Some Results On Normal Homogeneous Ideals

In this article we investigate when a homogeneous ideal in a graded ring is normal, that is, when all positive powers of the ideal are integrally closed. We are particularly interested in homogeneous ideals in an N-graded ring generated by all homogeneous elements of degree at least m and monomial ideals in a polynomial ring over a field. For ideals of the first trype we generalize a recent result of S. Faridi. We prove that a monomial ideal in a polynomial ring in n indeterminates over a field is normal if and only if the first n-1 positive powers of the ideal are integrally closed. We then specialize to the case of ideals obtained by taking integral closures of m-primary ideals generated by powers of the variables. We obtain classes of normal monomial ideals and arithmetic critera for deciding when the monomial ideal is not normal.Comment: 19 page

Internet searching produces misleading findings regarding violent deaths in crisis settings: short report

Donor and agency priorities are influenced by a variety of political, social, and media-related forces that can have a profound impact on response and resource provision. We have attempted to assess how well internet searches articulate the span of violent death rates for five current “crisis” settings. In three graduate classes (2 public health, 1 information science) at US universities, during a four month period in 2017–2018, we asked approximately 60 graduate students to conduct an internet search to determine which of five countries had the highest and lowest “violence specific mortality rate”: Venezuela, Syria, Yemen, Central African Republic (CAR), or Mali. Students were divided into groups of three, and within each group explored this question by three approaches. Many graduate students in all groups could not determine the relative rates, especially which country had the lowest violence specific mortality rate. Of the 34 searches that identified a highest violent death rate country, 27.5 (81%) concluded it was Venezuela, followed by Syria (4.5; 13%), Mali (1; 3%) and CAR (1; 3%). Of the 26 searches that identified a least violent death rate 21.5 (83%) reported either CAR or Mali, followed by Yemen (2.5; 10%) and Syria (2; 8%). Aside from lack of data on CAR and Mali, students were perplexed about whether to include suicides or executions in the measure. This resulted in almost half of all inquiries unable to estimate a highest and lowest rate among these five countries. Where conclusions were drawn, it is likely the internet drew students to the opposite conclusion from reality. There are several reasons for this discordance, such as differing categories of violent deaths as defined by the World Health Organization, and search engine algorithms. It is probable, however, that larger issues of connectivity of individual societies with each other and the outside world are playing a profound role in the deceptive results found in this exercise. This insight emphasizes the internet’s under-reporting in the world’s most poor and remote locations, and highlights the importance of primary data collection and reporting in such settings

Classes of normally and nearly normally torsion-free monomial ideals

In this paper, our main focus is to explore different classes of nearly normally torsion-free ideals. We first characterize all finite simple connected graphs with nearly normally torsion-free cover ideals. Next, we characterize all normally torsion-free $t$-spread principal Borel ideals that can also be viewed as edge ideals of uniform multipartite hypergraphs

Ecological criteria for evaluation candidate sites for marine reserves

Several schemes have been developed to help select the locations of marine reserves. All of them combine social, economic, and biological criteria, and few offer any guidance as to how to prioritize among the criteria identified. This can imply that the relative weights given to different criteria are unimportant. Where two sites are of equal value ecologically, then socioeconomic criteria should dominate the choice of which should be protected. However, in many cases, socioeconomic criteria are given equal or greater weight than ecological considerations in the choice of sites. This can lead to selection of reserves with little biological value that fail to meet many of the desired objectives. To avoid such a possibility, we develop a series of criteria that allow preliminary evaluation of candidate sites according to their relative biological values in advance of the application of socioeconomic criteria. We include criteria that, while not strictly biological, have a strong influence on the species present or ecological processes. Our scheme enables sites to be assessed according to their biodiversity, the processes which underpin that diversity, and the processes that support fisheries and provide a spectrum of other services important to people. Criteria that capture biodiversity values include biogeographic representation, habitat representation and heterogeneity, and presence of species or populations of special interest (e.g., threatened species). Criteria that capture sustainability of biodiversity and fishery values include the size of reserves necessary to protect viable habitats, presence of exploitable species, vulnerable life stages, connectivity among reserves, links among ecosystems, and provision of ecosystem services to people. Criteria measuring human and natural threats enable candidate sites to be eliminated from consideration if risks are too great, but also help prioritize among sites where threats can be mitigated by protection. While our criteria can be applied to the design of reserve networks, they also enable choice of single reserves to be made in the context of the attributes of existing protected areas. The overall goal of our scheme is to promote the development of reserve networks that will maintain biodiversity and ecosystem functioning at large scales. The values of ecosystem goods and services for people ultimately depend on meeting this objective

Can changes in angiogenic biomarkers between the first and second trimesters of pregnancy predict development of pre-eclampsia in a low-risk nulliparous patient population?

