Variants of chromosome 9 in phenotypically normal individuals

The human chromosome 9 displays the highest degree of structural variability. Four different types of variants are described including pericentric inversion, extra G-positive band in the q arm, additional G-positive band in the p arm and duplication of band 9q21-q22. It is important to demonstrate inheritance from a phenotypically normal individual in order to differentiate between a variant chromosome and an abnormal chromosome.     

Improved strained HEMT characteristics using double-heterojunctionIn0.65Ga0.35As/In0.52Al0.48As design

The DC and microwave properties of strained In_0.65Ga _0.35As/In₀₅₂Al_0.48As HEMTs (high electron-mobility transistors) with double-heterojunction design are presented. The high sheet carrier density and good carrier confinement give rise to excellent device performance with very low output conductance. For 1×150-μm² long-gate HEMTs, the measured cutoff frequency f_T and maximum frequency of oscillation f_max are as high as 37 and 66 GHz, respectively     

Determination of alpha-particle track depths in CR-39 detector from their cross-sections and replica heights

A challenging task in the application of solid-state nuclear track detectors (SSNTDs) is the measurement of depths of the tracks. One approach involves breaking and polishing the side of SSNTDs to reveal the cross-sections of the tracks for direct measurements. Recently, surface profilometry was used to measure the heights of the replicas of alpha-particle tracks to give the track depths. In the present work, systematic comparisons among the track depths for alpha-particles with normal incidence and different incident energies were made for these two methods. After irradiation, the detectors were etched in a 6.25 N aqueous solution of NaOH at 70 °C. Both long etching time of 15 h (to produce spherical-phase tracks) and short etching time from 1 to 8 h (to produce sharp-phase tracks) were used. Good agreement was achieved between the two methods for spherical-phase tracks but not for sharp-phase tracks. It has been found that the surface profilometry method only works for replicas for spherical-phase tracks. Replicas for sharp-phase tracks are easier to collapse or deform, so the surface profilometry method may not give correct results.     

Optical appearance of alpha particle tracks in CR-39 SSNTD

A ray tracing method based on geometrical optics was used to study the tracks from alpha particles with different energies and with an incident angle of 50°. The transmission operation mode of the microscope is simulated. Considering the distribution of light intensities from the tracks, the mean and the 80% percentile gray levels from real experiments are proposed as quantitative variables to differentiate among tracks. The gray level properties for the same track for different exposures can vary to large extents. We introduce three variables, κ, λ and ε, to make empirical corrections. It is interesting to see that these coefficients are very consistent for the same alpha particle track despite the very different gray level properties. Gray level results have been obtained for tracks from alpha particles with 50° incident angle and different incident energies. However, the track depths cannot be predicted by any one of the coefficients κ, λ and ε. Multivariate analyses can help separate the tracks corresponding to different alpha energies. By using discriminant analysis with κ, λ and ε as independents, effectively all alpha energies can be determined with an accuracy of ±0.5 MeV.     

795 nm and 1064 nm dual pump thulium-doped tellurite fibre for S-band amplification

Gain measurement in thulium-doped tellurite fibre is demonstrated with a maximum internal gain of 7 dB at 1480 nm. An improvement in gain by a factor of 2 is achieved using a 795 nm and 1064 nm dual pump scheme. Gain in tellurite fibres extends to longer wavelength than in fluorides, showing improved overlap with the C-band EDFA.     

Parallel Computation of High-Dimensional Robust Correlation and Covariance Matrices

The computation of covariance and correlation matrices are critical to many data mining applications and processes. Unfortunately the classical covariance and correlation matrices are very sensitive to outliers. Robust methods, such as Quadrant Correlation (QC) and the Maronna method, have been proposed. However, existing algorithms for QC only give acceptable performance when the dimensionality of the matrix is in the hundreds; and the Maronna method is rarely used in practice because of its high computational cost. In this paper we develop parallel algorithms for both QC and the Maronna method. We evaluate these parallel algorithms using a real data set of the gene expression of over 6000 genes, giving rise to a matrix of over 18 million entries. In our experimental evaluation, we explore scalability in dimensionality and in the number of processors, and the trade-offs between accuracy and computational efficiency. We also compare the parallel behaviours of the two methods. From a statistical standpoint, the Maronna method is more robust than QC. From a computational standpoint, while QC requires less computation, interestingly the Maronna method is much more parallelizable than QC. After a thorough experimentation, we conclude that for many data mining applications, both QC and Maronna are viable options. Less robust, but faster, QC is the recommended choice for small parallel platforms. On the other hand, the Maronna method is the recommended choice when a high degree of robustness is required, or when the parallel platform features a large number of processors (e.g., 32).     

