Third-order shear deformation beam model for flexural waves and free vibration of pipes.

A third-order shear deformation beam model is proposed to analyze dynamic behavior of straight hollow cylinders of annular cross-section, in which shear stress vanishes on the inner and outer surfaces of the pipe. Shear deformation, warping, and rotational inertia of cross-section are all considered, and the shear correction factor is not needed. A single governing differential equation is derived for analyzing flexural wave propagation and free vibration of straight pipe-beams. The phase and group speeds of flexural waves propagating in pipes are determined for acoustic and optical modes. The dispersion of flexural waves is analyzed. The frequency equations are obtained explicitly for pipe-beams with ten typical boundary conditions including clamped, pinned, guided, and free ends. The natural frequencies of clamped-free, clamped-clamped, and pinned-pinned pipe-beams are evaluated for the first four vibration modes. A comparison of this paper's numerical results of the natural frequencies with the previous ones is made and turns out the effectiveness of the suggested method. The influences of the pipe's thickness and length on the natural frequencies and mode shapes for a cantilever pipe are presented.

Trapped modes in an infinite or semi-infinite tube with a local enlargement.

Trapped modes in a hard cylindrical tube with a local axisymmetric enlargement or bulge and filled with a uniform acoustic medium is studied. The governing Helmholtz equation in the cylindrical coordinate system is employed to deal with this problem through the domain decomposition method and matching technique. The trapped modes and the corresponding frequencies less than the threshold frequency or cut-off frequency are derived. It is found that in addition to the fundamental mode, the second- and higher-order trapped modes exist and depend on the geometry parameters of the local bulge. The effects of the bulge radius and width on the frequencies are discussed. The local bulge leads to a decrease of the frequencies and the corresponding vibration mode is localized near the bulge. A multimodal analysis is made and frequency band gap of generalized trapped modes is also studied. A frequency band gap depends on the radius of a bulge and is independent of its width. The obtained results can be extended to analyze bound states in quantum wires.

[Expression of CD131 Gene in Acute Myeloid Leukemic Cells].

OBJECTIVE: To detect the expression level and the mutantion of CD131 in acute myeloid leukemic (AML) cells, and to analyze the relationship of CD131 expression level with clinical features. METHODS: The peripheral blood mononuclear cells (PBMNC) from 44 AML patients and 25 healthy donors were collected, and the expression level of CD131 mRNA was detected by RT-PCR. The full length coding sequence of CD131 from 15 patients and 5 healthy donors was amplified by RT-PCR, and linked to pGEM-T vector to clone TA, 10 positive recombinant clones of each sample were analyzed by DNA sequencing. The AML patients were divided into CD131 negative and CD131 positive groups according the expression level of CD131, and white blood cell counts, CD34(+) cells percentage, complete remission rate of patients were compared. RESULTS: CD131 was expressed at a lower level in AML than that in healthy donor. Five kinds of CD131 mutantions could be detected in both AML and healthy donor groups, but the mutation rate in AML (75.33%) was higher than that in healthy donors (18.0%). CD131 negative group showed a higher CD34(+) cells percentage (69.1% ± 20.8%), and lower complete remission rate (33.3%) than that in CD131 positive group (69.1% ± 20.8%, 33.3%). No statistically significant difference of WBC counts was found between 2 groups. CONCLUSION: CD131 is expressed at a low level and shows high frequency of mutation in acute myeloid leukemic cells. CD131 negative AML correlats with high proportion of CD34(+) cells, and showed insensitive to chemotherapy.

Resonance frequency and mass identification of zeptogram-scale nanosensor based on the nonlocal beam theory.

Free vibration and mass detection of carbon nanotube-based sensors are studied in this paper. Since the mechanical properties of carbon nanotubes possess a size effect, the nonlocal beam model is used to characterize flexural vibration of nanosensors carrying a concentrated nanoparticle, where the size effect is reflected by a nonlocal parameter. For nanocantilever or bridged sensor, frequency equations are derived when a nanoparticle is carried at the free end or the middle, respectively. Exact resonance frequencies are numerically determined for clamped-free, simply-supported, and clamped-clamped resonators. Alternative approximations of fundamental frequency are given in closed form within the relative error less than 0.4%, 0.6%, and 1.4% for cantilever, simply-supported, and bridged sensors, respectively. Mass identification formulae are derived in terms of the frequency shift. Identified masses via the present approach coincide with those using the molecular mechanics approach and reach as low as 10(-24)kg. The obtained results indicate that the nonlocal effect decreases the resonance frequency except for the fundamental frequency of nanocantilever sensor. These results are helpful to the design of micro/nanomechanical zeptogram-scale biosensor.