OBJECTIVE: To determine if change in maternal angiogenic biomarkers between the first and second trimesters predicts pre-eclampsia in low-risk nulliparous women. DESIGN: A nested case-control study of change in maternal plasma soluble Flt-1 (sFlt-1), soluble endoglin (sEng) and placenta growth factor (PlGF). We studied 158 pregnancies complicated by pre-eclampsia and 468 normotensive nonproteinuric controls. SETTING: A multicentre study in 16 academic medical centres in the USA. POPULATION: Low-risk nulliparous women. METHODS: Luminex assays for PlGF, sFlt-1 and sEng performed on maternal EDTA plasma collected at 9-12, 15-18 and 23-26 weeks of gestation. Rate of change of analyte between first and either early or late second trimester was calculated with and without adjustment for baseline clinical characteristics. MAIN OUTCOME MEASURES: Change in PlGF, sFlt-1 and sEng. RESULTS: Rates of change of PlGF, sEng and sFlt-1 between first and either early or late second trimesters were significantly different in women who developed pre-eclampsia, severe pre-eclampsia or early-onset pre-eclampsia compared with women who remained normotensive. Inclusion of clinical characteristics (race, body mass index and blood pressure at entry) increased sensitivity for detecting severe and particularly early-onset pre-eclampsia but not pre-eclampsia overall. Receiver operating characteristics curves for change from first to early second trimester in sEng, PlGF and sFlt-1 with clinical characteristics had areas under the curve of 0.88, 0.84 and 0.86, respectively, and for early-onset pre-eclampsia with sensitivities of 88% (95% CI 64-99), 77% (95% CI 50-93) and 77% (95% CI 50-93) for 80% specificity, respectively. Similar results were seen in the change from first to late second trimester. CONCLUSION: Change in angiogenic biomarkers between first and early second trimester combined with clinical characteristics has strong utility for predicting early-onset pre-eclampsia

Communicating leakage risk in the hydrogen economy : lessons already learned from geoenergy industries

Hydrogen may play a crucial part in delivering a net zero emissions future. Currently, hydrogen production, storage, transport and utilisation are being explored to scope opportunities and to reduce barriers to market activation. One such barrier could be negative public response to hydrogen technologies. Previous research around socio-technical risks finds that public acceptance issues are particularly challenging for emerging, remote, technical, sensitive, uncertain or unfamiliar technologies - such as hydrogen. Thus, while the hydrogen value chain could offer a range of potential environmental, economic and social benefits, each will have perceived risks that could challenge the introduction and subsequent roll-out of hydrogen. These potential issues must be identified and managed so that the hydrogen sector can develop, adapt or respond appropriately. The geological storage of hydrogen could present challenges in terms of the perceived safety of the approach. Valuable lessons can be learned from international research and practice of CO2 and natural gas storage in geological formations (for carbon capture and storage, CCS, and for power, respectively). Here, we explore these learnings. We consider the similarities and differences between these technologies, and how these may affect perceived risks. We also reflect on lessons for effective communication and community engagement. We draw on this to present potential risks to the perceived safety of - and public acceptability of – the geological storage of hydrogen. One of the key lessons learned from CCS and natural gas storage is that progress is most effective when risk communication and public acceptability is considered from the early stages of technology development

