Isla San Pedro Nolasco(ISPN)is a structural high bounded by inactive dextral oblique-slip faults in the east-central part of the Gulf of California rift zone and is composed of intrusive rocks not exposed on other Gul...Isla San Pedro Nolasco(ISPN)is a structural high bounded by inactive dextral oblique-slip faults in the east-central part of the Gulf of California rift zone and is composed of intrusive rocks not exposed on other Gulf of California islands.Here we present the reconnaissance results from geological mapping,as well as first geochemical and geochronological data for the ISPN intrusive complex.The intrusive rocks compose a sheet-like body of intermediate and felsic composition intruded by an intermediate and acidic dike swarm.All intrusive rocks(host and dikes)range in age from ca.9 Ma to 10 Ma(^(40)Ar/^(39)Ar)and show a hydrous ferromagnesian mineral association(amphibole and biotite)with a calc-alkalic and transitional affinity.This hydrated mineralogical association has not been recognized in the coeval rocks along the onshore western margin of the North American plate(coastal Sonora).However,such hydrous mineralogical association is found in the coeval rift transitional volcanic rocks from the Baja California Microplate at Santa Rosalía and Bahía de LosÁngeles–Bahía de LasÁnimas.The ISPN continental block,at least 40 km long,has been pulled apart by transtensional faulting of the late Miocene Gulf of California shear zone before the westward migration of the North America-Pacific plate boundary at ca.3–2 Ma.Eventually,ISPN became isolated as an island during the late Miocene flooding of the Gulf of California seaway.展开更多
The brown shrimp, Farfantepenaeus californiensis, is the most important shrimp species in the Mexican Pacific coastal fisheries, with annual yields averaging 20,000 metric tons. The Mexican state of Sinaloa has the la...The brown shrimp, Farfantepenaeus californiensis, is the most important shrimp species in the Mexican Pacific coastal fisheries, with annual yields averaging 20,000 metric tons. The Mexican state of Sinaloa has the largest Mexican fleet of shrimp trawlers (736 boats) with annual landings of 7000 tons of brown shrimp on average. The status of the brown shrimp fishery was assessed using commercial catch and effort data of the Sinaloa shrimp trawl fleet over 16 years, from 1995 to 2011. We developed a biomass dynamic Schaefer model and used resampling techniques to analyze the catch-per-unit effort (CPUE) of the trawl brown shrimp fishery in the southeastern Gulf of California,Mexico. To ascertain robustness of our conclusions, two hypotheses were tested: observation and process error. Explicitly accounting for observation errors produced the best model fit to available data than including process errors. We identified several sources of observation error, for example discriminating fishing effort by species, changes in catch ability and misreported catch. The brown shrimp fishery showed symptoms of overfishing, although catch reported in the last fishing season considered in the analyses seems to indicate a rapid recovery of the stock. Finally, we predicted for the 2011-12 fishing season a catch of 9630 tonsof brown shrimp.展开更多
Samples taken during the closed fishing seasons from 1992 to 2010 were analyzed at sea. These data along with the landing records for the fishing periods from 1992-1993 to 2009-2010 were used to allow the situation of...Samples taken during the closed fishing seasons from 1992 to 2010 were analyzed at sea. These data along with the landing records for the fishing periods from 1992-1993 to 2009-2010 were used to allow the situation of Litopenaeus van-namei from the coasts of Sinaloa and Nayarit to be analyzed by means of stochastic models and by a graphic approach for the surplus biomass. Using the catch from 1993-1994 as a reference point and comparing this to the 2008-2009 catch revealed a stock decrease of about 65%. By taking into account the percentage contribution to total shrimp land-ings, these changes showed a decrease from 76% to 12%. There were changes between 2000 and 2001 when the fleet grew by 50%. Considering a 3600 t maximum sustained yield (MSY) in the series 1992-2010, 50% of the reports are lower. It is necessary to recover the stock.展开更多
A monitoring program was developed to assess the cover of saltgrass managed for dust control on the saline dry Owens Lake. Although the original intent was to manage the vegetation as total cover that included green a...A monitoring program was developed to assess the cover of saltgrass managed for dust control on the saline dry Owens Lake. Although the original intent was to manage the vegetation as total cover that included green and senesced leaf and stem material, aged leaves that make up a large proportion of total cover were not differentiable spectrally from the background salt and lakebed. Hence, greenness-based indices were explored for detection of plant recruitment. Since all plant cover begins as green and growing, greenness indices provide a measure of all future cover whether living or senesced. The criteria for judging compliance were changed so that spatially variable vegetation cover measured as a milestone will need to be met in the future. A derivative of NDVI, NDVIx, calculated using scene statistics, proved highly accurate, to about 0.001 of this index and with an average signal to noise ratio of 64. This high level of accuracy allowed detection of small changes in vegetation growth and vigor. Performance according to the benchmark-as-par standard was determined through combined use of cumulative distribution functions and derivative maps.展开更多
