Author Correction: Forearc carbon sink reduces long-term volatile recycling into the mantle.

Change history: In this Article, the original affiliation 2 was not applicable and has been removed. In addition, in the Acknowledgements there was a statement missing and an error in a name. These errors have been corrected online.

Forearc carbon sink reduces long-term volatile recycling into the mantle.

Carbon and other volatiles in the form of gases, fluids or mineral phases are transported from Earth's surface into the mantle at convergent margins, where the oceanic crust subducts beneath the continental crust. The efficiency of this transfer has profound implications for the nature and scale of geochemical heterogeneities in Earth's deep mantle and shallow crustal reservoirs, as well as Earth's oxidation state. However, the proportions of volatiles released from the forearc and backarc are not well constrained compared to fluxes from the volcanic arc front. Here we use helium and carbon isotope data from deeply sourced springs along two cross-arc transects to show that about 91 per cent of carbon released from the slab and mantle beneath the Costa Rican forearc is sequestered within the crust by calcite deposition. Around an additional three per cent is incorporated into the biomass through microbial chemolithoautotrophy, whereby microbes assimilate inorganic carbon into biomass. We estimate that between 1.2 × 108 and 1.3 × 1010 moles of carbon dioxide per year are released from the slab beneath the forearc, and thus up to about 19 per cent less carbon is being transferred into Earth's deep mantle than previously estimated.

Author Correction: Forearc carbon sink reduces long-term volatile recycling into the mantle.

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.

Discharge patterns of hindlimb motoneurons during normal cat locomotion.

Long-term recording from single lumbar motoneurons of intact cats revealed activation patterns fundamentally different from those seen in decerebrate preparations. In intact cats, motoneuron bursts showed marked rate modulation without initial doublets. Each unit's frequencygram generally resembled the envelope of the gross electromyogram simultaneously recorded from the corresponding muscle. Average and peak discharge rates increased for faster gaits. These findings suggest that, in cat locomotion, rate modulation is a more important contributor to force regulation than was previously thought.

Factors influencing the occurrence of multicentric and 'recurrent' Warthin's tumour: a cross sectional study.

The multicentric nature of Warthin's tumour has been well recognised, though the factors predicting its occurrence and its influence on management remain speculative. In this cross sectional study, the authors analysed the presentation, management and outcome of solitary and multicentric Warthin's tumour, treated in the maxillofacial unit and investigated factors that could influence the occurrence of multicentric and recurrent tumours. Warthin's tumour was found in 24% (150/628) of patients presenting with parotid neoplasms and multicentric tumours were found in 13% (21/ 161) of parotidectomy specimens. Age, sex, side, site and smoking history were not predictors of multicentricity (P>0.40). Clinical examination (19%), imaging investigations (28%) and intra-operative palpation (33%) were poor at detecting multicentric tumours. Superficial parotidectomy was the most commonly performed operation. The recurrence rate was 0% in the solitary and 10% in the multicentric tumour group. Intra-operative rupture was not uncommon (11%), but was not associated with tumour recurrence (P= or >0.999). Incomplete excision (P=0.007) and multicentricity (P=0.026) were predictors of recurrence.

Multiple synchronous and metachronous neoplasms of the parotid gland: the Chichester experience.

Parotid neoplasms are usually solitary and multiple tumours occurring in an individual are uncommon. The incidence and implications of multiple synchronous and metachronous tumours remains relatively unknown. We reviewed the case notes of 606 patients who had parotidectomies for neoplastic lesions over a 30 year period and identified 30 patients (5%) with multiple primary tumours. There were 24 patients with synchronous tumours and 6 with metachronous tumours. Sixteen of the synchronous tumours (67%) were ipsilateral, whereas all six metachronous tumours were contralateral. Preoperative examination was effective at detecting bilateral tumours but poor at detecting multiple ipsilateral tumours. Multiple tumours were likely to be of the same histology (n=24, 80%) and Warthin's was by far the most common multiple tumour. Ipsilateral tumours of differing histological types and identical tumours other than Wartin's were uncommon. All but one patient had superficial parotidectomies and there were no recurrences.

A multiple-contact EMG recording array for mapping single muscle unit territories.

The glycogen-depletion technique has become a well-established method for determining histologically the cross-sectional distribution of a single muscle unit. A major drawback of this method is its low yield of one depleted unit per experiment. Furthermore, this technique is particularly unsuited for determining the longitudinal distribution of single muscle units in long, broad muscles because of the formidable serial sectioning job that would be required. Our alternative, electrophysiological method utilizes a multiple-contact, two-dimensional EMG recording array to map efficiently the cross-sectional and longitudinal distributions of numerous single muscle units in anatomically diverse muscles. Additionally, architectural information on muscle fiber lengths, end-plate locations, motor subunit (MSU) arrangements and muscle conduction velocities can be determined.

