牛牙的自然酸蚀与电化学人工龋的比较

进行了牛牙的自然酸蚀和电化学人工龋的初步研究 ,结果表明 ,酸的作用只能使牙釉质脱矿 ,只有在酸和电的双重作用下 ,才能形成牙釉质的类龋洞 .在人工电化学腐蚀中 ,不同浓度的羧甲基纤维素 (CMC)致龋凝胶对Ca溶出量影响较大 ,以 0 .5 %CMC致龋凝胶龋损深度最大 ,牙的Ca溶出量为自然酸蚀的 3～ 4倍 .在人工电化学腐蚀中 ,阳极pH值呈下降趋势 ,阴极pH值呈上升趋势 ,氟化物能减少阳、阴极间pH差值 .氟化物在自然酸蚀和人工电化学腐蚀中均能显著抑制牙Ca的溶出 ,在开窗区几乎看不到脱矿现象 .

Segmental Duplications Are Common in Rice Genome

Segmental duplications on rice (Oryza sativa L.) chromosomes 8, 9, 11, and 12 were studied by examining the distributions of sequences resolved by 13 probes detecting multiple copies of DNA sequences. Four of the hybridization bands detected by a repetitive sequence probe, rTRS, were mapped to the ends of all the four chromosomes. Two or three of the bands detected by each of the other 12 probes were also mapped to different chromosomes. The bands detected by the same probe usually occurred in similar locations of different chromosomes. Loci detected by different DNA probes were often similarly arranged on different chromosomes. Chromosomes 8 and 9 showed colinearity of marker loci arrangement indicating a possible common origin. A segment on chromosome 9 was also very similar to the previously reported duplicated fragments on the ends of chromosomes 11 and 12 which were also detected in this study, indicating a likely common origin. Moreover, the various degrees of distributional similarity of the segments suggest a complex relationship among the chromosomes in the evolution of the rice genome. These results support the proposition that chromosome duplication and diversification may be a mechanism for the origin and evolution of the chromosomes in the rice genome.

Synthesis and Structural Characterization of a Novel Two-Dimensional Heterometallic Coordination Polymer Nd_2Zn_3(EDTA)_3(H_2O)_( 11)·12H_2O

A novel two dimensional heterometallic coordination polymer, Nd 2Zn 3(EDTA) 3(H 2O) 11 ·12H 2O (EDTA= ethylenediamine N,N,N',N' tetraacetate) was synthesized and characterized. In the compound, each Nd 3+ is connected to three Zn 2+ through three carboxylate bridges, while each Zn 2+ has two Nd 3+ neighbors. In this way, a macrocycle involving six neodyium and six zinc ions is produced. The cycles are connected each other to form a two dimensional sheet. These sheets are further linked into a three dimensional network by the water molecules between the layers through rich hydrogen bonding.

An inverse method for underwater bottom topographyby using SAR imagery

Interaction between current and underwater bottom topography leads to roughness of the sea surface, which in turn yields variation of the radar scattering echo. By using the continuity equation and weak hydrodynamic interaction theory in the relaxation time approximation, the spatial variation of the radar scattering cross-section has been proved as proportional to the gradient of current velocity. The current direction is first determined by using two-dimensional (2-D) correlation of spatial variation of backscattering measured by the SAR imagery, as the priori knowledge of the current direction is not available. The inverse algorithm to successively derive 2 - D underwater bottom topography from the SAR imagery is developed. As an application, the SAR SIR- C image over the sea area of Hong Kong, China is studied.

A carbon nanoparticle-peptide fluorescent sensor custom-made for simple and sensitive detection of trypsin

Herein,we report a novel sensor to detect trypsin using a purpose-designed fluorescein-labelled peptide with negatively charged carbon nanoparticles(CNPs)modified by acid oxidation.The fluorescence of the fluorescein-labelled peptide was quenched by CNPs.The sensor reacted with trypsin to cleave the peptide,resulting in the release of the dye moiety and a substantial increase in fluorescence intensity,which was dose-and time-dependent,and trypsin could be quantified accordingly.Correspondingly,the biosensor has led to the development of a convenient and efficient fluorescent method to measure trypsin activity,with a detection limit of 0.7 mg/mL.The method allows rapid determination of trypsin activity in the normal and acute pancreatitis range,suitable for point-of-care testing.Furthermore,the applicability of the method has been demonstrated by detecting trypsin in spiked urine samples.

