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Tropical forest regions in equatorial Africa are threatened with degradation, deforestation and biodiversity loss as a result of land-cover change. We investigated historical land-cover dynamics in unprotected forested areas of the Littoral Region in south-western Cameroon during 1975–2017, to detect changes that may influence this important biodiversity and wildlife area. Processed Landsat imagery was used to map and monitor changes in land use and land cover. From 1975 to 2017 the area of high-value forest landscapes decreased by c. 420,000 ha, and increasing forest fragmentation caused a decline of c. 12% in the largest patch index. Conversely, disturbed vegetation, cleared areas and urban areas all expanded in extent, by 32% (c. 400,000 ha), 5.6% (c. 26,800 ha) and 6.6% (c. 78,631 ha), respectively. The greatest increase was in the area converted to oil palm plantations (c. 26,893 ha), followed by logging and land clearing (c. 34,838 ha), all of which were the major factors driving deforestation in the study area. Our findings highlight the increasing threats facing the wider Littoral Region, which includes Mount Nlonako and Ebo Forest, both of which are critical areas for regional conservation and the latter a proposed National Park and the only sizable area of intact forest in the region. Intact forest in the Littoral Region, and in particular at Ebo, merits urgent protection.
An investigation was undertaken by the Bureau of Mines at College Park, Md., to determine the effect of various combinations of collimators, analyzing crystals and detectors on line intensities, line-to-backgrouhd ratios, and spectral resolution. The research showed that line broadening due to mosaic crystal surfaces was greatly reduced and line splitting from faults was eliminatedby the use of two fine collimators (0.005 inch, spacing, 4 inch length). Line intensities were reduced, but lineto- background ratios arid line profiles were substantially improved with double collimators. Pulse height discrimination resulted in marked improvement in the line-to-background ratio in the long-wave length region, 2 to 10 A, but was much less effective for shorter wave lengths.
The effect of temperature change on LiF, ADP, and EDDT analyzing crystals was studied by measuring the change In intensity of a selected X-ray spectral line while maintaining a constant 2θ position on the spectrometer. A change in interplanar spacing due to thermal expansion and contraction satisfactorily account for experimentally observed line shifts for LiF and ADP. EDDT showed a large unexplained decrease in reflectivity with increasing ambient temperature.
An equation was developed to express the change in intensity at a constant 2θ position as an exponential function of temperature. In this equation the thermal expansion coefficients of the principal axes of the crystal, the width of the spectral line at half-height, and the Bragg angle appear as factors. Intensity changes due to peak shift were tabulated for LiF, ADP, NaCl, silicon, germanium, quartz, calcite, fiuorite, and topaz.
The fluorescent excitation of long-wavelength X-ray spectra is reviewed with respect to X-ray tube target element, inherent filtration, and optimum kilovoltage. A demountable X-ray tube vacuum spectrograph designed for the determination of the light elements is described. Operation of this instrument with both secondary and combined primary—secondary excitation is evaluated. Examples from the literature are cited to show the feasibility of direct electron excitation of longwavelength spectra.
The purpose of this investigation was to develop a rapid, accurate method of analysis for small amounts of calcium in wolframite concentrates. This analysis is necessary to determine if wolframite concentrates meet the U. S. National Stockpile Specification P-57R2, which limits the calcium content to 0.2 per cent.
Because of the small depth of sample analyzed in fluorescent x-ray spectrography the calcium Kα line intensity was found to be a function of the chemical composition of the calcium-bearing particle as well as the matrix composition. This particle-conn position effect was particularly important in this analysis because the calcium may be present as a carbonate, tungstate, phosphate, etc. Three methods of sample preparation were found to eliminate the variation of calcium Kα intensity with mineralogical occurrences: (1) Reduction in particle size by extensive grinding, (2) chemical fusion wtli sodium carbonate, and (3) solution of the calcium by an add.
Determinations by all three procedures are believed to be accurate to within ± 5 per cent for more than 0.30 per cent calcium and ± 10 per cent at the 0.1-per cent level. The lower limit of detectability is in the order of 0.005-0.01 per cent.
