Location of β-emitting12N in V crystal following recoil implantation

Nuclear dipolar broadening in the NMR spectra of β-emitting¹²N implanted in single crystal V was studied as a function of external magnetic field, orientation of the crystal axes relative to the field, and temperature of the sample. The implanted¹²N was located in an interstitial tetrahedral site. The surrounding V atoms nearest to the¹²N were displaced from the regular lattice position; the lattice expansion of large size Δa/a=0.5 was determined.     

Continuous screening of analytical parameters facilitates efficient development of HPLC methods required for impurity profiling

Developing a robust analytical HPLC–UV method to characterize a drug candidate during an early stage of development is a major challenge when not all impurity standards are available. Here, we report our efforts to devise an efficient strategy for HPLC method development using continuous screening of analytical parameters without impurity standards. This strategy uses small incremental changes in the mobile phase pH and column temperature to trace each impurity on an overlay chromatogram. We tested this method using benzocaine as the active pharmaceutical ingredient (API), and compounds with similar structures to represent unknown impurities. Despite the coelution of peaks, results identified the number of impurities and indicated the starting point and parameter variables of the ensuing optimization step. Further, we demonstrated that the retention time of each peak as a function of mobile phase pH accounts for the apparent pK_a of known and unknown compounds in the presence of an organic solvent. This information is critically important to the selection of a robust pH range for HPLC methods.     

Spin-lattice relaxation of 25Al and 28P in Pt

The spin-lattice relaxation times T ₁ for short-lived β emitters ²⁵Al(I?=?5/2, T _1/2?= 7.2 s) and ²⁸P(I?=?3, T _1/2?= 270 ms) in Pt were measured by means of the β-NMR technique. As a result, T ₁[²⁵Al in Pt] = (1.1 $^{+\ 0.7}_{-\ 0.3})$ s and T ₁[²⁸P in Pt] >0.5 s were obtained at temperatures of 17 and 20 K, respectively. The Knight shifts were estimated from the Korringa relation, which were evaluated by comparing to the first principle calculations.     

Evaluation of protein-ligand binding free energy focused on its entropic components

The binding free energy for FK506-binding protein-ligand systems is evaluated as a sum of two entropic components, the water-entropy gain, and the configurational-entropy loss for the protein and ligand molecules upon the binding. The two entropic components are calculated using morphometric thermodynamics combined with a statistical-mechanical theory for molecular liquids and the normal mode analysis, respectively. We find that there is an excellent correlation between the calculated and experimental values of the binding free energy. This result is compared with those of several other binding-free energy calculation methods, including MM-PB/SA. The binding can well be elucidated by competition of the two entropic components. Upon the protein-ligand binding, the total volume available to the translational displacement of the coexisting water molecules increases, leading to an increase in the number of accessible configurations of the water. The water-entropy gain, by which the binding is driven, originates primarily from this effect. This study sheds new light on the theoretical prediction of the protein-ligand binding free energy.     

Two-Photon Laser-Induced Fluorescence Spectra of Argon in a Grimm-Style Glow Discharge Tube

Two-photon excited laser-induced fluorescence (LIF) spectra of argon atom were successfully observed in a Grimm-style glow discharge tube, which has widely been applied to depth profiling of the elemental composition on various film-like samples by emission spectrometry. The LIF signal of an argon atomic line at 641.63 nm was observed when the glow discharge argon plasma was illuminated by a pulsed Ti:sapphire laser radiation of 7–10 mJ/pulse at 753.39 or 795.66 nm without focusing of the laser beam.     

Creation of polarized ultracold neutrons and observation of Ramsey resonance for electric dipole moment measurement

Polarized UCNs have been created by selecting only one spin state passing through a magnetized Fe foil. Typical degree of polarization was about 90 %. The polarization relaxation time in the prototype Ramsey cell was $T_1 =1100^{+800}_{-400}(Nd,Pr)-(Tb,Dy,Gd)-(Fe,Co,Al,Cu)-B magnets were heat treated in two different ways and investigated in the temperature range 4.2 to 400 K. After optimal heat treatment intrinsic coercive field _i H _c?= 1640 and 5040 kA/m for room temperature and 10 K was obtained and the temperature coefficient of remanence α?=??0.01 for temperature range 80 to 375 K was found. On basis of magnetic measurements and ⁵⁷Fe Mössbauer spectroscopy, the possible reasons for the increase of _i H _c during multi-step heat treatment are discussed.     

Generation of soft x-ray and water window harmonics using a few-cycle, phase-locked, optical parametric chirped-pulse amplifier

Multimillijoule, few-cycle, carrier-envelope-phase (CEP)-locked, near-IR pulses at 750 nm from an optical parametric chirped-pulse amplifier are applied to the generation of CEP-dependent, soft x-ray high harmonics around the boron K-edge at 188 eV. The dependence on the CEP manifests the phase coherence of high harmonics preserved in the highest-photon energy ever reported. Multimillijoule optical pulses also allow the extension of the cutoff energy up to 325 eV, exceeding the carbon K-edge of the water window. However, in this spectral range, the CEP dependence of harmonic spectra is not observed, suggesting the degradation of temporal coherence due to the heavy ionization of helium atoms.     

6‐[3‐Hydroxy‐17‐oxoestra‐1,3,5(10)‐trien‐7β‐yl]­hexane­nitrile

In the title compound, C₂₄H₃₁NO₂, ring B adopts a conformation between the boat and twisted‐boat forms. This conformation best accommodates adverse intramolecular H⋯H interactions between the H atoms of the 7β‐substituent and the two nearest ring H atoms. The tilt angle between rings A and D is 28.6 (1)°.     

Synthesis of Nonsymmetric Divinylarenes by a Heck/Wittig Reaction Combination

A protocol for a one-pot Heck reaction/Wittig olefination to divinylarenes has been developed.