Search

The formation and annihilation behaviors of thermal donors in 16O+‐, 18O+‐, or 16O++12C+‐implanted float‐zone silicon have been investigated with secondary ion mass spectrometry, spreading resistance probe, Hall effect, and transmission electron microscopy. Various oxygen or carbon+oxygen‐implanted samples were laser annealed to remove implant damage and subjected to furnace annealing at 450 °C for up to 100 h to activate oxygen‐related thermal donors. Oxygen concentrations at the peak of the implanted profiles exceed the maximum for Czochralski Si by an order of magnitude. It is found that the third to fourth power dependence of thermal donor formation on oxygen generally observed for Czochralski Si does not hold for the higher oxygen concentration in the implanted layer. Annihilation characteristics of thermal donors formed in the oxygen implanted layers were investigated by the rapid thermal annealing technique. A rapid thermal anneal at 1150 °C for 30 s was required to remove all the thermal donors. Based upon the annihilation kinetics data, it is tentatively concluded that both old and new thermal donors exist in the oxygen‐implanted layer. For carbon+oxygen‐coimplanted samples, the data have shown that carbon greatly increases the new thermal donor concentration in the implanted layer. Finally, precipitate morphologies for both oxygen‐only‐ and carbon+oxygen‐coimplanted samples after a 450 °C furnace annealing were investigated by high resolution electron microscopy. In the case of oxygen‐implant‐only samples, predominant precipitate morphologies are needlelike while platelet defects predominate for carbon+oxygen‐coimplanted samples. Since carbon increases the formation rate of new thermal donors, it is unlikely that they are distinctly related to needlelike precipitates as claimed in previous studies.

The strength of deuterium bonding to the walls of closed cavities within Si was determined in ion-beam experiments. These studies circumvented an inherent indeterminacy in the analysis of external-surface desorption and thereby achieved a quantitative characterization of Si-H surface bonding. The Si-D bond energy for submonolayer coverages is 2.5\ifmmode\pm\else\textpm\fi{}0.2 eV. This value has implications for the reaction path of molecular desorption.

The strength of deuterium bonding to the walls of closed cavities within Si was determined in ion-beam experiments. These studies circumvented an inherent indeterminacy in the analysis of external-surface desorption and thereby allowed the Si-H surface bond energy to be quantified for the first time. The bond energy is 2.5 {plus minus} 0.2 eV for submonolayer coverages. 14 refs., 3 figs.

While primary surgical resection with systematic lymphadenectomy remains the treatment of choice for locoregional Barrett's cancer, neoadjuvant chemotherapy is an increasingly accepted treatment modality for patients with locally advanced tumors and patients with extensive lymphatic spread. In contrast to neoadjuvant radiochemotherapy preoperative chemotherapy alone does not seem to increase peri-operative complications and mortality. Responders to pre-operative treatment clearly have a survival advantage as compared to those who do not respond. The use of positron emission tomography to measure changes in glucose metabolism of the primary tumor can predict response early after initiation of neoadjuvant chemotherapy and thus help to select patients who will or will not benefit from this approach. The best treatment strategy for non-responders to neoadjuvant therapy remains to be defined.

Inclusive measurements of pion production in proton-proton collisions in the forward direction were undertaken at 400 and 600 MeV at the cooler synchrotron (COSY) at Forschungszentrum Julich using the Big Karl spectrograph. The high resolution in the pi(+) momentum ensured that there was an unambiguous separation of the pp ->pi(+)d/pi(+)pn channels. Using these and earlier data, the ratio of the production cross sections could be followed through the Delta region and compared with the predictions of final state interaction theory. Deviations are strongly influenced by long-range terms in the production operator and the tensor force in the final pn system. These have been investigated in a realistic pp ->pi(+)d/pi(+)pn calculation that includes S reversible arrow D channel coupling between the final nucleons. A semiquantitative understanding of the observed effects is achieved. .

