Algebraic and multiple integral identities

In this paper we develop some identities involving symmetric products in an abstract algebra which was formerly introduced by Rimark Ree to investigate the shuffle product and relations with skew symmetric (Lie) products. His motivation was partially the characterization of homogeneous Lie polynomials in noncommuting variables, while our motivation is derived from problems in systems theory. The main link in these applications is the need for identities involving multiple integrals of functions of many variables. The relation between these identities and some of the abstract identities developed here is also worked out and some of the applications to systems theory reviewed.     

Conductance peak splitting in charge polarized coupled quantum dots

We report a measurement of linear conductance through a series double dot as a function of the total double dot charge and the charge difference for interdot tunnel conductances between zero and one mode. The dots are defined by ten independently tunable electrostatic gates on the surface of a GaAs/AlGaAs heterostructure to allow separate adjustment of dot charge and interdot conductance. For weak interdot tunneling the measured double dot conductance agrees with a transport model in which each dot is individually governed by Coulomb blockade theory. As interdot tunnel conductance increases toward one mode, the measured conductance peak positions and shapes indicate both a relaxation of the charge quantization condition for individual dots and quantum mechanical charge sharing between dots. The results are in quantitative agreement with many body charge fluctuation theory.     

CBE growth of GaAs/GaAlAs HBTs using the new DEAlH-NMe3 precursor and all-gaseous dopants

This paper describes the first reported use of diethylaluminium hydride-trimethylamine adduct (DEAlH-NMe₃) for the growth of GaAs/GaAlAs power heterojunction bipolar transistors (HBTs) by chemical beam epitaxy (CBE). This precursor possesses a significantly higher vapour pressure than the more conventionally used triethylaluminium (TEA), and leads to much less stringent requirements for bubbler and gas-line heating, and also much-improved GaAs/GaAlAs heterojunction definition when no carrier gas is employed. The use of all-gaseous n- and p-type dopants offers significant technological advantages in CBE, and the current paper also provides the first report of the use of hydrogen sulphide for n-type doping of CBE-grown GaAlAs HBT emitter regions. In conclusion, DC and RF data obtained from the heterojunction bipolar transistors fabricated to date are described. A DC gain of 40 has already been measured and encouraging early data obtained from RF-probed devices are also presented.     

Flame temperature determination by dual laser ionization

A dual laser ionization (DLI) apparatus was used to determine ionic diffusion and mobility coefficients for sodium and lithium in a stoichiometric H₂/O₂/Ar flame. The flame temperature was calculated using the Einstein relation. The sodium and lithium DLI temperature estimates are in agreement with each other and with temperatures measured by the line-reversal technique in similar flames.     

An integrated mass spectrometry imaging and digital pathology workflow for objective detection of colorectal tumours by unique atomic signatures

Tumours are abnormal growths of cells that reproduce by redirecting essential nutrients and resources from surrounding tissue. Changes to cell metabolism that trigger the growth of tumours are reflected in subtle differences between the chemical composition of healthy and malignant cells. We used LA-ICP-MS imaging to investigate whether these chemical differences can be used to spatially identify tumours and support detection of primary colorectal tumours in anatomical pathology. First, we generated quantitative LA-ICP-MS images of three colorectal surgical resections with case-matched normal intestinal wall tissue and used this data in a Monte Carlo optimisation experiment to develop an algorithm that can classify pixels as tumour positive or negative. Blinded testing and interrogation of LA-ICP-MS images with micrographs of haematoxylin and eosin stained and Ki67 immunolabelled sections revealed Monte Carlo optimisation accurately identified primary tumour cells, as well as returning false positive pixels in areas of high cell proliferation. We analysed an additional 11 surgical resections of primary colorectal tumours and re-developed our image processing method to include a random forest regression machine learning model to correctly identify heterogenous tumours and exclude false positive pixels in images of non-malignant tissue. Our final model used over 1.6 billion calculations to correctly discern healthy cells from various types and stages of invasive colorectal tumours. The imaging mass spectrometry and data analysis methods described, developed in partnership with clinical cancer researchers, have the potential to further support cancer detection as part of a comprehensive digital pathology approach to cancer care through validation of a new chemical biomarker of tumour cells.

Digital pathology and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) imaging reveals a unique elemental signature of colorectal cancer.     

Chemical composition, antimicrobial, antiradical and anticholinesterase activity of the essential oil of Pulicaria stephanocarpa from Soqotra

The chemical composition of the hydrodistilled leaf essential oil from Pulicaria stephanocarpa Balf. Fil was determined by GC-MS analysis, and its antimicrobial, antioxidant and anticholinesterase (AChE) activities were evaluated. Eighty-three compounds were identified representing 97.2% of the total oil. (E)-Caryophyllene 13.4%, (E)-nerolidol 8.5%, caryophyllene oxide 8.5%, alpha-cadinol 8.2% spathulenol 6.8% and tau-cadinol 4.7%, were the main components. Antimicrobial activity of the oil, evaluated using the disc diffusion and broth dilution methods, demonstrated the highest susceptibility on Gram-positive bacteria and Candida albicans. The free radical scavenging ability of the oil was assessed by the DPPH assay to show antiradical activity with IC50 of 330 microg/mL. Moreover, the oil revealed an AChE inhibitory activity of 47% at a concentration of 200 microg/mL using Ellman's method.     

利用对称位移脉冲改善分辨率-IMPRESS HMBC

众所周知异核二维实验在中、小分子的结构确定中非常重要. 例如¹H与¹³C/¹⁵N异核远程相关无疑是连接分子中孤立结构碎片及季碳的最有利的工具. 然而，在间接检测的异核二维实验中，间接检测域-异核维的太低分辨率一直是困扰着化学家的主要问题. 过去在有限的采样时间内提高分辨率的方法主要有线性预测、带选择脉冲和控制好的折叠3种方法. 文中介绍一种最新开发出的利用Hadamard激发雕刻的方法. 借助Varian核磁共振系统的高品质射频系统和灵活的软件工具, 用户可以方便的实施新的激发雕 刻方案，极大地改善gHMBC实验的F₁分辨率.     

ISOMERS OF 3,7,11-TRIMETHYLDODECA-2,4,6,8,10- PENTAENAL (A LINEAR ANALOGUE OF RETINAL) and LOWER HOMOLOGUES IN THEIR INTERACTION WITH BOVINE OPSIN and BACTERIOOPSIN

Abstract— The all-trans and 3 mono-cir isomers of the title linear pentaenal have been prepared. Results of their interaction with bovine opsin and bacterioopsin are presented. Likewise, the negative results on two lower member homologs are described. Implications on the specificity of the binding sites are discussed.     

Assignment of the NMR spectra of a potent ribonucleotide reductase inactivator - utilization of HMQC-TOCSY to establish connectivities in exchange broadened spectra

Inverted and Suppressed Direct Response (IDR and SDR, respectively) HMQC-TOCSY experiments are evaluated relative to the conventional HMQC-TOCSY experiment in the assignment of the congested proton and carbon spectra of a 2-acetylpyridine thiocarbonohydrazone used to potentiate the antiviral drug acyclovir. Spectra with moderate overlap can be most expeditiously interpreted using the inverted direct response HMQC-TOCSY variant; spectra with severe overlap can be more readily interpreted if direct responses are suppressed.