Heterostructures produced from nanosheet-based inks.

The new paradigm of heterostructures based on two-dimensional (2D) atomic crystals has already led to the observation of exciting physical phenomena and creation of novel devices. The possibility of combining layers of different 2D materials in one stack allows unprecedented control over the electronic and optical properties of the resulting material. Still, the current method of mechanical transfer of individual 2D crystals, though allowing exceptional control over the quality of such structures and interfaces, is not scalable. Here we show that such heterostructures can be assembled from chemically exfoliated 2D crystals, allowing for low-cost and scalable methods to be used in device fabrication.

Controlled modification of mono- and bilayer graphene in O2, H2 and CF4 plasmas.

In this work, covalent modification of mono- and bilayer graphene is achieved using tetrafluoromethane (CF4), oxygen and hydrogen RF plasma. Controlled modification of graphene is usually difficult to achieve, in particular with oxygen plasma, which is rather aggressive and usually leads to etching of graphene. Here we use x-ray photoelectron spectroscopy and Raman spectroscopy to show that mild plasma conditions and fine tuning of the number of functional groups can be obtained in all plasmas by varying parameters such as exposure time and sample position inside the chamber. We found that even for the usual harsh oxygen treatment the defect density could be lowered, down to one defect for 3.5 × 104 carbon atoms. Furthermore, we show that CF4 plasma leads to functionalization without etching and that graphene becomes an insulator at saturation coverage. In addition, the reactivity of mono- and bilayer graphene was studied revealing faster modification of monolayer in oxygen and CF4 plasma, in agreement with previous works. In contrast, similar modification rates were observed for both mono- and bilayer during hydrogenation. We attribute this discrepancy to the presence of more energetic species in the hydrogen plasma such as positive ions that could play a role in the functionalization process.

Strong light-matter interactions in heterostructures of atomically thin films.

The isolation of various two-dimensional (2D) materials, and the possibility to combine them in vertical stacks, has created a new paradigm in materials science: heterostructures based on 2D crystals. Such a concept has already proven fruitful for a number of electronic applications in the area of ultrathin and flexible devices. Here, we expand the range of such structures to photoactive ones by using semiconducting transition metal dichalcogenides (TMDCs)/graphene stacks. Van Hove singularities in the electronic density of states of TMDC guarantees enhanced light-matter interactions, leading to enhanced photon absorption and electron-hole creation (which are collected in transparent graphene electrodes). This allows development of extremely efficient flexible photovoltaic devices with photoresponsivity above 0.1 ampere per watt (corresponding to an external quantum efficiency of above 30%).

[Diagnosis of atherosclerotic lesions of the extracranial carotid artery using duplex sonography and IA-DSA. A prospective pathologically and anatomically controlled study]. / Zur Diagnostik atherosklerotischer Läsionen der extrakraniellen Arteria carotis mit Duplexsonographie und IA-DSA. Eine prospektive und pathologisch-anatomisch kontrollierte Studie.

Fifty patients were studied prospectively. The extracranial portions of the carotid arteries were examined by duplex sonography and IA-DSA in order to demonstrate haemodynamically significant stenoses or plaques which might give rise to emboli and the findings compared with the pathologic specimens. The results indicate high sensitivity (up to 90%) for more than 75% detection of stenoses. On the other hand ulceration was diagnosed sonographically with an accuracy of 66% and plaque hemorrhage with an accuracy of 56%.

[Early B-scan sonographic recognition of extracranial carotid atherosclerosis in patients at risk and its significance from the preventive medicine viewpoint]. / B-Scan-sonographische Früherkennung der extrakraniellen Karotis-Atherosklerose bei Risikopatienten und ihre Bedeutung aus präventivmedizinischer Sicht.

High-resolution 10 Mhz sonography was performed on 27 hypertensive patients, 24 diabetics, 39 hypertensive diabetics and 23 normal people in order to demonstrate asymptomatic arteriosclerotic lesions of the extra-cranial carotid artery. Compared with normal controls, diabetics and hypertensives showed increased vessel wall thickness, but only patients with hypertension showed a higher frequency of plaques and relevant carotid stenoses. The left carotid artery is involved more often. On the basis of these results, it appears that the use of B-scan sonography as a preventive measure should be limited to the high-risk hypertensive population.

