Phase diagram of the ST2 model of water

We evaluate the free energy of the fluid and crystal phases for the ST2 potential [F.H. Stillinger and A. Rahman, J. Chem. Phys. 60, 1545 (1974)] with reaction field corrections for the long-range interactions. We estimate the phase coexistence boundaries in the temperature-pressure plane, as well as the gas-liquid critical point and gas-liquid coexistence conditions. Our study frames the location of the previously identified liquid-liquid critical point relative to the crystalline phase boundaries, and opens the way for exploring crystal nucleation in a model where the metastable liquid-liquid critical point is computationally accessible

The kaon nucleon interaction

A new forward dispersion relation is developed to describe the kaon nucleon interaction by observing that the real part of resonant partial wave amplitude goes through a zero at the resonance position. This relation eliminates some of the practical deficiencies inherent in the conventional forward dispersion relations. The nKN and ΣKN coupling constants are determined by using the combinations of dispersion relations suggested by Lusignoli et al. evaluated at the kaon nucleon threshold. Initially the energy independent scattering lengths of Kim are used to parametrise the K(^-)N amplitudes in the low energy region in terms of a single channel s-wave zero-range approximation. Just above threshold the K(^+)N amplitudes are parametrised in terms of the constant s-wave scattering lengths and effective range terms found by Goldhaber et al. and Stenger et al. Subsequently, the K(^-)N s-wave scattering lengths are given an energy dependence in the unphysical region through the multi-channel K matrix formalism. Various constraints are placed on these I = 0 K(^-)N scattering lengths such that the constant elements ɤₒ, βₒ, ɤₒ of the corresponding R-matrix should reproduce the Yₒ*(1405) resonance with its correct position and width in the Σπ-Σπ channel, and also the values of the energy independent scattering lengths at the K(^-)N threshold. Furthermore, an energy dependence is then introduced ɤₒ, βₒ, ɤₒ. Similarly, using the 1=1 K(^-)N energy independent and dependent scattering lengths in the appropriate dispersion relation gives an equation for the ΣKN coupling constant which involves the p-wave Y*(1385) resonance. The effects of this resonance are approximated in terms of its position and width and the Y*(_1)KN coupling constant. A brief survey of previous determinations of the n, Σ coupling constants shows that these predictions are consistent within the large errors, except for a very recent calculation performed by Kim. By differentiating specific forward dispersion relations an attempt is made to calculate the nKN, ΣKN and Y*KN coupling constants explicitly. However, the results indicate a slight inconsistency in the values obtained from conventional forward dispersion relations, while the predictions of the new relations are reasonable within the large errors. Finally, the predictions of the new relations are conpared with the experimental data for the K-(^+)p interactions and the charge exchange processes. The results are found to be in good agreement

