New linearization and reweighting for simulations of string sigma-model on the lattice

We study the discretized worldsheet of Type IIB strings in the Gubser-Klebanov-Polyakov background in a new setup, which eliminates a complex phase previously detected in the fermionic determinant. A sign ambiguity remains, which a study of the fermionic spectrum shows to be related to Yukawa-like terms, including those present in the original Lagrangian before the linearization standard in a lattice QFT approach. Monte Carlo simulations are performed in a large region of the parameter space, where the sign problem starts becoming severe and instabilities appear due to the zero eigenvalues of the fermionic operator. To face these problems, simulations are conducted using the absolute value of a fermionic Pfaffian obtained introducing a small twisted-mass term, acting as an infrared regulator, into the action. The sign of the Pfaffian and the low modes of the quadratic fermionic operator are then taken into account by a reweighting procedure of which we discuss the impact on the measurement of the observables. In this setup we study bosonic and fermionic correlators and observe a divergence in the latter, which we argue - also via a one-loop analysis in lattice perturbation theory - to originate from the U(1)-breaking of our Wilson-like discretization for the fermionic sector

Vibrations on pulse tube based Dry Dilution Refrigerators for low noise measurements

Dry Dilution Refrigerators (DDR) based on pulse tube cryo-coolers have started to replace Wet Dilution Refrigerators (WDR) due to the ease and low cost of operation. However these advantages come at the cost of increased vibrations, induced by the pulse tube. In this work, we present the vibration measurements performed on three different commercial DDRs. We describe in detail the vibration measurement system we assembled, based on commercial accelerometers, conditioner and DAQ, and examined the effects of the various damping solutions utilized on three different DDRs, both in the low and high frequency regions. Finally, we ran low temperature, pseudo-massive (30 and 250 g) germanium bolometers in the best vibration-performing system under study and report on the results

Illness in Returned Travelers and Immigrants/Refugees: The 6-Year Experience of Two Australian Infectious Diseases Units.

BACKGROUND: Data comparing returned travelers and immigrants/refugees managed in a hospital setting is lacking. METHODS: We prospectively collected data on 1,106 patients with an illness likely acquired overseas who presented to two hospital-based Australian infectious diseases units over a 6-year period. RESULTS: Eighty-three percent of patients were travelers and 17% immigrants/refugees. In travelers, malaria (19%), gastroenteritis/diarrhea (15%), and upper respiratory tract infection (URTI) (7%) were the most common diagnoses. When compared with immigrants/refugees, travelers were significantly more likely to be diagnosed with gastroenteritis/diarrhea [odds ratio (OR) 8], malaria (OR 7), pneumonia (OR 6), URTI (OR 3), skin infection, dengue fever, typhoid/paratyphoid fever, influenza, and rickettsial disease. They were significantly less likely to be diagnosed with leprosy (OR 0.03), chronic hepatitis (OR 0.04), tuberculosis (OR 0.05), schistosomiasis (OR 0.3), and helminthic infection (OR 0.3). In addition, travelers were more likely to present within 1 month of entry into Australia (OR 96), and have fever (OR 8), skin (OR 6), gastrointestinal (OR 5), or neurological symptoms (OR 5) but were less likely to be asymptomatic (OR 0.1) or have anaemia (OR 0.4) or eosinophilia (OR 0.3). Diseases in travelers were more likely to have been acquired via a vector (OR 13) or food and water (OR 4), and less likely to have been acquired via the respiratory (OR 0.2) or skin (OR 0.6) routes. We also found that travel destination and classification of traveler can significantly influence the likelihood of a specific diagnosis in travelers. Six percent of travelers developed a potentially vaccine-preventable disease, with failure to vaccinate occurring in 31% of these cases in the pretravel medical consultation. CONCLUSIONS: There are important differences in the spectrum of illness, clinical features, and mode of disease transmission between returned travelers and immigrants/refugees presenting to hospital-based Australian infectious diseases units with an illness acquired overseas

Strings on the lattice and AdS/CFT

We present a new auxiliary field representation for the four-fermi term of the gauge-fixed Green-Schwarz superstring action which describes fluctuations around the null-cusp background in $AdS_5\times S^5$. We sketch the main features of the fermionic operator spectrum, identifying the region of parameter space where the sign ambiguity is absent. Measurements for the observables in the setup here described are presented and discussed in a forthcoming publication

Green-Schwarz superstring on the lattice

We consider possible discretizations for a gauge-fixed Green-Schwarz action of Type IIB superstring. We use them for measuring the action, from which we extract the cusp anomalous dimension of planar N=4 SYM as derived from AdS/CFT, as well as the mass of the two AdS excitations transverse to the relevant null cusp classical string solution. We perform lattice simulations employing a Rational Hybrid Monte Carlo (RHMC) algorithm and two Wilson-like fermion discretizations, one of which preserves the global SO(6) symmetry the model. We compare our results with the expected behavior at various values of g=λ√4π . For both the observables, we find a good agreement for large g, which is the perturbative regime of the sigma-model. For smaller values of g, the expectation value of the action exhibits a deviation compatible with the presence of quadratic divergences. After their non-perturbative subtraction the continuum limit can be taken, and suggests a qualitative agreement with the non-perturbative expectation from AdS/CFT. Furthermore, we detect a phase in the fermion determinant, whose origin we explain, that for small g leads to a sign problem not treatable via standard reweigthing. The continuum extrapolations of the observables in the two different discretizations agree within errors, which is strongly suggesting that they lead to the same continuum limit. Part of the results discussed here were presented earlier in [1]

