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Aim Habitat fragmentation threatens species’ persistence by increasing subpopulation isolation and vulnerability to stochastic events, and its impacts are expected to worsen under climate change. By reconnecting isolated fragments, habitat corridors should dampen the synergistic impacts of habitat and climate change on population viability. Choosing which fragments to reconnect is typically informed by past and current environmental conditions. However, habitat and climate are dynamic and change over time. Habitat suitability projections could inform fragment selection using current and future conditions, ensuring that corridors connect persistent fragments. We compare the efficacy of using current-day and future forecasts of breeding habitat to inform corridor placement under land cover and climate-change mitigation and no mitigation scenarios by evaluating their influence on subpopulation abundance, and connectivity and long-term metapopulation abundance. Our case study is the threatened orangutan metapopulation in Sabah. Location Sabah, Malaysian Borneo. Methods Using coupled niche–population models that capture a metapopulation distribution and its major processes, we forecast the effect of current-day and future-informed habitat corridor implementations under two scenarios where (1) land cover and climate change continue unabated (no mitigation) and (2) local and international cooperation mitigates their synergistic impact (mitigation). Results We show that Future-informed corridor placement maximizes long-term metapopulation abundance when human-driven land cover and climate change alter the spatio-temporal composition of suitable habitat. By contrast, there is no apparent benefit in using future forecasts of breeding habitat to inform corridor placement if conditions remain comparatively stable. For the Sabah orangutan under unabated land cover and climate change, habitat corridors should connect current-day populated eastern habitat fragments with vacant fragments in the state's west. Main conclusions The efficacy of habitat corridors can be improved by using habitat-suitability model projections to inform corridor placement in rapidly changing environments, even for long-lived, low-fecundity, philopatric species such as orangutan.

Aim:Advancement in ecological methods predicting species distributions is a crucial precondition for deriving sound management actions. Maximum entropy (MaxEnt) models are a popular tool to predict species distributions, as they are considered able to cope well with sparse, irregularly sampled data and minor location errors. Although a fundamental assumption of MaxEnt is that the entire area of interest has been systematically sampled, in practice, MaxEnt models are usually built from occurrence records that are spatially biased towards better‐surveyed areas. Two common, yet not compared, strategies to cope with uneven sampling effort are spatial filtering of occurrence data and background manipulation using environmental data with the same spatial bias as occurrence data. We tested these strategies using simulated data and a recently collated dataset on Malay civet Viverra tangalunga in Borneo.Location:Borneo, Southeast Asia.Methods:We collated 504 occurrence records of Malay civets from Borneo of which 291 records were from 2001 to 2011 and used them in the MaxEnt analysis (baseline scenario) together with 25 environmental input variables. We simulated datasets for two virtual species (similar to a range‐restricted highland and a lowland species) using the same number of records for model building. As occurrence records were biased towards north‐eastern Borneo, we investigated the efficacy of spatial filtering versus background manipulation to reduce overprediction or underprediction in specific areas.Results:Spatial filtering minimized omission errors (false negatives) and commission errors (false positives). We recommend that when sample size is insufficient to allow spatial filtering, manipulation of the background dataset is preferable to not correcting for sampling bias, although predictions were comparatively weak and commission errors increased.Main Conclusions:We conclude that a substantial improvement in the quality of model predictions can be achieved if uneven sampling effort is taken into account, thereby improving the efficacy of species conservation planning. published

In 1994 Alan Rabinowitz decried what he regarded as lackadaisical attempts by governments, NGOs and international funding agencies to conserve the Sumatran rhinoceros Dicerorhinus sumatrensis. Sixteen years on it is timely to evaluate whether his warnings were heeded. We review the current conservation status of D. sumatrensis throughout its range and the latest threats and challenges complicating efforts to conserve this species. Recent data from governments, NGOs and researchers indicate that the global population could be as low as 216, a decline from c. 320 estimated in 1995. Based on lessons learnt and expert opinions we call on decision makers to focus on two core strategies for conservation of D. sumatrensis: (1) the translocation of wild individuals from existing small, isolated or threatened forest patches into semi-in situ captive breeding programmes, and (2) a concomitant enhancement of protection and monitoring capacities in priority areas that have established these breeding facilities or have recorded relatively high population estimates and track encounter rates. At least USD 1.2 million is required to implement these strategies annually in four priority areas: Bukit Barisan Selatan and Way Kambas National Parks on Sumatra, and Danum Valley Conservation Area and Tabin Wildlife Reserve on Sabah. Given that conservation funds are rarely secure and D. sumatrensis is still in decline we call on potential donors to help secure and augment existing capacities of organizations in these four priority areas before committing resources to elucidate the status of the species in other areas such as Gunung Leuser and Taman Negara National Parks.

