Clinical use of heparin-coated cardiopulmonary bypass in coronary artery bypass grafting.

Clinical handling, risk and benefit of a heparin-coated cardiopulmonary bypass system combined with reduced systemic heparinization in coronary bypass surgery was investigated in a prospective, randomized clinical study. 243 patients (Pts.) were divided into 3 groups: group A (n = 83) had a standard uncoated extracorporeal circulation (ECC) set, and systemic heparin was administered in an initial dose of 400 IE/kg body weight. During ECC activated clotting time (ACT) was kept > or = 480 sec. Group B (n = 77) had the same ECC set completely coated with low-molecular-weight heparin; i.v. heparin was given in the same dose as in group A, ACT was kept at the same level. Group C (n = 83) had the same coated ECC set as group B, but i.v. heparin was reduced to 150 IE/kg, and was set to be > or = 240 sec during ECC ACT. The same circulatory components were used in all 3 groups including roller pumps, coronary suction and an open cardiotomy reservoir. In the postoperative clinical course, recovery was not significantly different between groups, especially with respect to organ dysfunction; but there was significantly reduced postoperative bleeding where heparin-coated ECC and low-dose systemic heparinization were both used. This circulatory technique was also associated with a distinctly lower need for postoperative blood replacement. We conclude that heparin-coated extracorporeal circulation combined with either full-dose or reduced systemic heparinization can be used effectively with the same standard equipment and procedures as in uncoated technology. Combination with low-dose i.v. heparin leads to significantly decreased blood loss and less need for blood replacement.     

Experimental evaluation of heparin-coated cardiopulmonary bypass equipment with low systemic heparinization and high-dose aprotinin.

Cardiopulmonary bypass (n = 8 calves) with heparin-coated perfusion equipment, low-dose systemic heparinization (activated clotting time: ACT greater than 180 s) and high-dose aprotinin administration was evaluated in comparison to standard perfusion equipment with full-dose systemic heparinization (ACT greater than 480). All animals were perfused for 6 hours and similar values were observed for blood gases and mixed venous oxygen saturation in both groups. The heparin doses given in the study group before and during the 6 hours of perfusion totalized 14660 +/- 2553 IU as compared to 60833 +/- 5137 IU for the control group. No protamin was given in the study group whereas an equivalent of 27000 +/- 5805 IU was necessary to reverse heparin in the control group. There was no difference for prebypass hematocrit versus postbypass hematocrit in the two groups. Prebypass plasma hemoglobine was 8.4 +/- 2.1 mumol/L in the study group versus 10.0 +/- 3.8 mumol/L in the control group. After mixing with the priming volume, plasma hemoglobine was 8.6 +/- 2.5 mumol/L in the study group versus 6.7 +/- 1.6 mumol/L in the control group. The highest value was observed in the study group after 2 hours of perfusion (8.2 +/- 2.1 mumol/L) versus 5 hours of perfusion in the control group (7.4 +/- 3.6 mumol/L). Prebypass LDH levels of 1610 +/- 150 IU in the study group versus 1740 +/- 210 IU in the control group moved to 1870 +/- 200 IU in the study group at 24 hours after perfusion versus 2650 +/- 400 IU in the control group at 24 hours and decreased thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)     

Systemic heparinization does not prevent clot formation in coil embolization

Therapeutic transcatheter closure with Gianturco-type steel coils has been applied to a variety of vascular communications in children with congenital heart disease. Vessel closure depends upon successful thrombus formation around the coil. Since systemic anticoagulation with heparin is commonly used during catheterization and cardiac surgery, we studied the effect of systemic heparinization on the efficiency of vessel occlusion by coil embolization in lambs. Catheters inserted in femoral arteries were used to arteriographically locate and size 36 systemic arteries in 9 lambs weighing 4.2 to 7.4 kg. Twenty-four vessels were embolized prior to heparinization with 400 u/kg heparin, IV. Effective anticoagulation was demonstrated by post-heparin activated clotting time (ACT) values greater than 300 sec. Seven vessels (29%) were not successfully coil-embolized because of inadequate coil position or distant embolization of the coil; 17 (71%) of these vessels were shown to be successfully occluded by arteriography 6 to 77 min later. After a period of systemic heparinization ranging from 71 to 159 min, 9/17 arteries remained occluded, 7/17 could not be examined arteriographically due to early demise of the animal, and only 1/17 showed recanalization. A second group of 12 vessels were embolized after heparinization. Eight (75%) were successfully occluded, and 4 (25%) were not successfully coil-embolized because of inadequate coil position or coil embolization to distant arteries. We conclude that systemic heparinization had no measurable effect on occlusion rates in coil-embolized systemic arteries in the lamb. These data support the use of systemic heparinization, when indicated, during or following therapeutic coil embolization in children.     

