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PURPOSE/OBJECTIVE(S) Stereotactic body radiotherapy (SBRT) is an emerging non-invasive treatment in the management of cardiac arrhythmias. The purpose of this research is to evaluate the MR imaging in the detection of radioablation lesion at the cavotricuspid isthmus (CTI) in mini pigs. MATERIALS/METHODS Four mini pigs underwent magnetic resonance (MR) evaluation of heart function and invasive electrophysiology assessment using electroanatomical mapping (EAM) before and 3 months after SBRT with single-fraction doses of 25Gy at the CTI. SBRT simulation, planning, and treatments were performed with the use of standard techniques. MR examination, including diffusion-weighted MRI, dynamic Gd-enhanced MRI, MR spectroscopy, and T2-weighted MRI were performed before and 3 months after SBRT, followed by histopathologic examination. One radiation oncologist and one radiologist evaluated the detectability and image quality for the irradiated site. MRI findings of the CTI radioablation lesion was compared to electrophysiology and histopathology findings. RESULTS A total dose of 25 Gy was delivered to the CTI (median volume of 25 cc) in a single procedure according to the radiation therapy oncology group. The mean radiation dose to the heart was 7 Gy. The maximal doses (< 0.05 cc) to the left and right coronary arteries were 14 Gy and 13 Gy, respectively. EAM visualized the irradiated site and confirmed clockwise conduction block across the CTI. Gd-enhanced T1-weighted imaging could only detect the irradiated site. There were no statistical differences in the image quality of the all MR images. CONCLUSION These data demonstrated the feasibility of SBRT for creating conduction block across the CTI in mini pigs. Gd-enhanced T1-weighted imaging was essential in assessing the radioablation lesion.

Two patients with cardiac metastasis from head and neck cancer are reported. Cardiac metastasis located in the left atrium was detected on a follow-up computed tomography (CT) scan 15 months after partial glossectomy for a tongue carcinoma in a 60-year-old man. The diagnosis was confirmed as cardiac metastasis of squamous cell carcinoma (SCC) by surgical excision of the cardiac lesion. The patient died 3 weeks after surgery. In a 69-year-old man with a partial maxillectomy for primary soft palate cancer, a follow-up CT scan 5 months after surgery revealed a mass in the right atrium and ventricle, and multiple lung metastases. He died of heart failure 3 weeks after the diagnosis of cardiac metastasis. Information on these cases should add to knowledge about rarely encountered cardiac metastasis.

Summary This study examined the immediate effects of wrapped warm footbaths (WW Footbath) on the autonomic, neuroimmunological and psychological activities in healthy middle-aged volunteers. Thirteen subjects were divided into a footbath group ( n =7) and a control group ( n =6). Immediate changes in autonomic activities were recorded with wavelet analysis of heart rate variability. Salivary secretory immunoglobulin A (sIgA) and serum cortisol levels were used as neuroimmunological parameters. Psychological conditions were measured using a Visual Analog Scale. Parasympathetic activity tended to increase and sympathetic activity decrease after footbaths. Results Changes in the relaxation indices, that is, sIgA and serum cortisol levels showed that both lying down and footbath resulted in a relaxed state. Conclusion: WW Footbaths can be an effective method of relaxation, since it induces both a significant increase in parasympathetic activity and significant decrease in sympathetic activity.

In this paper, ion-implantation technique was applied to improve corrosion resistance of a newly developed La-based bulk metallic glass with poor corrosion resistance. It is found that the alloys after ion implantation with doses ranging 6 × 1016–1 × 1017 Nb/cm2 have a remarkable enhancement of corrosion resistance in chloride containing environments and acid solution with respect to the alloy without the surface treatment while the implanted alloys still have high glass forming ability. The improvement of corrosion resistance for the implanted alloys is attributed to the high passivating ability of the Nb-containing surface layer. These results obtained here clearly demonstrate that the ion-implantation technique could be a useful method to improve the corrosion resistance of bulk metallic glasses without losing glass forming ability of alloys.

