scholarly journals Effects of crevice size on the establishment of macroalgae in subtropical streams

2014 ◽  
Vol 74 (4) ◽  
pp. 803-809
Author(s):  
AF Tonetto ◽  
CK Peres ◽  
MA Khnayfes ◽  
CCZ Branco
Keyword(s):  
Surface Roughness ◽  
Plane Surface ◽  
Algal Growth ◽  
Percent Cover ◽  
Weak Effect ◽  
Southern Brazil ◽  
Full Sunlight ◽  
Macroalgal Community ◽  
Stream Macroalgae ◽  
Different Shapes

Considering that in previous studies, the surface roughness (micrometric dimension) showed a weak effect on the colonization of stream macroalgae, we investigated the effects of different crevice sizes (milimetric dimension, a scale slightly higher than previous investigations) on the macroalgal abundance in three streams exposed to full sunlight in southern Brazil. We used smooth sterile glass plates with different shapes: P – plane surface without crevices; S – sinuous surface (depth of crevices with 0.159 mm ± 0.03); N – non-unifom surface (0.498 mm ± 0.09); C – surfaces with convex structures (1.190 mm ± 0.12); and three additional surface types with different patterns of heterogeneity with combinations of glass pieces: P + S (H1); P + S + N (H2) and P + S + N + C (H3). The plates were placed into the streams and after 105 days the percent cover of macroalgal community was measured. No significant differences among treatments were recorded. However, we observed a trend of macroalgae occurs within the crevices in all treatments and this suggests that, for stream macroalgae, the crevice sizes used in this study was still not enough to provide an expressive algal growth, even in the treatment with bigger crevices.

scholarly journals Epilithic community development on artificial reefs deployed along a cross-shelf environmental gradient off Paraná state, southern Brazil

2011 ◽  
Vol 59 (spe1) ◽  
pp. 43-53 ◽  
Author(s):  
Frederico Brandini ◽  
Ariel Scheffer da Silva
Keyword(s):  
Large Scale ◽  
Diversity Index ◽  
Artificial Reef ◽  
Larval Abundance ◽  
Percent Cover ◽  
Southern Brazil ◽  
Factors Affecting ◽  
Hydrographic Conditions ◽  
One Year ◽  
General Community

Concrete modules were deployed on the bottom of the 11, 18 and 30 meters isobaths along a cross-shelf hydrographic gradient off Paraná State, Southern Brazil, with the purpose of studying the colonization of sessile epilithic macroinvertebrates on artificial surfaces. After one year of submersion a total of 63 species of epilithic organisms were identified, dominated by Ostrea puelchana, Chthamalus bisinuatus, Balanus cf spongicola, Astrangia cf rathbuni, Didemnum spp, poryphers and bryozoans. Diversity index and percent cover at reef stations placed at 11, 18 and 30 meters isobaths were respectively 2.28 and 66.7%, 2.79 and 96.6% and 1.66 and 77.4%. Differences of general community structure among the three assemblages were not clearly related to the general environmental conditions at the bottom layers near the reef stations. Turbidity and larval abundance are discussed as important factors affecting colonization processes. Results indicate that depths between 15-20 meters are more suitable for the implementation of large scale artificial reef systems in the inner shelf off Paraná and, possibly, throughout the inner shelves off southern Brazil with similar hydrographic conditions.

Effect of various factors influencing the generation of hemispherical micro features using non-conformal RMEDM

2019 ◽  
Vol 2 (2) ◽  
pp. 110-122 ◽  
Author(s):  
T. Roy ◽  
R. Balasubramaniam
Keyword(s):  
Surface Roughness ◽  
Electrical Discharge Machining ◽  
Flat Bottom ◽  
Machining Time ◽  
Micro Electrical Discharge Machining ◽  
Bottom Hole ◽  
Roughness Analysis ◽  
Feature Based ◽  
Different Shapes ◽  
Micro Features

