Silicate dissolution boosts the CO2 concentrations in subduction fluids.

Estimates of dissolved CO2 in subduction-zone fluids are based on thermodynamic models, relying on a very sparse experimental data base. Here, we present experimental data at 1-3 GPa, 800 °C, and ∆FMQ ≈ -0.5 for the volatiles and solute contents of graphite-saturated fluids in the systems COH, SiO2-COH ( + quartz/coesite) and MgO-SiO2-COH ( + forsterite and enstatite). The CO2 content of fluids interacting with silicates exceeds the amounts measured in the pure COH system by up to 30 mol%, as a consequence of a decrease in water activity probably associated with the formation of organic complexes containing Si-O-C and Si-O-Mg bonds. The interaction of deep aqueous fluids with silicates is a novel mechanism for controlling the composition of subduction COH fluids, promoting the deep CO2 transfer from the slab-mantle interface to the overlying mantle wedge, in particular where fluids are stable over melts.Current estimates of dissolved CO2 in subduction-zone fluids based on thermodynamic models rely on a very sparse experimental data base. Here, the authors show that experimental graphite-saturated COH fluids interacting with silicates at 1-3 GPa and 800 °C display unpredictably high CO2 contents.

Morphometric evaluation of sesamoid bones of the first metacarpophalangeal joint with ultrasound.

OBJECTIVE: The purpose of our study is to demonstrate the role of ultrasound as a first-line technique in the evaluation of sesamoid bones of the first metacarpophalangeal joint. MATERIALS AND METHODS: In a 2 years period, we enrolled 117 healthy people, 60 men and 57 women, age range 24-35 years, mean 29 ± 4. We analysed both their ulnar and radial sesamoid bones within the metacarpophalangeal joint of the 1st finger of the dominant hand. RESULTS: For each sesamoid we measured the short and long axes diameter (mm); additionally, the relation between these parameters was used to calculate the Sesamoid Index, a classic radiographic index generally used to obtain volumetric information on the sesamoids. Additionally, we introduced and measured another index (the "Subsesamoid Index"), which we believe might be useful to measure the subsesamoid joint space. CONCLUSIONS: Ultrasound is able to provide all the anatomic information needed during the evaluation of sesamoid bones, thus replacing conventional radiography as the first-line diagnostic approach.

The intersection syndrome: Ultrasound findings and their diagnostic value.

INTRODUCTION: The intersection syndrome is a well-known overuse syndrome of the distal forearm. It is characterized by noninfectious, inflammatory changes involving the area of intersection of the first (abductor pollicis longus and extensor pollicis brevis) and second (extensor carpi radialis longus and extensor carpi radialis brevis) extensor compartments in the dorsoradial aspect of the distal forearm. Imaging modalities used to diagnosis this syndrome include ultrasonography (US) and magnetic resonance imaging. The purpose of this report is to describe typical US findings in the intersection syndrome and to demonstrate the diagnostic value of this approach. MATERIALS AND METHODS: We reviewed US findings in 4 patients (mean age 40 years) referred to our staff for symptoms suggestive of the intersection syndrome (pain, swelling, erythema, and edema of the wrist). RESULTS: In all 4 cases, the US examination revealed peritendinous edema and synovial fluid within the tendon sheaths at the intersection between the first and the second dorsal extensor tendon compartments. DISCUSSION: Our experience shows that the intersection syndrome is associated with typical signs on US. This imaging modality can be considered a reliable tool for diagnosing this syndrome and may eliminate the need for other more expensive tests.

Ultrasound picture of a wooden splinter evolved in phlegmon of the hand.

INTRODUCTION: To demonstrate the usefulness of ultrasound (US) in quickly and effectively diagnosing the presence of a foreign body in the superficial soft tissues. MATERIALS AND METHODS: A young lumberjack underwent US examination due to pain and swelling of the back of his right hand. These symptoms are often due to the presence of a wooden splinter. RESULTS: On the back of the right hand, US demonstrated a hyperechoic line with acoustic shadowing surrounded by a hypoechoic halo suggesting a foreign body. Next to it in the same area, several hypoechoic areas were observed. CONCLUSIONS: US can quickly identify the exact position of a foreign body embedded in the skin and soft tissues; US can furthermore provide information about the inflammatory process and its spreading.