Problem statement: In Asia, four elephant subspecies have been identified, Elephas maximus maximus from Sri Lanka, Elephas maximus summatranus from Sumatra, Elephas maximus borneensis (based on recent DNA analysis) from Borneo and Elephas maximus indicus, from mainland Asia. The Bornean elephant has a limited distribution and is found only in the northeastern part of the island, (Malaysian Sabah and Indonesian Kalimantan). Previous estimations for the population in Sabah have ranged between 500-2000 elephants. These estimations have been carried out through a non-systematic approach, either via interview or from direct sightings or extrapolating population count data from limited sites. In order to prepare the conservation plan for this species in Sabah, there is a need to establish reliable information on their density and population size. The main objective of this study was to determine the elephant density and population size in five main elephant managed ranges in Sabah. Approach: In this study, relative distribution and spatial density of the Bornean elephant was developed and established, using a systematic line transect survey and a long term monitoring of dung decay rates. We conducted the elephant population census in Sabah between July 2007 and December 2008. Using a line-transect dung-count methodology, we surveyed 216 line transects; with a total distance of 186.12 km, in five main elephant managed ranges. Namely (i) Tabin Wildlife Reserve, (ii) Lower Kinabatangan, (iii) Central Forest, (iv) North Kinabatangan and (v) Ulu Kalumpang. Results: We presented the elephant density estimate using long term monitoring of dung decay rates. In each range, the elephant’s density varied depending on the size of the suitable habitat. The size of the suitable habitat was derived from WWF’s study report (WWF-Malaysia, 2008). Densities were analyzed following line-transect analysis guidelines and were computed using the software Distance v6.0. Conclusion: Our survey indicated that approximately 2,040 (95% CI: 1,184-3,652) elephants remain in the five main ranges in Sabah, with the largest population being in the unprotected central forests. Elephant density was highest in ranges where habitat has been removed and elephants are concentrated in remaining forest areas. These results provide new baseline data for the elephant population in Sabah.

Problem statement: Orang-utan is classified as a totally protected species and is listed as an endangered species in Borneo. The survival of this species is highly dependent on the existence and quality of the lowland forest of Sabah. However, most of the pristine habitats in the lowland area have been converted into other land use activities such as a large scale plantation. This is due to the fact that most of the lowland forests are facing a continuous degradation process that will decrease its commercial value when it comes to generating revenue to the state government. Thus, the efforts to restore the forest are very vital. The main objectives of this study include establishing the relative spatial distribution of orang-utan in order to assess and determine the effects of the forest conversions in four main wild orang-utan population landscape, demonstrating the orang-utan population movement pattern as a response to the heavy logging activities and also quantifying the effect of logging activities on the status of food trees or plant species for orang-utan in their current forest habitat. Approach: In this research, relevant features are constructed in order to study the impacts of logging and forest conversion on Orang-utan population in Borneo. These features include aerial surveys and feeding behaviors. An aerial survey on orang-utan’s nest in four out of six main forest habitats for orang-utan in Sabah has been conducted between May 2005 and June 2009 in order to map the relative distribution and spatial density of the orang-utans. This is conducted in order to determine the impacts of the forest conversion for the last 20 years upon the orang-utan spatial distribution. In this project, three series of aerial surveys, covering Malua Forest Reserve, have been conducted to demonstrate the dynamic movement and habitat utilization by the orang-utan population, due to the logging activities within the forest habitat. A long term observation of the orang-utan feeding behavior in the degraded forest in North Ulu Segama (NUS) has been also conducted to determine their feeding ecology in a logged over forest. Results: This study suggested that (i) forest conversion and logging activities have effects on the orang-utan habitat utilization and movement pattern; (ii) due to the influx of the forest conversion, some of the orang-utan in the forest reserve is concentrated in certain area, adjacent to the boundary of the forest reserve due to their movement limitation by the river network; (iii) the orang-utan population in degraded forest of NUS consumed almost different species of food plants in 2009, compared to year 1974. Conclusion: These results demonstrated that forest conversion and unsustainable logging activities are the main threat for the orang-utans conservation in Sabah. Therefore, the conservation of orang-utan populations are not guaranteed by the establishment of more protected area, but by ensuring that more forest habitats can be managed in sustainable way in order to avoid further forest degradation and to ensure their habitats remain connected to the large forest landscape.

