The Anisotropic Complex Dielectric Function of CsPbBr3 Perovskite Nanorods Obtained via an Iterative Matrix Inversion Method.

Colloidal lead halide perovskite nanorods have recently emerged as promising optoelectronic materials. However, more information about how shape anisotropy impacts their complex dielectric function is required to aid the development of applications that take advantage of the strongly polarized absorption and emission. Here, we have determined the anisotropy of the complex dielectric function of CsPbBr3 nanorods by analyzing the ensemble absorption spectra in conjunction with the ensemble spectral fluorescence anisotropy. This strategy allows us to distinguish the absorption of light parallel and perpendicular to the main axis so that the real and imaginary components of the dielectric function along each direction can be determined by the use of an iterative matrix inversion (IMI) methodology. We find that quantum confinement gives rise to unique axis-dependent electronic features in the dielectric function that increase the overall fluorescence anisotropy in addition to the optical anisotropy that results from particle shape, even in the absence of quantum confinement. Further, the procedure outlined here provides a strategy for obtaining anisotropic complex dielectric functions of colloidal materials of varying composition and aspect ratios using ensemble solution-phase spectroscopy.

Kinetic Control for Continuously Tunable Lattice Parameters, Size, and Composition during CsPbX3 (X = Cl, Br, I) Nanorod Synthesis.

The fast kinetics of all-inorganic CsPbX3 (X = Cl, Br, or I) nanocrystal growth entail that many synthetic strategies for structural control established in other semiconductor systems do not apply. Rather, products are often determined by thermodynamic factors, limiting the range of synthetic outcomes and functionality. In this study, we show how reaction kinetics are significantly slowed if nanocrystals are prepared using a dual injection strategy that moderates the crucial interaction between cesium and halide during nucleation and growth. The result is highly uniform nanorod or cuboid nanocrystals with a controllable size and aspect ratio across the quantum confinement regime, obtainable for both pure and mixed halide compositions. Further, the crystal lattice is continuously tunable between the tetragonal (I4/mcm) and orthorhombic (Pbnm) phases, independent of the overall nanorod morphology, enabling significantly more sophisticated structure-property relationships that can be tailored during this kinetically controlled synthesis.

Quantifying Order during Field-Driven Alignment of Colloidal Semiconductor Nanorods.

Aligning large populations of colloidal nanorods (NRs) into ordered assemblies provides a strategy for engineering macroscopic functional materials with strong optical anisotropy. The bulk optical properties of such systems depend not only on the individual NR building blocks but also on their meso- and macroscale ordering, in addition to more complex interparticle coupling effects. Here, we investigate the dynamic alignment of colloidal CdSe/CdS NRs in the presence of AC electric fields by measuring concurrent changes in optical transmission. Our work identifies two distinct scales of interaction that give rise to the field-driven optical response: (1) the spontaneous mesoscale self-assembly of colloidal NRs into structures with increased optical anisotropy and (2) the macroscopic ordering of NR assemblies along the direction of the applied AC field. By modeling the alignment of NR ensembles using directional statistics, we experimentally quantify the maximum degree of order in terms of the average deviation angle relative to the field axis. Results show a consistent improvement in alignment as a function of NR concentration─with a minimum average deviation of 36.2°â”€indicating that mesoscale assembly helps facilitate field-driven alignment of colloidal NRs.

The role of gold oxidation state in the synthesis of Au-CsPbX3 heterostructure or lead-free Cs2AuIAuIIIX6 perovskite nanoparticles.