Hydrophilic coating aids radial sheath withdrawal and reduces patient discomfort following transradial coronary intervention: a randomized double-blind comparison of coated and uncoated sheaths.

Radial artery spasm may cause severe discomfort during radial artery sheath removal. A hydrophilic-coated sheath may reduce the force required to remove a radial sheath. This force may be quantified using an automatic pullback device (APD). The objective of this study was to assess if a hydrophilic coating reduces the required force and discomfort associated with removal of a radial sheath following transradial coronary intervention. Ninety patients undergoing percutaneous coronary intervention via the radial artery were randomly assigned to two groups receiving either coated or uncoated introducer sheaths. Radifocus Introducer II (Terumo) 25 cm, 6 Fr radial sheaths and sheaths that were identical apart from the presence of the coating were used in all patients. The APD was used for sheath removal at the end of the procedure. Three patients (7%) in the coated group experienced discomfort during automatic sheath removal, compared to 12 patients (27%) in the uncoated group (P = 0.02). The maximum pullback force (MPF) was significantly lower in the coated compared to the uncoated group (0.24 +/- 0.31 vs. 0.44 +/- 0.33 kg; P = 0.003). Similarly, the mean pullback force was significantly lower in the coated group (0.14 +/- 0.23 vs. 0.32 +/- 0.24 kg; P < 0.001). Only one patient (2%) in each group had an MPF greater than 1.0 kg together with clinical evidence of radial artery spasm. Removal of the coated Terumo Radifocus sheath requires less force than an identical uncoated sheath. The coated sheath was also associated with less discomfort for the patient.     

Substantial reduction of platelet adhesion by heparin-coated stents

Although optimized antiplatelet medication has improved the clinical outcome after coronary stenting, vessel occlusion and restenosis still remain a relevant clinical problem. Platelets play a key role in this process. Therefore, the authors compared the platelet adhesion on different stent surface modifications (electropolished without coating or coated with carbon, carbon and additional heparin, silicon carbide, or heparin alone) to investigate their role in reducing platelet adhesion. All stents and additional stainless steel plates were incubated in heparinized whole blood with radiolabeled platelets. After washing the stents and plates four times, radioactivity caused by the adhesion of radiolabeled platelets was measured. The adhesion of radiolabeled platelets, compared to uncoated, electropolished stents, was reduced through silicon carbide coating to 58.6%, by carbon coating with additional heparin to 32.9%, and heparin coating alone to 7.7%. Stent coating with heparin is the most effective among the examined coatings in reducing platelet adhesion in vitro.     

Spinal cord injury following surgery for acute traumatic rupture of the thoracic aorta

From 1970 to 1985, 49 patients were operated for traumatic aortic rupture (TAR) in 2 university hospitals. Protection of distal ischemia was performed 31 times with a left heart bypass (LHB), 5 times with a heparin coated shunt and, 13 times using simple aortic cross-clamping combined with pharmacological vasodilatation. Total mortality was 17 out of 49, 5 during and 12 after the operation, 2 of them being directly related to systemic heparinization during LHB. In the LHB and shunt groups there was one postoperative paraplegia out of 35 patients, while 4 from the 13 patients operated without a shunt developed paraplegia. If risk factors such as long cross-clamping time, hypotension, extensive laceration of the inner curvature of the aorta, or cross-clamping of the aortic arch at a high level are anticipated, LHB or the shunt technique must be considered to avoid paraplegia. A repair without a shunting procedure should be limited to those cases in which the individual surgeon believes that he can do the operation within 30 minutes aortic cross-clamping time.     

