Atmospheric mass loss by stellar wind from planets around main sequence M stars

We present an analytic model for the interaction between planetary atmospheres and stellar winds from main sequence M stars, with the purpose of obtaining a quick test-model that estimates the timescale for total atmospheric mass loss due to this interaction. Planets in the habitable zone of M dwarfs may be tidally locked and may have weak magnetic fields, because of this we consider the extreme case of planets with no magnetic field. The model gives the planetary atmosphere mass loss rate as a function of the stellar wind and planetary properties (mass, atmospheric pressure and orbital distance) and an entrainment efficiency coefficient $\alpha$. We use a mixing layer model to explore two different cases: a time-independent stellar mass loss and a stellar mass loss rate that decreases with time. For both cases we consider planetary masses within the range of $1\to10$ M$_{\oplus}$ and atmospheric pressures with values of 1, 5 and 10 atm. For the time dependent case, planets without magnetic field in the habitable zone of M dwarfs with initial stellar mass losses of $\leq \dot{M}_{w} < 10^{-11}$ M$_{\odot}$ yr$^{-1}$, may retain their atmospheres for at least 1 Gyr. This case may be applied to early spectral type M dwarfs (earlier than M5). Studies have shown that late type M dwarfs (later than M5) may be active for long periods of time ($\geq 4$Gyr), and because of that our model with constant stellar mass loss rate may be more accurate. For these stars most planets may have lost their atmospheres in 1 Gyr or less because most of the late type M dwarfs are expected to be active. We emphasize that our model only considers planets without magnetic fields. Clearly we must expect a higher resistance to atmospheric erosion if we include the presence of a magnetic field.Comment: Icarus, submitted. 18 pages, 6 figure

One Thousand and One Bubbles

We propose a novel strategy that permits the construction of completely general five-dimensional microstate geometries on a Gibbons-Hawking space. Our scheme is based on two steps. First, we rewrite the bubble equations as a system of linear equations that can be easily solved. Second, we conjecture that the presence or absence of closed timelike curves in the solution can be detected through the evaluation of an algebraic relation. The construction we propose is systematic and covers the whole space of parameters, so it can be applied to find all five-dimensional BPS microstate geometries on a Gibbons-Hawking base. As a first result of this approach, we find that the spectrum of scaling solutions becomes much larger when non-Abelian fields are present. We use our method to describe several smooth horizonless multicenter solutions with the asymptotic charges of three-charge (Abelian and non-Abelian) black holes. In particular, we describe solutions with the centers lying on lines and circles that can be specified with exact precision. We show the power of our method by explicitly constructing a 50-center solution. Moreover, we use it to find the first smooth five-dimensional microstate geometries with arbitrarily small angular momentum.Comment: 33 pages. v2: typos correcte

An integrative approach for modeling and simulation of Heterocyst pattern formation in Cyanobacteria strands

A comprehensive approach to cellular differentiation in cyanobacteria is developed. To this aim, the process of heterocyst cell formation is studied under a systems biology point of view. By relying on statistical physics techniques, we translate the essential ingredients and mechanisms of the genetic circuit into a set of differential equations that describes the continuous time evolution of combined nitrogen, PatS, HetR and NtcA concentrations. The detailed analysis of these equations gives insight into the single cell dynamics. On the other hand, the inclusion of diffusion and noisy conditions allows simulating the formation of heterocysts patterns in cyanobacteria strains. The time evolution of relevant component concentrations are calculated allowing for a comparison with experiments. Finally, we discuss the validity and the possible improvements of the model.Comment: 20 pages (including the supporting information), 8 figure

Kinetic Modeling of the Atmospheric Photooxidation of Reduced Sulfur and Nitrogen Compounds

Atmospheric aerosols encapsulate a wide variety of particles with different compositions, sizes and sources of origin. They also directly and indirectly affect climate by their interactions with sunlight, clouds, atmospheric chemical species, and even other suspended particles. To understand the atmospheric aerosol processes and the effects they have in global and regional climate is of utmost importance for the future establishment of environmental regulations and emission policies that affect aerosol precursor compounds in an effective and beneficial manner. In particular, aerosols are known to be formed from emissions from human activities, such as fossil fuel burning, agriculture, or concentrated animal feeding operations (CAFOs). Secondary organic aerosols (SOA) constitute a type of atmospheric aerosols that are formed from the atmospheric oxidation of organic compounds that are released from various sources into the atmosphere. Due to the complexity of the atmosphere and variability of its conditions, the direct study of SOA formation is a challenging task, but the implementation of atmospheric chamber facilities to study aerosol formation and growth under controlled conditions has provided a way to study the formation and growth of SOA. However, chamber experiments cannot study specific reactions or individual compounds from the aerosol formation mechanisms in isolation, they can only provide insight on what is produced and what it is produced from, and under what conditions. Thus, kinetic modeling of the mechanisms of gas-phase atmospheric oxidation of the compounds of interest is used to develop reliable and accurate chemical models that will help have precise estimations and determine the mechanisms by which volatile organic compounds interact to produce aerosol particles. Dimethyl sulfide (DMS), dimethyl disulfide (DMDS) and trimethylamine (TMA) are three relevant atmospheric compounds, due to their emissions from many natural and anthropogenic sources and recent studies on emissions of these compounds from animal waste from CAFOs has triggered the interests on the study of SOA formation from these and other similar compounds. In this study, kinetic modeling of the atmospheric oxidation mechanisms of DMDS, DMS and TMA is used to simulate atmospheric chamber studies of aerosol formation to develop accurate models and help determine the mechanisms of aerosol formation