Porous anodic films, with pore size of ∼10 nm, have been developed by anodizing of magnetron sputtered Ti–25 at.% Si alloy at constant formation voltages in glycerol electrolyte containing dibasic potassium phosphate at 433 K. The films, of amorphous structure, contain titanium and silicon species, as units of TiO2 and SiO2, throughout the film thicknesses, with negligible amounts of phosphorus species. The silicon is enriched in the film relative to the composition of the alloy, the level of enrichment suggesting that anion migration is increased in comparison with amorphous film growth at ambient temperature. In contrast to the behaviour of the alloy, essentially barrier films were formed on commercially pure titanium in the glycerol electrolyte, when a main anodic reaction was generation of oxygen, which was probably promoted by the development of anatase.

Epitaxial Ag and Cu films ∼ 300 nm thick on Si substrates were irradiated with self-ions (Ag + and Cu + ) at room temperature to improve crystal quality of the films. The minimum yield of Ag/Si(100) for [100] axial channeling, for example, was reduced from 39% of that for the un-irradiated sample to 13% after irradiation with 300 keV Ag ions to a fluence of 3 × 10 15 ions cm − 2 . The self-ion irradiation uniformly improves the crystal quality of the irradiated layer up to a depth of ∼ 200 nm, rather close to the depth corresponding to the end of range of ions, in spite of the non-uniform depth distribution of displaced Ag atoms. In channeling analysis, the energy dependences of dechanneling factors show that dominant defects present in the irradiated films are not dislocations, but twins, stacking faults and/or voids. AFM observations evidence grain growth in a lateral direction at the surface.

Retention of hydrogen in co-deposits formed under high-density plasma discharge in TRIAM-1M was studied. In order to quantify the retained hydrogen, material probe experiments were performed under the high-density ( n ˜ e ∼ 10 19 m - 3 ) discharges. After the exposure to the plasma, the quantitative analysis of deposition, hydrogen retention, and microscopic modification of specimens were performed by means of ion beam analysis and transmission electron microscopy. The co-deposits mainly consisted of Mo. The deposition rate of Mo was about ten times higher than that of the low-density discharge case. The hydrogen concentrations (H/Mo) retained in the co-deposits were 0.06–0.17, which was much higher than that in bulk-Mo and almost equal to the low-density case. These results indicate that as long as the co-deposition layers are continuously formed, strong wall pumping in TRIAM-1M is maintained during the discharges.

Influences of electrolyte, pre-thermal treatment and substrate composition have been examined to elucidate the mechanism of field crystallization of anodic niobia formed on magnetron-sputtered niobium. The field crystallization occurs during anodizing at 100 V in 0.1 mol dm −3 ammonium pentaborate electrolyte at 333 K, with the crystalline oxide growing more rapidly than the amorphous oxide, resulting in petal-like defects. The nucleation of crystalline oxide is accelerated by pre-thermal treatment of the niobium at 523 K in air, while vacuum treatment hinders nucleation. Notably field-crystallization is also absent in 0.1 mol dm −3 phosphoric acid electrolyte or when anodizing Nb–10at.%N and Nb–29at.%W alloys in the ammonium pentaborate electrolyte. The behaviour is explained by the role of the air-formed oxide in providing nucleation sites for field crystallization at about 25% of the thickness of the subsequently formed anodic film, the location being due to the growth mechanism of the anodic oxide and the nature of crystal nuclei. Incorporation of tungsten, nitrogen and phosphorus species to this depth suppresses the field crystallization. However, boron species occupy a relatively shallow layer and are unable to affect the nucleation sites.

In the high flux test module (HFTM) of the IFMIF, providing the required temperature control using gas-cooling and heater-heating is especially hard because of the restricted space in the very small irradiation volume of about 0.51. We have proposed an alternative design for the HFTM housing cast-like capsules. Studies of the HFTM have so far proceeded on the assumption of constant nuclear heating. Since the actual thermal control for irradiated specimens in the HFTM must be achieved with nuclear heating that has a spatially nonuniform profile, the thermal behavior of the specimens under nonuniform heating must be investigated. In this study, we described results of heat transfer experiments performed with nonuniform heating profiles and of numerical thermal-hydraulic analysis done to estimate the heater power required to achieve certain temperature levels.

The present study is directed at understanding of the influence of oxygen in the metal on anodic film growth on niobium, using sputter-deposited niobium containing from about 0–52 at.% oxygen, with anodizing carried out at high efficiency in phosphoric acid electrolyte. The findings reveal amorphous anodic niobia films, with no significant effect of oxygen on the field strength, transport numbers, mobility of impurity species and capacitance. However, since niobium is partially oxidized due to presence of oxygen in the substrate, less charge is required to form the films, hence reducing the time to reach a particular film thickness and anodizing voltage. Further, the relative thickness of film material formed at the metal/film interface is increased by the incorporation of oxygen species into the films from the substrate, with an associated altered depth of incorporation of phosphorus species into the films.

