Energy return on investment (EROI) of solar PV: an attempt at reconciliation

In a recent Point of View piece, William Pickard made an excellent case for the importance of energy return on investment (EROI) as a useful metric for assessing longterm viability of energy-dependent systems from bands of hunter-gatherers, to modern society and, finally to the specific case of a solar electricity generating project. The author then highlighted a seeming disparity between a number of different research groups 1) Fthenakis group at Brookhaven, 2) Prieto group in Madrid, 3) Weißbach group in Berlin, and 4) Brandt group at Stanford all of whom have recently published values for the EROI (or similar metric) for solar photovoltaic (PV) technologies. Unfortunately, in so doing, the author directly compares results calculated using different system boundaries, methodologies, and assumptions. It is the purpose of this response to (1) adjust the results for the four groups to better compare like systems and (2) outline details of two methodological issues common in the EROI literature. The objective of these two activities is to explain much of the apparent disparity between the different EROI values produced by the different research groups

Disease Risk & Landscape Attributes of Tick-Borne Borrelia Pathogens in the San Francisco Bay Area, California

Habitat heterogeneity influences pathogen ecology by affecting vector abundance and the reservoir host communities. We investigated spatial patterns of disease risk for two human pathogens in the Borrelia genus–B. burgdorferi and B. miyamotoi–that are transmitted by the western black-legged tick, Ixodes pacificus. We collected ticks (349 nymphs, 273 adults) at 20 sites in the San Francisco Bay Area, California, USA. Tick abundance, pathogen prevalence and density of infected nymphs varied widely across sites and habitat type, though nymphal western black-legged ticks were more frequently found, and were more abundant in coast live oak forest and desert/semi-desert scrub (dominated by California sagebrush) habitats. We observed Borrelia infections in ticks at all sites where we able to collect >10 ticks. The recently recognized human pathogen, B. miyamotoi, was observed at a higher prevalence (13/349 nymphs = 3.7%, 95% CI = 2.0–6.3; 5/273 adults = 1.8%, 95% CI = 0.6–4.2) than recent studies from nearby locations (Alameda County, east of the San Francisco Bay), demonstrating that tick-borne disease risk and ecology can vary substantially at small geographic scales, with consequences for public health and disease diagnosis

Summary statistics of entomologic risk for <i>Ixodes pacificus</i> infected with <i>Borrelia</i> spp. in recreational areas of the San Francisco Bay Area.

<p>¹Betsy Crowder Trail is comprised of coast live oak woodland.</p><p>²Anniversary Trail is comprised of coastal scrub and moderate grassland.</p><p>³Meadow Trail is comprised of coast live oak woodland and Douglas fir forest.</p><p>Data are presented on density of nymphal (DON) <i>I</i>. <i>pacificus</i> (i.e., number of nymphs/100m² (calculated by (number of ticks collected/meters covered by transects) x100); density of infected nymphs (DIN) for <i>Borrelia</i> spp. (calculated by <i>Borrelia</i> prevalence x DON); and for <i>B</i>. <i>miyamotoi</i>, <i>B</i>. <i>burgdorferi</i> ss, and for <i>B</i>. <i>burgdorferi</i> sl.</p

Recreational areas in the San Francisco Bay area (left) sampled for western black-legged ticks, with a close-up (right) of recreational areas sampled in San Mateo and Santa Clara Counties.

<p>Recreational areas in the San Francisco Bay area (left) sampled for western black-legged ticks, with a close-up (right) of recreational areas sampled in San Mateo and Santa Clara Counties.</p

Prevalence data for <i>Borrelia</i> in <i>I</i>. <i>pacificus</i> ticks from previous studies in California.

<p>¹Number positive/number tested (percentage positive, 95% CI).</p><p>Prevalence data for <i>Borrelia</i> in <i>I</i>. <i>pacificus</i> ticks from previous studies in California.</p

Study area showing independent variables: soil type (top left), elevation (top right), vegetation type (bottom left) and distance to roads (bottom right).

