Optical radiation from the interaction of energetic atoms, ions, electrons, and photons with surfaces

Heavy particle, electron, and UV photon bombardment of solid surfaces has been recently observed to result in the emission of infrared, visible, and ultraviolet radiation. This effect occurs over a wide range of incident projectile energies. Line radiation arising from transitions between discrete atomic or molecular levels may be attributed to the decay of excited particles which have been sputtered or electronically/chemically desorbed from the surface. Broadband continuum radiation, which is also observed, is believed to arise either from fluorescence of the near surface bulk or from the radiative decay of desorbed excited clusters. Spacecraft, in the ambient near Earth environment, are subject to such bombardment. The dynamics of energetic particle and photon beam interactions with surfaces which lead to surface erosion and glow phenomena will be treated. In addition, projected experimental and theoretical studies of oxygen and nitrogen beam surface interactions on materials characteristic of spacecraft surfaces will be discussed

The production of low-energy neutral oxygen beams by grazing-incidence neutralization

The Vanderbilt University neutral oxygen facility produces beams of low-energy neutral oxygen atoms by means of grazing-incidence collisions between ion beams and metal surfaces. Residual ions are reflected by applied electric fields. This method can utilize initial ion beams of either O(+) or O2(+) since a very large percentage of molecular oxygen ions are dissociated when they undergo grazing-incidence neutralization. The method of neutralization is applicable to low-energy beams and to all ions. Particular emphasis is on O and N2 beams for simulation of the low Earth orbit space environment. Since the beam is a pure O-neutral beam and since measurements of the interaction of the beam with solid surfaces are made spectroscopically, absolute reaction rates can be determined. The technique permits the beams to be used in conjunction with electron and photon irradiation for studies of synergistic effects. Comparisons of optical spectra of Kapton excited by 2.5-keV O, O(+), and O2(+) show significant differences. Optical spectra of Kapton excited by neutral oxygen beams of less than 1 keV have been recorded

Impact of pasireotide on postoperative pancreatic fistulas following distal resections

Purpose Postoperative pancreatic fistula (POPF), a difficult complication after surgery, can cause peripancreatic fluid collection and infections in the operative area. In addition, pancreatic fluid is corrosive and can lead to postoperative bleeding. Clinically significant grade B and C fistulas (CR-POPF) increase postoperative morbidity, resulting in a prolonged hospital stay. Delaying adjuvant therapy due to fistula formation in cancer patients can affect their prognosis. In this study, we aimed to determine if pasireotide affects fistula formation, and the severity of other complications in patients following pancreatic distal resections. Data and methods Between 2000 and 2016, 258 distal pancreatectomies were performed at Helsinki University Hospital and were included in our analysis. Pasireotide was administered to patients undergoing distal resections between July 2014 and December 2016. Patients received 900-mu g pasireotide administered twice daily perioperatively. Other patients who received octreotide treatment were analyzed separately. Complications such as fistulas (POPF), delayed gastric emptying (DGE), postpancreatectomy hemorrhage (PPH), reoperations, and mortality were recorded and analyzed 90 days postoperatively. Results Overall, 47 (18%) patients received pasireotide and 31 (12%) octreotide, while 180 patients (70%) who received neither constituted the control group. There were 40 (16%) clinically relevant grade B and C POPFs: seven (15%) in the pasireotide group, three (10%) in the octreotide group, and 30 (17%) in the control group (p = 0.739). Severe complications categorized as Clavien-Dindo grade III or IV were recorded in 64 (25%) patients: 17 (27%) in the pasireotide group, 4 (6%) in the octreotide group, and 43 (67%) in the control group (p = 0.059). We found no 90-day mortality. Conclusions In this study, pasireotide did not reduce clinically relevant POPFs or severe complications following pancreatic distal resection.Peer reviewe

Ultrafast Insulator-Metal Phase Transition in VO2 Studied by Multiterahertz Spectroscopy