Kidney protection in preventing post-ischaemic renal failure during thoracoabdominal aortic aneurysm repair: does prostaglandin E1 together with cooling provide more protection than cooling alone?

BACKGROUND: Prostaglandin E1 (PGE1) is known to have a positive effect on kidney function after kidney ischaemia due to aortic clamping. Side effects of PGE1 are a decrease of systemic blood pressure and prevention of thrombocyte clotting, both being undesired during repair of thoracoabdominal aortic aneurysms (TAA). The aim of this study was to evaluate, whether intraoperative and intraarterial kidney perfusion with 4 degrees Ringer's lactate plus 1000 IU of heparin/l plus 20 micrograms PGE1/l is more effective in preventing postischaemic kidney dysfunction than cold perfusion without PGE1. PATIENTS AND METHODS: In the time period from I/1996 until X/1998 58 patients underwent aortic repair for TAA type II, III, or IV (Crawford's classification). Ten patients fulfilled the criteria for this study: renal artery stenosis or occlusion was excluded by angiography pre- and postoperatively. By means of szintigraphy an at least 30% participation in renal function had to be proven for every kidney. Intraoperatively both kidneys had to be excluded from circulation simultaneously. The left kidney in each patient was perfused with 4 degrees Ringer's lactate plus 1000 IU of heparin/l plus 20 micrograms PGE1/l. The right kidney was perfused with a solution of the same temperature plus heparin but without PGE1. RESULTS: There was an intermittent increase of creatinin and/or urea in each patient postoperatively. By renal szintigraphy, which was performed after a mean time of 9 (5-13) days postoperatively, a shift of renal function from one kidney to the other could be excluded. CONCLUSION: In this experimental setting no additional benefit for kidney function could be detected, when under conditions of ischaemia kidneys were perfused with 4 degrees Ringer's lactate plus 1000 IU of heparin/l plus 20 micrograms PGE1/l compared to kidneys perfused with the same solution without PGE1.     

Haemocompatibility of polymer-coated stainless steel stents as compared to uncoated stents

Acute and subacute stent thrombosis still represent an unsolved problem in connection with endovascular stents. For this reason coatings are tested now with the intention to reduce thrombogenicity of stainless steel surfaces. This comparative study examined whether a polymeric stent coating affected the haemocompatibility of a stainless steel stent. For compatibility testing, coated and non-coated stents were implanted in a low-grade thrombogenic closed-loop system perfused with platelet rich plasma at shear rates far below the threshold value at which shear-rate-induced activation of thrombocytes occurs. After 21 circulations of the filling volume (exposure time: 6.2 min), the number of single circulating platelets in the perfusion system with uncoated stainless steel stents decreased almost twice as much as was the case with polymer-coated stents. This is thought to indicate that more thrombocytes had adhered to the uncoated stainless steel stent, or that the thrombocytes were clustered in circulating aggregates. Parallel to the platelet aggregation/adherence, a release reaction took place, as was evident from the TAT complexes indicating the generation of thrombin. In the case of the implantation of uncoated stainless steel stents, both the number of activated circulating thrombocytes and the level of platelet reactivity (number of thrombocytes circulating in the plasma as aggregates) were notably higher than in the system with polymer-coated stents. At the same time it should be noted that the activation or aggregation is almost wholly attributable to the exogenic surface of the implanted stent, since activation due to the tube system or to shear rate can be excluded (as shown by measurements of the system without a stent). In addition to activation of the thrombocytes, a notable increase in the number of receptors per platelet (significant only in the system with the uncoated stent) took place. This supports both the adherence of the thrombocytes and their readiness to aggregate, since more receptors (docking places for ligands) are available. The better haemocompatibility of the polymer-coated stents, as verified in the laboratory, was also evident under microscopic examination of the explanted stents following the perfusion tests.     