Transient band keratopathy associated with ocular inflammation and systemic hypercalcemia

Anat Galor, Henry A Leder, Jennifer E Thorne, James P DunnThe Wilmer Eye Institute, Department of Ophthalmology, the Johns Hopkins University School of MedicinePurpose: To report a case of visually significant band keratopathy associated with ocular inflammation and systemic hypercalcemia which markedly decreased in severity after treatment of these underlying factors.Methods: Retrospective case report.Results: A 53-year-old Asian female with granulomatous panuveitis in the left eye presented with diffuse band keratopathy through the central cornea. The serum calcium was elevated. The patient was treated with topical prednisolone acetate 1% and oral prednisone with marked improvement in inflammation. The band keratopathy lessened in severity with clearing of the central cornea and improvement in visual acuity.Conclusions: Early medical treatment of underlying factors may allow reversal of band keratopathy.Keywords: ocular inflammation, transient band keratopath

The Origin of Variations in the Isotopic Record of Scleractinian Corals: II. Carbon

This study examines the relationship between the δ13C of the skeleton of a zooxanthellate coral (Montastraea annularis) growing on the Florida Reef Tract and environmental variables (insolation and temperature), physiological variables (growth rate, respiration, calcification, and photosynthesis). Colonies of this species were grown in the field for a 2.5 year study period, during which the rates of photosynthesis, respiration, and calcification were measured on fifteen separate occasions, spaced approximately equally throughout the study period. The corals were stained with alizarin-red S within seven days after each set of physiological measurements. At the end of the period the corals were sacrificed and their skeletal extension, density, and skeletal δ13C determined. Despite substantial high-frequency variations, a strong seasonal cycle was evident in the skeletal δ13C records of all the corals throughout the experimental period. The skeletal δ13C and δ18O values varied approximately in phase, and showed a weak, but statistically significant positive relationship with each other. The δ13C of the coral skeletons, when corrected for changes in the δ13C of dissolved inorganic carbon (DIC), exhibited an inverse correlation with P/R, a finding opposite to what was expected based on current models of isotopic fractionation in coral skeletons. Although such findings tend to support the model of Erez (1978) that increases in photosynthesis act to isotopically deplete the δ13C of the coral skeleton, we note that the inverse association between δ13C and P/R arises because of a slight positive association between δ13C and respiration. We therefore believe that the association may be a result of seasonal variation in some parameters of the system which was not constrained in our study. Alternatives include (1) variations in the δ13C of the DIC which are translated into the δ13C of the food chain, (2) changes from heterotrophy to autotrophy, and (3) changes in the partitioning of δ13C between the zooxanthellae and the coral tissue. Based on previous studies which we have carried out we believe that changes in the skeletal δ13C are not related to sexual reproduction or growth rate. Contrary to previous work we were unable to measure any significant differences in the skeletal δ13C between the fast growing tops of the coral and the slower growing sides

Lattice and string worldsheet in AdS/CFT: a numerical study

We consider a possible discretization for the gauge-fixed Green-Schwarz (two-dimensional) sigma-model action for the Type IIB superstring and use it for measuring the cusp anomalous dimension of planar $\mathcal{N}=4$ SYM as derived from string theory. We perform lattice simulations employing a Rational Hybrid Monte Carlo (RHMC) algorithm and a Wilson-like fermion discretization. In this preliminary study, we compare our results with the expected behavior for very large values of $g=\frac{\sqrt{\lambda}}{4\pi}$, which is the perturbative regime of the sigma-model, and find a qualitative agreement at finite lattice spacing. For smaller $g$ the continuum limit is obstructed by a divergence. We also detect a phase in the fermion determinant, whose origin we explain, which for small $g$ leads to a sign problem not treatable via standard reweigthing. Results presented here are discussed thoroughly in~\cite{toappear}

Mental Models and Social Media Personas: a Case of Amateur Palaeontologists

This study explores social palaeontology - an inclusive and collaborative form of science occurring across digital habitats. The purpose was to: 1) examine conceptualisations of amateurs via expressed mental models and 2) use the unified media-user typology (MUT) to explore any relationship between these models and social media persona. Data collection involved a survey, modelling task and interview. Findings reveal that persona was demonstrated in subtle ways, offering limited evidence for a relationship between persona and mental model. Sequential models were most common, but more so for advanced personas. Expertise development was expressed through the number of conventions used during modelling. However, the degree of inaccuracy suggests a lack of metacognitive awareness, implying that any increase in expertise with persona was not conveyed as such. The results bolster the capacity to design community-centred social spaces and inform understanding of science learning and the utility of MUT as a predictive tool