Non-supersymmetric heterotic model building

We investigate orbifold and smooth Calabi-Yau compactifications of the non-supersymmetric heterotic SO(16)xSO(16) string. We focus on such Calabi-Yau backgrounds in order to recycle commonly employed techniques, like index theorems and cohomology theory, to determine both the fermionic and bosonic 4D spectra. We argue that the N=0 theory never leads to tachyons on smooth Calabi-Yaus in the large volume approximation. As twisted tachyons may arise on certain singular orbifolds, we conjecture that such tachyonic states are lifted in the full blow-up. We perform model searches on selected orbifold geometries. In particular, we construct an explicit example of a Standard Model-like theory with three generations and a single Higgs field.Comment: 1+30 pages latex, 11 tables; v2: references and minor revisions added, matches version published in JHE

Functional traits and phenotypic plasticity modulate species coexistence across contrasting climatic conditions

Functional traits are expected to modulate plant competitive dynamics. However, how traits and their plasticity in response to contrasting environments connect with the mechanisms determining species coexistence remains poorly understood. Here, we couple field experiments under two contrasting climatic conditions to a plant population model describing competitive dynamics between 10 annual plant species in order to evaluate how 19 functional traits, covering physiological, morphological and reproductive characteristics, are associated with species’ niche and fitness differences. We find a rich diversity of univariate and multidimensional associations, which highlight the primary role of traits related to water- and lightuse- efficiency for modulating the determinants of competitive outcomes. Importantly, such traits and their plasticity promote species coexistence across climatic conditions by enhancing stabilizing niche differences and by generating competitive trade-offs between species. Our study represents a significant advance showing how leading dimensions of plant function connect to the mechanisms determining the maintenance of biodiversity

Probing the near infrared stellar population of Seyfert galaxies

We employ IRTF SpeX NIR (0.8-2.4 microns) spectra to investigate the stellar population (SP), active galactic nuclei (AGN) featureless continuum (FC) and hot dust properties in 9 Sy 1 and 15 Sy 2 galaxies. Both the starlight code and the hot dust as an additional base element were used for the first time in this spectral range. We found evidence of correlation among the equivalent widths (W) Si I 1.59 microns x Mg I 1.58 microns, equally for both kinds of activity. Part of the W{Na I 2.21 microns} and W {CO 2.3 microns} strengths may be related to galaxy inclination. Our synthesis shows significant differences between Sy 1 and Sy 2 galaxies: the hot dust component is required to fit the K-band spectra of ~90% of the Sy 1 galaxies, and only of ~25% of the Sy 2; about 50 % of the Sy 2 galaxies require a $FC$ component contribution >20%, while this fraction increases to 60% in the Sy 1; also, in about 50 % of the Sy2, the combined FC and young components contribute with more than 20%, while this occurs in 90% of the Sy1, suggesting recent star formation in the central region. The central few hundred parsecs of our galaxy sample contain a substantial fraction of intermediate-age SPs with a mean metallicity near solar. Our SP synthesis confirms that the 1.1 micron CN band can be used as a tracer of intermediate-age SPs. The simultaneous fitting of SP, FC and hot dust components increased in ~150% the number of AGNs with hot dust detected and the mass estimated. The NIR emerges as an excellent window to study the stellar population of Sy 1 galaxies, as opposed to the usually heavily attenuated optical range. Our approach opens a new way to investigate and quantify the individual contribution of the three most important NIR continuum components observed in AGNs.Comment: The paper contains 14 figures and 5 tables. Accepted for publication in MNRA

Time from first presentation in primary care to treatment of symptomatic colorectal cancer:effect on disease stage and survival

BACKGROUND: British 5-year survival from colorectal cancer (CRC) is below the European average, but the reasons are unclear. This study explored if longer provider delays (time from presentation to treatment) were associated with more advanced stage disease at diagnosis and poorer survival. METHODS: Data on 958 people with CRC were linked with the Scottish Cancer Registry, the Scottish Death Registry and the acute hospital discharge (SMR01) dataset. Time from first presentation in primary care to first treatment, disease stage at diagnosis and survival time from date of first presentation in primary care were determined. Logistic regression and Cox survival analyses, both with a restricted cubic spline, were used to model stage and survival, respectively, following sequential adjustment of patient and tumour factors. RESULTS: On univariate analysis, those with <4 weeks from first presentation in primary care to treatment had more advanced disease at diagnosis and the poorest prognosis. Treatment delays between 4 and 34 weeks were associated with earlier stage (with the lowest odds ratio occurring at 20 weeks) and better survival (with the lowest hazard ratio occurring at 16 weeks). Provider delays beyond 34 weeks were associated with more advanced disease at diagnosis, but not increased mortality. Following adjustment for patient, tumour factors, emergency admissions and symptoms and signs, no significant relationship between provider delay and stage at diagnosis or survival from CRC was found. CONCLUSIONS: Although allowing for a nonlinear relationship and important confounders, moderately long provider delays did not impact adversely on cancer outcomes. Delays are undesirable because they cause anxiety; this may be fuelled by government targets and health campaigns stressing the importance of very prompt cancer diagnosis. Our findings should reassure patients. They suggest that a health service's primary emphasis should be on quality and outcomes rather than on time to treatment

