Novel orientational ordering and reentrant metallicity in K(x)C(60) monolayers for 3 < or = x < or = 5.

STM studies on K(x)C(60) monolayers reveal new behavior over a wide range of the phase diagram. As x increases from 3 to 5 K(x)C(60) monolayers undergo metal-insulator-metal reentrant phase transitions and exhibit a variety of novel orientational orderings, including a complex 7-molecule, pinwheel-like structure. The proposed driving mechanism for the orientational ordering is the lowering of electron kinetic energy by maximizing the overlap of neighboring molecular orbitals. In insulating (metallic) K(x)C(60) this gives rise to orbital versions of the superexchange (double-exchange) interaction.

Visualization of the molecular Jahn-Teller effect in an insulating K4C60 monolayer.

We present a low-temperature scanning tunneling microscopy (STM) study of K(x)C60 monolayers on Au(111) for 3 < or = x < or = 4. The STM spectrum evolves from one that is characteristic of a metal at x = 3 to one that is characteristic of an insulator at x = 4. This electronic transition is accompanied by a dramatic structural rearrangement of the C60 molecules. The Jahn-Teller effect, a charge-induced mechanical deformation of molecular structure, is directly visualized in the K4C60 monolayer at the single-molecule level. These results, along with theoretical analyses, provide strong evidence that the transition from metal to insulator in K(x)C60 monolayers is caused by the Jahn-Teller effect.

Controlled atomic doping of a single C60 molecule.

We report a method for controllably attaching an arbitrary number of charge dopant atoms directly to a single, isolated molecule. Charge-donating K atoms adsorbed on a silver surface were reversibly attached to a C60 molecule by moving it over K atoms with a scanning tunneling microscope tip. Spectroscopic measurements reveal that each attached K atom donates a constant amount of charge (approximately 0.6 electron charge) to the C60 host, thereby enabling its molecular electronic structure to be precisely and reversibly tuned.

Direct observation of internal spin structure of magnetic vortex cores.

Thin film nanoscale elements with a curling magnetic structure (vortex) are a promising candidate for future nonvolatile data storage devices. Their properties are strongly influenced by the spin structure in the vortex core. We have used spin-polarized scanning tunneling microscopy on nanoscale iron islands to probe for the first time the internal spin structure of magnetic vortex cores. Using tips coated with a layer of antiferromagnetic chromium, we obtained images of the curling in-plane magnetization around and of the out-of-plane magnetization inside the core region. The experimental data are compared with micromagnetic simulations. The results confirm theoretical predictions that the size and the shape of the vortex core as well as its magnetic field dependence are governed by only two material parameters, the exchange stiffness and the saturation magnetization that determines the stray field energy.

[Epidemiology of proximal femur fracture and results of therapy in patients treated at the Orthopedic-Trauma Ward of the Railway Hospital in Warsaw in the years 1986-1990]. / Epidemiologia zlaman czesci blizszej kosci udowej oraz ocena kosztów leczenia (material Oddzialu Ortopedyczno-Urazowego Szpitala Kolejowego w Warszawie w latach 1986-1990).

A retrospective analysis included 441 hospitalized patients with fractures of the proximal femoral bone, treated at the orthopedic-traumatology ward in 1986-1990. Such patients constituted 9.12% of all patients treated during those years. There were 313 women aged between 26 and 99 years (mean 77.4 years) and 128 men aged between 30 and 95 years (mean 68.3 years). Fractures were more frequent in women than in men (rate 2.4:1). Four hundred four patients (91.6%) were treated surgically. Mortality rate in this group was about 10% whereas in patients treated conservatively--approximately 66%. Locomotive functions were restored in the majority of patients under 80 years of age. Mean hospitalization time was 22 days. Mean cost per patient in zlotys treated surgically was 4.97 million in 1990, and 8.3 million in 1992.