非全身肝素化冠状动脉造影安全性的临床评价

目的评价非全身肝素化状态下冠状动脉造影（CAG）的安全性。方法100例择期冠状动脉脉造影的病人随机分为常规肝素抗凝组50例（肝素组）和无肝素抗凝组50例（非肝素组），非肝素组要求从鞘管进入股动脉到CAG结束在10min内完成。观察CAG期间及其后6h内病人发生卒中、新发生的外周动脉血栓、穿刺及非穿刺部位出血并发症情况。结果肝素组术中及术后无卒中、新发生的外周动脉血栓和非穿刺部位出血发生，穿刺部位血肿4例（8．0％）；非肝素组术后1例（2．0％）发生短暂性脑缺血发作，无新发生的外周动脉血栓、穿刺和非穿刺部位出血发生。结论对技术熟练的术者，在10min内，非全身肝素化状态下完成从鞘管进入股动脉到CAG操作是安全的，可减少穿刺和非穿刺部位出血并发症的发生。     

Adequate heparinization during PTCA: assessment using activated clotting times

Heparinization during PTCA is often done empirically with an initial 10,000 unit bolus of heparin and subsequent additional boluses as deemed necessary to prevent thrombus formation and fibrin deposition. However, the initial 10,000 unit bolus may not result in adequate systemic anticoagulation in every patient, exposing some patients to risk of thrombus at the angioplasty site and subsequent reocclusion. In this non-randomized study, we assessed systemic coagulation during PTCA by retrospectively analyzing activated clotting times obtained in 108 consecutive patients. All patients had normal baseline prothrombin times and activated partial thromboplastin times. Patients who were on heparin prior to PTCA were excluded. Based on data from studies on heparinization during extracorporeal bypass an activated clotting time (ACT) of greater than 300 seconds was required. Twelve patients (11%) were observed to have activated clotting times of below 300 seconds after an initial 10,000 unit bolus of heparin. These patients required an additional 3,000-10,000 units of heparin to have systemic anticoagulation during PTCA. Symptoms of stable or unstable angina had no significant effect on heparin requirement, although there was a trend toward greater heparin resistance in unstable angina. We conclude that it is important to monitor the status of anticoagulation during PTCA, for 11% of patients undergoing PTCA require additional initial heparin bolus to achieve an ACT greater than 300 seconds and to be effectively anticoagulated. Careful monitoring of heparinization during PTCA may reduce the incidence of thrombosis.     

Effects of local heparin administration on coronary thrombin activity during percutaneous transluminal coronary angioplasty.

Simultaneously obtained blood samples from the coronary sinus and systemic arterial circulation were analyzed for antithrombin III (ATIII) activity and fibrinopeptide A (FpA) concentration in nine patients undergoing elective PTCA in order to determine the effects of locally delivered heparin. Samples were obtained at the following designated times: prior to the administration of systemic heparin (period I); 5 min following a loading dose of systemic heparin (period II); 5 min following the final balloon inflation but prior to local delivery (period III); and 5 min following the administration of 4,000 units of unfractionated heparin using a local delivery catheter system (period IV). We found consistent increases in both systemic arterial (P = 0.006) and coronary sinus (P = 0.0002) ATIII activity with systemic heparinization designed to prolong the activated clotting time to 300 sec. However, local delivery of heparin further increased coronary sinus ATIII activity (P = 0.003, period III vs. period IV). FpA concentration decreased in both systemic arterial (P < 0.0001) and coronary sinus (P < 0. 0001) samples following systemic heparinization. Moreover, local delivery of heparin further decreased coronary sinus FpA concentration (P = 0.04). Thus, on a background of intense anticoagulation during PTCA, the local delivery of 4,000 units of unfractionated heparin confers incremental antithrombotic activity. Cathet. Cardiovasc. Intervent. 48:84-88, 1999.     

Non-invasive assessment of pulmonary blood supply after staged repair of pulmonary atresia

Radionuclide studies were performed to determine pulmonary blood flow in six children who had undergone surgery for pulmonary atresia, ventricular septal defect, and hypoplastic pulmonary arteries with or without major aortopulmonary collateral arteries. Lung blood flow was assessed from both particle perfusion lung scans and the pulmonary and systemic phase of a radionuclide dynamic flow study. Five patients had perfusion defects identified on the particle perfusion lung scan. In three of these, abnormal areas were perfused only during the systemic phase of the flow study, a combination of findings that indicate the presence of perfusion by collateral arteries. In one patient no systemic perfusion was noted and in one an initial particle perfusion study indicated the presence of a lung segment perfused by a collateral artery. In this last patient the particle perfusion scan after total correction showed a reduction in the size of the lung perfusion defect and no evidence of lung perfusion during the systemic phase of the flow study. The particle perfusion lung scan in the sixth patient showed pronounced asymmetry in blood flow to the lungs with no segmental perfusion defect on the particle perfusion scan and no abnormalities on the systemic flow study. It is concluded that radionuclide lung perfusion and flow studies provide useful information on lung perfusion and merit further evaluation to define their role in the management of these patients.     

