Freed-Witten anomaly in general flux compactification

Turning on a NS-NS three-form flux in a compact space drives some D-branes to be either Freed-Witten anomalous or unstable to decay into fluxes by the appearance of instantonic branes. By applying T-duality on a toroidal compactification, the NS-flux is transformed into metric fluxes. We propose a T-dual version of the Atiyah-Hirzebruch Spectral Sequence upon which we describe the Freed-Witten anomaly and the brane-flux transition driven by NS and metric fluxes in a twisted torus. The required conditions to cancel the anomaly and the appearance of new instantonic branes are also described. In addition, we give an example in which all D6-branes wrapping Freed-Witten anomaly-free three-cycles in the twisted torus T^6/Z(2)XZ(2) are nevertheless unstable to be transformed into fluxes. Evenmore we find a topological transformation between RR, NS-NS and metric fluxes driven by a chain of instantonic branes.Comment: v3: Shortened version. Examples added. Main results unchange

Technical solutions to prevent heat stress induced crop growth reduction for three climatic regions in Mexico

In the last 15 years a significant increase in greenhouse area has occurred in Mexico, from a modest 50 hectares in 1990 to over 2,000 hectares in 2004. The rapid increase in greenhouse area is a result of an attractive export market, USA. Mexican summer midday temperatures are well above crop optimum and cooling is needed if heat stress induced crop growth reduction is to be prevented. The objective of this study was to determine the effectiveness and feasibility of greenhouse cooling systems for tomato culture under desert, humid tropic and temperate Mexican weather conditions. These climate regions are represented by Mexicali, Merida and Huejutla respectively. The cooling systems included a variety of passive and active systems, which through an engineering design methodology were combined to suit the climate conditions of the 3 regions. The evaluation was conducted via simulation, taking into account the most important temperature effects on crop growth and yield. The results showed that the cooling systems were effective in decreasing heat stress to plants. Investment costs of greenhouse with cooling equipment were under USD 50 m-2 and operational costs were under USD 10 m-2 for all equipment combinations and treatments except for the humid tropic climate of Merida. Solutions for Merida were both economically and physically not feasible due to too high humidity levels. This model study clearly indicates that cooling is feasible in desert and moderate climate regions of Mexico but in humid tropic climate regions feasibility is a problem. Application of design methodology and design evaluation with help of simulation greatly contributed to pointing out effective and non-effective solutions to reduce heat stress in hot climates

The Exchange of Orientifold Two-Planes in M-theory

We propose an M-theory lift picture of the exchange among type IIA orientifold two-planes. This consists in wrapping a M5-brane on a three-cycle in the transverse space of the M-theory orientifold plane OM2. A flux quantization condition for the three-form self-dual field strength, on the worldvolume of the M5-brane is computed. This condition establishes the value which explains the relative charge between two different OM2-planes. Also, we find that the exchange of the four types of orientifold two-planes in string theory, has a common picture in M-theory. Moreover, we find that the assignment of the extra charge is fixed by cohomology and by the flux quantization of the field strength G in M-theory. We conclude that cohomology is sufficient to describe some orientifold properties in M-theory, that at string theory level, only K-theory is able to explain.Comment: 23+1 pages, 6 figures. v2: typos corrected, references adde

Ryanodine receptors

Excitation-contraction coupling involves the faithful conversion of electrical stimuli to mechanical shortening in striated muscle cells, enabled by the ubiquitous second messenger, calcium. Crucial to this process are ryanodine receptors (RyRs), the sentinels of massive intracellular calcium stores contained within the sarcoplasmic reticulum. In response to sarcolemmal depolarization, RyRs release calcium into the cytosol, facilitating mobilization of the myofilaments and enabling cell contraction. In order for the cells to relax, calcium must be rapidly resequestered or extruded from the cytosol. The sustainability of this cycle is crucially dependent upon precise regulation of RyRs by numerous cytosolic metabolites and by proteins within the lumen of the sarcoplasmic reticulum and those directly associated with the receptors in a macromolecular complex. In addition to providing the majority of the calcium necessary for contraction of cardiac and skeletal muscle, RyRs act as molecular switchboards that integrate a multitude of cytosolic signals such as dynamic and steady calcium fluctuations, β-adrenergic stimulation (phosphorylation), nitrosylation and metabolic states, and transduce these signals to the channel pore to release appropriate amounts of calcium. Indeed, dysregulation of calcium release via RyRs is associated with life-threatening diseases in both skeletal and cardiac muscle. In this paper, we briefly review some of the most outstanding structural and functional attributes of RyRs and their mechanism of regulation. Further, we address pathogenic RyR dysfunction implicated in cardiovascular disease and skeletal myopathies

