Solar cells sensitized with natural dyes: an introductory experiment about solar energy for undergraduate students

An interesting practical experiment about the preparation of dye–sensitized solar cells (DSSC) using natural dyes were carried out by the undergraduate students in the chemistry course at UNICAMP . Natural dyes were extracted from blueberries (Vaccinium myrtillus L.), jabuticabas (Myrciaria cauliflora), raw and cooked beets (Beta vulgarisL.), and annattos (Bixa orellana L.), which were used to sensitize TiO2 films that composed the photoanode in the DSSC. A polymer electrolyte containing an iodide/triiodide redox couple was used in lieu of the use of liquid solutions to prevent any leakage in the devices. A maximum solar-to-electric energy conversion of 0.26 ± 0.02% was obtained for the solar cell prepared with annatto extracts. This experiment was an effective way to illustrate to the undergraduate students how to apply some of the chemical concepts that they learned during their chemistry course to produce electric energy from a clean and renewable energy source. Teachers could also exploit the basics of the electronic transitions in inorganic and organic compounds (e.g., metal-to-ligand charge transfer and ϖ-ϖ* transitions), thermodynamics (e.g., Gibbs free energy), acid–base reactions in the oxide solid surface and electrolyte, and band theory (i.e., the importance of the Fermi level energy).An interesting practical experiment about the preparation of dye–sensitized solar cells (DSSC) using natural dyes were carried out by the undergraduate students in the chemistry course at UNICAMP . Natural dyes were extracted from blueberries (Vaccinium myrtillus L.), jabuticabas (Myrciaria cauliflora), raw and cooked beets (Beta vulgarisL.), and annattos (Bixa orellana L.), which were used to sensitize TiO2 films that composed the photoanode in the DSSC. A polymer electrolyte containing an iodide/triiodide redox couple was used in lieu of the use of liquid solutions to prevent any leakage in the devices. A maximum solar-to-electric energy conversion of 0.26 ± 0.02% was obtained for the solar cell prepared with annatto extracts. This experiment was an effective way to illustrate to the undergraduate students how to apply some of the chemical concepts that they learned during their chemistry course to produce electric energy from a clean and renewable energy source. Teachers could also exploit the basics of the electronic transitions in inorganic and organic compounds (e.g., metal-to-ligand charge transfer and ϖ-ϖ* transitions), thermodynamics (e.g., Gibbs free energy), acid–base reactions in the oxide solid surface and electrolyte, and band theory (i.e., the importance of the Fermi level energy).v. 38n.101357136

Effective theories of single field inflation when heavy fields matter

We compute the low energy effective field theory (EFT) expansion for single-field inflationary models that descend from a parent theory containing multiple other scalar fields. By assuming that all other degrees of freedom in the parent theory are sufficiently massive relative to the inflaton, it is possible to derive an EFT valid to arbitrary order in perturbations, provided certain generalized adiabaticity conditions are respected. These conditions permit a consistent low energy EFT description even when the inflaton deviates off its adiabatic minimum along its slowly rolling trajectory. By generalizing the formalism that identifies the adiabatic mode with the Goldstone boson of this spontaneously broken time translational symmetry prior to the integration of the heavy fields, we show that this invariance of the parent theory dictates the entire non-perturbative structure of the descendent EFT. The couplings of this theory can be written entirely in terms of the reduced speed of sound of adiabatic perturbations. The resulting operator expansion is distinguishable from that of other scenarios, such as standard single inflation or DBI inflation. In particular, we re-derive how certain operators can become transiently strongly coupled along the inflaton trajectory, consistent with slow-roll and the validity of the EFT expansion, imprinting features in the primordial power spectrum, and we deduce the relevant cubic operators that imply distinct signatures in the primordial bispectrum which may soon be constrained by observations.Comment: (v1) 25 pages, 1 figure; (v2) references added and typos corrected, to appear in Journal of High Energy Physic