Problem statement: The lowland forest of Sabah is the most important h abitat for orangutans and pygmy elephants. This is shown in the WWF-Malaysia's elephant tracking programme in which satellite-based Global Position System (GP S) collar devices are used to monitor their movement and the range of their habitats, as well a s an aerial survey on orangutan's nest is performed to determine the spatial distribution pattern. We o bserved the activities of both species and we found that these species stay inside lowland forests with on flat ground or with gentle slopes, below 500 m elevation, which is mostly covered by natural fores t. The density of orangutan's population was estimated to be higher in a certain location in nat ural lowland forests where the soils are more ferti le. A suitable long term habitat for both species is loca ted in the lowland dipterocarp forests. However, mo st of the pristine habitats in the lowland area have b een converted into other land use activities such a s a large scale plantation. This is due to the fact tha t most of the lowland forests are facing a continuo us degradation process that will decrease its commerci al value when it comes to generating revenue to the state government. As a result, the efforts to resto re the forest are very vital. Approach: This study described the technical and biological aspects in t he forest restoration planning, prioritizing, implementation and monitoring process, integrated with the data on habitat utilization by orangutan in lowland degraded dipterocarp forest. Key habitats f or orangutans were identified, forest condition wer e mapped and field works are carried out using a plot sampling technique to identify the diversity and density of the forest (current and potential), in o rder to support the forest restoration planning. A proper database on forest restoration and tree main tenance planning had been developed to enable the monitoring process. Results: This study outlined some of the findings that incl ude the main challenges that were faced in the forest restoration programme in North Ulu Segama (NUS), which could be used as lessons and guideline in the future. Conclusion: A long term monitoring programme is important in order to have a successful forest restoration progr amme as well as to have the opportunity to study th e impact of this restoration on the behavior of orang utan as a result of their adaptation to the new for est structure.

Three of Malaysia’s endangered large mammal species are experiencing contrasting futures. Populations of the Sumatran rhino (Dicerorhinus sumatrensis) have dwindled to critically low numbers in Peninsular Malaysia (current estimates need to be revised) and the state of Sabah (less than 40 individuals estimated). In the latter region, a bold intervention involving the translocation of isolated rhinos is being developed to concentrate them into a protected area to improve reproduction success rates. For the Asian elephant (Elephas maximus), recently established baselines for Peninsular Malaysia (0.09 elephants/km2 estimated from one site) and Sabah (between 0.56 and 2.15 elephants/km2 estimated from four sites) seem to indicate globally significant populations based on dung count surveys. Similar surveys are required to monitor elephant population trends at these sites and to determine baselines elsewhere. The population status of the Malayan tiger (Panthera tigris jacksoni) in Peninsular Malaysia, however, remains uncertain as only a couple of scientifically defensible camera-trapping surveys (1.66 and 2.59 tigers/100 km2 estimated from two sites) have been conducted to date. As conservation resources are limited, it may be prudent to focus tiger monitoring and protection efforts in priority areas identified by the National Tiger Action Plan for Malaysia. Apart from reviewing the conservation status of rhinos, elephants and tigers and threats facing them, we highlight existing and novel conservation initiatives, policies and frameworks that can help secure the long-term future of these iconic species in Malaysia.

