Surface composition of Hyperion.

Hyperion, Saturn's eighth largest icy satellite, is a body of irregular shape in a state of chaotic rotation. The surface is segregated into two distinct units. A spatially dominant high-albedo unit having the strong signature of H2O ice contrasts with a unit that is about a factor of four lower in albedo and is found mostly in the bottoms of cup-like craters. Here we report observations of Hyperion's surface in the ultraviolet and near-infrared spectral regions with two optical remote sensing instruments on the Cassini spacecraft at closest approach during a fly-by on 25-26 September 2005. The close fly-by afforded us the opportunity to obtain separate reflectance spectra of the high- and low-albedo surface components. The low-albedo material has spectral similarities and compositional signatures that link it with the surface of Phoebe and a hemisphere-wide superficial coating on Iapetus.

A dynamic upper atmosphere of Venus as revealed by VIRTIS on Venus Express.

The upper atmosphere of a planet is a transition region in which energy is transferred between the deeper atmosphere and outer space. Molecular emissions from the upper atmosphere (90-120 km altitude) of Venus can be used to investigate the energetics and to trace the circulation of this hitherto little-studied region. Previous spacecraft and ground-based observations of infrared emission from CO2, O2 and NO have established that photochemical and dynamic activity controls the structure of the upper atmosphere of Venus. These data, however, have left unresolved the precise altitude of the emission owing to a lack of data and of an adequate observing geometry. Here we report measurements of day-side CO2 non-local thermodynamic equilibrium emission at 4.3 microm, extending from 90 to 120 km altitude, and of night-side O2 emission extending from 95 to 100 km. The CO2 emission peak occurs at approximately 115 km and varies with solar zenith angle over a range of approximately 10 km. This confirms previous modelling, and permits the beginning of a systematic study of the variability of the emission. The O2 peak emission happens at 96 km +/- 1 km, which is consistent with three-body recombination of oxygen atoms transported from the day side by a global thermospheric sub-solar to anti-solar circulation, as previously predicted.

South-polar features on Venus similar to those near the north pole.

Venus has no seasons, slow rotation and a very massive atmosphere, which is mainly carbon dioxide with clouds primarily of sulphuric acid droplets. Infrared observations by previous missions to Venus revealed a bright 'dipole' feature surrounded by a cold 'collar' at its north pole. The polar dipole is a 'double-eye' feature at the centre of a vast vortex that rotates around the pole, and is possibly associated with rapid downwelling. The polar cold collar is a wide, shallow river of cold air that circulates around the polar vortex. One outstanding question has been whether the global circulation was symmetric, such that a dipole feature existed at the south pole. Here we report observations of Venus' south-polar region, where we have seen clouds with morphology much like those around the north pole, but rotating somewhat faster than the northern dipole. The vortex may extend down to the lower cloud layers that lie at about 50 km height and perhaps deeper. The spectroscopic properties of the clouds around the south pole are compatible with a sulphuric acid composition.

Phyllosilicates on Mars and implications for early martian climate.

The recent identification of large deposits of sulphates by remote sensing and in situ observations has been considered evidence of the past presence of liquid water on Mars. Here we report the unambiguous detection of diverse phyllosilicates, a family of aqueous alteration products, on the basis of observations by the OMEGA imaging spectrometer on board the Mars Express spacecraft. These minerals are mainly associated with Noachian outcrops, which is consistent with an early active hydrological system, sustaining the long-term contact of igneous minerals with liquid water. We infer that the two main families of hydrated alteration products detected-phyllosilicates and sulphates--result from different formation processes. These occurred during two distinct climatic episodes: an early Noachian Mars, resulting in the formation of hydrated silicates, followed by a more acidic environment, in which sulphates formed.

Compositional maps of Saturn's moon Phoebe from imaging spectroscopy.

The origin of Phoebe, which is the outermost large satellite of Saturn, is of particular interest because its inclined, retrograde orbit suggests that it was gravitationally captured by Saturn, having accreted outside the region of the solar nebula in which Saturn formed. By contrast, Saturn's regular satellites (with prograde, low-inclination, circular orbits) probably accreted within the sub-nebula in which Saturn itself formed. Here we report imaging spectroscopy of Phoebe resulting from the Cassini-Huygens spacecraft encounter on 11 June 2004. We mapped ferrous-iron-bearing minerals, bound water, trapped CO2, probable phyllosilicates, organics, nitriles and cyanide compounds. Detection of these compounds on Phoebe makes it one of the most compositionally diverse objects yet observed in our Solar System. It is likely that Phoebe's surface contains primitive materials from the outer Solar System, indicating a surface of cometary origin.

Release of volatiles from a possible cryovolcano from near-infrared imaging of Titan.