Responses of marine benthic microalgae to elevated CO<inf>2</inf>

Increasing anthropogenic CO2 emissions to the atmosphere are causing a rise in pCO2 concentrations in the ocean surface and lowering pH. To predict the effects of these changes, we need to improve our understanding of the responses of marine primary producers since these drive biogeochemical cycles and profoundly affect the structure and function of benthic habitats. The effects of increasing CO2 levels on the colonisation of artificial substrata by microalgal assemblages (periphyton) were examined across a CO2 gradient off the volcanic island of Vulcano (NE Sicily). We show that periphyton communities altered significantly as CO2 concentrations increased. CO2 enrichment caused significant increases in chlorophyll a concentrations and in diatom abundance although we did not detect any changes in cyanobacteria. SEM analysis revealed major shifts in diatom assemblage composition as CO2 levels increased. The responses of benthic microalgae to rising anthropogenic CO2 emissions are likely to have significant ecological ramifications for coastal systems. © 2011 Springer-Verlag

Hepatitis C virus infection acquired in childhood

Hepatitis C virus (HCV) infection occurs less frequently in children than in adult patients, and the natural history, prognosis, and clinical significance of HCV infection in children are poorly defined. We report here a descriptive follow-up of the clinical course, biochemical data, and viral markers observed in 37 children with anti-HCV. Ten patients included in the study tested persistently negative for serum HCV-RNA (group 1) and 27 patients tested persistently positive (group 2). In group 1, serum alanine aminotransferase (ALT) was normal in all patients, while two patients had non-organ-specific autoantibodies. In group 2, serum ALT was elevated in 13 of 27 patients, and five patients had non-organ-specific autoantibodies. HCV genotype 1a and 1b were the most prevalent among HCV-RNA-positive patients. Twenty liver biopsies were carried out on 17 patients in our series (mean evolution time, 11.2 years; range, 3–21 years). The liver specimens showed mild necroinflammatory changes in most patients, and fibrosis was absent or low grade. Two HCV-RNA-positive patients became persistently HCV-RNA negative. Of the 26 children investigated, 7 (one in group 1, six in group 2) had a co-infection with hepatitis G virus. Conclusion Most children chronically infected with HCV were asymptomatic and presented only mild biochemical evidence of hepatic injury. Autoimmunity in the form of non-organ-specific autoantibodies was common. HCV in children induced mild changes in the liver with a low level of fibrosis and at a low rate of progression

Synchronous malignant B-cell lymphoma and gastric tubular adenocarcinoma associated with paraneoplastic cutaneous vasculitis: hypereosinophilic syndrome with mixed cryoglobulinemia is an important sign of paraneoplastic syndrome

Gastric adenocarcinoma developing concomitantly with a lymphoma is rare. Furthermore, B-cell lymphoma, originating from lymph nodes, with eosinophilia is extremely rare. We report here a case with a synchronous diffuse large B-cell lymphoma (DLBCL) and an early adenocarcinoma of the stomach. In addition, this case seemed to be associated with paraneoplastic cutaneous vasculitis caused by hypereosinophilic syndrome (HES) with mixed cryoglobulinemia (MC). Many neoplastic diseases that affect internal organs display cutaneous manifestations, which may be the presenting signs and symptoms of the underlying malignancy. In particular, the association between cutaneous vasculitis and malignancy has been widely reviewed, and recently neoplasms have been suggested to produce antigens and the resultant immune complex formations, activating the serum complement, thus cause paraneoplastic vasculitis. In this case, severe eosinophilia and cryoglobulinemia with low complements were observed in a laboratory test. A biopsy specimen from a skin lesion revealed leukocytoclastic vasculitis with severe perivascular infiltration of eosinophils. The cutaneous vasuculitis was considered to be a manifestation of HES with MC, although there were no etiological factors of HES and MC. Therefore, the vasculitis seems to be a symptom of paraneoplastic syndrome in this case. Our finding suggests that the potential presence of malignancies should be kept in mind as a possible underlying disorder especially in the presence of HES with MC; this possibility is interesting also as regards at least part of the pathogenesis for paraneplastic syndrome