Elementary Principalas Technology Leadership Dispositions

This qualitative study examined the reported technology dispositions that a group of elementary principals in a South Texas public school district possess as technology leaders as aligned to the 2009 National Technology Standards for Administrators NETS-A An online questionnaire and open-ended audio recorded interviews were utilized to determine technology dispositions of the participants Findings included the following five dispositions 1 Technology s usefulness 2 Risk taking 3 Self-reliance 4 Encouragement and 5 Role mode

Using the Jigsaw Method for Meaningful Learning to Enhance Learning and Rentention in an Educational Leadership Graduate School Course

This qualitative case study examined factors that were both successful and unsuccessful along with the attitudes and preferences of educational leadership graduate students towards working in an online cooperative jigsaw blog project in which each student had an active role for each topic addressed throughout the semester The theoretical framework for this study was based on the work of Novak 2011 and Ausubel 1960 Their theories explore how the learner processes large amounts of meaningful material from verbal and textual formats in classroom settings Analysis of the online questionnaire and face-to-face interview data indicated that the graduate students enrolled in the course effectively learn when they are learning collaboratively in smaller chunks of information at a time as subject matter experts and have an ease of access to the learning materials Students also preferred non-traditional methods over traditional lectures and become more involved when they participate in the evaluation of their peers Results also revealed that students disliked learning using the jigsaw method when there were missing pieces to the blog postings a lack of quality in the postings a lack of accuracy a repetition of information in the blog and a lack of peer and instructor feedbac

A monitoring system for a LoRa mesh network

El internet de las cosas (IoT) ha sido una tecnología en alza en los últimos años. A medida que pasa el tiempo, los pequeños aparatos se han convertido en potentes dispositivos capaces de cálculos más complejos. De entre todas estas tecnologías, particularmente una se ha puesto bastante de moda dentro del campo, las placas LoRa perfectas para establecer redes LPWAN (Low Power Wide Area Network). El Doctor Roger Pueyo Centelles diseñó un protocolo para redes mesh basado en LoRa, y el ingeniero Sergi Miralles realizó una primera aproximación de su implementación en c++. Posteriormente el ingeniero Joan Miquel Solé completó una versión estable del mismo. Ahora necesitamos saber más del comportamiento de este protocolo sobre el campo. En este TFG hemos creado un sistema completo de monitorización que nos ayudará en el futuro a realizar diversos análisis y experimentos adicionales con mucho menos esfuerzo.The internet of things(IoT) has been a pushing technology in the last years. As time goes by, the little devices have become more powerful and capable of doing more complex calculus. Among all these technologies one particularly has be- come quite mainstream in the field, these are the LoRa devices suitable to build low power wide area network (LPWAN). Phd. Roger Pueyo Centelles designed a protocol for LoRa mesh networks, and the Bachelor Sergi Miralles build a first approach of the protocol, afterwards Joan Miquel Solé made a stable version of it. Now we need to know more about the behaviour of this protocol over the field. In this Bachelor Thesis we created a whole monitoring system that will help us in the future doing analysis of a lot of experimental research with less effor

DIA: A complexity-effective decoding architecture

Fast instruction decoding is a true challenge for the design of CISC microprocessors implementing variable-length instructions. A well-known solution to overcome this problem is caching decoded instructions in a hardware buffer. Fetching already decoded instructions avoids the need for decoding them again, improving processor performance. However, introducing such special--purpose storage in the processor design involves an important increase in the fetch architecture complexity. In this paper, we propose a novel decoding architecture that reduces the fetch engine implementation cost. Instead of using a special-purpose hardware buffer, our proposal stores frequently decoded instructions in the memory hierarchy. The address where the decoded instructions are stored is kept in the branch prediction mechanism, enabling it to guide our decoding architecture. This makes it possible for the processor front end to fetch already decoded instructions from the memory instead of the original nondecoded instructions. Our results show that using our decoding architecture, a state-of-the-art superscalar processor achieves competitive performance improvements, while requiring less chip area and energy consumption in the fetch architecture than a hardware code caching mechanism.Peer ReviewedPostprint (published version