190 research outputs found
The Relationship between Photosynthesis and Irradiance for Gulf of California Phytoplankton
During June 17-28, 1982, we carried on experiments to generate
photosynthesis-irradiance curves for phytoplankton from five locations of the
central and northern Gulf of California. Using natural sunlight, on board 14C
incubations were done with samples collected from five different depths within
the euphotic zone. In general there were great vertical changes of variables
controlling primary productivity, even in cases where weak vertical TOC gradients
indicated high instability and mixing of the euphotic zone. The assimilation
number (PBm) had a two fold variation within the mixed layer. In general PBm
decreased monotonically with depth due to phytoplankton conditioning to lower
irradiances. Surface PBm values had a range of 8 to 15mg C. mg Chl a- 1. h-1.
When a thermocline was present, PBm for the bottom of the euphotic zone was
about 4 to 10% of that for surface waters. But, without a thermocline, P~ for
the bottom of the euphotic zone was ~ 60% of that for surface waters, due to
turbulence moving phytoplankton up and down the water column. Diatoms
were abundant in three stations near Angel de la Guarda and Tiburon islands.
For the station at the central gulf and the one at the very northern gulf, very few
nano and microplankton were found with the inverted scope technique, but high
chlorophyll concentrations and primary productivity indicated a high abundance
of picoplankton. This difference in plankton size composition was not
reflected in PBm values. Nutrient concentrations were high and did not limit PBm
values. Our PBm values are higher than those reported for the gulf's winter
phytoplankton; and they are about two times higher than those for winter
phytoplankton of the oceanic region between San Diego and Acapulco. Our
Gulf of California integrated primary productivity values had a range of 1.3 to
4.4gC. m-2. d-1
Impacto del turismo sobre el bienestar de los mexicanos y de los hogares que en México y sus regiones se dedican al turismo
En el debate sobre la relación entre turismo y bienestar existe consenso en que este es un poderoso instrumento para generar crecimiento eco- nómico. Trabajos en materia turística se han dedicado a cuanti car la riqueza generada por el turismo y a analizarlo como parte de una política pro-poor; sin embargo, no existen investigaciones que midan su impacto sobre el bienestar. El objetivo de esta investigación es evaluar los efectos del turismo sobre el bienestar de los mexicanos y sus regiones, así como conocer la situación de bienestar que prevalece en los hogares que en México se dedican al turismo, medido por su capacidad de consumo, la línea de bienestar urbana del Coneval y el método de Serrano.
Dichloridobis(methanol-κO)[cis-(±)-2,4,5-tris(pyridin-2-yl)-2-imidazoline-κ3 N 2,N 3,N 4]ytterbium(III) chloride
In the crystal structure of the title complex, [YbCl2(C18H15N5)(CH3OH)2]Cl, the pseudo-pentagonal–bipyramidal coordination geometry of the YbIII cation is composed of three N atoms from one cis-(±)-2,4,5-tris(pyridin-2-yl)imidazoline (HL) ligand, two O atoms from two methanol molecules and two Cl− anions. Chains are formed along [010] through N—H⋯Cl, O—H⋯Cl and O—H⋯N hydrogen bonds
Determinants of Mental Health and Self-Rated Health: A Model of Socioeconomic Status, Neighborhood Safety, and Physical Activity
Objectives. We investigated the underlying mechanisms of the influence of socioeconomic status (SES) on mental health and self-rated health (SRH), and evaluated how these relationships might vary by race/ethnicity, age, and gender
Phytoplankton size-fractionated chlorophyll-a off Baja California during winter, spring, and summer 2008
