首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Mechanistic-empirical pavement design guide for flexible pavements as per the AASHTO design guide requires characterization of subgrade soils using the resilient modulus (MR) property. This property, however, does not fully account for the plastic or permanent strain or rutting of subgrade soils, which often distress the overlying pavements. Soils such as silts exhibit moderate to high resilient moduli properties but they still undergo large permanent deformations under repeated loading. This explains the fallacy in the current pavement material characterization practice. A comprehensive research study was performed to measure permanent deformation properties of subgrade soils by subjecting various soils under repeated cycles of deviatoric loads. This paper describes test procedure followed and results obtained on three soils including clay, silt, and sandy soils. The influence of compaction moisture content, confining pressure, and deviatoric stresses applied on the measured permanent deformations of all three soils are addressed. A four-parameter permanent strain model formulation as a function of stress states in soils and the number of loading cycles was used to model and analyze the present test results. The model constants of all three soils were first determined and these results were used to explain the effects of various soil properties on permanent deformations of soils. Validation studies were performed to address the adequacy of the formulated model to predict rutting or permanent strains in soils.  相似文献   

2.
Optimisation of a novel series of osteoclast ATPase inhibitors led to (2Z,4E)-5-(5,6-dichloro-2-indolyl)-2-methoxy-N-(1,2,2,6,6- pentamethylpiperidin-4-yl)-2,4-pentadienamide (1) that was the most potent compound in an in vitro osteoclast ATPase assay and in human bone resorption assays. Two of the possible geometric isomers have also been prepared and shown to be significantly less potent than 1.  相似文献   

3.
Effects of ifenprodil tartrate, a potent vasodilator, on the autonomic, peripheral and central nerve system were studied in experimental animals. In isolated vas deferens of guinea pigs, the contraction in response to noradrenaline and sympathetic nerve stimulation was competetively antagonized by ifenprodil 10(-7)--10(-5) M (pA2: 7.69 against noradrenaline). Ifenprodil (50 approximately 1,000 mug/kg i.v.) inhibited the contraction of cat nictitating membrane and dog urinary bladder induced by sympathetic nerve stimulation. Ifenprodil (250 approximately 1,000 mug/kg i.v.) lowered adrenaline-induced lethality (ED50: 360 mug/kg). The drug produced a hypermotility of guinea pig uterus, and showed a transient hypertonus of dog gut which was abolished by atropine. Ifenprodil (10 approximately 20 mg/kg i.v.) inhibited the propulsion of charcoal meal in mice. In Shay rats, more than 10 mg/kg i.m. of the drug inhibited the secretion of acid gastric juice and the ulceration. Ifenprodil showed a potent local anesthetic action in the guinea pig cornea and skin. The spontaneous EEG of rabbits showed a resting pattern (0.25 approximately 2 mg/kg i.v.) followed by an arousal pattern (5 approximately 10 mg/kg). Ifenprodil (20 approximately 100 mg/kg p.o.) potentiated a hypnosis induced by barbital, and potentiated pentylenetetrazol, strychnine and picrotoxin induced convulsion. The drug (20 and 100 mg/kg p.o.) lowered the body temperature of rats. From these results it is concluded that ifenprodil produces a blocking action of alpha-adrenoceptors in various smooth muscle preparations and a direct relaxation of the smooth muscle itself without affecting the motor and central nerve systems.  相似文献   

4.
合成了通式为(C26H30NO)3RE(C6H5O7)2(H2O)x,当RE=La~Gd时,x=3,RE=Tb、Dy时,x=4,RE=Ho~Tm时,x=5,RE=Yb、Lu时,x=6的一个系列13种标题稀土配合物。通过元素分析、红外光谱、热重-差热分析、摩尔电导、X射线粉末衍射分析等对配合物的性质进行了表征。  相似文献   

5.
The design, synthesis, and biological evaluation of compounds related to the dopamine (DA) uptake inhibitors: 1-[2-(diphenylmethoxy)ethyl]-4-(3-phenylpropyl)piperazine (1) and 1-[2-[bis-(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine (2) (GBR 12395 and GBR 12909, respectively), directed toward the development and identification of new ligands interacting with high potency and selectivity at the dopamine transporter (DAT) is reported. The substitution of the piperazine ring in the GBR structure with other diamine moieties resulted in the retention of the high affinity of new ligands for the DAT. Some of the modified GBR analogs (e.g. 8, 10, (-)-49, or (-)-50) displayed substantially higher selectivity (4736- to 693-fold) for the dopamine (DA) versus the serotonin (5HT) reuptake site than the parent compounds. The bis(p-fluoro) substitution in the (diphenylmethoxy)ethyl fragment slightly increased the affinity of the ligands at the DA reuptake site but reduced their selectivity at this site (e.g. 9 and 8, 11 and 10, or 17 and 16, respectively). Congeners, such as the series of monosubstituted and symmetrically disubstituted piperazines and trans-2,5-dimethylpiperazines, which lack the (diphenylmethoxy)ethyl substituent lost the affinity for the DAT yet exhibited very high potency for binding to the sigma receptors (e.g.28). The chiral pyrrolidine derivatives of 1, (-)-49, and (+)-49, exhibited an enantioselectivity ratio of 181 and 146 for the inhibition of DA reuptake and binding to the DAT, respectively.  相似文献   