Single unit conduction velocities from averaged nerve cuff electrode records in freely moving cats.

The conduction velocity of peripheral neurons recorded by wire microelectrodes implanted in intact, freely moving cats was determined on-line using the technique of spike-triggered averaging of nerve cuff electrode records described here. Axonal velocity was estimated from the conduction latency between two adjacent sets of tripolar recording electrodes inside a cuff, thereby avoiding uncertainties that could arise from differences in spike shape, variable conduction distance, or unknown stimulus utilization time. This method rendered conduction velocity values for individual afferent and efferent myelinated fibers ranging from 27 to 120 m/sec, estimated with an uncertainty of +/-5%. In addition, predictions from theoretical models relating extracellular potential amplitude, wavelength, and conduction velocity were confirmed experimentally for en passant records obtained from intact myelinated fibers.

Cross-correlation of EMG reveals widespread synchronization of motor units during some slow movements in intact cats.

It is commonly assumed that the motor units comprising a single mammalian muscle will be recruited asynchronously at subtetanic firing rates to produce smoothly modulated force output. However, electromyograms from certain neck muscles, recorded by implanted bipolar "patch" electrodes having large contacts, often exhibited a rhythmic clustering of spike activity whose patterns suggested that motor-unit firing was synchronized both within and across muscles. We have developed a computerized processing system that digitizes EMG activity and calculates auto- and cross-correlation products of selected segments. The presence or absence of synchronization caused by neural mechanisms can be identified and differentiated from that due to the rhythmicity of the behavior itself (e.g. shaking) or due to cross-talk, according to the shapes of the resultant correlograms. These methods have so far been applied to the study of hindlimb and neck muscle EMG during various natural motor behaviors, but they provide a general, quantitative tool for the study of an important aspect of motor control that may be overlooked by conventional sampling and smoothing techniques.

Nutrition knowledge and concerns of health and physical education teachers.

The results indicated that most (80%) of the teachers were fairly knowledgeable about the nutrition needs of athletes. However, while many teachers agreed that carbohydrates and fats were the main sources of muscular energy, 35% indicated that protein was the primary source of energy for muscular activity. Also, 12% agreed that the consumption of salt tablets during athletic events prevents muscle cramps. The results suggest nutrition education for HPE teachers is needed. Information provided to HPE teachers should address their three main nutrition concerns, which are a balanced diet for athletes, weight control, and fluid replacement.

Distribution and innervation of short, interdigitated muscle fibers in parallel-fibered muscles of the cat hindlimb.

The cat hindlimb contains several long, biarticular strap muscles composed of parallel muscle fascicles that attach to short tendons. Three of these muscles--sartorius, tenuissimus, and semitendinosus--were studied by dissecting individual gold-stained fibers and determining the surface distribution of acetylcholinesterase-stained end-plate zones. In each muscle, fascicles were composed of muscle fibers that ran only part of the fascicle length and tapered to end as fine strands that interdigitated with other tapering fibers within the muscle mass. Most muscle fibers measured 2-3 cm in length. Fascicles of muscle fibers were crossed by short transverse bands of endplates (1 mm wide by 1-5 mm long) that were spaced at fairly regular intervals from the origin to the insertion of the muscle. The endplate pattern suggested that the fiber fascicles were organized into multiple longitudinal strips. In the sartorius, the temporospatial distribution of electromyographic (EMG) activity evoked by stimulating fine, longitudinal branches of the parent nerve confirmed that each strip was selectively innervated by a small subset of the motor axons. These axons appeared to distribute their endings throughout the entire length of the fascicles, providing for synchronous activation of their in-series fibers.

Changing frequency of parotid gland neoplasms--analysis of 560 tumours treated in a district general hospital.

An analysis of all parotidectomies performed for neoplastic lesions in the maxillofacial unit at a district general hospital during a 26-year period between 1974-1999 was undertaken. The details analysed were age, sex, histology and temporal variations in the frequency of specific tumour types during the study period. A total of 538 parotidectomies performed on 529 patients in whom 560 tumours were present, formed the basis of this study. Marked variations were present in the age and sex distribution and relative frequency of specific tumour types in this study, when compared to previous reports. There were also differences in the age and sex distribution of pleomorphic adenoma and adenolymphoma (P <0.0001) in this study. The relative frequency of benign tumours and adenolymphoma increased, whereas that of pleomorphic adenoma decreased during the study period. In addition, there was a statistically significant decrease in the relative frequency of pleomorphic adenoma (P <0.0001) and an increase in adenolymphoma (P <0.0001) when comparisons were made with previous studies. This study from a defined population may be more representative of the true proportion of specific tumours in this population. The potential implications of the results on the investigation and treatment of parotid neoplasms is highlighted.

