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At room temperature, the low cycle fatigue tests for smooth specimens of TC25 titanium alloy under various stress ranges are operated at a CSS280I-20w Electro Hydraulic Servo Universal Testing Machine with a microscopic observation system, and the low cycle fatigue lifetimes are measured. Based upon the analysis of stress-strain hysteresis loop of low cycle fatigue of TC25 titanium alloy, a simplified Manson-Coffin formula is derived according to both the experimental characteristics and the stress-strain constitutive model, the fatigue lifetimes are plotted against stress ranges, and a stress-fatigue life curve for TC25 titanium alloy is obtained by the linear regression analysis method. Finally, the fracture surface morphologies of TC25 specimens are investigated using a JSM-6360 Scanning Electron Microscopy, and the fatigue fracture mechanisms of low cycle fatigue are studied. It shows that the plastic deformations are mainly formed at the accelerated fracture stage, and various shear lips can be observed on the fracture surfaces, which demonstrates that the shear stress results in the final rupture of TC25 titanium alloy. During the fracture of low cycle fatigue, the cleavage nucleation leads to the formation of fatigue crack initiation region, the fatigue crack growth exhibits a mixed transgranular and intergranular crack growth mode, and in the final rupture region, the fracture surface of low cycle fatigue of TC25 titanium alloy appears as a typical semi-brittle fracture mode.

The fatigue crack propagation tests for circular notched compact tension specimens of GH4133B superalloy used in a turbine disk of aero-engine are carried out at room temperature. The test data shows that in the transition region from short to long crack growth, the crack growth rate appears as a fluctuation form with acceleration following deceleration. A quasi harmonic function is constructed to model the fatigue crack growth in the transition region, and the result indicates that such function is suitable to describe the crack growth behavior. A metallographic analysis with respect to microscopic observation for the specimen’s surface suggests that the wave period, that is, a step length of a cycle fluctuation from acceleration to deceleration on the crack growth rate curve is agree well with the intrinsic scale of grain size, which indicates that in the transition region from short to long crack growth, grain boundary plays a dominant role in crack growth rate. Finally, the fracture surfaces of specimen are observed using a scanning electron microscopy. It can be found from the fracture surface morphologies that in the transition region from short to long crack growth, the stress intensity factor range is still lower than the fatigue crack growth threshold ΔKth, the effect of microstructure, such as grain size, grain boundary, secondary phase particle, and inclusion ahead of the crack tip, and the effect of crack closure on crack growth behavior should be considered, the local further plastic deformation at crack tip will meet larger resistance, so some twin bands are observed on the fracture surface. As crack length increases with increasing fatigue cycle, the crack propagation is noted to change from a transgranular crack propagation mode, a mixed transgranular and intergranular crack propagation nature, to intergranular crack propagation manner.

The high cycle fatigue tests for smooth specimens of TC25 titanium alloy under different stress ratios are carried out on a MTS 809 Material Test Machine at a given maximum stress level of 917MPa at ambient temperature, the high cycle fatigue lifetimes for such alloy are measured, and the effects of stress amplitude and mean stress on high cycle fatigue life are analyzed. The initial resistance is measured at the two ends of smooth specimen of TC25 titanium alloy, every a certain cycles, the fatigue test is interrupted, and the current resistance values at various fatigue cycles are measured. The ratio of resistance change is adopted to characterize the fatigue damage evolution in TC25 titanium alloy, and a modified Chaboche damage model is applied to derive the fatigue damage evolution equation. The results show that the theoretical calculated values agree well with the test data, which indicates that the modified Chaboche damage model can precisely describe the accumulated damage in TC25 titanium alloy at high cycle fatigue under unaxial loading. Finally, the high cycle fatigue lifetimes for TC25 titanium alloy specimens at different strain hardening rates are tested at a given stress ratio of 0.1, the effect of strain hardening on fatigue life is investigated based on a microstructure analysis on TC25 titanium alloy, and an expression between fatigue life and strain hardening rate is derived

