229 research outputs found
The Influence of Immediate Urban Surroundings on Energy Performance of Historical Buildings
High-density urban areas contain large number of historical buildings whose structures and artistic values are protected by regulations. This restricts the improvements can be made to building envelope to reduce energy demand of historical buildings. Therefore, immediate urban surroundings (IUS) may play a central role on energy performance of historical buildings (EPHB). Yet, literature has provided little or no evidence, so far. To address the gap, the current experimental inquiry aims to test the significance of IUS’s influence on the EPHB. To achieve, historical structure in hothumid climate was selected and surveyed thoroughly. Control and intervention cases were considered to measure the influence IUS. The control case corresponds to the former state of IUS; whereas the intervention described as the IUS which includes a recently built office block with reflective glass façade. The numerical result obtained from computational thermal simulations were used for comparison. Accordingly, the increase in heating demand substantially surpassed the decrease in cooling demand for the case under study. Therefore, a significant increase in total energy demand was observed in the presence of intervention. In addition, the energy performance of the individual volumes located in the lower floors presented higher fluctuations due to intervention’s shading effect
Nitrogen and sulfur deprivation differentiate lipid accumulation targets of Chlamydomonas reinhardtii
Cataloged from PDF version of article.Nitrogen (N) and sulfur (S) have inter-related and distinct impacts on microalgal metabolism; with N starvation having previously been reported to induce elevated levels of the biodiesel feedstock material triacylglycerol (TAG), while S deprivation is extensively studied for its effects on biohydrogen production in microalgae.1,2 We have previously demonstrated that N- and S-starved cells of Chlamydomonas reinhardtii display different metabolic trends, suggesting that different response mechanisms exist to compensate for the absence of those two elements.3 We used C. reinhardtii CC-124 mt(-) and CC-125 mt(+) strains to test possible metabolic changes related to TAG accumulation in response to N and S deprivation, considering that gamete differentiation in this organism is mainly regulated by N.4 Our findings contribute to the understanding of microalgal response to element deprivation and potential use of element deprivation for biodiesel feedstock production using microalgae, but much remains to be elucidated on the precise contribution of both N and S starvation on microalgal metabolism. © 2012 Landes Bioscience
On the BPS Spectrum at the Root of the Higgs Branch
We study the BPS spectrum and walls of marginal stability of the
supersymmetric theory in four dimensions with gauge group SU(n)
and fundamental flavours at the root of the Higgs branch. The
strong-coupling spectrum of this theory was conjectured in hep-th/9902134 to
coincide with that of the two-dimensional supersymmetric
sigma model. Using the Kontsevich--Soibelman
wall-crossing formula, we start with the conjectured strong-coupling spectrum
and extrapolate it to all other regions of the moduli space. In the
weak-coupling regime, our results precisely agree with the semiclassical
analysis of hep-th/9902134: in addition to the usual dyons, quarks, and
bosons, if the complex masses obey a particular inequality, the resulting
weak-coupling spectrum includes a tower of bound states consisting of a dyon
and one or more quarks. In the special case of -symmetric
masses, there are bound states with one quark for odd and no bound states
for even .Comment: 11 pages, 4 figure
The General Supersymmetric Solution of Topologically Massive Supergravity
We find the general fully non-linear solution of topologically massive
supergravity admitting a Killing spinor. It is of plane-wave type, with a null
Killing vector field. Conversely, we show that all solutions with a null
Killing vector are supersymmetric for one or the other choice of sign for the
Chern-Simons coupling constant \mu. If \mu does not take the critical value
\mu=\pm 1, these solutions are asymptotically regular on a Poincar\'e patch,
but do not admit a smooth global compactification with boundary S^1\times\R. In
the critical case, the solutions have a logarithmic singularity on the boundary
of the Poincar\'e patch. We derive a Nester-Witten identity, which allows us to
identify the associated charges, but we conclude that the presence of the
Chern-Simons term prevents us from making a statement about their positivity.
