531 research outputs found
Responding to chromosomal breakage during M-phase: insights from a cell-free system
DNA double strand breaks (DSBs) activate ATM and ATR dependent checkpoints that prevent the onset of mitosis. However, how cells react to DSBs occurring when they are already in mitosis is poorly understood. The Xenopus egg extract has been utilized to study cell cycle progression and DNA damage checkpoints. Recently this system has been successfully used to uncover an ATM and ATR dependent checkpoint affecting centrosome driven spindle assembly. These studies have led to the identification of XCEP63 as major target of this pathway. XCEP63 is a coiled-coil rich protein localized at centrosome essential for proper spindle assembly. ATM and ATR directly phosphorylate XCEP63 on serine 560 inducing its delocalization from centrosome, which in turn delays spindle assembly. This pathway might contribute to regulate DNA repair or mitotic cell survival in the presence of chromosome breakage
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Indoor thermal environments in Chinese residential buildings responding to the diversity of climates
China has a diversity of climates and a unique historic national heating policy which greatly affects indoor thermal environment and the occupantsâ thermal response. This paper quantitatively analyzes the data from a large-scale field study across the country conducted from 2008 to 2011 in residential buildings. The study covers nine typical cities located in the five climate zones including Severe Cold (SC), Cold (C), Hot Summer and Cold Winter (HSCW), Hot Summer and Warm Winter (HSWW) and Mild (M) zones. It is revealed that there exists a large regional discrepancy in indoor thermal environ- ment, the worst performing region being the HSCW zone. Humanâs long-term climate adaptation leads to wider range of acceptable thermal comfort temperature. Different graphic comfort zones with accept- able range of temperature and humidity for the five climate zones are obtained using the adaptive Predictive Mean Vote (aPMV) model. The results show that occupants living in the poorer thermal environments in the HSCW and HSWW zones are more adaptive and tolerant to poor indoor conditions than those living in the north part of China where central heating systems are in use. It is therefore recommended to develop regional evaluation standards of thermal environments responding to climate characteristics as well as local occupantsâ acclimatization and adaptation in order to meeting dual targets of energy conservation and indoor thermal environment improvement
Structure of human Cdc45 and implications for CMG helicase function.
Cell division cycle protein 45 (Cdc45) is required for DNA synthesis during genome duplication, as a component of the Cdc45-MCM-GINS (CMG) helicase. Despite its essential biological function, its biochemical role in DNA replication has remained elusive. Here we report the 2.1-Ă
crystal structure of human Cdc45, which confirms its evolutionary link with the bacterial RecJ nuclease and reveals several unexpected features that underpin its function in eukaryotic DNA replication. These include a long-range interaction between N- and C-terminal DHH domains, blocking access to the DNA-binding groove of its RecJ-like fold, and a helical insertion in its N-terminal DHH domain, which appears poised for replisome interactions. In combination with available electron microscopy data, we validate by mutational analysis the mechanism of Cdc45 association with the MCM ring and GINS co-activator, critical for CMG assembly. These findings provide an indispensable molecular basis to rationalize the essential role of Cdc45 in genomic duplication.We would like to thank Ben Luisi for help with X-ray data collection, Alessandro Costa for sharing the cryoEM data of the CMG complex before publication and Joseph Maman for help with the analysis of Cdc45-DNA interactions. This work was supported by a Wellcome Trust Senior Investigator award to LP (104641/Z/14/Z) and a Cambridge Gates PhD scholarship to ACS. VC is funded by the Associazione Italiana per Ricerca sul Cancro (AIRC), the European Research Council (ERC) consolidator grant (614541), the Association for International Cancer Research (AICR), the Giovanni-Armenise award to VC, the Epigen Progetto Bandiera and the Fondazione Telethon.This is the final version of the article. It first appeared from Nature via https://doi.org/10.1038/ncomms1163
A review of daylighting strategies in schools: state of the art and expected future trends
The study of daylight conditions within educational buildings has been a topic of interest
since the nineteenth century in western countries, and European ones in particular. Although it has
been argued that providing a view outsideâor even using daylight instead of more stable and
manageable artificial lightâcould reduce studentsâ performance without providing a pleasant and
healthy environment, nowadays it seems that a large consensus upon the need to design well daylit
spaces is being reached. This paper reviews how the research community has tackled the task of
understanding and solving the complex relationships amongst local climate, usersâ needs and
design constraints in school buildings by showing the different approaches used and technological
solutions suggested. The reported case studies, based either on experimental measurements or on
simulations, highlight the need of a comprehensive approach to the topic to fully understand the
nonâtrivial requirements of a daylit educational environment
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Stressing the passive behavior of a Passivhaus: an evidence-based scenario analysis for a Mediterranean case study
This paper first reports the outcomes of a one-year measurement
campaign of a passive house built in the Mediterranean climate of Cesena
(Italy) in terms of thermal comfort parameters temperature and relative
humidity and Indoor Environmental Quality (IEQ) parameter CO2
concentrations. The design carried out with the help of the steady state
Passive House Planning Package (PHPP) was able to guarantee good comfort
conditions during the heating period, but on the other hand, overheating
occurrences during the cooling season have been recorded for almost 50%
time according to EN 15251 Standard. Further analyses conducted with the
help of dynamic simulations in EnergyPlus allowed identifying the
insulation levels and ventilation mode as the key design factors to
change in order to reduce overheating to less than 20% of time while
keeping a comfortable indoor environment in winter.
The simplifications that can be made by reducing the insulation material
thickness (up to a third of the original value) on the roof and on the
walls, replacing triple-glazed windows with double-glazed windows and
implementing a hybrid ventilation strategy instead of using Mechanical
Ventilation with Heat Recovery (MVHR) alone could also lead to economic
savings. These savings, due to both lower construction costs and
operational energy savings, amount to 8755 euros in terms of Net Present
Value (NPV) over 30 years' time.