Here, we report that the oxidation state of gold plays a dominant role in determining the reaction products when gold halide salts are mixed with all-inorganic lead halide perovskite nanocrystals. When CsPbX3 nanocrystals react with Au(i) halide salts, Au nanoparticles are deposited on the surface of the perovskites through the reduction of Au1+ ions by the surfactant ligand shell, to produce Au-CsPbX3 heterostructures. These heterostructures preserve comparably high photoluminescence quantum yield (PLQY) and show identical XRD diffractograms as the parent CsPbX3 nanocrystals. In contrast, the reaction of CsPbX3 nanocrystals with Au(iii) halide salts promotes complete cation exchange of Pb ions by Au ions in the nanocrystal perovskite lattice. The cation exchange products, Cs2AuIAuIIIBr6 or Cs2AuIAuIIICl6, show XRD patterns corresponding to a tetragonal mixed halide perovskite crystal structure and show no visible photoluminescence. This crucial dependence on the oxidation state of the Au ion informs synthetic strategies for producing and optimizing metal-perovskite heterostructures and lead-free perovskite nanoparticles.

Historical Migration revealed through a Case of Autosomal Dominant Alzheimer's Disease.

With the increasing geopolitical instability and environmental devastation occurring across the globe, human migration is increasing. We report a case that illustrates a migration pattern seen a century ago that is currently in the process of repeating itself. Using information from a neuropathological examination, genetic analyses, and historical sources, we linked a patient with autosomal dominant Alzheimer's disease in Hawai'i with her ancestors in Puerto Rico. In this patient we identified the G206A PSEN1 mutation, previously identified as being linked to a founder effect from Puerto Rico. At the turn of the twentieth century, due to devastating hurricanes in Puerto Rico and the island's new status as a possession of the United States, over 5,000 Puerto Ricans, including the grandparents of our patient, migrated to Hawai'i. This short-term but historic migration has resulted in a significant population of Puerto Ricans in Hawai'i, today. As physicians we sometimes have the opportunity and privilege, through the patients who come to us for help, to be indirect witnesses to such historical events and movements. These occurrences can inform the present and also portend future developments in this rapidly changing world.

[Microbial flora isolated from patient's conjunctiva previous to cataract surgery]. / Microbiota conjuntival en el preoperatorio de pacientes que se someterán a cirugía de cataratas.

BACKGROUND: Endophtalmitis post cataract surgery is one of most feared and devastating complications resulting in serious consequences and an uncertain visual prognosis. Antimicrobial prophylaxis against endophtalmitis must be based on the best knowledge of conjuntival microbiota. OBJECTIVE: To establish microbiological basis for the best antibiotic prophylaxis to prevent endophthalmitis in cataract surgery. MATERIALS AND METHODS: A descriptive, cross-sectional, prospective study. A preoperative conjunctival sample was taken from the lower fornix of 118 pacients, sowing it immediately in culture media. Identification of growing colonies and susceptibility testing were performed by manual or automated methods. RESULTS: 106 (89.8%) of 118 preoperative cultures were positive. 159 bacteria were isolated in single or mixed flora, with 95% of Gram positive organisms. Staphylococci represented 76.1% of isolated bacteria, with 82.6% of coagulase-negative staphylococci (SCN) and 17.4% of Staphylococcus aureus. Forty two percent of SCN and 38% of S. aureus were methicillin resistan; both groups showed high susceptibility to tobramycin and fourth-generation fluoroquinolones. CONCLUSIONS: we recommend the use of topical tobramycin as pre-operative antimicrobial prophylaxis associated with povidone-iodine antisepsis. A fourth-generation quinolone is recommended when there is risk of infection.

Use of the MoCA in Detecting Early Alzheimer's Disease in a Spanish-Speaking Population with Varied Levels of Education.

