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Computer-based surgical training simulators are instrumental in skill-based training and performance measurement. However, to date, the educational employment of these tools lacks empirically founded insights and effective practical guidelines. This study examined surgical residents during computer-based simulator training of basic laparoscopic surgical skills. The quantitative analysis of residents' performance averages from training onset to completion produced mixed results, revealing skill improvements as well as decreases, depending on the parameter. The results obtained from the simulator parameters and questionnaires showed that residents with either prior laparoscopic experience or gaming experience significantly outperformed their colleagues. Based on feedback and video-recorded performance analysis, the study concluded that autonomous training with the simulator is not sufficient for developing a minimum standard of performance. Residents need an adequate level of content-based feedback and supervisor support during training. We advise a more detailed and pedagogically informative measurement and feedback system, including specialist-instructor guidance, be developed.

Agriculture plays a central role in achieving most Sustainable Development Goals (SDGs). Sustainable intensification (SI) of agriculture has been proposed as a promising concept for safeguarding global food security, while simultaneously protecting the environment and promoting good quality of life. However, SI often leads to context-specific sustainability trade-offs. Operationalising SI thus needs to be supported by transparent sustainability assessments. In this article, we propose a general systematic approach to developing context-specific frameworks for integrated sustainability assessment of agricultural intensity change. Firstly, we specify a comprehensive system representation for analysing how changes in agricultural intensity lead to a multitude of sustainability outcomes affecting different societal groups across geographical scales. We then introduce a procedure for identifying the attributes that are relevant for assessment within particular contexts, and respective indicator metrics. Finally, we illustrate the proposed approach by developing an assessment framework for evaluating a wide range of intensification pathways in Europe. The application of the approach revealed processes and effects that are relevant for the European context but are rarely considered in SI assessments. These include farmers' health, workers' living conditions, cultural heritage and sense of place of rural communities, animal welfare, impacts on sectors not directly related to agriculture (e.g., tourism), shrinking and ageing of rural population and consumers' health. The proposed approach addresses important gaps in SI assessments, and thus represents an important step forward in defining transparent procedures for sustainability assessments that can stimulate an informed debate about the operationalisation of SI and its contribution towards achieving SDGs. • We propose an approach to develop context-specific frameworks for SI assessment. • We apply the approach for developing a framework for assessing SI in Europe. • We identify how changes in agricultural intensity affect sustainability outcomes. • These sustainability outcomes affect distinct societal groups at different scales. • The approach revealed sustainability dimensions rarely considered in SI assessments. [ABSTRACT FROM AUTHOR]

Author(s): P. C. Thomas (corresponding author) [1]; J. W. Armstrong [2]; S. W. Asmar [2]; J. A. Burns [1]; T. Denk [3]; B. Giese [4]; P. Helfenstein [1]; L. Iess [...]

To better understand the negative polarization and brightness opposition effects observed on airless celestial bodies, we carried out simultaneous photometric and polarimetric measurements of laboratory samples that simulate the structure of planetary regoliths. Computer modeling of shadow-hiding and coherent backscatter in regolith-like media are also presented. The laboratory investigations were carried out with a photometer/polarimeter at phase angles covering 0.2[degrees]-4[degrees] and wavelengths of 0.63 and 0.45 [micro]m. We studied samples that characterize a variety of microscopic structures and albedos. A particle-size dependence of the negative branch of polarization for powdered dielectric surfaces was found. Colored samples such as a powder [Fe.sub.2][O.sub.3] exhibit a very prominent wavelength dependence of the photometric and polarimetric opposition phenomena. Metallic powders usually exhibit a wide branch of the negative polarization independent of the size of particles. For fine dielectric powders, both opposition phenomena become more prominent when the samples were compressed. Our computer modeling based on ray tracing in particulate media shows that shadow-hiding affects the negative polarization only in combination with the coherent backscatter enhancement. Modeling reveals that scattering orders higher than second contribute to negative polarization even in dark particulate surfaces. Our model qualitatively reproduces the effects of varying sample-compression that we observed in the laboratory. Our experimental and computer modeling studies mutually confirm that the degree of polarization for highly reflective dielectric surfaces depends not only on phase angle but also on surface tilt. Even at exactly zero phase the degree of polarization for tilted surfaces can be nonzero. A tilt of the surface normal to the scattering plane gives a parallel shift of the negative polarization branch to large values of [absolute value of P]. The tilt in the perpendicular plane gives the same shift in the direction of positive polarization. At exactly zero phase angle, a celestial body of irregular shape can exhibit nonzero polarization even in integral polarimetric observations. Key Words: regolith; polarimetry, photometry; radiative transfer.