The short fatigue crack growth tests for circular notched compact tension specimens of GH4133B superalloy used in turbine disk of aero-engine are carried out at ambient temperature and atmospheric pressure. The stress intensity factor ranges and the fatigue crack growth rates at various stress ratios are measured, and the corresponding effective stress intensity factor ranges considering the crack closure effect are calculated. It is shown that the effective stress intensity factor range ΔKeff, can be applied to describe the deceleration and acceleration of crack growth rate during the short crack propagation. The fatigue fracture surface morphologies in the short crack growth region are investigated using a scanning electron microscopy. It is found that there is a cleavage step between two adjacent radial striations, a series of early fatigue striations exist on the cleavage step, and some secondary cracks perpendicular to the direction of main crack propagation emerge on the fracture surface, the superalloy exhibits a mixed fracture mode in the short crack growth region, which reveals the microscopic mechanism of short crack propagation that the fatigue crack growth rate is primarily higher, and then gradually decreases with the propagation of short crack.

A large body of evidence suggests that the inflammatory reaction plays an important role in the pathogenesis of neurodegenerative diseases. Our previous studies described the neuroprotective effects of catalpol in lipopolysaccharide (LPS)-induced inflammatory models, in which catalpol was shown to prevent mesencephalic neuron death and ameliorate cognitive ability animals. To further investigate the protective effect and underlying mechanism of catalpol, astrocytes were pretreated with low (0.1mM) and high dose (0.5mM) catalpol for 1h prior to LPS plus interferon-γ stimulation. Biochemical analyses showed that NO and ROS production and iNOS activity were significantly reduced by catalpol. Data at transcriptional level also demonstrated that catalpol potently attenuated gene expressions involved in inflammation, such as iNOS, COX-2 and TLR4. In addition, our exploration further revealed that the suppressive action of catalpol on inflammation was mediated via inhibiting nuclear factor-κB (NF-κB) activation. Collectively, these results suggest that catalpol can exert inhibitory effects on the inflammatory reaction in astrocytes and that inactivation of NF-κB could be the major determinant for its anti-inflammatory mechanism. Therefore, catalpol may potentially be a highly effective therapeutic agent in treating neurodegenerative diseases associated with inflammation.

The fatigue crack growth tests for nickel-based GH4133B superalloy used in turbine disk of a type of aero-engine are carried out at room temperature. The stress intensity factor ranges and the fatigue crack growth rates at various stress ratios are measured, and the corresponding threshold stress intensity factor ranges are determined. Using the Paris formula, the experiment data of fatigue crack growth are analyzed. It is shown that the fatigue crack growth rate increasing with increasing stress intensity factor range and stress ratio, and a modified Paris formula considering threshold stress intensity factor range can describe the fatigue crack growth behavior precisely. The fracture surface morphologies are investigated using a scanning electron microscope. It is shown that in the crack initiation region, steady growth region and rapid growth region, the fracture surface exhibits a cleavage fracture mode, fatigue striations and an intergranular fracture mode, respectively. Finally, the von Mises stresses and stress intensity factors at the crack tip of specimen of GH4133B superalloy at various external loads and crack lengths are simulated using the finite element method, and the threshold stress intensity factors under different maximal external loads at a certain crack length are calculated. The comparison between test and simulation indicates that the stress intensity factors at the crack tip calculated by the finite element method agree well with experimental data.

Outward delayed rectifier potassium channel and outward transient potassium channel have multiple important roles in maintaining the excitability of hippocampal neurons. The present study investigated the effects of two bufadienolides, Resibufogenin (RBG) and Cinobufagin (CBG), on the outward delayed rectifier potassium current (IK) and outward transient potassium current (IA) in rat hippocampal neurons. RBG and CBG have similar structures and both were isolated from the venom gland of toad skin. RBG inhibited both IK and IA, whereas CBG inhibited IK without noticeable effect on IA. Moreover, at 1 μM concentration both RBG and CBG could alter some channel kinetics and gating properties of IK, such as steady-state activation and inactivation curves, open probability and time constants. These findings suggested that IK is probably a target of bufadienolides, which may explain the mechanisms of bufadienolides' pathological effects on central nervous system.