Acculturation Is Associated With Hypertension in a Multiethnic Sample

Background: Hypertension varies in prevalence among race/ethnic groups in the United States. Within-ethnic group differences associated with acculturation have been less frequently examined. We studied the association of three measures of acculturation (language spoken at home, place of birth, and years living in the US) with hypertension in a population sample of 2619 white, 1898 African American, 1,494 Hispanic, and 803 Chinese participants in the Multiethnic Study of Atherosclerosis. Methods: Multivariate Poisson regression was used to estimate the association between the acculturation variables and hypertension. Results: Birthplace outside the US and speaking a non-English language at home were each associated with a lower prevalence of hypertension after adjustment for age, gender, and socioeconomic status (prevalence ratio [95% confidence intervals] 0.82 (0.77–0.87) for non-US born versus US born and 0.80 (0.74–0.85) for those not speaking English at home versus speakers of English at home, both P < .001). For participants born outside of the US, each 10-year increment of years in the US was associated with a higher prevalence of hypertension after adjustment for age, gender, and socioeconomic status (P for trend < .01). The associations between acculturation variables and hypertension were weakened after adjustment for race/ethnic category and risk factors for hypertension. Compared to US-born Hispanics, those born in Mexico or South America had lower prevalence of hypertension, but those born in the Caribbean and Central America had higher prevalence of hypertension. Conclusions: Acculturation and place of birth are associated with hypertension in a multiethnic sample.http://deepblue.lib.umich.edu/bitstream/2027.42/57776/1/Acculturation is associated with hypertension in a multiethnic sample.pd

A Distinct Gene Module for Dysfunction Uncoupled from Activation in Tumor-Infiltrating T Cells

Reversing the dysfunctional T cell state that arises in cancer and chronic viral infections is the focus of therapeutic interventions; however, current therapies are effective in only some patients and some tumor types. To gain a deeper molecular understanding of the dysfunctional T cell state, we analyzed population and single-cell RNA profiles of CD8+tumor-infiltrating lymphocytes (TILs) and used genetic perturbations to identify a distinct gene module for T cell dysfunction that can be uncoupled from T cell activation. This distinct dysfunction module is downstream of intracellular metallothioneins that regulate zinc metabolism and can be identified at single-cell resolution. We further identify Gata-3, a zinc-finger transcription factor in the dysfunctional module, as a regulator of dysfunction, and we use CRISPR-Cas9 genome editing to show that it drives a dysfunctional phenotype in CD8+TILs. Our results open novel avenues for targeting dysfunctional T cell states while leaving activation programs intact

Hemozoin produced by mammals confers heme tolerance

Free heme is cytotoxic as exemplified by hemolytic diseases and genetic deficiencies in heme recycling and detoxifying pathways. Thus, intracellular accumulation of heme has not been observed in mammalian cells to date. Here we show that mice deficient for the heme transporter SLC48A1 (also known as HRG1) accumulate over ten-fold excess heme in reticuloendothelial macrophage lysosomes that are 10 to 100 times larger than normal. Macrophages tolerate these high concentrations of heme by crystallizing them into hemozoin, which heretofore has only been found in blood-feeding organisms. SLC48A1 deficiency results in impaired erythroid maturation and an inability to systemically respond to iron deficiency. Complete heme tolerance requires a fully-operational heme degradation pathway as haplo insufficiency of HMOX1 combined with SLC48A1 inactivation causes perinatal lethality demonstrating synthetic lethal interactions between heme transport and degradation. Our studies establish the formation of hemozoin by mammals as a previously unsuspected heme tolerance pathway

New Multicomponent Forms of the Antiretroviral Nevirapine with Improved Dissolution Performance

In the pharmaceutical area, some drugs exhibit physicochemical properties that adversely affect the formulation processes for bioavailability and effectiveness. Nevirapine (NVP) is an antiretroviral drug that presents low aqueous solubility, which directly impacts its bioavailability. Among all possible modifications, multicomponent crystals, such as cocrystals and eutectic compositions, have been successfully used to improve the solubility of drugs. In this work, the propensity of the formation of multicomponent systems of NVP with seven possible coformers were predicted and tested: salicylic acid (SA), 3-hydroxybenzoic acid (3HBZC), 4-hydroxybenzoic acid (4HBZC), saccharin (SAC), theophylline (THEO), caffeine (CAF), and urea (URE). Results indicate that NVP-SA, NVP-SAC, NVP-3HBZC, and NVP-4HBZC are cocrystals, whereas NVP-THEO and NVP-CAF are eutectic materials, and NVP-URE is a solid physical mixture. A temperature-dependent disorder behavior was identified for NVP-SA cocrystal. Dissolution studies for the eutectic materials are reported, evidencing that these materials exhibit a significant increase in NVP dissolution kinetics.Fil: Costa, Rogeria Nunes. Universidade Federal de Sao Paulo; BrasilFil: Reviglio, Ana Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Siedler, Sana. Universidade Federal de Santa Catarina; BrasilFil: Cardoso, Simone G.. Universidade Federal de Santa Catarina; BrasilFil: Garro Linck, Yamila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Monti, Gustavo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Carvalho, Alexandre Magnus G.. Centro Nacional de Pesquisa em Energia e Materiais; BrasilFil: Resende, Jackson A. L. C.. Universidade Federal do Mato Grosso do Sul; BrasilFil: Chaves, Marcelo H. C.. Fundación Oswaldo Cruz; BrasilFil: Rocha, Helvético Vinícius Antunes. Fundación Oswaldo Cruz; BrasilFil: Choquesillo Lazarte, Duane. Consejo Superior de Investigaciones Científicas; España. Universidad de Granada; EspañaFil: Infantes, Lourdes. Consejo Superior de Investigaciones Científicas; España. Instituto de Química Física Rocasolano; EspañaFil: Cuffini, Silvia Lucia. Universidade de Sao Paulo; Brasi

