Showing papers by "Ensenada Center for Scientific Research and Higher Education published in 2006"

Climate Variability, Fish, and Fisheries

Abstract: Fish population variability and fisheries activities are closely linked to weather and climate dynamics. While weather at sea directly affects fishing, environmental variability determines the distribution, migration, and abundance of fish. Fishery science grew up during the last century by integrating knowledge from oceanography, fish biology, marine ecology, and fish population dynamics, largely focused on the great Northern Hemisphere fisheries. During this period, understanding and explaining interannual fish recruitment variability became a major focus for fisheries oceanographers. Yet, the close link between climate and fisheries is best illustrated by the effect of “unexpected” events—that is, nonseasonal, and sometimes catastrophic—on fish exploitation, such as those associated with the El Nino–Southern Oscillation (ENSO). The observation that fish populations fluctuate at decadal time scales and show patterns of synchrony while being geographically separated drew attention to oceanograph...

Large warming and salinification of the Mediterranean outflow due to changes in its composition

Abstract: The Mediterranean Sea transforms surface Atlantic Water (AW) into a set of cooler and saltier typical Mediterranean Waters (tMWs) that are formed in different subbasins within the sea and thus have distinct hydrological characteristics. Depending on the mixing conditions along their route and on their relative amounts, the tMWs are more or less differentiated at any given place, and some mix together up to forming new water masses. We emphasise the fact that any of these Mediterranean Waters (MWs) must outflow from the sea, even if more or less identifiable and/or in a more or less continuous way. Historical data from the 1960s–1980s showed that the densest MW outflowing through the Strait of Gibraltar at Camarinal Sill South (CSS) was a relatively cool and fresh tMW formed in the western basin, namely the Western Mediterranean Deep Water (WMDW). At these times, the sole other tMW identified in the strait was the Levantine Intermediate Water (LIW); no mention was made there of, in particular, the two densest tMWs formed in the eastern basin (in the Aegean and the Adriatic) that are now named Eastern Overflow Water (EOW) when they reach the Channel of Sicily (where they cannot be differentiated). A fortiori, no mention was made of the Tyrrhenian Dense Water (TDW) that results from the mixing of EOW with waters resident in the western basin (in particular WMDW) when it cascades down to ∼2000 m from the channel of Sicily. New measurements (essentially temperature and salinity time series) collected at CSS since the mid-1990s indicate that the densest MWs outflowing through the strait have been continuously changing; temperature and salinity there have been increasing, being actually (early 2000s) much warmer (∼0.3 °C) and saltier (0.06) than ∼20 years ago. These changes are one order of magnitude larger than the decadal trends shown for WMDW in particular. We thus demonstrate that, in the early 2000s, (i) the densest MW outflowing at Gibraltar is TDW and (ii) TDW is mainly composed of EOW (the percentage of MWs from the western basin, in particular WMDW, is lower): the densest part of the outflow is thus “more eastern than western”. This Mediterranean Sea Transient (a shift from the western basin to the eastern one) could be linked to the Eastern Mediterranean Transient (a shift from the Adriatic subbasin to the Aegean one). Whatever the case, we demonstrate that the proper functioning of the Mediterranean Sea leads to a variability in its outflow's composition that can have consequences for the mid-depth water characteristics in the North-Atlantic much more dramatic than previously thought.

Conservation of the vaquita Phocoena sinus

Abstract: The vaquita Phocoena sinus is a small porpoise that is endemic to the northern Gulf of California, Mexico. It is the most critically endangered marine small cetacean in the world. The most precise estimate of global abundance based on a 1997 survey is 567 (95% CI 177- 1073). 2. Vaquitas mainly live north of 30 ° 45 ' N and west of 114 ° 20 ' W. Their 'core area' consists of about 2235 km 2 centred around Rocas Consag, 40 km east of San Felipe, Baja California. Genetic analyses and population simulations suggest that the vaquita has always been rare, and that its extreme loss of genomic variability occurred over evolutionary time rather than being caused by human activities. 3. Gill nets for fish and shrimp cause very high rates of by-catch (entanglement) of vaquitas. Estimates of bycatch rates are from 1993-94 and refer to one of three main fishing ports: 84 per year (95% CI 14-155) using only data collected by observers and 39 per year (95% CI 14-93) using combined data from observers and interviews with fishermen. Boats from other ports may experience similar rates, and the total is probably well above what would be

PDO–ENSO Effects in the Climate of Mexico

Abstract: The role of the Pacific decadal oscillation (PDO) in El Nino–Southern Oscillation (ENSO)-related Mexican climate anomalies during winter and summer is investigated. The precipitation and mean temperature data of approximately 1000 stations throughout Mexico are considered. After sorting ENSO events by warm phase (El Nino) and cold phase (La Nina) and prevailing PDO phase: warm or high (HiPDO) and cold or low (LoPDO), the authors found the following: 1) For precipitation, El Nino favors wet conditions during summers of LoPDO and during winters of HiPDO. 2) For mean temperature, cooler conditions are favored during La Nina summers and during El Nino winters, regardless of the PDO phase; however, warmer conditions are favored by the HiPDO during El Nino summers.