Extensive dust control on the dry Owens Lake mainly uses constructed basins that are flooded with shallow depths of fresh water. This dust control is mandated by law as a minimum percent of the area of each individual...Extensive dust control on the dry Owens Lake mainly uses constructed basins that are flooded with shallow depths of fresh water. This dust control is mandated by law as a minimum percent of the area of each individual wetting basin. Wetted surfaces are evaluated for area and degree of wetness using the shortwave infrared (SWIR) band of Landsat TM, or similar earth observation satellite sensor. The SWIR region appropriate for these measurements lies within the electromagnetic spectrum between about 1.5 and 1.8 μm wavelengths. A threshold value for Landsat TM5 band 5 reflectance of 0.19 was found to conform with surfaces having a threshold for adequate wetting at a nascent point where rapid drying would occur following loss of capillary connection with groundwater. This threshold is robust and requires no atmospheric correction for the effects of aerosol scatter and attenuation as long as the features on the image appear clear. Monthly monitoring of surface wetting has proven accurate, verifiable and repeatable using these methods. This threshold can be calibrated for any Earth observation satellite that records the appropriate SWIR region. The monitoring program is expected to provide major input for the final phase of the dust control program that will have a focus to conserve water and resources.展开更多
The California least tern (Sternula antillarum browni) is an endangered species. The two largest colonies of this bird species in the San Francisco Bay, California, USA, are located 23 km apart at Alameda Point and ...The California least tern (Sternula antillarum browni) is an endangered species. The two largest colonies of this bird species in the San Francisco Bay, California, USA, are located 23 km apart at Alameda Point and Hayward Regional Shoreline. The Alameda Point colony, on the former Naval Air Station, Alameda, has grown at an average rate of 9.2% per year since its discovery in 1976 and has a nesting density ranging from 1-153 nests per ha. Long-term breeding success at Alameda has averaged 0.86 fledglings per breeding pair. Least tems began appearing in 2003, at an island in Hayward enhanced with substrate mediums and social attraction devices. Successful breeding attempts have been observed at the Hayward colony since 2006. The Hayward colony has grown at an average rate of 51.5% per year, has a nesting density ranging from 33-333 nests per ha and long-term breeding success average of 0.87 fledglings per breeding pair. Dropped fish have been collected from both colonies, and silversides (family Atherinopsidae) are the dominant prey. Alameda terns forage on a greater variety of species than the Hayward terns. The regression results indicate the importance of Northern anchovy (Engraulis mordax) to the breeding success of the Alameda colony.展开更多
In this study, we present results from the CASA (Carnegie-Ames-Stanford Approach) model to estimate net primary production (NPP) in grasslands under different management (ranching versus unmanaged) on the Central Coas...In this study, we present results from the CASA (Carnegie-Ames-Stanford Approach) model to estimate net primary production (NPP) in grasslands under different management (ranching versus unmanaged) on the Central Coast of California. The latest model version called CASA Express has been designed to estimate monthly patterns in carbon fixation and plant biomass production using moderate spatial resolution (30 m to 250 m) satellite image data of surface vegetation characteristics. Landsat imagery with 30 m resolution was adjusted by contemporaneous Moderate Resolution Imaging Spectroradiometer (MODIS) data to calibrate the model based on previous CASA research. Results showed annual NPP predictions of between 300 - 450 grams C per square meter for coastal rangeland sites. Irrigation increased the predicted NPP carbon flux of grazed lands by 59 grams C per square meter annually compared to unmanaged grasslands. Low intensity grazing activity appeared to promote higher grass regrowth until June, compared to the ungrazed grassland sites. These modeling methods were shown to be successful in capturing the differing seasonal growing cycles of rangeland forage production across the area of individual ranch properties.展开更多
We use 146 422 P-wave arrival times from 6 347 local earthquakes recorded by the Southern California SeismicNetwork to determine a detailed three-dimensional P-wave velocity structure at 0~35 km depth. We have takeni...We use 146 422 P-wave arrival times from 6 347 local earthquakes recorded by the Southern California SeismicNetwork to determine a detailed three-dimensional P-wave velocity structure at 0~35 km depth. We have takeninto account the Moho depth variations, which were obtained by seismological methods. Checkerboard tests sug-gest that our inversion results are reliable. Our models provide new information on regional geological structuresof Southern California. At shallow depths P-wave velocity structure correlates with surface geological features andexpresses well variations of surface topography of the mountains and basins. The velocity structure at each layer ischaracterized by block structures bounded by large faults. Ventura Basin, Los Angeles Basin, Mojave Desert, Pen-insular Ranges, San Joaquin Valley, Sierra Nevada, and Salton Trough show respectively all-round block. SanAndreas Fault becomes an obvious boundary of the region. To its southwest, the velocity is higher, and there arestrong heterogeneity and deeper seismicity; but to its northeast, the velocity is lower and shows less variation thanto the southwest, the seismicity is shallower. To investigate the effect of the Moho geometry we conducted inver-sions for two cases: one for flat Moho geometry, another for a Moho with lateral depth variations. We found thatthe topography of the Moho greatly affects the velocity structure of the middle and lower crust. When the Mohotopography is considered, a more reasonable tomographic result can be obtained and the resulting 3-D velocitymodel fits the data better.展开更多
The Santa Cruz Mountain range in northern California is a coastal landscape with a history of extensive forest logging and frequent large wildfires that have recently destroyed numerous residential structures at the w...The Santa Cruz Mountain range in northern California is a coastal landscape with a history of extensive forest logging and frequent large wildfires that have recently destroyed numerous residential structures at the wildland interface. Results from Landsat satellite image time-series analysis since 1984 of the study area within the Los Gatos Creek and Corralitos Creek watersheds showed that none of the severe drought periods since the 1980s have notably inhibited rapid tree and shrub regrowth rates on steep hill slopes burned recently by the 1985 Lexington Fire and the 2008 Summit Fire. In high burn severity areas of both fires, post-fire vegetation types showed a marked increase in shrub cover, mainly at the expense of evergreen tree cover. Most of these low (<3 m), dense stands of evergreen woody species have regenerated in as little as five years from bare charred ground. A combination of Landsat and Laser Altimeter (GLAS) satellite sensor data revealed that exposed south-facing slopes are presently supporting 200 to 240 Mg·ha<sup>-1</sup> of standing woody biomass on the burned areas. This study is the first of its kind to utilize a full 30-year record of Landsat vegetation index data to monitor tree and shrub regrowth after stand-replacing wildfires in California.展开更多
