Mechanical on-chip microwave circulator.

Nonreciprocal circuit elements form an integral part of modern measurement and communication systems. Mathematically they require breaking of time-reversal symmetry, typically achieved using magnetic materials and more recently using the quantum Hall effect, parametric permittivity modulation or Josephson nonlinearities. Here we demonstrate an on-chip magnetic-free circulator based on reservoir-engineered electromechanic interactions. Directional circulation is achieved with controlled phase-sensitive interference of six distinct electro-mechanical signal conversion paths. The presented circulator is compact, its silicon-on-insulator platform is compatible with both superconducting qubits and silicon photonics, and its noise performance is close to the quantum limit. With a high dynamic range, a tunable bandwidth of up to 30 MHz and an in situ reconfigurability as beam splitter or wavelength converter, it could pave the way for superconducting qubit processors with multiplexed on-chip signal processing and readout.Nonreciprocal optical elements often require magnetic materials in order to break time-reversal symmetry. Here, Barzanjeh et al. demonstrate a magnetic-free on-chip microwave circulator that utilizes the interference from six electro-mechanical signal paths.

[A young patient with multiple arterial occlusions]. / Junge Patientin mit multiplen arteriellen Verschlüssen.

BACKGROUND: Mild hyperhomocysteinemia due to genetic causes and nutrition factors is well known as an independent strong risk factor for premature arterial occlusive disease. CASE REPORT: A 27-year-old female with a history of two episodes of small bowel ileus due to vascular causes presented with subacute pain in the left lower extremity. Angiography revealed a short segmental occlusion in the P III segment of the popliteal artery with small vessel collateralization and proximal occlusion of the superior mesenteric artery und the coeliac trunk. Vascular risk factors in this patient included smoking over a duration of 10 years, use of oral contraceptives (estrogen and gestagen combination) and elevated levels of homocysteine in the fasting state and after methionin loading. The patient was treated conservatively with intravenous application of prostaglandins, additionally she underwent training to improve her walking capability. After 4 weeks of the fasting state as well as after methionin loading were normalized by an oral substitution with folate and B vitamins. So far it was not possible to prove a genetic defect of the enzymes participating in the metabolism of homocysteine. CONCLUSION: This clinical conference of a young female patient with occlusion of several arteries illustrates the differential diagnosis of premature occlusive vascular disease with special regard to mild hyperhomocysteinemia as an independent risk factor.

Muscle metabolism during exercise in diabetics and in obese during starvation.

The influence of exercise on forearm muscle metabolism was examined in 9 healthy subjects, in 16 diabetics and in 4 obese subjects during complete starvation. During exercise glucose uptake rose 7-8 fold in the controls. However, no increase of glucose uptake was observed in the other groups studied. Moreover, a glucose production from the working muscle took place in about 40 percent of both the diabetic patients and the starved obese subjects. The nonutilization of glucose during physical work in the diabetic like states was accompanied by a significantly diminished lactate output. The arterial concentration of FFA, glycerol beta-HOB and Acac was markedly elevated in the starved obese patients. The FFA-uptake at rest and during exercise, however, was not different from results of controls. Whereas an effux of beta-HOB has been observed during exercise, Acac uptake was increased in these patients. It is suggested that in maturity onset and starvation diabetes glycolysis is inhibited.

[Concordant deuteranomaly in monozygotic twin sisters (author's transl)]. / Jumelles monozygotiques atteintes de deuteranomalie concordante

Colorblind twin sisters were born from the marriage of a hemizygote with a carrier for colorblindness. The proof of monozygosity is given by the blood-group typing and the dermatoglyphs. The deuteranomaly is of the same degree in each but is more marked in one of the sisters. The mother has none of the microsymptoms sometimes found in carriers.

[Muscle metabolism of glucose, lactate, free fatty acids, and glycerol at rest and during electrically stimulated exercise in the perfused rat hind limb (author's transl)]. / Kohlenhydrat- und Fettstoffwechsel der Skelettmuskulatur unter Ruhebedingungen und bei kurzfristiger submaximaler Arbeit am Modell des perfundierten Hinterbeins der Ratte

The influence of insulin on muscle metabolism at rest and during electrically stimulated exercise was examined in the perfused rat hind limb. Basal glucose uptake of muscle tissue was enhanced threefold both by muscle contraction an by addition of physiological amounts of insulin. A further increase in glucose uptake was seen, when muscle was exercised in the presence of insulin. Lactate production rose 7 - 8fold by contractions. Insulin had no additional effect on lactate production during exercise. The work-induced lactate output exceeded glucose uptake, corresponding to a significantly reduced glycogen content after exercise. Basal lipolysis was not stimulated by muscle contractions. At rest the addition of both corticosterone and thyroxine did not increase the basal lipolysis. Yet, glycerol release rose twofold by the addition of serum to the perfusion medium. It is assumed that in the perfused rat hind limb glycogenolysis will promptly be stimulated by muscle contractions, whereas lipolysis can not be enhanced by exercise alone.