Interpolated Coarse Models for Microwave Design Optimization With Space Mapping

The efficiency of space-mapping optimization depends on the quality of the underlying coarse model, which should be sufficiently close to the fine model and cheap to evaluate. In practice, available coarse models are often cheap, but inaccurate (e.g., a circuit equivalent of the microwave structure) or accurate, but too expensive (e.g., a coarse-mesh model). In either case, the space-mapping optimization process exhibits substantial computational overhead due to the excessive fine model evaluations necessary to find a good solution if the coarse model is inaccurate, or due to the cost of the parameter extraction and surrogate optimization sub-problems if the coarse model is too expensive. In this paper, we use an interpolation technique, which allows us to create coarse models that are both accurate and cheap. This overcomes the accuracy/cost dilemma described above, permitting significant reduction of the space-mapping optimization time. Examples verify the performance of our approach.     

Brain stem integration of vocalization: role of the nucleus retroambigualis

1. The descending pathways that mediate the periaqueductal gray (PAG)-evoked coordination of respiratory, laryngeal, and orofacial activity for vocalization have yet to be delineated. Two hypotheses have been offered. One theory is that this activity is mediated by a diffuse descending projection to parvocellular reticular interneurons, adjacent to the relevant laryngeal and orofacial motoneuronal pools. The second hypothesis is that the motor activity for vocalization is integrated via a projection from the PAG to a caudal medullary column of neurons, the nucleus retroambigualis (NRA). These hypotheses were tested with the use of a series of medullary transections combined with PAG stimulation. Transections that eliminated, in a series of caudal-to-rostral steps, the NRA, also eliminated the PAG-evoked cricothyroid and most of the thyroarytenoid laryngeal motor activity. These results indicate that the final common pathway for much of the laryngeal activity in PAG-evoked vocalization includes un initial synapse in the caudal medulla, presumably in the NRA. 2. The electromyographic changes evoked by microinjection of D,L-homocysteic acid (DLH) in the NRA of the unanesthetized, precollicular decerebrate cat were analyzed in order to delineate the NRA contribution to the coordinated respiratory, laryngeal, and oral muscle changes in vocalization. A total of 415 DLH injection sites were located at or caudal to the level of the obex. Vocalization was evoked at 46 of these sites, which were all confined to a restricted region of the ventrolateral medulla 1-3 mm caudal to the obex. This region corresponded to the rostral half of the NRA and the immediately adjacent medullary tegmentum. 3. In all experiments evidence was obtained that variable muscle activation, rather than functional and integrated muscle patterns, was represented within the NRA. Vocalization evoked by DLH microinjection in the NRA was usually associated with excitation of the cricothyroid, thyroarytenoid, external oblique, internal oblique, internal intercostal, and diaphragm muscles that occurred in a different manner from site to site. That is, injection at sites separated by 0.3-0.5 mm evoked quite different responses. 4. NRA-evoked vocalization was compared with PAG-evoked vocalization using small injections (1.5-4.5 nl) into each region. As well, larger microinjections (15-120 nl) into NRA were made for comparison with previous results from the PAG using similar doses. Within the PAG, stereotyped and relatively "fixed" patterns of muscle activity are represented, whereas within the NRA there was no representation of specific muscle patterns, but rather a partial topographic separation of "premotor neurons" regulating different muscles. Correspondingly, stereotyped vocalizations were never evoked from the NRA. Further, most NRA-evoked vocalizations were unusual in quality and would not be identified generally as feline. 5. Evidence was obtained for a separation of pathways from the PAG regulating sound production and orofacial modulation of that sound. In contrast to the results from the PAG, excitation of NRA neurons rarely evoked activity in the oral muscles (genioglossus or anterior belly of digastric) or orofacial modulation of sound production. 6. Our finding suggests that the NRA serves as an important substrate for the generation of respiratory pressure and larynges adduction, which are two essential aspects of not only vocalization but also several behaviors involving Valsava maneuvers such as coughing, vomiting, and defecation.     

The evaporation signal from α particles stopped in superfluid helium

Alpha particles stopped in a 3 liter volume of liquid helium at 30 mK are observed by the calorimetric detection of helium atoms evaporated from the free surface of the liquid. Quantum evaporation of the helium is produced by the rotons that are created by the particle. While the energy spectrum of the 5.5 MeV 's from the²⁴¹Am source has a width of less than 0.5%, the energy distribution of the observed evaporation signals extends from the low energy threshold of several keV up to a maximum of several 100 keV, depending on geometrical factors and the collection area of the calorimeter. The origin of the observed distribution may result in part from the presence of the substrate and a dependence on the direction of the track of the particle. A simple model of the generation of rotons by the particle will be discussed.     

Implications of Weak Link Effects on Thermal Characteristics of Transition-Edge Sensors

Weak link behavior in transition-edge sensor (TES) microcalorimeters creates the need for a more careful characterization of a device’s thermal characteristics through its transition. This is particularly true for small TESs where a small change in the bias current results in large changes in effective transition temperature. To correctly interpret measurements, especially complex impedance, it is crucial to know the temperature-dependent thermal conductance, G(T), and heat capacity, C(T), at each point through the transition. We present data illustrating these effects and discuss how we overcome the challenges that are present in accurately determining G and T from I–V curves. We also show how these weak link effects vary with TES size. Additionally, we use this improved understanding of G(T) to determine that, for these TES microcalorimeters, Kaptiza boundary resistance dominates the G of devices with absorbers while the electron-phonon coupling also needs to be considered when determining G for devices without absorbers     

Hypotension following acute hypovolaemia depends on the caudal midline medulla

Acute hypovolaemia evokes abrupt, life-threatening hypotension and bradycardia. Hypotension can be evoked also by excitation of the caudal midline medulla (CMM). This study investigated the possible contribution of the CMM depressor area to hypotension evoked by acute hypovolaemia. Inactivation of the CMM, with either lignocaine or cobalt chloride did not alter resting arterial pressure. However lignocaine injections blocked the fall in arterial pressure, and cobalt chloride injections delayed the onset and significantly attenuated the size of hypovolaemic-evoked hypotension. These findings suggest that the CMM is a key region triggering hypotension after blood loss, and that the brain areas mediating cardiovascular response to challenges such as acute hypovolaemia are not the same areas that regulate resting arterial pressure.     