SummaryResponses of biodiversity to changes in both land cover and climate are recognized [1] but still poorly understood [2]. This poses significant challenges for spatial planning as species could shift, contract, expand, or maintain their range inside or outside protected areas [2–4]. We examine this problem in Borneo, a global biodiversity hotspot [5], using spatial prioritization analyses that maximize species conservation under multiple environmental-change forecasts. Climate projections indicate that 11%–36% of Bornean mammal species will lose ≥30% of their habitat by 2080, and suitable ecological conditions will shift upslope for 23%–46%. Deforestation exacerbates this process, increasing the proportion of species facing comparable habitat loss to 30%–49%, a 2-fold increase on historical trends. Accommodating these distributional changes will require conserving land outside existing protected areas, but this may be less than anticipated from models incorporating deforestation alone because some species will colonize high-elevation reserves. Our results demonstrate the increasing importance of upland reserves and that relatively small additions (16,000–28,000 km2) to the current conservation estate could provide substantial benefits to biodiversity facing changes to land cover and climate. On Borneo, much of this land is under forestry jurisdiction, warranting targeted conservation partnerships to safeguard biodiversity in an era of global change.

Background: Southeast Asian deforestation rates are among the world’s highest and threaten to drive many forest-dependent species to extinction. Climate change is expected to interact with deforestation to amplify this risk. Here we examine whether regional incentives for sustainable forest management will be effective in improving threatened mammal conservation, in isolation and when combined with global climate change mitigation.\ud Methodology/Principal Findings: Using a long time-series of orangutan nest counts for Sabah (2000–10), Malaysian Borneo, we evaluated the effect of sustainable forest management and climate change scenarios, and their interaction, on orangutan spatial abundance patterns. By linking dynamic land-cover and downscaled global climate model projections, we determine the relative influence of these factors on orangutan spatial abundance and use the resulting statistical models to identify habitat crucial for their long-term conservation. We show that land-cover change the degradation of primary forest had the greatest influence on orangutan population size. Anticipated climate change was predicted to cause reductions in abundance in currently occupied populations due to decreased habitat suitability, but also to promote population growth in western Sabah by increasing the suitability of presently unoccupied regions.\ud Conclusions/Significance: We find strong quantitative support for the Sabah government’s proposal to implement sustainable forest management in all its forest reserves during the current decade; failure to do so could result in a 40 to 80 per cent regional decline in orangutan abundance by 2100. The Sabah orangutan is just one (albeit iconic) example of a forest-dependent species that stands to benefit from sustainable forest management, which promotes conservation of existing forests.

BackgroundHome range is defined as the extent and location of the area covered annually by a wild animal in its natural habitat. Studies of African and Indian elephants in landscapes of largely open habitats have indicated that the sizes of the home range are determined not only by the food supplies and seasonal changes, but also by numerous other factors including availability of water sources, habitat loss and the existence of man-made barriers. The home range size for the Bornean elephant had never been investigated before.Methodology/principal findingsThe first satellite tracking program to investigate the movement of wild Bornean elephants in Sabah was initiated in 2005. Five adult female elephants were immobilized and neck collars were fitted with tracking devices. The sizes of their home range and movement patterns were determined using location data gathered from a satellite tracking system and analyzed by using the Minimum Convex Polygon and Harmonic Mean methods. Home range size was estimated to be 250 to 400 km(2) in a non-fragmented forest and 600 km(2) in a fragmented forest. The ranging behavior was influenced by the size of the natural forest habitat and the availability of permanent water sources. The movement pattern was influenced by human disturbance and the need to move from one feeding site to another.Conclusions/significanceHome range and movement rate were influenced by the degree of habitat fragmentation. Once habitat was cleared or converted, the availability of food plants and water sources were reduced, forcing the elephants to travel to adjacent forest areas. Therefore movement rate in fragmented forest was higher than in the non-fragmented forest. Finally, in fragmented habitat human and elephant conflict occurrences were likely to be higher, due to increased movement bringing elephants into contact more often with humans.

It was observed that in a particular open-pit mine, failure of the front and rear suspensions of a particular model of dump truck frequently occurs before the scheduled replacement of the parts. The Weibull distribution is used to model the time to failure of these components. Maximum likelihood estimators of the parameters are obtained and used to find a more appropriate replacement time.