Titan is the only satellite in our Solar System with a dense atmosphere. The surface pressure is 1.5 bar (ref. 1) and, similar to the Earth, N2 is the main component of the atmosphere. Methane is the second most important component, but it is photodissociated on a timescale of 10(7) years (ref. 3). This short timescale has led to the suggestion that Titan may possess a surface or subsurface reservoir of hydrocarbons to replenish the atmosphere. Here we report near-infrared images of Titan obtained on 26 October 2004 by the Cassini spacecraft. The images show that a widespread methane ocean does not exist; subtle albedo variations instead suggest topographical variations, as would be expected for a more solid (perhaps icy) surface. We also find a circular structure approximately 30 km in diameter that does not resemble any features seen on other icy satellites. We propose that the structure is a dome formed by upwelling icy plumes that release methane into Titan's atmosphere.

[Peutz-Jeghers syndrome: case report and update on diagnosis and treatment]. / Sindrome di Peutz-Jeghers. Caso clinico ed attualità diagnostico-terapeutiche.

Peutz-Jeghers syndrome is a rare autosomal dominantly inherited condition with an incidence of 1/120.000 liveborns, characterized by the presence of hamartomatous gastrointestinal polyps and mucocutaneous pigmentation. This syndrome predisposes to various clinical problems such as intussusception and cancer development in different loci (gastrointestinal tract, breast and ovary). For this reason, PJS patients should undergo a surveillance protocol of the genital and gastrointestinal apparatus. Therefore, the early diagnosis of PJS in at-risk family members is very important in preventing cancer development. Germline mutations within the LKB1 or Serine Threonine Kinase (STK11) gene, located on chromosome 19p13.3, are responsible for most cases of PJS so far studied. The existence of a second locus is suspected on chromosome 19q13.4 in a minority of families. The LKB1 gene, recently cloned, encodes the Serine Threonine Kinase LKB1 and is ubiquitously expressed. The identification of the disease-causing mutation in each family makes it possible to perform a presymptomatic diagnosis; therefore, only the mutation carriers will undergo the clinical surveillance program. In this paper, the case of a PJS patient who has been surgically treated is presented. The DNA screening of the LKB1 gene in this patient has led to the identification of the causing mutation. A critical review of the literature and is also presented as well as the proposal to establish an Italian Registry of PJS.

[Current problems of the surgical treatment of rectal cancer: analysis of the literature and personal experience]. / Problematiche attuali nella terapia chirurgica del cancro del retto: analisi della letteratura ed esperienza personale.

The surgical procedure is a crucial factor in preventing local recurrence in rectal cancer, and total mesorectal excision (TME) particularly is widely accepted as being associated with a decreased local recurrence rate. In this study, concerning 187 patients with rectal cancer, we compare conventional surgery, performed in 140 patients from 1979 to 1993, with a standardised TME procedure in 47 patients over the period from 1994 to 1998. The first group not treated by TME were operated on for 56 (40%) tumours of the upper rectum and 84 (60%) of the lower rectum; 35 (25%) were Dukes' A, 77 Dukes' B and 28 (20%) Dukes' C. 42 abdominoperineal amputations (30%) and 98 anterior resections (70%) were performed. The second group in which TME was performed comprised 17 (36%) tumours of the upper rectum and 30 (64%) of the lower rectum, 8 (17%) in stage I AJCC (Dukes' A), 16 (34%) in II (B) and 23 (49%) in III (C). 9 abdominoperineal amputations (19%) and 38 anterior resections (81%) were performed, 8 (21%) with an ultra-low anastomosis. In the first group of patients we observed 28 local recurrences (20%) and a 5-year disease-free survival in 50% of cases. In the second group we achieved a decreased rate of local recurrence (10.6%) which is about half that observed after conventional surgery, but there was no significant difference in survival. These data confirm the effectiveness of TME in reducing local recurrence rate, according to the literature; in future this procedure can get to reconsider the role of adjuvant therapy in the management of rectal cancer.

[Conservative treatment of a large retroperitoneal hematoma following extracorporeal shock wave lithotripsy (ESWL): case report and literature review]. / Trattamento conservativo di voluminoso ematoma retroperitoneale (ERP) secondario a litotripsia renale ad onde d'urto (ESWL): case report e revisione della letteratura.

Retroperitoneal and subcapsular renal hematomas, following extracorporeal shock wave lithotripsy (ESWL) occur rarely, but the large number of this treatment performed has to be considered. The knowledge of risk factors, natural history and complications represents a crucial factor in the correct management of these lesions, that generally must be treated conservatively, monitoring clinical parameters and eco-TC diameters of the hematoma. Surgical approache is indicated only in case of haemodinamic instability not responsive to medical therapy and, after 1-2 months, to try to improve renal disfunction due to compression. In this paper we present a case of retroperitoneal hematoma after ESWL and review the literature, so as to define the management of these lesions.

