840 research outputs found
Capabilities' Substitutability and the "S" Curve of Export Diversity
Product diversity, which is highly important in economic systems, has been
highlighted by recent studies on international trade. We found an empirical
pattern, designated as the "S-shaped curve", that models the relationship
between economic size (logarithmic GDP) and export diversity (the number of
varieties of export products) on the detailed international trade data. As the
economic size of a country begins to increase, its export diversity initially
increases in an exponential manner, but overtime, this diversity growth slows
and eventually reaches an upper limit. The interdependence between size and
diversity takes the shape of an S-shaped curve that an be fitted by a logistic
equation. To explain this phenomenon, we introduce a new parameter called
"substitutability" into the list of capabilities or factors of products in the
tri-partite network model (i.e., the country-capability-product model) of
Hidalgo et al. As we observe, when the substitutability is zero, the model
returns to Hidalgo's original model but failed to reproduce the S-shaped curve.
However, in a plot of data, the data increasingly resembles an the S-shaped
curve as the substitutability expands. Therefore, the diversity ceiling effect
can be explained by the substitutability of different capabilities
Estimating the Proportion of True Null Hypotheses for Multiple Comparisons
Whole genome microarray investigations (e.g. differential expression, differential methylation, ChIP-Chip) provide opportunities to test millions of features in a genome. Traditional multiple comparison procedures such as familywise error rate (FWER) controlling procedures are too conservative. Although false discovery rate (FDR) procedures have been suggested as having greater power, the control itself is not exact and depends on the proportion of true null hypotheses. Because this proportion is unknown, it has to be accurately (small bias, small variance) estimated, preferably using a simple calculation that can be made accessible to the general scientific community. We propose an easy-to-implement method and make the R code available, for estimating the proportion of true null hypotheses. This estimate has relatively small bias and small variance as demonstrated by (simulated and real data) comparing it with four existing procedures. Although presented here in the context of microarrays, this estimate is applicable for many multiple comparison situations
LOW-TEMPERATURE SINTERED (ZnMg)2SiO4 MICROWAVE CERAMICS WITH TiO2 ADDITION AND CALCIUM BOROSILICATE GLASS
The low-temperature sintered (ZnMg)2SiOāTiO2 microwave ceramic using CaOāB2O3āSiO2 (CBS) as a sintering aid has been developed. Microwave properties of (Zn1-xMgx)2SiO4 base materials via sol-gel method were highly dependent on the Mg-substituted content. Further, effects of CBS and TiO2 additives on the crystal phases, microstructures and microwave characteristics of (ZnMg)2SiO4 (ZMS) ceramics were investigated. The results indicated that CBS glass could lower the firing temperature of ZMS dielectrics effectively from 1170 to 950Ā°C due to the liquid-phase effect, and significantly improve the sintering behavior and microwave properties of ZMS ceramics. Moreover, ZMSāTiO2 ceramics showed the biphasic structure and the abnormal grain growth was suppressed by the pinning effect of second phase TiO2. Proper amount of TiO2 could tune the large negative temperature coefficient of resonant frequency (tf) of ZMS system to a near zero value. (Zn0.8Mg0.2)2SiO4 codoped with 10 wt.% TiO2 and 3 wt.% CBS sintered at 950Ā°C exhibits the dense microstructure and excellent microwave properties: Īµr = 9.5, QĀ·f = 16 600 GHz and tf = ā9.6 ppm/Ā°C
Promotion of tumor development in prostate cancer by progerin
Progerin is a truncated form of lamin A. It is identified in patients with Hutchinson-Gilford progeria syndrome (HGPS), a disease characterized by accelerated aging. The contribution of progerin toward aging has been shown to be related to increased DNA damages. Since aging is one major risk factor for carcinogenesis, and genomic instability is a hallmark of malignant cancers, we investigated the expression of progerin in human cancer cells, and whether its expression contributes to carcinogenesis. Using RT-PCR and Western blotting, we detected the expression of progerin in prostate PC-3, DU145 and LNCaP cells at mRNA and protein levels. Ectopic progerin expression did not cause cellular senescence in PC-3 or MCF7 cells. PC-3 cells progerin transfectants were sensitized to DNA damage agent camptothecin (CPT); and persistent DNA damage responses were observed, which might be caused by progerin induced defective DNA damage repair. In addition, progerin transfectants were more tumorigenic in vivo than vector control cells. Our study for the first time describes the expression of progerin in a number of human cancer cell lines and its contributory role in tumorigenesis
Profiling Public Relations Practitionersā Work-Life Conflict: From A Diversity Lens
Work-life conflict -- defined as the incompatibility between expectations to perform one role
versus another -- can be categorized as time-based, strain-based, and behavior-based. Using a broad
diversity perspective, we examined understudied diversity categories as influencers of work-life
conflict, namely, age, family dependent care responsibility, and professional specialty. Surveying a
nationally representative sample of PRSA membership (N=820), we found that Generation Xers are
more stressed out than are other age groups; those who need to care for an older adult experience
significantly higher levels of time-based conflict; and employee relations specialists have to deal with
significantly more strain-based work-life conflict than do others
Do the Characteristics of Independent Directors and Supervisory Board Members Matter in China?
