Observation of the effect of gravity on the motion of antimatter.

Einstein's general theory of relativity from 19151 remains the most successful description of gravitation. From the 1919 solar eclipse2 to the observation of gravitational waves3, the theory has passed many crucial experimental tests. However, the evolving concepts of dark matter and dark energy illustrate that there is much to be learned about the gravitating content of the universe. Singularities in the general theory of relativity and the lack of a quantum theory of gravity suggest that our picture is incomplete. It is thus prudent to explore gravity in exotic physical systems. Antimatter was unknown to Einstein in 1915. Dirac's theory4 appeared in 1928; the positron was observed5 in 1932. There has since been much speculation about gravity and antimatter. The theoretical consensus is that any laboratory mass must be attracted6 by the Earth, although some authors have considered the cosmological consequences if antimatter should be repelled by matter7-10. In the general theory of relativity, the weak equivalence principle (WEP) requires that all masses react identically to gravity, independent of their internal structure. Here we show that antihydrogen atoms, released from magnetic confinement in the ALPHA-g apparatus, behave in a way consistent with gravitational attraction to the Earth. Repulsive 'antigravity' is ruled out in this case. This experiment paves the way for precision studies of the magnitude of the gravitational acceleration between anti-atoms and the Earth to test the WEP.

Sympathetic cooling of positrons to cryogenic temperatures for antihydrogen production.

The positron, the antiparticle of the electron, predicted by Dirac in 1931 and discovered by Anderson in 1933, plays a key role in many scientific and everyday endeavours. Notably, the positron is a constituent of antihydrogen, the only long-lived neutral antimatter bound state that can currently be synthesized at low energy, presenting a prominent system for testing fundamental symmetries with high precision. Here, we report on the use of laser cooled Be+ ions to sympathetically cool a large and dense plasma of positrons to directly measured temperatures below 7 K in a Penning trap for antihydrogen synthesis. This will likely herald a significant increase in the amount of antihydrogen available for experimentation, thus facilitating further improvements in studies of fundamental symmetries.

Laser cooling of antihydrogen atoms.

The photon-the quantum excitation of the electromagnetic field-is massless but carries momentum. A photon can therefore exert a force on an object upon collision1. Slowing the translational motion of atoms and ions by application of such a force2,3, known as laser cooling, was first demonstrated 40 years ago4,5. It revolutionized atomic physics over the following decades6-8, and it is now a workhorse in many fields, including studies on quantum degenerate gases, quantum information, atomic clocks and tests of fundamental physics. However, this technique has not yet been applied to antimatter. Here we demonstrate laser cooling of antihydrogen9, the antimatter atom consisting of an antiproton and a positron. By exciting the 1S-2P transition in antihydrogen with pulsed, narrow-linewidth, Lyman-α laser radiation10,11, we Doppler-cool a sample of magnetically trapped antihydrogen. Although we apply laser cooling in only one dimension, the trap couples the longitudinal and transverse motions of the anti-atoms, leading to cooling in all three dimensions. We observe a reduction in the median transverse energy by more than an order of magnitude-with a substantial fraction of the anti-atoms attaining submicroelectronvolt transverse kinetic energies. We also report the observation of the laser-driven 1S-2S transition in samples of laser-cooled antihydrogen atoms. The observed spectral line is approximately four times narrower than that obtained without laser cooling. The demonstration of laser cooling and its immediate application has far-reaching implications for antimatter studies. A more localized, denser and colder sample of antihydrogen will drastically improve spectroscopic11-13 and gravitational14 studies of antihydrogen in ongoing experiments. Furthermore, the demonstrated ability to manipulate the motion of antimatter atoms by laser light will potentially provide ground-breaking opportunities for future experiments, such as anti-atomic fountains, anti-atom interferometry and the creation of antimatter molecules.

Skin lifting in aesthetic cervicofacial rhytidectomy: personal experience in more than 1500 patients.

BACKGROUND: Skin lifting alone in face-lifting surgery is limited to minor lifts in younger patients. The extent of skin undermining depends on the operative plan. AIMS: An optimal aim is to minimize the amount of undermining to achieve a pleasing, natural rejuvenated result. RESULTS: By respecting the extensive network of the dermal vascular plexus and by good surgical technique, ischaemia of the elevated skin may be minimized. CONCLUSION: Moderate to maximal lifting, however, has proven to be anatomically sound in over 1500 cases operated on over the last 20 years using classical face-lift techniques to correct the pathoanatomy of the ageing face.

Expansion techniques after Mohs' surgery on the face.

Mohs' surgery in the face has established itself as the optimal technique for a high cure rate of basal cell and squamous cell carcinoma occurring in the skin of the face. However, after the resection in Mohs' surgery, the defects, when extensive, require careful, planned reconstruction in order to produce a good cosmetic result. Although flap reconstruction is available for smaller lesions, larger defects can be covered often by expansion techniques. The expansion technique involves placing a silastic expander of various size and designs underneath the adjacent skin and, over a period of weeks, injecting saline into the expander in order to increase the amount of skin available for future flap reconstruction. This usually represents a two-stage procedure consisting of the insertion of the expander and, some weeks later, removal of the filled expander when there is sufficient tissue, and using this tissue to reconstruct the initial Mohs' defect by a flap. When defects are greater than half the aesthetic unit of the face, or greater than one-third in the forehead, or over 6 cm in the scalp, expansion techniques should be considered for reconstruction.