Non-conformal reverse micro electrical discharge machining (NC-RMEDM) is a variant of conventional RMEDM developed by the present authors wherein modification in the tool is carried out to generate different shapes of micro features. In this study, the effect of various factors like flat bottom and taper bottom hole, inversing the position of tool and workpiece and changing the hole depth have been experimentally investigated to determine the optimal combination required for generating hemispherical shaped micro features. It was found that hemispherical shaped micro feature can be generated by employing tapered bottom blind hole as tool. Buoyancy assisted machining (BAM) with traverse of workpiece (anode) downwards into the tool (cathode) and vice versa, i.e., buoyancy opposed machining (BOM) with traverse of tool downwards into the workpiece were carried out to study the generation of hemispherical micro feature based on inversion of electrode positions. Although both BAM and BOM generated hemispherical shaped feature, BAM is preferred due to reduced machining time as opposed to BOM. Also, increasing the hole depths led to altering the shape of micro feature from hemispherical to cylindrical with hemispherical end and coni-spherical end. An array of hemispherical micro features was fabricated based on the finding from this study, and surface roughness analysis was carried out which showed that irrespective of the position of micro feature on the array, surface roughness at the tip and base of the micro feature is lower as compared to side portion.

Effects of overtopping vegetation on light availability and growth of Engelmann spruce (Piceaengelmannii) seedlings

1993 ◽  
Vol 23 (10) ◽  
pp. 2044-2048 ◽  
Author(s):  
Philip G. Comeau ◽  
Thomas F. Braumandl ◽  
Chang-Yi Xie
Keyword(s):  
Seedling Growth ◽  
Objective Assessment ◽  
Light Availability ◽  
Field Measurements ◽  
Percent Cover ◽  
Competition Index ◽  
Full Sunlight ◽  
Vegetation Height ◽  
Engelmann Spruce ◽  
Neighborhood Studies

To examine the effects of overtopping vegetation on solar irradiance reaching Engelmann spruce (Piceaengelmannii Parry) seedlings and on crop seedling performance, neighborhood studies were established at six sites in mixed shrub–herb and fireweed communities of the Interior Cedar–Hemlock zone of southern British Columbia. These communities were dominated by mixtures of fireweed (Epilobiumangustifolium L.), thimbleberry (Rubusparviflorus Nutt.), red raspberry (Rubusidaeus L.), and (or) bracken fern (Pteridiumaquilinum (L.) Kuhn). Three hundred and eighty-eight planted Engelmann spruce seedlings, between 1 and 5 years of age, served as plot centers for measurements in 1990 and 1991. Vegetation had been clipped around 109 of these seedlings in 1988, 1989, and 1990. Seedling diameter and height were measured in the autumn of 1990 and 1991. Vegetation cover, vegetation height, and the fraction of full sunlight reaching the top branches of each spruce seedling were measured in midsummer of 1991. A simple competition index (CI), based on visually estimated percent cover, height of each species present within 1.26 m of the crop seedling, and crop-seedling height, can be used to estimate the fraction of full sunlight reaching crop seedlings. Measurements of transmittance through vegetation canopies are correlated with this competition index and could be useful as a separate, objective assessment of competition levels. Seedling growth was related to both seedling-needle biomass (at the beginning of the year) and either CI or the amount of light reaching crop seedlings during midsummer. Growth increased as needle biomass or irradiance reaching the seedling increased and decreased as CI increased. Since CI can be calculated from simple field measurements and since seedling growth is related to CI, this index has potential utility in evaluating the need for operational release treatments. Transmittance measurement provides an equally useful, and potentially more objective approach to evaluating the need for release treatment. Results from this study suggest that cumulative effects of competition result at least in part from effects on growth of seedling leaf mass.