This paper investigates and compares the characteristics of independent directors and supervisory board members in Chinese listed firms. The occupational backgrounds of independent directors and supervisory board members in listed firms are very different. Besides, different firms have different preferences in employing independent directors and supervisory board members according to their demands. Moreover, the empirical results show that characteristics of independent directors and supervisory board members have no clear relationship with firm performance. No matter their professional backgrounds or age, the independent directors and supervisory board members do not have the authority to affect the decision making process of management. Thus they cannot really contribute to firm performance
Preparation of antibacterial microfibre
Three different kinds of antibacterial microfibres (270D, 300D and 330D) have been developed by adding 2-4 wt % nano silver masterbatch in the melt spinning process. The mechanical properties, silver content and morphology have been examined with tensile tester, inductively coupled plasma-optical emission spectrometer and scanning electron microscope respectively. Their antibacterial abilities are also studied with KS K 0693:2011. The results show that the added nano-particles have little influence on mechanical properties of antibacterial microfibres and their max strain and tenacity are similar to that of common manmade fibre. The fineness of the 270D, 300D and 330D samples are found to be 0.23, 0.26 and 0.30 den, and the corresponding added silver contents are 265.5, 231 and 259 ppm respectively. It is also observed that all samples bacteriostatic reduction rates are about 99.9% for both Staphylococcus aureus and Klebsiella pneumonia before washing. But after washing, it drops to 65.4%/75%, 91.9%/97.7% and 94.8%/99.9% respectively for both the bacteria in case of 270D, 300D and 330D samples. It is concluded that 300D and 330D microfibre samples have good antibacterial ability before and after washing
Improved Statistical Analysis for Array CGH-Based DNA Copy Number Aberrations
Array-based comparative genomic hybridization (aCGH) allows measuring DNA copy number at the whole genome scale. In cancer studies, one may be interested in identifying DNA copy number aberrations (CNAs) associated with certain clinicopathological characteristics such as cancer metastasis. We proposed to define test regions based on copy number pattern profiles across multiple samples, using either smoothed log2-ratio or discrete data of copy number gain/loss calls. Association test performed on the refined test regions instead of the probes has improved power due to reduced number of tests. We also compared three types of measurement of copy number levels, normalized log2-ratio, smoothed log2-ratio, and copy number gain or loss calls in statistical hypothesis testing. The relative strengths and weaknesses of the proposed method were demonstrated using both simulation studies and real data analysis of a liver cancer study
Rethinking the Detection Head Configuration for Traffic Object Detection
Multi-scale detection plays an important role in object detection models.
However, researchers usually feel blank on how to reasonably configure
detection heads combining multi-scale features at different input resolutions.
We find that there are different matching relationships between the object
distribution and the detection head at different input resolutions. Based on
the instructive findings, we propose a lightweight traffic object detection
network based on matching between detection head and object distribution,
termed as MHD-Net. It consists of three main parts. The first is the detection
head and object distribution matching strategy, which guides the rational
configuration of detection head, so as to leverage multi-scale features to
effectively detect objects at vastly different scales. The second is the
cross-scale detection head configuration guideline, which instructs to replace
multiple detection heads with only two detection heads possessing of rich
feature representations to achieve an excellent balance between detection
accuracy, model parameters, FLOPs and detection speed. The third is the
receptive field enlargement method, which combines the dilated convolution
module with shallow features of backbone to further improve the detection
accuracy at the cost of increasing model parameters very slightly. The proposed
model achieves more competitive performance than other models on BDD100K
dataset and our proposed ETFOD-v2 dataset. The code will be available.Comment: 26 pages, 4 figures, 7 table
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