Effect of Size-Distribution Environment on Breakage Parameters Using Closed-Cycle Grinding Tests

The so-called population balance model (PBM) is the most widely used approach to describe the grinding process. The analysis of the grinding data is carried out using-among others-the one-size fraction BII method. According to the BII method, the breakage parameters can be determined when a narrow particle size fraction is used as feed material to the mill. However, it is commonly accepted that these parameters are influenced by changing the particle size distribution in the mill. Thus, this study examines the breakage parameters through kinetic testing in different natural-size distribution environments generated by closed-cycle grinding tests that simulate industrial milling conditions. The differentiation of the milling environments was accomplished using various reference sieves in the closed-cycle tests. The experimentally determined breakage parameters were back-calculated and then used to simulate the closed-cycle tests using the MODSIMTM software. Additionally, the energy efficiency was evaluated based on the specific surface area of the grinding products and the energy consumption. The results of the kinetic tests showed that the breakage rate of the coarse particles increases as the aperture size of the reference sieve decreases, and consequently, the content of fines in the mill increases. The back-calculated breakage parameters can be reliably used to simulate closed-cycle circuits, thus helping control industrial milling operations.

A novel and greener sequential column leaching approach for the treatment of two different Greek laterites

Τhe present study investigates, from an environmental protection viewpoint, the efficiency of sequential column leaching of two different Greek laterites, i.e. a limonitic ore from central and a saprolitic ore from northern Greece. First, the most refractory limonitic laterite is leached in the first column for 15 days and the obtained pregnant leach solution (PLS) is further used for the leaching of the easier to treat saprolitic ore in the second column, thus achieving a significantly reduced acid consumption. The main parameters affecting the process efficiency, i.e. acid molarity (1.5 or 3 mol/L H2SO4) and addition of sodium sulfite (Na2SO3) in the leaching solution were studied. The extraction of Ni, Co, Fe, Al, Mg, Mn and Ca was determined by Atomic Absorption Spectroscopy (AAS), while the characterization of the ores and final residues was carried out by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA/DTA), and Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy (SEM-EDS) analysis. The results confirm the efficiency of the proposed green approach, which with the use of leaching solution containing 1.5 mol/L H2SO4 and 20 g/L Na2SO3 resulted in 73.8 % Ni, 71.6 % Co and 8.4 % Fe extraction after a short period of time (33 days), while the acid consumption, which is a serious environmental concern, was very low and did not exceed 300 kg/t ore. Overall, the proposed process not only improves the efficiency of leaching of different types of laterites for the recovery of both Ni and Co but also reduces the environmental impacts due to the significantly lower acid consumption.

Can pelvic organ prolapse in postmenopausal women be treated with laser therapy?

PURPOSE

This study aims to assess the effectiveness of the non-ablative photothermal erbium laser (Er:YAG laser) for managing anterior and/or posterior vaginal compartment prolapse.

METHODS

A randomized, single-blind, 1:1 trial was performed comparing Er:YAG laser treatment to watchful waiting in postmenopausal women with symptomatic cystocele and/or rectocele stage 2 or 3 who opted to undergo surgery due to bothersome prolapse symptoms. Three Er:YAG laser treatments at monthly intervals were applied for the Er:YAG laser group, while there was no treatment for the watchful-waiting group. The primary outcome was the proportion of patients with stage 0 or 1 following laser treatment, while secondary outcomes included the Pelvic Organ Prolapse Quantification System (POP-Q points), Pelvic Floor Distress Inventory Questionnaire short-form, Pelvic Floor Impact Questionnaire short-form, and Patients Global Impression of Improvement (PGI-I). All outcomes were evaluated at baseline and 4 months post baseline.

RESULTS

Thirty women (15 vs. 15) were eligible to be included. No participants (0%) in either group had POP-Q stage 0 or 1 at 4 months. Moreover, no change was present in the secondary outcomes. In the PGI-I, 2/15 (14%) and 0/15 (0%) participants declared much better/very much better in the laser and watchful-waiting group, respectively.

