Capsicum species have been the object of different studies (Dorantes et al., 2000; Careaga et al.... more Capsicum species have been the object of different studies (Dorantes et al., 2000; Careaga et al., 2003; Acero-Ortega et al., 2005) in order to determine their antimicrobial activity, the compounds that would be responsible for it, and the microorganisms that could be affected by it, finding that Staphylococcus aureus, Salmonella tiphymurium, Listeria monocytogenes, Pseudomonas aureaginosa and Bacillus cereus are susceptible to inhibition by Capsicum extracts. Some of the active compounds responsible for the inhibitory action are t-cinnamic acid and its derivatives, which are intermediate compounds in phenylpropanoids pathway. Capsicum annuum oleoresins are “generally recognized as safe” (GRAS) by the FDA, and so their use as natural antimicrobials is safe. However, it is important to know through predictive microbiology and modeling the quantitative effect of the Capsicum extracts, the active compounds, and the interactions with other factors such as pH and temperature. One of the food products that has been involved in outbreaks is fresh rennetcurdled cheese, which has a rich nutrient content, a high water activity and low acidity, which make it an adequate culture medium for the growth of a wide variety of bacteria. Some of these bacteria are known to cause food-borne illness, such as Staphylococcus aureus. It has been estimated that consumption of foods contaminated by this microorganism is responsible for 185,060 illnesses, 1,753 hospitalizations and two deaths per year in the United States. In the United Kingdom since 1980, numbers of reported cases have not exceeded 189 per year, although this is only a small percentage of actual cases (Sutherland and Varnam, 2002). S. aureus has also been involved in food-borne diseases in México, especially in the consumption of milk products. Staphylococcal enterointoxication (staphylococcal food poisoning) results from the ingestion of enterotoxins that are synthesized during growth of S. aureus in foods. S. aureus is capable of producing an enterotoxin in conditions such as: water activity >0.85, a range of pH between 4 to 9.8, temperatures from 10 to 48 °C and a good nutrient supply such as that provided by fresh cheese and other milk products (Halpin-Dohnalek and Marth, 1989).
Capsicum species have been the object of different studies (Dorantes et al., 2000; Careaga et al.... more Capsicum species have been the object of different studies (Dorantes et al., 2000; Careaga et al., 2003; Acero-Ortega et al., 2005) in order to determine their antimicrobial activity, the compounds that would be responsible for it, and the microorganisms that could be affected by it, finding that Staphylococcus aureus, Salmonella tiphymurium, Listeria monocytogenes, Pseudomonas aureaginosa and Bacillus cereus are susceptible to inhibition by Capsicum extracts. Some of the active compounds responsible for the inhibitory action are t-cinnamic acid and its derivatives, which are intermediate compounds in phenylpropanoids pathway. Capsicum annuum oleoresins are “generally recognized as safe” (GRAS) by the FDA, and so their use as natural antimicrobials is safe. However, it is important to know through predictive microbiology and modeling the quantitative effect of the Capsicum extracts, the active compounds, and the interactions with other factors such as pH and temperature. One of the food products that has been involved in outbreaks is fresh rennetcurdled cheese, which has a rich nutrient content, a high water activity and low acidity, which make it an adequate culture medium for the growth of a wide variety of bacteria. Some of these bacteria are known to cause food-borne illness, such as Staphylococcus aureus. It has been estimated that consumption of foods contaminated by this microorganism is responsible for 185,060 illnesses, 1,753 hospitalizations and two deaths per year in the United States. In the United Kingdom since 1980, numbers of reported cases have not exceeded 189 per year, although this is only a small percentage of actual cases (Sutherland and Varnam, 2002). S. aureus has also been involved in food-borne diseases in México, especially in the consumption of milk products. Staphylococcal enterointoxication (staphylococcal food poisoning) results from the ingestion of enterotoxins that are synthesized during growth of S. aureus in foods. S. aureus is capable of producing an enterotoxin in conditions such as: water activity >0.85, a range of pH between 4 to 9.8, temperatures from 10 to 48 °C and a good nutrient supply such as that provided by fresh cheese and other milk products (Halpin-Dohnalek and Marth, 1989).