The operating characteristics of a gas-flow proportional counter used in conjunction with a pulse-height analyzer were studied in detail. This detector was found to have a high counting efficiency for calcium Ka radiation, to have a low counting efficiency for overlapping higher order radiation and to have counting stability equivalent to Geiger tubes.
A time-sharing computer was used in conjunction with a semiconductor detector and radioisotopic sources to evaluate energy dispersion x-ray analysis for the rapid analysis of copper base alloys. The time-sharing computer served two purposes: to aid in the development of the analytical method and to simulate the action of a dedicated computer that would eventually be used as part of an on-line analytical device. Some of the general capabilities of time-sharing computers are discussed in this paper with some emphasis on the differences between the computer requirements of energy dispersive x-ray methods and conventional x-ray spectrography.
An annular source of americium 24l was used with a secondary fluorescer to excite 23 brass and bronze alloys. The 400 channel spectrum from a multichannel analyzer was recorded on paper tape. A telephone coupled teletype was used to transmit the X-ray spectrum to the central processing facility. Curve fitting and statistical analysis programs similar to those available from most commercial time-sharing computer operations were utilised as well as other programs written at this laboratory for processing digitized spectra.
Line intensity and background measurements were made on the K lines for the elements with atomic numbers 16 to 60, L lines for the elements above atomic number 42, and M lines for elements above atomic number 80. Three general classes of samples were investigated: (1) infinitely thick, (2) microgram deposits, and (3) thin layers.
These studies show that longer-wavelength L radiation may be preferable to the K series lines from the same element in the range of elements with atomic numbers 42 to 60, In particular the Lα lines are more intense than the K series lines from Class 2 and 3 samples. With Class 1 samples the Lα lines are weaker than the K series but their line-to-background ratio is superior to the K series.
M series lines show little promise for spectrochemical analysis except for elements with atomic numbers 90 to 92; for example, with uranium samples in Class 2 and 3, the very high line-to-background ratio of the UMβ1 line may have limited application.
Elements with atomic numbers from 16 to 22 are more sensitive than expected due to the very high line-to-background ratios and the reduced collimation requirements in this longwavelength region.
High-temperature X-ray diffractometer measurements by the Bureau showed that alpha-alumina expands anisotropically with expansion parallel to the c axis approximately 10% greater than that parallel to the a axis. Thermal-expansion characteristics of four different alumina samples were determined up to 1200°C; the results are presented in both tabular and graphical form. The combined random and systematic errors in the measurements are considered less than 3% above 500°C and approximately 2% at 1000°C. No differences in expansion were observed between the samples or between the heating and cooling cycles.
Critical evaluation of the literature showed that published values for thermal-expansion coefficients of single crystals vary over a range of 40% (relative values) and disagreement concerning whether expansion of alpha-alumina is isotropic or anisotropic. Systematic and experimental errors were found to be the principal factor for the variation in results, rather than differences in measuring techniques or in samples.
Published values for polycrystalline aggregates also varied. Two laboratories reported values 20–30% lower than those of the Bureau of Mines, but two other laboratories agree with the Bureau within 3–5% above 500°C.
This paper summarizes developments in the field of high-temperature X-ray diffractometers through 1959, evaluates various furnace designs, and describes briefly the X-ray diffraction facilities of the Federal Bureau of Mines.
X-ray optics, for those furnaces that have precision sample movements, are equivalent in resolution and line profile to conventional X-ray techniques. There is a 10-25% loss of intensity due to absorption of X-rays in the furnace windows, magnitude of which depends on wavelength and type of window used, and a reduction (5–40° 2θ) of useful angular range from limiting X-ray windows, radiation shielding, or the viewport for an optical pyrometer. In oxidizing atmospheres, temperatures up to 1500°C were obtained with furnaces wound with platinum—20% rhodium wire. Under nonoxidizing conditions temperatures of 1800 to 2000°C were obtained with both tantalum-foil and tungsten-wire heaters.
Accurate temperature measurement over the area and depth of samples being studied is the most difficult problem in high-temperature X-ray diffractometry. Below 500°C, there are several furnace designs which are reported to reduce thermal differentials to less than 1°C across the sample. However, at temperatures around 1000°C, there are thermal gradients of 20-30°C/cm across the sample and 100–600°C/cm through the sample holder, making thermocouple location critical. Secondary standards have been used extensively to calibrate the furnaces; however, there is disagreement concerning which are the most reliable data to use. For these reasons, plus others discussed in this report, there is a probable error in the temperature determination of ±10 to 20°C at 1000°C, with the error increasing with temperature.