Non-invasive assessment of pulmonary blood supply after staged repair of pulmonary atresia.

Radionuclide studies were performed to determine pulmonary blood flow in six children who had undergone surgery for pulmonary atresia, ventricular septal defect, and hypoplastic pulmonary arteries with or without major aortopulmonary collateral arteries. Lung blood flow was assessed from both particle perfusion lung scans and the pulmonary and systemic phase of a radionuclide dynamic flow study. Five patients had perfusion defects identified on the particle perfusion lung scan. In three of these, abnormal areas were perfused only during the systemic phase of the flow study, a combination of findings that indicate the presence of perfusion by collateral arteries. In one patient no systemic perfusion was noted and in one an initial particle perfusion study indicated the presence of a lung segment perfused by a collateral artery. In this last patient the particle perfusion scan after total correction showed a reduction in the size of the lung perfusion defect and no evidence of lung perfusion during the systemic phase of the flow study. The particle perfusion lung scan in the sixth patient showed pronounced asymmetry in blood flow to the lungs with no segmental perfusion defect on the particle perfusion scan and no abnormalities on the systemic flow study. It is concluded that radionuclide lung perfusion and flow studies provide useful information on lung perfusion and merit further evaluation to define their role in the management of these patients.     

Effect of argatroban on trinitrobenzene sulfonic acid-induced colitis

BACKGROUND: Recent studies have suggested that heparin is effective for treatment of inflammatory bowel disease (IBD) and its various effects (in addition to the anticoagulant effect). We evaluated the effects of argatroban as an antithrombin drug on trinitrobenzene sulfonic acid (TNB)-induced colitis, an established model of IBD. METHODS: Rats were randomly assigned to four groups in which mini-osmotic pumps containing saline (TNB-S), argatroban (TNB-A), or 100 U/kg heparin (TNB-H) were intraperitoneally implanted. Three days after the pumps were implanted, TNB was infused via the anus, and colitis was induced. After 5 days, prothrombin time (PT), activated partial prothrombin time (APTT), antithrombin III (AT-III), platelet, fibrinogen, colonic wet weight, macroscopic damage score, histological score, mucosal myeloperoxidase activity and mucosal leukotrien B4 (LTB4) levels were compared among the four groups. RESULTS: The APTT was prolonged in the heparin treatment group but only slightly prolonged in the argatroban treatment group. The platelet count and the fibrinogen level were higher in the TNB-S group than in the healthy control group and the AT-III level was slightly lower in the TNB-S group than in the healthy control group and lower still in the TNB-H group. CONCLUSIONS: The colonic wet weight was similar among the four groups while the macroscopic damage score, histological score, mucosal myeloperoxidase activity and the mucosal LTB4 level were significantly decreased in the TNB-A and TNB-H groups. Argatroban, as well as heparin may be effective for treatment of TNB-induced colitis.     

The effect of prophylactic heparinization on DIC arising from transitory circulatory arrest in dogs

To evaluate the beneficial effect of heparin administration on the prevention of disseminated intravascular coagulation (DIC) which appears following circulatory arrest, experimental studies were carried out with one group of dogs during circulatory arrest (control group) and compared to a group of dogs that received heparinization (heparinized group) soon after termination of circulatory arrest. Dogs of the control group were subjected to transitory circulatory arrest with occlusion balloons in the aorta and the femoral vein for a period of 8 minutes and allowed to recover without further treatment. Dogs of the heparinized group were given continuous infusions of 20 units/kg/hour of heparin as soon as circulatory arrest was started. The control group developed DIC 5 hours after circulatory arrest; however, the heparinized group demonstrated reduced platelet counts and low levels of antithrombin III (AT-III) 2 to 3 hours subsequently to circulatory arrest, but these changes were not serious, and normal levels of platelet count and AT-III were restored rapidly thereafter. Prophylactic heparin therapy is, accordingly, recommended as a useful measure of preventing the occurrence of DIC in circulatory arrest and the subsequent detrimental consequences.     