AIM:To identify key variables associated with colon cancer testing using the 2009 California Health Inventory Survey(CHIS).METHODS:The CHIS has been conducted biennially since 2001 using a two-stage,geographically str...AIM:To identify key variables associated with colon cancer testing using the 2009 California Health Inventory Survey(CHIS).METHODS:The CHIS has been conducted biennially since 2001 using a two-stage,geographically stratified random-digit-dial sample design to produce a representative sample of the entire State.For this study we used survey data from 2001-2009 inclusive.We restricted our analysis to White,Black,and Hispanic/Latinos aged 50-80 years.Weighted data was used to calculate the proportion of participants who underwent some form of colon cancer testing(colonoscopy,flexible sigmoidoscopy or fecal occult blood testing) within the previous 5 years stratified by race/ethnicity.For inferential analysis,boot-strapping with replacement was performed on the weighted sample to attain variance estimates at the 95%CI.For mean differences among categories we used t-tests and for comparisons of categorical data we used Pearson's χ 2.Binary logistic regression was used to identify independent variables associated with undergoing some form of testing.Trend analysis was performed to determine rates of testing over the study period stratified by race.RESULTS:The CHIS database for 2009 had 30 857 unique respondents corresponding to a weighted sample size of 10.6 million Californians.Overall,63.0%(63.0-63.1) underwent a colon cancer test within the previous 5 years;with 70.5%(70.5%-70.6%) of this subset having undergone colonoscopy.That is 44.5%(44.4%-44.5%) of all individuals 50-80 underwent colonoscopy.By multivariable regression,those tested were more likely to be male(OR = 1.06;95%CI:1.06-1.06),Black(OR = 1.30;95%CI:1.30-1.31),have a family member with colon cancer(OR = 1.71;95%CI:1.70-1.72),and have health insurance(OR = 2.71;95%CI:2.70-2.72).Progressive levels above the poverty line were also associated with receiving a test(100%-199%:1.21;1.20-1.21),(200%-299%:1.41;1.40-1.42),(> 300:1.69;1.68-1.70).The strongest variable was physician recommendation(OR = 3.90;95%CI:3.88-3.91).For the Hispanic/Latino group,additional variables associated with testing were success of physician-patient communication(OR = 2.44;95%CI:2.40-2.48) and naturalized citizenship status(OR = 1.91;95%CI:1.89-1.93).Trend analysis demonstrated increased colon cancer testing for all racial/ethnic subgroups from 2001-2009 although the rate remained considerably lower for the Hispanic/Latino subgroup.CONCLUSION:Using CHIS we identified California citizens most likely to undergo colon cancer testing.The strongest variable associated with testing for all groups was physician recommendation.展开更多
In this paper we outline the science,engineering,and societal considerations of the prototype Earthquake Early Warning System( EEWS) in California and detail the development and testing of methodologies in the last 10...In this paper we outline the science,engineering,and societal considerations of the prototype Earthquake Early Warning System( EEWS) in California and detail the development and testing of methodologies in the last 10 years in America. Also,we give a brief introduction of Earthquake Early Warning( EEW) in China,and based on the summary of EEW in California we make an analysis of the perspectives,misconceptions,and challenges that China may have.展开更多
The dissolved ionic constituents of groundwaters are, in part, a record of the minerals and rocks in aquifers through which the water has flowed. The chemical composition and association of these major ions in groundw...The dissolved ionic constituents of groundwaters are, in part, a record of the minerals and rocks in aquifers through which the water has flowed. The chemical composition and association of these major ions in groundwaters have been used to trace groundwater flow paths and sources. In general, the chemical composition of water in carbonate\|rock aquifers is dominated by calcium, magnesium, and bicarbonate, whereas sodium, chloride, and sulfate can be dominant ions in the water that comes from volcanic aquifers or clay minerals. Since the \{1990’s\}, we have dealt with the geochemistry of groundwaters from more than 100 springs and wells in southern Nevada and eastern California, USA for major solutes and trace elements. This paper compiles the hydrochemical data of major ions of these groundwaters. Based on major ion geochemistry, groundwaters from southern Nevada and eastern California can be classified as carbonate aquifer water, volcanic aquifer water, and mixing water (either mixing of carbonate and volcanic aquifer waters or mixing with local recharges). Piper and Stiff diagrams of major ions have graphically shown the general chemical characteristics, classifications, and mixing relationships of groundwaters from southern Nevada and eastern California.展开更多