The Prion Protein Ligand, Stress-Inducible Phosphoprotein 1, Regulates Amyloid-beta Oligomer Toxicity

In Alzheimer\u27s disease (AD), soluble amyloid-beta oligomers (A beta Os) trigger neurotoxic signaling, at least partially, via the cellular prion protein (PrPC). However, it is unknown whether other ligands of PrPC can regulate this potentially toxic interaction. Stress-inducible phosphoprotein 1 (STI1), an Hsp90 cochaperone secreted by astrocytes, binds to PrPC in the vicinity of the A beta O binding site to protect neurons against toxic stimuli. Here, we investigated a potential role of STI1 in A beta O toxicity. We confirmed the specific binding of A beta Os and STI1 to the PrP and showed that STI1 efficiently inhibited A beta O binding to PrP in vitro (IC50 of similar to 70 nM) and also decreased A beta O binding to cultured mouse primary hippocampal neurons. Treatment with STI1 prevented A beta O-induced synaptic loss and neuronal death in mouse cultured neurons and long-term potentiation inhibition in mouse hippocampal slices. Interestingly, STI1-haploinsufficient neurons were more sensitive to A beta O-induced cell death and could be rescued by treatment with recombinant STI1. Noteworthy, both A beta O binding to PrPC and PrPC-dependent A beta O toxicity were inhibited by TPR2A, the PrPC-interacting domain of STI1. Additionally, PrPC-STI1 engagement activated alpha 7 nicotinic acetylcholine receptors, which participated in neuroprotection against A beta O-induced toxicity. We found an age-dependent upregulation of cortical STI1 in the APPswe/PS1dE9 mouse model of AD and in the brains of AD-affected individuals, suggesting a compensatory response. Our findings reveal a previously unrecognized role of the PrPC ligand STI1 in protecting neurons in AD and suggest a novel pathway that may help to offset A beta O-induced toxicity

The Milky Way's circular velocity curve between 4 and 14 kpc from APOGEE data

We measure the Milky Way's rotation curve over the Galactocentric range 4 kpc <~ R <~ 14 kpc from the first year of data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE). We model the line-of-sight velocities of 3,365 stars in fourteen fields with b = 0 deg between 30 deg < l < 210 deg out to distances of 10 kpc using an axisymmetric kinematical model that includes a correction for the asymmetric drift of the warm tracer population (\sigma_R ~ 35 km/s). We determine the local value of the circular velocity to be V_c(R_0) = 218 +/- 6 km/s and find that the rotation curve is approximately flat with a local derivative between -3.0 km/s/kpc and 0.4 km/s/kpc. We also measure the Sun's position and velocity in the Galactocentric rest frame, finding the distance to the Galactic center to be 8 kpc < R_0 < 9 kpc, radial velocity V_{R,sun} = -10 +/- 1 km/s, and rotational velocity V_{\phi,sun} = 242^{+10}_{-3} km/s, in good agreement with local measurements of the Sun's radial velocity and with the observed proper motion of Sgr A*. We investigate various systematic uncertainties and find that these are limited to offsets at the percent level, ~2 km/s in V_c. Marginalizing over all the systematics that we consider, we find that V_c(R_0) 99% confidence. We find an offset between the Sun's rotational velocity and the local circular velocity of 26 +/- 3 km/s, which is larger than the locally-measured solar motion of 12 km/s. This larger offset reconciles our value for V_c with recent claims that V_c >~ 240 km/s. Combining our results with other data, we find that the Milky Way's dark-halo mass within the virial radius is ~8x10^{11} M_sun.Comment: submitted to Ap