The origin of Borneo's elephants is controversial. Two competing hypotheses argue that they are either indigenous, tracing back to the Pleistocene, or were introduced, descending from elephants imported in the 16th–18th centuries. Taxonomically, they have either been classified as a unique subspecies or placed under the Indian or Sumatran subspecies. If shown to be a unique indigenous population, this would extend the natural species range of the Asian elephant by 1300 km, and therefore Borneo elephants would have much greater conservation importance than if they were a feral population. We compared DNA of Borneo elephants to that of elephants from across the range of the Asian elephant, using a fragment of mitochondrial DNA, including part of the hypervariable d-loop, and five autosomal microsatellite loci. We find that Borneo's elephants are genetically distinct, with molecular divergence indicative of a Pleistocene colonisation of Borneo and subsequent isolation. We reject the hypothesis that Borneo's elephants were introduced. The genetic divergence of Borneo elephants warrants their recognition as a separate evolutionary significant unit. Thus, interbreeding Borneo elephants with those from other populations would be contraindicated in ex situ conservation, and their genetic distinctiveness makes them one of the highest priority populations for Asian elephant conservation., Comparison between DNA sequences of Borneo elephants with those of other Asian elephants settles a longstanding dispute about the origins of these endangered animals

Accelerated testing is often used to gauge the reliability of a product before it is released to the market. Warranty data provide valuable additional information about the reliability of a product and its constituent components via field data. In this study, warranty data provided by an Australian automobile manufacturer is used. This article considers the need to clean the data before commencing any analysis. It discusses the distribution of warranty claims and the use of warranty data to model the reliability of elemental components of an automobile. Various model options are considered before suitable modelling is adopted. The reality of modelling the reliability of a vehicle containing a large number of components is considered and a suitable method is adopted. Verification of the reliability modelling is made by comparing an estimated warranty cost with the actual cost. References Blischke, W. R., Karim, M. R. and Murthy, D. N. P. Warranty Data Collection and Analysis . Springer, London, 2011. Blischke, W. R. and Murthy, D. N. P. Warranty Cost Analysis . Marcel Dekker, Inc, New York, 1994. Blischke, W. R. and Murthy, D. N. P. Reliability: Modelling, Prediction, and Optimisation . John Wiley and Sons, New York, 2000. Campean, I. F. and Brunson, D. Reliability modelling using warranty data. International Conference on Statistics and Analytical Methods in Automotive Engineering . IMechE Conference Transactions 2002, 225--236. Cox, D. R. Renewal Theory . Chapman and Hall, New York, 1982. Cox, D. R. and Oakes, D. Analysis of Survival Data . Chapman and Hall, London, 1984. Hill, V. L. and Blischke, W. R. An assessment of alternative models in warranty analysis. Journal of Information and Optimization Sciences , 8 , 1987, 33--55. Iskandar, B. P. and Blischke, W. R. Reliability and Warranty Analysis of a Motorcycle Based on Claims Data. In Case Studies in Reliability and Maintenance (eds W. R. Blischke and D. N. P. Murthy.) John Wiley and Sons, Hoboken, NJ, USA, 2003, 623--656. doi:10.1002/0471393002.ch27 Lawless, J. F. Statistical Models and Methods for Lifetime Data . John Wiley and Sons, New York, 1982. Lawless, J. F., Hu, J. and Cao, J. Methods for the estimation of failure distributions and rates from automobile warranty data. Lifetime Data Analysis , 1 , 1995, 227--240. Lu, M. Automotive reliability prediction based on early field failure warranty data. Quality And Reliability Engineering International , 14 , 1998, 103--108. 3.0.CO;2-5">doi:10.1002/(SICI)1099-1638(199803/04)14:2 3.0.CO;2-5 Majeske, K. D. Evaluating product and process design changes with warranty data. International Journal of Production Economics , 50 , 1997, 79--89. doi:10.1016/S0925-5273(97)00034-0 Majeske, K. D. and Herrin, G. D. Determining the warranty benefits for automobile design changes. Proceedings Annual Reliability and Maintainability Symposium , 1998, 94--99. http://ieeexplore.ieee.org/xpls/abs\protect \global \let \OT1\textunderscore \unhbox \voidb@x \kern .06em\vbox {\hrule width.3em}\OT1\textunderscore all.jsp?arnumber=653636andtag=1 Nelson, W. Applied Life Data Analysis . John Wiley and Sons, New York, 1982. Rai, B. and Singh, N. Hazard rate estimation from incomplete and unclean warranty data. Reliability Engineering and System Safety , 81 , 2003, 79--92. doi:10.1016/S0951-8320(03)00083-8 Singh, N. and Rai, B. K. Reliability Analysis and Prediction with Warranty Data: Issues, Strategies, and Methods . CRC Press, 2009. doi:10.1201/9781439803264 Summit, R. Estimating the reliability model parameters through a simulation of warranty claims: How much data is needed? ANZIAM Journal , 53 , 2011. http://journal.austms.org.au/ojs/index.php/ANZIAMJ/article/view/5114 Tijms, H. C. Stochastic Models: An Algorithmic Approach . John Wiley and Sons, New York, 1994. Xie, M. On the Solution of Renewal-Type Integral Equations. Communications in Statistics , 18 , 1989, 281--293. doi:10.1080/03610918908812760