Resin-loaded papers composed of approximately 50% cellulose and 50% ion-exchange or chelating resin provide an ideal matrix for many X-ray spectrographic analyses. Standards are prepared by multiple filtration of solutions of known composition through the paper to achieve quantitative collection or by the use of a radiotracer as a monitor for nonquantitative collection. Solutions prepared fram unknown samples are processed in the same manner as the standards.
Advantages of the resin-loaded papers are: reduction of interelement effects because standards and unknowns are present in a similar low X-ray absorbing matrix; physical parameters such as metallurgical history, grain size, and surface preparation are eliminated; and sampling errors are significantly reduced and sensitivity greatly increased by concentrating trace elements separated from large samples.
Application of these papers to a variety of metallurgical, geological, and water samples will be summarized. The possible use of resin-loaded papers as standards for air pollution monitoring will be examined.
The concept of using immunological strategies to boost reproductive performance in sheep and cattle is far from new, with products such as Fecundin®, which involved active immunisation against the weak androgen, androstenedione, having been released nearly 20 years ago. However, whilst effective in sheep, immunisation against androgens was not effective in inducing multiple ovulation in cattle (unpublished observations), in which the natural rate of twinning is low (<4%). The purification of inhibin in the late 1980’s and the subsequent elucidation of its role in controlling follicle stimulating hormone (FSH) release from the pituitary represented an alternative means to increase prolificacy in domestic ruminants. Intense research effort throughout the 1990’s utilising active inhibin immunisation showed that while this approach was quite successful in sheep, results in cattle were less promising due to the extreme variability of the response obtained both between animals and within a single animals across successive cycles. Further, while numerous studies have shown that with correct identification and management production of twins in cattle can lead to significant economic gains, the possibility of more than two young clearly raised welfare concerns for both sheep and cattle in terms of dystocia and post-natal welfare of both the mother and her offspring. Over recent years, however, continued research into the control of ovarian follicle development in ruminants has suggested alternate immunological strategies that could be used to modulate prolificacy in a more reliable and controllable manner.
We have recently completed an analysis that examines in detail the spatial and temporal variations in global sea-ice coverage from 26 October 1978, through 20 August 1987. The sea-icemeasurements we analyzed are derived from data collected by a multispectral, dual-polarized, constant incidence-angle microwave imager, the Scanning Multichannel Microwave Radiometer (SMMR) on board the NASA Nimbus 7 satellite. The characteristics of the SMMR have permitted a more accurate calculation of total sea-ice concentrations (fraction of ocean area covered by sea ice) than earlier single-channel instruments and, for the first time, a determination of both multiyear sea-ice concentrations and physical temperatures of the sea-ice pack. An estimate of the SMMR wintertime total ice concentration accuracy of ± 7% in both hemispheres has been obtained. As this is an improvement over the estimated accuracies of previous microwave sensors, we are able to present improved calculations of the sea-ice extents (areas enclosed by the 15% ice concentration boundaries), sea-ice concentrations, and open-water areas within the ice margins. This analysis will be published in a book, Arctic and Antarctic sea ice, 1978–1987: satellite passive microwave observations and analysis, due for publication in1992. Some highlights from the analysis are presented in this paper.
Recently reported observations of a nine-year decrease in global sea-ice extent, obtained from the Scanning Multichannel Microwave Radiometer onboard the Nimbus-7 satellite during 1978–87 and averaged with an annual running mean, have been separated into Arctic and Antarctic components. The annually-averaged global extent decrease was 2.5%. Here it is shown that the greater part of this decrease occurred in the Arctic where there was a decline of 3.5% with a goodness of fit of 0.54.
Superimposed on this decline was a small oscillation with a period of about four years and an amplitude of about 1%. A significantly smaller and statistically insignificant decrease of 1.2% with a goodness of fit of 0.03 is observed in the annually averaged Antarctic sea-ice extent. However, three large oscillations with amplitudes of about 4% and periods of about three years occurred in phase with three El Niño events.