Microplastics in the Antarctic marine system: An emerging area of research

It was thought that the Southern Ocean was relatively free of microplastic contamination; however, recent studies and citizen science projects in the Southern Ocean have reported microplastics in deep-sea sediments and surface waters. Here we reviewed available information on microplastics (including macroplastics as a source of microplastics) in the Southern Ocean. We estimated primary microplastic concentrations from personal care products and laundry, and identified potential sources and routes of transmission into the region. Estimates showed the levels of microplastic pollution released into the region from ships and scientific research stations were likely to be negligible at the scale of the Southern Ocean, but may be significant on a local scale. This was demonstrated by the detection of the first microplastics in shallow benthic sediments close to a number of research stations on King George Island. Furthermore, our predictions of primary microplastic concentrations from local sources were five orders of magnitude lower than levels reported in published sampling surveys (assuming an even dispersal at the ocean surface). Sea surface transfer from lower latitudes may contribute, at an as yet unknown level, to Southern Ocean plastic concentrations. Acknowledging the lack of data describing microplastic origins, concentrations, distribution and impacts in the Southern Ocean, we highlight the urgent need for research, and call for routine, standardised monitoring in the Antarctic marine system

Species Composition and Distribution of Adult Anopheles (Diptera: Culicidae) in Panama

Anopheles (Diptera: Culicidae) species composition and distribution were studied using human landing catch data over a 35-yr period in Panama. Mosquitoes were collected from 77 sites during 228 Þeld trips carried out by members of the National Malaria Eradication Service. Fourteen Anopheles species were identiÞed. The highest average human biting rates were recorded from Anopheles (Nyssorhynchus) albimanus (Wiedemann) (9.8 bites/person/night) andAnopheles (Anopheles) punctimacula (Dyar and Knab) (6.2 bites/person/night). These two species were also the most common, present in 99.1 and 74.9%, respectively, of the sites. Anopheles (Nyssorhynchus) aquasalis (Curry) was encountered mostly in the indigenous Kuna Yala Comarca along the eastern Atlantic coast, where malaria case history and average human biting rate (9.3 bites/person/night) suggest a local role in malaria transmission. An. albimanus, An. punctimacula, and Anopheles (Anopheles) vestitipennis (Dyar and Knab) were more abundant during the rainy season (MayÐDecember), whereas An. aquasalis was more abundant in the dry season (JanuaryÐApril). Other vector species collected in this study were Anopheles (Kerteszia) neivai (Howard, Dyar, and Knab) and Anopheles (Anopheles) pseudopunctipenniss.l. (Theobald). High diversity of Anophelesspecies and six conÞrmed malaria vectors in endemic areas of Panama emphasize the need for more detailed studies to better understand malaria transmission dynamics.Anopheles (Diptera: Culicidae) species composition and distribution were studied using human landing catch data over a 35-yr period in Panama. Mosquitoes were collected from 77 sites during 228 Þeld trips carried out by members of the National Malaria Eradication Service. Fourteen Anopheles species were identiÞed. The highest average human biting rates were recorded from Anopheles (Nyssorhynchus) albimanus (Wiedemann) (9.8 bites/person/night) andAnopheles (Anopheles) punctimacula (Dyar and Knab) (6.2 bites/person/night). These two species were also the most common, present in 99.1 and 74.9%, respectively, of the sites. Anopheles (Nyssorhynchus) aquasalis (Curry) was encountered mostly in the indigenous Kuna Yala Comarca along the eastern Atlantic coast, where malaria case history and average human biting rate (9.3 bites/person/night) suggest a local role in malaria transmission. An. albimanus, An. punctimacula, and Anopheles (Anopheles) vestitipennis (Dyar and Knab) were more abundant during the rainy season (MayÐDecember), whereas An. aquasalis was more abundant in the dry season (JanuaryÐApril). Other vector species collected in this study were Anopheles (Kerteszia) neivai (Howard, Dyar, and Knab) and Anopheles (Anopheles) pseudopunctipenniss.l. (Theobald). High diversity of Anophelesspecies and six conÞrmed malaria vectors in endemic areas of Panama emphasize the need for more detailed studies to better understand malaria transmission dynamics

Interferometry with Photon-Subtracted Thermal Light

We propose and implement a quantum procedure for enhancing the sensitivity with which one can determine the phase shift experienced by a weak light beam possessing thermal statistics in passing through an interferometer. Our procedure entails subtracting exactly one (which can be generalized to m) photons from the light field exiting an interferometer containing a phase-shifting element in one of its arms. As a consequence of the process of photon subtraction, and somewhat surprisingly, the mean photon number and signal-to-noise ratio of the resulting light field are thereby increased, leading to enhanced interferometry. This method can be used to increase measurement sensitivity in a variety of practical applications, including that of forming the image of an object illuminated only by weak thermal light