The temperature sweep tests at defferent frequencies and heating rates, and frequency sweep tests at various temperatures for the samples of poly(methyl methacrylate) are carried out on a dynamic mechanical thermal spectrometer EPLEXOR® 500N-Gabo. The effects of temperature, frequency and heating rate on dynamic mechanical properties of poly(methyl methacrylate) are investigated. The results indicate that the glass transition temperature of poly(methyl methacrylate) increases with increasing frequency from 1 to 100Hz, and increases with increasing heating rate from 3 to 8°C/min as well. The temperature sweep curves at various heating rates suggest that the storage modulus of poly(methyl methacrylate) is non-sensitive at heating rate 3°C/min or 8°C/min, while heating rate is 5°C/min, there exists a critical temperature, within which the storage modulus versus temperature curves depart from each other, and beyond which the curves overlap one another. The glass transition temperature determined by the peak of loss modulus curve is smaller than that defined by the peak of loss tangent. The frequency sweep curves at a constant temperature show that a drop in storage modulus and a peak in loss tangent appear at a certain critical frequency, and the critical frequency increases with increasing temperature. For amorphous polymer, a competitive mechanism between frequency and temperature is observed. Higher temperature accelerates molecular motion, while higher frequency restrains molecular motion, so that the critical frequency corresponding to the peak of loss tangent shifts toward the direction of high temperature.

The uniaxial tensions for foam nickel ceramic specimens with different relative densities are carried out on a CSS-44020 Universal Electronic Test Machine at ambient temperature, and the uniaxial tensile tests at various strain rates and temperatures are performed as well. The effects of relative density, strain rate and temperature on the elastic modulus are investigated. It is found that the elastic modulus of the foam nickel ceramic material increases with the density and stain rate, while decreases with the temperature. Simultaneously, the effects of relative density, strain rate and temperature on the yield strength of the foam nickel ceramic material are studied. It is shown that the yield stress increases with relative density and strain rate, but is reversed with increasing temperature. The comparison between the calculated result and experimental data demonstrates that the theoretical model can well predict the mechanical behavior of foam nickel ceramic material.

The effects of stress, ageing time and ageing temperature on creep behavior of poly(methyl methacrylate) were studied. After annealing above its glass transition temperature for a period of time to eliminate the stress and thermal history, the specimens were quenched and aged at various ageing temperatures for different ageing time, and then the short-term creep tests under different stress levels were carried out at room temperature. The creep strains were modeled by means of time-ageing time equivalence and time-stress equivalence, and the master creep curves were constructed via ageing time shift factors and stress shift factors. The results indicate that the creep rate increases with stress, while decreases with ageing time, and the ageing temperature history obviously affects the creep rate. For linear viscoelastic material, the ageing shift rate is independent on imposed stress, while for nonlinear viscoelastic material, the ageing shift rate decreases with increasing stress. The unified master creep curve up to 540 d at reference state was constructed by shifting the creep curves horizontally along the logarithmic time axis to overlap each other. It is demonstrated that the time-stress equivalence, united with the time-ageing time equivalence, provides an effective accelerated characterization technique in the laboratory to evaluate the long-term creep behavior of physical ageing polymers.

The effect of strain rate on fracture behavior of poly (methyl methacrylate) was investigated. The uniaxial tensile rupture tests for the poly (methyl methacrylate) samples were carried out at different strain rates at ambient temperature. It is found that the elastic modulus of the material increases with increasing strain rate, while the elongation is reversal with strain rate. Simultaneously, there exists a critical strain rate within which the stress-strain curves overlap one another, and beyond which the curves depart from each other. The amount of energy added to the system due to work done by the imposed load was calculated, and the strain energy stored in the material at each strain rate was calculated by the current stress integral with respect to strain. The complementary strain energy, which is the difference between the work and the strain energy, was obtained and was considered to supply the surface energy to create a new crack surface in the polymeric material. It is found that the work done by the imposed load, which is needed for the fracture of poly (methyl methacrylate) sample, decreases with increasing strain rate, and the strain energy decreases with strain rate as well, which demonstrates that the polymeric material at high strain rate is easier to fracture than that at low strain rate. As the strain rate increases, the fracture mode changes from ductile, semi-ductile to brittle mode. The complementary strain energy almost sustains a constant at any strain rate. The density of surface energy, which characterizes the energy per unit area needed for creating crack surface, is a strain rate-independent material constant.

