The great complexity of the operation of wood harvesting machines and unpredictable differences of performance between operators must be reflected in the industry recruitment techniques. This work ...aimed to carry out an evaluation of the bimanual motor skill in candidates for the position of harvester operators using a virtual reality simulator to generate information that can contribute to and improve the selection process. The work was developed at the Forest Operators Training Center (CENFOR), at the State University of the Center–West, in Irati, PR. A sample of 12 individuals was studied and distributed into three levels of performance. The motor ability of the individuals was evaluated through the variables: »run time«, »fall direction«, and »cutting height«, assessed at different points during a 4-hour practice – 0.5; 1.0; 1.5; 2.0; 3.0 and 4.0 hours – practice in a virtual harvester simulator. The data were analyzed by variance and means, as well as compared to a Tukey test at the 5% level of significance. The individuals had a significant difference in the variables »run time« and »cutting height«, and could be accurately used to predict bimanual motor skill/performance. There was a significant gain in the performance of the operators up to 1.5 hours after the beginning of the skill test, and all those who demonstrated greater and lesser ability in the first half hour of the test maintained this behavior until the end of the training period. The virtual reality simulator can be used as a tool to assess bimanual motor skills during the selection of harvester operators.
To evaluate the renal function and the renal histological alterations through the stereology and morphometrics in rats submitted to the natural process of aging.
Seventy two Wistar rats, divided in ...six groups. Each group was sacrificed in a different age: 3, 6, 9, 12, 18 and 24 months. It was performed right nephrectomy, stereological and morphometric analysis of the renal tissue (renal volume and weight, density of volume (Vvglom) and numerical density (Nvglom) of the renal glomeruli and average glomerular volume (Volglom)) and also it was evaluated the renal function for the dosage of serum creatinine and urea.
There was significant decrease of the renal function in the oldest rats. The renal volume presented gradual increase during the development of the rats with the biggest values registered in the group of animals at 12 months of age and significant progressive decrease in older animals. Vvglom presented statistically significant gradual reduction between the groups and the Nvglom also decreased significantly.
The renal function proved to be inferior in senile rats when compared to the young rats. The morphometric and stereological analysis evidenced renal atrophy, gradual reduction of the volume density and numerical density of the renal glomeruli associated to the aging process.
To evaluate, by quantitative and qualitative methods, the glomerular ultrastructure in Wistar rats fed a cafeteria diet.
Male Wistar rats were divided into two groups at 21 days of age: control (C, n ...= 10) and cafeteria diet (CAF, n = 8). The animals were followed up until 5 months of age, followed by euthanasia. The blood, kidneys, and fat deposits--epididymal, retroperitoneal, and subcutaneous--were extracted and analyzed. Data were analyzed by Student's t test, and p < 0.05 was considered statistically significant.
The cafeteria diet promoted glucose intolerance, hyperglycemia (p < 0.0001), and deposition of retroperitoneal fat (p < 0.005). Scanning electron microscopy revealed that the length of the foot process was similar in both groups. The quantitative analyses by transmission electron microscopy revealed that the cafeteria diet reduced the thickness of the glomerular basement membrane (p < 0.05).
The intake of lipids and simple carbohydrates were found to be associated with alteration in the glomerular ultrastructure. However, more studies are needed to evaluate not only the effects of high-protein and high-fat diets on components of the glomerular filtration barrier, but also renal physiology.
A sustainable alternative for wood waste is turning them into structural panels since it adds value to the raw material and contributes to the sector's circular economy. Strand-based composites such ...as oriented strand board is a natural fit for these wood wastes. A molded core composite with sandwich geometry with trapezoidal core guarantees significant increases in the stiffness of the panel, enabling its use as structural components in civil construction. Therefore, in this study, the mechanical properties of OSB sandwich panel with trapezoidal core produced with Balsa wood (
Ochroma Pyramidale
) waste agglomerated with bicomponent castor oil polyurethane resin (phenol free) were evaluated. The results indicate that the panel under study presented properties in the longitudinal direction that enable its use as a structural component.
Graphical Abstract
In mechanized timber harvesting operations, it is possible to verify ergonomic inadequacies, such as poor visibility and inappropriate postures, which can cause risks to the safety and health of ...workers, with effects on the operational performance of the machines. In this context, the objective of this work was to evaluate the effects of the positioning of the coupling crane in harvesters concerning the visibility and postures of forestry operators. For this, the study was carried out in clear-cutting operations in eucalyptus stands, evaluating a harvester with a frontal coupling crane and another with lateral coupling, as well as operators per machine. To determine effective times and typical postures, filming and freezing of images were performed. Then, the Skogforsk and Rapid Upper-Limb Assessment (RULA) methods were used to assess visibility and posture, respectively. Angulation and posture data were compared between machines by the Student's t test. Front and side visibility remained within acceptable limits, but the side crane harvester required operators to have an average head tilt angle of 15º, 50% higher than with the front crane. Consequently, in the postural evaluation, the one with the lateral crane presented score 3 and action level 2 86% of the time, suggesting further investigations, while the other presented score 2 and action level 1 81% of the time, being acceptable if not maintained or repeated for long periods. Therefore, the positioning of the crane coupling on the machine requires a reorganization of the workstation, mainly the machine's display.