The potent platelet inhibitory effects of S-nitrosated albumin coating of artificial surfaces

OBJECTIVES: We studied the antithrombotic effect of coating glass, collagen and metal stent surfaces with bovine serum albumin (BSA) covalently modified to carry S-NO functional groups denoted (pS-NO-BSA). METHODS: Video-enhanced light microscopy was used to visualize canine blood platelet adhesion and aggregation in a parallel plate glass chamber. Platelet adhesion was observed for 60 min on glass, glass coated with BSA, glass coated with pS-NO-BSA, collagen I (CO) surface, CO coated with BSA and CO coated with pS-NO-BSA. We also coated Palmaz-Shatz (P-S) stents with pS-NO-BSA. Coated and uncoated stents were then immersed in porcine platelet-rich plasma for two min and the platelet cyclic GMP level was measured. In six anesthetized pigs, coated and uncoated stents were placed in the carotid arteries and [111In]-labeled platelets were circulated for 2 h. The stented arteries were then removed and placed in a gamma well counter. RESULTS: There was significantly less platelet attachment, adhesion and aggregation on the pS-NO-BSA coated surfaces compared with the BSA coated and uncoated surfaces. The pS-NO-BSA coating increased the platelet cGMP levels to 5.9+/-0.7 pmoles/10(8) platelets compared with 2.7+/-0.9 pmoles/10(8) platelets for control (p < 0.01). The average gamma ray count from [111In]-labeled platelets that attached to the coated stents was 90,000+/-42,000/min and 435,000+/-290,000/min for the uncoated stents (p < 0.01). CONCLUSIONS: The pS-NO-BSA coating of thrombogenic surfaces reduces platelet adhesion and aggregation, possibly by increasing the platelet cGMP. This inhibitory effect appears to be a consequence of the direct antiplatelet actions of NO combined with the antiadhesive properties of albumin.     

Thrombolytic therapy for femoral artery thrombosis after pediatric cardiac catheterization

Femoral artery thrombosis remains a well-known complication after cardiac catheterization. A study was undertaken to assess the efficacy of thrombolytic therapy for this complication. A total of 526 consecutive infants and children were prospectively evaluated after cardiac catheterization, and the medical charts of 42 patients who required femoral artery thrombectomy between 1975 and 1985 were reviewed. In the prospective study, patients were given a bolus injection of heparin, 150 U/kg, at the time the artery was entered. Patients with persistently absent or diminished pulse 2 hours after catheterization received a second bolus injection of 50 U/kg followed by an infusion of 20 U/kg/hr heparin for a maximum of 48 hours. If the affected leg pulse was absent or reduced and the systolic Doppler blood pressure was less than two thirds that of the unaffected leg, thrombolytic therapy was begun. In the 42 patients with surgical thrombectomy, there were no serious complications of surgery. Forty-five of the 526 patients (8.6%) had a decreased or absent pulse after catheterization. Of these 45 patients, 32 (71.1%) improved with systemic heparinization only. Thirteen patients (28.9%) had a persistently absent pedal pulse suggesting femoral artery thrombosis, despite continuous heparinization. Eleven patients were successfully treated with thrombolytic therapy and two required surgical thrombectomy. Intraarterial balloon dilatation procedures were performed in 8 of these 13 patients. Prothrombin time was prolonged (11.5 +/- 1.06 to 52.3 +/- 40.4 seconds; p less than 0.025) and fibrinogen levels were significantly reduced (2.25 +/- 0.79 to 1.52 +/- 0.52 gm/dl; p less than 0.01) during therapy. There were no serious complications, although four patients bled from the groin entry site.(ABSTRACT TRUNCATED AT 250 WORDS)     

Experimental Study on the Dry Drilling Nickel-Based Superalloy of CrAlYN Coated Carbide Bit