Manufactured goods are put through a quality control process that ensures an acceptable reliability level before being released to the public. However, manufacturing processes can change over time, which may affect the quality of a product. Warranty claims provide an opportunity to obtain feedback on the manufacturing process. In this study, a Weibull failure model is used to simulate the occurrence of warranty claims. The parameters of the Weibull model used to generate the data are to be estimated from the simulated warranty claims. The length of time required to obtain accurate parameter estimates is examined. The study is based on claims arising from the failure of a single component, but the techniques can also be used for a simple product or a subsystem of a more complex product that can be suitably modelled by a Weibull distribution. Our study shows that at least two years of data are required to obtain acceptable estimates of the Weibull parameters.

This article describes a laboratory supplementary program that was integrated into a traditional mining engineering mathematics unit. The practical classes consisted of computer investigations designed to help develop mathematical concepts. The program described here was mainly web based and did not directly rely on a computer algebra system for its implementation. An evaluation of the program is included. References S. Cunningham. The visualization environment for mathematics education. In Visualization in Teaching and Learning Mathematics , ed. W. Zimmermann and S. Cunningham, 67--76. USA, Mathematical Association of America, 1991. A. Franco, P. Franco, A. Garcia, F. Garcia, F. J.Gonzalez, S. Hoya, G. Rodriguez, and A. de la Villa. Learning calculus of several variables with new technologies. The International Journal of Computer Algebra in Mathematics Education , 7 (4), 295--309, 2000. B. E. Garner and L. E. Garner. Retention of concepts and skills in traditional and reformed applied calculus. Mathematics Education Research Journal , 13 (3), 165--184, 2001 S. Habre. Visualization enhanced by technology in the learning of multivariate calculus. The International Journal of Computer Algebra in Mathematics Education , 8 (2), 115--130, 2001. B. H. Hallet. Visualization and calculus reform. In Visualization in Teaching and learning Mathematics , ed. W. Zimmermann and S. Cunningham, 121--126, 1991. USA, Mathematical Association of America F. Marton and R. Saljo. Approaches to learning. In eds. F. Marton, D. Hounsell and N. Entwistle, The Experience of Learning , 36--55, 1984. Scottish Academic Press, Edinburgh. R. Moreno and R. Mayer. Verbal redundancy in multimedia learning; When reading helps listening. Journal of Educational Psychology , 94 (1), 153--163, 2002. L. D. Murphy. Computer algebra systems in calculus reform, MSTE, University of Illinois at Urbana-Champaign, 1999. http://mste.illinois.edu/users/Murphy/Papers/CalcReformPaper.html M. Pemberton. Integrating web-based maple with a first year calculus and linear algebra course. Proceedings of the 2nd International Conference on the Teaching of Mathematics , Hersonissos, Greece, July 2002. http://www.math.uoc.gr/ ictm2/Proceedings/pap316.pdf R. Pierce and K. Stacey. Observations on students' responses to learning in a cas environment. Mathematics Education Research Journal , 13 (1), 28--46, 2001. M. D. Roblyer. Integrating Educational Technology Into Teaching (4th Ed.), 2006. Pearson, New Jersey, USA. J. Stewart. Calculus (5th Ed.), 2003. Brooks/Cole, Belmont, USA. E. J. Tonkes, B. I. Loch and A. W. Stace. An innovative learning model for computation in first year mathematics. International Journal of Mathematical Education in Science and Technology , 36 (7), 751--759, 2005. L. M. Villarreal. A step in the positive direction: Integrating a computer laboratory component into developmental algebra courses. Mathematics and Computer Education , 37 (1), 72--78, 2003. S. Vinner. The pseudo-conceptual and the pseudo-analytical thought processes in mathematics learning. Educational Studies in Mathematics , 34 (2), 97--129, 1997. P. Vlachos and A.K. Kehagias. A computer algebra system and a new approach for teaching business calculus. The International Journal of Computer Algebra in Mathematics Education . 7 (2), 87--104, 2000.