Labial sensory function following sagittal split osteotomy.

A retrospective assessment of labial sensory function following sagittal split osteotomy was undertaken by a combination of record analysis, postal questionnaire and objective sensory testing. Case records for 90 sides operated upon by a single consultant surgeon between 1979 and 1992 identified a prevalence of persisting sensory changed at 2 years of 6.7%. A higher incidence of sensory change was seen in patients treated with intermaxillary fixation/upper border wires than those managed with buccal monocortical miniplates. Postal questionnaire returns for 67 consultant operated sides identified a higher incidence of sensory change than recorded in the notes. 5.9% had long term persisting anaesthesia. Another 28% had more variable subtle sensory impairment. A similar relation to method of fixation was seen. An association between duration of temporary sensory change and magnitude of forward mandibular advance was noted. Objective sensory testing validated the subjectively reported sensory status but also identified many patients self-assessed as normal had some undetected sensory impairment. Possible mechanisms for the above findings and implications for clinical practice are presented.

Controversies in third molar surgery--the national view on review strategies.

A national survey was conducted to establish the current practice of postoperative review of third molar surgery by the 255 fellows of the British Association of Oral and Maxillofacial Surgeons. Of the 216 complete responses, 134 say that they routinely reviewed all patients, while 67 did not. A further 15 fellows (7%) are currently considering their practice. Five (2%) stated that routine review should be compulsory and failure to do so was medically negligent. We conclude that a policy of selective rather than routine review is safe for most patients, but if a patient is under age, mentally retarded, taking psychoactive drugs, or has any other associated condition, then routine follow-up should be undertaken.

Surgical management of incompletely excised basal cell carcinomas of the head and neck.

We made a retrospective audit of all basal cell carcinomas excised in the Maxillofacial Units at St. Richard's Hospital, Chichester and the Worthing and Southlands NHS Trust between 1990 and 1999. A total of 3795 BCCs were excised. Of these, 3560 were completely excised (93.8%) and 235 were incompletely excised (6.2%), which compares favourably with other series. Of these, 84 patients had further excision, 11 had radiotherapy, and 140 were kept under review. Residual tumour was present in 45% of the re-excised specimens. Of the 140 cases managed by observation, 21% recurred. Notably, 31% of patients in the observation cohort died of other causes without recurrence. Incomplete excision was significantly more likely (P < 0.001) if multiple lesions were excised at the time of operation. Involvement of multiple margins was not a significant risk factor for recurrence in the 'observed' cohort. This study shows that a flexible strategy, which balances observation, further excision and radiotherapy, is superior to any single approach.

Michigan physicians' perceptions of their role in managing obesity.

In a random sample of 211 primary-care physicians in Michigan, about 33% (n = 70) perceived their role in the prevention of obesity as coordinating and 39% (n = 82) as cooperative and of equal importance to that of other professionals. Perceived barriers to prevention of obesity were inadequate time to educate patients, method of reimbursement, and inadequate training in management of obesity. These results suggest that physicians' involvement in managing obesity can improve if they work closely with other health professionals.

A multivariate analysis of weight-loss behavior.

This study used a theoretical framework with multiple variables in multivariate analyses (factor, multiple regression, and path analyses) to investigate the sociopsychological predictors of weight loss. Responses from 309 participants of a comprehensive weight-loss program indicated that self-assurance was the most significant predictor of actual weight loss, followed by weeks completed. Other factors, such as program satisfaction and perceived importance, indirectly predicted weight loss through the intervening variables of self-assurance and weeks completed. Differences in the factors predicting weight loss were observed between completers and dropouts. The implications of these results for professionals concerned with weight control are discussed.

Pentoxifylline and tocopherol in the management of patients with osteoradionecrosis, the Portsmouth experience.

Osteoradionecrosis of the jaw remains the most problematic consequence of radiotherapy for the management of head and neck cancer. Treatment is often complex and multimodal. New theories on its pathophysiology have allowed the development of potential treatment modalities, including the use of pentoxifylline and tocopherol. In this retrospective case series we examined the outcomes of patients with ORN prescribed pentoxifylline and tocopherol.