6.
The previously reported oxytocin antagonist L-371,257 (2) has been modified at its acetylpiperidine terminus to incorporate various pyridine N-oxide groups. This modification has led to the identification of compounds with improved pharmacokinetics and excellent oral bioavailability. The pyridine N-oxide series is exemplified by L-372,662 (30), which possessed good potency in vitro (Ki = 4.1 nM, cloned human oxytocin receptor) and in vivo (intravenous AD50 = 0.71 mg/kg in the rat), excellent oral bioavailability (90% in the rat, 96% in the dog), good aqueous solubility (>8.5 mg/mL at pH 5.2) which should facilitate formulation for iv administration, and excellent selectivity against the human arginine vasopressin receptors. Incorporation of a 5-fluoro substituent on the central benzoyl ring of this class of oxytocin antagonists enhanced in vitro and in vivo potency but was detrimental to the pharmacokinetic profiles of these compounds. Although lipophilic substitution around the pyridine ring of compound 30 gave higher affinity in vitro, such substituents were a metabolic liability and caused shortfalls in vivo. Two approaches to prevent this metabolism, addition of a cyclic constraint and incorporation of trifluoromethyl groups, were examined. The former approach was ineffective because of metabolic hydroxylation on the constrained ring system, whereas the latter showed improvement in plasma pharmacokinetics in some cases.  相似文献   

7.
8.
Human growth hormone (HGH) and somatomedin (Sm) concentrations have been studied in a group of newborns. Plasma HGH values were 41.17 +/- 24.26 (SD) ng/ml (14.00-90.00 ng/ml) and the Sm value was 0.59 +/- 0.43 (SD) U/ml (0.18-1.8 U/ml); the difference between these values and the ones observed in normal adults (2.45 +/- 2.53 (SD) ng/ml and 1.16 +/- 0.28 (SD) U/ml respectively) were statistically significant. While growth hormone values were higher than in normal adult controls, somatomedin was significantly decreased. It is possible that the dissociation between human growth hormone and somatomedin in newborn could reflect a reduced biosynthesis of the somatomedin-generating system and consequently a lack of a feed-back control on GH exerted by somatomedin.  相似文献   

9.
A modified endoscopic technique for anterior cruciate ligament (ACL) reconstruction using an autologous patellar tendon graft is described using the early results for 120 patients. A special technique using an oscillating hollow saw allows for the rapid and standardized harvest of cylindrical bone plugs, ensuring safe and adequate femoral press-fit fixation. The complications encountered included one fracture of a bone back on plugging in as well as two cases with revision procedures for interference screw fixation due to insufficient femoral anchorage. Within the framework of a prospective study, all 120 patients underwent a control arthroscopy after the first postoperative year showing viable and mechanically stable grafts in 64 (53.3%) of the patients. In 44 patients (36.7%), viable though somewhat lax grafts were found, whereas the remaining 12 patients (10%) only showed insufficient tissue residues. All of these cases were the result of a ventral misplacement of the femoral insertion site representing the primary complication of transtibial technique. The results of the control arthroscopies showed a highly significant correlation with the clinical results for the IKDC score obtained in a follow-up after an average 29 (18 to 36) months. The results for stability according to the IKDC rating scale showed a normal or near-normal knee function in 76.7%. With regard to the subjective results in the IKDC rating scale, 83.3% of the patients (n = 100) assessed their knee function as normal or almost normal. The location and positioning of the femoral and tibial tunnel were evaluated in an exact radiographic evaluation showing an "ideal position" of the graft in only 94 cases (78.3%). Statistically, a significant correlation of stability with the femoral fixation site could be shown.  相似文献   

10.
11.
A series of seven novel lanthanide(Ⅲ ) nitrato complexes with 4-[ N-(2-methoxybenzylimine)formyl] 1-2, 3- dimethyl-1-phenyl-3-pyazolin-5-one (2mbfa), were synthesized. These complexes were characterized by elemental analysis, molecular mass determination, conductance and magnetic moment measurements, IR, UV-visible, and ^13CNMR spectral studies, In these complexes, the Schiff base, 2mbfa, acts as neutral bidentate ligand by utilizing the carbonyl oxygen and azomethine nitrogen as donor sites. All the three nitrate ions are also coordinated unidentately with 7 coordination for the lanthanide(Ⅲ) ions with a tentative monocapped octahedral geometry for the complexes. All the seven lanthanide(Ⅲ) complexes have a general formula, [ Ln(2mbfa):(NO3)3 ].  相似文献   