Based on the observations that high temperature accelerates creep rate of polymer while physical ageing plays a reverse role, and that there is an analogy between the influences of stress and temperature on the intrinsic times of polymers, the time-ageing time superposition principle (TASP) and the time-temperature-stress superposition principle (TTSSP) are used to evaluate the long-term creep behavior of poly(methyl methacrylate) (PMMA). PMMA specimens were aged for 2 to 120 hours at identical temperature, their short-term creep strains with 2-hour test duration were measured under various stress levels ranging from 14 to 30 MPa at room temperature, and modeled by means of time-ageing time equivalence and time-stress equivalence. The results show that the creep rate increases with stress, but decreases with ageing time. The ageing time shift factors vary with the stresses at which the shifts are applied. The ageing shift rate is independent on imposed stress in linear viscoelastic region, while it decreases with increasing stress when the material behaves in a nonlinear viscoelastic manner. The master creep compliance curve up to about 1-month at reference ageing time 120 hours and stress 18 MPa, which is nearly 2.5 decades longer than the test duration, is constructed by shifting the creep curves horizontally along the logarithmic time axis. The result illustrates that TTSSP, combined with TASP, provides an effective accelerated test technique for long-term mechanical behaviors of polymers.

The uniaxial tension under various strain rates, creep under various sustained loads, and equalamplitude- strain loading and unloading tests are carried out at room temperature with polyamide 6/nano- SiO2 composite specimens. According to the elasticity recovery correspondence principle, the recovered elastic stresses (strains) in the case of prescribed strain (stress) history are calculated, and the instantaneous elastic constitutive equations are deduced. The nonlinear viscoelastic constitutive relations in single integral form on the basis of the instantaneous elastic constitutive equations are constructed and applied to model the current stress (strain) responses of polyamide 6/nano-SiO2 composite. The theoretic results agree well with the experimental data, which demonstrates that the single integral constitutive relations used in this work can accurately simulate the physical nonlinear viscoelastic properties of polyamide 6/nano-SiO2 composite. Finally, the creep curve at higher stress level is horizontally shifted along logarithmic timescale using a stress shift factor in terms of the time-stress superposition principle and superposed on that at relative lower stress level to form a master creep compliance curve that spans a longer timescale interval than the short-term test curve does, which suggests that TSSP provides an accelerated characterization method for the long-term creep performance of polyamide 6/nano-SiO2 composite.

In this work, the physical aging and its effect on nonlinear creep behavior of poly(methyl methacrylate) are presented. After annealing above Tg to release the previous thermal and stress history, the samples were quenched to 60oC, aged for various times, and were then tested at three different stress levels (22MPa, 26MPa and 30MPa) at room temperature of 27oC. At each stress level, the creep strain was converted to compliance and measured as a function of test time and aging time. The test results show that higher stress accelerates creep rate of the material while physical aging plays a reverse role. The time-aging time superposition is applicable to build a master creep compliance curve at each stress level, and it is demonstrated that the shift rate deceases with increasing stress. Moreover, based on the time-stress superposition principle, a unified master curve was constructed by further shifting the sub-master curves at 30MPa and 26 MPa to a reference stress level of 22MPa.

