Modeling the Impact of Testing Mode on the Viscoelastic Behavior of Asphalt Concrete

The variations in the viscoelastic characteristics of asphalt concrete due to testing mode are assessed and modeled in the present investigation.Asphalt concrete mixture was prepared at its optimum asphalt binder requirement and compacted in slab mold with the aid of roller compaction.Beam specimens of 6.2 cm width,5.6 cm depth,and 40 cm length,were obtained from the slab samples with the aid of a diamond saw,and tested using controlled stress and strain techniques under dynamic flexural stresses.The viscoelastic properties such as the phase angle,cumulative dissipated energy,permanent deformation,flexural stiffness,and micro strain were monitored and modeled among the two testing techniques.It was noticed that higher micro strain and permanent deformation are detected when testing the asphalt concrete specimens under constant strain mode.However,higher phase angle,flexural stiffness,and energy dissipation could be observed under the constant stress mode of the test.

Comparing surgical efficiencies between phacoemulsification systems: a single surgeon retrospective study of 2000 eyes

AIM: To compare under similar conditions intraoperative surgical efficiencies metrics between an active fluidics and a gravity based phacoemulsification systems.METHODS: Adult patients who were diagnosed with a cataract that compromised visual acuity inferior to 20/40 were included in the study. Patients were excluded from the study if they had a history of severe retinal disorders, clinically significant corneal endothelial dystrophy or history of corneal disease. All phacoemulsification surgeries were performed by a single surgeon. Both phacoemulsification systems used the 0.9 mm 45-degree aspiration bypass system Intrepid Balanced tip and the 0.9 mm Intrepid Ultra infusion sleeve. All cataracts were classified using the Lens Opacities Classification System III, cumulative dissipated energy(CDE) and aspiration fluids were measured in each surgery.RESULTS: Totally 2000 eyes were included in the study. Phacoemulsification was performed in 1000(50%) eyes with an active fluid dynamics system and in 1000(50%) eyes with a gravity-based fluidic system. Mean CDE until fracture of the lens was 1.1 and 1.9 percent-seconds and total mean CDE used was 5.6 and 7.2 percent-seconds using an active fluidics dynamics system and gravity-based fluidic system, respectively(P<0.001). Mean aspiration fluids used were 70 m L using an active fluidics dynamics system and 85 m L using a gravity-based fluidic system(P<0.001).CONCLUSION: This study evidences that surgeries performed under similar conditions(same surgeon, phaco tip and sleeve) with the active fluidics dynamics system required significantly lower CDE and aspiration fluids.

Evaluation of environmental factors to fatigue performance of asphalt mixes

This paper studies the effect of different environmental factors, including the axle load weight, environmental temperature, vehicle speed, and the aging level of asphalt, on the fatigue performance of asphalt mixes based on four-point bending beam fatigue tests. A fractional factorial design method named ＂uniform design＂ was applied in experimental design. The relations of the environmental factors to initial stiffness, fatigue life, phase angle and cumulative dissipated energy were established with the general linear modeling method. It is found that there exists very good correlativity between the environmental factors and the fatigue performance indices of asphalt mixes. The coefficients of total correlation are mainly beyond 0. 95. The results indicate that the consideration of the effect of environmental factors is necessary in the fatigue performance evaluation on real asphalt pavement.

Prospective study of Centurion~？ versus Infiniti~？ phacoemulsification systems： surgical and visual outcomes

AIM： To evaluate surgical outcomes（SOs） and visual outcomes（VOs） in cataract surgery comparing the Centurion？ phacoemulsification system（CPS） with the Infiniti？ phacoemulsification system（IPS）.METHODS： Prospective, consecutive study in a singlesite private practice. Totally 412 patients undergoing cataract surgery with either the CPS using the 30-degree balanced？ tip（n=207） or the IPS using the 30-degree Kelman？ tip（n=205）. Intraoperative and postoperative outcomes were documented prospectively up to one month follow-up. Nuclear sclerosis（NS） grade, cumulated dissipated energy（CDE）, preoperative corrected distance visual acuity（CDVA）, and CDVA at one month were recorded. RESULTS： CDE was 13.50% less in the whole CPS compared with the whole IPS subcohort. In eyes with NS grade III or greater, CDE was 28.87% less with CPS（n=70） compared with IPS（n=44）（P=0.010）. Surgical complications were not statistically different between the two subcohorts（P=0.083）, but in the one case of vitreous loss using the CPS, CDVA of 6/4 was achieved at one month. The mean CDVAs（VOs） at one month for NS grade III and above cataracts were-0.17 log MAR（6/4.5） in the CPS and-0.15 log MAR（6/4.5） in the IPS subcohort respectively（P=0.033）.CONCLUSION： CDE is 28.87% less, and VOs are significantly improved, in denser cataracts in the CPS compared with the IPS. The authors recommend the CPS for cases with denser nuclei.

