Structure and Magnetocaloric Effect in Tb（ Co1-xSnx）2 Alloys

Recently,researchonmagnetocaloriceffect(MCE)hasattractedagreatdealofinterestinrare earth(RE)basedcompoundsbecauseoftheirenergy efficiencyandenvironmentalsafetyformagneticrefrig eration.Afirst ordermagneticphasetransitionwas foundintheintermetalliccompoundsRECo2(RE=Er,Ho,Dy)withMgCu2typestructure[1,2],leadingtoa largemagneticentropychangeforthesecompounds,whereasasecond ordertransitionwasfoundinTbCo2andGdCo2.IntheintermetalliccompoundsRECo2,theloweringofd electronconcentrationbythesubst…     

Structural Analysis and Magnetic Properties of Gd-Doped Li-Ni Ferrites Prepared Using Rheological Phase Reaction Method

A series of Gd-doped Li-Ni ferrites with the formula of LiNi0.5GdxFe2-xO4 where x = 0.00 - 0.08 in steps of 0.02, were prepared by thermolysis of oxalate precursors obtained by rheological phase reaction. The structure, morphology, and the magnetic properties of the samples were characterized by powder X-ray diffraction （XRD）, atomic force microscopy （AFM） and a vibrating sample magnetometer （VSM）. A single spinel phase was obtained in the range of x = 0.00 - 0.04. The lattice parameters of the Gd-doped samples were larger than that of pure Li-Ni ferrite, and increased in the range of 0.00 ≤ x ≤ 0.04, then decreased up to x = 0.08, because of the formation of the secondary phase （Gd- FeO3）. All samples were spheric particles with an average size of about 100 nm, but agglomerated to some extent. The hysteresis loops indicated that the saturation magnetization decreased gradually with increasing Gd content, while the variation of coercivity was related to the microstructure of the Gd-doped samples.     

Structural,electrical and magnetic studies on Y-Fe-O system

The compounds of iron substituted yttrium oxide systems have been prepared for the importance in the field of magneto electric materials.The polycrystalline samples of Y2-xFexO3-y(x=0.1,0.2) were prepared by solid-state reaction method.The single-phase formation of these compounds was confirmed by X-ray diffraction studies.It was found that the samples crystallized in tetragonal phase and the lattice parameters were calculated as a=1.0559(7) nm,c=1.0832(9) nm for Y1.9Fe0.1O3-y and a=1.0545(6) nm,c=1.0841(8)...     

单相Sm掺杂BaTiO3陶瓷的结构研究

采用高温固相反应法,在1 400℃/12h烧结条件下制备了具有Ti空位补偿的Ba1-xSmxTi1-x/4O3(BST;x=0.02~0.07)陶瓷。利用XRD对BST陶瓷的晶体结构进行表征,并在532和638nm两种激发波长下对其进行拉曼光谱测试。结果表明:当x≤0.07时,所有的BST陶瓷均表现为单相钙钛矿结构,并且随着Sm含量的增加,其晶体结构由四方相(x≤0.06)转变为立方相(x=0.07);不同激发波长下的拉曼测试证实高频谱来自稀土Sm^3+的荧光效应。     

Magnetocaloric effect of(Tb_(1-x)Ce_x)Co_2 alloys in low magnetic field

The phases in alloys(Tb1-xCex)Co2 with x=0,0.1,0.2,0.3,0.4 and 0.5 were investigated by X-ray diffraction analysis,and the magnetocaloric effect for x=0-0.4 was studied by magnetization measurement.The samples were almost single phase with MgCu2-type cubic structure.The magnetization decreased with the increase of Ce.The Curie temperatures(Tc) of Tb1-xCexCo2 alloys with x from 0.1 to 0.4 were 180,165,160 and 152 K,respectively.For x=0.5 in the range from 100 K to 230 K,the point of magnetic transition was n...     