Height growth of planted black spruce seedlings in response to interspecific vegetation competition: a comparison of four competition measures at two measuring positions

2000 ◽  
Vol 30 (4) ◽  
pp. 573-579 ◽  
Author(s):  
G G Wang ◽  
J Su ◽  
J R Wang
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Picea Mariana ◽  
Black Spruce ◽  
Height Growth ◽  
Percent Cover ◽  
Relative Height ◽  
Full Sunlight ◽  
Significant Relationships ◽  
Hemispherical Photographs

Four simple measures of interspecific competition (percent cover visually estimated in the field, percent cover derived from hemispherical photographs, percent full sunlight measured by a ceptometer, and gap light index derived from hemispherical photographs) obtained at two reference positions (the top and the middle of crop seedlings) were evaluated in relation to two growth variables (relative height growth rates in 1998 and during 1996 to 1998) of black spruce (Picea mariana (Mill.) BSP) seedlings planted on boreal mixedwood sites in southeastern Manitoba. The four competition measures assessed at the two measuring positions explained 57.2-68.0% of the total variation in black spruce height growth rate. Significant relationships were found among the four measures, and between the two measuring positions for each measure. The measuring position was not critical for all competition measures except the percent full sunlight measured by the ceptometer, for which the middle position was much better. When assessed at their preferred positions, the four competition measures ranked as follows: (i) percent cover derived from hemispherical photographs or percent full sunlight measured by the ceptometer; (ii) gap light index derived from hemispherical photographs; and (iii) visually estimated percent cover of vegetation.

Magnetic domain wall trapping by in-plane surface roughness modulation

2003 ◽  
Vol 82 (8) ◽  
pp. 1239-1241 ◽  
Author(s):  
J. Swerts ◽  
K. Temst ◽  
M. J. Van Bael ◽  
C. Van Haesendonck ◽  
Y. Bruynseraede
Keyword(s):  
Surface Roughness ◽  
Domain Wall ◽  
Plane Surface ◽  
Magnetic Domain ◽  
Magnetic Domain Wall

Effect of surface roughness on magneto-hydrodynamic squeeze-film characteristics between a sphere and a porous plane surface

2014 ◽  
Vol 66 (3) ◽  
pp. 365-372 ◽  
Author(s):  
Neminath Bhujappa Naduvinamani ◽  
Mareppa Rajashekar
Keyword(s):  
Surface Roughness ◽  
Response Time ◽  
Carrying Capacity ◽  
Hydrodynamic Lubrication ◽  
Plane Surface ◽  
Squeeze Film ◽  
Load Carrying Capacity ◽  
Content Type ◽  
Load Carrying ◽  
Film Characteristics

Purpose – The purpose of this article is to analyse the effects of surface roughness on the magneto-hydrodynamic (MHD) squeeze-film characteristics between a sphere and a porous plane surface, which have not been studied so far. Design/methodology/approach – The analytical model takes into account the effect of porosity by assuming that the flow in the porous matrix obeys modified Darcy's law. The stochastic MHD Reynold's type equation is derived by using the Christensen's stochastic method developed for hydrodynamic lubrication of rough surfaces. Two types of one-dimensional surface roughness (radial and azimuthal) patterns are considered. Findings – The expressions for the mean MHD squeeze-film pressure and mean load-carrying capacity are obtained numerically. The results are shown graphically for selected representative parametric values. It is found that the response time increases significantly for the MHD case as compared to the corresponding non-conducting lubricants. The effect of roughness parameter is to increase/decrease the load-carrying capacity and the response time for azimuthal/radial roughness patterns as compared to the smooth case. Also, the effect of porous parameter is to decrease the load-carrying capacity and response time as compared to the solid case. Originality/value – In this paper, an attempt has been made to analyse the combined effects of surface roughness and permeability on the MHD squeeze-film characteristics between a sphere and a plane surface.

