Alkyl‐Tethered Bis‐Phosphoryl Compounds with two 1,3,2‐Benzodiazaphosphorinone Units; Oxidation,Complexation, and X‐Ray Structure Analysis of Selected Compounds

The reaction of the bis‐chlorophosphines 1 a – 1 d with bis(2‐chloroethyl)amine hydrochloride in the presence of triethylamine and with various trimethylsilylamines led to a new class of bis‐phosphorus ligands 2 a – 2 c and 3 a – 3 g . ³¹P‐NMR studies suggested that the bis‐phosphorus ligands undergo rotation reactions about the alkyl bridge in polar solvents. Compounds 2 a – 2 c showed initially only one sharp singlet each in their ³¹P‐NMR spectra. After a few days at room temperature, two signals were observed. Similar results were observed for 3 a – 3 g . In the solid state, the two phosphorus atoms in 2 c are not equivalent, as was confirmed by the observation of two signals in the solid state ³¹P‐NMR spectrum. Oxidation reactions of 2 a – 2 c by the hydrogen peroxide‐urea 1 : 1 adduct (NH₂)₂C(:O) · H₂O₂ led to the formation of the corresponding phosphoryl compounds 4 a – 4 c . Reaction of 2 a and 3 a with Pt[COD]Cl₂ (COD = 1.5‐Cyclooctadiene) furnished the complexes 5 and 6 . The NMR spectra suggested that the two chlorine atoms are in cis position. X‐ray structure analyses were conducted for 2 a , which exhibits twofold symmetry; 2 c , which is linked into dimers by hydrogen bonds C–H…O; and 6 , confirming the cis configuration.     

Mechanism and origin of stereoselectivity in Robinson annulations leading to bicyclo[3.3.1]nonanes: a rare Curtin–Hammet scenario

Computational studies on the mechanism and diastereoselectivity of base catalyzed synthesis of bicyclo[3.3.1]nonanes by Robinson annulation are reported. Three possible mechanisms were considered, and only the methanol assisted H‐shift process could be the favorable pathway. We have discovered a rare Curtin–Hammet scenario: rate determining steps for the two diastereomeric products formed are completely different reactions, and a correction factor should be considered when gauging the ratio of products from competing pathways. The pathway leading to the anti product is kinetically preferred, which is consistent with experimental results. Finally, the ratio of the two products was rationalized. Copyright © 2016 John Wiley & Sons, Ltd.     

A multi-state model to improve the design of an automated system to monitor the activity patterns of patients with bipolar disorder

This paper describes the role of mathematical modelling in the design and evaluation of an automated system of wearable and environmental sensors called PAM (Personalised Ambient Monitoring) to monitor the activity patterns of patients with bipolar disorder (BD). The modelling work was part of an EPSRC-funded project, also involving biomedical engineers and computer scientists, to develop a prototype PAM system. BD is a chronic, disabling mental illness associated with recurrent severe episodes of mania and depression, interspersed with periods of remission. Early detection of the onset of an acute episode is crucial for effective treatment and control. The aim of PAM is to enable patients with BD to self-manage their condition, by identifying the person's normal ‘activity signature’ and thus automatically detecting tiny changes in behaviour patterns which could herald the possible onset of an acute episode. PAM then alerts the patient to take appropriate action in time to prevent further deterioration and possible hospitalisation. A disease state transition model for BD was developed, using data from the clinical literature, and then used stochastically in a Monte Carlo simulation to test a wide range of monitoring scenarios. The minimum best set of sensors suitable to detect the onset of acute episodes (of both mania and depression) is identified, and the performance of the PAM system evaluated for a range of personalised choices of sensors.     

Silica passivation efficiency monitored by a surface-bound fluorescent dye

A new method for evaluating surface passivation of silicon surfaces using a strongly adsorbing and fluorescing perylenediimide (PDI) dye is reported. Silanes containing differing reactive groups delivering a trimethylsilyl moiety were investigated for their ability to passivate glass surfaces, both from solution and in the vapor phase, as a function of temperature and concentration. Among the silanizing agents used in this study were 1,1,1,3,3,3-hexamethyldisilazane ( HMDS), allyltrimethylsilane ( TMS-A), chlorotrimethylsilane ( TMS-Cl), N-(trimethylsilyl)imidazole ( TMS-Im), and N, N-dimethylaminotrimethylsilane ( TMS-DMA). Surface coverage was determined using fluorescence intensity. The highest surface coverage films were obtained on glass treated with HMDS vapor at 280 degrees C or with solutions of TMS-Im or TMS-DMA at 105 degrees C. These studies provide important insight into the optimal methods for surface passivation.     

