Exploiting Polarization Wobble in Sinuous Antennas for the Detection of Linear Scatterers in Ground Penetrating Radar Applications.
Abstract not provided.
Crocker, Dylan Andrew↗
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First Observation of Multiple Transverse Wobbling Bands of Different Kinds in 183 Au
Here, we report the first observation of two wobbling bands in 183 Au, both of which were interpreted as the transverse wobbling (TW) band but with different behavior of their wobbling energies as a function of spin. It increases (decreases) with spin for the positive (negative) parity configuration. The crucial evidence for the wobbling nature of the bands, dominance of the $\textit{E}$2 component in the Δ$\textit{I}$ = 1 transitions between the partner bands, is provided by the simultaneous measurements of directional correlation from the oriented states ratio and the linear polarization of the $\textit{γ}$ rays. Particle rotor model calculations with triaxial deformation reproduce the experimental data well. A value of spin, $I_m$, has been determined for the observed TW bands below which the wobbling energy increases and above which it decreases with spin. The nucleus 183 Au is, so far, the only nucleus in which both the increasing and the decreasing parts are observed and thus gives the experimental evidence of the complete transverse wobbling phenomenon.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Dynamic Influence of Spindle Wobble in a Lathe on the Workpiece Geometry
The influence of spindle wobble in a lathe on the geometry of the machined surface is not direct. The intermediate stages involve conversion of the wobble to forces and elastic deformations. Together with the elastic deformation, wobble modifies the shaping trajectories, which are mainly responsible for the geometry of the final product. Wobble induces periodic variation in the parameters of the dynamic system. It leads not only to parametric self-excitation but also, in a nonlinear dynamic system, to the formation of various attractive deformational-displacement sets. The present work is devoted to mathematical modeling of the influence of wobble on the workpiece geometry. Cases in which various types of attractive sets are formed in the system (such as limit cycles, invariant tori, and chaotic attractors) are considered.
42 ENGINEERING↗
Influence of Spindle Wobble in Turning on the Workpiece’s Surface Topology
The shaping trajectory of the cutting tool relative to the workpiece consists of the trajectories of the machine tool’s working components, trajectories unrelated to control of perturbations (including spindle wobble), and deformational-displacement trajectories of the tool and workpiece relative to the supporting system. In the present work, the perturbation considered is wobble, which depends on the precision and state of the machine tool. Spindle wobble in a lathe leads to the formation of various attractive sets associated with deformational displacement of the tool. The result is to change the shaping trajectory. That affects the geometric topology of the machined surface, which depends not only on the shaping motion but also on independent processes that accompany cutting, such as plastic deformation, thermodynamic phenomena, and dissipative structures formed in the cutting zone. The present work examines how the attractive sets associated with the deformational displacement produced by spindle wobble are related to the surface topology. The contribution of the wobble to the surface topology is assessed.
42 ENGINEERING↗
Influence of Spindle Wobble in a Lathe on the Tool’s Deformational-Displacement Trajectory
Attention focuses here on the conversion of the trajectory of spindle-group wobble in a lathe into deformational displacement of the tool and the associated modification of the shaping trajectory. This process depends on the change in dynamic properties of the system due to the wobble. On the basis of simulation and digital experiments, it may be concluded that the wobble changes the stability of the trajectories and that various attractive sets are formed in the system (such as limit cycles, invariant tori, and chaotic attractors). The wobble does not change the shaping trajectory directly, but rather through the formation of attractive deformational-displacement sets. Therefore, the attractive sets affect the geometric topology of the workpiece surface and the limiting feasible manufacturing precision.