The three largest earthquakes in northern California since 1849 were preceded by increased decadal activity for moderate-size shocks along surrounding nearby faults. Increased seismicity, double-difference precise loc...The three largest earthquakes in northern California since 1849 were preceded by increased decadal activity for moderate-size shocks along surrounding nearby faults. Increased seismicity, double-difference precise locations of earthquakes since 1968, geodetic data and fault offsets for the 1906 great shock are used to re-examine the timing and locations of possible future large earthquakes. The physical mechanisms of regional faults like the Calaveras, Hayward and Sargent, which exhibit creep, differ from those of the northern San Andreas, which is currently locked and is not creeping. Much decadal forerunning activity occurred on creeping faults. Moderate-size earthquakes along those faults became more frequent as stresses in the region increased in the latter part of the cycle of stress restoration for major and great earthquakes along the San Andreas. They may be useful for decadal forecasts. Yearly to decadal forecasts, however, are based on only a few major to great events. Activity along closer faults like that in the two years prior to the 1989 Loma Prieta shock needs to be examined for possible yearly forerunning changes to large plate boundary earthquakes. Geodetic observations are needed to focus on identifying creeping faults close to the San Andreas. The distribution of moderate-size earthquakes increased significantly since 1990 along the Hayward fault but not adjacent to the San Andreas fault to the south of San Francisco compared to what took place in the decades prior to the three major historic earthquakes in the region. It is now clear from a re-examination of the 1989 mainshock that the increased level of moderate-size shocks in the one to two preceding decades occurred on nearby East Bay faults. Double-difference locations of small earthquakes provide structural information about faults in the region, especially their depths. The northern San Andreas fault is divided into several strongly coupled segments based on differences in seismicity.展开更多
This paper presents a comprehensive exploration of the complex phenomenon of homelessness in California,with a specific focus on the state’s three largest cities-Los Angeles,San Francisco,and San Diego.Against the ba...This paper presents a comprehensive exploration of the complex phenomenon of homelessness in California,with a specific focus on the state’s three largest cities-Los Angeles,San Francisco,and San Diego.Against the backdrop of a high cost of living and a housing market strained by insufficient affordable options,the multifaceted nature of social diversity further complicates the landscape,leading to a widespread presence of homelessness that spans both major urban centers and rural regions.Through an in-depth examination of the distinct challenges confronting each city,ranging from housing shortages to intricate social dynamics,this study seeks to illuminate the underlying factors driving homelessness and identify potential avenues for intervention.Moreover,the paper delves into the unique vulnerabilities experienced by certain demographics within the homeless population,including veterans,families with children,and LGBTQ+individuals,highlighting the critical need for targeted solutions tailored to their specific needs.By synthesizing existing research and incorporating firsthand accounts,this research endeavor aims to contribute to a deeper understanding of homelessness in California and inform the development of comprehensive strategies aimed at fostering inclusive,sustainable communities statewide.展开更多
The synchronous construction of the secondary lining during the boring of large-diameter shield faces challenges such as the design of the lining jumbo,the high requirements on the performance for the lining jumbo,the...The synchronous construction of the secondary lining during the boring of large-diameter shield faces challenges such as the design of the lining jumbo,the high requirements on the performance for the lining jumbo,the organization of the construction activities in the small and confined area,the horizontal transportation for shield boring and high safety management requirements.A super-long invert lining construction jumbo,as well as the matching California switch,is developed,which provides solution for the confliction between the invert lining construction and the horizontal transportation.The procedure and method for the synchronous operation of the shield boring and the secondary lining are developed by referring to the synchronous construction of the secondary lining during the boring of the TBMs in hard rocks.Due to the adoption of the synchronous operation of the shield boring and the secondary lining,the construction period is shortened and the construction cost is reduced.The paper can provide reference for the synchronous construction of the secondary lining in similar projects in the future.展开更多
A pair of Black Oystercatchers(Haematopus bachmani)established a nest in June 2022 at“Tern Town”,an island located in Hayward,California along the eastern side of the San Francisco Bay.This is the first documented o...A pair of Black Oystercatchers(Haematopus bachmani)established a nest in June 2022 at“Tern Town”,an island located in Hayward,California along the eastern side of the San Francisco Bay.This is the first documented occurrence of oystercatchers successfully nesting and fledgling young in association with California Least Terns.The island provides nesting habitat for three special status species.Since 2015,and for a total of six breeding seasons,the endangered California Least Tern(Sternula antillarum browni),the threatened Western Snowy Plover(Charadrius alexandrinus nivosus)and species-of-special-concern Black Skimmer(Rynchops niger),have nested successfully,in association with American Avocet(Recurvirostra americana)and Black-necked Stilt(Himantopus mexicanus).We collected shells near the oystercatcher nest to assess their diet.Diet data showed the oystercatchers foraged on,in decreasing order of abundance,Japanese Little-necked Clams(Ruditapes philippinarum),Ribbed Mussels(Geukensia demissa),Bent-nose Clams(Macoma nasuta),Limpets(Patellogastropoda sp.)and Bay Mussels(Mytilus edulis).This new report on breeding Black Oystercatchers indicates that managing habitat for California Least Tern,Western Snowy Plover,and Black Skimmer can also benefit Black Oystercatcher.This site-specific information on breeding Black Oystercatchers supports recovery plan tasks that are consistent with managing habitat for California Least Tern,Western Snowy Plover and Black Skimmer.展开更多