The search for a potentially prebiotic synthesis of nucleotides via arabinose-3-phosphate and its cyanamide derivative

For the RNA world hypothesis to be accepted, the constitutional self-assembly of RNA will have to be demonstrated. Conceptually, the simplest route to RNA involves nucleotide polymerisation. Activated pyrimidine nucleotides can be derived from arabinose-3-phosphate under potentially prebiotic conditions, but the prebiotic synthesis of this sugar phosphate has not hitherto been investigated. The results of synthetic approaches involving phosphorylation, phosphate migration and 2,3-C--C bond construction are described herein.     

64×64 pixel smart sensor array for laser Doppler blood flow imaging

What is believed to be the first fully integrated two-dimensional complementary metal oxide semiconductor (CMOS) imaging array for laser Doppler blood flow imaging is demonstrated. The sensor has 64×64 pixels and includes both analog and digital on-chip processing electronics. This offers several potential advantages over commercial sensors as the processing is tailored to the signals of interest and the data bottleneck that exists between the sensor and processing electronics is overcome. To obtain a space efficient design over 64×64 pixels means that standard processing electronics used off-chip cannot be implemented. Images of both simulated blood flow responses and a blood flow occlusion test demonstrate the capability.     

GaAs Schottky devices for submillimeter wavelengths

Conclusion The above analyses assume the absence of excess noise in the Schottky barrier mixer diode. Achievement of such a condition is dependent not only on the absence of interfacial stress in the device structure, but also on device surface properties. Reduction of excess noise caused by these two mechanisms is discussed by Sherrill, et al.,⁽¹⁰⁾ and Kattman, et al.⁽¹¹⁾ Minimum conversion loss in the THz range occurs for mixer diode with the smallest possible junction capacitance. This capacitance can be reduced along with the R_s, C_j(0) product by decreasing the device area and increasing the active layer impurity concentration. It was shown above that this impurity concentration increase will (a) permit higher frequency of operation, (b) cause a lower intrinsic conversion loss, and (c) be responsible for an increase in mixer diode I–V slope parameter, V₀. The only potentially negative effect comes from (c), but the analysis reviewed in the last section shows that an increase in V₀ has a minimal effect on mixer noise temperature for terahertz range operation. Experimental results of Dr. H. P. Röser⁽¹²⁾ to frequencies as high as 2.5 THz are in agreement with these predictions.It is thus concluded on the basis of the above four analyses of device mixer noise temperature and conversion loss that reasonable Schottky barrier mixer diode operation can be expected to at least 10 THz.This work was supported in part by the National Science Foundation under Grant ECS-8412477     

μ+ SR studies on pure MnF2 and site-diluted (Mn0.5Zn0.5)F2SR studies on pure MnF2 and site-diluted (Mn0.5Zn0.5)F2

Positive muon spin rotation and relaxation measurements have been carried out on the antiferromagnets, pure MnF₂ and site-diluted (Mn_0.5Zn_0.5)F₂, above and below the Néel temperature T_N using single-crystal specimens. Two different muon signals have been found in the pure MnF₂; with the precession frequency υ_A for the site A and υ_B for the site B measured in zero external magnetic field at T=5 K. We propose a picture that the signal from the A site represents the “muonium” state, and discuss the characteristic features of muonium in magnetic materials. The spin relaxation rate 1/T₁, measured in zero external field, decreases rapidly with decreasing temperature below T_N. The mechanism of the spin relaxation above T_N is explained by the exchange fluctuations of the Mn moments, while below T_N by the Raman scattering of spin waves. At the same normalized temperature T/T_N, 1/T₁ observed in the diluted (Mn_0.5Zn_0.5)F₂ is significantly larger than that in the pure MnF₂ below T_N. The difference between the pure and diluted systems is related to the large spectral weight of low-energy magnons in (Mn_0.5Zn_0.5)F₂ found by neutron scattering.     

o-Cyclohexadiamine complexes of some diorganotin,mono-organtotin and stannic carboxylates: Synthesis and spectral properties

o-Cyclohexadiamine (the base component of tetraplatin) adducts of Ph₂Sn(OCOCH₃)₂, nBu₂Sn(OCOH₃)₂, (PhCH₂)₂Sn(OCOCH₃)₂, PhSn(OCOCF₃)₃, BuSn(OCOCH₃)₃ and Sn(OCOCH₃)₄ have been synthesized and characterized by elemental analysis and spectroscopy. The compounds appear to be the first such adducts in their class.