[microRNAs expression profile in acute promyelocytic leukemia cell differentiation induced by all-trans retinoic acid and arsenic trioxide].

OBJECTIVE: To study the expression profile of microRNAs in acute promyelocytic leukemia (APL) cells during differentiation. METHODS: Differentiation of APL cell line NB4 cells was induced by all-trans retinoic acid (ATRA) and arsenic trioxide (As2O3). Morphological and immunological assay was performed by Wright-Giemsa staining and flow-cytometric analysis of CD11b surface expression. During in vitro NB4 differentiation induced by ATRA and As2O3, microRNA expression profiles (miR-15b, miR-16, miR-34a, miR-107, miR-124a, miR-146, miR-155, miR-181a, miR-223, miR-342, let7c) were detected by real time RT-PCR, and the relative expression level of microRNAs were quantitatively analyzed by using 2(-ΔΔCt), and compared with that of control group. Meanwhile, the microRNA expression profiles were also detected in 15 newly diagnosed APL patients and 15 complete remission (CR) APL cases by real time RT-PCR, and the relative expression level of microRNA was quantitated by using 2(-ΔCt), and compared with that of control group (newly diagnosed APL as control group). These data were expressed as x(-) ± s, and differences between groups were examined using t test. P < 0.05 was considered statistically significant. RESULTS: The expression levels of miR-15b, miR-16, miR-107, miR-223 and miR-342 in NB4 differentiation group were obviously up-regulated (3.40, 4.22, 5.41, 20.03 and 5.29 folds higher in ATRA treated NB4 cells than that of control group respectively, and 3.62, 2.49, 2.58, 4.27 and 1.94 folds higher in AS2O3 treated NB4 cells than that of control group respectively), except for miR-15b, the expression levels of miR-16, miR-107, miR-223 and miR-342 in ATRA treated group was significantly higher than that in As2O3 treated group. The relative expression levels of miR-15b, miR-16, miR-107, miR-181a, miR-223 and miR-342 were 0.4137, 0.6367, 0.1260, 0.0522, 0.6611, 0.0280 in APL CR group, and 0.0751, 0.2022, 0.0425, 0.3064, 0.1733, 0.0090 in newly diagnosed APL group, respectively. The expression level of miR-15b, miR-16, miR-107, miR-223 and miR-342 in APL CR group were significantly upregulated compared with that of newly diagnosed APL groups (P < 0.05), while the expression level of miR-181a was significantly downregulated (P < 0.05). CONCLUSION: Specific expression of microRNA profiles is a key contributing factor in the differentiation of APL.

[Expression pattern of myeloid differentiation-related transcription factor mRNA in differentiation of NB4 and HL-60 cells induced by all-trans retinoic acid].

Hematopoiesis is coordinated by a complex regulatory network of transcription factors that involves proliferation, differentiation and maturation of a very small population of pluripotent hematopoietic stem cells with self-renewing and differentiating into various specialized and distinct blood cell types. Malfunction of transcription factors may lead to diseases such as acute myeloid leukemia (AML). The purpose of this study was to investigate the expression pattern of transcription factor mRNA in acute myeloid leukemia (AML) cells during in vitro differentiation. The 2 human leukemic cell lines HL-60 and NB4 had been used as model cell lines. Differentiation of HL-60 and NB4 cells was induced by all-trans retinoic acid (ATRA) for 4 days. Morphological changes were observed by May-Grunwald Giemsa stainings, the CD11b expression level was detected by flow cytometry. Transcription factor mRNA profiles (PU.1, C/EBPα, ε, γ, GATA-1, GATA-2) were determined by real time RT-PCR during in vitro HL-60 and NB4 differentiation; The expression level of transcription factor mRNA was relatively quantitatively analyzed by using 2(-ΔΔCT) and compared with control group. The results showed that the expression levels of PU.1 and C/EBP ε mRNA in NB4 differentiation group were 5.75 and 6.16, respectively, which were significantly higher than those in untreated group; while the expression level of C/EBPα, γ, GATA-1, GATA-2 mRNA in NB4 differentiation group were 62%, 31%, 63% and 8.7% respectively, which were significantly lower than those in untreated group; In HL-60 differentiation group, the expression levels of PU.1, C/EBPα, ε were 1.97, 1.95 and 2.35 respectively, which were significantly higher than those in untreated group; while the expression levels of C/EBPγ, GATA-1, GATA-2 in HL-60 differentiation group were 20%, 21% and 18% respectively, which were significantly lower than those in untreated group. It is concluded that dysregulation of transcription factors is a key contributing factor in the pathogenesis of acute myeloid leukemia.