Crystalline anodic oxide films have been formed on sputter-deposited zirconium and Zr–Ti alloys in 0.1 mol dm −3 ammonium pentaborate electrolyte, with their structure, composition, dielectric properties and growth behaviour examined using X-ray diffraction, transmission electron microscopy, Rutherford backscattering spectroscopy, glow discharge optical emission spectroscopy and electrochemical impedance spectroscopy. The films formed on zirconium consist of a high-temperature stable ZrO 2 phase (cubic or tetragonal) as well as monoclinic ZrO 2 , with the latter predominant with increasing formation voltage. The incorporation of titanium species into the films stabilizes the high-temperature phase up to high voltages. Associated with the change in the crystalline structure with the incorporation of titanium species, the permittivities of the oxides increase, in agreement with the higher permittivity of bulk cubic and tetragonal ZrO 2 containing stabilizing cations compared with that of bulk monoclinic ZrO 2 . The transport number of cations during crystalline oxide growth is about 0.05, irrespective of titanium incorporation.

This paper discusses the various excitation methods of eddy current non-destructive testing (NDT). In conventional eddy current NDT, a specimen is drive by an ad or dc current. Consequently, the magnetic field generated in the specimen is aligned in a single direction. However, in order to estimate the shape or position of an unknown defect, a two-dimensional alternating magnetic flux density vector is necessary. In this paper, two-dimensional excitation methods are proposed. The magnitude and phase value are measured and analyzed to obtain information about the defect. Finally, the results of the boundary elements analysis show the availability of these methods.

The effect of co-deposition on recycling and wall pumping during long duration plasmas in TRIAM-1M has been studied. To examine the hydrogen retention on the all metal walls, material exposure experiments were carried out using an ultra-long discharge for about 72 min. After exposure to the plasma, the surface modification and hydrogen retention of the specimens were examined quantitatively by means of ion beam analysis techniques and transmission electron microscopy (TEM). Large amount of retained hydrogen were detected in the specimen exposed to the long duration discharge in TRIAM-1M. This amount was sufficient to explain the wall pumping in TRIAM-1M. A correlation was also observed between the thicknesses of the deposits and the amount of retained hydrogen. These results mean that the metallic deposited layer can trap a large amount of hydrogen and has a strong influence on hydrogen recycling similar to a carbon deposit.

The electrical conductivity of Mn a 2+ Zn b 2+ Fe c 2+ Fe 2 3+ O 4 2− (0.52⩽ a ⩽0.72, 0.20⩽ b ⩽0.43, 0.0023⩽ c ⩽0.14) single crystals was measured in the temperature range of 80–300 K. Electrical conductivity increases monotonously with the concentration of Fe 2+ ions. The activation energy for hopping conduction is 0.024–0.27 eV and shows its minimum value in the vicinity of c =0.06. Due to low carrier mobility, a small polaron effect is expected to be important at c c >0.06 suggests that the Coulomb interaction between carriers increases with the Fe 2+ ion concentration. Polaron binding energy and Coulmb interaction are considered to result in additional activation energy for hopping conduction. Thus, the electrical conduction mechanism of ferrite is understood as the result of competition between the polaron effect and electron–electron interactions.

The influence of incorporation of silicon species on the electric properties of anodic niobia, formed in 0.1 mol dm −3 ammonium pentaborate electrolyte, has been examined using sputter-deposited Nb–Si alloys containing 5 and 17 at.% silicon. The potential dependence of the capacitance of anodic niobia, originating from its n-type semiconducting properties, becomes less significant by incorporation of silicon species. In addition, the leakage current decreases with increasing silicon content in the alloy. The thermal stability of the anodic niobia is also enhanced by silicon species; the capacitance and leakage current, which increase significantly for niobium, are little influenced by annealing up to 523 K. The silicon species are incorporated in the inner 72% of the film thickness, as a consequence of immobility of the species in growing anodic niobia. The immobility of silicon species is associated with a strong Si 4+ O bond, which may also contribute to the reduction of leakage current.

