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.

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.

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.

Scrotal reconstruction for giant inguinal hernias.

A case of inguinal hernia with massive scrotal enlargement is presented. Walking and voiding had become extremely difficult for the patient; only one testicle could be palpated, and the penis could not be delivered from the scrotal mass. Surgical reduction of the massive hernia was accomplished. The right testis with its spermatic cord had to be sacrificed; the left one was normal, although the cord was elongated. The main bulk of the enlarged scrotum was excised, and a neoscrotum was created from perineal skin; orchiopexy on the left was carried out. Healing has been uneventful.

Extra-adrenal intrathoracic functioning paraganglioma (pheochromocytoma) in childhood.

Extra-adrenal pheochromocytomas are more common in children (30%) than in adults (10%). Of the extra-adrenal sites, the intrathoracic site is the most rare. A 15-year-old boy had a pheochromocytoma successfully removed from the left paraspinal region of his chest. Four years before removal, he had radiation therapy of 3,500 rads to the tumor because of its apparent nonresectability. After therapy, there was transient clinical and biochemical improvement. Preoperative angiography and computed tomography helped define the anatomy of the tumor vessels and the relationship to the thoracic aorta of the tumor. These studies also aided in discounting any other site for the pheochromocytoma, either adrenal or extramedullary. A slow-growing pulmonary metastatic lesion was subsequently identified and successfully excised.

Pancreatic cystadenoma. A clinicopathologic study of 45 cases.

Forty-five patients with pancreatic cystadenoma were treated surgically at the Mayo Clinic between 1939 and 1975. Each lesion was classified as mucous or serous. The most frequent lesion site was the tail of the pancreas. The typical patient was a middle-aged woman with upper abdominal pain and a palpable mass on initial examination. Total extirpation of the cystadenoma was the treatment of choice; internal drainage or external drainage of these cysts should not be done. Occasionally, the nearness of the tumors to the mesenteric vessels precluded excision. The mucous type had malignant potential whereas the serous does not. None of the cystadenomas subsequently underwent malignant degeneration. Because of the slow-growing characteristics of the tumor, undue operative risks should not be taken.

Early hemodynamic changes at the microcirculatory level and effects of mannitol following focal cryogenic injury.

Changes in cerebral blood flow due to infusion of hyperosmolar solutions are of considerable importance in states of raised intracranial pressure. The present study was aimed to evaluate the effects of mannitol on the cerebral microcirculation, in a model of vasogenic brain edema. A right fronto-parietal craniotomy was performed in 30 adult Sprague-Dawley rats. Vasogenic edema was produced by placing dry-ice over the dura for 1 min. The cortical blood flow was monitored for 120 min using a laser-Doppler flowmeter (Perimed, Stockholm, Sweden), and graphics were recorded using a personal computer. Animals were randomly divided into three groups: group 1 (control group) received no mannitol; group 2 was treated with a bolus injection of 20% mannitol (1 mg kg-1); group 3 received the same dose over a 30 min infusion. Mean blood pressure, temperature, and respiratory rate were continuously monitored. At the end of the procedure, an intravenous injection of Evan's blue 2% was given. Results were compared by using repeated measures of analysis of variance and a two-sample t-test at each time. After the production of a cryogenic injury, we found a marked decrease in the cerebral blood flow, whereas mannitol partially reversed that effect. There was not significant difference between groups 2 and 3; however, there was a significant difference between mannitol and control groups after 15 min. During the early phase of vasogenic edema, early use of mannitol did not increase the blood flow, but stabilized it, preventing further decrease. Laser-Doppler flowmetry is a valuable method for continuous estimation of hemodynamic changes in the cerebral microcirculation.

Scrotal reconstruction for giant inguinal hernias.

Giant inguinal hernias require special consideration for repair of the abdominal wall. The associated greatly thickened, enlarged scrotum should be discarded and a neoscrotum should be reconstructed from the uninvolved perineal-scrotal skin. A cloverleaf design flap is used for this reconstruction.

Subungual osteochondroma.

Subungual osteochondromas are rare tumors that occur in the toes and fingers. This case report of a large subungual tumor of the right ring finger demonstrates the classic radiologic features and successful management of a large tumor by complete excision of the nail bed and the tumor and reconstruction of the distal nail bed with a split-thickness nail bed graft from the great toe.

Extensor digitorum turn-down muscle flap.

When the extensor digitorum longus--a multisegmentally vascular-supplied muscle--is rotated distally, its origin can be used for covering defects in the lower one-third of the leg. We have used this technique successfully in four consecutive patients, and it has resulted in osteomyelitic cavity obliteration in three and a stable skin coverage in all four.

Aesthetic vaginal labioplasty.

Labia minora that protrude past the labia majora are aesthetically and functionally unsatisfactory to some women. Historically, female circumcision has been practiced in Islamic/Arabic countries for many centuries and is still commonly practiced in these countries. Three case reports present middle-aged women who were dissatisfied with the size and protuberance of the labia minora, and an aesthetic labioplasty was performed in these three women. The technical aspects of this procedure are outlined, and a representative case with 3-month follow-up is presented pictorially.

Mild head injury--a positive approach to management.

It is estimated that 1.4 million patients each year attend Accident and Emergency (A&E) departments in the UK with a head injury. The vast majority are, in retrospect, diagnosed as a 'mild' injury. There is evidence to suggest that many develop short term morbidity and some long term problems. The incidence is unknown. Early recognition and treatment many hasten recovery. A national postal survey of A&E departments revealed a general unawareness for this morbidity. Written advice given to patients on discharge from the departments was exclusively concerned with the symptoms expected if serious complications developed. A description of the common symptoms of fatigue, poor memory and concentration were not given to the patients in a written format. Arrangements for follow up are, in the majority of hospitals, unstructured. We recommend a positive approach to the management and follow up of mild head injury. This should recognize the common problems experienced by these patients and cater for their needs. More interest and research is required into this aspect of head injury.

ABC of emergency radiology. The wrist.

History including detailed mechanism of injury. Meticulous clinical examination. Appropriate radiograph and systematic assessment.

Doctors' legal position in treating temporarily incompetent patients.

Doctors in accident and emergency departments are sometimes presented with patients with potentially life threatening conditions who refuse to consent to treatment. The doctors then face a dilemma: to withhold necessary treatment or to act against a patient's express wishes. Two such cases are presented, and we asked a lawyer, two medical ethicists, a psychiatrist, and an accident and emergency physician to comment on the implications.

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.