A strident girl

A 12-year-old girl was referred with a 7-month history of episodes of dyspnoea, stridor and a sense of chest constriction during physical exercise. These were self-limiting and never occurred at night. Physical examination was normal. An initial diagnosis of vocal cord dysfunction was made.Spirometry showed a plateau of forced expiratory flow, with a truncated aspect of the expiratory phase (figure 1). Six weeks later she described occasional dysphagia with solid foods. The barium swallow, performed only in anteroposterior projection, did not show oesophageal dilation. A bronchoscopy showed extrinsic compression of the middle lower third of the trachea and the right main bronchus. A chest CT scan was performed (figures 2 and 3).Figure 1The spirometry showed a truncated expiratory phase with a substantially decreased PEF, compared with FEV1: indicating central intrathoracic airway obstruction. FEF, forced expiratory flow; FEV1, forced expiratory volume in 1 s; FIF, forced inspiratory flow; FIV1, forced inspiratory volume in 1 s; FIVC, forced inspiratory vital capacity; FVC, forced vital capacity; PEF, peak expiratory flow; PIF, peak inspiratory flow.Figure 2Contrast enhanced CT axial section image showing right aortic arch (white arrow on the left) with aberrant subclavian artery (red arrow on the right) encircling the trachea and the oesophagus.Figure 3CT three-dimensional reconstruction arteriography posterior view showing right aortic arch (white arrow), diverticulum of Kommerell (white star) from which the left subclavian artery (red arrow) arose. D Ao, descending aorta.QuestionsWhat is your diagnosis?Persistent vocal cord dysfunctionAchalasiaVascular ringAsthmaWhat is the gold standard for diagnosis of VR?ECGChest radiographCT and/or MRIBronchoscopyHow should this patient be treated?Surgical correctionVideo-assisted thoracoscopyDecompression of the oesophagus with a nasogastric tubeInspiratory muscle training and ipratropium bromide inhalerWhat signs in the history pointed away from vocal cord dysfunction?Dysphagia with solid food was present.The episodes of dyspnoea and stridor never occurred at night.The episodes arose mainly on exertion.The episodes of dyspnoea and stridor were self-limiting.Answers can be found on page 2.

Floral signposts: testing the significance of visual ‘nectar guides’ for pollinator behaviour and plant fitness

Nectar guides, contrasting patterns on flowers that supposedly direct pollinators towards a concealed nectar reward, are taxonomically widespread. However, there have been few studies of their functional significance and effects on plant fitness. Most previous studies focused on pollinator behaviour and used artificial flowers in laboratory settings. We experimentally investigated the role of putative nectar guides in a natural system: the South African iris Lapeirousia oreogena , whose flowers have a clearly visible pattern of six white arrow-markings pointing towards the narrow entrance of the long corolla tube, and its sole pollinator, a long-proboscid nemestrinid fly. We painted over none, some or all of the white arrow-markings with ink that matched the colour of the corolla background. Although arrow-marking removal had little effect on the approaches by flies to flowers from a distance, it dramatically reduced the likelihood of proboscis insertion. Export of pollen dye analogue (an estimate of male fitness) was reduced to almost zero in flowers from which all nectar guides had been removed, and fruit set (a measure of female fitness) was also significantly reduced. Our results confirm that the markings on L. oreogena flowers serve as nectar guides and suggest that they are under strong selective maintenance through both male and female fitness components in this pollination system.

Metastasis to Internal Mammary Node

• 56-year-old patient with a history of breast cancer • Confluence of shadows (white arrow) looks like a lesion in left lung, but it is not seen on CT (next slide). The lesion on the lateral CXR is in the right lung (yellow arrow) •...

Fins

Judging by the number of present-day aircraft which have suffered changes of fin shape, it is clear that there is still some difficulty in estimating the size and shape of fin required on a new project. In this paper some of the principles on which fin design is based will be explained, and some of the difficulties involved described.It is necessary to have some sort of fin to provide weathercock, or directional, stability. This is illustrated in Fig. 1. This shows the balance of yawing moments, due to sideslipping. In general, the side force acting on the fuselage, represented by the black arrow, has its c.p. ahead of the e.g. of the aircraft, and hence it produces a destabilising moment about the e.g. Sufficient fin area must be provided for the yawing moment due to the fin side force, represented by the white arrow, to at least equal the destabilising fuselage moment. Otherwise, when disturbed laterally due to, say, a gust, the aeroplane will tend to swing still further out of wind, making it difficult to fly accurately. The minimum permissible fin area can, in fact, be fixed simply by this requirement for weathercock stability.