The California bearing ratio (CBR) test is the most widely spread method of determining the bearing strength of the pavement material and is fundamental to pavement design practice in most countries. This test is expe...The California bearing ratio (CBR) test is the most widely spread method of determining the bearing strength of the pavement material and is fundamental to pavement design practice in most countries. This test is expensive, laborious and time consuming, and to overcome this, Quasi static cone penetrometer machine was fabricated and used to measure the consistency limits (liquid limit-LL, Plastic limit-PL and Plasticity index-PI), which were used to develop an empirical equation to determine CBR. Soil samples were collected and unsoaked CBR, PL, LL and PI were determined according to BS 1377 part 9 and BS 1377-2;1990. Quasi static penetration forces at 20 mm depth of penetration were also determined at consistency limits. It was found that the force of 1020 gf and 60 gf was achieved at a depth of 20 mm at PI and LL respectively. The correlation and regression analysis between consistency limits, and the experimental CBR obtained showed coefficient of determination, R<sup>2</sup> = 0.907 between CBR and all the parameters using multiple linear regression analysis (MLRA). The regression equation developed was used together with the relationship developed between the Quasi static Penetration force at consistency limits and the tested consistency limits to come up with the General Empirical Equation. Verification of the formula showed that the correlation can be used accurately to determine the un soaked CBR.展开更多
基金supported by Grant #180784 from CONACyT (Mexico)Grant USO315007364 from DCEN UNISON to J.R. Vidal-Solanothe financial support from PAPIIT-DGAPA-UNAM internal project IN101521
文摘Isla San Pedro Nolasco(ISPN)is a structural high bounded by inactive dextral oblique-slip faults in the east-central part of the Gulf of California rift zone and is composed of intrusive rocks not exposed on other Gulf of California islands.Here we present the reconnaissance results from geological mapping,as well as first geochemical and geochronological data for the ISPN intrusive complex.The intrusive rocks compose a sheet-like body of intermediate and felsic composition intruded by an intermediate and acidic dike swarm.All intrusive rocks(host and dikes)range in age from ca.9 Ma to 10 Ma(^(40)Ar/^(39)Ar)and show a hydrous ferromagnesian mineral association(amphibole and biotite)with a calc-alkalic and transitional affinity.This hydrated mineralogical association has not been recognized in the coeval rocks along the onshore western margin of the North American plate(coastal Sonora).However,such hydrous mineralogical association is found in the coeval rift transitional volcanic rocks from the Baja California Microplate at Santa Rosalía and Bahía de LosÁngeles–Bahía de LasÁnimas.The ISPN continental block,at least 40 km long,has been pulled apart by transtensional faulting of the late Miocene Gulf of California shear zone before the westward migration of the North America-Pacific plate boundary at ca.3–2 Ma.Eventually,ISPN became isolated as an island during the late Miocene flooding of the Gulf of California seaway.
文摘The brown shrimp, Farfantepenaeus californiensis, is the most important shrimp species in the Mexican Pacific coastal fisheries, with annual yields averaging 20,000 metric tons. The Mexican state of Sinaloa has the largest Mexican fleet of shrimp trawlers (736 boats) with annual landings of 7000 tons of brown shrimp on average. The status of the brown shrimp fishery was assessed using commercial catch and effort data of the Sinaloa shrimp trawl fleet over 16 years, from 1995 to 2011. We developed a biomass dynamic Schaefer model and used resampling techniques to analyze the catch-per-unit effort (CPUE) of the trawl brown shrimp fishery in the southeastern Gulf of California,Mexico. To ascertain robustness of our conclusions, two hypotheses were tested: observation and process error. Explicitly accounting for observation errors produced the best model fit to available data than including process errors. We identified several sources of observation error, for example discriminating fishing effort by species, changes in catch ability and misreported catch. The brown shrimp fishery showed symptoms of overfishing, although catch reported in the last fishing season considered in the analyses seems to indicate a rapid recovery of the stock. Finally, we predicted for the 2011-12 fishing season a catch of 9630 tonsof brown shrimp.
文摘Samples taken during the closed fishing seasons from 1992 to 2010 were analyzed at sea. These data along with the landing records for the fishing periods from 1992-1993 to 2009-2010 were used to allow the situation of Litopenaeus van-namei from the coasts of Sinaloa and Nayarit to be analyzed by means of stochastic models and by a graphic approach for the surplus biomass. Using the catch from 1993-1994 as a reference point and comparing this to the 2008-2009 catch revealed a stock decrease of about 65%. By taking into account the percentage contribution to total shrimp land-ings, these changes showed a decrease from 76% to 12%. There were changes between 2000 and 2001 when the fleet grew by 50%. Considering a 3600 t maximum sustained yield (MSY) in the series 1992-2010, 50% of the reports are lower. It is necessary to recover the stock.
文摘A monitoring program was developed to assess the cover of saltgrass managed for dust control on the saline dry Owens Lake. Although the original intent was to manage the vegetation as total cover that included green and senesced leaf and stem material, aged leaves that make up a large proportion of total cover were not differentiable spectrally from the background salt and lakebed. Hence, greenness-based indices were explored for detection of plant recruitment. Since all plant cover begins as green and growing, greenness indices provide a measure of all future cover whether living or senesced. The criteria for judging compliance were changed so that spatially variable vegetation cover measured as a milestone will need to be met in the future. A derivative of NDVI, NDVIx, calculated using scene statistics, proved highly accurate, to about 0.001 of this index and with an average signal to noise ratio of 64. This high level of accuracy allowed detection of small changes in vegetation growth and vigor. Performance according to the benchmark-as-par standard was determined through combined use of cumulative distribution functions and derivative maps.