Chitosomes: past, present and future

Abstract: Jose Ruiz-Herrera's discovery that chitin microfibrils could be made by a fungal extract paved the way for elucidating the intracellular location of chitin synthetase. In collaboration with Charles Bracker, chitosomes were identified as the major reservoir of chitin synthetase in fungi. Unique in size, buoyant density, and membrane thickness, chitosomes were found in a wide range of fungi. Their reversible dissociation into 16S subunits is another unique property of chitosomes. These 16S subunits are the smallest molecular entities known to retain chitin synthetase activity. Further dissociation leads to complete loss of activity. From studies with secretory mutants, yeast researchers concluded that chitosomes were components of the endocytosis pathway. However, key structural and enzymatic characteristics argue in favor of the chitosome being poised for exocytotic delivery rather than endocytotic recycling. The chitosome represents the main vehicle for delivering chitin synthetase to the cell surface. An immediate challenge is to elucidate chitosome ontogeny and the role of proteins encoded by the reported chitin synthetase genes in the structure or function of chitosomes. The ultimate challenge would be to understand how the chitosome integrates with the cell surface to construct the organized microfibrillar skeleton of the fungal cell wall.

Privacy-Aware Autonomous Agents for Pervasive Healthcare

Abstract: Hospitals are convenient settings for deploying pervasive computing technology, but they also raise important privacy concerns. Hospital work imposes significant demands on staff, including high availability, careful attention to patients, confidentiality, rapid response to emergencies, and constant coordination with colleagues. These demands shape the way hospital workers experience and understand privacy. In addition, healthcare professionals experience a high level of mobility because they must collaborate with colleagues and access information and artifacts distributed throughout the premises. Autonomous agents can help developers design privacy-aware systems that handle the threats raised by pervasive technology

Identification of bacterial diversity in the oyster Crassostrea gigas by fluorescent in situ hybridization and polymerase chain reaction

Abstract: Aims: To carry out a rapid and reliable identification of bacterial diversity in the oyster Crassostrea gigas from Todos Santos Bay, Mexico, in the current study we applied the molecular techniques of fluorescent in situ hybridization (FISH) and polymerase chain reaction (PCR). In order to reach this goal, genus and group-specific oligonucleotides targeted to 16S rDNA/rRNA were used. Methods and Results: Oysters were collected and different tissues were analysed by means of culture-independent methodologies. In the digestive glands and gonads γ-Proteobacteria and Gram-positive bacteria with a low G+C content, were identified as metabolically active by FISH. In the oyster gills a higher active diversity was observed, including Gram-positive bacteria with a low and high G+C content, members of the Cytophaga/Flavobacterium cluster and γ-Proteobacteria. Consistent with FISH analysis, the amplification of 16S rDNA genes fragments with genus and group-specific oligonucleotides confirmed the presence of the same groups, as well as members of the α- and β-Proteobacterias, Pseudomonas spp. and Bacillus spp. Conclusions: The combination of accurate and very easy-to-apply molecular methods allowed us to carry out a rapid screening of high bacterial diversity in oysters. Significance and Impact of the Study: This work is the first report about bacterial diversity in oyster tissues analysed by FISH and PCR, without using culture-dependent methods and allowed us to determine the phylogenetic diversity of the bacterial communities present in oyster cultures, including bacteria with and without metabolic activity, as well as uncultivable cells, which are generally underestimated by traditional identification.

Generation of two-photon States with an arbitrary degree of entanglement via nonlinear crystal superlattices.

Abstract: We demonstrate a general method of engineering the joint quantum state of photon pairs produced in spontaneous parametric down-conversion. The method makes use of a superlattice structure of nonlinear and linear materials, in conjunction with a broadband pump, to manipulate the group delays of the signal and idler photons relative to the pump pulse, and realizes photon pairs described by a joint spectral amplitude with arbitrary degree of entanglement. This method of group-delay engineering has the potential of synthesizing a broad range of states including factorizable states crucial for quantum networking and states optimized for Hong-Ou-Mandel interferometry. Experimental results for the latter case are presented, illustrating the principles of this approach.