An investigation into the analysis of ecdysones and other steroid hormones

As an aid to the analysis of ecdysones (arthropod moulting hormones), an investigation has been carried out to find an efficient and sensitive method for determining them by chromatography. A series of fluorocarbonsilanes were synthesized and tested as electron capturing derivatives for gas chromatography. Flophemesyl* (*pentafluorophenyldimethylsilyl) derivatives of mammalian steroids were volatile and sensitive to detection. The derivatives produced characteristic mass spectra with a greater proportion of the ion current carried by hydrocarbon fragments than with other siloxy derivatives making flophemesyl derivatives more suitable for structural determinations. A series of flophemesyl reagents were developed for selectively protecting hydroxyl groups in different steric environments. New methods of synthesis of some of these reagents and analytical techniques for their identification were established. In their mass spectra, unusual rearrangements were found to occur between the fluorine atoms of the pentafluorophenyl ring and the methyl groups bonded to silicon, giving hydrofluorocarbon tropylium-type ions. Flophemesyl derivatives, although useful for mammalian steroids did not give volatile derivatives of ecdysones. The introduction of the pentafluorophenyl ring into steroids as pentafluorophenylhydrazones or pentafluorophenylboronic esters was attempted. The hydrazones, as ketone derivatives, had poor GC characteristics and limited stability when exposed to light or the atmosphere. The pentafluorophenylboronic esters were susceptible to disproportionationin the presence of traces of water or other strong nucleophiles. Boron can be selectively detected with a nitrogen thermionic detector. Boronic esters of model steroids were detected at lower levels than with the FID, but the estimated sensitivity for ecdysones was insufficient for trace level analysis. As ecdysone TMS ethers fragment to produce mass spectra containing a few ions of relatively high intensity, the possibility of using the mass spectrometer as a gas chromatographic detector was investigated. The ecdysone derivatives could only be chromatographed at high temperatures as low carrier gas flow rates had to be used to meet the vacuum requirements of the mass spectrometer. An excessive column background made quantification difficult at trace levels. Optimum GC-MS conditions for steroid analysis were established. The model steroids 28,30-dihydroxy-5a-cholestane and 28,3$,lUa-tri- hydroxy-50-cholest-7-en-6-one were prepared by published procedures; 5a-cholest-7-en-6-one and 14a-hydroxy-5o-cholest-7~en-6-one were synthesised for the first time in good overall yield. In an investigation of the formation of ecdysone THS ethers and the formation of heptafluorobutyrate esters by an exchange reaction with the TMS ethers, it was discovered that the ecdysone nucleus contains the features necessary for electron capture without the need for the formation of halogenated derivatives. The electrophore was identified as the unsaturated ketone, the C-14 oxy substituent with a smaller contribution from the more remote 28,30-oxy substituents. The rate of formation of the TMS ethers of ecdysterone hydroxyl groups with trimethylsilylimidazole was found to be 2,3,22,25>20>>1*U The degree of TMS ether formation in ecdysone and ecdysterone was confirmed by mass spectrometry of the derivatives and also by selective silylation of model steroids. Ecdysones in biological samples were determined as their TMS ethers after a preliminary extraction, solvent partition and TLC separation from impurities. The method has been applied to determine the daily changes in ecdysone content in the desert locust, Schistocerca gregaria. A brief survey of high pressure liquid chromatography illustrated the potential of this technique for the detection and separation of ecdysones

Implementing a Three-Tier Data Warehouse

This paper aims at developing a 3-tier inter-universities data warehouse prototype for the Egyptian universities. The implementation scope is restricted to the student enrollment process. The bottom-up approach and the multi-tier (3-tier) client/server architecture were used to implement the proposed prototype. The implementation required a number of steps to be undertaken. First, a star schema data warehouse was built based on an operational database of a public university. Second, another star schema data warehouse was built based on an operational database of a private university. Third, data from the two warehouses were abstracted to formulate the inter-universities data warehouse (tier 3). Hence, a data cube based on the resulting interuniversities data warehouse was developed using an OLAP server (tier 2). The data cube is then accessed by a client tool (tier 1) for the purpose of query and analysis. Although two universities were used to implement the interuniversities data warehouse, this scenario could be applied with any number of universities in a quite similar way. This inter-universities prototype is scalable and flexible to retain more than two universities regardless of the size of the operational databases. The interuniversities prototype fosters the coordination between participating universities and supports the decision making process. The proposed system could be used to generate a variety of strategic reports

Locally Preferred Structure and Frustration in Glassforming Liquids: A Clue to Polyamorphism?