Transgenic mice overexpressingγ-aminobutyric acid transporter subtypeⅠ develop obesity

Transgenic mice ubiquitously overexpressing murine γ aminobutyric acid transporter subtype Ⅰ were created. Unexpectedly, these mice markedly exhibited heritable obesity, which features significantly increased body weight and fat deposition. Behavioral examination revealed that transgeinc mice have slightly reduced spontaneous locomotive capacity and altered feeding pattern. Tills preliminary finding indicates that the inappropriate level of γ-aminobutyric acid transporters may be directly or indirectly involved in the pathogenic mechanism underlying certain types of obesity.

A new method to directly invert the elastic parameters

The aim of seismic data inversion is to assess the physical parameters (including density, elastic parameters and viscous elastic parameters). Defining the best assessing value to be a kind of parameters set, it is simulated that the synthesized seismic records are the most fit to those which were recorded in fields. A new way of directly inversion for elastic parameters has been brought forward in the context. It is suitable to the inversion of elastic parameters in anisotropic media (HTI). It is totally different from those depicted in the previous approaches. In order to classify the strata properties, it utilizes both PP wave and PSV wave to inverse the strata elastic parameters (C11 and C33). It could be called as the inversion of elastic wave equation.

NUMERICAL SIMULATIONS OF OCEANIC ELEMENTS IN THE SCS AND ITS NEIGHBORING SEA REGIONS FROM JANUARY TO AUGUST IN 1998

Studies on oceanic conditions in the South China Sea (SCS) and adjacent waters are helpful for thorough understanding of summer monsoons in East Asia. To have a 3-dimensional picture of how the oceanic currents vary, the oceanic elements in the South China Sea (SCS) and its neighboring sea regions in January ~ August 1998 have been simulated by using the improved Princeton University Ocean Model (POM) in this paper. The main results are in good agreement with that of ocean investigations and other simulations. The results show that the SCS branch of the Kuroshio Current is an important part in the north SCS from January to August; the SCS warm current is reproduced clearly in all months except in winter; there always exists a large-scale anti-cyclonic vortex on the right of the Kuroshio Current from January to August. In the model domain, the surface currents of the SCS have the closest relations with the monsoon with an apparent seasonal variation. In addition, the developing characteristics of the SST in the SCS and its neighboring sea regions before and after the summer monsoon onset are also well simulated by the improved POM. Those are the foundation for developing a coupled regional ocean-atmospheric model system.

Clinical Applications of Serum Anti-Mullerian Hormone€Measurements in Both Males and Females:An Update

Infertility is one of the most common non-communicable diseases,affecting both men and women equally.Ovarian reserve,the number of primordial follicles in the ovaries is believed to be the most important determinants for female fertility.Anti-Mullerian hormone(AMH)secreted from granulosa cells of growing follicles is recognized as the most important biomarker for ovarian reserve.Ovarian reserve models have been developed using AMH and other hormonal indicators,thus childbearing plans and reproductive choices could be arranged by women.In assisted reproductive technology cycles,measurement of AMH helps to predict ovarian response and guide recombinant follicle-stimulating hormone dosing in women.Serum AMH level is increasingly being recognized as a potential surrogate marker for polycystic ovarian morphology,one of the criteria for diagnosis of polycystic ovarian syndrome.AMH is also secreted by Sertoli cells of testes in men,and AMH measurements in the prediction of surgical sperm recovery rate in men have also been investigated.AMH levels are significantly higher in boys than in girls before puberty.Therefore,serum levels of AMH in combination with testosterone is used for the differential diagnosis of disorders of sex development,anorchia,non-obstructive azoospermia,and persistent Mullerian duct syndrome.Recently,serum AMH measurements have also been used in fertility preservation programs in oncofertility,screening for granulosa cell tumors,and prediction of menopause applications.In this review,we will focus on clinical application of AMH in fertility assessments for healthy men and women,as well as for cancer patients.