The levels of exposure whole-body vibration (WBV) while performing mechanized soil preparation operations are concerning due to the exposure time of operators at their work stations, adverse terrain ...topography, and types of wheels on the machines used. Thus, this study aimed to evaluate the exposure to WBV in bulldozers and hydraulic excavators in performing soil preparation for forest plantation in order to identify possible ergonomic problems and propose improvements in working conditions. The study was carried out in Paraná State, Brazil, in a Eucalyptus urophylla × Eucalyptus grandis stand hybrid, being registered with use of a vibration meter and triaxial accelerometer coupled to the seat of the machines, the resulting acceleration to normalized exposure (aren) and the resulting vibration dose (VDVR) for a period of 8 working hours, following the Occupational Hygiene Standard 09. The results showed aren and VDVR values of 1.0 m s-2 and 18.3 m s-1.75 in the bulldozer, while in the hydraulic excavator it was 0.7 m s-2 and 13.5 m s-1.75, respectively, with a statistically significant difference between the machines by the Wilcoxon test for independent samples (α ≤ 0.05). The WBV levels were above the action level and below the exposure limit in both machines, with the bulldozer showing values above the uncertainty level. Therefore, substituting machines specifically designed for soil preparation and improvements in work organization are measures indicated to reduce ergonomic problems.
The increased demand for several forest products makes it necessary to apply different management regimes in forest stands, which may influence the wood harvesting operations. This study aimed to ...evaluate the effect of average individual tree volumes obtained through different management regimes on harvester productivity and costs, thereby enabling to generate information for forest managers. The study was carried out in three Pinus taeda L. stands under clear cutting with different average individual tree volumes (AIV): I (0.367 m3); II (0.582 m3); and III (0.766 m3). Working cycle times, productivity per productive machine hour, energy yield and production costs were obtained by a time and motion study, in which the average values obtained were compared by the Tukey-Kramer test (α ≤ 0.05). The work elements of the harvester’s work cycles were affected by forest management regimes, mainly the movement and the processing, with significant statistical difference between stands, but no difference between total working cycle times. The management regime applied to forest stands influenced the spacing and whole trunk volume which consequently increased the average productivity of the machine from 36.8 to 74.1 m³ per productive machine hour in treatments I and III, respectively, and reduced production costs by 50%. The forest management regimes influenced the clear-cutting operation with harvester.
•Development of an unconventional material using forest biomass by-products.•OSB sandwich panel has great potential for applications in civil construction.•Finite element model adequately predicted ...the deflection and failure of the panel.•The stiffness ratio of the longitudinal and transverse directions was around 1.6.
The development of materials using forest biomass by-products has presented a viable alternative to replacing conventional materials and a great potential for the reuse of waste by-products. This study aimed to evaluate experimentally and by computational modeling, the mechanical performance of OSB (Oriented Strand Board) panels stiffened by the trapezoidal core according to the bending direction. By the cross-section of the panels manufactured with strands of balsa wood waste and castor oil polyurethane resin, the influence of the core direction on the flexural stiffness and ultimate load capacity was evaluated. Bending performance tests showed that stiffness in the longitudinal direction was 56% greater than in the transversal direction. For this same approach and referring to the elastic-linear segment, the computational modeling by Finite Element Analysis showed a superiority of 66% for stiffness in the longitudinal direction. Regarding the deflections and predictions of critical regions for the failure of the panel, an appropriate accuracy of the computational models adjusted for the material's nonlinearity and orthotropy. The OSB sandwich panels reached the minimum normative requirements for structural purposes, presenting great potential for applications in civil constructions, due to their efficient bending stiffness added to the benefits of a bio-based waste product
In this work, we present that how bifurcation in Pinus trees can influence productivity and harvester production costs. Our example draws from one harvesting machine that works in thinning operations ...in forest plantations of Pinus taeda L. in a small Brazilian forestry company. To get daily productivity, we use the machine's system, which provides such daily information as total production. We also used a time and motion study to obtain the meantime to cut, delimb, and process the tree stem into logs. In this way, we separated the normal trees from the forked trees to get the operating cycle time of the machine and get the productivity to the two types of trees. The continuous timing method was used for this purpose. The results show an increase of up to 22.9% in the operational cycle time for cutting forked trees, resulting in reduction of productivity of 5.58 m3 for each hour worked. The production cost increased by 23.3% on operation of forked trees, as the machine took more time to perform the partial activities of the operational cycle. This study can help many companies and contractors to calculate the appropriate productivity and production harvest cost according to the type of tree stems from the plantation forest.
Receptors of living donor liver transplantation (LDLT) have higher rate of postoperative biliary and vascular complications that may reduce posttransplant quality of life (QOL) due to the need of ...invasive and repetitive treatments.
The purpose of our study is to assess the various aspects of QOL of receptors undergoing LDLT after 10 years of transplantation and to identify potential factors that might be associated with impaired QOL.
Data of all patients with more than 10 years of LDLT were retrospectively evaluated. Patients were interviewed through a quality of life questionnaire (SF-36).
From a total of 440 LT performed in 17 years (from September 1991 through December 2008), 78 patients underwent LDLT, of which 27 were alive and 25 answered completely the questionnaire. There were 17 (68%) men and 8 (32%) women, with a mean age of 38.6±18.5 years at the time of transplantation and mean follow up time of 15.1±1.9 years. The average MELD was 16.4±4.9 and the main indication for LT was hepatic cirrhosis caused by hepatitis B virus (32%). When compared to the general po-pulation, LDLT patients had lower mental health score (66.4 vs 74.5, P=0.0093) and higher vitality score (87.8 vs 71.9, P<0.001), functional aspects (94.6 vs 75.5, P=0.002), social aspects (93 vs 83.9, P=0.005), physical aspects (92 vs 77.5, P=0.006), and emotional aspects (97.33 vs 81.7, P<0.001). General health status (73.28 vs 70.2, P=0.074) and pain (78.72 vs 76.7, P=0.672) scores were similar in both groups.
It is concluded that the various aspects LDLT recipients' QOF are similar to those of the general population more than a decade after the transplant, except for the mental health domain which is lower.
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