We discuss polarizing a proton beam in a storage ring, either by selective removal or by spin flip of the stored ions. Prompted by recent, conflicting calculations, we have carried out a measurement of the spin flip cross section in low-energy electron-proton scattering. The experiment uses the cooling electron beam at COSY as an electron target. The measured cross sections are too small for making spin flip a viable tool in polarizing a stored beam. This invalidates a recent proposal to use co-moving polarized positrons to polarize a stored antiproton beam., 18 pages, 6 figures

Measurements of the pd{yields}p{sub sp}dK{sup +}K{sup -} reaction, where p{sub sp} is a spectator proton, have been undertaken at the Cooler Synchrotron COSY-Juelich by detecting a fast deuteron in coincidence with a K{sup +}K{sup -} pair in the ANKE facility. Although the proton beam energy was fixed, the moving target neutron allowed values of the nonresonant quasifree pn{yields}dK{sup +}K{sup -} total cross section to be deduced up to an excess energy {epsilon}{approx_equal}100 MeV. Evidence is found for the effects of K{sup -}d and KK final state interactions. The comparison of these data with those of pp{yields}ppK{sup +}K{sup -} and pp{yields}dK{sup +}K{sup 0} shows that all the total cross sections are very similar in magnitude.

Electrical transport properties of zone‐melt‐recrystallized Si films of Si‐on‐Insulator wafers were investigated using resistivity and Hall effect measurements between 77 and 300 K. Both graphite strip and cold cathode electron beam methods were used for zone melting which produced high resistivity (≳103 Ω cm at room temperature) recrystallized films. Phosphorus implantation into the silicon films to a dopant level of 1×1016 cm−3 and subsequent annealing at 1100 °C reduced the room‐temperature resistivities to ∼1 Ω cm. Hall mobilities of 950 cm2/V s were observed at room temperature for both materials after the implant anneal sequence. However, for temperatures less than 150 K, the mobility is higher in graphite strip than in electron beam recrystallized films. This behavior is consistent with the relative crystalline qualities of the two films as determined by electron channeling and x‐ray diffraction. It is noteworthy that a deep level was observed at 0.2 eV below the conduction band in the graphite str...

Good quality, low temperature silicon nitride and oxynitride films were deposited downstream from an electron cyclotron resonance (ECR) plasma source using SiH4 and N2 gas mixtures. The Si/N ratio and H content in the deposited films were determined using Rutherford backscattering spectrometry and elastic recoil detection. The H concentration was minimum for films with compositions closest to that of stoichiometric Si3N4. The optimum conditions for producing a stoichiometric Si3N4 were a SiH4/N2 flow ratio between 0.1 and 0.2, and an electrically isolated sample far from the ECR source. Infrared absorption spectra showed that as the film composition changed from N rich to Si rich the dominant bonds associated with H changed from N–H to Si–H.

Expression of prostaglandin E synthase (PGES) - an enzyme of the prostaglandin biosynthetic pathway with suspected impact on carcinogenesis--was studied in Barrett's cancer to determine its pathogenetic role and prognostic impact in this entity. Expression analysis of PGES was performed on mRNA level (quantitative reverse transcription polymerase chain rection [RT-PCR]) in a large surgical series of 123 primary resected adenocarcinomas of the distal esophagus (Barrett's cancer). Gene expression results were correlated with clinical parameters, overall survival and expression levels of previously analyzed target genes of the cyclooxygenase (COX) pathway (COX-1, COX-2) and mediators of angiogenesis (vascular endothelial growth factor [VEGF]-A) and lymphangiogenesis [VEGF-C]. Expression of PGES was demonstrated in all 123 tumors (100%) on mRNA level (quantitative RT-PCR). Relative mRNA expression levels were highly variable between different cases. Gene expression showed a strong positive correlation with both COX isoforms (COX-1: r = 0.502, P < 0.001; COX-2: r = 0.679, P < 0.001), with the angiogenetic VEGF-A (r = 0.583, P < 0.001) and with the lymphangiogentic VEGF-C (r = 0.465, P < 0.001). PGES mRNA expression showed no significant correlation with clinicopathologic parameters (i.e. pTNM categories, UICC stage, survival). Variable overexpression of PGES seems to be potentially implicated in Barrett's carcinogenesis. Gene expression of PGES is strongly correlated with other mediators of the prostaglandin biosynthetic pathway, that is both COX isoforms (COX-1 and COX-2). However, no impact on patients' outcome in relation to PGES expression was found.