Double blind, randomised, placebo controlled study of oral vancomycin in prevention of necrotising enterocolitis in preterm, very low birthweight infants

AIMS: To evaluate the effectiveness of oral vancomycin in the prophylaxis of necrotising enterocolitis in preterm, very low birthweight infants. METHODS: A prospective, double blind, randomised, placebo controlled study in a tertiary referral centre of a university teaching hospital was conducted on 140 very low birthweight infants consecutively admitted to the neonatal unit. The babies were randomly allocated to receive oral vancomycin (15 mg/kg every 8 hours for 7 days) or an equivalent volume of placebo solution. Prophylaxis was started 24 hours before the start of oral feeds. All suspected cases of necrotising enterocolitis were investigated with a full sepsis screen and serial abdominal radiographs. Necrotising enterocolitis was diagnosed and staged according to modified Bell's criteria. RESULTS: Nine of 71 infants receiving oral vancomycin and 19 of 69 infants receiving the placebo solution developed necrotising enterocolitis (p = 0.035). Infants with necrotising enterocolitis were associated with a significant increase in mortality (p = 0.026) and longer duration of hospital stay (p = 0.002). CONCLUSIONS: Prophylactic oral vancomycin conferred protection against necrotising enterocolitis in preterm, very low birthweight infants and was associated with a 50% reduction in the incidence. However, widespread implementation of this preventive measure is not recommended, as it would only be effective in necrotising enterocolitis caused by Gram positive organisms and could increase the danger of the emergence of vancomycin resistant or dependent organisms. Its use should be restricted to a high prevalence nursery for a short and well defined period in a selected group of high risk patients.     

Cytosolic and nuclear distribution of PPARgamma2 in differentiating 3T3-L1 preadipocytes

In light of the pivotal role that PPARgamma2 plays in the expression of fat specific genes (e.g., A-FABP), we have examined the hypothesis that a rise in PPARgamma2 protein is required for the expression of A-FABP, and that the acceleration of fat cell differentiation by the thiazolidinedione agent, pioglitazone (PIOG), reflects an increase in the abundance of PPARgamma2 mRNA and protein. Western analyses surprisingly revealed that undifferentiated 3T3-L1 fibroblasts contained significant levels of PPARgamma2 protein; that the amount of total cellular PPARgamma2 only increased 2-fold during differentiation; and that the levels of PPARgamma2 protein and mRNA were not increased by PIOG even though fat cell differentiation was accelerated by PIOG as revealed by a 20-fold increase in A-FABP expression. Cell fractionation studies revealed that PPARgamma2 was evenly distributed between the cytosolic and nuclear compartments in both undifferentiated and differentiating 3T3-L1 cells. Immunocytochemical studies with a PPARgamma2-specific antibody indicated that PPARgamma2 was diffusely distributed throughout the cytosol of undifferentiated 3T3-L1 cells, but as the differentiation progressed, the PPARgamma2 became focused around the developing lipid droplets. In contrast to PPARgamma2, undifferentiated 3T3-L1 cells contained no measurable quantities of RXRalpha, but once fat cell differentiation was initiated by treatment with IBMX and dexamethasone, the cellular content of RXRalpha increased several fold. The rise in RXRalpha content paralleled the induction of A-FABP, but the expression of RXRalpha was not enhanced by PIOG. Although the amount of PPARgamma2 and RXRalpha was unaffected by PIOG, gel shift assays revealed that PIOG stimulated PPARgamma2/RXRalpha binding to the adipose response element of A-FABP by 5-fold in less than 12 h. Apparently, RXRalpha rather than PPARgamma2 is the pivotal trans-factor essential for the initiation of terminal fat cell differentiation. However, the high cytsolic content of PPARgamma2 and its association with the lipid droplet of differentiating 3T3-L1 cells suggests PPARgamma2 may possess a cytosolic function in the developing fat cell.     

Severe progressive deformities after limb lengthening in type-II fibular hemimelia

Until recently the accepted treatment of choice for severe type-II fibular hemimelia has been Syme's or Boyd's amputation. The alternative of distraction lengthening using the Ilizarov technique is now available. We report three patients (four limbs) with type-II fibular hemimelia who were treated by the Ilizarov technique and followed up for two to six years. Severe progressive procurvatum and valgus deformity of the tibia and valgus deformity and lateral subluxation of the ankle were found in all four limbs. Multiple additional soft-tissue and bony surgery was necessary. In view of these problems we feel that reappraisal of the indications for lengthening in type-II fibular hemimelia is necessary.     

微波辐射对细胞膜通透性的影响

本实验通过电镜镧细胞化学方法，观察了微波辐射对生物样品细胞膜通透性的影响。在常规化学固定的情况下，镧颗粒沿细胞间隙密集分布而不能进入细胞内。生物样品经微波辐射后，在细胞内甚至在线粒体等细胞器内可观察到较多的镧颗粒。提示：微波辐射使生物膜的通透性发生了改变。