[Cystadenoma of the pancreas: the clinical and preoperative diagnostic problems]. / Il cistoadenoma del pancreas: problemi di clinica e diagnosi preoperatoria.

Pancreatic cystadenomas must be considered in the differential diagnosis of all cystic neoplasms of the pancreas. On the basis of a clinical observation, the authors discuss the most important clinical and diagnostic findings of pancreatic cystadenomas with special regard for what concerns the mucinous type. The authors underline the extreme difficulty of a correct preoperative diagnosis and discuss, after a wide literature review, the utility and the validity of the various imaging, cytological and immunohistochemical preoperative diagnostic procedures. In most cases the final diagnostic confirmation comes from the histology on the resected specimen; therefore all cystic neoplasms, no matter their location within the gland, which are not clearly identified pre or intraoperatively, should be surgically treated and removed.

[Urgent management of obstructing colo-rectal cancer: authors' experience]. / Trattamento in urgenza delle occlusioni intestinali da cancro del colon-retto: nostra esperienza.

PURPOSE: The aim of this retrospective study is to compare the different surgical approaches in obstructing colo-rectal cancer in terms of mortality, morbidity and quality of life. MATERIALS AND METHODS: We observed 379 patients with colorectal cancer, 354 of which underwent surgical treatment, 189 M (53.4%) and 165 F (46.6%), with a median age of 72.6 years. Complicated tumors were 150 (42.4%), with 126 obstructions (84%). For 95 obstructing left-sided colorectal cancers we performed: 9 defunctioning colostomies; 62 two-stages operations: 55 Hartmann's procedures, 5 primary anastomosis with colostomy; 2 primary anastomosis with on table wash-out and ileostomy; 24 single-stage operations: 17 primary anastomosis with on table wash-out and 7 colectomy. RESULTS: The overall operative mortality rate was 8.7% (11/126). The overall leak rate was 8% (5/62), 12.9% (4/31) in left colon and 3.2% (1/31) in right colon, all treated conservatively. The wound infection rate was 23.8% (30/126). DISCUSSION AND CONCLUSIONS: Obstructing colo-rectal cancer is associated with a high operative mortality and a worse prognosis. Defunctioning colostomy can be regarded as a valid option only in extreme circumstances. Hartmann's operation has indicated in case of metastatic disease, unsure anastomosis, simultaneous colonic perforation. The gold-standard is primary anastomosis, as colonic resection with on table wash-out or subtotal/total colectomy, in case of largely distended colon or synchronous lesions.

Composition and physical properties of Enceladus' surface.

Observations of Saturn's satellite Enceladus using Cassini's Visual and Infrared Mapping Spectrometer instrument were obtained during three flybys of Enceladus in 2005. Enceladus' surface is composed mostly of nearly pure water ice except near its south pole, where there are light organics, CO2, and amorphous and crystalline water ice, particularly in the region dubbed the "tiger stripes." An upper limit of 5 precipitable nanometers is derived for CO in the atmospheric column above Enceladus, and 2% for NH3 in global surface deposits. Upper limits of 140 kelvin (for a filled pixel) are derived for the temperatures in the tiger stripes.

The evolution of Titan's mid-latitude clouds.

Spectra from Cassini's Visual and Infrared Mapping Spectrometer reveal that the horizontal structure, height, and optical depth of Titan's clouds are highly dynamic. Vigorous cloud centers are seen to rise from the middle to the upper troposphere within 30 minutes and dissipate within the next hour. Their development indicates that Titan's clouds evolve convectively; dissipate through rain; and, over the next several hours, waft downwind to achieve their great longitude extents. These and other characteristics suggest that temperate clouds originate from circulation-induced convergence, in addition to a forcing at the surface associated with Saturn's tides, geology, and/or surface composition.

Extrasampling and thermal behavior of diode lasers used as a reference source in a Fourier transform IR spectrometer.

The diode laser is often used as a reference source in an interferometer because its interferogram zero crossings allow for precise intervals to be used for sampling the measured interferogram. The diode laser side modes, the features of which depend on the laser's temperature and power, may generate extra sampling points. The number of extra sampling points is analytically evaluated, and the synthetic spectra are compared with those obtained experimentally using the Planetary Fourier Spectrometer. The conclusion is that the theoretical resolution is guaranteed in practice only when no more than one extra sampling point is generated. This is the case when either the diode laser side mode amplitudes are less than one half of the main mode amplitude or the distance in wave numbers between the side modes and the main mode times the maximum optical path difference is less than 1. Finally, once an appropriate diode laser has been chosen, the actual spectral resolution might be degraded by poor device-operating conditions.