The Nester-Witten procedure is applied to the BTZ black hole.Comment: Minor correction
Effects of laser ablated silver nanoparticles on Lemna minor
Cataloged from PDF version of article.The present study investigates and models the effect of laser ablated silver nanoparticles (AgNPs) on the development of the aquatic macrophyte Lemna minor. Toxic effects of five different AgNP concentrations (8, 16, 32, 96 and 128μgL-1) on L. minor were recorded over seven days under simulated natural conditions. Biosorption of AgNPs by L. minor was modeled using four sorption isotherms, and the sorption behavior was found to agree most closely with the Langmuir-Freundlich model (R2=0.997). While toxic effects of AgNPs could be observed in all models and concentrations, the greatest increase in toxicity was in the 8-32μgL-1 range. Dry weight- and frond number-based inhibition experiments suggest that growth inhibition does not necessarily scale with AgNP concentration, and that slight fluctuations in inhibition rates exist over certain concentration ranges. Very close fits (R2=0.999) were obtained for all removal models, suggesting that the fluctuations are not caused by experimental variation. In addition, L. minor was found to be a successful bioremediation agent for AgNPs, and displayed higher removal rates for increasing AgNP doses. FT-IR spectroscopy suggests that carbonyl groups are involved in AgNP remediation. © 2014 Elsevier Ltd
Mitigating housing market shocks: an agent-based reinforcement learning approach with implications for real-time decision support
Research in modelling housing market dynamics using agent-based models (ABMs) has grown due to the rise of accessible individual-level data. This research involves forecasting house prices, analysing urban regeneration, and the impact of economic shocks. There is a trend towards using machine learning (ML) algorithms to enhance ABM decision-making frameworks. This study investigates exogenous shocks to the UK housing market and integrates reinforcement learning (RL) to adapt housing market dynamics in an ABM. Results show agents can learn real-time trends and make decisions to manage shocks, achieving goals like adjusting the median house price without pre-determined rules. This model is transferable to other housing markets with similar complexities. The RL agent adjusts mortgage interest rates based on market conditions. Importantly, our model shows how a central bank agent learned conservative behaviours in sensitive scenarios, aligning with a 2009 study, demonstrating emergent behavioural patterns
Bending AdS Waves with New Massive Gravity
We study AdS-waves in the three-dimensional new theory of massive gravity
recently proposed by Bergshoeff, Hohm, and Townsend. The general configuration
of this type is derived and shown to exhibit different branches, with different
asymptotic behaviors. In particular, for the special fine tuning
, solutions with logarithmic fall-off arise, while in the
range , spacetimes with Schrodinger isometry group are admitted
as solutions. Solutions that are asymptotically AdS, both for
Brown-Henneaux and for the weakened boundary conditions, are also identified.
The metric function that characterizes the profile of the AdS-wave behaves as a
massive excitation on the spacetime, with an effective mass given by
. For the critical value , the value of
the effective mass precisely saturates the Breitenlohner-Freedman bound for the
AdS space where the wave is propagating on. The analogies with the AdS-wave
solutions of topologically massive gravity are also discussed. Besides, we
consider the coupling of both massive deformations to Einstein gravity and find
the exact configurations for the complete theory, discussing all the different
branches exhaustively. One of the effects of introducing the Chern-Simons
gravitational term is that of breaking the degeneracy in the effective mass of
the generic modes of pure New Massive Gravity, producing a fine structure due
to parity violation. Another effect is that the zoo of exact logarithmic
specimens becomes considerably enlarged.Comment: 9 pages. Minor typos correcte
A Study of Wall-Crossing: Flavored Kinks in D=2 QED
We study spectrum of D=2 N=(2,2) QED with N+1 massive charged chiral
multiplets, with care given to precise supermultiplet countings. In the
infrared the theory flows to CP^N model with twisted masses, where we construct
generic flavored kink solitons for the large mass regime, and study their
quantum degeneracies. These kinks are qualitatively different and far more
numerous than those of small mass regime, with features reminiscent of
multi-pronged (p,q) string web, complete with the wall-crossing behavior. It
has been also conjectured that spectrum of this theory is equivalent to the
hypermultiplet spectrum of a certain D=4 Seiberg-Witten theory. We find that
the correspondence actually extends beyond hypermultiplets in D=4, and that
many of the relevant indices match. However, a D=2 BPS state is typically
mapped to several different kind of dyons whose individual supermultiplets are
rather complicated; the match of index comes about only after summing over
indices of these different dyons. We note general wall-crossing behavior of
flavored BPS kink states, and compare it to those of D=4 dyons.Comment: 47 pages, 5 figures; typos fixed; references adde
Three-dimensional black holes, gravitational solitons, kinks and wormholes for BHT massive gravity
The theory of massive gravity in three dimensions recently proposed by
Bergshoeff, Hohm and Townsend (BHT) is considered. At the special case when the
theory admits a unique maximally symmetric solution, a conformally flat space
that contains black holes and gravitational solitons for any value of the
cosmological constant is found. For negative cosmological constant, the black
hole is characterized in terms of the mass and the "gravitational hair"
parameter, providing a lower bound for the mass. For negative mass parameter,
the black hole acquires an inner horizon, and the entropy vanishes at the
extremal case. Gravitational solitons and kinks, being regular everywhere, are
obtained from a double Wick rotation of the black hole. A wormhole solution in
vacuum that interpolates between two static universes of negative spatial
curvature is obtained as a limiting case of the gravitational soliton with a
suitable identification. The black hole and the gravitational soliton fit
within a set of relaxed asymptotically AdS conditions as compared with the ones
of Brown and Henneaux. In the case of positive cosmological constant the black
hole possesses an event and a cosmological horizon, whose mass is bounded from
above. Remarkably, the temperatures of the event and the cosmological horizons
coincide, and at the extremal case one obtains the analogue of the Nariai
solution, . A gravitational soliton is also obtained
through a double Wick rotation of the black hole. The Euclidean continuation of
these solutions describes instantons with vanishing Euclidean action. For
vanishing cosmological constant the black hole and the gravitational soliton
are asymptotically locally flat spacetimes. The rotating solutions can be
obtained by boosting the previous ones in the plane.Comment: Talk given at the "Workshop on Gravity in Three Dimensions," 14-24
April 2009, ESI, Vienna. 30 pages, 6 figures. V2: minor changes and section 6
slightly improved. Last version for JHE
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