JFET integration using a foundry SOI photonics platform

We explore the monolithic integration of conventional electronics with SOI photonics using the commercial silicon photonics foundry technology offered by A*STAR's Institute of Microelectronics (IME). This process offers optical waveguide modulators and photodetectors, but was not intended to support transistors. We present the implementation of junction field effect transistors (JFETs) integrated with optical waveguides and photodetectors. A simple SPICE model is developed for the JFETs based on the available ion implant parameters, and the geometry feature size allowed by the technology's layout rules. We have demonstrated the monolithic integration of photonics and electronics circuits. This work could be useful for application in waveguide sensors and optical telecommunications

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Monolithic integration of SOI waveguide photodetectors and transimpedance amplifiers

In the absence of commercial foundry technologies offering silicon-on-insulator (SOI) photonics combined with Complementary Metal Oxide Semiconductor (CMOS) transistors, monolithic integration of conventional electronics with SOI photonics is difficult. Here we explore the implementation of lateral bipolar junction transistors (LBJTs) and Junction Field Effect Transistors (JFETs) in a commercial SOI photonics technology lacking MOS devices but offering a variety of n- and p-type ion implants intended to provide waveguide modulators and photodetectors. The fabrication makes use of the commercial Institute of Microelectronics (IME) SOI photonics technology. Based on knowledge of device doping and geometry, simple compact LBJT and JFET device models are developed. These models are then used to design basic transimpedance amplifiers integrated with optical waveguides. The devices' experimental current-voltage characteristics results are reported

CALORIMETRIC STUDY FOR HYDRAZINE NITRATE

By using a precision automatic adiabatic calorimeter the heat capacity of hydra zine nitrate in the temperature range of 220-370 K have been measured. The heat of fusion, melting point and entropy of fusion for the sample have been obtained from the results of heat capeity measurements. The precision of heat capacity measurements for hydrazine nitrate is +/- 0.2%, as shown by the root mean-square (r.m.s) of the percentage deviation, and the relative error for beat of fusion measurement is 0.1%. In order to verify the reliability for all of these measurements we have determined the heat capacity, heat of fusion as well as the melting point of pure ice with the same apparatus and the results were found to be in agreement with the data in literature. Then, the heat of fusion and melting point of hydrazine nitrate have been. measured with the SETARAM high temperature calorimeter. The results obtained by the two apparatuses coincided with each other. Besides, the purity derived from the heat capacity measurements of the sample is in agreement with the results from chemical analysis. The facts show that the data from calorimetric measurements for hydrazine nitrate are reliable

Pd Schottky barrier photodetector integrated with LOCOS-defined SOI waveguides

Palladium on n-type silicon Schottky barrier photodetectors have been integrated with SOI optical waveguides. The diodes gave optical responsivity of 330 nA/mW at 1310 nm. Dark current density is less than 2×10-8 Acm-2 at 1 volt reverse bias

Optical and electrical performance of Schottky diodes on low loss SOI waveguides

Thin layers of nickel (Ni) and palladium (Pd) are used to form Schottky barrier photodiodes on silicon–on–insulator optical rib waveguides defined by the local oxidation of silicon technique. Optical loss and attenuation due to the metallic layers on the waveguides are estimated by simulations followed by experimental verification. Loss increases with increasing metal thickness until a plateau is reached at a thickness of approximately 50 nm. Higher optical loss is observed for the transverse magnetic mode compared to that for the transverse electric mode. The dark current density of all the devices is less than 10−6Acm−2 at 1 V reverse bias. The TM mode responsivity is 4.7 mA/W and 0.33 mA/W for 0.5 mm long Ni/nSi and Pd/nSi at 1310 nm wavelength, respectively. This work demonstrates great potential for simple sub-bandgap photodetectors for silicon photonics

Relationships between Maternal Gene Polymorphisms in One Carbon Metabolism and Adverse Pregnancy Outcomes: A Prospective Mother and Child Cohort Study in China

Background: To investigate relationships between five single nucleotide polymorphisms (SNP) in four maternal genes involved in one carbon metabolism and adverse pregnancy outcomes, including preterm birth (PTB), low birth weight (LBW), and small-for-gestational-age (SGA). Methods: This was a prospective mother and child cohort study in Wuqiang, China. Pregnant women (n = 939) were recruited from Jun 2016 to Oct 2018. Pregnancy outcomes (PTB, LBW, and SGA) were extracted from medical records and other information including age at childbearing, maternal education level, gravidity, parity, pre-pregnancy weight and height was collected by using a structured questionnaire. The maternal serum folate concentration was measured by using Abbott Architect i2000SR chemiluminescence analyzer in the first prenatal care visit. DNA genotyping of methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C, methionine synthase reductase (MTRR) A66G, methionine synthase (MTR) A2756G, and thymidylate synthetase (TYMS) rs3819102 was processed by Sequenom MassARRAY iPLEX Platform. Univariate and multivariate logistics regression analysis were used to test the relationships between 5 SNPs and PTB, LBW, SGA. Results: Totally, 849 dyads of women and infants were included in the analysis. The prevalence of PTD, LBW, and SGA were 3.76%, 1.58%, and 5.31% respectively. The homozygote frequencies of MTHFR C677T, MTHFR A1298C, MTRR A66G, MTR A2756G, and TYMS rs3819102 were 44.2%, 1.4%, 6.7%, 1.3%, and 3.2%, and the alt allele frequencies were 66.1%, 10.8%, 24.9%, 10.5%, and 20.5% respectively. The average serum folate concentration was 11.95 ng/mL and the folate deficiency rate was 0.47%. There were no significant associations between MTHFR C677T, MTHFR A1298C, MTRR A66G, MTR A2756G, TYMS rs3819102 alleles and PTD, LBW, SGA (p > 0.05). Conclusions: In the population with adequate folate status and low prevalence of adverse pregnancy outcomes, MTHFR C677T, MTHFR A1298C, MTRR A66G, MTR A2756G, TYMS rs3819102 alleles may not be related to PTD, LBW, and SGA

Nitrogen fertilizer is a key factor effecting the soil chemical and microbial communities in a Mollisol

Microbial communities drive geochemical cycles in soils. Relatively few studies have assessed the long-term impacts of different types of soil amendments under field conditions in long-term experiments. The response of soil microbial organisms in a Mollisol cultivated with maize for 35 years was examined. Treatments involved the use of N, P and K fertilizers and two doses of straw residue incorporation, in isolation and combined Real-time PCR and Illumina Miseq sequencing methods were used to characterize the microbial community. The results showed that addition of nitrogen fertilizers decreased soil pH, but this was mitigated when a high dose of straw was also incorporated. Long-term application of inorganic fertilizers was able to alter the abundance of functional soil microbial population. Application of inorganic N fertilizer resulted in distinctive changes on N-cycle microorganisms. Phosphate-solubilizing functional genes abundance was lower in plots with no phosphate fertilizer. Sequencing analysis showed that the presence or absence of N in the fertilizer mix is a key factor affecting bacterial community diversity of agricultural soil, pH TOC and TN showed a high correlation with bacterial community composition. Nitrogen addition increased the N concentration in the soil which could cause changes in the soil pH and changed the soil bacterial community. Our findings proved that interaction of N fertilizer with other fertilizers can affect microbial communities.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author