupled semiconductor lasers. This paper offers an analytic interpretation of their experiment using a simple rate equation model. Local eigenvalue analysis shows that isochronal synchronization is unstable; achronal synchronization, on the other hand, is stable if a generalized synchronization function is introduced. Single- and multimode simulations have substantiated this rate equation interpretation. Finally, there is a brief examination of "chaos pass filtering."

Molecular similarity for small species: refining the isoelectronic index.

This paper tests a chemical-similarity model against properties of gas-phase neutral triatomic and four-atom molecules. The model is a variant of the Diatomics-in-Molecules (DIM) picture, which considers a molecule to be the superposition of all diatomic molecules that could be formed from adjacent atoms in the molecule. The variant is that adjacent atoms are counted as a diatomic molecule only if they are bonded. The tests consist of investigating whether molecules with the same number of electrons, computed by the adjacent-DIM model, have data more similar than do molecules selected at random. The tests vindicate the model for the heat of atomization and for the equilibrium constant for formation, they agree with the model with lesser confidence for the entropy and the partition function, and they show that the model fails for the ionization potential. The model applies with most confidence to molecules with the more electronegative atoms from rows 2 or 3 (those of greatest interest in organic chemistry) and with lesser confidence otherwise. For these properties and these molecules, the model passes graphical and statistical tests at least as well as does the traditional isoelectronic model. Thus, this work refines what may be called the isoelectronic index.

Determinación de bifenilos policlorados (PCBs) en muestras de leche humana recolectadas en tres provincias de la décima región, Chile: 1990 / Polychlorinated biphenils (PCBs) determination in human milk samples collected in 3 provinces of tenth region of Chile: 1990

PCBs were detected using gas liquid chromatography in 540 human milk samples coming from 180 mothers living in three provinces of the Southern Region of Chile, collected in three different stages of lactation. Samples coming from 33 women (18.3 per cent) had PCBs residues, with a median level of 1.28 (range 0,09-84.83) ppm (milk fat basis). Ten of these women delivered to their offspring more than 0.01 mg of PCB/kg body weight/day, level considered hazardous to child helath. PCB levels tended to increase toward the third sampling stage. These levels were not related to women`s age but primiparae had higher levels than multiparae. It is concluded that a surveillance system in biological samples is necessary to oversee PCB levels in different regions of the country