CONCLUSIONS

The findings of this study do not support use of the intravaginal Er:YAG laser for treatment of the anterior/posterior vaginal wall. Clinical trial identification number: NCT03714607.

Factors affecting co-valorization of fayalitic and ferronickel slags for the production of alkali activated materials

The first objective of this experimental study is the assessment of the alkali activation potential of two types of fayalitic slags, an as-received one (FS) and the one obtained after plasma treatment (FSP) of the initial FS, for the production of alkali activated materials (AAMs). Furthermore, the second objective is the elucidation of the co-valorization potential of FS and FSP slags when mixed with ferronickel (FeNi) slag (LS). The alkaline activating solution used was a mixture of sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃). The effect of various operating parameters, such as H₂O/Na₂O and SiO₂/Na₂O ratios present in the activating solution, curing temperature, curing period and ageing period on the compressive strength, density, water adsorption, porosity and toxicity of the produced AAMs was explored. The structural integrity of selected AAMs was investigated after firing specimens for 6 h at temperature up to 500 °C, immersion in distilled water and acidic solution or subjection to freeze-thaw cycles for a period of 7 or 30 days. The results of this study show that FS- and FSP-based AAMs acquire compressive strength of 44.8 MPa and 27.2 MPa, respectively. When FS and FSP were mixed with LS at 50:50%wt ratios the compressive strength of the produced specimens increased to 64.3 MPa and 45.8 MPa, respectively. Furthermore, selected AAMs produced after co-valorisation of slags retained sufficient compressive strength after firing at 500 °C, 45-68 MPa, and exhibited very low toxicity. These findings prove the alkali activation potential of fayalitic slags as well as their co-valorization with ferronickel slag for the production of AAMs, an approach which is in line with the principles of zero-waste and circular economy.

Large cyst of the vaginal wall in pregnancy

Large vaginal cysts during pregnancy are rare and can mislead Obstetricians to a false diagnosis, that of "Protruding membranes". Aspiration of the cyst can be easily performed, resulting in the collapsing of the cyst and an uneventful vaginal delivery can be conducted.

Column leaching of low-grade saprolitic laterites and valorization of leaching residues

Socio-economic data on nickel and cobalt show their importance throughout the entire metal value chain, from mining to end use, disposal and recycling. Thus, the extraction of both metals from primary and secondary raw materials as well as from wastes is currently considered strategically important for the industry and the society. In this paper heap leaching of Greek low-grade saprolitic laterites, with Ni content 0.97%, was investigated. The main parameters studied involved the strength of the H₂SO₄ solution used (49 and 147gL^-1) and the effect of adding sodium sulfite (Na₂SO₃) in the leaching medium. The pregnant leach solution (PLS) was recycled several times during leaching in order to minimize acid consumption. The experimental results showed that within a period of 25days, and under the optimum conditions (147gL^-1 H₂SO₄ and 20gL^-1 Na₂SO₃), i) Ni and Co extractions were 72.5% and 47.4%, respectively and ii) Fe and Al co-extractions were 8.7% and 31.3%, respectively. Furthermore, valorization of the leaching residues through alkali activation using NaOH and Na₂SiO₃ and the addition of metakaolin (MK) for the production of inorganic polymers (IPs) was explored. X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, Differential scanning calorimetry (DSC/TG) and Scanning electron microscopy (SEM-EDS) were used to characterize the ore, its leaching residues and the IPs. The IPs produced demonstrated high compressive strength, almost 40MPa and are suitable for a wide range of applications in the construction sector.

Pemphigoid gestationis

Pemphigoid gestationis is a rare autoimmune skin disorder emerging exclusively during pregnancy. Topical and oral glucocorticoids as well as oral antihistamines are the standard medications administered during pregnancy, aiming to relieve pruritus and to suppress extensive blister formation. Obstetricians should be able to recognize and treat this rare clinical condition accordingly.