The ultrafast photoinduced insulator-metal transition in VO2 is studied at different temperatures and excitation fluences using multi-THz probe pulses. The spectrally resolved mid-infrared response allows us to trace separately the dynamics of lattice and electronic degrees of freedom with a time resolution of 40 fs. The critical fluence of the optical pump pulse which drives the system into a long-lived metallic state is found to increase with decreasing temperature. Under all measurement conditions we observe a modulation of the eigenfrequencies of the optical phonon modes induced by their anharmonic coupling to the coherent wave packet motion of V-V dimers at 6.1 THz. Furthermore, we find a weak quadratic coupling of the electronic response to the coherent dimer oscillation resulting in a modulation of the electronic conductivity at twice the frequency of the wave packet motion. The findings are discussed in the framework of a qualitative model based on an approximation of local photoexcitation of the vanadium dimers from the insulating state.Comment: 10 pages, 8 figures submitted to Physical Review

Prognostic and diagnostic value of REG4 serum and tissue expression in pancreatic ductal adenocarcinoma

Expression of regenerating islet-derived protein 4 (REG4), a secretory protein involved in cell differentiation and proliferation, is upregulated in inflammatory bowel diseases and in many gastrointestinal malignancies. The prognostic significance of its expression in pancreatic ductal adenocarcinoma is unknown. Our aim was to investigate tumor tissue and serum REG4 expression in pancreatic ductal adenocarcinoma patients. We also evaluated as a control the diagnostic value of serum REG4 level in patients with chronic pancreatitis. Immunohistochemical expression of REG4 was evaluated in 154 surgical specimens and serum REG4 level in 130 samples from pancreatic ductal adenocarcinoma patients treated at Helsinki University Hospital, Finland, in 2000–2011. REG4 tissue and serum expression was assessed in relation to clinicopathological parameters and patient survival. A chronic pancreatitis control group comprised 34 patients who underwent pancreatic resection because of suspicion of malignancy. Significant survival differences were detectable in subgroups: in tumor stages IA–IIA, high serum REG4 level predicted worse survival (p=0.046). In patients with grade I tumor, positive tissue REG4 expression predicted better survival (p=0.006). In multivariate analysis, neither tissue nor serum REG4 expression was independent prognostic factors. Serum REG4 levels were higher in pancreatic ductal adenocarcinoma than in chronic pancreatitis (p=0.002), with diagnostic sensitivity of 45% and specificity of 91%. In logistic regression analysis, a multivariate model with REG4, CA19-9, and age provided sensitivity of 82% and specificity of 79%. REG4 tissue expression is a prognostic marker in subgroups of pancreatic ductal adenocarcinoma patients. Serum REG4 level might be useful in differential diagnosis between pancreatic ductal adenocarcinoma and chronic pancreatitis. © 2018, © The Author(s) 2018.Peer reviewe

Immunohistochemical Expression of Somatostatin Receptor Subtypes in a Panel of Neuroendocrine Neoplasias

Neuroendocrine neoplasias (NENs) are known to express somatostatin receptors (SSTRs) 1-5, which are G-protein-coupled cell membrane receptors. Somatostatin receptor imaging and therapy utilizes the SSTR expression. Synthetic somatostatin analogs with radioligands are used to detect primary tumors, metastases, and recurrent disease. Receptor analogs are also used for treating NENs. Furthermore, commercially available SSTR antibodies can be used for the immunohistochemical (IHC) detection of SSTRs. We investigated different SSTR antibody clones applying diverse IHC protocol settings to identify reliable clones and feasible protocols for NENs. A tissue microarray including NENs from 12 different primary sites were stained. Only UMB clones were able to localize SSTR on the cell membranes of NENs. SSTR2 (UMB1) emerged as the most common subtype followed by SSTR5 (UMB4) and SSTR1 (UMB7). SSTR3 (UMB5) expression was mainly cytoplasmic. Yet, SSTR4 expression was weak and located primarily in the cytoplasm. Thus, appropriate IHC protocols, including proper positive and negative controls, represent requirements for high-quality NEN diagnostics and for planning personalized therapy.Peer reviewe