Multiple receivers

For a manufacturer the difficulty is to estimate future developments or trends in NMR microscopy. Based on dedicated laboratory-made hardware developed by the NMR microscopy users and on their requests for new commercial hardware and software, the following topics could become more important micro-coil applications, multiple receiver systems and multi-coil arrangements, NMR microscopy at very high magnetic fields, MAS imaging and localized 1H MAS spectroscopy and localized single-shot 2D spectroscopy. There are no clear-cut distinctions between most of the individual topics, as will be discussed in the following sections. 

Multiple Receive Systems and Multi-coil Arrangements... 

Multiple receive systems with multi-coil arrays have become widely distributed in medical MRI. The benefit is the enhancement of the signal-to-noise ratio per time or a reduction of the acquisition time. This technique is not used in NMR microscopy for objects of intermediate size in standard bore (52-mm id) and wide bore (89-mm id) magnets, which are the most widely distributed magnet types for NMR microscopy. The main reason is the restricted space in such magnets for the shim... 

Andersson, S., Pryke, S. R., Omborg, J., Lawes, M. J., and Andersson, M. 2002. Multiple receivers, multiple ornaments, and a trade-off between agonistic and epigamic signaling in a widowbird. Am. Nat. 160 683-691. 

Selective excitation is an efficient method of data collection for samples in which the value of the relaxation time (TRc j) is less than three times the T value of the sample. The smallest possible value of 77 eff is given by n times the data acquisition time for each sample, where n is the number of coils. In cases where very high spectral resolution is required, a large number of coils are used, and/or where the samples have short T values, this method may be of limited use. The use of multiple receivers interfaced with a number of arrays, each containing a smaller number of coils, can potentially overcome this limitation. Alternatively, a one-dimensional CSI method can be used, with the proviso of losses in S/N or potentially longer acquisition times, as mentioned earlier. 

The reaction is conducted in a 250-mL, three-necked flask, fitted with a mechanical stirrer, a thermometer reaching close to the bottom of the flask, and a 25-cm Vigreux column to which has been connected a distillation head with multiple receiver. tert-Butyldichlorophosphine (31.8 g, 0.2 mole) is added to a stirred suspension of NaF (25.2 g, 0.6 mole) in 100 mL of sulfolane over a period of 1 hour. A slow stream of nitrogen is passed through a T-tube connected to the outlet of the distillation apparatus. After the addition of the chloro-phosphine, the reaction mixture is heated as follows 45 minutes at 80°, 15 minutes at 100-180°, and 30 minutes at 180°. Distillation of the fluorophosphine commences at 80° and is complete at 180°. The product is collected in a receiver flask cooled in Dry Ice. fer -Butyldifluorophosphine is obtained as a colorless liquid of bp 41-44° the yield is 20-23 g (79-91%, based on tert-butyl-dichlorophosphine ). Anal. Calcd. for C4H9F2P P, 24.6 F, 30.2. Found P, 24.1 F, 29.0,... 

When multiple receivers are deployed, one should remember that the number of independent baselines is only (n-1), where n is the number of receivers deployed. Although it is economical to deploy multiple receivers, compared with a single pair, the associated logistical problems increase with the number of operational parties involved. It is unusual to deploy more than five receivers simultaneously on an engineering surveying project. 

SDI Bits 10 and 9 provide a Source/Destination Identifier or SDL This is used for multiple receivers to identify the receiver for which the data are destined. It can also be used in the case of multiple systems to identify the source of the transmission. This is used in the case study where a line feeds more than one LRU as is the case with the ADCs. 

The interesting observations on the variety of discrete and different chemicals eliciting the low level, non-repetitive novel substance response reinforce the multiple receiver functionality of the VNO. Sets of molecules contained in the complex urine and single molecules are both capable of eliciting flehmen. The inactivity of chemicals such as phenols, especially 4-methylphenol, identified in urines of several species (Patterson, 1967 Hradecky, 1978 Brown et al., 1978) was expected because of both their volatility and their non-uniqueness in female elephant estrous urine. 

A more recent study employed both direct and indirect covariance on C, N-labelled histidine in a poly crystalline sample [34]. The investigators constructed C—C and N—N correlation maps from a H—H dipolar mediated shift correlation experiment where the and FIDs were simultaneously acquired with multiple receivers. The correlation plots obtained were equivalent to CHHC, NHHN and NHHC spectra. Significant... 

A variation of a simple vacuum system is shown in Fig. 7.9. This is referred to as a central vacuum system in that it uses a single vacuum pump to draw material to multiple receivers on different machines by means of a common vacuum line with sequence valves which open when loading is required at a particular station. 

If it is necessary to use multiple receivers to collect fractions of different boiling ranges, the distillation must be interrupted to change flasks. Remove the heating source with caution and allow the stillpot to cool somewhat. Slowly open the vacuum release valve to re-admit air to the system. When atmospheric pressure is reached, change receivers, close the release valve, re-evacuate the system to the same pressure as previously, reapply heat, and continue distilling. The operation may result in a different pressure in the fully evacuated... 

Detection of Data Integrity Attacks. An arbitrary RTU is set to a malicious state leading to sensor messages in transfer being corrupted. For each received SCADA sensor message on an MTU, the same datum is requested from q different replica locations. With the multiple received messages, the receiver can check for their SCADA payload equality. Simulations use a replication degree of k = Z, i.e., three copies of each DHT key/value pair exist in the network. 

Multistatic Here, one or more transmitters and multiple receivers are located on different receiving platforms or ships. 

Acoustic data fusion is a technique that combines information from multiple receivers or receiving platforms about a common object or channel. Instead of each receiver making a decision, relevant information from the different receivers is sent to a common control unit where the acoustic data is combined and processed (hence the name data fusion). After fusion, a decision can be relayed or fed back to each of the receivers. If data transmission is a concern, due to time constraints, cost, or security, other techniques can be used in which each receiver makes a decision and transmits only the decision. The control unit makes a global decision based on the decisions of all of the receivers and relays this global decision back to the receivers. This is called distributed detection. The receivers can then be asked to re-evaluate their individual decisions based on the new global decision. This process could continue until all of the receivers are in agreement or could be terminated whenever an acceptable level of consensus is attained. 

E. Kupce, NMR with Multiple Receivers, in Modem NMR Methodology, ed. H. Heise, Topics in Current Chemistiy, Springer, 2013, vol. 335, p. 71. 

This chapter will focus on multi-dimensional NMR experiments that have been designed with multiple receivers in mind. We shall discuss the benefits and challenges of such experiments, their applications in NMR of both small organic molecules and bio-molecules (proteins). 

Fig. 22 The processing flow chart for handling data recorded using multiple receivers...

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