The Passivhaus Standard can still be regarded as a good reference for
designing low-energy and comfortable houses in a Mediterranean climate if
some simplifications are made according to detailed building performance
simulations
A Macroscopic Mathematical Model For Cell Migration Assays Using A Real-Time Cell Analysis
Experiments of cell migration and chemotaxis assays have been classically
performed in the so-called Boyden Chambers. A recent technology, xCELLigence
Real Time Cell Analysis, is now allowing to monitor the cell migration in real
time. This technology measures impedance changes caused by the gradual increase
of electrode surface occupation by cells during the course of time and provide
a Cell Index which is proportional to cellular morphology, spreading, ruffling
and adhesion quality as well as cell number. In this paper we propose a
macroscopic mathematical model, based on \emph{advection-reaction-diffusion}
partial differential equations, describing the cell migration assay using the
real-time technology. We carried out numerical simulations to compare simulated
model dynamics with data of observed biological experiments on three different
cell lines and in two experimental settings: absence of chemotactic signals
(basal migration) and presence of a chemoattractant. Overall we conclude that
our minimal mathematical model is able to describe the phenomenon in the real
time scale and numerical results show a good agreement with the experimental
evidences
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Refurbishing an existing apartment block in Mediterranean climate: towards the Passivhaus standard
The Passivhaus standard, although widely appreciated in cold regions, is seldom regarded as a reference in the energy renovation of existing buildings in warm countries. This paper evaluates the effectiveness of a series of strategies for the energy refurbishment of an existing apartment block in Southern Italy, based on dynamic energy simulations. The paper aims to show
that, in warm Mediterranean areas, a building refurbishment must not be oriented towards an excessive insulation level. Conversely, if aimed to comply with the Passivhaus standard, the renovation must look above all at those strategies that mitigate
the energy needs for space cooling and improve thermal comfort in summer
In vivo evaluation of renal function using intravital multiphoton microscopy on rats and mice with induced or spontaneous renal injury
Multiphoton microscopy is a powerful tool for the in vivo imaging of renal processes thanks to the improved tissue penetration and the high spatial and temporal resolution. Intravital imaging permits to evaluate dynamic processes and pathophysiological parameters in real time using non-invasive methods. This project aims to use existing multiphoton microscopy approaches to evaluate in vivo many renal parameters in our animal models and, at the same time, to develop an original application for the assessment of single nephron glomerular filtration rate. In addition, a method for detection and quantification of renal fibrosis ex vivo was developed coupling multiphoton microscopy and machine learning-based segmentation software.
The linescan-based innovative methodology offered a great improvement in terms of temporal resolution and provided reliable values of single nephron glomerular filtration rate comparable with previous methods. The validation of this approach was carried out measuring renal filtration in low-dose dopamine and ischemic treated rats, which showed significantly higher and lower values of single nephron glomerular filtration rate, respectively, compared to the control group.
The dynamic process of renal glucose reabsorption was elucidated in GLUT2 cKO mice mimicking the Fanconi Bickel Syndrome. Intravital multiphoton microscopy of the renal tubules after the continuous infusion of fluorescent 2-NBDG demonstrated an impaired utilization of glucose in these mice compared to the control.
We also developed a novel approach based on second harmonic generation tool provided by the multiphoton microscopy and a machine learning-based segmentation software to detect and quantify renal fibrosis in kidney slices.
These multiphoton applications highlighted the great potential of intravital microscopy to elucidate in real time the mechanisms involved in renal pathophysiology at cellular and subcellular resolutio
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Study on the application of cool paintings for the passive cooling of existing buildings in Mediterranean climates
Building roofs play a very important role in the energy balance of buildings, especially in summer, when they are hit by a rather high solar irradiance. Depending on the type of finishing layer, roofs can absorb a great amount of heat and reach quite high temperatures on their outermost surface, which determines significant room overheating. However, the use of highly reflective cool materials can help to maintain low outer surface temperatures; this practice may improve indoor thermal comfort and reduce the
cooling energy need during the hot season.This technology is currently well known and widely used in the USA, while receiving
increasing attention in Europe. In order to investigate the effectiveness of cool roofs as a passive strategy for passive cooling in moderately hot climates, this paper presents the numerical results of a case study based on the dynamic thermal analysis of an existing office building in Catania (southern Italy, Mediterranean area). The results show how the application of a cool paint on
the roof can enhance the thermal comfort of the occupants by reducing the operative temperatures of the rooms and to reduce the overall energy needs of the building for space heating and cooling
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Establishment and verification of solar radiation calculation model of glass daylighting roof in hot summer and warm winter zone in China
In this paper, solar heat gain through glass daylighting roof is deeply studied by theoretical calculation method, taking Guangzhou in the Hot Summer and Warm Winter (HSWW) zone as an example. The direct solar radiation is calculated by Bouguer formula whereas the diffuse solar radiation is calculated by Berlage formula, representing the basis for the calculation method of the solar radiation intensity through the glass daylighting roof. Through the establishment of solar radiation calculation
model, the solar heat gain of the commonly used glass types has been calculated and analyzed, especially comparatively analyzing of Low-E cored-glass with double-coated silver and 6+12A+6 insulating glass. Then, comparison between solar heat
gain as calculated and measured by field measurement tested the indoor solar radiation heat gain distribution by using adjacent rooms with different glass types in a hot summer area, with the aim of demonstrating the effectiveness of the model. The research in this paper is expected to further improve the calculation accuracy of both thermal load and indoor temperature
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