We present near-infrared spectrometer (NIS) observations (0.8 to 2.4 [micro]m) of the S-type asteroid 433 Eros obtained by the NEAR Shoemaker spacecraft and report results of our Hapke photometric model analysis of data obtained at phase angles ranging from 1.2 [degrees] to 111.0 [degrees] and at spatial resolutions of 1.25 x 2.5 to 2.75 x 5.5 km/spectrum. Our Hapke model fits successfully to the NEAR spectroscopic data for systematic color variations that accompany changing viewing and illumination geometry. Model parameters imply a geometric albedo at 0.946/[micro]m of 0.27 [+ or -] 0.04, which corresponds to a geometric albedo at 0.550 [micro]m of 0.25 4 [+ or -] 0.05. We find that Eros exhibits phase reddening of up to 10% across the phase angle range of 0-100 [degrees]. We observe a 10% increase in the 1-[micro]m band depth at high phase angles. In contrast, we observe only a 5% increase in continuum slope from 1.486 to 2.363 [micro]m and essentially no difference in the 2-[micro]m band depth at higher phase angles. These contrasting phase effects imply that there are phase-dependent differences in the parametric measurements of 1- and 2- [micro]m band areas, and in their ratio. The Hapke model fits suggest that Eros exhibits a weaker opposition surge than either 951 Gaspra or 243 Ida (the only other S-type asteroids for which we possess disk-resolved photometric observations). On average, we find that Eros at 0.946 [micro]m has a higher geometric albedo and a higher single-scatter albedo than Gaspar or Ida at 0.56 [micro]m; however, Eros's single-particle phase function asymmetry and average surface macroscopic roughness parameters are intermediate between Gaspra and Ida. Only two of the five Hapke model parameters exhibit a notable wavelength dependence: (1) The single-scatter albedo mimics the spectrum of Eros, and (2) there is a decrease in angular width of the opposition surge with increasing wavelength from 0.8 to 1.7 [micro]m. Such opposition surge behavior is not adequately modeled with our shadow-hiding Hapke model, consistent with coherent backscattering phenomena near zero phase. Key Words: asteroid; photometry; spectrophotometry; asteroid surfaces; NEAR; 433 Eros.

During Galileo's G7 orbit, the Solid State Imaging (SSI) camera acquired pictures of the spacecraft shadow point on Europa's surface as well as a comparison set of images showing the same geographic region at phase angle [Alpha] = 5 [degrees]. Coverage, obtained at three spectral bandpasses (VLT, 0.41 [[micro]meter], GRN, 0.56 [[micro]meter]; and 1MC, 0.99 [[micro]meter]) at a spatial resolution of 404 m/pixel, shows a 162 x 220-km region of Europa's surface located at 30 [degrees] N, 162 [degrees] W. We have used these images to measure the near-opposition spectrophotometric behavior of four primary europan terrain materials: IR-bright icy material, IR-dark icy material, dark lineament material, and dark spot material. The high spatial resolution of the G7 images reveal low-albedo materials in dark spots that are among the darkest features (17% albedo at 0.56 [[micro]meter] and 5 [degrees] phase) yet found on icy Galilean satellites. While material of comparable albedo is found on Ganymede and Callisto, low-albedo europan materials are much redder. All europan surface materials exhibit an opposition effect; however, the strength of the effect, as measured by the total increase in reflectance as phase angle decreases from [Alpha] = 5 [degrees] to [Alpha] = 0 [degrees], varies among terrains. The opposition effects of IR-bright icy and IR-dark icy materials which dominate Europa's surface are about 1.5 times larger than predicted from pre-Galileo studies. Low-albedo materials in dark spots exhibit unusually intense opposition effects (up to four times larger than bright icy europan terrains), consistent with the presence of a strong shadow-hiding opposition surge. The strengths of the opposition surges among average europan terrains systematically vary with terrain albedo and can be explained in terms of the simultaneous contributions of shadow-hiding and coherent-backscatter to the total opposition effect. Coherent backscatter introduces a narrow angular contribution ( Key Words: Europa; photometry; regolith; spectrophotometry; ices; albedo; spectra; geological processes; Galileo; Voyager.

Four distinct classes of lineaments can be described on the basis of Galileo's improved spectral and spatial coverage of Europa: (1) incipient cracks are narrow (

We have modeled Ganymede's polar regions as a frost layer overlying typical non-polar materials using a two-layer photometric model. The optical depth of the overlying layer is found to increase from a few tenths at the cap boundary to more than four at the poles. Such an increase is consistent with the predictions of Johnson's (1985) sputtering model but not with those of thermal migration models of the formation of Ganymede's polar caps. If the frost forms a distinct layer, it must be physically thin - on the order of millimeters or less - particularly near the cap boundary. Therefore, the mechanism responsible for its formation must be ongoing since impact gardening would destroy such a thin layer on short time scales. Interestingly, the photometric properties of the layer are similar to those of the surface of Europa.