Temperature induced change, and stress induced change as well, in intrinsic timescale were investigated by nonlinear creep tests on poly(methyl methacrylate). With four different experimental temperatures, from 14 to 26 degrees centigrade, time-dependent axial elongations of the specimen were measured at seven different stress levels, from 14 MPa to 30 MPa, and modeled according to the concept of time-temperature-stress equivalence. The test duration was only 4000 seconds. The corresponding temperature shift factors, stress shift factors and temperature-stress shift factors were obtained according to the time-temperature superposition principle (TTSP), the time-stress superposition principle (TSSP) and the time-temperature-stress superposition principle (TTSSP). The master creep compliance curve up to about two-year at a reference temperature 14 degrees centigrade and a reference stress 14 MPa was constructed by shifting the creep curves horizontally along the logarithmic time axis using shift factors. It is shown that TTSSP provides an effective accelerated test technique in the laboratory, the results obtained from a short-term creep test of PMMA specimen at high temperature and stress level can be used to construct the master creep compliance curve for prediction of the long-term mechanical properties at relatively lower temperature and stress level.

The uniaxial tensile creep of a commercial grade Poly(methyl methacrylate) was measured for 4000 seconds under various temperatures and stress levels ranging from 14 oC to 26 oC and 6 MPa to 32 MPa. The resultant creep compliance curves depart from each other for stresses beyond a critical value which varies with temperature, indicating nonlinear viscoelastic behavior. The time-temperature-stress superposition principle (TTSSP) was used to construct a smooth master compliance curve with a much longer time-scale interval from the short-term tests at higher stresses and temperatures. It is shown that the master curve covers a period of over 290 days, which is nearly 3.9 decades longer than the test duration. Moreover, it is verified that the time-temperature shift factors are dependent on stresses at which the shifts are applied, and that the time-stress shift factors are dependent on reference temperatures.

The numerical solution procedures for viscoelastic material subjected to deformation and mechanical damage were concerned. The analyses were based upon the constitutive model of viscoelastic material with damage derived from the elasticity recovery correspondence principle and Lemaitre-Chaboche’s damage model. The uniaxial tensile tests for specimens made of polymeric materials were carried out under different strain rates at room temperature, and the stress vs. strain curves were simulated by the constitutive model of viscoelastic material without damage. The results show that the stresses predicted by the model fit with experimental stresses moderately even if damage is not considered when the strain is smaller than a certain strain threshold. But when the strain exceeds this threshold, the damage parameter should be introduced into the constitutive model. It is verified that the constitutive model with damage proposed can more accurately estimate the stress response of a class of viscoelastic particle-reinforced composite, such as solid propellent, than the constitutive model without damage.

The mechanical behaviors were investigated by nonlinear creep tests of poly(methyl methacrylate) under different temperatures. The test duration was 4000 seconds. The corresponding temperature shift factors, stress shift factors and temperature-stress shift factors were obtained according to time-temperature superposition principle, the time-stress superposition principle and the time-temperature-stress superposition principle (TTSSP). The master creep compliance curve up to about 1-month at a reference temperature 22 degrees centigrade and a reference stress 14 MPa was constructed, and the effect of stress-induced damage evolution on the long-term creep behavior of polymeric material was accounted. It was shown that TTSSP provides an effective accelerated test technique in the laboratory, the results obtained from a short-term creep test of poly(methyl methacrylate) specimen at high temperature and stress level can be used to construct the master creep compliance curve for prediction of the long-term mechanical properties at relatively lower temperature and stress level, and the master creep compliance curve with damage considered can be applied to accurately characterize the long-term creep behavior of nonlinear viscoelastic polymer.