BACKGROUND/AIMS: Performance on the Montreal Cognitive Assessment (MoCA) has been demonstrated to be dependent on the educational level. The purpose of this study was to identify how to best adjust MoCA scores and to identify MoCA items most sensitive to cognitive decline in incipient Alzheimer's disease (AD) in a Spanish-speaking population with varied levels of education. METHODS: We analyzed data from 50 Spanish-speaking participants. We examined the pattern of diagnosis-adjusted MoCA residuals in relation to education and compared four alternative score adjustments using bootstrap sampling. Sensitivity and specificity analyses were performed for the raw and each adjusted score. The interval reliability of the MoCA as well as item discrimination and item validity were examined. RESULTS: We found that with progressive compensation added for those with lower education, unexplained residuals decreased and education-residual association moved to zero, suggesting that more compensation was necessary to better adjust MoCA scores in those with a lower educational level. Cube copying, sentence repetition, delayed recall, and orientation were most sensitive to cognitive impairment due to AD. CONCLUSION: A compensation of 3-4 points was needed for <6 years of education. Overall, the Spanish version of the MoCA maintained adequate psychometric properties in this population.

Microbiota conjuntival en el preoperatorio de pacientes que se someterán a cirugía de cataratas / Microbial flora isolated from patient's conjunctiva previous to cataract surgery

Background. Endophtalmitis post cataract surgery is one of most feared and devastating complications resulting in serious consequences and an uncertain visual prognosis. Antimicrobial prophylaxis against endophtalmitis must be based on the best knowledge of conjuntival microbiota. Objective: To establish microbiological basis for the best antibiotic prophylaxis to prevent endophthalmitis in cataract surgery. Materials and Methods: A descriptive, cross-sectional, prospective study. A preoperative conjunctival sample was taken from the lower fornix of 118 pacients, sowing it immediately in culture media. Identification of growing colonies and susceptibility testing were performed by manual or automated methods. Results: 106 (89.8%) of 118 preoperative cultures were positive. 159 bacteria were isolated in single or mixed flora, with 95% of Gram positive organisms. Staphylococci represented 76.1% of isolated bacteria, with 82.6% of coagulase-negative staphylococci (SCN) and 17.4% of Staphylococcus aureus. Forty two percent of SCN and 38% of S. aureus were methicillin resistan; both groups showed high susceptibility to tobramycin and fourth-generation fluoroquinolones. Conclusions: we recommend the use of topical tobramycin as pre-operative antimicrobial prophylaxis associated with povidone-iodine antisepsis. A fourth-generation quinolone is recommended when there is risk of infection.

Introducción: La endoftalmitis post-cirugía de cataratas es una de las complicaciones post-operatorias más temidas y devastadoras, pudiendo ocasionar secuelas graves, con un pronóstico visual incierto. La profilaxis antimicrobiana de esta complicación debe basarse en el conocimiento acabado de la microbiota presente en el territorio conjuntival. Objetivo: Establecer bases microbiológicas para una mejor profilaxis antimicrobiana de la endoftalmitis en cirugía de cataratas. Materiales y Métodos: Estudio descriptivo, de corte transversal, prospectivo. A 118 pacientes se les tomó muestra conjuntival pre-operatoria del fondo de saco inferior, sembrándola de inmediato en medios de cultivo. Las colonias desarrolladas se identificaron por métodos manuales y método de microdilución y difusión en disco. Resultados: De 118 cultivos pre-operatorios, 106 (89,8%) desarrollaron colonias bacterianas. Se aislaron 159 bacterias conjuntivales como especie única o cultivo mixta, siendo 95% grampositivas. El género Staphylococcus representó 76,1% del total de bacterias aisladas, siendo 82,6% Staphylococcus coagulasa negativa (SCN) y 17,4% Staphylococcus aureus. El 42% de los SCN y 38% de S. aureus presentaron resistencia a meticilina, presentando ambos buena susceptibilidad a tobramicina y fluoroquinolonas de cuarta generación. Conclusiones: Considerando nuestros resultados, recomendaríamos a nuestros pacientes tobramicina tópica como antibioprofilaxis, asociada a povidona yodada como antiséptico. Una quinolona de cuarta generación podría usarse cuando existan factores de riesgo de infección.

Younger age of dementia diagnosis in a Hispanic population in southern California.