Under certain simplified but realistic physical assumptions, the basic data from continuous velocity surveys in wells can be used to simulate the variations in acoustic impedance in the ground which give rise to seismic reflections. An analogue computer is described which makes use of the basic well data to produce synthetic seismic records which resemble actual seismograms from shothole explosions. This process provides an interesting insight into the requisite physical conditions, as well as the physical processes, whereby seismic reflections are set up in the earth. The close relationship between seismograms and well logs is brought out. Illustrations are given of field results.

Summary Groundwater derived from the Lower Greensand of the London Basin has been ‘dated’ by the use of tritium and carbon-14 techniques. The data indicate that replenishment from the northern outcrop is feasible but that movement from the southern outcrop is extremely slow and possibly restricted.

In seismograph computations assuming a uniform rate of velocity increase with depth, a “wave front‐wave path” chart consisting of sets of orthogonal circles is often used. The present paper describes a transformation by which the wave fronts become a set of concentric circles with the wave paths as radii, while the cartesian coordinates representing vertical and horizontal distances in the ground become orthogonal circles.

The various types of instruments for gravity measurements are briefly discussed. The theory of an inverted pendulum of the "Holweck-Lejay" type with an elastic mounting at its base is given, and an instrument of this design, ninety times as sensitive to differences in gravity as an ordinary pendulum, is described. The theory of the interpretation of gravity data is discussed. The results of gravity observations along a profile across the Los Angeles Basin and San Gabriel Mountains are given. From this data together with geologic data and that obtained from a reflection seismograph survey, a hypothetical structure section along the profile is constructed. The outstanding features of this section are the presence of a basin of Tertiary sediments about thirty thousand feet deep, and the increasing predominance of relatively lighter rocks under the San Gabriel Mountains and Mojave Desert. This last feature is in accord with the concept of "regional isostatic compensation."

The area discussed in this report lies on the north side of the Santa Monica Mountains, bordering on the San Fernando Valley. It includes the region around the Encino Country Club and Encino Reservoir, and extends from Ventura Boulevard on the North to a short distance south of Mulholland Highway. The accompanying sketch map shows the location of the area, and its relation to the major features of Southern California. It is easily accessible from Los Angeles or Pasadena by Ventura Boulevard or Mulholland Highway. Very excellent Los Angeles County maps (2,000 feet to the inch, 25 ft. C.I.) are available for the region, in the form of the U.S.G.S. Van Nuys and Reseda quadrangles. Fairchild Aerial Surveys of Los Angeles have also made a mosaic aerial map of this locality and the remainder of the Santa Monica. Mountains. The mapping for this report was done entirely on the aerial map, which proved highly satisfactory, allowing contacts and other features to be located very accurately. The scale used was 1500 feet to the inch. Mapping was made difficult by several features. Most of the region is covered by very heavy brush, which is all but impassable. Accurate mapping is very slow and laborious. In the valley north of the Encino Country Club, contact and exposures are largely covered by alluvium, making exact mapping impossible. Also this fact coupled with the similarity in lithology between parts of the Modelo and Topanga formations makes it difficult to find the Modelo-Topanga contact. One helpful feature is that the Modelo is usually free from brush and covered by grass, which greatly facilitates mapping. An attempt was made to map a small area accurately rather than a larger one roughly. Hence the map represents only an area about three miles square, and of this the mapping west of the eastern border of the Encino Reservoir by Holzman. Also the mapping of the Modelo-Topanga contact was done jointly with Holzman. Part of this area was included in Kew' s report, U.S.G.S. Bul. 753. Also the area is included in Hoot's report on the Santa Monica Mountains, now in press as a U.S.G.S. bulletin. The mapping of this report seems to agree in larger details with that of Hoots, but differs slightly from that of Kew as brought out later. This area overlaps in part that covered in Scharf's Senior Thesis. The area to the west has been mapped by Holzman, and that south by Crossman.