C.H. van Niekerk

A robust integrated multibias parameter-extraction method for MESFET and HEMT models

An integrated multibias extraction technique for MESFET and high electron-mobility transistor (HEMT) models is presented in this paper. The technique uses S-parameters measured at various bias points in the active region to construct one optimization problem, of which the vector of unknowns contains a set of bias-dependent elements for each bias point and one set of bias-independent elements. This problem is solved by an extremely robust decomposition-based optimizer, which splits the problem into n subproblems, n being the number of unknowns. The optimizer consistently converges to the same solution from a wide range of randomly chosen starting values. No assumptions are made concerning the layout of the device or the bias dependencies of the intrinsic model elements. It is shown that there is a convergence in the values of the model elements and a decrease in the extraction uncertainty as the number of bias points in the extraction is increased. Robustness tests using 100 extractions, each using a different set of random starting values, are performed on measured S-parameters of a MESFET and pseudomorphic HEMT device. Results indicate that the extracted parameters typically vary by less than 1%. Extractions with up to 48 bias points were performed successfully, leading to the simultaneous determination of 342 model elements.

Different synchronization techniques in Boer goat does outside the normal breeding season

Synchronization techniques outside the normal breeding season were evaluated on 85 Boer goats with intravaginal progestagen sponges, sponges plus prostaglandin, and two injections of prostaglandin, with or without 500 IU PMSG. Oestrous response following the double prostaglandin injection regime was significantly (P < 0.01) lower than in the intravaginal sponge and sponge plus protaglandin groups (with and without exogenous PMSG). The PMSG led to a higher (P < 0.01) oestrous response in goats treated with intravaginal sponges only (100.0% vs. 53.3%). Administration of 500 IU PMSG led to a shorter time interval (P<0.01) from cessation of treatment to the onset of oestrus in the intravaginal sponge and sponge plus prostaglandin groups (40.0 vs. 72.1 hr and 39.3 vs. 71.3hr, respectively). Time interval from treatment to the LH peak was shorter (P<0.01) in the groups (excluding the double injection prostaglandin groups) receiving 500 IU PMSG, with no significant difference between the two intravaginal sponge treated groups. No significant differences in the time interval between LH peak and onset of the oestrous period was recorded between treatment groups. There was no significant difference in fertility between the intravaginal sponge and sponge plus prostaglandin groups (73.3 vs. 66.7% with PMSG and 53.3 vs. 60.0% without PMSG). Intravaginal sponge and sponge plus prostaglandin techniques (with PMSG) are effective as synchronizing agents outside the breeding season in Boer goat does. The double prostaglandin injection regime on the other hand proved ineffective outside the breeding season.

Effect of pregnant mare serum gonadotrophin (PMSG) and route of administration after progestagen treatment on oestrus and LH secretion in the Boer goat

During the breeding season, 94 mature Boer goats were treated with intravaginal progestagen sponges (MAP, 60 mg) for a period of 14 days. Upon sponge withdrawal, goats received 300 i.u. PMSG either subcutaneously (n = 32) or intramuscularly (n = 30). A control group was not treated with PMSG (n = 32). Administration of 300 i.u. PMSG at sponge withdrawal had no significant effect on the number of animals exhibiting oestrus in each group. Interval from sponge withdrawal to commencement of oestrus was shorter for intramuscular (P < 0.01) and subcutaneous (P < 0.05) PMSG-treated groups than controls, with the route of PMSG administration not having a significant effect. Mean duration of induced oestrus was significantly shorter (P < 0.05) in the control group. The interval from onset of oestrus to the occurrence of the preovulatory LH peak was shorter (P < 0.05) in the group receiving PMSG subcutaneously.

Ovulation in the boer goat doe

Abstract A total of 40 Boer goat does were slaughtered 26 ( n = 15), 32 ( n = 10) or 38 ( n = 15) h after onset of oestrus. Blood was sampled from eight does in each group for serum progesterone and LH concentration determinations from the time of onset of oestrus to slaughter. Follicular activity (follicles greater than 0.2 cm) in the ovary increased significantly ( P Mean interval from onset of oestrus to the pre-ovulatory LH peak was 11.3 ± 4.3; 13.1 ± 3.0 and 10.5 ± 4.1 h for the groups slaughtered at 26, 32 and 38 h, respectively. The interval between the LH peak and ovulation was relatively constant at 24.7 h for all does. Knowledge of the time of onset of the LH peak permits approximate predictions regarding the time of ovulation.

