Flocculation kinetics and mechanisms of microalgae- and clay-containing suspensions in different microalgal growth phases.

Interplays between microalgae and clay minerals enhance biologically mediated flocculation, thereby affecting the sedimentation and transportation of suspended particulate matter (SPM) in water and benthic environments. This interaction forms larger flocs with a higher settling velocity and enhances SPM sinking. The aim of this study was to investigate the flocculation kinetics of microalgae and clay in suspension and to elucidate the mechanisms associated with such interactions. Standard jar test experiments were conducted using various mixtures of kaolinite and microalgal samples from batch cultures (Chlorella vulgaris) to estimate biologically mediated flocculation kinetics. The organic matter (OM) composition secreted by the microalgae was characterized using a liquid chromatography - organic carbon detection system, and quantitative analysis of transparent exopolymer particles was conducted separately. A two-class flocculation kinetic model, based on the interaction between flocculi and flocs, was also adopted to quantitatively analyze the experimental data from flocculation. Results from the flocculation kinetic tests and OM analyses, in association with other data analyses (i.e., floc size distribution and flocculation kinetic model), showed that flocculation increased with OM concentration during the growth phase (10-20 d). However, on day 23 during the early stationary phase, flocculation kinetics started decreasing and substantially declined on day 30, even though the amount of OM (mainly biopolymers) continued to increase. Our results indicate that an adequate quantity of biopolymers produced by the microalgal cells in the growth phase enhanced floc-to-floc attachment and hence flocculation kinetics. In contrast, an excessive quantity of biopolymers and humic substances in the stationary phase enhanced the formation of polymeric backbone structures and flocculation via scavenging particles but simultaneously increased steric stabilization with the production of a large number of fragmented particles.

Comparison of the postoperative analgesic effect for infiltration between the popliteal artery and the capsule of the posterior knee and that of periarticular multimodal drug injection in total knee arthroplasty: retrospective study in the immediate postoperative period.

BACKGROUND: The aim of this study is to compare the postoperative analgesic effect of infiltration between the popliteal artery and the capsule of the knee (IPACK) and the effect of periarticular multimodal drug injection (PMDI) in addition to adductor canal block (ACB) after total knee arthroplasty. METHODS: Among patients who received total knee arthroplasty from June 2017 to December 2017, 50 who underwent ACB with additional IPACK and 50 who received ACB with additional PMDI were selected for this study. We compared the postoperative pain numerical rating scale (NRS), the number of times patient-controlled analgesia was administered and the amount administered, the total amount of opioids given, and complications associated with the procedure between the two groups. RESULTS: NRS measured at rest and 45° knee flexion at days 1 and 2 after surgery was significantly lower in the IPACK group than in the PMDI group. The resting NRS measured at day 3 after surgery was also significantly lower in the IPACK group than in the PMDI group, and the NRS at 45° knee flexion measured from day 3 to day 5 showed a significant reduction in the IPACK group. No complications relating to the procedure occurred. CONCLUSIONS: IPACK may be a better option than PMDI for controlling acute phase pain in patients undergoing total knee arthroplasty.

The effect of autotransfusion system in minimally invasive total knee arthroplasty.

PURPOSE: To evaluate the effect of autotransfusion system in minimally invasive total knee arthroplasty (TKA). MATERIALS AND METHODS: Seventy-one patients who underwent unilateral minimally invasive TKA between October 2009 and June 2010 were selected. The first group included 36 patients who received standard vacuum drainage and the second group, 35 patients who underwent autologous retransfusion drainage. In the first group, allogeneic blood transfusion was performed if the postoperative hemoglobin level was <7.0 g/dL or 7.0-8.0 g/dL with the presence of a medical complication and an anemic symptom. The second group received autotransfusion and allogeneic transfusion additionally according to the same criteria. Changes in the pre- and postoperative hemoglobin level, amount of auto- or allotransfusion, and frequency of allogeneic transfusion were assessed. RESULTS: Allogeneic transfusion was required in 13 patients (36.1%) in the first group and four patients (11.4%) in the second group. The mean allogeneic transfusion volume was significantly low in the second group compared to the first group (64.4 mL vs. 278.9 mL; p<0.05). The hemoglobin level on the 1st postoperative day compared to the preoperative level decreased by 22.6% in the first group and 11.7% in the second group. The postoperative hemoglobin level was higher in the second group (p<0.05). CONCLUSIONS: Minimally invasive unilateral TKA with an autotransfusion system can be beneficial in patients with no medical complications because of the decreased allogeneic transfusion.

Formation of quasi-single crystalline porous ZnO nanostructures with a single large cavity.

We report a method for synthesizing quasi-single crystalline porous ZnO nanostructures containing a single large cavity. The microwave-assisted route consists of a short (about 2 min) temperature ramping stage (from room temperature to 120 °C) and a stage in which the temperature is maintained at 120 °C for 2 h. The structures produced by this route were 200-480 nm in diameter. The morphological yields of this method were very high. The temperature- and time-dependent evolution of the synthesized powders and the effects of an additive, vitamin C, were studied. Spherical amorphous/polycrystalline structures (70-170 nm in diameter), which appeared transitorily, may play a key role in the formation of the single crystalline porous hollow ZnO nanostructures. Studies and characterization of the nanostructures suggested a possible mechanism for formation of the quasi-single crystalline porous ZnO nanostructures with an interior space.

Management of focal chondral lesion in the knee joint.

Articular cartilage does not contain vascular, nervous and lymphatic tissue and chondrocytes hardly participate in the healing or repair process of chondral tissue because of being surrounded by plenty of extracellular matrix. Therefore, the injury to articular cartilage frequently requires an operative treatment. The goal of surgical repair of articular cartilage is to regenerate nearly normal chondral tissue and prevent degenerative arthritis caused by the articular cartilage defect. Microfracture is a kind of cartilage repair procedure that makes a fibrin clot containing mesenchymal stem cells in the chondral lesion. Microfracture is a simple procedure but it has a disadvantage that the repaired tissue is fibrocartilage. Autologous chondrocyte implantation has an advantage that it implants fully differentiated chondrocytes to the lesion, which theoretically produces hyaline cartilage. Its disadvantages are that it is a two stage and a costly procedure. Osteochondral autograft transplantation is a one stage procedure and repairs the lesion with hyaline cartilage. But its limitation is the lack of donor site availability. Surgeons who understand the theoretical background, indications, surgical methods, rehabilitation, complications, and clinical course of cartilage repair procedures can achieve the goal of preventing degenerative arthritis.