42 ENGINEERING↗
Evidence against the wobbling nature of low-spin bands in 135 Pr
The electromagnetic character of the ΔI=1 transitions connecting the 1- to 0-phonon and the 2- to 1-phonon wobbling bands should be dominated by an E2 component, due to the collective motion of the entire nuclear charge. In the present work it is shown, based on combined angular correlation and linear polarization measurements, that the mixing ratios of all analyzed connecting transitions between low-lying bands in 135 Pr interpreted as 0-, 1-, and 2-phonon wobbling bands, have absolute values smaller than one. This indicates predominant M1 magnetic character, which is incompatible with the proposed wobbling nature. All experimental observables are instead in good agreement with quasiparticle-plus-triaxial-rotor model calculations, which describe the bands as resulting from a rapid re-alignment of the total angular momentum from the short to the intermediate nuclear axis
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Identification and codon reading properties of 5-cyanomethyl uridine, a new modified nucleoside found in the anticodon wobble position of mutant haloarchaeal isoleucine tRNAs
Most archaea and bacteria use a modified C in the anticodon wobble position of isoleucine tRNA to base pair with A but not with G of the mRNA. This allows the tRNA to read the isoleucine codon AUA without also reading the methionine codon AUG. To understand why a modified C, and not U or modified U, is used to base pair with A, we mutated the C34 in the anticodon of Haloarcula marismortui isoleucine tRNA (tRNA2 Ile) to U, expressed the mutant tRNA in Haloferax volcanii, and purified and analyzed the tRNA. Ribosome binding experiments show that although the wild-type tRNA2 Ile binds exclusively to the isoleucine codon AUA, the mutant tRNA binds not only to AUA but also to AUU, another isoleucine codon, and to AUG, a methionine codon. The G34 to U mutant in the anticodon of another H. marismortui isoleucine tRNA species showed similar codon binding properties. Binding of the mutant tRNA to AUG could lead to misreading of the AUG codon and insertion of isoleucine in place of methionine. This result would explain why most archaea and bacteria do not normally use U or a modified U in the anticodon wobble position of isoleucine tRNA for reading the codon AUA. Biochemical and mass spectrometric analyses of the mutant tRNAs have led to the discovery of a new modified nucleoside, 5-cyanomethyl U in the anticodon wobble position of the mutant tRNAs. 5-Cyanomethyl U is present in total tRNAs from euryarchaea but not in crenarchaea, eubacteria, or eukaryotes.
5-cyanomethyl uridine↗
Ribosome Structure Reveals Preservation of Active Sites in the Presence of a P-Site Wobble Mismatch
Translation initiation in the P site occasionally occurs at atypical (non-AUG) start codons, including those forming a mismatch in the third (wobble) position. During elongation, however, a pyrimidine-pyrimidine wobble mismatch may trigger a translation quality-control mechanism, whereby the P-site mismatch is thought to perturb the downstream A-site codon or the decoding center, thereby reducing translation fidelity and inducing termination of aberrant translation. We report a crystal structure of the 70S initiation complex containing an AUC codon in the ribosomal P site. Remarkably, the ribosome stabilizes the mismatched codon-anticodon helix, arranging a normally disruptive cytosine-cytosine pair into a Watson-Crick-like conformation. Here, the translation-competent conformations of the tRNA, mRNA, and decoding center suggest that a P-site wobble-position mismatch in the 70S initiation complex does not pre-arrange the mRNA or decoding center to favor subsequent miscoding events.
59 BASIC BIOLOGICAL SCIENCES↗
Longitudinal Wobbling Motion in Au 187
The rare phenomenon of nuclear wobbling motion has been investigated in the nucleus 187Au. A longitudinal wobbling-bands pair has been identified and clearly distinguished from the associated signature-partner band on the basis of angular distribution measurements. Theoretical calculations in the framework of the particle rotor model are found to agree well with the experimental observations. This is the first experimental evidence for longitudinal wobbling bands where the expected signature partner band has also been identified, and establishes this exotic collective mode as a general phenomenon over the nuclear chart.
