Ultracold field-linked tetratomic molecules.

Ultracold polyatomic molecules offer opportunities1 in cold chemistry2,3, precision measurements4 and quantum information processing5,6, because of their rich internal structure. However, their increased complexity compared with diatomic molecules presents a challenge in using conventional cooling techniques. Here we demonstrate an approach to create weakly bound ultracold polyatomic molecules by electroassociation7 (F.D. et al., manuscript in preparation) in a degenerate Fermi gas of microwave-dressed polar molecules through a field-linked resonance8-11. Starting from ground-state NaK molecules, we create around 1.1 × 103 weakly bound tetratomic (NaK)2 molecules, with a phase space density of 0.040(3) at a temperature of 134(3) nK, more than 3,000 times colder than previously realized tetratomic molecules12. We observe a maximum tetramer lifetime of 8(2) ms in free space without a notable change in the presence of an optical dipole trap, indicating that these tetramers are collisionally stable. Moreover, we directly image the dissociated tetramers through microwave-field modulation to probe the anisotropy of their wavefunction in momentum space. Our result demonstrates a universal tool for assembling weakly bound ultracold polyatomic molecules from smaller polar molecules, which is a crucial step towards Bose-Einstein condensation of polyatomic molecules and towards a new crossover from a dipolar Bardeen-Cooper-Schrieffer superfluid13-15 to a Bose-Einstein condensation of tetramers. Moreover, the long-lived field-linked state provides an ideal starting point for deterministic optical transfer to deeply bound tetramer states16-18.

Reconstruction of lower limb defect with a variant sural neuro-fasciocutaneous flap: A case report.

INTRODUCTION: The sural neuro-fasciocutaneous flap is widely used for reconstructing skin defects in the lower calf. Variations of the sural nerve in the calf are infrequent, which may require a variation in the traditional surgical procedure. CASE PRESENTATION: A 76-year-old male patient had soft tissue defect of the right lateral ankle and lower leg caused by an accident 18 years ago. He had exposed bones and had osteomyelitis. He underwent two primary operations, and finally, we used a sural neuro-fasciocutaneous flap to effectively cover the defect. We observed that the course of the sural nerve was atypical during the surgery, and we adjusted the flap axis laterally to bring the lateral sural cutaneous nerve inside the flap to improve the success rate of the surgery. The flap entirely survived, and there was no sensory impairment in the calf. The patient was discharged from the hospital after 10 days. CLINICAL DISCUSSION: Some type of variant of the sural nerve makes the flap harvest without the neurovascular component of the sural nerve and the cutaneous chain, which might decrease flap survival. Moving the flap axis laterally and bringing in the lateral sural nerve or peroneal communicating nerve offers an adequate blood supply to the vascular territory and the flap region. CONCLUSION: In patients with sural nerve variants, the procedure does not have to follow the traditional theory of the sural neuro-fasciocutaneous flap. Preoperative and intraoperative protection of the sural nerve variant should also be considered.

Effective Potential and Superfluidity of Microwave-Shielded Polar Molecules.

We analytically show that the effective interaction potential between microwave-shielded polar molecules consists of an anisotropic van der Waals-like shielding core and a modified dipolar interaction. This effective potential is validated by comparing its scattering cross sections with those calculated using intermolecular potential involving all interaction channels. It is shown that a scattering resonance can be induced under microwave fields reachable in current experiments. With the effective potential, we further study the Bardeen-Cooper-Schrieffer pairing in the microwave-shielded NaK gas. We show that the superfluid critical temperature is drastically enhanced near the resonance. As the effective potential is suitable for exploring the many-body physics of molecular gases, our results pave the way for studies of the ultracold gases of microwave-shielded molecular gases.