Among the well-imaged small satellites and asteroids, Deimos displays a unique surface: very smooth with global-scale albedo features. We have examined the disk-resolved photometry of Deimos using Viking Orbiter images for clues to its distinctive appearance. Hapke parameters were fit to characterize the phase behavior and to compute normal reflectance. The opposition surge amplitude ([B.sub.0]) is smaller for Deimos than for Phobos. Outside the range of the opposition effect the two martian satellites have similarly shaped phase curves, but Deimos is about 20-30% brighter than Phobos from 10 [degrees]-80 [degrees] phase. The calculated mean normal reflectance of Deimos ([[Lambda].sub.eff] = 0.54 [[micro]meter]) is 0.068 [+ or -] 0.007. The brighter and darker areas on Deimos exhibit constant contrast between 0.6 [degrees] and 81 [degrees] phase; this characteristic allows a calculation of the range of normal reflectances over most of its surface, nearly all of which values are between 0.06 and 0.09. The trailing side of Deimos has a larger relative distribution of the brighter material, and is on average about 10% brighter than the leading side. The mean normal reflectance cannot be formally distinguished from that of Phobos (0.071 [+ or -] 0.012; Simonelli, D. P., M. Wisz, A. Switala, D. Adinolfi, J. Veverka, P. C. Thomas, and P. Helfenstein 1996. Submitted to Icarus). Although the statistical distribution of normal reflectances on the two satellites is similar, the geography of the albedo variations is very different. Deimos has gradational changes in albedo downslope from ridge crests, primarily manifested in long albedo 'streamers.' On Phobos there is a more patchy global distribution of albedos, apparently related to ejecta from the large crater Stickney. Because of the similarity of mean density, spectral properties, mean normal reflectance, the range of normal reflectance, and phase function outside the opposition effect, Deimos appears to be made of materials with compositions very similar to those on Phobos, although the apparent wider distribution of ejecta on Deimos has been cited as indicating a greater role for strength scaling in cratering on Deimos (Lee, S. W., P. Thomas, and J. Veverka 1986. Icarus 68, 77-86). Simple modeling of the formation of the albedo patterns by gardening, creep, and 'weathering' of bright material from crater rims suggests that impact gardening contributes very little to the motion of the material downslope, and that vertical mixing and/or 'weathering' must be important in addition to an unspecified creep process. The distinction of Deimos is primarily in the smooth surface that allows a particularly large scale of downslope movement of regolith on very gentle slopes. This smoothness is most easily explained by the effects from impact formation of a 10-km concavity at high southern latitudes in the latter half of Deimos' surface history. This impact scar is relatively much larger than is the crater Stickney on Phobos. The effects of this large impact probably include blanketing by an average of nearly 200 m of ejecta, but also may include seismic erasing of craters similar to that proposed for Ida by Asphaug et al. (Asphaug, E., J. M. Moore, D. Morrison, W. Benz, and R. A. Sullivan 1996. Icarus 120, 158-184).

Galileo's flyby of 243 Ida in August 1993 led to the discovery of a small satellite, Dactyl, some 85 km from the asteroid's center. From Earth at mean opposition, the satellite is a V = +20.3 mag object (some 6.7 magnitudes fainter than Ida). Forty-seven images of the satellite at 18 different observing times were played back, including one multicolor sequence in which the satellite is resolved adequately to distinguish surface markings ([approximately]105 m/pxl) and three higher resolution single-color views (89, 39, and 24 m/pxl). The satellite, mean radius = 0.7 km, is an elongated, but not angular body with principal diameters of 1.6 x 1.4 x 1.2 km. In the highest resolution view, the longest axis points approximately in the direction of Ida, and its shortest axis is perpendicular to the orbital plane. The spin period is slow (> 8 hr?) and may be synchronous. The satellite shows no conspicuous sharp edges and is much less irregular in shape than Ida. Limb profiles are remarkably smooth over distances of 200-300 m. The geometric albedos of the two objects are similar (0.20 vs 0.21), as are the 0.4-1.0-[[micro]meter] colors. Like Ida, Dactyl is an S-asteroid, but has a slightly deeper 1-[[micro]meter] band than Ida (by 5-8%). While no identical regions (in color) are seen on Ida, the color difference is consistent with color variations reported within the Koronis family and may be due to a slightly higher pyroxene/olivine ratio on the satellite. More than a dozen craters ranging from [less than or approximately]90 to 280 m diameter are visible in the best image (39 m/pxl at 47 [degrees] phase). The largest contains an off-centered, positive relief feature some 75 m across. The image includes an intriguing crater chain, but no grooves, ridges, or sharp edges are evident. In terms of limb roughness, Dactyl is much smoother than Ida, but comparable to the two satellites of Mars, Phobos and Deimos. While the satellite's origin is uncertain, a likely scenario would have the satellite date from the breakup of the Koronis family. It is interesting that crater densities on the satellite are similar to those on Ida itself.