Yb掺杂对热电化合物Ca_(3-x)Yb_xCo_4O_(9+δ)电性能的影响

采用溶胶凝胶法合成Ca3-xYbxCo4O9+δ(x=0,0.15,0.30,0.45)化合物粉体,以粉体为原料结合放电等离子烧结(SparkPlasmaSinte-ring,SPS)制备出致密的块体材料。研究了Yb掺杂对热电化合物电传输特性的影响。结果表明:在300～850K温度范围内,每个样品的See-beck系数又随着温度的升高而单调增大,而Yb取代Ca可使材料的电阻率(ρ)和Seebeck系数同时增加,这是因为三价的Yb3+取代二价的Ca2+将使化合物的载流子浓度降低,当x=0.30时,材料的功率因子最佳,850K时达到0.32×10-3W.K-.2m-1。     

Preparation and Ionic Conductivity of Ultrafine Li2+xRExSi1-xO3 by Sol-Gel Method

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Effect of electron traps on long afterglow behavior of Sr3Al2O6:Eu0.012+,Dy0.02-x3+,Hox3+

The long persistent phosphors Sr3Al2O6:Eu0.012+,Dy0.02-x3+,Hox3+ (x=0, 0.01, 0.02) were prepared by a high temperature solid state reaction. All samples showed a broad band emission peaking at ~510 nm, which could be ascribed to Eu2+ transition between 4f65d1 and 4f7 electron configurations. With the increase of substitution of Ho3+ ions for the Dy3+ ions in the as-prepared phosphors Sr3Al2O6:Eu0.012+,Dy0.02-x3+,Hox3+ (x=0, 0.01, 0.02), the initial intensity of the afterglow obviously decreased. From the thermoluminescence (TL) curves of the samples, we concluded that codoped Ho3+ ions led to a decline of the trap depth and redistribution of the trap. This may be responsible for the change of afterglow of Sr3Al2O6:Eu0.012+,Dy0.02-x3+,Hox3+ (x=0, 0.01, 0.02).     

La1-xNaxMnO3的磁电性质研究

采用固相反应法制备了La1-xNaxMnO3(x=0.05,0.15,0.33)多晶样品。通过测量XRD(X射线衍射)谱、R-T(电阻-温度)曲线、M-T(磁化强度-温度)曲线和ESR(电子自旋共振)曲线,研究了La位Na+离子替代对体系的电性和磁性的影响。实验结果表明:体系伴随绝缘体-金属相变出现顺磁-铁磁相变,随着La位Na+离子替代量的增加,样品的电阻值先减小后增大,磁化强度先增大后减小;随着La位Na+离子替代量的增加,居里温度单调升高;居里温度附近温区,顺磁相中存在着铁磁团簇,铁磁相中也存在顺磁成分,即出现了磁相分离;少量的Na+离子替代(x=0.05)样品,反铁磁与铁磁相共存,低温下表现为自旋倾斜玻璃态特征,较高Na+离子替代样品的自旋倾斜玻璃态遭到破坏。体系磁电性质的变化来源于Na+离子替代引起的晶体晶格结构的变化、容忍因子t的变化和Mn3+/Mn4+离子比值的变化。     

柠檬酸盐溶胶—凝胶法合成Li1＋2xZn1—xPO4及其离子导电性

采用柠檬酸盐溶胶-凝胶法制备了组成为Li     

Electrical and CO-sensing properties of NdFe_(1–x)Co_xO_3 perovskite system

NdFe1–xCoxO3 (x=0.0–0.5) powders were prepared by a sol-gel citric method. X-ray diffraction was used to confirm the phase composition of the powders. All the samples are orthorhombic structure. The unit cell volume and grain size decreased with an increase of Co content x. The conduction type of the NdFe1–xCoxO3 perovskite oxides changed with the increasing Co content x. When x<0.3, the oxides showed p-type conduction behavior, and then changed to n-type when x>0.3. All the sensors presented higher respons...     

Magnetic Properties of La1-xSrxCoO3 (0≤x≤0.5)

The measurements of temperature dependence of the magnetic susceptibility of La1-xSrxCoO3 perovskite oxides at different Sr doping (0≤x≤0.5) and annealing temperature were presented. For the sample with x=0.1, a shoulder was observed around 150 K, and a peak which is one feature of spin glass appeared around 50 K in the curve of susceptibility versus temperature. The high-temperature(250～420 K)susceptibility fits well with Curie-Weiss law for all samples. Weiss constant and effective magnetic moment were determined and their variations with Sr doping and oxygen annealing condition were obtained. The Weiss constant increases monotonously with Sr content for x>0.2. The values of effective moments were interpreted with the spin state of cobalt ions. Studies on the susceptibilities of the samples with x=0.2 under different preparation temperatures and annealing temperatures show that the rising of sintering temperature and annealing temperature will increase the para-ferromagnetic transition temperature, and reduce the effective moment to normal value. Our result shows that both Co3 and Co4 ions should be in IS state after annealing and the oxygen annealing causes the transition of Co3 spin state from HS to IS.     

