AlGaN/GaN high electron mobility transistor heterostructures grown by ammonia and combined plasma-assisted ammonia molecular beam epitaxy

The structural properties and surface morphology of AlN epitaxial layers grown by ammonia (NH3) and plasma-assisted (PA) molecular beam epitaxy (MBE) at different growth conditions on (0001) sapphire were investigated. The lowest RMS roughness of ~0.7 nm was achieved for the sample grown by NH3 MBE at a substrate temperature of 1085 °C and NH3 flow of 100 standard cm3 min−1. Atomic force microscopy measurements demonstrated a terrace-monolayer step-like surface morphology. Furthermore, the optimal substrate temperature for growth of GaN and AlGaN layers was determined from analysis of the GaN thermal decomposition rate. Using the optimized growth conditions, high electron mobility transistor heterostructures were grown by NH3 MBE on different types of AlN nucleation layer deposited by NH3 MBE or PA MBE. The grown heterostructures demonstrated comparable two-dimensional electron gas (2DEG) properties. The maximum 2DEG mobility of ~2000 cm2 V–1 s–1) at a 2DEG density of ~1.17 × 1013 cm−2 was achieved for the heterostructure with a PA MBE-grown AlN nucleation layer. The obtained results demonstrate the possibility of successful combination of different epitaxial approaches within a single growth process, which will contribute to the development of a new type of hybrid epitaxy that exploits the advantages of several technologies

Ultraviolet stimulated emission in AlGaN layers grown on sapphire substrates using ammonia and plasma-assisted molecular beam epitaxy

Ammonia and plasma‐assisted (PA) molecular beam epitaxy modes are used to grow AlN and AlGaN epitaxial layers on sapphire substrates. It is determined that the increase of thickness of AlN buffer layer grown by ammonia‐MBE from 0.32 μm to 1.25 μm results in the narrowing of 101 X‐Ray rocking curves whereas no clear effect on 002 X‐Ray rocking curve width is observed. It is shown that strong GaN decomposition during growth by ammonia‐MBE causes AlGaN surface roughening and compositional inhomogeneity, which leads to deterioration of its lasing properties. AlGaN layers grown by ammonia‐MBE at optimized temperature demonstrate stimulated emission (SE) peaked at λ = 330 nm, 323 nm, 303 nm and 297 nm with the SE threshold values of 0.7 MW cm−2, 1.1 MW cm−2, 1.4 MW cm−2 and 1.4 MW cm−2, respectively. In comparison to these, AlGaN layer grown using PA‐MBE pulsed modes (migration‐enhanced epitaxy, metal‐modulated epitaxy, and droplet elimination by thermal annealing) shows a SE with a relatively low threshold (0.8 MW cm−2) at the considerably shorter wavelength of λ = 267 nm

Insights into corn genes derived from large-scale cDNA sequencing

We present a large portion of the transcriptome of Zea mays, including ESTs representing 484,032 cDNA clones from 53 libraries and 36,565 fully sequenced cDNA clones, out of which 31,552 clones are non-redundant. These and other previously sequenced transcripts have been aligned with available genome sequences and have provided new insights into the characteristics of gene structures and promoters within this major crop species. We found that although the average number of introns per gene is about the same in corn and Arabidopsis, corn genes have more alternatively spliced isoforms. Examination of the nucleotide composition of coding regions reveals that corn genes, as well as genes of other Poaceae (Grass family), can be divided into two classes according to the GC content at the third position in the amino acid encoding codons. Many of the transcripts that have lower GC content at the third position have dicot homologs but the high GC content transcripts tend to be more specific to the grasses. The high GC content class is also enriched with intronless genes. Together this suggests that an identifiable class of genes in plants is associated with the Poaceae divergence. Furthermore, because many of these genes appear to be derived from ancestral genes that do not contain introns, this evolutionary divergence may be the result of horizontal gene transfer from species not only with different codon usage but possibly that did not have introns, perhaps outside of the plant kingdom. By comparing the cDNAs described herein with the non-redundant set of corn mRNAs in GenBank, we estimate that there are about 50,000 different protein coding genes in Zea. All of the sequence data from this study have been submitted to DDBJ/GenBank/EMBL under accession numbers EU940701–EU977132 (FLI cDNA) and FK944382-FL482108 (EST)