文摘Extensive dust control on the dry Owens Lake mainly uses constructed basins that are flooded with shallow depths of fresh water. This dust control is mandated by law as a minimum percent of the area of each individual wetting basin. Wetted surfaces are evaluated for area and degree of wetness using the shortwave infrared (SWIR) band of Landsat TM, or similar earth observation satellite sensor. The SWIR region appropriate for these measurements lies within the electromagnetic spectrum between about 1.5 and 1.8 μm wavelengths. A threshold value for Landsat TM5 band 5 reflectance of 0.19 was found to conform with surfaces having a threshold for adequate wetting at a nascent point where rapid drying would occur following loss of capillary connection with groundwater. This threshold is robust and requires no atmospheric correction for the effects of aerosol scatter and attenuation as long as the features on the image appear clear. Monthly monitoring of surface wetting has proven accurate, verifiable and repeatable using these methods. This threshold can be calibrated for any Earth observation satellite that records the appropriate SWIR region. The monitoring program is expected to provide major input for the final phase of the dust control program that will have a focus to conserve water and resources.
文摘The California least tern (Sternula antillarum browni) is an endangered species. The two largest colonies of this bird species in the San Francisco Bay, California, USA, are located 23 km apart at Alameda Point and Hayward Regional Shoreline. The Alameda Point colony, on the former Naval Air Station, Alameda, has grown at an average rate of 9.2% per year since its discovery in 1976 and has a nesting density ranging from 1-153 nests per ha. Long-term breeding success at Alameda has averaged 0.86 fledglings per breeding pair. Least tems began appearing in 2003, at an island in Hayward enhanced with substrate mediums and social attraction devices. Successful breeding attempts have been observed at the Hayward colony since 2006. The Hayward colony has grown at an average rate of 51.5% per year, has a nesting density ranging from 33-333 nests per ha and long-term breeding success average of 0.87 fledglings per breeding pair. Dropped fish have been collected from both colonies, and silversides (family Atherinopsidae) are the dominant prey. Alameda terns forage on a greater variety of species than the Hayward terns. The regression results indicate the importance of Northern anchovy (Engraulis mordax) to the breeding success of the Alameda colony.
文摘In this study, we present results from the CASA (Carnegie-Ames-Stanford Approach) model to estimate net primary production (NPP) in grasslands under different management (ranching versus unmanaged) on the Central Coast of California. The latest model version called CASA Express has been designed to estimate monthly patterns in carbon fixation and plant biomass production using moderate spatial resolution (30 m to 250 m) satellite image data of surface vegetation characteristics. Landsat imagery with 30 m resolution was adjusted by contemporaneous Moderate Resolution Imaging Spectroradiometer (MODIS) data to calibrate the model based on previous CASA research. Results showed annual NPP predictions of between 300 - 450 grams C per square meter for coastal rangeland sites. Irrigation increased the predicted NPP carbon flux of grazed lands by 59 grams C per square meter annually compared to unmanaged grasslands. Low intensity grazing activity appeared to promote higher grass regrowth until June, compared to the ungrazed grassland sites. These modeling methods were shown to be successful in capturing the differing seasonal growing cycles of rangeland forage production across the area of individual ranch properties.
基金Japan Society for Promotion of Science,Chinese State Key Program of Basic Research on Mechanisms and Predictions of Strong Continental Earthquakes
文摘We use 146 422 P-wave arrival times from 6 347 local earthquakes recorded by the Southern California SeismicNetwork to determine a detailed three-dimensional P-wave velocity structure at 0~35 km depth. We have takeninto account the Moho depth variations, which were obtained by seismological methods. Checkerboard tests sug-gest that our inversion results are reliable. Our models provide new information on regional geological structuresof Southern California. At shallow depths P-wave velocity structure correlates with surface geological features andexpresses well variations of surface topography of the mountains and basins. The velocity structure at each layer ischaracterized by block structures bounded by large faults. Ventura Basin, Los Angeles Basin, Mojave Desert, Pen-insular Ranges, San Joaquin Valley, Sierra Nevada, and Salton Trough show respectively all-round block. SanAndreas Fault becomes an obvious boundary of the region. To its southwest, the velocity is higher, and there arestrong heterogeneity and deeper seismicity; but to its northeast, the velocity is lower and shows less variation thanto the southwest, the seismicity is shallower. To investigate the effect of the Moho geometry we conducted inver-sions for two cases: one for flat Moho geometry, another for a Moho with lateral depth variations. We found thatthe topography of the Moho greatly affects the velocity structure of the middle and lower crust. When the Mohotopography is considered, a more reasonable tomographic result can be obtained and the resulting 3-D velocitymodel fits the data better.