Sheared turbulence in a weakly stratified upper ocean

Abstract: Microstructure, ADCP and CTD profiles taken in the North Atlantic along 53°N under moderate and high winds showed that the median of log-normally distributed kinetic energy dissipation rate e within the upper mixing layer is 1.5×10−7 W/kg and the layer depth, on the average, is ∼40 m. Assuming that mixing efficiency γ is a constant ( γ = 0.2 ), the following scaling is proposed for the normalized eddy diffusivity: K ^ b = K b / κ u * z = ( 1 + Ri / R i cr ) - p P r tr - 1 , where K b = γ e / N 2 , N2 is the squared buoyancy frequency, u * the surface friction velocity, Ri the local Richardson number, P r tr = 1 + Ri / R i β the turbulent Prandtl number, p = 1 or 2/3, Ricr=0.1 and Riβ=0.1 or 0.05. The power-law function with p = 1 relates the asymptotes of Kb(Ri) to the buoyancy scale L N ∼ ( e / N 3 ) 1 / 2 at Ri⪢Ricr and to the shear scale L Sh ∼ ( e / Sh 3 ) 1 / 2 at Ri⪡Ricr. If p = 2 / 3 , the lengthscale L R = ( e / N 2 Sh ) 1 / 2 replaces LN in spectra of ocean microstructure than due to the influence of local shear. This mixing regime corresponds to intermediate Richardson numbers (∼0.25 Alternatively, if γ is not a constant, but an increasing function of Ri for 0 K ^ b ( Ri ) shows a very weak dependence on Ri for Ri K ^ b ( Ri ) is used.

Thermal preference and tolerance of green abalone Haliotis fulgens (Philippi, 1845) and pink abalone Haliotis corrugata (Gray, 1828)

Abstract: The thermoregulatory behaviour of green abalone Haliotis fulgens and pink abalone H. corrugata was investigated. Haliotis fulgens juveniles ranging in wet weight from 3.0 to 3.3 g and from 28.7 to 30.5 mm shell length and of H. corrugata 2.0 g and 25.7 mm in shell length were exposed to 19°C for 30 days in a flow-through water system. Temperature preference was determined in a horizontal thermal gradient and was found to be 25.4°C for green abalone and 25.0°C for pink abalone. Displacement velocity was 4.3 cm h⁻¹ for H. fulgens and 12.8 cm h⁻¹ for H. corrugata. The optimum temperature for growth calculated for both abalone species was 24.6 and 24.5°C respectively. The critical thermal maxima (CTMax) of H. fulgens and H. corrugata were determined as a measure of thermal tolerance. Abalones were subjected to increasing water temperatures at a rate of 1°C on 30 min until they detached from the substrate. The CTMax at 50% were 33.6 and 32.0°C for green and pink abalone respectively. The results are discussed in relation to site selection and commercial rearing.

Ground-Motion Predictions from Empirical Attenuation Relationships versus Recorded Data: The Case of the 1997–1998 Umbria-Marche, Central Italy, Strong-Motion Data Set

Abstract: We evaluate the goodness of fit of attenuation relations commonly used for the Italian national territory (Sabetta and Pugliese, 1996) by using the maximum likelihood approaches of Spudich et al. (1999) and Scherbaum et al. (2004). According to the classification scheme proposed by Scherbaum et al. (2004), the Sabetta and Pugliese (1996) relationships show consistent discrepancies between the predicted and the observed peak ground acceleration (pga) at rock sites in the Umbria- Marche region, central Italy; however, at soft sites the agreement between observations and prediction is satisfactory. The bias of the residuals, computed with the Sabetta and Pugliese (1996) models for pga, peak ground velocity, (pgv) and pseudovelocity response spectrum (psv) (for M l = 4–6 and epicentral distances up to 100 km) is negative. This means that on the average, the predictions overestimate the observations, but the overestimation decreases with increasing magnitude. Then, we present regional predictive relations (UMA05) for maximum horizontal pga, pgv, and 5%-damped psv, derived from the strong-motion data recorded in the Umbria-Marche area and classified as to four site categories. The UMA05 attenuation relationships for rock sites are log 10 (PGA) = −2.487 + M 1 − 1.280 log 10 ( R 2 + 3.94 2 ) 0.5 ± 0.268 log 10 (PGV) = −1.803 + 0.687 M 1 − 1.150 log 10 ( R 2 + 2.74 2 ) 0.5 ± 0.300 and log 10 (PGA) = −2.500 + 0.544 M 1 − 1.284 log 10 R h ± 0.292 log 10 (PGV) = −1.752 + 0.685 M 1 − 1.167 log 10 R h ± 0.297, where pga is measured in fraction of g and pgv in centimeters per second, M l is the local magnitude in the range 4–6, R is the epicentral distance in the range 1–100 km, and R h is the hypocentral distance in kilometers. We used the random effect model (Brillinger and Priesler, 1985; Abrahamson and Youngs, 1992; Joyner and Boore, 1993; Joyner and Boore, 1994) to estimate the component of variance related to the earthquake-to-earthquake, station-to-station, and record-to-record variability, and to quantify the benefit of introducing a site classification in the attenuation model to reduce the variance. The introduction of the site classification in the attenuation model allows a reduction of the station-to-station component of variability (from 0.19 to 0.14 for pga, and from 0.21 to 0.18 for pgv). We also found that the record- to-record component represents the largest contribution to the model uncertainty.