"Feed from the Service": Corruption and Coercion in the State-University Relations in Central Eurasia

Education in Central Eurasia has become one of the industries, most affected by corruption. Corruption in academia, including bribery, extortions, embezzlement, nepotism, fraud, cheating, and plagiarism, is reflected in the region’s media and addressed in few scholarly works. This paper considers corruption in higher education as a product of interrelations between the government and academia. A substantial block of literature considers excessive corruption as an indicator of a weak state. In contrast to standard interpretations, this paper argues that in non-democratic societies corruption is used on a systematic basis as a mechanism of direct and indirect administrative control over higher education institutions. Informal approval of corrupt activities in exchange for loyalty and compliance with the regime may be used in the countries of Central Eurasia for the purposes of political indoctrination. This paper presents the concept of corruption and coercion in the state-university relations in Central Eurasia and outlines the model which incorporates this concept and the “feed from the service” approach. It presents implications of this model for the state-university relations and the national educational systems in Central Eurasia in general and offers some suggestions on curbing corruption

Research and Design of a Routing Protocol in Large-Scale Wireless Sensor Networks

无线传感器网络，作为全球未来十大技术之一，集成了传感器技术、嵌入式计算技术、分布式信息处理和自组织网技术，可实时感知、采集、处理、传输网络分布区域内的各种信息数据，在军事国防、生物医疗、环境监测、抢险救灾、防恐反恐、危险区域远程控制等领域具有十分广阔的应用前景。 本文研究分析了无线传感器网络的已有路由协议，并针对大规模的无线传感器网络设计了一种树状路由协议，它根据节点地址信息来形成路由，从而简化了复杂繁冗的路由表查找和维护，节省了不必要的开销，提高了路由效率，实现了快速有效的数据传输。 为支持此路由协议本文提出了一种自适应动态地址分配算——ADAR（AdaptiveDynamicAddre...As one of the ten high technologies in the future, wireless sensor network, which is the integration of micro-sensors, embedded computing, modern network and Ad Hoc technologies, can apperceive, collect, process and transmit various information data within the region. It can be used in military defense, biomedical, environmental monitoring, disaster relief, counter-terrorism, remote control of haz...学位：工学硕士院系专业：信息科学与技术学院通信工程系_通信与信息系统学号：2332007115216

Mechanism Of Nitric Oxide Oxidation Reaction (2No + O2 → 2No2) Revisited

The reaction between molecular oxygen and two nitric oxide(II) molecules is studied with high-level ab initio wave function methods, including geometry optimizations with coupled cluster (CCSD(T,full)/cc-pCVTZ) and complete active space with second order perturbation theory levels (CASPT2/cc-pVDZ). The energy at the critical points was refined by calculations at the CCSD(T,full)/aug-cc- pCVTZ level. The controversies found in the previous theoretical studies are critically discussed and resolved. The best estimate of the activation energy is 6.47 kJ/mol. © 2011 American Chemical Society

Polypeptide-Based Molecular Platform and Its Docetaxel/Sulfo-Cy5-Containing Conjugate for Targeted Delivery to Prostate Specific Membrane Antigen

A strategy for stereoselective synthesis of molecular platform for targeted delivery of bimodal therapeutic or theranostic agents to the prostate-specific membrane antigen (PSMA) receptor was developed. The proposed platform contains a urea-based, PSMA-targeting Glu-Urea-Lys (EuK) fragment as a vector moiety and tripeptide linker with terminal amide and azide groups for subsequent addition of two different therapeutic and diagnostic agents. The optimal method for this molecular platform synthesis includes (a) solid-phase assembly of the polypeptide linker, (b) coupling of this linker with the vector fragment, (c) attachment of 3-aminopropylazide, and (d) amide and carboxylic groups deprotection. A bimodal theranostic conjugate of the proposed platform with a cytostatic drug (docetaxel) and a fluorescent label (Sulfo-Cy5) was synthesized to demonstrate its possible sequential conjugation with different functional molecules