scholarly journals EXTIRPATION OF THE THYMUS IN THE GUINEA PIG

1917 ◽  
Vol 25 (1) ◽  
pp. 129-152 ◽  
Author(s):  
Edwards A. Park
Keyword(s):  
Guinea Pig ◽  
Serial Section ◽  
Guinea Pigs ◽  
Close Association ◽  
Main Lobe ◽  
Technical Error ◽  
Serial Sections ◽  
Pharyngeal Pouch ◽  
The Third ◽  
Third Pharyngeal Pouch

1. Accessory lobes of thymus, derived from the third pharyngeal pouch, occurring in close association with the parathyroids from the third pouch, were found in serial section of the cervical tissues of eleven out of fourteen guinea pigs, and probably would have been found in all fourteen but for a technical error. 2. It is probable, therefore, that accessory lobes of thymus having this situation and origin are usually, if not always, present in the guinea pig. 3. Additional accessory lobes of thymus belonging to, but at some distance from the main lobe were also present in several of the animals. 4. The discovery of these accessory lobes makes it certain that the guinea pig is unsuitable material for complete thymectomy, and probably complete extirpation of the thymus in this animal is rarely, if ever accomplished. 5. The extirpation experiments of previous investigators in the guinea pig must now be regarded as partial extirpations, and their results interpreted in that light. 6. Extirpation of the thymus in the guinea pig produced no changes in the writer's experiments. 7. The study of the serial sections of the cervical tissues of the guinea pig indicates that Ruben's statements regarding the parathyroid derived from the fourth pharyngeal pouch in the guinea pig are correct,—that it is much smaller than parathyroid III, may be rudimentary, and is sometimes absent at least on one side. 8. No accessory lobe of thymus was found accompanying the parathyroid from the fourth pouch, a finding also bearing out Ruben's statement that no thymus anlarge springs from the fourth pouch in the guinea pig.

Manipulation of main lobe number and azimuth angle of terahertz-transmitted beams by matrix-form-coding metasurface

2019 ◽  
Vol 125 (9) ◽  
Author(s):  
Bo Fang ◽  
Xun Bie ◽  
Zhigang Yan ◽  
Haiyong Gan ◽  
Chenxia Li ◽  
...  
Keyword(s):  
Azimuth Angle ◽  
Matrix Form ◽  
Main Lobe

scholarly journals AN IMPROVED ESP ALGORITHM FOR MAIN LOBE INTERFERENCE IN SLF COMMUNICATION

2018 ◽  
Vol 73 ◽  
pp. 163-171
Author(s):  
Ning Zhang ◽  
Yu-Zhong Jiang ◽  
Yang Liu
Keyword(s):  
Main Lobe

scholarly journals Development and Analysis of New NLFM Waveform for Achieving Sidelobe Reduction and Narrowing of Main lobe Width

2021 ◽  
Vol 9 (7) ◽  
pp. 885-889
Keyword(s):  
Doppler Effect ◽  
Background Noise ◽  
Sampling Rate ◽  
Ambiguity Function ◽  
Main Lobe ◽  
The Doppler Effect ◽  
The Impact ◽  
Lobe Width

Aimed at narrowing main lobe width and reduced sidelobe values, we developed three new NLFM chirp waveforms. The ambiguity function and the impact of sampling rate and compression ratios of these waveforms are analyzed. Their performance is examined against the doppler effect and background noise. One of the three designed NLFM chirp waveforms is useful in applications requiring side lobes of -50 dB and narrow main lobe width. The new waveform could achieve reduced sidelobes and narrow main lobe width compared to LFM and other NLFM waveforms

scholarly journals Optimization of two-stage NLFM signal using Heuristic approach

2020 ◽  
Vol 13 (44) ◽  
pp. 4465-4473
Author(s):  
Chandu Kavitha ◽  
Keyword(s):  
Optimization Algorithm ◽  
Frequency Modulation ◽  
Pulse Compression ◽  
Piecewise Linear ◽  
Side Lobe ◽  
Linear Frequency Modulation ◽  
Main Lobe ◽  
Design And Optimization ◽  
Linear Frequency ◽  
Scripting Language

Background/Objectives: The design of appropriate Non-Linear Frequency Modulation (NLFM) signals continues to be the focus of research in radar pulse compression theory for sidelobe reduction. This study focuses on a heuristic design and optimization algorithm to optimize the side lobe values of the NLFM signal designed using two-piece wise linear frequency modulation (LFM) functions. Methods: 1) Heuristic search identifies the optimum B1, T1, and B2, T2, which yield the lowest sidelobe value of the designed function.2) Compute all the side lobe values of the designed NLFM signal using an algorithm developed in Python scripting language. To plot a complete contour map for all the calculated side lobe values, which helps identify the associated variations in the range of side lobe values. Finally, optimize the side lobe values keeping the main lobe width and time-bandwidth (BT) product unchanged by designing a dynamic optimization algorithm. Findings: The algorithm developed considered all side lobe levels after the main lobe for optimization. The focus is mainly on the peak sidelobe ratio (PSLR) value without affecting the other parameters. The results demonstrate that the achieved side lobes exhibit their desired levels. Novelty: The method is useful in all types of hardware associated with weather radar applications to military solutions. The technique can be extended to other multistage signals consisting of piecewise linear Segments. Keywords: Contour; LFM; NLFM; optimization; PSLR

Memoirs: On the Structure of the Nephridia and ‘funnels’ of the Indian Leech Hirudinaria with remarks on these organs in Hirudo