Comparison of Theoretical and Real Surface Roughness in Case of Ball-End Milling

2017 ◽  
Vol 261 ◽  
pp. 299-304 ◽  
Author(s):  
Balázs Mikó ◽  
Balázs Tóth ◽  
Bálint Varga
Keyword(s):  
Surface Roughness ◽  
End Milling ◽  
Plane Surface ◽  
Estimation Method ◽  
Free Form ◽  
Surface Finishing ◽  
Depth Of Cut ◽  
Real Surface ◽  
Ball End Milling ◽  
Tool Diameter

In case of free form surface milling the quality of the manufacturing is described by the accuracy of the shape and the surface roughness. The 3D surface finishing milling by ball-end milling cutter is one of the most often used machining technologies. In case of ball-end milling the surface roughness can be described theoretically based on the tool diameter and the density of the tool path, but the experience shows than other parameters have effect on the surface roughness. In the article the effect of the different cutting parameters, like feed (fz), depth of cut (ap) and width of cut (ae), is presented in case of plane surface, and the surface roughness is compared with the theoretical roughness, and an estimation method is presented.

scholarly journals Effect of Surface Roughness on MHD Couple Stress Squeeze-Film Characteristics between a Sphere and a Porous Plane Surface

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
M. Rajashekar ◽  
Biradar Kashinath
Keyword(s):  
Surface Roughness ◽  
Carrying Capacity ◽  
Couple Stress ◽  
Hydrodynamic Lubrication ◽  
Plane Surface ◽  
Squeeze Film ◽  
Load Carrying Capacity ◽  
Film Pressure ◽  
Load Carrying ◽  
The Mean

The combined effects of couple stress and surface roughness on the MHD squeeze-film lubrication between a sphere and a porous plane surface are analyzed, based upon the thin-film magnetohydrodynamic (MHD) theory. Using Stoke’s theory to account for the couple stresses due to the microstructure additives and the Christensen’s stochastic method developed for hydrodynamic lubrication of rough surfaces derives the stochastic MHD Reynolds-type equation. The expressions for the mean MHD squeeze-film pressure, mean load-carrying capacity, and mean squeeze-film time are obtained. The results indicate that the couple stress fluid in the film region enhances the mean MHD squeeze-film pressure, load-carrying capacity, and squeeze-film time. The effect of roughness parameter is to increase (decrease) the load-carrying capacity and lengthen the response time for azimuthal (radial) roughness patterns as compared to the smooth case. Also, the effect of porous parameter is to decrease the load-carrying capacity and increase the squeeze-film time as compared to the solid case.

scholarly journals The interactive effect of herbivory, nutrient enrichment and mucilage on shallow rocky macroalgal communities

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e6908
Author(s):  
Sarah Caronni ◽  
Chiara Calabretti ◽  
Sandra Citterio ◽  
Maria Anna Delaria ◽  
Rodolfo Gentili ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Nutrient Enrichment ◽  
Marine Protected Area ◽  
Interactive Effect ◽  
Grazing Pressure ◽  
Coralline Algae ◽  
Percent Cover ◽  
Crustose Coralline Algae ◽  
Macroalgal Community ◽  
Experimental Treatments

This paper focuses on the interactive short and long-term effect of three different stressors on a macroalgal assemblage. Three stressors are considered: herbivory, nutrients and mucilage. The experiment was conducted in Tavolara Punta Coda Cavallo Marine Protected Area (Mediterranean Sea) during a bloom of the benthic mucilage-producing microalga Chrysophaeum taylorii (Pelagophyceae); this microalga is recently spreading in the Mediterranean Sea. On a rocky substratum, 36 plots 20 × 20 cm in size were prepared. Factorial combinations of three experimental treatments were applied in triplicate, including three grazing levels crossed with two nutrient enrichment and two mucilage removal treatments. Significant differences were observed among treatments 8 weeks later, at the end of summer. In particular, dark filamentous algae were more abundant in all enriched plots, especially where mucilage and macroalgae had been removed; a higher percent cover of crustose coralline algae was instead observed where nutrients had been increased and no grazing pressure acted. Furthermore, the abundance of Dictyota spp. and Laurencia spp. was significantly higher in enriched mucilage-free plots where the grazing pressure was null or low. However, the effects of the treatments on the overall assemblage of the macroalgal community were not long persistent (36 weeks later). These results illustrate the capacity of a shallow-water macroalgal community to quickly recover from the simultaneous impacts of herbivory, nutrient enrichment, and mucilage.

Sign in / Sign up

Export Citation Format

Share Document