Protoplanetary disks are composed primarily of gas (99% of the mass). Nevertheless, relatively fe... more Protoplanetary disks are composed primarily of gas (99% of the mass). Nevertheless, relatively few observational constraints exist for the gas in disks. In this review, I discuss several observational diagnostics in the UV, optical, near-IR, mid-IR, and (sub)-mm wavelengths that have been employed to study the gas in the disks of young stellar objects. I concentrate in diagnostics that probe the inner 20 AU of the disk, the region where planets are expected to form. I discuss the potential and limitations of each gas tracer and present prospects for future research.
FU Orionis objects (FUors) play a central role in the study of the evolution of young stars. They... more FU Orionis objects (FUors) play a central role in the study of the evolution of young stars. They undergo accretion outbursts that can bring up to about 0.01 solar masses per outburst, therefore providing a significant amount of mass in the pre-main sequence life of a star. Spitzer IRS observations of FUors have shown either silicate features in absorption and ice bands or silicates in emission with no ice bands. This led some authors to propose an evolutionary paradigm in which the former FUors are younger than the latter FUors. The FUor phase might be a common but rarely observed phase (about 20 FUors known) of most young low-mass stars and might be the link between Class I and Class II sources. So far, Spitzer has obtained IRS spectra of about half of the FUor catalog, focusing on its most famous class members. With this short Spitzer proposal, we aim to observe FUors that have not yet been observed with the IRS or had no high-resolution module spectra. We will study the composition and evolution of dust grains and of ices in FUors surrounded by envelopes, and we aim at detecting faint molecular hydrogen and atomic lines with the high-resolution module spectra. The IRS spectra will probe the stellar environment, and thus test the above evolutionary paradigm and the different theories for the origin of FUor outburst. The Spitzer IRS observations of our sample of FUors will therefore provide additional insights about a significant phase in the life of young stars with the aim to better describe the evolutionary sequence from Class I star to Class II sources.
La gran mayoría de los metales son policristalinos, es decir, formados por cristales, y a cada cr... more La gran mayoría de los metales son policristalinos, es decir, formados por cristales, y a cada cristal se le denomina grano. Se busca también explicar la relación entre el grano y las propiedades de los metales.
Capsicum species have been the object of different studies (Dorantes et al., 2000; Careaga et al.... more Capsicum species have been the object of different studies (Dorantes et al., 2000; Careaga et al., 2003; Acero-Ortega et al., 2005) in order to determine their antimicrobial activity, the compounds that would be responsible for it, and the microorganisms that could be affected by it, finding that Staphylococcus aureus, Salmonella tiphymurium, Listeria monocytogenes, Pseudomonas aureaginosa and Bacillus cereus are susceptible to inhibition by Capsicum extracts. Some of the active compounds responsible for the inhibitory action are t-cinnamic acid and its derivatives, which are intermediate compounds in phenylpropanoids pathway. Capsicum annuum oleoresins are “generally recognized as safe” (GRAS) by the FDA, and so their use as natural antimicrobials is safe. However, it is important to know through predictive microbiology and modeling the quantitative effect of the Capsicum extracts, the active compounds, and the interactions with other factors such as pH and temperature. One of the food products that has been involved in outbreaks is fresh rennetcurdled cheese, which has a rich nutrient content, a high water activity and low acidity, which make it an adequate culture medium for the growth of a wide variety of bacteria. Some of these bacteria are known to cause food-borne illness, such as Staphylococcus aureus. It has been estimated that consumption of foods contaminated by this microorganism is responsible for 185,060 illnesses, 1,753 hospitalizations and two deaths per year in the United States. In the United Kingdom since 1980, numbers of reported cases have not exceeded 189 per year, although this is only a small percentage of actual cases (Sutherland and Varnam, 2002). S. aureus has also been involved in food-borne diseases in México, especially in the consumption of milk products. Staphylococcal enterointoxication (staphylococcal food poisoning) results from the ingestion of enterotoxins that are synthesized during growth of S. aureus in foods. S. aureus is capable of producing an enterotoxin in conditions such as: water activity >0.85, a range of pH between 4 to 9.8, temperatures from 10 to 48 °C and a good nutrient supply such as that provided by fresh cheese and other milk products (Halpin-Dohnalek and Marth, 1989).