We propose that the concept of liquids characterized by a given locally preferred structure (LPS) could help in understanding the observed phenomenon of polyamorphism. ``True polyamorphism'' would involve the competition between two (or more) distinct LPS, one favored at low pressure because of its low energy and one favored at high pressure because of its small specific volume, as in tetrahedrally coordinated systems. ``Apparent polyamorphism'' could be associated with the existence of a poorly crystallized defect-ordered phase with a large unit cell and small crystallites, which may be illustrated by the metastable glacial phase of the fragile glassformer triphenylphosphite; the apparent polyamorphism might result from structural frustration, i. e., a competition between the tendency to extend the LPS and a global constraint that prevents tiling of the whole space by the LPS.Comment: 11, 6 figures, Proceedings of the Conference "Horizons in Complex Systems", Messina; in honor of the 60th birthday of H.E. Stanle

Association Between Depression and Physical Conditions Requiring Hospitalization

IMPORTANCE: Depression is associated with an increased risk of physical illness, but the most common causes of hospitalization among people with depression are unclear. OBJECTIVE: To examine the association of depression with an array of physical conditions requiring hospital treatment. DESIGN, SETTING, AND PARTICIPANTS: In this outcomewide prospective multicohort study, primary analysis was based on data from the UK Biobank, a population-based study in the United Kingdom. Analyses were repeated in an independent data set of 2 cohorts in Finland, a population-based study and an occupational cohort. Data analysis was conducted between April and September 2022. EXPOSURES: Self-reported depression, recurrent severe major depression, recurrent moderate major depression, and a single major depressive episode. MAIN OUTCOMES AND MEASURES: A total of 77 common health conditions ascertained from linkage data to national hospital and mortality registries. RESULTS: The analytical sample of UK Biobank participants consisted of 130 652 individuals (71 565 women [54.8%]; 59 087 men [45.2%]; mean [SD] age at baseline, 63.3 [7.8] years). The pooled data from the Finnish replication cohorts included 109 781 participants (82 921 women [78.6%]; 26 860 men [21.4%]; mean [SD] age, 42 [10.8] years). In the main analysis, severe/moderately severe depression was associated with the incidence of 29 nonoverlapping conditions requiring hospital treatment during a 5-year follow-up. Twenty-five of these associations remained after adjustment for confounders and multiple testing (adjusted hazard ratio [HR] range, 1.52-23.03) and were confirmed in the analysis of the Finnish cohorts. These included sleep disorders (HR, 5.97; 95% CI, 3.27-10.89), diabetes (HR, 5.15; 95% CI, 2.52-10.50), ischemic heart disease (HR, 1.76; 95% CI, 1.36-2.29), chronic obstructive bronchitis (HR, 4.11; 95% CI, 2.56-6.60), bacterial infections (HR, 2.52; 95% CI, 1.99-3.19), back pain (HR, 3.99; 95% CI, 2.96-5.38), and osteoarthritis (HR, 1.80; 95% CI, 1.46-2.20). The highest cumulative incidence was observed for endocrine and related internal organ diseases (245 per 1000 persons with depression; risk difference relative to unaffected individuals: 9.8%), musculoskeletal diseases (91 per 1000 persons; risk difference, 3.7%), and diseases of the circulatory system and blood (86 per 1000 persons; risk difference, 3.9%). The cumulative incidence was lower for hospital-treated mental, behavioral, and neurological disorders (20 in 1000 persons; risk difference, 1.7%). Depression was also associated with disease progression in people with prevalent heart disease or diabetes, and for 12 conditions, there was evidence of a bidirectional relationship. CONCLUSIONS AND RELEVANCE: In this study, the most common causes of hospitalization in people with depression were endocrine, musculoskeletal, and vascular diseases, not psychiatric disorders. These findings suggest that depression should be considered as a target for the prevention of physical and mental disease

The unusual 2006 dwarf nova outburst of GK Perseii

The 2006 outburst of GK Perseii differed significantly at optical and ultraviolet wavelengths from typical outbursts of this object. We present multi-wavelength (X-ray, UV and optical) Swift and AAVSO data, giving unprecedented broad-band coverage of the outburst, allowing us to follow the evolution of the longer-than-normal 2006 outburst across these wavelengths. In the optical and UV we see a triple-peaked morphology with maximum brightness ~1.5 magnitudes lower than in previous years. In contrast, the peak hard X-ray flux is the same as in previous outbursts. We resolve this dichotomy by demonstrating that the hard X-ray flux only accounts for a small fraction of the total energy liberated during accretion, and interpret the optical/UV outburst profile as arising from a series of heating and cooling waves traversing the disc, caused by its variable density profile.Comment: 9 pages, 7 figures, accepted for publication in MNRA