文摘The Santa Cruz Mountain range in northern California is a coastal landscape with a history of extensive forest logging and frequent large wildfires that have recently destroyed numerous residential structures at the wildland interface. Results from Landsat satellite image time-series analysis since 1984 of the study area within the Los Gatos Creek and Corralitos Creek watersheds showed that none of the severe drought periods since the 1980s have notably inhibited rapid tree and shrub regrowth rates on steep hill slopes burned recently by the 1985 Lexington Fire and the 2008 Summit Fire. In high burn severity areas of both fires, post-fire vegetation types showed a marked increase in shrub cover, mainly at the expense of evergreen tree cover. Most of these low (<3 m), dense stands of evergreen woody species have regenerated in as little as five years from bare charred ground. A combination of Landsat and Laser Altimeter (GLAS) satellite sensor data revealed that exposed south-facing slopes are presently supporting 200 to 240 Mg·ha<sup>-1</sup> of standing woody biomass on the burned areas. This study is the first of its kind to utilize a full 30-year record of Landsat vegetation index data to monitor tree and shrub regrowth after stand-replacing wildfires in California.
基金Supported by Grant K24 DK83268 awarded to Friedenberg F
文摘AIM:To identify key variables associated with colon cancer testing using the 2009 California Health Inventory Survey(CHIS).METHODS:The CHIS has been conducted biennially since 2001 using a two-stage,geographically stratified random-digit-dial sample design to produce a representative sample of the entire State.For this study we used survey data from 2001-2009 inclusive.We restricted our analysis to White,Black,and Hispanic/Latinos aged 50-80 years.Weighted data was used to calculate the proportion of participants who underwent some form of colon cancer testing(colonoscopy,flexible sigmoidoscopy or fecal occult blood testing) within the previous 5 years stratified by race/ethnicity.For inferential analysis,boot-strapping with replacement was performed on the weighted sample to attain variance estimates at the 95%CI.For mean differences among categories we used t-tests and for comparisons of categorical data we used Pearson's χ 2.Binary logistic regression was used to identify independent variables associated with undergoing some form of testing.Trend analysis was performed to determine rates of testing over the study period stratified by race.RESULTS:The CHIS database for 2009 had 30 857 unique respondents corresponding to a weighted sample size of 10.6 million Californians.Overall,63.0%(63.0-63.1) underwent a colon cancer test within the previous 5 years;with 70.5%(70.5%-70.6%) of this subset having undergone colonoscopy.That is 44.5%(44.4%-44.5%) of all individuals 50-80 underwent colonoscopy.By multivariable regression,those tested were more likely to be male(OR = 1.06;95%CI:1.06-1.06),Black(OR = 1.30;95%CI:1.30-1.31),have a family member with colon cancer(OR = 1.71;95%CI:1.70-1.72),and have health insurance(OR = 2.71;95%CI:2.70-2.72).Progressive levels above the poverty line were also associated with receiving a test(100%-199%:1.21;1.20-1.21),(200%-299%:1.41;1.40-1.42),(> 300:1.69;1.68-1.70).The strongest variable was physician recommendation(OR = 3.90;95%CI:3.88-3.91).For the Hispanic/Latino group,additional variables associated with testing were success of physician-patient communication(OR = 2.44;95%CI:2.40-2.48) and naturalized citizenship status(OR = 1.91;95%CI:1.89-1.93).Trend analysis demonstrated increased colon cancer testing for all racial/ethnic subgroups from 2001-2009 although the rate remained considerably lower for the Hispanic/Latino subgroup.CONCLUSION:Using CHIS we identified California citizens most likely to undergo colon cancer testing.The strongest variable associated with testing for all groups was physician recommendation.
基金supported by the China Scholarship Council (CSC)China Earthquake Administration (CEA)+1 种基金Earthquake Administration of Hebei Provincepartially funded by the U. S. Geological Survey (USGS)
文摘In this paper we outline the science,engineering,and societal considerations of the prototype Earthquake Early Warning System( EEWS) in California and detail the development and testing of methodologies in the last 10 years in America. Also,we give a brief introduction of Earthquake Early Warning( EEW) in China,and based on the summary of EEW in California we make an analysis of the perspectives,misconceptions,and challenges that China may have.
文摘The dissolved ionic constituents of groundwaters are, in part, a record of the minerals and rocks in aquifers through which the water has flowed. The chemical composition and association of these major ions in groundwaters have been used to trace groundwater flow paths and sources. In general, the chemical composition of water in carbonate\|rock aquifers is dominated by calcium, magnesium, and bicarbonate, whereas sodium, chloride, and sulfate can be dominant ions in the water that comes from volcanic aquifers or clay minerals. Since the \{1990’s\}, we have dealt with the geochemistry of groundwaters from more than 100 springs and wells in southern Nevada and eastern California, USA for major solutes and trace elements. This paper compiles the hydrochemical data of major ions of these groundwaters. Based on major ion geochemistry, groundwaters from southern Nevada and eastern California can be classified as carbonate aquifer water, volcanic aquifer water, and mixing water (either mixing of carbonate and volcanic aquifer waters or mixing with local recharges). Piper and Stiff diagrams of major ions have graphically shown the general chemical characteristics, classifications, and mixing relationships of groundwaters from southern Nevada and eastern California.