Simulation of 3D fracture propagation under I-II-III mixed-mode loading

Fracture propagation under mixed-mode loading conditions prevails in many natural geological processes and deep engineering projects,while the corresponding numerical simulation is very challenging in rock mechanics,especially in 3D cases.In most previous studies,the complexity of 3D fracture geometry was over-simplified,and model III loading was often not considered.In this study,we propose to use an efficient stress-based Sch€ollmann criterion combined with Displacement Discontinuity Method(DDM)to model 3D fracture propagation under arbitrary I+II+III mixed-mode loading conditions.A novel curve-smoothing algorithm is developed to smoothen the fracture front during propagation,which significantly enhances the model's ability in dealing with complex 3D fracture geometry.In particular,we adopt two different solution schemes,namely staggered and monolithic,to simulate mode I fracture propagation in the case of hydraulic fracturing.The accuracy,efficiency and convergency of the two solution schemes are compared in detail.Our research findings suggest that the degree of coupling between fracture aperture and fluid pressure in hydraulic fracturing lies somewhere between one-way and two-way,which favors the staggered solution scheme.To further test our new model,we provide three additional numerical examples associated with 3D fracture propagation under various mixed-mode loading conditions.Our model shows excellent performance in efficiently locating the new fracture front and reliably capturing the complex 3D fracture geometry.This study provides a generic algorithm to model high-fidelity 3D fracture propagation without simplifying fracture geometry or loading conditions,making it widely applicable to fracture-propagation-related problems.

具有宽频与可控微波吸收性能的石墨烯空心微球的自组装

用简单高效的两步法制备了一种包覆有四氧化三铁的还原石墨烯空心微球(Air@r GO€Fe_3O_4)。两步法包括油包水乳化技术和高温煅烧技术。Air@r GO€Fe_3O_4空心微球的介电损耗和磁损耗优异,使其具有良好的微波吸收性能。空心微球在石蜡中的添加量为33.3%、厚度为2.8 mm的微球在10 GHz处有最小反射率,为-52 d B,反射率小于-10 d B的频率范围为7.5~14.7 GHz。调节各成分的配比和样品厚度可控制空心微球的吸波性能。随着四氧化三铁含量的提高,微球的最小反射率的峰值位置向高频移动。Air@r GO€Fe_3O_4空心微球有吸收频率范围宽、吸收强度大以及吸波性能可调控等优点,使其成为具有潜在应用价值的高性能吸波材料。

ABR Flow Control Algorithm in ATM Networks: a Neural Network Approach

A Neural Network( NN ) approach to ABR flow control algorithm in ATM networks is proposed. The NN predicts the queue length, its variation and possible cell loss, then regulates the source rate adaptively. Therefore, more appropriate value of the explicit rate can be determined in the corresponding field of the RM cells. This approach performs better than the traditional static feedback control. Additionally, the performance of this algorithm under CBR background traffic is discussed, and the simulatino results show that the neural network is also efficient.

Relationship between the burden of pneumocystis carinii, the inflammatory reaction and lung injury in pneumocystis carinii pneumonia