The effects of polytetrafluoroethylene (PTFE) content on water-absorptivity, tensile strength, fiexural strength, and notched impact strength of polytctrafiuoroethylene/polyamide 6 (PTFE/PA6) and polytetrafluoroethylene/polyamide 66 (PTFE/PA66) blends were investigated by water immersion test, uniaxial tensile test, three-point test, and Charpy impact fracture test. The water-absorptivity in the blend decreases with increasing PTFE content, which indicates that the PTFE phase restrains the polyamide phase from water absorption. For water-free blends, the addition of PTFE causes a reduction in tensile strength, while for water-absorbed PTFE/PA6 blends, the tensile strength increases with increasing PTFE. Simultaneously, the absorbed water improves the elongation, but results in a notable reduction in fiexural strength of the blends. Although the addition of PTFE causes a reduction in notched impact strength of the blends, as compared to pure polyamide, the absorbed water has little effects on the notched impact strength of the blends. Finally, the effects of temperature and loading frequency on complex viscosity parameters of PTFE/PA6 and PTFE/PA66 melts were tested. It is found that the complex viscosity of PTFE/PA6 melt is reversed with increasing temperature and shear velocity, but that of PTFE/PA66 melt increases approximately in exponential form with increasing temperature. To fill polyamide with suitable mass percentage of PTFE can effectively reduce the viscosity of blend, and as a result, the molding and processing properties are improved.

Fracture surface morphologies of nano-SiO2/epoxy composite with different weight percentage of SiO2 are investigated using scanning electron microscopy. Two types of curing agent, dimethylbenzanthracene (DMBA) and methyltetrahydrophthalic anhydride (MeTHPA), are individually used for preparing the composites. It is found that the fracture surface morphology of the composite cured by DMBA shows as radial striations, which suggests a rapid brittle fracture mode, while the fracture surface morphology of the composite cured by MeTHPA shows as regularly spaced ‘rib’ markings, which indicates a stick–slip motion during the fracture process. Furthermore, the uniaxial tensile behavior under constant loading rate and ambient temperature are investigated. It is shown that the elastic modulus of the composite cured by DMBA firstly increases, and then decreases with the mass fraction of nano-SiO2 particles, but the elongation of the composite cured by MeTHPA is reversed with increasing fraction of nano-SiO2 particles. For nano-SiO2/epoxy composite cured with MeTHPA that possesses a suitable fraction of nano-SiO2, an excellent synthetic mechanical property on elastic modulus and elongation is obtained.

A simple optical technique is used to quantify creep crazing damage in a uniaxially stressed transparent glassy polymeric sheet of polymethyl methacrylate (PMMA) at room temperature. The areal craze densities are taken as a measure of the crazing damage. It is shown that the crazing damage increases with nominal applied stress and creep time. The crazing initiation time and the crazing damage evolution equation for PMMA is modeled from a mechanical viewpoint and the results are used to predict the nonlinear creep behavior of PMMA with growing damage. The predictions are in good agreement with the test results.

Voltage-gated sodium channels (VGSCs) play important roles in maintaining the excitability of hippocampal neurons. The present study investigated the effects of resibufogenin (RBG, a main component of bufadienolides) on voltage-gated sodium channel currents (I(Na)) in rat hippocampal neurons using whole-cell patch clamp recording. According to the results, RBG activated I(Na) in a concentration-dependent manner. RBG at 1 μM concentration could alter some channel kinetics of I(Na), such as activation thresholds, steady-state activation and inactivation curves, time constant of recovery, and activity-dependent attenuation of I(Na). RBG influenced peak amplitude, overshoot and half-width of the evoked single action potential, and simultaneously lessened the firing rate of evoked repetitive firing. These findings suggested that I(Na) is probably a target of RBG, which may explain the mechanisms for the pathological effects of RBG on central nervous system.

Based on the observation that high stress results in increasin g creep rate of polymeric material, which is analogous to the time-temperature equivalence, where high temperature accelerates the process of creep or relaxation of polymer, the time-stress equivalence is investigated. The changes of intrinsic time in polyme r induced by temperature and stress are studied using the free volume theory, and a clock model based on the time-temperature and time-stress equivalence is constructed to predict the long-term creep behavior of polymer . Polypropylene is used for th is work. The specimens with shape of dumbbell are formed via injectio n molding. The short-term creep tests u nder various stress levels are carried out at ambient temperature. The creep strain s of specimens are modeled according to the concept of time-stress equivalence, and the corresponding stress shift factors are calculated. A master creep curve is built by the clock model. The result indicates that the time-stress superposition principle provides an accelerated characterization method in the laboratory. Finally, the time-dependent axial elongations at sustained stress levels, whose values are close to the tensile strength of polypropylene, are measured. The three phases of creep, i.e., the transient, stead y state and accelerated creep phases, are studied, and the application and limitation of the time-stress superposition principle are discussed. Keywords: rheology, intrinsic time, temperature, stress, polypropylene