Community dynamics, trade-offs, invasion criteria and the evolution of host resistance to microparasites.

This article discusses the community dynamics of the evolution of host resistance to microparasites. We present exact results for a model with an arbitrary number of host strains. We show that these results are identical to those inferred on the basis of invadability criteria. The long-term behaviour of the model allows monomorphism or dimorphism (but no higher polymorphisms). We invoke trade-offs between pathogen transmissibility and either host intrinsic growth rate or resistance to crowding. In the first case, convexity leads to an ESS, concavity to branching points and repellers. In the second, these roles are interchanged. We present results for fixed strain distributions and establish parallels with results using an adaptive dynamics perspective. We also establish differences. For example, if an ESS is "deleted" from the strain distribution, then adjacent-strain dimorphism is possible. The invadability criteria which we obtain can be expressed in terms of geometrical properties of the trade-offs namely, the slopes of chords and tangent to the associated function. We speculate that this result may have wider applicability than provided by the context of the present work.

Hyperventilation: cause or effect?

A young person presenting with shortness of breath is common to the accident and emergency department. Usually this hyperventilation is anxiety related or a panic attack, but sometimes it can be caused by a serious underlying condition like pulmonary embolus. Acute shortness of breath in any patient should never be dismissed lightly. It is important to realise that pulmonary embolus can present without chest pain and with shortness of breath as the major symptom. Such patients can be distinguished by close attention to history and examination, risk factors for thromboembolic disease and the use of basic investigations (electrocardiogram, chest radiography and arterial blood gas analysis). A serious cause for shortness of breath must be excluded before labelling it as "hysteria" or "panic".

Chest pain in the emergency department.

The assessment of patients with chest pain is challenging for any emergency physician because of the spectrum of illness covered by this symptom. Patients may have a serious life-threatening condition or a trivial self-limiting illness. This article presents an approach to the assessment and early management of patients presenting with acute non-traumatic chest pain in the emergency department.

Phytophotodermatitis associated with parsnip picking.

Phytophotodermatitis to certain plant groups is a well recognised entity. The combination of sunlight exposure and contact with plants of the umbelliferae family leads to the development of painful, erythematous, and bullous lesions and later to cutaneous hyperpigmentation. Agricultural workers and many clinicians often fail to make this link when patients present with these lesions. An incident involving 11 patients is presented to high-light this problem.

Cocaine induced myocardial infarction.

The case of a 29 year old man who presented with chest pains after the use of cocaine is reported. The diagnosis of myocardial infarction was made on the electrocardiogram changes and lactate dehydrogenase profile. The diagnosis may be overlooked if there is no direct questioning about the use of drugs such as cocaine. Diazepam has an important role in the management of cardiac complications after cocaine use and should be used early in management. The use of thrombolysis should be a joint decision between the emergency physician and cardiologist.

Buckled upper pole breast style 410 implant presenting as a manifestation of capsular contraction.

Recent experience with the cohesive gel implant has shown an interesting variation of capsular contracture. Instead of spherical contraction, the capsule formation around the 410 implant seems to cause a buckling of the superior pole of the implant. This buckling has been observed in four implants and presented clinically in 2 of 50 patients with a superior pole mass. The capsular contraction around the implant and the buckling are probably camouflaged by a subpectoral implantation and this presentation should be recognized by the surgeon, especially when considering placement of the cohesive gel implant in a subglandular position. Histological sections of a capsule around the implant show fragmented silicone, with a cellular reaction around the fragmented silicone.

Reconstruction of the upper lip with lip switch (Abbe flap reconstruction).

The lip switch operation (Abbe) is useful for full thickness defects of the upper lip. Careful design of the flap with pedicle take-down and inset of the flap after 2 weeks, leads to a predictably good reconstructive result. The flap is most useful for 30-50% full thickness defects of the upper lip.

Chest wall implants: their use for pectus excavatum, pectoralis muscle tears, Poland's syndrome, and muscular insufficiency.

Solid customized and prefabricated silicone implants have been used by the author for 15 years in a wide range of chest wall deformities. Chest wall implants are often used in males seeking to augment a muscularly deficient or underdeveloped chest; however, their greatest use has come in a variety of deformities both congenital and acquired, such as pectus excavatum, Poland's Syndrome, and pectoralis muscle tears. The implants can be either customized using a moulage technique or are prefabricated, manufactured implants which can be modified on the operating table to repair the contour deformity. The immediate postoperative problem of seroma and subcutaneous implant "show" has been minimized by careful planning, gentle technique, deep insertion, improved patient positioning on the operating room table, and the use of oral anti-inflammatory medications. The long-term results of these implants seem very satisfactory. The patients are usually physically active, and the implants show no long-term sequelae such as seroma, infection, displacement, or rupture.

Warfarin and the apparent minor head injury.

Two cases of patients on warfarin who developed intracranial haematoma after an apparently minor head injury are described. There is a 10-fold increase in the likelihood of developing an intracranial haematoma in these patients. Recommendations are made regarding the management of this type of patient seen in the accident and emergency department.