文摘The three largest earthquakes in northern California since 1849 were preceded by increased decadal activity for moderate-size shocks along surrounding nearby faults. Increased seismicity, double-difference precise locations of earthquakes since 1968, geodetic data and fault offsets for the 1906 great shock are used to re-examine the timing and locations of possible future large earthquakes. The physical mechanisms of regional faults like the Calaveras, Hayward and Sargent, which exhibit creep, differ from those of the northern San Andreas, which is currently locked and is not creeping. Much decadal forerunning activity occurred on creeping faults. Moderate-size earthquakes along those faults became more frequent as stresses in the region increased in the latter part of the cycle of stress restoration for major and great earthquakes along the San Andreas. They may be useful for decadal forecasts. Yearly to decadal forecasts, however, are based on only a few major to great events. Activity along closer faults like that in the two years prior to the 1989 Loma Prieta shock needs to be examined for possible yearly forerunning changes to large plate boundary earthquakes. Geodetic observations are needed to focus on identifying creeping faults close to the San Andreas. The distribution of moderate-size earthquakes increased significantly since 1990 along the Hayward fault but not adjacent to the San Andreas fault to the south of San Francisco compared to what took place in the decades prior to the three major historic earthquakes in the region. It is now clear from a re-examination of the 1989 mainshock that the increased level of moderate-size shocks in the one to two preceding decades occurred on nearby East Bay faults. Double-difference locations of small earthquakes provide structural information about faults in the region, especially their depths. The northern San Andreas fault is divided into several strongly coupled segments based on differences in seismicity.
文摘This paper presents a comprehensive exploration of the complex phenomenon of homelessness in California,with a specific focus on the state’s three largest cities-Los Angeles,San Francisco,and San Diego.Against the backdrop of a high cost of living and a housing market strained by insufficient affordable options,the multifaceted nature of social diversity further complicates the landscape,leading to a widespread presence of homelessness that spans both major urban centers and rural regions.Through an in-depth examination of the distinct challenges confronting each city,ranging from housing shortages to intricate social dynamics,this study seeks to illuminate the underlying factors driving homelessness and identify potential avenues for intervention.Moreover,the paper delves into the unique vulnerabilities experienced by certain demographics within the homeless population,including veterans,families with children,and LGBTQ+individuals,highlighting the critical need for targeted solutions tailored to their specific needs.By synthesizing existing research and incorporating firsthand accounts,this research endeavor aims to contribute to a deeper understanding of homelessness in California and inform the development of comprehensive strategies aimed at fostering inclusive,sustainable communities statewide.
文摘The synchronous construction of the secondary lining during the boring of large-diameter shield faces challenges such as the design of the lining jumbo,the high requirements on the performance for the lining jumbo,the organization of the construction activities in the small and confined area,the horizontal transportation for shield boring and high safety management requirements.A super-long invert lining construction jumbo,as well as the matching California switch,is developed,which provides solution for the confliction between the invert lining construction and the horizontal transportation.The procedure and method for the synchronous operation of the shield boring and the secondary lining are developed by referring to the synchronous construction of the secondary lining during the boring of the TBMs in hard rocks.Due to the adoption of the synchronous operation of the shield boring and the secondary lining,the construction period is shortened and the construction cost is reduced.The paper can provide reference for the synchronous construction of the secondary lining in similar projects in the future.
文摘A pair of Black Oystercatchers(Haematopus bachmani)established a nest in June 2022 at“Tern Town”,an island located in Hayward,California along the eastern side of the San Francisco Bay.This is the first documented occurrence of oystercatchers successfully nesting and fledgling young in association with California Least Terns.The island provides nesting habitat for three special status species.Since 2015,and for a total of six breeding seasons,the endangered California Least Tern(Sternula antillarum browni),the threatened Western Snowy Plover(Charadrius alexandrinus nivosus)and species-of-special-concern Black Skimmer(Rynchops niger),have nested successfully,in association with American Avocet(Recurvirostra americana)and Black-necked Stilt(Himantopus mexicanus).We collected shells near the oystercatcher nest to assess their diet.Diet data showed the oystercatchers foraged on,in decreasing order of abundance,Japanese Little-necked Clams(Ruditapes philippinarum),Ribbed Mussels(Geukensia demissa),Bent-nose Clams(Macoma nasuta),Limpets(Patellogastropoda sp.)and Bay Mussels(Mytilus edulis).This new report on breeding Black Oystercatchers indicates that managing habitat for California Least Tern,Western Snowy Plover,and Black Skimmer can also benefit Black Oystercatcher.This site-specific information on breeding Black Oystercatchers supports recovery plan tasks that are consistent with managing habitat for California Least Tern,Western Snowy Plover and Black Skimmer.
文摘The California bearing ratio (CBR) test is the most widely spread method of determining the bearing strength of the pavement material and is fundamental to pavement design practice in most countries. This test is expensive, laborious and time consuming, and to overcome this, Quasi static cone penetrometer machine was fabricated and used to measure the consistency limits (liquid limit-LL, Plastic limit-PL and Plasticity index-PI), which were used to develop an empirical equation to determine CBR. Soil samples were collected and unsoaked CBR, PL, LL and PI were determined according to BS 1377 part 9 and BS 1377-2;1990. Quasi static penetration forces at 20 mm depth of penetration were also determined at consistency limits. It was found that the force of 1020 gf and 60 gf was achieved at a depth of 20 mm at PI and LL respectively. The correlation and regression analysis between consistency limits, and the experimental CBR obtained showed coefficient of determination, R<sup>2</sup> = 0.907 between CBR and all the parameters using multiple linear regression analysis (MLRA). The regression equation developed was used together with the relationship developed between the Quasi static Penetration force at consistency limits and the tested consistency limits to come up with the General Empirical Equation. Verification of the formula showed that the correlation can be used accurately to determine the un soaked CBR.