Assessing the Use of Instant Messaging in Online Learning Environments.

Abstract: There is a body of evidence supporting the claim that informal interactions in educational environments have positive effects on learning. In order to increase the opportunities of informal interaction in online courses, an instant messaging tool, called CENTERS, was developed and integrated into online learning environments. This tool provides the students with awareness of the presence of others connected to the course at the same time and allows them to interact by means of two communication facilities: instant messaging and one-to-one chat. To evaluate the reliability of CENTERS as a tool to promote interaction, we studied the performance and use of the system during one graduate and three undergraduate online courses. The participants were 43 students and 4 teachers. Analyses of the logs show that the system was used mainly for socializing but that it also supported the students' learning activities. The responses to the questionnaires with regard to the students' perceived use of the system were in ...

Adaptive synthetic discriminant function filters for pattern recognition

Abstract: New adaptive correlation filters based on a conventional synthetic discriminant function (SDF) for reliable recognition of an object in cluttered background are proposed. The information about an object to be recognized, false objects, and a background to be rejected is utilized in an iterative training procedure to design a correlation filter with a given value of discrimination capability. Computer simulation results obtained with the proposed adaptive filter in test scenes are discussed and compared with those of various correlation filters in terms of discrimination capability, tolerance to input additive noise that is always present in image sensors, and to small geometric image distortions.

Phylogeography of the flag cabrilla Epinephelus labriformis (Serranidae): implications for the biogeography of the Tropical Eastern Pacific and the early stages of speciation in a marine shore fish

Abstract: Aim To examine the role of previously described biogeographical boundaries in shaping phylogeographical relationships within and among two putative eastern Pacific sibling species, the flag cabrilla, Epinephelus labriformis and the Clipperton grouper, Epinephelus clippertonensis (Serranidae). Location Tropical Eastern Pacific (TEP). Methods Sequence data from the mitochondrial cytochrome b gene were obtained from samples throughout the range of the species. Coalescence analysis, mismatch distributions and an analysis of molecular variance (amova) were used to infer population differentiation. Results Overall, 49 haplotypes were found among 304 specimens, and there was significant structure corresponding to geographical locality (amova, Uct ¼ 0.198, P < 0.001; Ust ¼ 0.207, P < 0.001; Fst ¼ 0.169, P < 0.001; Fct ¼ 0.151, P ¼ 0.036). Coalescence analysis indicates a population expansion at Clipperton Atoll during the mid-Pleistocene. Main conclusions Our results suggest that previously described barriers to dispersal along the mainland of the TEP may not impinge on the dispersal ability of marine species, such as these groupers, that have long-lived pelagic larvae. In contrast, gene flow between mainland and island populations of the readily distinguishable morphospecies E. labriformis and E. clippertonensis is restricted. The low level of genetic differentiation between the two species indicates that changes in external colour patterns may evolve more rapidly than genetic markers commonly used to delimit species boundaries. Thus a combination of colour differences and a lack of reciprocal monophyly may act as good indicators of incipient speciation in the marine environment.