To study the relationship between the burden of Pneumocystis carinii (P carinii) and the inflammatory reaction and biochemical markers in bronchoalveolar lavage fluids (BALF)in a rat model of P carinii pneumonia (PCP) Methods Clean grade 50 male Sprague Dawley rats were immunosuppressed by a subcutaneous injection of 25mg cortisone acetate twice a week for 8-12 weeks; the PCP model was successfully induced in 14 rats The inflammatory reaction and biochemical markers of the activity of lactate dehydrogenase (LDH), alkaline phosphatase (ALP) and type Ⅳ collagenase (matrix metalloproteinases, MMP 2, MMP 9) as well as the values of total protein (TP) and albumin (ALB) in BALF between the mild burden group of P carinii (involved alveoli <25% per 100 alveoli, Group A) and the moderate to severe burden group (involved alveoli ≥25% per 100 alveoli, Group B) were measured The other six clean grade SD rats served as normal control group (Group C) Results The total white cell count in BALF was higher in Group B [(6 8±1 7)×10 6/L] than in Group A [(3 8±1 2)×10 6/L] ( P <0 01); however, there were no differences in white cell differentiation Assays of biochemical markers showed that ALB in BALF in Group B (0 893±0 469?g/L) was increased in comparison with Group A (0 262±0 169 ?g/L); it was only 0 026±0 021?g/L in Group C The contents of TP and activities of LDH were higher in Group B (TP 1 756±0 706?g/L, LDH 2580±550?U/L) than in Group A (TP 0 784±0 553?g/L, LDH 1410±620?U/L); the values of TP and LDH were 0 063±0 020?g/L and 370±250?U/L respectively in Group C The activity of Type Ⅳ collagenase, including MMP 2 and MMP 9, was higher in Group B than in Group A ( P <0 01) (MMP 2: 1102±169 grey value vs 459±274 grey value; MMP 9: 1218±257 grey value vs 449±225 grey value) There was no activity of Type Ⅳ collagenase in BALF of Group C No statistically significant difference was observed in ALP between the groups B and A Conclusions These results indicate that there is a significant correlation between the burden of P carinii in lung tissues and the inflammatory reaction as well as biochemical markers of the resultant activity of lung injury

Numerical Investigation of Dynamic Effects on Unsteady Flow Measurements Using a Two-Dimensional Probe

WTFZ] The dynamic effects in measurements of unsteady flow when using a probe with quasi-steady calibration curves has been investigated in this paper by numerical simulation of the compressible flow around a fixed two-dimensional 3-hole probe. The unsteady velocity and pressure distributions, as well as the hole-pressures, are calculated for high frequency flow variations. The measurement errors caused by the dynamic effects indicate that considerable measurement errors may occur for high frequency flow fluctuation, e.g., 2000Hz, especially, when the flow around the probe head approaches separation. This work shows how numerical simulation can be used to investigate and correct for the dynamic effects.[

Effect of cobalt substitution on structure and magnetic properties of Nd0.4Zr0.6Fe10-xCoxSi2（x =0-3） alloys and their ribbons

This study reports the stabilization of the RFe12-type based compounds where part of R and Fe are substituted with Zr and Co and Si, respectively, in order to examine whether these rare-earth-lean materials are suitable for applications as permanent magnets. Structural and magnetic characterization of the family of alloys with the general formula Nd0.4 Zr0.6 Fe10-xCoxSi2(x = 0 -3) and their melt-spun ribbons were carried out using X-ray diffraction and M€ossbauer spectroscopy. The ThMn12-type structure is obtained for all samples as the majority phase with a minority a-Fe(CoSi) phase(less than 5 wt%) as it was estimated by XRD for x = 1 and 2. The Curie temperature increases linearly with Co substitution from 561 K for x = 0 to 712 K for x = 3. The saturation magnetization decreases slightly from 130.5(x =1)to 129.1 A·m2/kg(x=3), while the anisotropy field is following the same trend.

Estimation of the True Cost of Living Index of food consumption for Chinese urban consumers

This paper studies the True Cost of Living Index(TCLI)of food consumption for all income groups of urban households in China from 1997 to 2012.Based on the Generalised Fechner-Thurstone direct utility function,this paper estimates the TCLI under variable preference assumptions,and also decomposes the total bias of the traditional Laspeyres Price Index(LPI)estimation of TCLI into substitution bias and preference variation bias.For all income group households,the estimated preference variation bias is found to be quite substantial.According to the finding,when it is necessary to apply the cost of living adjustment clause in any public welfare programmes,the TCLI calculation compatible with preference variation may be more appropriate than the usual Laspeyres Consumer Price Index estimation.