An auto-controlled study in in-vitro fertilization reveals the benefit of Percoll centrifugation to swim-up in the preparation of poor-quality semen

The efficiency of spermatozoa prepared by swim-up or by Percoll centrifugation was assessed in an in-vitro fertilization programme on 71 semen samples of a well-defined quality [total number of type A (WHO criteria) motile spermatozoa]: category I (n = 21) with > 100 x 10(6), II (n = 31) with 15-100 x 10(6), III (n = 11) with 5-15 x 10(6) and IV (n = 8) with < 5 x 10(6) type A motile spermatozoa. Oocytes were inseminated 4 h after oocyte retrieval, alternately with spermatozoa derived from swim-up and Percoll preparation. Both selection procedures resulted in a significantly higher (P < 0.001) percentage motility as compared to fresh semen. For low-quality samples (III and IV), however, swim-up was more effective in selecting highly motile (P = 0.004) and morphologically normal spermatozoa (P < 0.05). For high-quality samples, this difference might have been masked by introducing a swim-up step to remove Percoll particles. Regardless of the initial sperm quality, the mean fertilization rate was significantly higher (P = 0.003) when Percoll-treated spermatozoa were used for insemination (51.3 versus 37.8%). For semen of groups I and II, no difference in fertilization capacity was observed according to the sperm preparation method. Despite the lower percentage motility and normal morphology for the Percoll compared to the swim-up treatment in groups III and IV, fertilizing capacity was significantly (P < 0.001) in favour of this selection method (65.3 versus 26.5% in group III, 47.6 versus 11.6% in group IV).(ABSTRACT TRUNCATED AT 250 WORDS)     

Fabrication and Properties of （Y, Gd）BCO Superconductors

MelttexturingYBCObulksuperconductorexhibitsthecriticalcurrentdensity(Jc)exceeding 1× 10 4 A·cm 2at 77Kandhaspotentialforvariousengineeringappli cations .Recently ,itwasfoundthatREBa2 Cu3Oy(RE :lightrareearthelement)canexhibithigherJcvaluesun derrelativelyhighfieldsduetoasecondpeakthanthatofYBCO[1] .Anditiswidelyacceptedthatthesecondpeakoriginatesfromthepresenceoffield inducedpin ningbyRE rich(12 3)clusters[2 ,3] .MelttexturinggrowthofRE Ba Cu Odependsonthereducedoxygenatmo sphere ,…     

Yb3+，Er3+掺杂Y2Ti2O7荧光粉的制备与上转换发光机理研究

采用溶胶-凝胶法制备合成了(Y_0.98-xYb_xEr_0.02)₂Ti₂O₇(x=0, 0.02, 0.04...0.10)荧光粉, 分别采用XRD和荧光光谱仪对样品的结构和上转换发光性能进行了表征.研究了Yb3+掺杂浓度对样品上转换发光性能的影响, 并对样品的发光机理进行了研究.结果表明, 所得样品为面心立方结构的烧绿石相.在980nm激发下, 样品展现出很强的上转换荧光发射并且发光颜色可以通过Yb3+掺杂浓度来调节.样品上转换绿光和红光发射均为双光子过程并且交叉弛豫过程在上转换红光发射过程中占据主导作用.      