OBJECTIVE: Prior studies of US Hispanics, largely performed on the East Coast, have found a younger age of dementia onset than in White non-Hispanics. We performed a cross-sectional study to examine clinical and sociodemographic variables associated with age of dementia diagnosis in older Hispanics and White, non-Hispanics in southern California. METHODS: Two hundred ninety (110 Hispanic and 180 White non-Hispanic) community dwelling, cognitively symptomatic subjects, aged 50 years and older, were assessed and diagnosed with probable Alzheimer's disease or probable vascular dementia. Apolipoprotein E (APOE) genotype was assessed in a subset of cases. Analysis of variance and multiple stepwise linear regression were used to assess main effects and interactions of ethnicity with dementia severity (indexed by mini mental state examination scores) and other sociodemographic and clinical variables on age of dementia diagnosis. RESULTS: Hispanics were younger by an average of 4 years at the time of diagnosis, regardless of dementia subtype, despite a similar prevalence of the APOE ε4 genotype. The earlier age at diagnosis for Hispanics was not explained by gender, dementia severity, years of education, history of hypercholesterolemia, hypertension, or diabetes. Only ethnicity was significantly associated with age of onset. CONCLUSIONS: These findings confirm that US Hispanics living in the southwestern USA tend to be younger at the time of dementia diagnosis than their White non-Hispanic counterparts. As this is not explained by the presence of the APOE ε4 genotype, further studies should explore other cultural, medical, or genetic risk factors influencing the age of dementia onset in this population.

Challenges to screening and evaluation of memory impairment among Hispanic elders in a primary care safety net facility.

OBJECTIVE: Implement a memory impairment screening procedure for elderly Hispanic primary care patients, and analyze its yield and challenges to further triage and diagnostic evaluation. METHODS: Three hundred twenty nine Hispanic patients aged ≥60 years or proxy informants were enrolled from outpatient primary care clinics at an urban safety-net medical center. Patients were screened for memory impairment using the WHO-UCLA AVLT; for those without consent capacity, proxies were given the IQCODE. Bilingual research assistants conducted in-person or telephone screening. Age, gender, education, comorbidities, acculturation, overall health, access to care, and memory concerns were assessed as potential predictors of memory impairment. Based on identified implementation challenges, a multi-disciplinary stakeholder committee proposed revised approaches to increase diagnostic evaluation and sustainability. RESULTS: Of 677 eligible patients approached, 329 (49%) were screened, and 77 (23%) met criteria for memory impairment using the WHO-UCLA AVLT (N=60) or the IQCODE (N=17). Only male gender and higher comorbidity uniquely predicted memory impairment (ps<0.05). Few screen-positive patients declined further triage and evaluation, but a substantial proportion could not be subsequently contacted. Challenges to implementing a memory screening program included staff time and adequate clinic space for in-person screening; challenges to follow-up of positive screening results included inability to contact patients and lack of primary care continuity to facilitate further triage and referral. CONCLUSIONS: Nearly one-fourth of primary care Hispanic elders screened as memory-impaired, but few factors predicted positive screening. Stakeholder-guided adaptations are needed-particularly in resource-constrained settings-to overcome challenges to further diagnostic evaluation and referral.

The Spanish translation and adaptation of the Uniform Data Set of the National Institute on Aging Alzheimer's Disease Centers.

Researchers from Alzheimer's Disease Centers (ADCs) across the United States with expertise in the assessment of Spanish-speaking elderly collaborated to create the official Spanish version of measures in the Uniform Data Set of the National Institute on Aging Alzheimer's Disease Center Program. The present article describes this project, whose primary goal was to create Spanish instruments with cultural and linguistic equivalence to the English versions. The resulting Spanish versions make provisions for variations among Spanish-speaking groups in the United States of different nationalities, socio-cultural, linguistic, and educational backgrounds. A consensus-based translation and adaptation approach was used, and guiding principles and specific components of this process are summarized. The Spanish translation and adaptation of the Uniform Data Set measures became available online to ADCs in April 2007. Its creation is important, as the resulting effort provides standardized measures for the collection of cross-sectional and longitudinal data on a large cohort of Spanish-speaking elders across the country and facilitates collaborative research among ADCs.