Sputter-deposited TiZr alloys of various compositions have been anodized at a constant current density in 0.1 mol dm −3 ammonium pentaborate electrolyte at 298 K. The resultant anodic films have been characterized using transmission electron microscopy (TEM), glow discharge optical emission spectroscopy (GD-OES), Rutherford backscattering spectroscopy and capacitance measurements to elucidate the influence of alloy composition on their structure, growth behavior and dielectric properties. The Ti–10.5 at.% Zr alloy reveals oxygen formation within the film above ∼40 V, associated with crystallization of the anodic oxide to anatase. In contrast, amorphous anodic films, with a thin outer layer consisting of zirconium-free TiO 2 , grow up to about 250 V on Ti–23.0 at.% Zr and Ti–42.0 at.% Zr alloys at high current efficiency. Further increase in zirconium content to 62.5 at.% results in the formation of a film containing nanocrystals of monoclinic ZrO 2 phase in an amorphous matrix. The crystalline oxide is formed predominantly in the inner region of the film that is developed by anion migration inward. An anodic film composed of monoclinic ZrO 2 throughout the film thickness is formed on the zirconium. The influences of structure and composition of the anodic films on their growth behavior and dielectric properties are discussed and compared with findings for AlTa alloys, which form amorphous oxides over the entire composition range.

Barrier-type amorphous anodic films with uniform thickness grow at high current efficiency on sputter-deposited Ti–Mo alloys containing 11.5–37.0 at.% molybdenum to high voltages of more than 100 V in 0.1 mol dm −3 ammonium pentaborate electrolyte, in contrast to an amorphous-to-crystalline transition of anodic film on titanium and subsequent oxygen formation at relatively low voltages of less than 20 V. During anodizing of the alloys at a constant voltage of 80 V, the currents decrease to the order of 10 −2 A m −2 within 3 h, whereas the current for titanium decreases only to the order of 1 A m −2 , due to the presence of flaws in the film, associated with oxygen evolution. The capacitance of the anodic films formed on the Ti–11.5 at.% Mo alloy is almost comparable to that formed on tantalum at the same voltage. The increase in molybdenum content in the alloy results in a slight decrease in the capacitance of the films. From these results, the structure of anodic films on titanium can be modified by incorporation of molybdenum species from the substrate so that uniform amorphous anodic films with a relatively high capacitance and a low defect density have been obtained.

Sputter-deposited niobium, and Nb 90 N 10 , Nb 83 N 17 and Nb 60 N 40 alloys, have been anodized at 50 A m −2 in 0.1 mol dm −3 ammonium pentaborate electrolyte at 293 K and resultant amorphous anodic films have been characterized by transmission electron microscopy, glow discharge optical emission spectroscopy, Rutherford backscattering spectrometry and Fourier-transform, infra-red spectroscopy. Except for the Nb 60 N 40 alloy, which shows a breakdown at approximately 60 V, the deposited layers reveal a linear voltage increase to more than 150 V, with the rate decreasing with the niobium content. Additionally, anodic films, with flat and parallel metal/film and film/electrolyte interfaces, are formed on the specimens with the formation ratio decreasing with increasing nitrogen content in the deposited films. Nitrogen is incorporated into the inner ∼70–75% of the film thickness as N 2 O molecules, forming fine bubbles, with typical sizes up to 10 nm, in a Nb 2 O 5 -based matrix material. The remaining 25–30% of the film comprises a layer of Nb 2 O 5 with the outer regions containing boron species derived from the electrolyte. Release of high pressure N 2 O gas is associated with the relatively low breakdown voltage for the Nb 60 N 40 alloy of highest nitrogen content. The two-layered nature of the anodic films arises from the film growth mechanism that involves outward migration of niobium species and inward migration of oxygen species; in contrast nitrogen species are immobile due either to the relatively high energy of the NO bond or to their presence in bubbles.

The microsurgical anatomy of the lateral ventricles was examined in cadaveric cerebral hemispheres. The neural, arterial and venous structures in the wall of the lateral ventricles, the relationships of the lateral ventricles to the velum interpositum and third ventricle were examined. The relationships of the choroidal fissure and basal cisterns were also examined. The operative approaches to the lateral ventricles are reviewed and several clinical cases are presented.

