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van der Waals crystals have opened a new and exciting chapter in heterostructure research, removing the lattice matching constraint characteristics of epitaxial semiconductors. They provide unprecedented flexibility for heterostructure design. Combining two-dimensional (2D) perovskites with other 2D materials, in particular transition metal dichalcogenides (TMDs), has recently emerged as an intriguing way to design hybrid opto-electronic devices. However, the excitation transfer mechanism between the layers (charge or energy transfer) remains to be elucidated. Here, we investigate PEA2PbI4/MoSe2 and (BA)2PbI4/MoSe2 heterostructures by combining optical spectroscopy and density functional theory (DFT) calculations. We show that band alignment facilitates charge transfer. Namely, holes are transferred from TMDs to 2D perovskites, while the electron transfer is blocked, resulting in the formation of interlayer excitons. Moreover, we show that the energy transfer mechanism can be turned on by an appropriate alignment of the excitonic states, providing a rule of thumb for the deterministic control of the excitation transfer mechanism in TMD/2D-perovskite heterostructures.

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The sensitivity of chest radiography for the early detection of mycetoma formation within fibrotic cavities is poor. The purpose of this study was to determine the predictive value of the secondary sign of lateral cavity wall thickening for the detection of a radiographically occult mycetoma. The chest radiographs and CT scans of 70 patients who had a total of 109 fibrotic cavities on CT were reviewed by two observers. Dimensions of the cavity, mycetoma, and cavity wall thickness on chest radiography and CT scans were recorded. Mycetomas were visible in 41 of 99 cavities on chest radiographs and in 61 of 109 cavities on CT. Using CT as the gold standard for detecting the presence of mycetomas, the sensitivity of chest radiography for the presence of a mycetoma was 62 % and the specificity 94 %, and the positive and negative predictive values were 93 and 66 %, respectively. On logistic regression analysis, lateral wall thickness on chest radiography was predictive of the presence of a mycetoma (p < 0.0005) independent of other radiographic features. In patients with chronic fibrocavitary disease on chest radiography, the presence of lateral wall thickening is highly suggestive of an underlying mycetoma.

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AIM: To evaluate the yield of abdominal computed tomography (CT) in patients with human immunodeficiency virus (HIV) infection and to assess the influence of CT scanning on patient management and diagnosis. METHOD: A retrospective analysis of 216 abdominal CT scans, performed on 156 patients (147 men, nine women; age range 22-57 years), between March 1992 and October 1994 was undertaken. Clinical information, including the indication for performing the scan and the eventual diagnosis, was obtained from the case notes and the contribution of CT scanning to patient management assessed. RESULTS: Indications for CT fell into five main groups: investigation of pyrexia of unknown origin (PUO) (n = 82), staging and response to treatment of previously diagnosed neoplasms (n = 46), investigation of abdominal pain (n = 20), CT undertaken to clarify the results of other imaging investigations (n = 20) and miscellaneous indications (n = 48). An eventual diagnosis thought to account for the clinical presentation was made in 150 cases (68%), reflecting the high level of underlying pathology. CT contributed to patient management in a large proportion of cases (62%), but only led directly to a diagnosis in a minority (12%). CONCLUSION: With the exception of patients presenting with PUO, abdominal CT remains an important investigation in the management of patients with HIV infection. In patients presenting with PUO a thorough infection screen should be undertaken prior to CT scanning. Whilst frequently contributing to patient management, CT rarely leads directly to a diagnosis.

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A postal survey was performed to determine the current practices and attitudes of radiologists towards the imaging of suspected lower limb deep vein thrombosis (DVT). One hundred and twenty-seven departments responded to a questionnaire sent in March 1996. The results show that 87% of hospitals possess colour Doppler ultrasound (CDUS) machines and that 46% of departments perform ultrasound as the first line investigation in over 90% of cases. Thirty per cent of departments considered calf vein visualization to be generally adequate and 34% thought that clinicians in their hospitals invariably anticoagulated patients with isolated calf thrombus. In hospitals where venography was routinely used as the first line investigation, the most common reasons were: the perceived inferiority of ultrasound (US) in demonstrating below-knee clot, its time-consuming nature and the limited access to suitable ultrasound machines. The widespread use of ultrasound is encouraging, however, there are clearly diverse views. A significant minority of departments depend principally upon venography in the diagnosis of DVT.

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Five cases of small cell carcinoma (three of the prostate and two of the bladder) are described to illustrate the unusual behaviour of these tumours. Cerebral, hepatic and bulky lymph node spread with large volume local disease occurred. The role the radiologist may play in these diseases is discussed.

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Vinte e um casos de pacientes portadores de tumor carcinóide säo analisados. Em 18 deles o diagnóstico foi realizado através de cirurgia e em três deles por necrópsia. Os locais mais freüentes do tumor primário foram o apêncice cecal (38,1%), íleo (23,8%) e cólon (19%). Tumores assintomáticos foram descobertos em dez pacientes (55,5%) de maneira incidental. Os casos sintomáticos foram mais freqüentes em pacientes com carcinóide do íleo. Em nenhum paciente desta série foi obtido diagnóstico antes de operaçäo ou necropsia. Neste estudo näo se observou pacientes com síndrome carcinóide. Cirurgia de ressecçäo da neoplasia foi realizada em 16 pacientes (88,8%) e a sobrevivência média neste grupo foi de 10,7 anos. Operaçäo paliativa foi realizada em dois pacientes (11,1%), cuja sobrevivência média foi de 3,5 meses. Metástases foram encontradas em 71,4% dos pacientes com lesäo neoplásica maior que 2,0cm de diâmetro e em 7,6% dos pacientes com tumor menor que 2,0cm de diâmetro; todos os pacientes com lesöes metastáticas eram portadores de carcinóide de cólon ou do íleo. Os pacientes portadores de carcinóide do apêndice cecal näo apresentaram metástases. Neste estudo, o prognóstico esteve relacionado com o tamanho da lesäo, localizaçäo do tumor no trato gastrointestinal e com a ressecabilidade ou näo da neoplasia primária

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