[Sonomorphological characterization of arteriosclerotic plaques--potentials and limitations of high-resolution B-scan sonography]. / Sonomorphologische Charakterisierung arteriosklerotischer Plaques--Möglichkeiten und Grenzen der hochauflösenden B-Scan-Sonographie.

One hundred and five carotid stenoses were examined by B-scan sonography (10 MHz) and the results compared with the macroscopic and histological appearances. The most important sonographic findings depended on surface structure, echo amplitude and the presence of acoustic shadows. From the therapeutic point of view, B-scan sonography is complementary to angiography by evaluating the morphology of the plaques, particularly if the indications for surgery are ill-defined.

[Isolated aneurysms of the iliac arteries]. / Isolierte Aneurysmen der Iliakalarterien.

Isolated aneurysms of the iliac arteries are rare. They must be considered as a disease pattern of their own as against aneurysms of the abdominal aorta because of the specific anatomical conditions in the pelvis. The clinical symptomatology is determined by their localisation and topographical relationships within the pelvis; this can give rise to problems in differential diagnosis primary urological, neurological or gastrointestinal diseases. The prognosis is decisively determined by early and correct diagnosis because of the danger of rupture. Sonography, computed tomography and angiography are indispensable aids in preoperative planning.

[Liver CT with portal vein administration of a contrast medium]. / Leber-CT mit portal-venöser Kontrastmittelgabe.

Contrast administration through the superior mesenteric or splenic arteries provided additional information in 22 out of 31 patients, when compared with intravenous contrast bolus for CT of the liver. In 11 patients, the demonstration of a tumour lead to a change in treatment. False positive findings occurred in four of the 31 patients. In 2 patients intrahepatic lesions were overlooked, but were found during angiography carried out at the same examination. The diagnosis of intrahepatic space-occupying lesions is discussed as well as the CT appearances of portal-venous liver perfusion.

[Removal of a fixed T-drain following detachment by a ring stripper]. / Entfernung eines fixierten T-Drains nach Lösung durch Ringstripper.

This is a report on an intra-abdominally fixed T-drain. Surgical removal was avoided without complications by detaching it with a ring stripper.

[Functional echo morphology of Bauhin's valve]. / Funktionelle Echomorphologie der Bauhinschen Klappe.

Following rectal irrigation, it is possible to demonstrate the ileo-caecal valve sonographically, using a right para-inguinal approach. The shape, position and motility of the valve can be evaluated. The normal valve is two to three mm. thick, similar to the colonic wall, but its lips are thickened. Two distinct mechanisms are responsible for opening the valve, the ileocolic pressure gradient and relaxation of the circular muscle round the valve. The resulting intraluminal flow can be quantified by duplex sonography. The information may be of diagnostic and therapeutic significance, particularly during childhood.

[Postoperative follow-up after thromboendarterectomy of the carotid artery using duplex sonography]. / Postoperative Verlaufskontrolle nach Thrombendarteriektomie der A. carotis mit der Duplex-Sonographie.

Fifty-one patients, on whom a total of 64 carotid thromboendarterectomies had been performed, were followed up by duplex sonography. Five asymptomatic occlusions of the internal carotid artery (8%) and one occlusion of the common carotid artery were found. Two patients (3%) developed a restenosis of more than 50% and another two patients a restenosis of less than 50%. Changes in the vessel wall not producing significant luminal change were observed in another 18 cases (28%). Thirty-six of the operated vessels (56%) showed no change.

[Blood picture changes in rats after 90Y-citrate administration]. / Blutbildveränderungen bei Ratten nach Verabreichung von 90Y-Zitrat.

Therapeutic doses of 90Y-citrate show a high selective accumulation in bone. Bone marrow is the critical organ. Investigations in rats show a decrease of leucocytes, erythrocytes and thrombocytes depending on dose. A significant decrease of the leucocytes and thrombocytes was seen with 0.5 mCi (17.5 MBq) 90Y per kg bodyweight, with 2.0 mCi (74 MBq) also of the erythrocytes. This would be equivalent to a dose of 35 to 140 mCi (1.295 to 5.18 GBq) for a normal patient (70 kg). Therefore, a single dose of 10 mCi (370 MBq) of 90Y-citrate should be tolerated by a tumor patient without any blood cell depression, if there was no prior chemotherapy.