1,224 research outputs found
Extended conjugated microporous polymers for photocatalytic hydrogen evolution from water
Conjugated microporous polymers (CMPs) have been used as photocatalysts for hydrogen production from water in the presence of a sacrificial electron donor. The relative importance of the linker geometry, the co-monomer linker length, and the degree of planarisation were studied with respect to the photocatalytic hydrogen evolution rate
Searching High Redshift Large-Scale Structures: Photometry of Four Fields Around Quasar Pairs at z~1
We have studied the photometric properties of four fields around the
high-redshift quasar pairs QP1310+0007, QP1355-0032, QP0110-0219, and
QP0114-3140 at z ~ 1 with the aim of identifying large-scale structures- galaxy
clusters or groups- around them. This sample was observed with GMOS in Gemini
North and South telescopes in the g', r', i', and z' bands, and our photometry
is complete to a limiting magnitude of i' ~ 24 mag (corresponding to ~ M*_i' +
2 at the redshift of the pairs). Our analysis reveals that QP0110-0219 shows
very strong and QP1310+0007 and QP1355-0032 show some evidence for the presence
of rich galaxy clusters in direct vicinity of the pairs. On the other hand,
QP0114-3140 could be an isolated pair in a poor environment. This work suggest
that z ~ 1 quasar pairs are excellent tracers of high density environments and
this same technique may be useful to find clusters at higher redshifts.Comment: 29 pages, 7 figures, ApJ accepted. Added one figure and 3 references.
Some paragraphs was rewritten in sections 1, 3, 5, and 6, as suggested by
refere
Scaling of Horizontal and Vertical Fixational Eye Movements
Eye movements during fixation of a stationary target prevent the adaptation
of the photoreceptors to continuous illumination and inhibit fading of the
image. These random, involuntary, small, movements are restricted at long time
scales so as to keep the target at the center of the field of view. Here we use
the Detrended Fluctuation Analysis (DFA) in order to study the properties of
fixational eye movements at different time scales. Results show different
scaling behavior between horizontal and vertical movements. When the small
ballistics movements, i.e. micro-saccades, are removed, the scaling exponents
in both directions become similar. Our findings suggest that micro-saccades
enhance the persistence at short time scales mostly in the horizontal component
and much less in the vertical component. This difference may be due to the need
of continuously moving the eyes in the horizontal plane, in order to match the
stereoscopic image for different viewing distance.Comment: 5 pages, 4 figure
Melt-quenched porous organic cage glasses
The discrete molecular nature of porous organic cages (POCs) has allowed us to direct the formation of crystalline materials by crystal engineering. It has also been possible to create porous amorphous solids by deliberately disrupting the crystalline packing, either with chemical modification or by processing. More recently, organic cages were used to form isotropic porous liquids. However, the connection between solid and liquid states of POCs, and the glass state, are almost completely unexplored. Here, we investigate the melting and glass-forming behaviour of a range of organic cages, including both shapepersistent POCs formed by imine condensation, and reduced and synthetically post-modified amine POCs that are more flexible and lack shape-persistence. The organic cages exhibited melting and quenching of the resultant liquids provides molecular glasses. One of these molecular glasses exhibited improved gas uptake for both CO2 and CH4 compared to the starting amorphous cage. In addition, foaming of the liquid in one case resulted in a more stable and less soluble glass, which demonstrates the potential for an alternative approach to forming materials such as membranes without solution processing
The ESO Key-Programme ``A Homogeneous Bright QSO Survey'' - I The Methods and the ``Deep'' Fields
This is the first paper in a series aimed at defining a statistically
significant sample of QSOs in the range and .
The selection is carried out using direct plates obtained at the ESO and UK
Schmidt Telescopes, scanned with the COSMOS facility and searched for objects
with an ultraviolet excess. Follow-up spectroscopy, carried out at ESO La
Silla, is used to classify each candidate. In this initial paper, we describe
the scientific objectives of the survey; the selection and observing techniques
used. We present the first sample of 285 QSOs () in a 153 deg
area, covered by the six ``deep'' fields, intended to obtain significant
statistics down with unprecedented photometric accuracy. From
this database, QSO counts are determined in the magnitude range .Comment: 21 pages uuencoded compressed postscript, to appear in Astronomy and
Astrophysics Supplements, 199
Competitive aminal formation during the synthesis of a highly soluble, isopropyl-decorated imine porous organic cage
The synthesis of a new porous organic cage decorated with isopropyl moieties (CC21) was achieved from the reaction of triformylbenzene and an isopropyl functionalised diamine. Unlike structurally analogous porous organic cages, its synthesis proved challenging due to competitive aminal formation, rationalised using control experiments and computational modelling. The use of an additional amine was found to increase conversion to the desired cage
Modular Type III Porous Liquids Based on Porous Organic Cage Microparticles
The dispersion of particulate porous solids in size-excluded liquids has emerged as a method to create Type III porous liquids, mostly using insoluble microporous materials such as metal–organic frameworks and zeolites. Here, the first examples of Type III porous liquids based on porous organic cages (POCs) are presented. By exploiting the solution processability of the POCs, racemic and quasiracemic cage microparticles are formed by chiral recognition. Dispersion of these porous microparticles in a range of size-excluded liquids, including oils and ionic liquids, forms stable POC-based Type III porous liquids. The flexible pairing between the solid POC particles and a carrier liquid allows the formation of a range of compositions, pore sizes, and other physicochemical properties to suit different applications and operating conditions. For example, it is shown that porous liquids with relatively low viscosities or high thermal stability can be produced. A 12.5 wt% Type III porous liquid comprising racemic POC microparticles and an ionic liquid, [BPy][NTf2], shows a CO2 working capacity (104.30 µmol gL−1) that is significantly higher than the neat ionic liquid (37.27 µmol gL−1) between 25 and 100 °C. This liquid is colloidally stable and can be recycled at least ten times without loss of CO2 capacity
A Renormalization Group Approach to Relativistic Cosmology
We discuss the averaging hypothesis tacitly assumed in standard cosmology.
Our approach is implemented in a "3+1" formalism and invokes the coarse
graining arguments, provided and supported by the real-space Renormalization
Group (RG) methods. Block variables are introduced and the recursion relations
written down explicitly enabling us to characterize the corresponding RG flow.
To leading order, the RG flow is provided by the Ricci-Hamilton equations
studied in connection with the geometry of three-manifolds. The properties of
the Ricci-Hamilton flow make it possible to study a critical behaviour of
cosmological models. This criticality is discussed and it is argued that it may
be related to the formation of sheet-like structures in the universe. We
provide an explicit expression for the renormalized Hubble constant and for the
scale dependence of the matter distribution. It is shown that the Hubble
constant is affected by non-trivial scale dependent shear terms, while the
spatial anisotropy of the metric influences significantly the scale-dependence
of the matter distribution.Comment: 57 pages, LaTeX, 15 pictures available on request from the Author
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