150 ≤ A ≤ 189↗
SU-E-T-594: Out-Of-Field Neutron and Gamma Dose Estimated Using TLD-600/700 Pairs in the Wobbling Proton Therapy System
Purpose: Secondary fast neutrons and gamma rays are mainly produced due to the interaction of the primary proton beam with the beam delivery nozzle. These secondary radiation dose to patients and radiation workers are unwanted. The purpose of this study is to estimate the neutron and gamma dose equivalent out of the treatment volume during the wobbling proton therapy system. Methods: Two types of thermoluminescent (TL) dosimeters, TLD-600 ({sup 6}LiF: Mg, Ti) and TLD-700 ({sup 7}LiF: Mg, Ti) were used in this study. They were calibrated in the standard neutron and gamma sources at National Standards Laboratory. Annealing procedure is 400°C for 1 hour, 100°C for 2 hours and spontaneously cooling down to the room temperature in a programmable oven. Two-peak method (a kind of glow curve analysis technique) was used to evaluate the TL response corresponding to the neutron and gamma dose. The TLD pairs were placed outside the treatment field at the neutron-gamma mixed field with 190-MeV proton beam produced by the wobbling system through the polyethylene plate phantom. The results of TLD measurement were compared to the Monte Carlo simulation. Results: The initial experiment results of calculated dose equivalents are 0.63, 0.38, 0.21 and 0.13 mSv per Gy outside the field at the distance of 50, 100, 150 and 200 cm. Conclusion: The TLD-600 and TLD-700 pairs are convenient to estimate neutron and gamma dosimetry during proton therapy. However, an accurate and suitable glow curve analysis technique is necessary. During the wobbling system proton therapy, our results showed that the neutron and gamma doses outside the treatment field are noticeable. This study was supported by the grants from the Chang Gung Memorial Hospital (CMRPD1C0682)
61 RADIATION PROTECTION AND DOSIMETRY↗
Human tRNA Lys3 UUU Is Pre-Structured by Natural Modifications for Cognate and Wobble Codon Binding through Keto-Enol Tautomerism
Human tRNA Lys3 UUU (htRNA Lys3 UUU ) decodes the lysine codons AAA and AAG during translation and also plays a crucial role as the primer for HIV-1 (human immunodeficiency virus type 1) reverse transcription. The posttranscriptional modifications 5-methoxycarbonylmethyl-2-thiouridine (mcm 5 s 2 U 34 ), 2-methylthio-N 6 -threonylcarbamoyladenosine (ms 2 t 6 A 37 ), and pseudouridine (Ψ 39 ) in the tRNA's anticodon domain are critical for ribosomal binding and HIV-1 reverse transcription. To understand the importance of modified nucleoside contributions, we determined the structure and function of this tRNA's anticodon stem and loop (ASL) domain with these modifications at positions 34, 37, and 39, respectively (hASL Lys3 UUU -mcm 5 s 2 U 34 ;ms 2 t 6 A 37 ;Ψ 39 ). Ribosome binding assays in vitro revealed that the hASL Lys3 UUU -mcm 5 s 2 U 34 ;ms 2 t 6 A 37 ;Ψ 39 bound AAA and AAG codons, whereas binding of the unmodified ASL Lys3 UUU was barely detectable. The UV hyperchromicity, the circular dichroism, and the structural analyses indicated that Ψ 39 enhanced the thermodynamic stability of the ASL through base stacking while ms 2 t 6 A 37 restrained the anticodon to adopt an open loop conformation that is required for ribosomal binding. The NMR-restrained molecular-dynamics-derived solution structure revealed that the modifications provided an open, ordered loop for codon binding. The crystal structures of the hASL Lys3 UUU -mcm 5 s 2 U 34 ;ms 2 t 6 A 37 ;Ψ 39 bound to the 30S ribosomal subunit with each codon in the A site showed that the modified nucleotides mcm 5 s 2 U 34 and ms 2 t 6 A 37 participate in the stability of the anticodon–codon interaction. Importantly, the mcm 5 s 2 U 34 ·G 3 wobble base pair is in the Watson–Crick geometry, requiring unusual hydrogen bonding to G in which mcm 5 s 2 U 34 must shift from the keto to the enol form. The results unambiguously demonstrate that modifications pre-structure the anticodon as a key prerequisite for efficient and accurate recognition of cognate and wobble codons.
Vendeix, Franck A.P.↗
Two-phonon wobbling in 135 Pr
The second-phonon (n ω = 2) wobbling band has been established in the nucleus 135 Pr. Conclusive evidence for its wobbling nature comes from the ΔI = 1, E2 character of the transitions between the new band and the previously identified transverse wobbler band (n ω = 1) in this nucleus. Theoretical calculations in the framework of the quasiparticle triaxial rotor and triaxial projected shell models are found to be in good agreement with the experimental results.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Evolution of chirality from transverse wobbling in 135 Pr
Chirality is a distinct signature that characterizes triaxial shapes in nuclei. We report the first observation of chirality in the nucleus 135 Pr using a high-statistics Gammasphere experiment with the 123 Sb( 16 O, 4n) 135 Pr reaction. Two chiral-partner bands with the configuration π(1h11/2 )1 ⊗ ν(1h 11/2 ) −2 have been identified in this nucleus. Angular distribution analyses of the ΔI = 1 transitions connecting the two bands reveal a dominant dipole character, and quasiparticle triaxial rotor model calculations show good agreement with the data. Since the simultaneous observation of chirality and transverse wobbling in 135 Pr relies critically on these angular distribution results, we also address and refute the experimental and theoretical criticisms raised in a recent work by Lv et al., presenting additional evidence that further strengthens our interpretation. Furthermore, this marks the first observation of both hallmarks of triaxiality—chirality and wobbling—in the same nucleus.