TiMo, bcc, solid-solution alloys, containing 11.5–37.0 at.% molybdenum, have been anodised galvanostatically in 0.1 mol dm −3 ammonium pentaborate and 1.0 mol dm −3 phosphoric acid electrolytes, with resultant anodic films characterised by scanning electron microscopy, transmission electron microscopy, Rutherford backscattering spectroscopy and glow discharge optical emission spectroscopy. Uniform amorphous films are formed at high current efficiency to >100 V, with formation ratios of 2.3 and 2.2 nm V −1 in the respective electrolytes, contrasting with the amorphous-to-crystalline transition of anodic titania on titanium that occurs at ∼20–50 V. Apart from minor incorporation of electrolyte species, the films comprise an outer layer of TiO 2 and an inner oxide layer containing Ti 4+ and Mo 6+ ions. The films grow by migration of both cations and anions, with Ti 4+ ions migrating faster than Mo 6+ ions that is related to the energies of Ti 4+ O and Mo 6+ O bonds.

Exact expressions of the Pauli exclusion operator Q in the nuclear matter calculation are presented in detail. Exact formulae are also given for the calculations of the single-particle-potential energy and the binding energy per nucleon with the exact Q operator. Numerical calculations of the G matrix in the lowest-order Brueckner theory are carried out to check the reliability of the standard angle-average approximation for the Q operator by employing the Bonn B and C NN potentials. It is observed that the exact treatment of the operator Q brings about non-negligible and attractive contributions to the binding energy., 16 pages, 3 figures

A method for the simultaneous determination of bile acids in rat liver tissue by high-performance liquid chromatography was developed. Without prior fractionation and alkaline hydrolysis, 30 unconjugated, glycine- and taurine-conjugated bile acids were detected by post-column enzymatic reaction and fluorescence detection. They were separated on a reversed-phase column using a linear gradient solvent system of 10 mM tribasic ammonium phosphate-acetonitrile-methanol (44:12:5, v/v/v) and 20 mM dibasic ammonium phosphate-acetonitrile-methanol (2:1:2, v/v/v). The limits of detection were 1-5 pmol, and calibration curves were linear for concentrations ranging between 10 and 4000 pmol per 10 microl injection. This rapid and reliable method is effective for measuring bile acid levels in liver tissue not only of rats but also of patients with hepatobiliary and other diseases.

To investigate the nature of extraocular pseudoexfoliative (PSX) material, and to validate the hypothesis that the PSX syndrome is a systemic disorder, we studied the immunoreactivity of intraocular and extraocular PSX material from patients with the PSX syndrome using antibodies against proteins of extracellular matrices. Surgical specimens of four different tissues were obtained from human eyes with the PSX syndrome: nine trabecular tissues, three cataractous lenses, six bulbar conjunctivas, and seven lid skins. These tissues were processed for electron microscopic immunohistochemistry, and stained with antibodies against vitronectin, fibronectin, laminin, and elastin, by an indirect immunogold procedure. Density of the gold particles located on the PSX material was estimated by video image analysis. Statistical analysis of the data revealed that the PSX material from trabecular tissues, lenses, bulbar conjunctivas, and lid skins had almost identical immunoreactivity to the antibodies studied. PSX materials of trabecular tissues, lenses, bulbar conjunctivas, and lid skins were found to have not only a similar ultrastructure, but also almost identical immunohistochemical characteristics. These results support the hypothesis that the PSX syndrome is a systemic disorder.

The effect of ion irradiation on cluster-like Sn films grown on a crystalline Si substrate was studied by scanning electron microscopy (SEM) and Rutherford backscattering spectrometry combined with channelling (RBS/C). It was established from SEM observations that ion-beam irradiation causes a morphological change in the cluster-like Sn films; the Sn particles wet the substrate and coalesce on ion irradiation. In order to characterize the Sn/Si interface, RBS/C measurements were performed to investigate the correlation between the Sn/Si interfacial structure and the morphology of the Sn films on the Si substrate. It was revealed that intermixing between the Sn film and the substrate and the segregation of Si atoms may be responsible for the reduction in the interfacial and surface free energies respectively, which results in the morphological transition from a three-dimensional cluster-like film to a uniform film.