Anaplasmosis in improved boer goats in South Africa artificially infected with Anaplasma ovis

Abstract Blood originating from Boer goat does which had aborted and were suspected to be infected with Anaplasma ovis organisms, was injected into splenectomised does. Anaplasmosis was diagnosed in these splenectomised does 6 days after infection. When 6% of the red blood cells of the splenectomised does was infected, 50 ml of their blood was transferred intravenously to each of 20 non-infected Boer goat does in different stages of pregnancy. A clinical, pathological and haematological study was done on a daily basis on these pregnant does (n=19) and their fetuses for the next 25 days, as well as on all aborted fetuses and kids that died shortly after birth. While confined to their isolation pens, the does showed few noticeable signs of anaplasmosis, but when they were forcefully exercised, the does that developed an anaemia showed rapid fatigue and some showed severe respiratory distress. Ten of the 19 infected does, especially those that developed a high body temperature and severe anaemia, lost their fetuses. It was demonstrated on blood smears that A. ovis organisms migrate through the placenta to the red blood cells of the fetus to cause anaemia and death of the fetus in utero.

Performance and limitations of decomposition-based parameter extraction procedures for FET small-signal models

A recently proposed optimizer-based parameter-extraction technique using adaptive decomposition is subjected to a systematic and rigorous evaluation. The technique is shown to be robust and accurate under varying starting conditions. A study of convergence performance based on decomposition theory and test results is presented. Robustness tests are used to show that commonly used statistical descriptions such as mean and standard deviation are inadequate for presenting these types of test data.

Oestrus synchronization in sheep with progesterone-impregnated (MAP) intravaginal sponges and a prostagland in analogue

Abstract A double injection of PGF2α at two different dosage levels, 5 mg and 10 mg, eleven days apart, were compared with a combination of MAP-sponges and 5 mg or 10 mg PGF2α. The combination of MAP-sponges plus 10 mg PGF2α gave the best syn=chronization results (93,4%), as well as the best conception rate (84,9%) when ewes were inseminated on a fixed time basis 68 and 80 hours after treatment.

A new hybrid multibias analytical/decomposition-based FET parameter extraction algorithm with intelligent bias point selection

A new hybrid multibias analytical/decomposition-based parameter extraction procedure for GaAs FETs is described. The analytical calculations are integrated into an existing decomposition-based optimizer in a complementary approach, further increasing the robustness of the existing algorithm. It is illustrated that, in order to increase the reliability with which the full 15-element small-signal model can be extracted, it is necessary to exploit the underlaying characteristics of the system and the measured data used. This is achieved through the use of cold S-parameter data, along with simple modifications to the extraction algorithm, and a new intelligent selection algorithm for the active bias points used in the multi-bias extraction. The selection algorithm employs a simple geometric abstraction for the S-parameter data that allows it to select bias points that maximize the information available to the extraction procedure. The new selection algorithm shows for the first time what the influence of the bias points is on the performance of a multibias extraction procedure. Experimental results proving the robustness and accuracy of the described procedures are presented.

Macroscopic uterine involution in the post-partum Boer goat

Abstract Sixteen Boer goat does were slaughtered at different intervals between parturition and 34 days post-partum and all the relevant macroscopic uterine measurements recorded. Involution of the post-partum uterus and macroscopic changes of different parameters are described and predicted in the Boer goat by Y = A e Bt + Ct 2 . Considerable anatomical variation existed between individuals, but the objective was to monitor when the uterus had macroscopically involuted. Mass and volume of the uterus declined drastically after parturition. According to the model, the involution process was complete by 27.0 and 27.4 days for the uterus mass and volume, with rate of decrease 17.2 ± 2.7% and 20.8 ± 3.0%/day for the first 34 days post-partum, respectively. The external diameter of the cervix decreased in size from 7.5 cm following parturition to approximately 2.0 cm by day 4 post-partum. This decrease was theoretically complete 20.7 days post-partum. Similarly the external diameter of the body of the uterus was static 21.3 days post-partum with a rate of decrease of 12.4 ± 2.5%/day. Mean length and diameter of the uterine horns reached normal, non-pregnant size by 24 and 27.9 days post-partum, respectively. Diameter of the largest caruncles exhibited an initial fast decline (11.2 ± 1.7%/day for the entire observation period), tapering off towards the end of the period. Caruncles were “back to normal” by 26.3 days post-partum. The involution process of the uterus was macroscopically complete by approximately 28 days post-partum in the Boer goat.

A NEW APPROACH FOR THE EXTRACTION OF AN FET EQUIVALENT CIRCUIT FROM MEASURED S PARAMETERS

A new method for the entraction of the 13-element GaAs FET model from hot S parameters is presented. The method reduces the uniqueness problem that mists between the parasitic gate resistance R, and the channel resistance K,. Ihirteen error functions are used, with the order of o~~rimiza~ion determined through a principle-components semihi& analysis. 0 1996 John Wiley & Sons, Inc.