<p>Purple dots represent tick- drag transects in Santa Clara and San Mateo counties.</p

Prevalence of Early B-Cell Factor 1 Gene rs4704963 Single Nucleotide Polymorphism (T>C) in a Population of Type 2 Diabetic Patients with Obesity

Background: Previous studies established that in a population with exacerbation of type 2 diabetes with obesity (DBT+Ob)suffering from stress, the prevalence of early B-Cell Factor 1 (EBF1) gene rs4704963 single nucleotide polymorphism (SNP)(T>C) is 16.5%.Objectives: The aim of this study was to determine the prevalence of this SNP in patients with DBT+Ob attending HospitalRamos Mejía of the Autonomous City of Buenos Aires and to ascertain whether this polymorphism is associated with stressor acute coronary events.Methods: An observational, prospective study on the prevalence of rs4704963 SNP was performed in 53 patients with DBT+Oband body mass index between 28 and 41, seen in Hospital Ramos Mejía for a period of 15 months. Each patient was evaluatedwith a stressful life events scale and a perceived stress scale.The chi-square test and odds ratio (OR) were used for statistical analysis.Results: A total of 53 patients were included in the study. Mean population age was 60.2±9.77 years and 47.2% were men.Among these patients, 8 (15.1%) presented SNP and all were heterozygous. Fifteen patients (28.3%) had acute ischemicsyndrome (AIS), and among these, only one (6.6%) had SNP. No statistically significant relationship was found between thepresence of SNP and AIS (p=0.282). Fourteen patients (26.4%) presented moderate or severe chronic stress, and there wasno relationship between this finding and the presence of SNP (p=0.979).Conclusions: The prevalence of EBF1 gene rs4704963 SNP (T>C) in the DBT+Ob population was 15.1%. No statisticallysignificant association was found between SNP and stress or AIS.Introducción: En estudios previos, se determinó para una población con agravamiento de la diabetes tipo 2 con obesidad(DBT+Ob) que sufría estrés una prevalencia del polimorfismo de nucleótido único (SNP) rs4704963 (T > C) del gen EarlyB-Cell Factor 1 (EBF1) del 16,5%.Objetivos: Determinar la prevalencia de este SNP en pacientes con DBT+ Ob que acuden al Hospital Ramos Mejía de la CiudadAutónoma de Buenos .Aires y establecer si dicho polimorfismo se asocia con el estrés o la ocurrencia de eventos coronariosagudos.Material y métodos: Se llevó a cabo un estudio observacional, prospectivo, sobre prevalencia del polimorfismo en 53 pacientescon DBT+Ob e índice de masa corporal (IMC) entre 28 y 41, atendidos en el citado hospital en un período de 15 meses. Acada paciente se le computó una escala de estrés percibido, además de evaluarlo mediante la escala de acontecimientos vitalesestresantes.Para el análisis estadístico, se realizaron las pruebas de Chi cuadrado y se calcularon los odds ratio (OR).Resultados: La población evaluada (53 pacientes) tuvo una media de edad de 60,2 ±9,77 años; 47,2% fueron hombres. De ellos,8 individuos (15,1%) presentaron el SNP y todos fueron heterocigotas. Quince sujetos (28,3%) tuvieron síndrome isquémicoagudo (SIA) y de estos solo uno (6,6%) tenía el SNP. No se halló relación estadísticamente significativa entre la presencia delSNP y la aparición de SIA (p = 0,282). Catorce pacientes (26,4%) presentaron estrés crónico moderado o grave, y no huborelación entre este hallazgo y la presencia del SNP (p = 0,979).Conclusiones: La prevalencia del SNP rs4704963 (T > C) del gen EBF1 en la población de DBT+Ob estudiada fue del 15,1%y no se halló relación estadísticamente significativa del SNP con el estrés ni con el SIA