Minnesota Multiphasic Personality Inventory correlates of panic disorder with agoraphobia: changes with treatment

Granulocytes, monocytes, and T- and B-lymphocytes were separated from 28 blood samples collected from 5 bone marrow transplant (BMT) recipients. About 40% of granulocyte, monocyte, and B-lymphocyte samples were CMV DNA-positive by polymerase chain reaction in recipients with cytomegalovirus (CMV) infection. CMV DNA was rarely detected in separated T-lymphocytes. Within each of the simultaneously separated paired samples, there were several with single positive cell subtypes. Monocytes, granulocytes, and B-lymphocytes were the single positive samples in some instances. Thus, it is important to have all of the different cell subtypes present in samples for detection of CMV DNA in peripheral blood. We also studied the appearance of CMV DNA in plasma and peripheral blood leukocytes (PBLs) from 351 blood samples collected from 30 BMT recipients during a follow-up period of at least 3 months after BMT. All cell subtypes were represented in the PBL samples. In the 13 recipients who developed symptoms possibly associated with CMV infection or CMV disease, a correlation with the detection of CMV DNA in < or = 2 x 10(5) PBLs was found. In PBLs from 11 of the 13 BMT recipients, CMV DNA was detected before the onset of symptoms. CMV DNA was not detected in < or = 2 x 10(5) PBLs from recipients without CMV infection. The virus load in PBLs decreased during ganciclovir treatment. Nine of the 13 recipients displayed PCR-positive plasma samples, and CMV DNA was detected frequently after the onset of symptoms.     

Incidence of neoplasms in ages 0-19 y in parts of Sweden with high 137Cs fallout after the Chernobyl accident

An experiment was conducted to elucidate the origin of tetraploids (2n = 4x = 44) of Paragonimus westermani that occur together with diploid (2n = 2x = 22) and triploid (2n = 3x = 33) types in Liaoning Province, the People's Republic of China. Metacercariae of the diploid type, obtained from Hyogo Prefecture, Japan, and those of the triploid type from Tsushima, Nagasaki Prefecture, Japan, were mixed and inoculated into dogs and cats. The following results were obtained. The flukes were found in pairs within cysts in random combinations of 2x + 2x, 2x + 3x, and 3x + 3x (7:15:7). Oocytes in the oviduct were at stages from diplotene to metaphase. In a triploid fluke encysted with a diploid fluke, the primary oocytes were intruded by sperms from the diploid fluke. In the primary oocytes of diploid as well as triploid flukes, from diplotene to diakinesis, the homologues of the nucleolar chromosomes were heteromorphic as far as the size of the short arm was concerned. This implies that the triploid is an autotriploid generated in an ancestral diploid population that was polymorphic for the nucleolar chromosome.     

Vasopressin for the treatment of refractory hypotension after cardiopulmonary bypass

Fecal samples from 3 species of Onychomys (Rodentia: Muridae) captured in New Mexico and Arizona were examined for coccidia. Six of the 59 (10%) were infected with a new species of Eimeria. Sporulated oocysts (n = 105) of this new species are subspheroidal, 17.4 x 16.1 (14-21 x 13-19) microm, with ellipsoidal sporocysts 10.4 x 5.7 (9-12 x 5-8) microm. This species occurred in 3 of 24 (13%) Onychomys arenicola, 2 of 31 (6%) Onychomys leucogaster from New Mexico, and 1 of 4 (25%) Onychomys torridus from Arizona. Isolates recovered from O. leucogaster and O. torridus were inoculated into O. leucogaster (n = 5) and produced infections with a prepatent period of 7 days and a patent period of 7-23 days.     

Influence of Rare Earth Elements on Luminescent Properties of Y2SiO5:Tb

Photoluminescent(PL) and cathodoluminescent(CL) properties of rare earths (Sc3 , La3 , Gd3 and Lu3 ) doped (Y0.97Tb0.03)2SiO5 were studied. Rare earth doping clearly influences PL and CL properties of Y2SiO5:Tb. For La3 doped system, PL intensity increases nearly 10% at x=0.05 whereas for Lu3 doped system, the intensity increases about 20% at x=0.20. Gd3 doping and Sc3 doping reduce the intensity; at x=0.3, it is reduced about 30% for Gd3 doped system and about 15% for Sc3 doped system, respectively. Quenching concentration of activator became higher in rare earth doped samples, which may be understood by that the rare earth dopants might dilute the concentration of the activator. Additionally, doping also influences the color saturation of Y2SiO5:Tb. Sc3 , La3 , and Gd3 doping improve the color saturation, whereas Lu3 doping decreases the color saturation. CL measurements show that CL intensity increases for all rare earths doped systems. The energy transfer from Gd3 to Tb3 was discussed.