90 ≤ A ≤ 149↗
Transverse wobbling in an even-even nucleus
Two new bands built on the two-quasiparticle $π(h_{11/2})^2$ configuration of the even-even nucleus 130 Ba are investigated using constrained triaxial covariant density functional theory combined with quantum particle rotor model calculations. The energy difference between the two bands, as well as the available electromagnetic transition probabilities $B(M1)_{\text{out}}/B(E2)_{\text{in}}$ and $B(E2)_{\text{out}}/B(E2)_{\text{in}}$, are well reproduced. In this work, the analysis of the angular momentum geometry reveals that the higher band represents transverse wobbling motion of a two-quasiparticle configuration. This is the first example of two-quasiparticle wobbling bands in an even-even nucleus.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Possible wobbling phenomenon in 125 Xe
In the present paper, negative-parity bands based on the νh 11/2 configuration in 125 Xe have been revisited. This nucleus was populated through the reaction 82 Se( 48 Ca, 5n) 125 Xe at a beam energy of 205 MeV and the corresponding γ rays were observed using the Gammasphere spectrometer. Evidence for first and second phonon wobbling excitations has been established by measurements of directional correlation ratios and angular distributions of the involved γ rays. Here, the observed wobbling energy of the bands involved were compared with the recently published results obtained within the framework of triaxial projected shell-model calculations.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Two-Dimensional Collective Hamiltonian for Chiral and Wobbling Modes
Here, a two-dimensional collective Hamiltonian (2DCH) on both azimuth and polar motions in triaxial nuclei is proposed to investigate the chiral and wobbling modes. In the 2DCH, the collective potential and the mass parameters are determined from three-dimensional tilted axis cranking (TAC) calculations. The broken chiral and signature symmetries in the TAC solutions are restored by the 2DCH. The validity of the 2DCH is illustrated with a triaxial rotor (γ= -30°) coupling to one h 11/2 proton particle and one h 11/2 neutron hole. By diagonalizing the 2DCH, the angular momenta and energy spectra are obtained. These results agree with the exact solutions of the particle rotor model (PRM) at high rotational frequencies. However, at low frequencies, the energies given by the 2DCH are larger than those by the PRM due to the underestimation of the mass parameters. In addition, with increasing angular momentum, the transitions from the chiral vibration to chiral rotation and further to longitudinal wobbling motion have been presented in the 2DCH.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Comment on “Stability of the wobbling motion in an odd-mass nucleus and the analysis of Pr 135 ”
The claim here is that transverse wobbling is unstable is contradicted. Examples for stable transverse wobbling are provided. It is demonstrated that the alternative scenario suggested in the commented paper violates fundamental properties of the nuclear many-body system.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
SU-E-T-666: Radionuclides and Activity of the Patient Apertures Used in a Proton Beam of Wobbling System
Purpose: To identify the radionuclides and quantify the activity of the patient apertures used in a 190-MeV proton beam of wobbling system. Methods: A proton beam of wobbling system in the first proton center in Taiwan, Chang Gung Memorial Hospital at Linkou, was used to bombard the patient apertures. The patient aperture was composed of 60.5 % copper, 39.4 % Zinc, 0.05 % iron, 0.05 % lead. A protable high-purity germanium (HPGe) coaxial detector was used to measure the spectra of the induced nuclides of patient apertures. The analysis of the spectra and the identification of the radionuclides were preliminarily operated by the Nuclide Navigator III Master Library. On the basis of the results by Nuclide Navigator III Master Library, we manually selected the reliable nuclides by the gamma-ray energies, branching ratio, and half life. In the spectra, we can quantify the activity of radionuclides by the Monte Carlo efficiency transfer method. Results: In this study, the radioisotopes activated in patient apertures by the 190-MeV proton beam were divided into two categories. The first category is long half-life radionuclides, such as Co-56 (half life, 77.3 days). Other radionuclides of Cu-60, Cu-61, Cu-62, Cu-66, and Zn-62 have shorter half life. The radionuclide of Cu-60 had the highest activity. From calculation with the efficiency transfer method, the deviations between the computed results and the measured efficiencies were mostly within 10%. Conclusion: To identify the radionuclides and quantify the activity helps us to estimate proper time intervals for cooling the patient apertures. This study was supported by the grants from the Chang Gung Memorial Hospital (CMRPD1C0682)
07 ISOTOPE AND RADIATION SOURCES↗