12.
13.
邱凤仙  倪良 《冶金分析》2002,22(6):14-16
研究了新试剂(2 苯并噻唑) 3 (4 硝基苯) 三氮烯(BTNPT)与Zn 的反应。在阳离子表面活性剂溴化十六烷基三甲基铵(CTMAB)存在下,于pH10 14的缓冲溶液中,该试剂与锌可形成稳定的橙红色的络合物,其表观摩尔吸光系数为2 7×105,锌含量在0~12μg/25mL范围内符合比尔定律。  相似文献   

14.
用化合物4-(3-吡啶基)-2-巯基咪唑(PMI)修饰碳粉制备了化学修饰碳糊电极,基于该氮杂环巯基化合物对Cu2+络合的选择性,Cu2+可富集于该电极表面。修饰电极经富集后再于-0.4 V还原20 s,阳极化扫描,在0.1 V左右可以获得灵敏的铜阳极溶出峰。其二次导数峰电流与Cu2+在5.0×10-9~2.0×10-5mol/L浓度范围内呈线性关系,检出限可达2.0×10-9mol/L(S/N=3)。采用本法不经过预分离,对成分复杂的阳极泥和铝合金等样品中的铜可进行直接测定。  相似文献   

15.
Spinel ferrite Co_(1-2 x)Ni_xMn_xFe_(2-y)Ce_yO_4(0.0≤x=y≤0.3) nanoparticles(NPs) were prepared by sol-gel auto-combustion method.The synthesized NPs were examined using several techniques such as X-ray diffraction(XRD),field emission scanning electron microscopy(FE-SEM) coupled with EDX and elemental mapping,transmission electron microscopy(TEM),Fourier-transform infrared spectroscopy(FT-IR),and a vibrating sample magnetometer(VSM).The analysis of the crystal structure and the phase identification of samples indicates the formation of spinel cubic phase with the occurrence of CeO_2 as secondary phase when the content of Ce substitution element increases.In addition,all produced samples exhibit cubic symmetry with space group Fd3m.TEM confirms the presence of two phases,i.e.,the cubic spinel ferrite and the cubic cerium oxide(CeO_2).The characteristics of hysteresis loops reveal the soft ferrimagnetic nature of the different synthesized samples.The saturation(M_s) and remanent(M_r) magnetizations fall on increasing the content of substituting elements.Compared with pure CoFe_2O_4 NPs,the value of coercive field(H_c) slightly increases for x=y=0.1 and x=y=0,2 NPs.Then,H_c reduces with further increasing the x and y contents.The squareness ratio is found to be in the 0.528-0.400 interval,indicating the single domain NPs with uniaxial anisotropy for the different produced NPs.The magneto crystalline anisotropy constant(K_(eff)),anisotropy field(H_a),magneton number(n_B) and the demagnetizing field(N) were also determined and discussed.  相似文献   

16.
The luminescent enhancement effect of Na_5Eu(MoO_4)_4 by doping(WO_4)~(2-) has been studied.When the value x in Na_5Eu(Mo_(1-x)W_xO_4)_4 is in 0相似文献   

17.
研究了显色剂 4 ( 2 噻唑偶氮 ) 5 二甲氨基苯胺 (简称TADMA)与铑 的显色反应。结果表明 ,在 pH3 2~ 4 8范围内 ,铑 与TADMA反应形成 1∶2红色络合物 ,加入无机酸后色泽加深 ,络合物的表观摩尔吸光系数为 1 2 1× 10 5,铑质量浓度在 0~ 0 92 μg/mL范围内服从比尔定律。本方法操作简便 ,灵敏度高 ,选择性好 ,常见金属离子在一定范围内无干扰 ,用于催化剂中微量铑的测定 ,结果满意  相似文献   

18.
王晓菊  高烨 《稀土》2012,33(3):55-59
采用聚(苯乙烯-丙烯酰胺)载体氯化钕配合物催化剂催化合成聚4-乙烯吡啶,研究了Al3+/Nd3+摩尔比、单体浓度、不同类型催化剂、反应时间和温度对聚合活性、单体转化率、相对分子量的影响规律。结果表明,Al3+/Nd3+摩尔比为200、单体浓度为0.25 g.mL-1,聚合时间为5h,聚合温度为50℃,催化活性达到最大。氯化钕配合物的催化活性高于稀土氯化物,聚合物载体氯化钕配合物催化性能高于同类小分子体系配合物。并通过傅里叶变换红外光谱(IR)、核磁共振氢谱(H-HMR)、核磁共振碳谱(13C-HMR)、差示扫描量热分析(DSC)测试手段对4乙烯吡啶聚合物结构进行表征。  相似文献   

19.
研究表明,新显色剂1-(6-硝基-2-苯并噻唑)-3-(4-硝基苯)-三氮烯与镉反应,可生成稳定的橙黄色络合物,分别在444nm和530nm波长处有一正一负两个吸收峰,建立以530nm为参比波长,444nm为测定波长的双峰双波长测定法,表观摩尔吸光系数达2.82×105,镉含量在0~280μg/L符合比尔定律,测定了实验室废水和人发中的镉含量,结果满意.  相似文献   

20.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号