Capsicum species have been the object of different studies (Dorantes et al., 2000; Careaga et al.... more Capsicum species have been the object of different studies (Dorantes et al., 2000; Careaga et al., 2003; Acero-Ortega et al., 2005) in order to determine their antimicrobial activity, the compounds that would be responsible for it, and the microorganisms that could be affected by it, finding that Staphylococcus aureus, Salmonella tiphymurium, Listeria monocytogenes, Pseudomonas aureaginosa and Bacillus cereus are susceptible to inhibition by Capsicum extracts. Some of the active compounds responsible for the inhibitory action are t-cinnamic acid and its derivatives, which are intermediate compounds in phenylpropanoids pathway. Capsicum annuum oleoresins are “generally recognized as safe” (GRAS) by the FDA, and so their use as natural antimicrobials is safe. However, it is important to know through predictive microbiology and modeling the quantitative effect of the Capsicum extracts, the active compounds, and the interactions with other factors such as pH and temperature. One of the food products that has been involved in outbreaks is fresh rennetcurdled cheese, which has a rich nutrient content, a high water activity and low acidity, which make it an adequate culture medium for the growth of a wide variety of bacteria. Some of these bacteria are known to cause food-borne illness, such as Staphylococcus aureus. It has been estimated that consumption of foods contaminated by this microorganism is responsible for 185,060 illnesses, 1,753 hospitalizations and two deaths per year in the United States. In the United Kingdom since 1980, numbers of reported cases have not exceeded 189 per year, although this is only a small percentage of actual cases (Sutherland and Varnam, 2002). S. aureus has also been involved in food-borne diseases in México, especially in the consumption of milk products. Staphylococcal enterointoxication (staphylococcal food poisoning) results from the ingestion of enterotoxins that are synthesized during growth of S. aureus in foods. S. aureus is capable of producing an enterotoxin in conditions such as: water activity >0.85, a range of pH between 4 to 9.8, temperatures from 10 to 48 °C and a good nutrient supply such as that provided by fresh cheese and other milk products (Halpin-Dohnalek and Marth, 1989).
Protoplanetary disks are composed primarily of gas (99% of the mass). Nevertheless, relatively fe... more Protoplanetary disks are composed primarily of gas (99% of the mass). Nevertheless, relatively few observational constraints exist for the gas in disks. In this review, I discuss several observational diagnostics in the UV, optical, near-IR, mid-IR, and (sub)-mm wavelengths that have been employed to study the gas in the disks of young stellar objects. I concentrate in diagnostics that probe the inner 20 AU of the disk, the region where planets are expected to form. I discuss the potential and limitations of each gas tracer and present prospects for future research.
FU Orionis objects (FUors) play a central role in the study of the evolution of young stars. They... more FU Orionis objects (FUors) play a central role in the study of the evolution of young stars. They undergo accretion outbursts that can bring up to about 0.01 solar masses per outburst, therefore providing a significant amount of mass in the pre-main sequence life of a star. Spitzer IRS observations of FUors have shown either silicate features in absorption and ice bands or silicates in emission with no ice bands. This led some authors to propose an evolutionary paradigm in which the former FUors are younger than the latter FUors. The FUor phase might be a common but rarely observed phase (about 20 FUors known) of most young low-mass stars and might be the link between Class I and Class II sources. So far, Spitzer has obtained IRS spectra of about half of the FUor catalog, focusing on its most famous class members. With this short Spitzer proposal, we aim to observe FUors that have not yet been observed with the IRS or had no high-resolution module spectra. We will study the composition and evolution of dust grains and of ices in FUors surrounded by envelopes, and we aim at detecting faint molecular hydrogen and atomic lines with the high-resolution module spectra. The IRS spectra will probe the stellar environment, and thus test the above evolutionary paradigm and the different theories for the origin of FUor outburst. The Spitzer IRS observations of our sample of FUors will therefore provide additional insights about a significant phase in the life of young stars with the aim to better describe the evolutionary sequence from Class I star to Class II sources.
La gran mayoría de los metales son policristalinos, es decir, formados por cristales, y a cada cr... more La gran mayoría de los metales son policristalinos, es decir, formados por cristales, y a cada cristal se le denomina grano. Se busca también explicar la relación entre el grano y las propiedades de los metales.
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