[Packaging of lentivirus carrying gene hßc and overexpression of gene hßc in NB4 cells].

This study was aimed to overexpress gene hßc in NB4 cells via the method of lentivirus-mediated gene transfer, to observe the differentiation behaviour change of hßc over-expressing NB4 cells treated with IL-3 or GM-CSF, to explore the relationship between hßc gene and the differentiation behaviour of NB4 cells. The targeted hßc gene was amplified by PCR from the cloned vector carrying ORF of hßc. The PCR product containing PmeI and BstBI site introduced by primer was digested, and then cloned into lentivirus vector pRRLSIN.cPPT.PGK/IRES/GFP.WPRE to construct a lentiviral vector carrying hßc, named pLV-hßc. And the pLV-hßc plasmid was confirmed by restriction and sequencing. The recombinant lentivirus was produced by co-transfecting three plasmids into 293T packing cells. After transfection, the lentiviral supernatant was collected to transfect NB4 cells. GFP expression was examined by fluorescent microscope and the expression of hßc gene was detected by Western blot. Then, the NB4 cells over-expressing hßc were treated with IL-3 (10 ng/ml), GM-CSF (10 ng/ml), ATRA (1 µmol/L) respectively, and the CD11b expression, morphology and differentiation behaviour changes of every groups were observed by flow cytometry and microscopy, while NB4 cells transfected with blank lentivirus (NB4-blank cells) were used as controls. The results showed that the recombinant lentivirus vector carrying hßc gene could efficiently transfect NB4 cells and made NB4 cells to stably over-express hßc gene. The expression of CD11b was up-regulated in NB4-hßc cells treated with of IL-3 or GM-CSF, but it was not as obvious as the effect of ATRA, and no morphological change was observed in NB4 hßc cells treated with the IL-3 or GM-CSF. It is concluded that IL-3 or GM-CSF can induce NB4 cells over-expressing hßc to differentiate to neutrophils, but can not make them fully matured.

Interfacial waves in dissimilar piezoelectric cubic crystals with an imperfect bonding.

This paper studies propagation of shear waves along a weak interface of two dissimilar piezoelectric cubic crystals. Two piezoelectric cubic crystals are bonded along a specified cut direction. For an imperfect electrode interface, a dispersion relation of interfacial waves is derived explicitly. Numerical solutions are evaluated for several commonly-used piezoelectric cubic crystals. Our results show that interfacial imperfection alters the velocity of the interfacial shear waves. In particular, sometimes the interfacial shear waves may not exist for a perfect grounded interface and exist only for an imperfect electrode interface.

[Expression change of IL-3 receptor system in all-trans retinoic acid induced differentiation of NB4 cells].

Interleukin-3 receptor (IL-3R) is a heterodimeric membrane receptor. The α subunit is essential for ligand binding and confers ligand specificity to the receptor. The common beta chain (ßc) subunit, which is shared by the granulocyte macrophage-colony stimulating factor (GM-CSF), IL-3 and IL-5 receptors, is required for high-affinity ligand binding and signal transduction, mediating growth and survival of hematopoietic progenitor cells and the production and activation of mature hematopoietic cells. In order to investigate the role of IL-3 receptor system (IL-3Rα, GM-CSFRα and hßc) in myeloid differentiation, the expression level of IL-3 receptor system gene in all-trans retinoic acid (ATRA)-induced NB4 cell differentiation was detected by quantitative real time RT-PCR. At the same time, DNA sequence change was analyzed by cDNA sequencing. The results showed that the expression level of IL-3Rα mRNA was obviously down-regulated in NB4 cells treated with ATRA for 24 hours, but during differentiation of ATRA induced NB4 cells, the expression level of IL-3Rα mRNA was gradually restored, while the expression levels of GM-CSFRα mRNA and hßc mRNA were gradually up-regulated. The sequence of IL-3Rα and GM-CSFRα gene did not change before and after NB4 cells differentiation, but the sequence of hßc gene changed when NB4 cells were treated with ATRA, the expression of hßc mRNA sequence before NB4 cell differentiation taken truncated mutation as dominant, as regards expression of hßc mRNA sequence after NB4 cell differentiation, the truncated mutation of hßc mRNA had restored to wild type. It is concluded that the IL-3 receptor abnormality exists in NB4 cells, over expression of IL-3Rα and truncated mutation of hßc may be involved in proliferation and differentiation block in NB4 cells.