Photometric Monitoring of Open Clusters I. The Survey

Open clusters, which have age, abundance, and extinction information from studies of main-sequence turn off stars, are the ideal location in which to determine the mass-luminosity-radius relation for low-mass stars. We have undertaken a photometric monitoring survey of open clusters in the Galaxy designed to detect low-mass eclipsing binary systems through variations in their relative light curves. Our aim is to provide an improved calibration of the mass-luminosity-radius relation for low-mass stars and brown dwarfs, to test stellar structure and evolution models, and to help quantify the contribution of low-mass stars to the global mass census in the Galaxy. In this paper we present our survey, describing the data and outlining the analysis techniques. We study six nearby open clusters, with a range of ages from $\sim 0.2$ to 4 Gyr and metallicities from approximately solar to -0.2dex. We monitor a field-of-view of > 1 square degree per target cluster, well beyond the characteristic cluster radius, over timescales of hours, days, and months with a sampling rate optimised for the detection of eclipsing binaries with periods of hours to days. Our survey depth is designed to detect eclipse events in a binary with a primary star of \lesssim 0.3~M_{\sun}. Our data have a photometric precision of $\sim 3$ mmag at $I\approx 16$.Comment: 50 pages, 18 figures, accepted for publication in A

The structure of the PapD-PapGII pilin complex reveals an open and flexible P5 pocket

P pili are hairlike polymeric structures that mediate binding of uropathogenic Escherichia coli to the surface of the kidney via the PapG adhesin at their tips. PapG is composed of two domains: a lectin domain at the tip of the pilus followed by a pilin domain that comprises the initial polymerizing subunit of the 1,000-plus-subunit heteropolymeric pilus fiber. Prior to assembly, periplasmic pilin domains bind to a chaperone, PapD. PapD mediates donor strand complementation, in which a beta strand of PapD temporarily completes the pilin domain's fold, preventing premature, nonproductive interactions with other pilin subunits and facilitating subunit folding. Chaperone-subunit complexes are delivered to the outer membrane usher where donor strand exchange (DSE) replaces PapD's donated beta strand with an amino-terminal extension on the next incoming pilin subunit. This occurs via a zip-in-zip-out mechanism that initiates at a relatively accessible hydrophobic space termed the P5 pocket on the terminally incorporated pilus subunit. Here, we solve the structure of PapD in complex with the pilin domain of isoform II of PapG (PapGIIp). Our data revealed that PapGIIp adopts an immunoglobulin fold with a missing seventh strand, complemented in parallel by the G1 PapD strand, typical of pilin subunits. Comparisons with other chaperone-pilin complexes indicated that the interactive surfaces are highly conserved. Interestingly, the PapGIIp P5 pocket was in an open conformation, which, as molecular dynamics simulations revealed, switches between an open and a closed conformation due to the flexibility of the surrounding loops. Our study reveals the structural details of the DSE mechanism

Traumatic Stress Interacts With Bipolar Disorder Genetic Risk to Increase Risk for Suicide Attempts

Objective Bipolar disorder (BD) is one of the most heritable psychiatric conditions and is associated with high suicide risk. To explore the reasons for this link, this study examined the interaction between traumatic stress and BD polygenic risk score in relation to suicidal ideation, suicide attempt, and nonsuicidal self-injury (NSSI) in adolescent and young adult offspring and relatives of persons with BD (BD-relatives) compared with adolescent and young adult offspring of individuals without psychiatric disorders (controls). Method Data were collected from 4 sites in the United States and 1 site in Australia from 2006 through 2012. Generalized estimating equation models were used to compare rates of ideation, attempts, and NSSI between BD-relatives (n = 307) and controls (n = 166) and to determine the contribution of demographic factors, traumatic stress exposure, lifetime mood or substance (alcohol/drug) use disorders, and BD polygenic risk score. Results After adjusting for demographic characteristics and mood and substance use disorders, BD-relatives were at increased risk for suicidal ideation and attempts but not for NSSI. Independent of BD-relative versus control status, demographic factors, or mood and substance use disorders, exposure to trauma within the past year (including bullying, sexual abuse, and domestic violence) was associated with suicide attempts (p = .014), and BD polygenic risk score was marginally associated with attempts (p = .061). Importantly, the interaction between BD polygenic risk score and traumatic event exposures was significantly associated with attempts, independent of demographics, relative versus control status, and mood and substance use disorders (p = .041). Conclusion BD-relatives are at increased risk for suicide attempts and ideation, especially if they are exposed to trauma and have evidence of increased genetic vulnerability