Effect of IOP based infusion system with and without balanced phaco tip on cumulative dissipated energy and estimated fluid usage in comparison to gravity fed infusion in torsional phacoemulsification

Background:To evaluate the effect of three different combinations of tip designs and infusion systems in torsional phacoemulsification(INFINITI and CENTURION)in patients with cataract.According to the manufacturer,two unique improvements in the Centurion are:active fluid dynamic management system and use of an intrepid balanced tip.The study specifically aimed to evaluate the beneficial effects,if any,of change in tip design and infusion system individually and in combination on both per-operative parameters as well as endothelial health over 6 months.Methods:One hundred and twenty six consenting patients of grade 4.0-6.9 senile cataract were randomized into three groups for phacoemulsification:Group A(n=42):Gravity fed infusion system and 45° Kelman miniflared ABS phaco tip;Group B(n=42):intraocular pressure(IOP)based infusion system and 45° Kelman miniflared ABS phaco tip;Group C(n=42):IOP based infusion system and 45° Intrepid balanced phaco tip.The cumulative dissipated energy(CDE),estimated fluid usage(EFU)and total aspiration time(TAT)were compared peroperatively.The endothelial parameters were followed up postoperatively for six months.Results:The three arms were matched for age(p=0.525),gender(p=0.96)and grade of cataract(p=0.177).Group C was associated with significant reductions in CDE(p=0.001),EFU(p<0.0005)as well as TAT(p=0.001)in comparison to the other groups.All three groups had comparable baseline endothelial cell density(p=0.876)and central corneal thickness(p=0.561).On post-operative evaluation,although all groups were comparable till 3 months,by 6 months,the percentage losses in endothelial cell density were significantly lower in group C as compared to the other groups.Conclusions:Use of an IOP based phacoemulsification system in association with use of the Intrepid balanced tip reduces the CDE,EFU and TAT in comparison to a gravity fed system with a mini flared tip or IOP based system with a mini flared tip while also providing better endothelial preservation thus favouring the use of an IOP fed system with a balanced tip.

Comparison of clinical outcomes between femtosecond laser-assisted versus conventional phacoemulsification

Background:To compare femtosecond laser-assisted versus conventional phacoemulsification in terms of visual and refractive outcomes,cumulative dissipated energy,anterior chamber inflammation and endothelial cell loss.Methods:In this retrospective cohort study,records of eyes that underwent femtosecond laser-assisted cataract surgery(FLACS)or conventional phacoemulsification(CP)were reviewed.The Victus femtosecond laser(Bausch and Lomb,Germany)was used to carry out corneal incisions,anterior capsulotomy,and lens fragmentation in FLACS procedures.Manifest refraction spherical equivalence(MRSE),uncorrected distance visual acuity(UDVA),corrected distance visual acuity(CDVA),cumulative dissipated energy(CDE),postoperative cells and flare and endothelial cell count data were collected.Subgroup analysis of the visual acuity tests was performed based on the type of intraocular lens implanted(monofocal,monofocal toric,multifocal,multifocal toric,accommodating).Results:A total of 735 eyes were included in the study(296 eyes for the FLACS group and 439 eyes for the CP group).At one year follow-up,120 eyes comprised the FLACS group and 265 eyes for the CP group.MRSE in the FLACS group was−0.16±0.58 D and−0.20±0.52 D in the CP group(P=0.50).UDVA in the FLACS group was 20/25(mean logMAR 0.12±0.13)and 20/25(mean logMAR 0.11±0.13)in the CP group(P=0.48).CDVA was 20/20(mean logMAR 0.03±0.07)in the FLACS group and 20/20(mean logMAR 0.02±0.06)in the CP group(P=0.15).No statistically significant trend was seen for FLACS versus CP by intraocular type for visual acuity.CDE for the different cataract grades ranged from 6.97±5.74 to 29.02±16.07 in the FLACS group and 7.59±6.42 to 35.69±18.30 in the CP group.The FLACS group was significantly lower for post-operative central corneal edema(P=0.05),cells and flare(P=0.01),and endothelial cell loss(P=0.04).Conclusions:Femtosecond laser-assisted cataract surgery and conventional phacoemulsification had similar refractive and visual outcomes.Phacoemulsification energy,anterior chamber inflammation and corneal endothelial cell loss were less in the femtosecond laser group.