Prospective study of transcutaneous oxygen tension (TcPO2) measurement in the testing period of spinal cord stimulation in diabetic patients with critical lower limb ischaemia

BACKGROUND

Spinal cord stimulation improves microcirculatory blood flow, relieves diabetic neuropathic and ischaemic pain and reduces the amputation rate in patients with severe peripheral arterial occlusive disease.

AIM

To evaluate whether transcutaneous oxygen tension (TcPO2) measurements can be used as a specific prognostic parameter in the assessment of suitability for permanent device implantation in a prospective controlled study on diabetic patients with peripheral arterial occlusive disease.

METHODS

Sixty patients (39 men, 21 women; mean age: 60 years; range: 46-75) were submitted to implantation of a spinal cord electrical generator for severe peripheral vascular disease, after failed conservative or surgical treatment. The clinical status was classified as Fontaine's stage III and IV and the main pathology was diabetic vascular disease. Pedal TcPO2 was assessed on the dorsum of the foot and ankle and toe pressure Doppler measurements were performed before, two weeks and four weeks after implantation.

RESULTS

Pain relief of over 75% and limb salvage were achieved in 35 diabetic patients, while in 12 a partial success with pain relief over 50% and limb salvage for at least 6 months was obtained. In 13 patients the method failed and the affected limbs were amputated. Clinical improvement and spinal cord stimulation success were associated with increases of TcPO2, within the first two weeks after implantation (temporary period). Limb salvage was achieved with significant increase of TcPO2 within the first two weeks of the testing period (from 21.4 to 31.5 mmHg in rest pain patients, p=0.030, from 15.1 to 22.0 mmHg, p=0.030 in patients with trophic lesions under 3 cm2 in size and in those with trophic lesions over 3 cm2, from 12.1 to 17.9 mmHg, p=0.025) unrelated to the stage of the disease and the initial TcPO2 value. TcPO2 changes were related to the presence of adequate paraesthesias and warmth in the painful area during the trial period. The systolic ankle/brachial blood pressure index and toe pressure did not change under stimulation.

CONCLUSIONS

A two-week testing period should be performed in all diabetic patients treated with spinal cord stimulation for peripheral arterial occlusive disease to identify the candidates for permanent implantation. Only diabetic patients with significant increases of TcPO2 and clinical improvement, during the test period, should be considered for permanent implantation and not merely all patients with pain relief. TcPO2 changes could be used as a predictive index of the therapy success and should be considered in terms of cost effectiveness before the final decision to permanent implantation.

Visuoperceptual speed of karate practitioners at three levels of skill

The Identical Pictures Test was administered to 50 male and 45 female volunteer karateka who were classified by Fitts' level of learning and karate belt-rank color system (kyu-dan) into three groups. A 2 (sex) x 3 (skill) analysis of variance gave a significant difference for skill and sex. Over-all, the practitioners in the autonomous stage (black belts) and the women had faster visuoperceptual speed.

Relation of physical education to self-concept

This study investigated the relation of an elementary school program in physical education to the self-concepts of children in Grades 1 to 4. Two parochial schools were selected, one with a physical education program (n = 126 children) and one without such a program (n = 86 children). The Martinek-Zaichkowsky Self-concept Scale was administered during the first two weeks of September and again during the last two weeks of April. A 2 (pre-posttest) x 2 (group) x 4 (grade) analysis of variance with repeated measures on the first factor was used to analyze each measure, with post hoc tests to follow up. The self-concept results indicated that physical education did not enhance the self-concepts of children, except for those children in the second grade.

Relationship between figure-ground perception and viewing time in a ball-catching task

This investigation determined the relationship between figure-ground perception and viewing time in a ball-catching task of 34 beginning, 34 intermediate, and 30 advanced tennis players. Also analyzed were the differences between the sexes and levels of tennis skill on figure-ground perception, on the ball-catching task, and viewing time. Findings indicated that there is no relationship between figure-ground perception and viewing time. No differences were noted between the sexes or levels of tennis skill on figure-ground perception; however, there were significant differences in success in ball-catching and viewing times.