Galileo SSI color data between 0.4 and 1.0 [[micro]meter] demonstrate that both Ida and Dactyl are S-type asteroids with similar, but distinct spectra. Small but definite color variations are also observed on Ida itself and involve both the blue part of the spectrum and the depth of the 1-[[micro]meter] pyroxene-olivine band. Ida's surface can be classified into two color terrains: Terrain A has a shallower 1-[[micro]meter] absorption and a steeper visible red slope than does Terrain B. Qualitatively, the color-albedo systematics of these two terrains follow those noted for color units on Gaspra and the variations in 1-[[micro]meter] band depth with weathering described by Gaffey et al. (Gaffey, M. J., J. F. Bell, R. H. Brown, T. H. Burbine, J. Piatek, K. L. Reed, and D. A. Chaky 1993. Icarus 106, 573-602). Terrain A, with its slightly lower albedo, its shallower 1-[[micro]meter] band, and its slightly steeper visible red slope relative to Terrain B could be interpreted as the 'more processed,' 'more mature,' or the 'more weathered' of the two terrains. Consistent with this interpretation is that Terrain A appears to be the ubiquitous background on most of Ida, while Terrain B is correlated with some small craters as well as with possible ejecta from the 10-km Azzurra impact structure. Because of these trends, it is less likely that differences between Terrains A and B are caused by an original compositional inhomogeneity within the body of Ida, although they do fall within the range known to occur within the Koronis family. The spectrum of Dactyl is similar to, but definitely different from, that of Terrain B on Ida. It does not conform to the pattern that obtains between the colors and albedos of Terrains A and B: the satellite's 1-[[micro]meter] band is deeper than that of Terrain B, but its albedo is lower, rather than higher. By itself, the deeper band depth could be interpreted, following Gaffey et al., to mean that Dactyl is a less weathered version of Terrain B on Ida, but such an interpretation is at odds with Dactyl's redder spectral slope. Thus, the explanation for the color difference between Dactyl and Ida is likely to be different from that which accounts for the differences between the two terrains on Ida. Given that Dactyl and Ida have very similar photometric properties (Helfenstein, P., J. Veverka, P. C. Thomas, D. P. Simonelli, K. Klassen, T. V. Johnson, F. Fanale, J. Granahan, A. S. McEwen, M. J. S. Belton, and C. R. Chapman 1996 Icarus 120, 48-65), thus ruling out any dramatic texture differences between the two surfaces, the most likely explanation is that the satellite has a slightly different composition (more pyroxene?) than Ida. The spectral difference is within the range reported by Binzel et al. (Binzel, R. P., S. Xu, and S. J. Bus 1993. Icarus 106, 608-611.) for members of the Koronis family, and could be caused by compositional inhomogeneities of the Koronis parent body rather than by post-breakup regolith processes.

Galileo imaging observations over phase angles 19.5 [degrees] to 109.8 [degrees] are combined with near-opposition Earth-based data to derive the photometric properties of Ida. To first order these properties are uniform over the surface and well modeled at [Lambda] = 0.55 [[micro]meter] by Hapke parameters [Mathematical Expression Omitted], h = 0.020, [B.sub.0] = 1.5, g = -0.33, and [Theta] = 18 [degrees] with corresponding geometric albedo [Mathematical Expression Omitted] and Bond albedo [Mathematical Expression Omitted]. Ida's photometric properties are more similar to those of 'average S-asteroids' (P. Helfenstein and J. Veverka 1989, Asteroids II, Univ. of Arizona Press, Tucson) than are those of 951 Gaspra. Two primary color units are identified on Ida: Terrain A exhibits a spectrum with relatively shallower 1-[[micro]meter] absorption and a relatively steeper red spectral slope than average Ida, while Terrain B has a deeper 1-[[micro]meter] absorption and a less steep red slope. The average photometric properties of Ida and Terrain A are similar while those of Terrain B differ mostly in having a slightly higher value of [Mathematical Expression Omitted] (0.22 versus 0.21), suggesting that Terrain B consists of slightly brighter, more transparent regolith particles. Galileo observations of Ida's satellite Dactyl over phase angles 19.5 [degrees] to 47.6 [degrees] suggest photometric characteristics similar to those of Ida, the major difference being Dactyl's slightly lower albedo (0.20 compared to 0.21).