To improve capability of appendiceal mucocele diagnosis via analyzes its clinical, pathological basis and radiological results.Summarize 18 cases with pathological diagnosed appendiceal mucocele in PUMC Hospital since January 1985 till september 2004, including 4 males and 14 females (1:3.5), age ranged from 31 to 78 yrs old (average 59.8 years old). Eleven cases underwent barium enema, in which 9 cases received abdominal CT scanning and 1 case received CT virtual colonography.(1) CLINICAL RESULTS: 8 cases (44.4%) had right lower abdominal pain, 12 cases (66.7%) had palpable abdominal mass. (2) Radiological results: barium enema showed extrinsic oppressed filling defect at the end of cecum without destruction of mucosa; CT scanning showed right lower abdominal cystic mass, 75% with cystic wall calcification, massive septal mucous ascites was seen in one case with pseudomyxoma peritonei; CT virtual colonography showed clearly the extra cavity and intracavity changes at cecum. (3) Pathological results: simple mucocele (4 cases, 22.2%), mucous cystadenoma (12 cases, 66.7%) and mucous cystadenocarcinoma (2 cases, 11.1%)There are four pathological types in appendiceal mucocele. Radiological characters of appendiceal mucocele have distinct specificities while its clinical ones not. Radiological procedures are vital for correct clinical diagnosis.

While clinicians are devoting themselves to the study of the behaviour of ovarian cancer as well as to the search for more effective therapeutic modalities, little attention has been paid to an important route of metastasis in this group of diseases: retroperitoneal spread through the lymphatic pathway. The purpose of this report is to present a 5-year experience of a prospective study on lymph node metastasis in patients with ovarian cancer through retroperitoneal lymphadenectomy at the Peking Union Medical College Hospital. From June 1982 through May 1987, retroperitoneal lymph node dissection was performed in 105 cases of ovarian cancer. Seventy-seven (73.3%) were histologically diagnosed as cancer of epithelial origin, and 28 (26.7%) as germ-cell tumours. The overall incidence of retroperitoneal positive nodes was 54.3% (57/105). The incidence of positive pelvic nodes was 46.7% (49/105), and that of positive para-aortic nodes was 37.5% (30/80). In 69 patients who underwent systemic lymphadenectomy, 39 were found to have glandular involvement; in these 39 patients both aortic and pelvic nodes were positive in 19 cases (48.7%), aortic nodes were positive and pelvic nodes negative in 7 cases (18.0%), and pelvic nodes were positive and aortic nodes negative in 13 cases (33.3%). Preoperative lymphography was performed in 30 cases. The positive and negative correspondence rates with the pathological findings were both 83.3%. In 38 cases in which the primary cancer originated in the left ovary, 17 (44.7%) were found to have positive pelvic nodes, whereas in 25 cases with primary cancer arising in the right ovary only 2 (8%) had metastasis of the ipsilateral pelvic nodes. The lymph nodes obtained from 22 patients with positive nodes and sufficient preoperative chemotherapy were carefully examined under the microscope for the effects of the drugs. Some cellular degeneration of the lymph node metastasis was observed in only one of the 15 cases of epithelial cancer, and no response at all was noted in three cases of immature teratoma. Cellular degeneration accompanied by extensive necrosis was demonstrated in the metastatic tumours of the lymph nodes in all four cases of endodermal sinus tumour. Seventy-two patients were followed-up for at least 2 1/2 years. The rate of complete remission was 46.7% (14/30) in patients with negative nodes, but only 33.3% (14/42) in those with positive nodes. However, the difference was not statistically significant.