1938 ◽  
Vol s2-81 (321) ◽  
pp. 27-80
Author(s):  
M. L. BHATIA
Keyword(s):  
Early Stage ◽  
Fibrous Tissue ◽  
Outer Wall ◽  
Central Canal ◽  
The Body ◽  
Main Lobe ◽  
Excretory Function ◽  
Ciliary Action ◽  
Apical Lobe ◽  
Discrete Structures

1. The nephridial system of Hirudinaria consists of a series of seventeen pairs of nephridia metamerically arranged in somites VI to XXII. The first sis pairs occur in the pretesticular segments (VI-XI), while the remaining eleven pairs lie in the testicular segments (XII-XXII). 2. A typical nephridium consists of the following parts: (i) the initial lobe, (ii) the apical lobe, (iii) the inner lobe, (iv) the main lobe, (v) the vesicle-duct and the vesicle. All the nephridia in the testicular region possess ‘funnels’ (ciliated organs) which are enclosed within the ampullae of the perinephrostoniial sinus. There is no continuity or connexion of these ‘funnels’ with the nephridia in the adult leech. 3. The inner end of the initial lobe is directed towards the testis-sac and either ends freely within the connective tissue without coming in contact with the testis-sac, o r- is embedded in fibrous tissue in external contact with the wall of the sac, or becomes incorporated within the outer wall of the perinephrostomial sinus. 4. The initial lobe (testis-lobe) forms a very long coiled string of cells round the apical lobe and part of the inner lobe. The inner lobe (the ‘recurrent lobe’ of Bourne) forms a distinct strip of nephridial tissue enclosed between the two limbs of the main lobe besides a small piece which runs alongside the apical lobe. The inner lobe canals serve to connect the intra-cellular canals of all the lobes with one another. 5. The cells of the different lobes of the nephridium are tunnelled through by intra-cellular canals and canaliculi which form a continuous branching network throughout the body of the nephridium. Besides, there is an intra-cellular central canal which makes 1 3/4 ‘rounds’ through the various lobes of the nephridium and opens into the vesicle. The intra-cellular canals and canaliculi open directly or indirectly into the central canal. 6. The vesicle has no muscular layer, and its wall is not contractile. The evacuation of the contents of the vesicle is brought about by the contraction of ventro-lateral mameles of the bodywall that extend across all the resides. The vesicle and the terminal excretory duet do not develop from the rudiments of the true nepfaritliam, but are formed from an ingrowth of the epidermis. 7. A fully developed adult ‘funnel’ (ciliated organ) is a compound structure consisting of (1) a central reservoir and (2) a large number of small independent funnels set on the reservoir and opening into it. The funnels are profusely dilated. Each funnel is composed of five to six cells, and has the appearance of an ear-lobe with a broad distal and a narrow proximal end. 8. The reservoir is the seat of manufacture of corpuscles which are thrown out of the reservoir through the funnels into the surrounding sinus by the active movements of the cilia of the numerous funnels. 9. The ‘funnel’ is not a degenerate structure. It has, infact, multiplied into numerous small ciliated funnels, which, are much more effective in their ciliary action than a single funnel, even of a large size, could be. Cilia of the funnels show very vigorous movements which keep the fluid in the sinus in constant active circulation. The ciliated organ, instead of serving a renal excretory function, has here become subservient to the sinus-system. 10. The botryoidal vessels are in direct communication with the perinephrostomial sinus. Possibly the corpuscles take up pigment and become the chloragogen cells in the botryoidal vessels. 11. In the embryonic condition the ‘funnel’ is a solid mass of cells which is distinctly continuous with the nephridinm by means of a delicate strand of cells. This connexion of the ‘funnel’ with the nephridium snaps later, and the two become discontinuous and discrete structures. In the embryonic solid ciliated organ the funnel-forming cells can be clearly distinguished from the cells of the reservoir. The ‘funnel’ becomes enclosed at an early stage in the perinephrostomial sinus, which is a part of the reduced coelom. 12. The nephridial system of Hirudo is essentially similar to that of Hirudinaria. In Hirudo the initial lobe does not coil round the apical lobe, but forms one mass round the ampullae of the perinephrostomial sinus and another between the apical and main lobes. The inner end of the nephridium is closed as in Hiradinaria. The ‘funnels’ have the same structure and perform the same function as in Hirudinaria.

Excitation series design and pulse compression synthesis for high-resolution Lamb wave inspection

2018 ◽  
Vol 18 (5-6) ◽  
pp. 1464-1478
Author(s):  
Jiadong Hua ◽  
Liang Zeng ◽  
Jing Lin ◽  
Liping Huang
Keyword(s):  
Lamb Wave ◽  
Pulse Compression ◽  
Lamb Waves ◽  
Dispersion Compensation ◽  
Synthesis Method ◽  
Side Lobe ◽  
Main Lobe ◽  
Window Functions ◽  
Windowing Technique ◽  
Lobe Width

Lamb wave pulse compression is a promising technique for ultrasonic nondestructive evaluation and structural health monitoring, in which the excitation waveform is designed to exhibit attractive auto-correlation characteristics including short main-lobe width and small side-lobe amplitude. However, narrowing main-lobe will increase side-lobe amplitude, and vice versa. Conventional time windowing technique is a balance between main-lobe width and side-lobe amplitude. An improvement over time windowing is proposed using pulse compression synthesis method. In this method, a series of excitation waveforms are used to actuate Lamb waves, each response is processed by pulse compression, and all the compression signals are summed together. The excitation series are constructed as linear chirps weighted with different combinations of rectangular and Hanning window functions. The selection of the combination coefficients is optimized to ensure best signal summation. The effectiveness of the proposed method is demonstrated by an experiment, and the robustness to inaccuracy in dispersion compensation is also evaluated. Application of the proposed method for damage detection is demonstrated by a further experiment.

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