Nickel-based superalloy is regarded as one of the materials with the poorest cutting and drilling performance. Additionally, there is much less research on the drilling of it. This paper aims to study the drilling performance of dry drilling nickel-based superalloy with uncoated and CrAlYN coated carbide bit. First of all, the primary and secondary factors influencing the machining performance of dry drilling nickel-base superalloy uncoated carbide bit were explored through an orthogonal test. Secondly, the self-prepared CrAlYN coated carbide drills, and uncoated drills were compared and analyzed from perspectives of service life, drilling force, drilling temperature, drill surface topography, failure mechanism, and machining surface quality. The research results are as follows: the drilling temperature is the primary factor affecting the drilling performance under dry drilling conditions. CrAlYN coating can obviously prolong the service life of tools, reduce the drilling force and drilling temperature, and improve the machining surface quality at lower rotational speeds. Moreover, the coated cemented carbide bit has a similar failure mode to the uncoated cemented carbide bit after the CrAlYN coating falls off in the wear zone of cemented carbide bit, which is mainly bonding wear on the rear tool surface and the front tool surface.     

Explosion Test and Numerical Simulation of Coated Reinforced Concrete Slab Based on BLAST Mitigation Polyurea Coating Performance

The mechanical strength, thermal stability, thermal performance, and microstructure of Qtech T26 blast mitigation polyurea (T26 polyurea) were studied using quasi-static and dynamic mechanical experiments, thermogravimetric experiments, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) experiments, and contact explosion and non-contact explosion experiments with polyurea-coated reinforced concrete slabs. Additionally, the energy dissipation mechanism of the coating was analyzed. The blast mitigation ability and blast mitigation mechanism of T26 polyurea-coated reinforced concrete slabs were investigated by analyzing the macroscopic morphology of reinforced concrete slabs with or without coatings and the contact explosion simulation of polyurea-coated reinforced concrete slabs. The results showed that T26 polyurea exhibited a certain strain rate effect. Its initial thermal decomposition temperature reached 286 °C, and its thermal stability was good. After carbonization, carbon slag can form and adhere to the structural surface. The glass transition temperature Tgs of the soft segment was −44.9 °C, and the glass transition temperature Tgh of the hard segment was 36.5 °C, showing a certain amount of microphase separation morphology. After the explosion test, there was a small pit on the front surface of the coated reinforced concrete plate, and there was no damage on the back surface. The integrity of the plate was good. The uncoated reinforced concrete slab had a large crater on the front of the explosion surface, and the back of the explosion surface experienced explosion collapse, concrete crushing, and an overall loss of stability. The numerical simulation results showed that the failure mode of the coated plate was consistent with the test. The kinetic energy conversion rate of the uncoated reinforced concrete plate was 87.27%, and the kinetic energy conversion rate of the coated reinforced concrete plate was 95.36%. The T26 coating improved the kinetic energy conversion rate of the structure and improved the blast mitigation ability of the reinforced concrete plate structure.     

Fabrication of TiO2 – KH550 – PEG Super-Hydrophilic Coating on Glass Surface without UV/Plasma Treatment for Self-Cleaning and Anti-Fogging Applications

In this study, we have developed a self-cleaning transparent coating on a glass substrate by dip coating a TiO₂ – KH550 – PEG mixed solution with super-hydrophilicity and good antifogging properties. The fabrication of the thin-film-coated glass is a one-step solution blending method that is performed by depositing only one layer of modified TiO₂ nanoparticles at room temperature. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to determine the structure and morphology of the nanoparticles and the thin-film-coated glass. The surface functional groups were investigated using Fourier-transform infrared spectroscopy (FT-IR), and the optical properties of the glass coating were measured using a UV/Vis spectrometer. The results revealed that the KH-500-modified TiO₂ film coating was in an anatase crystalline form. The hydrophilicity of the coated and uncoated glass substrates was observed by measuring their water contact angle (WCA) using a contact angle instrument. The maximum transparency of the coated glass measured in the visible region (380–780 nm) was approximately 70%, and it possessed excellent super-hydrophilic properties (WCA ~0°) at an annealing temperature of 350 °C without further need of UV or plasma treatment. These results demonstrate the super-hydrophilic coated glass surface has potential for use in self-cleaning and anti-fogging applications.