Nitrogen ions (N 2 + ) with energy 62 keV were implanted into 100 nm thick Ti films evaporated onto thermally cleaned NaCl substrates. Unimplanted and N-implanted Ti films were examined by transmission electron microscopy, Rutherford backscattering spectrometry and elastic recoil detection analysis. It was revealed that N-implantation expands the h.c.p. Ti lattice and reduces the hydrogen concentration in the evaporated Ti film. The former induces the h.c.p.-f.c.c. transformation and then leads to the growth of (001) oriented TiN y by occupation of the octahedral sites in the f.c.c. Ti sublattice by N. The latter indicates the escape of H from TiH x , and leads to the growth of (110) oriented TiN y , by the similar occupation by N.

Ion beam assisted electron cyclotron resonance plasma CVD (IB-PCVD) equipment was developed. Plasma was produced by a coaxial ECR discharge. A bucket-type ion source with a microwave plasma (MP) cathode was used as an ion source. Amorphous SiO 2 films were deposited on austenitic-type stainless steel and silicon wafer substrates by use of the IB-PCVD equipment. The effects of the gas flow of monosilane, carbon dioxide and hydrogen and oxygen ion energies have been studied in the relation to composition, structure, corrosion properties and oxidation protection potential of the films. The surface morphology was observed by scanning electron microscopy. Auger spectroscopy, X-ray photoelectron spectroscopy and Fourier transform IR were used to characterize films and interface. The corrosion protection potential in an aqueous environment was evaluated by electrochemical techniques. Oxidation behaviour in the atmosphere in an oven was studied at 1000 °C. Surfaces of the films were smooth, and grain structure was not clear. These films had good corrosion protection. Oxidation of steel substrate was suppressed by the SiO 2 coating. Oxygen irradiation during deposition was effective to improve corrosion and oxidation protection.

Fe/M (M = Ag, Sn) multilayer films have been prepared by a vacuum evaporation method. RBS is performed to examine the depth profile of the multilayer films. For M = Ag, a layer structure with a well defined interface is formed by the present evaporation method. Mossbauer spectroscopy as well as XRD shows that the Fe in the multilayer is in an α-Fe state. For M = Sn, RBS showed that a considerable mixing had taken place between Fe and Sn during the multilayer procedure.

Thin titanium nitride (TiN) films of 40 and 70 nm in thickness were deposited on austenitic-type 304 stainless steel substrates by a rf ion plating process, and these specimens were irradiated with 70 kV titanium ions at a fluence of 1 × 10 17 /cm 2 by use of MEVVA IV metallic ion source at room temperature. After that TiN films of 2 μm were deposited by the same method. The results of X-ray photoelectron spectroscopy and Auger electron spectroscopy revealed that implanted titanium penetrated into the substrate and interfacial mixing was verified. The adhesion strength was estimated by a scratch test. It was found that ion implantation can enhance the adhesion strength between the film and the substrate. The corrosion resistance of the specimens was evaluated in aqueous solutions of sulfuric acid by an electrochemical method. Titanium implantation was extremely effective in suppressing the anodic dissolution of stainless steel.

This study provides valuable insights into the functions of the lysine residue that forms an internal aldimine with pyridoxal phosphate in the beta subunit of tryptophan synthase from Salmonella typhimurium. Our spectroscopic and kinetic studies demonstrate that a mutant alpha 2 beta 2 complex having beta subunit lysine 87 replaced by threonine forms external aldimines with several amino acids including L-serine, beta-chloro-1-alanine, L-tryptophan, and D-tryptophan. Because the rates of aldimine formation are very slow, we conclude that one role of lysine 87 in the wild type enzyme is to facilitate formation of external aldimines by transimination. Lysine 87 is an essential catalytic residue because the mutant alpha 2 beta 2 complex has no measurable activity in reactions catalyzed by the beta subunit and does not convert external aldimines to products. The mutant enzyme carries out two slow partial beta-elimination reactions: the conversion of beta-chloro-L-alanine and L-serine to enzyme-bound aminoacrylate. The reaction with L-serine is catalyzed by ammonia, which partially replaces the deleted epsilon-amino group. Lysine 87 is important for substrate and product release because L-serine, L-tryptophan, and aminoacrylate dissociate very slowly from the mutant alpha 2 beta 2 complex. Our ability to prepare very stable derivatives of the mutant alpha 2 beta 2 complex containing tightly bound aldimines with a substrate, a product, or a reaction intermediate provides valuable materials for ongoing x-ray crystallographic investigations and future kinetic analyses of the allosteric activation of the alpha subunit by beta subunit ligands.