Análogos en el Régimen Basal/Bolo: Insulinización oportuna en diabetes tipo 2

La diabetes es una patología difícil de tratar. Actualmente la insulina sigue siendo el pilar fundamental, y las estrategias de tratamiento de reemplazo tienen por finalidad reproducir el perfil de secreción normal de insulina, para lograr así el control efectivo en los niveles de glucemia basal y postprandial. Con una combinación adecuada de análogos de insulina, se puede lograr ése control óptimo de la glucemia, recomendado por las diferentes asociaciones y organizaciones mundiales, dedicadas al estudio y control de la diabetes. En este artículo se realiza una revisión sobre la fisiopatología de la diabetes mellitus Tipo 1 y Tipo 2, como base para dirigir el tratamiento usando las nuevas insulinas (análogos), en cada una de ellas. Pero necesitamos superar los mitos y las barreras, que tienen los médicos y sus pacientes, a los regímenes de tratamiento con insulina.

Diabetes is a difficult disease to treat. Currently, insulin is still the mainstay. Treatment strategies are aimed to reproduce the normal secretory profile of insulin to achieve the effective control in the fasting and postprandial plasma glucose levels. Mostly, with an appropriate combination of insulin analogues, an optimal control of blood sugar could be achieved, such as recommended by the different worldwide associations and organizations, dedicated to the study and control care of diabetes. This article is a review of the pathophysiology of Type 1 and Type 2 diabetes mellitus as the support for treatment in each one of its, but we still need to dispel myth and removing barriers of acceptance about these insulin regimens treatments in physicians and patients.

Increased prevalence of significant recurrent headache in preclinical familial Alzheimer's disease mutation carriers.

BACKGROUND/AIMS: A previous study found a high prevalence of headaches in persons with familial Alzheimer's disease (FAD) due to a PSEN1 mutation. In our study we compared the prevalence of headaches between nondemented FAD mutation carriers (MCs) and non-mutation-carrying controls (NCs). METHODS: A headache questionnaire that assessed the prevalence of significant headaches and diagnosis of migraine and aura by ICHD-2 criteria was administered to 27 individuals at risk for FAD. Frequency of significant headaches, migraine, and aura were compared between MCs and NCs by chi(2) or Fisher's exact tests. RESULTS: Twenty-three subjects were at risk for PSEN1 mutations and 4 for an APP substitution. The majority of subjects were female (23/27). MCs were more likely to report significant recurrent headache than NCs (67 vs. 25%, p = 0.031). Forty percent of MCs had headaches that met criteria for migraine whereas 17% of NCs met such criteria. The tendency for a higher prevalence of headaches in MCs held for different PSEN1 and APP mutations but was not significant unless all families were combined. CONCLUSIONS: In this population, headache was more common in nondemented FAD MCs than NCs. Possible mechanisms for this include cerebral inflammation, aberrant processing of Notch3, or disrupted intracellular calcium regulation.

Diffusion tensor imaging in preclinical and presymptomatic carriers of familial Alzheimer's disease mutations.