Jet and accretion power in the most powerful Fermi blazars

Among the blazars detected by the Fermi satellite, we have selected the 23 blazars that in the three months of survey had an average gamma-ray luminosity above 1e48 erg/s. For 17 out of the 23 sources we found and analysed X-ray and optical-UV data taken by the Swift satellite. With these data, implemented by archival and not simultaneous data, we construct the spectral energy distributions, and interpreted them with a simple one-zone, leptonic, synchrotron and inverse Compton model. When possible, we also compare different high energy states of single sources, like 0528+134 and 3C 454.3, for which multiple good sets of multi-wavelength data are available. In our powerful blazars the high energy emission always dominates the electromagnetic output, and the relatively low level of the synchrotron radiation often does not hide the accretion disk emission. We can then constrain the black hole mass and the disk luminosity. Both are large (i.e. masses equal or greater than 1e9 solar masses and disk luminosities above 0.1 Eddington). By modelling the non-thermal continuum we derive the power that the jet carries in the form of bulk motion of particles and fields. On average, the jet power is found to be slightly larger than the disk luminosity, and proportional to the mass accretion rate.Comment: 15 pages, 14 figures, accepted for publication in MNRA

The blazar S5 0014+813: a real or apparent monster?

A strong hard X-ray luminosity from a blazar flags the presence of a very powerful jet. If the jet power is in turn related to the mass accretion rate, the most luminous hard X-ray blazars should pinpoint the largest accretion rates, and therefore the largest black hole masses. These ideas are confirmed by the Swift satellite observations of the blazar S5 0014+813, at the redshift z=3.366. Swift detected this source with all its three instruments, from the optical to the hard X-rays. Through the construction of its spectral energy distribution we are confident that its optical-UV emission is thermal in origin. Associating it to the emission of a standard optically thick geometrically thin accretion disk, we find a black hole mass of 40 billion solar masses, radiating at 40% the Eddington value. The derived mass is among the largest ever found. Super-Eddington slim disks or thick disks with the presence of a collimating funnel can in principle reduce the black hole mass estimate, but tends to produce spectra bluer than observed.Comment: 5 pages, 2 figures, accepted for publication as a letter in MNRAS after minor revisio

Chasing the heaviest black holes of jetted Active Galactic Nuclei

We investigate the physical properties of the 10 blazars at redshift greater than 2 detected in the 3-years all sky survey performed by the Burst Alert Telescope (BAT) onboard the Swift satellite. We find that the jets of these blazars are among the most powerful known. Furthermore, the mass of their central black hole, inferred from the optical-UV bump, exceeds a few billions of solar masses, with accretion luminosities being a large fraction of the Eddington one. We compare their properties with those of the brightest blazars of the 3-months survey performed by the Large Area Telescope (LAT) onboard the Fermi satellite. We find that the BAT blazars have more powerful jets, more luminous accretion disks and larger black hole masses than LAT blazars. These findings can be simply understood on the basis of the blazar sequence, that suggests that the most powerful blazars have a spectral energy distribution with a high energy peak at MeV (or even sub-MeV) energies. This implies that the most extreme blazars can be found more efficiently in hard X-rays, rather than in the high energy gamma-ray band. We then discuss the implications of our findings for future missions, such as the New Hard X-ray Mission (NHXM) and especially the Energetic X-ray Imaging Survey Telescope (EXIST) mission which, during its planned 2 years all sky survey, is expected to detect thousands of blazars, with a few of them at z greater than 6.Comment: Accepted for publication in MNRAS. Absorption due to Lyman-alpha clouds calculated, and optical-UV data de-absorbed. 16 figures, 15 page