Circulation along the Mexican Caribbean coast

Abstract: [1] Data from an array of seven subsurface upward-looking moored Acoustic Doppler Current Profilers (ADCPs) and four subsurface pressure sensors deployed from August 2002 to August 2003 along the Caribbean coast of Mexico showed that the currents in the area have a predominant northeastward direction along the coast, are coherent within the upper 130 m of the water column, and have a general tendency to increase northward, reaching magnitudes of 2.4 m/s north of Cozumel. In addition, important weeklong reversal periods (southward flows) are observed around Chinchorro Bank. A vertical current profile EOF analysis at each station indicates high coherence within the study area, with the first vertical mode at each station explaining at least 69% of variance and current vectors aligned with the coast. A second EOF analysis carried out for any uniform depth level using current data from all stations shows high coherence in the horizontal as well. The first mode explains at least 59% of the variance and has a dominant 3-month-long variability. Comparison between the current patterns along the Mexican Caribbean coast and in the Yucatan Channel suggests that dynamics of the entire area might be strongly influenced by the passage of eddies through the region. Comparison of a Singular Spectral Analysis (SSA) of the principal components of currents with the pressure difference across the channels supports the idea of eddies modulating current variability. Numerical model results indicate that high values of the current intensity indexes are associated with eddies. The flow along Chinchorro and Cozumel channels is in geostrophic balance most of the observation time, but with week-long ageostrophic periods which are predominant off Cozumel. These events appear to occur when eddies are traversing the region.

Intensity noise in SBS with injection locking generation of Stokes seed signal

Abstract: We present experimental and theoretical investigation of intensity noise features in SBS for experimental configuration utilized injection locking of two semiconductor lasers for Stokes signal generation. Significant decreasing of the intensity noise of the Stokes signal with the frequency equal to the Brillouin resonance is observed and analytically explained.

PdO/Al 2 O 3 –(Ce 1-X Zr X )O 2 catalysts: effect of the sol-gel support composition

Abstract: The contribution of (Ce1-X Zr X )O2 additives to alumina supports prepared by sol-gel and the catalytic properties of PdO/Al2O3–(Ce1-X Zr X )O2 catalysts (~0.3 wt% Pd, ~5 wt% (Ce1-X Zr X )O2) in CO oxidation was herein investigated. The addition of (Ce1-X Zr X )O2 to the support enhanced the surface area and decreased the size of Al2O3 particles. The UV–Vis bands of PdO particles and Pd2+ ions indicate that zirconia in (Ce1-X Zr X )O2 promotes palladium-support interactions by forming highly dispersed PdO particles. Temperature-programmed reduction (TPR) in hydrogen revealed that ceria enhanced the redox capacity of the supports while zirconia lowered the reduction temperature of palladium oxide species. The comprehensive study revealed that the Ce/Zr ratio was a key factor influencing the catalytic activity of samples in CO oxidation, because palladium oxide-support interactions had a significant effect in changing of the reducibility of samples. So, the PdO/Al2O3–(Ce0.5Zr0.5)O2 exhibited the highest catalytic activity.

Robust and efficient algorithm of image enhancement

Abstract: A method for enhancing the local contrast of a noisy image using sliding discrete transforms is proposed. A minimum mean-square error estimator in the domain of a sliding transform for noise removal is derived. This estimator is based on a fast inverse sliding transform. Local contrast enhancement is performed by a nonlinear modification of denoised local spectrum coefficients. To provide image processing in real time, a fast recursive algorithm for computing the sliding transform is utilized. The algorithm is based on a recursive relationship between three subsequent local spectra. Computer simulation results using a real image are provided and discussed.

Transboundary seabird conservation in an important North American marine ecoregion

Abstract: SUMMARY Many seabird species of conservation concern have large geographic ranges that span political borders, forcing conservation planners to facilitate their pro- tection in multiple countries. Seabird conservation planningwithintheseabird-diverseCaliforniaCurrent System (CCS) marine ecoregion presents an important opportunityfortransboundarycollaborationstobetter protect seabirds across the USA/Mborder. While seabird populations in the USA are relatively well- studied and well-protected, the status of seabird populations in the Mexican region of the CCS is not well known and seabird colonies have been virtually unprotected. This study synthesizes and supple- ments information on breeding seabird diversity and distribution, identifies and ranks threats to seabirds and evaluates conservation capacity in the Mexican CCStoprovideaframeworkfortransboundaryseabird conservation throughout the CCS ecoregion. Island- breeding seabirds in M´ exico support 43-57% of CCS breeding individuals, 59% of CCS breeding taxa and a high level of endemism. Connectivity between populations in Mand the USA is high. At least 17 of the 22 extant Mexican CCS breeding seabirds are USA/M´ exico transboundary breeders or foragers, 13 of which are federally listed in the USA or M´ exico. Introduced predators and human disturbance have caused multiple seabird population extirpations in the Mexican CCS because breeding colonieslacklegalprotectionorenforcement.However, conservation capacity in this region has increased rapidly in recent years through the establishment of new protected areas, growth of local conservation non-governmental organizations, and increase in local community support, all of which will allow for more effective use of conservation funds. Transboundary conservation coordination would better protect CCS seabirds by facilitating restoration of seabird colonies in the Mexican CCS and enabling an ecoregion-wide