一道石家庄二模压轴试题的推广

文章通过对河北省石家庄市2023届高三质量检测(二)中一道压轴试题的探究,得到在一般双曲线和椭圆中的一个与四条直线斜率相关的推广性质.

两个优美的无理不等式

命题1:若正数a,b满足a+b=1,n∈N,n≥3,则有√1+a^(n)+√1+b^(n)≥2√1+(1/2)^(n).命题1的证明用到如下引理:引理1:设a,b∈R^(+).

Quantitative evaluation of enhanced laser tattoo removal by skin optical clearing

Lasers have been widely used for tattoo removal,but the limited light penetration depth calused by high skin scattering property restricts the therapeutic outcome of deep tattoo.Skin optical clearing method,by introducing optical clearing agent(OCA)into skin,has shown some im-provement in the effect of laser tattoo removal.In this study,the enhanced laser tattoo removal has been quantitatively assessed.OCA was applied to the skin of tattoo animal model and Q switched Nd:YAG laser(1064 nm)irradiation was used to remove the tattoo.The skin evaluation instrument(Mexameter probe,MPA580)was applied to measure the content of tattoo pigment before and after laser treatment,and then the clearance rate of pigment was calculated.Further,Monte Carlo(MC)method was utilized to simulate the efecet of skin optical clearing on light transmission in tattoo skin model.By comparing the pigment change of tattoo areas respectively treated with OCA plus laser and single laser,it was found that pigment clearance of the former tattoo area was increased by 1.5-fold.Further,the MC simulation verifed that the reduced light scattering in skin could increase the effective dose of lumninous fux reaching to the deep tattoo regions.It can be concluded from both experiment and theoretical simulations that skin optical clearing technique could improve the outcome of laser tattoo re moval,which should be beneficial for clinical laser tattoo removal and other laser pigment elimination.

椭圆的一个优美的定值性质

试题已知椭圆C:(石家庄市2018届高中毕业班模拟考试(一)理科数学第20题)x^2/a^2+y^2/b^2=1(a>b>0)的左、右焦点分别为F1,F2,且离心率为√2/2.M为椭圆上任意一点,当∠F1MF2=90°时,△F1MF2的面积为1.

Structural performance of a façade precast concrete sandwich panel enabled by a bar-type basalt fiber-reinforced polymer connector

In this study,a novel diagonally inserted bar-type basalt fiber reinforced polymer(BFRP)connector was proposed,aiming to achieve both construction convenience and partially composite behavior in precast concrete sandwich panels(PCSPs).First,pull-out tests were conducted to evaluate the anchoring performance of the connector in concrete after exposure to different temperatures.Thereafter,direct shear tests were conducted to investigate the shear performance of the connector.After the test on the individual performance of the connector,five façade PCSP specimens with the bar-type BFRP connector were fabricated,and the out-of-plane flexural performance was tested under a uniformly distributed load.The investigating parameters included the panel length,opening condition,and boundary condition.The results obtained in this study primarily indicated that 1)the bar-type BFRP connector can achieve a reliable anchorage system in concrete;2)the bar-type BFRP connector can offer sufficient stiffness and capacity to achieve a partially composite PCSP;3)the boundary condition of the panel considerably influenced the out-of-plane flexural performance and composite action of the investigated façade PCSP.

Effects of dietary supplementation of nucleotides from late gestation to lactation on the performance and oxidative stress status of sows and their offspring

Increased metabolic burdens in breeding sows,which are induced by elevated systemic oxidative stress,could increase the need for nucleotides to repair lymphocyte DNA damage;however,de novo synthesis of nucleotides may be insufficient to cover this increased need.This study investigated the effects of dietary nucleotides on milk composition,oxidative stress status,and the reproductive and lactational performance of sows.Forty multiparous sows were assigned to 2 dietary treatments(Control group,and 1 g/kg Nucleotides group)based on a randomized complete block design using their BW at 85 d of gestation as a block.Sows from 2 groups were fed a restricted diet during gestation and ad libitum during lactation.The experiment lasted from 85 d of gestation to 21 d of lactation.The reproductive perfor-mance of sows and the growth performance of suckling piglets were measured.Oxidative stress pa-rameters and milk components were also analysed.Data were analyzed using contrasts in the MIXED procedure of SAS.Sows in the Nucleotides group consumed more feed during the first week(P<0.01)and from 1 to 21 d(P<0.05)of lactation than those in Control group.Correspondingly,the litter weight gain of piglets showed a tendency to increase from cross-fostering to 9 d(P=0.09)and from cross-fostering to 20 d(P=0.10)in the Nucleotides group relative to the Control group.Additionally,the Nucleotides group was higher(P<0.01)than the Control group in the concentrations of uridine 5'monophosphate,guanosine 5'monophosphate,inosine 5'monophosphate,adenosine 5'mono-phosphate and total nucleotides in milk.Furthermore,the Nucleotides group was higher(P<0.01)than the Control group in the serum levels of total antioxidant capacity(P<0.01)for sows at 109 d of gestation and glutathione peroxidase for weaning piglets,but lower at the levels of thiobarbituric acid-reactive substances(P<0.05)in serum of weaning piglets.This study indicated that maternal dietary nucleotides could promote piglet growth,probably due to the higher lactational feed intake and higher concentration of nucleotides in the milk of sows,and lower oxidative stress for both sows and piglets.