Space Mapping Design Framework Exploiting Tuning Elements

Inspired by the ideas of “simulator-based” tuning, implicit space mapping, and surrogate optimization, we propose an implementable microwave design framework. In this framework, we alter an electromagnetic (EM) model by embedding suitable tuning elements. The resulting tuning model is aligned with the original unaltered EM model. We then designate the aligned tuning model as surrogate for design optimization purposes. We illustrate our tuning space mapping framework using a simple microstrip line example. Several microwave examples, including a low-temperature co-fired ceramic filter demonstrate the framework's implementation and robustness.      

Cardiovascular effects of microinjections of opioid agonists into the ''Depressor Region'' of the ventrolateral periaqueductal gray region

Differentiating the binding properties of applied lectins should facilitate the selection of lectins for characterization of glycoreceptors on the cell surface. Based on the binding specificities studied by inhibition assays of lectin-glycan interactions, over twenty Gal and/or GalNAc specific lectins have been divided into eight groups according to their specificity for structural units (lectin determinants), which are the disaccharide as all or part of the determinants and of GalNAc alpha 1-->Ser (Thr) of the peptide chain. A scheme of codes for lectin determinants is illustrated as follows: (1) F (GalNAc alpha 1-->3GalNAc), Forssman specific disaccharide--Dolichos biflorus (DBL), Helix pomatia (HPL) and Wistaria floribunda (WFL) lectins. (2) A (GalNAc alpha 1-->3 Gal), blood group A specific disaccharide--Codium fragile subspecies tomentosoides (CFT), Soy bean (SBL), Vicia villosa-A4 (VVL-A4), and Wistaria floribunda (WFL) lectins. (3) Tn (GalNAc alpha 1-->Ser (Thr) of the protein core)--Vicia villosa B4 (VVL-B4), Salvia sclarea (SSL), Maclura pomifera (MPL), Bauhinia purpurea alba (BPL) and Artocarpus integrifolia (Jacalin, AIL). (4) T (Gal beta 1-->3GalNAc), the mucin type sugar sequences on the human erythrocyte membrane(T alpha), T antigen or the disaccharides at the terminal nonreducing end of gangliosides (T beta)--Peanut (PNA), Bauhinia purpurea alba (BPL), Maclura pomifera (MPL), Sophora japonica (SJL), Artocarpus lakoocha (Artocarpin) lectins and Abrus precatorius agglutinin (APA).(5) I and II (Gal beta 1-->3(4)GlcNAc)--the disaccharide residue at the nonreducing end of the carbohydrate chains derived from either N- or O-glycosidic linkage--Ricinus communis agglutinin (RCA1), Datura stramonium (TAL, Thorn apple), Erythrina cristagalli (ECL, Coral tree), and Geodia cydonium (GCL). (6) B (Gal alpha 1-->3Gal), human blood group B specific disaccharide--Griffonia(Banderiaea) simplicifolia B4 (GSI-B4). (7) E (Gal alpha 1-->4Gal), receptors for pathogenic E. coli agglutinin, Shiga toxin and Mistletoe toxic lectin-I (ML-I) and abrin-a.     

Optimizing Arrays of Position-Sensitive TESs

We are developing position-sensitive transition-edge sensors (PoSTs) for future X-ray astronomy missions such as NASAs Constellation-X. The PoST consists of 1 or more transitions-edge sensors (TESs) thermally connected to a large X-ray absorber, which through heat diffusion, gives rise to position dependence. The development of PoSTs is motivated by the desire to achieve the largest focal-plane coverage with the fewest number of readout channels. In this paper, we investigate optimized signal processing algorithms for single channel PoSTs or ‘Hydras’ (consisting of 4-absorbers connected to 1 TES). Using simulated data, we investigate the impact different parameters such as the thermal conductances and the inductance of the bias circuit have on device performance.      

Combining Coarse and Fine Models for Optimal Design

In this article we reviewed the implicit space mapping concept. We illustrated it using a simple tapped-line microstrip filter example. We demonstrated the robustness of our approach by performing an accurate design of a microstrip hairpin filter. A detailed and easy-to-follow design optimization procedure was provided and the Agilent ADS implementation of the algorithm was described. A good electromagnetically validated design in Sonnet em was obtained in a few fine model simulations. Implicit space mapping is a simple approach to combine a circuit-theory based CAD model and an EM simulator model to achieve fast and accurate optimal design and modeling.     

Low Temperature Properties of Erbium In Gold

The properties of dilute alloys of Er in Au have been studied, principally below 100 mK, in connection with the use of this system in thermometry and in microcalorimetry for particle detection. Measurements are reported of (1) the magnetization at high temperatures and high field, (2) the magnetization in low fields with temperatures extending down to 0.1 mK, and (3) the heat capacity as a function of temperature and field at low temperatures. These measurements are analyzed to provide information of several properties of the Er³⁺ ion in the Au lattice, in particular, the crystal field parameters, the exchange interaction of the 4f electrons with the conduction electrons, and the spin glass freezing temperature.