Satellite passive microwave observations can provide unique mesoscale (25 km) information on snowpack properties; however, the mountainous terrain of the upper Colorado River basin compounds the difficulty of the problem. Nevertheless, observations of this region from the Scanning Multichannel Microwave Radiometer (SMMR) have provided unique, synoptic, mesoscale snowpack information from 1979 to 1987 on the snowpack extent. For this nine-year period, the SMMR 18 and 37 GHz brightness temperature observations, combined to form a parameter called NGR, show the average maximum snowpack extent covers 70% of the basin and occurs on water year day 130 (mid-February). The minimum snowpack extent took place in 1981 and covered 35% of the basin. The maximum snowpack extent took place in 1979 and covered 99% of the basin. Summation of the NGR values from each SMMR mesoscale pixel within the basin provides an index of the regional snowpack properties on both an intra- and inter-annual basis and exhibits behavior similar to the snowpack extent. When compared to the nine-year average, 1981 is the minimum year and 1979 is the maximum year. Furthermore, the sum over the basin of the annual maximum NGR from each pixel correlates with the annual discharge, r = 0.6. This correlation increases to 0.8 when digital elevation data are used to characterize each SMMR pixel and only the April through July discharge is used in the regression. Hence, this study combines the small scale elevation data with the mesoscale SMMR observations to investigate the basin-wide or regional snowpack characteristics and its hydrology.
Background: Cognitive Behavioural Therapy (CBT) aims to teach people skills to help them self-manage their depression. Trial evidence shows that CBT is an effective treatment for depression and individuals may experience benefits long-term. However, there is little research about individuals’ continued use of CBT skills once treatment has finished. Aims: To explore whether individuals who had attended at least 12 sessions of CBT continued to use and value the CBT skills they had learnt during therapy. Method: Semi-structured interviews were held with participants from the CoBalT trial who had received CBT, approximately 4 years earlier. Interviews were audio-recorded, transcribed and analysed thematically. Results: 20 participants were interviewed. Analysis of the interviews suggested that individuals who viewed CBT as a learning process, at the time of treatment, recalled and used specific skills to manage their depression once treatment had finished. In contrast, individuals who viewed CBT only as an opportunity to talk about their problems did not appear to utilize any of the CBT skills they had been taught and reported struggling to manage their depression once treatment had ended. Conclusions: Our findings suggest individuals may value and use CBT skills if they engage with CBT as a learning opportunity at the time of treatment. Our findings underline the importance of the educational model in CBT and the need to emphasize this to individuals receiving treatment.
During 1990 we surveyed the southern sky using a multi-beam receiver at frequencies of 4850 and 843 MHz. The half-power beamwidths were 4 and 25 arcmin respectively. The finished surveys cover the declination range between +10 and −90 degrees declination, essentially complete in right ascension, an area of 7.30 steradians. Preliminary analysis of the 4850 MHz data indicates that we will achieve a five sigma flux density limit of about 30 mJy. We estimate that we will find between 80 000 and 90 000 new sources above this limit. This is a revised version of the paper presented at the Regional Meeting by the first four authors; the surveys now have been completed.
Depression is expensive to treat, but providing ineffective treatment is more expensive. Such is the case for many patients who do not respond to antidepressant medication.
To assess the cost-effectiveness of cognitive–behavioural therapy (CBT) plus usual care for primary care patients with treatment-resistant depression compared with usual care alone.
Economic evaluation at 12 months alongside a randomised controlled trial. Cost-effectiveness assessed using a cost-consequences framework comparing cost to the health and social care provider, patients and society, with a range of outcomes. Cost-utility analysis comparing health and social care costs with quality-adjusted life-years (QALYs).
The mean cost of CBT per participant was £910. The difference in QALY gain between the groups was 0.057, equivalent to 21 days a year of good health. The incremental cost-effectiveness ratio was £14 911 (representing a 74% probability of the intervention being cost-effective at the National Institute of Health and Care Excellence threshold of £20 000 per QALY). Loss of earnings and productivity costs were substantial but there was no evidence of a difference between intervention and control groups.
The addition of CBT to usual care is cost-effective in patients who have not responded to antidepressants. Primary care physicians should therefore be encouraged to refer such individuals for CBT.