Measures are needed that identify persons that will develop Alzheimer's disease in order to target them for preventative interventions. There is evidence from animal, pathological and imaging studies that disruption of white matter occurs in the course of Alzheimer's disease and may be an early event. Prior studies have suggested that late-myelinating regions or white matter connecting limbic structures are particularly susceptible to degradation. Persons destined to develop the disease by virtue of fully penetrant genetic alterations (familial Alzheimer's disease or FAD) provide a model in which early and even presymptomatic changes of the disease may be identified. In this study we performed diffusion tensor imaging (DTI) on 2 demented and 21 subjects at-risk for inheriting an FAD mutation. We compared global and localized fractional anisotropy (FA) measures in white matter between FAD mutation carriers and non-carriers in the preclinical (clinical dementia rating <1, n = 20) and presymptomatic (clinical dementia rating = 0, n = 15) stages of the disease. There were no significant differences between mutation carriers and non-carriers with regard to absolute age, age relative to the typical age of disease diagnosis in their family, gender or Mini-Mental Status Examination Score. Among preclinical FAD mutation carriers (n = 12), mean whole brain white-matter FA (P = 0.045), FA of the columns of the fornix (P = 0.012), area of the perforant pathways bilaterally (right side: P = 0.028, left side: P = 0.027) and left orbitofrontal lobe (P = 0.024) were decreased relative to that of non-carriers (n = 8). We also found that FA in the columns of the fornix (P = 0.008) and left orbitofrontal lobe white matter (P = 0.045) were decreased in the eight presymptomatic mutation carriers compared to seven non-carriers. Logistic regression demonstrated that FA of the columns of the fornix was a better predictor of mutation status than was cross-sectional area of the fornix, global mean white-matter FA and left frontal lobe white-matter FA. In a linear regression analysis, white-matter volume (P = 0.002), hippocampal volume (P = 0.023) and mutation status (P = 0.032) significantly predicted fornix FA. We conclude that FA is decreased in the white matter in preclinical and even presymptomatic FAD mutation carriers, particularly in the late-myelinating tracts connecting limbic structures. Decreased FA in of the columns of the fornix is particularly robust in early FAD and may provide a biomarker for early disease in sporadic Alzheimer's disease.

Neuropsychiatric and behavioral symptoms in a community sample of Hispanics with Alzheimer's disease.

The purpose of this study was to characterize and compare neuropsychiatric symptoms in a sample of 367 community-dwelling subjects: 70 Hispanics and 230 non-Hispanic white patients with Alzheimer's disease, and 22 Hispanics and 45 non-Hispanic white healthy age-matched controls. Neuropsychiatric symptoms were common among all patients with Alzheimer's disease. In the Alzheimer's disease groups, Hispanic subjects presented to the initial assessment with more symptoms than non-Hispanic white subjects did. In comparison to the non-Hispanic white population, the proportion of Hispanics with neuropsychiatric and behavioral symptoms was higher. These findings have implications for differential sociocultural presentations of Alzheimer's disease among ethnic/racial groups.

Mild cognitive impairment is associated with characteristic neuropsychiatric symptoms.

Mild cognitive impairment (MCI) has emerged as an identifiable condition and in many cases is a transitional state preceding diagnosable Alzheimer disease (AD). Neurobiological and neuroimaging characteristics of amnestic-type MCI have been investigated, but few comprehensive neuropsychiatric studies have been reported. The aim of this preliminary study was to define the neuropsychiatric features of the amnestic-type MCI and compare them with those of mild AD and normal controls. The Neuropsychiatric Inventory (NPI) was used to assess the neuropsychiatric symptoms in three age and education comparable groups, i.e., 28 MCI, 124 mild AD, and 50 normal subjects. Individual subscores of the 10 NPI symptoms and total NPI scores were compared between the MCI patients and the other 2 groups. The results of this preliminary investigation showed that MCI patients frequently manifested neuropsychiatric symptoms. The most common symptoms in the MCI group were dysphoria (39%), apathy (39%), irritability (29%), and anxiety (25%). There were significant differences in apathy, dysphoria, irritability, anxiety, agitation, and aberrant motor behavior between the MCI and control groups; in contrast, only delusions were significantly less common in MCI compared with mild AD. There was a significant difference between the MCI and control groups on total NPI scores (p = 0.001), but not between the MCI and mild AD groups (p = 0.304). Amnestic MCI is associated with significant neuropsychiatric symptoms, especially mood disturbances and apathy. Psychotic symptoms are significantly more common in the early stage of AD than in MCI. These results are derived from a limited clinical sample and require confirmation in longitudinal community-based investigations.