Spatial and temporal size-fractionated phytoplankton chlorophyll-a (Chl-a) variability as pico-nanoplankton (PN, 0.4- 8.0 µm) and nano-microplankton (NM, >8.0 µm) off Baja California is shown. Chl-a samples from the upper 200 m were obtained from nearshore, offshore, and intermediate locations during winter, spring, and summer 2008. PN-Chl-a contribution to phytoplankton biomass was ~4 times higher than NM fraction. Chl-a PN/NM ratio increased toward offshore, while total Chl-a (PN + NM) decreased. Seasonally, offshore phytoplankton cells abundance had a comparable contribution for both size-fractions, without an apparent change by the integrated water-column total Chl-a (60 mg m?2). Vertical Chl-a profiles were similar for winter and summer seasons. The highest Chl-a concentration and phytoplankton-cells abundance arose in spring, predominantly for NM at nearshore locations, reaching from 2.7-fold (nearshore: middle) to 4.2-fold (middle: offshore) ratios. Phytoplankton Chl-a increased from winter to spring (5.4 times), with maximum contribution of NM (6.6 times) at nearshore zones. Water-column integrated phytoplankton abundance was 5-fold higher in spring than winter, and 2-fold over summer. Using optical microscopy, dinoflagellate cells were the most abundant and variable phytoplankton recognizable group at intermediate zone. Smaller phytoplankton cells sustained approximately continuous biomass off Baja California. The spatial and temporal phytoplankton biomass variability was mainly influenced by an increase of larger cells as result of spring coastal upwelling events
Frequency and risk factors of intestinal parasites in pet dogs from Mexicali, Mexico
Parasitic intestinal infections in dogs represent a problem for human health, because a wide variety of these parasites have zoonotic potential. Therefore, proximity to pets puts us at risk. The objective of this study was to determine the frequency and risk factors (age, sex, size, breed, presence of ectoparasites and gastrointestinal disorders) of intestinal parasites in the feces of dogs attending a Veterinary Hospital in the City of Mexicali, Baja California, Mexico. A total of 148 fecal samples were collected from canine patients and analyzed for parasite identification and parasite load. A 12.2% (18/148) of the samples were positive to parasitic intestinal infections. The frequency of specific infections was an 8.1% of Cryptosporidium sp., followed by a 2.7% of Cystoisospora sp., and 1.4% of Toxascaris leonina. A statistical significance was identified between the presence of intestinal parasites and mongrel breed. The predominance of protozoa shows the importance of diagnosis prior to treatment with anthelminthic drugs, since preventive antiparasitic protocols are commonly used, although these particular parasites are out of the spectrum of those drugs. Cryptosporidium spp. have zoonotic potential, particularly in immunocompromised patients, and there are few or no treatment options
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Seasonal and interannual variability of satellite-derived chlorophyll pigment, surface height, and temperature off Baja California
Mean fields, seasonal cycles, and interannual variability are examined for fields of
satellite-derived chlorophyll pigment concentrations (CHL), sea surface height (SSH), and
sea surface temperature (SST) during 1997–2002. The analyses help to identify three
dynamic regions: an upwelling zone next to the coast, the Ensenada Front in the north,
and regions of repeated meanders and/or eddy variability west and southwest of Point
Eugenia. High values of CHL are found in the upwelling zone, diminishing offshore. The
exception is the area north of 31°N (the Ensenada Front), where higher CHL are found
about 150 km offshore. South of 31°N, the long-term mean dynamic topography decreases
next to the coast, creating isopleths of height parallel to the coastline, consistent with
southward geostrophic flow. North of 31°N the mean flow is toward the east, consistent
with the presence of the Ensenada Front. The mean SST reveals a more north-south
gradient, reflecting latitudinal differences in surface heating due to solar radiation.
Harmonic analyses and EOFs reveal the seasonal and interannual patterns, including the
region of repeated eddy activity to the west and southwest of Point Eugenia. A maximum
CHL occurs in spring in most of the inshore regions, reflecting the growth of
phytoplankton in response to the seasonal maximum in upwelling-favorable winds. SST
and SSH anomalies are negative in the coastal upwelling zone in spring, also consistent
with a response to the seasonal maximum in upwelling. When the seasonal cycle is
removed, the strongest signal in the EOF time series is the response to the strong 1997–
1998 El Niño, with a weaker signal representing La Niña (1998–1999) conditions.
El Niño conditions consist of low chlorophyll, high SSH, and high SST, with opposite
conditions during La Niña
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