Mainly patients with advanced esophageal adenocarcinoma who respond to neoadjuvant chemotherapy show a significant survival benefit after resection. Therefore, prediction of response before treatment is desirable. The aim of this study was to assess genetic predictors of response and survival for patients with esophageal adenocarcinoma prior to neoadjuvant therapy. Thirty-two patients with advanced esophageal adenocarcinoma who underwent neoadjuvant therapy with resection of their tumor were analyzed for thymidylate synthase (TS), excision repair cross complementing (ERCC1) and Gluthatione S-transferase (GSTP-1) mRNA levels prior to the treatment. These results were analyzed in regards of response and survival. In total, 18 patients responded to this protocol. Seventeen of those did show a gene expression level at or below the respective median of at least one gene. This had a profound impact on survival, demonstrating an increase in survival for patients who have TS, ERCC1, or GSTP-1 mRNA level at or below the median. These results demonstrate a potential predictive value of a gene expression profile available prior to therapy. These data have to be confirmed by a larger prospective trial.

The differential and total cross sections for kaon pair production in the pp->ppK+K- reaction have been measured at three beam energies of 2.65, 2.70, and 2.83 GeV using the ANKE magnetic spectrometer at the COSY-Juelich accelerator. These near-threshold data are separated into pairs arising from the decay of the phi-meson and the remainder. For the non-phi selection, the ratio of the differential cross sections in terms of the K-p and K+p invariant masses is strongly peaked towards low masses. This effect can be described quantitatively by using a simple ansatz for the K-p final state interaction, where it is seen that the data are sensitive to the magnitude of an effective K-p scattering length. When allowance is made for a small number of phi events where the K- rescatters from the proton, the phi region is equally well described at all three energies. A very similar phenomenon is discovered in the ratio of the cross sections as functions of the K-pp and K+pp invariant masses and the identical final state interaction model is also very successful here. The world data on the energy dependence of the non-phi total cross section is also reproduced, except possibly for the results closest to threshold., 12 two-column pages, 12 figures, 1 table

The repeated passage of a coasting ion beam of a storage ring through a thin target induces a shift in the revolution frequency due to the energy loss in the target. Since the frequency shift is proportional to the beam-target overlap, its measurement offers the possibility of determining the target thickness and hence the corresponding luminosity in an experiment. This effect has been investigated with an internal proton beam of energy 2.65 GeV at the COSY-J\"ulich accelerator using the ANKE spectrometer and a hydrogen cluster-jet target. Possible sources of error, especially those arising from the influence of residual gas in the ring, were carefully studied, resulting in a accuracy of better than 5%. The luminosity determined in this way was used, in conjunction with measurements in the ANKE forward detector, to determine the cross section for elastic proton-proton scattering. The result is compared to published data as well as to the predictions of a phase shift solution. The practicability and the limitations of the energy-loss method are discussed., Comment: 11 pages, 11 figures

Plasma hydrogenation at temperatures between 50° and 700°C of thermally grown films on Si has been investigated by infrared absorption and nuclear reaction analysis techniques. Hydrogen profiles after hydrogenation are consistent with trap‐limited diffusion with a diffusivity of 10−13 cm2/s a 100°C. Hydrogen bonds predominantly to O in the host. Isotope exchange occurs on these OH bonds in a deuterium plasma, and the bonds are unstable at temperatures >500°C. Predominance of OH over bonds in thermal oxide films is in contrast to significant bond formation found by Shelby for hydrogen‐impregnated vitreous silica damaged by gamma‐ray irradiation. Bond selection by H in displacement‐damaged oxides may, therefore, be an indicator of deviation from stoichiometry.

A microbial amperometric sensor for the determination of the biochemical oxygen demand (BOD) determination using Trichosporon cutaneum cells immobilized in polyvinylalcohol has been developed. This sensor allowed BOD measurement with very short response times (< 30 s), an operation stability of 48 days and a serial coefficient of variation of ±3.3% when a sample solution containing 22 mg l−1 BOD was employed. A linear range was obtained up to 100 mg l−1 BOD using a glucose/glutamic acid standard. The sensitivity and specificity was increased by incubation of the BOD sensor with the respective wastewater. Comparable results were obtained for BOD values estimated by the biosensor and those determined by the 5-day method.

Porous silicon and its oxide can be converted into porous silicon oxynitrides by ammonia heat treatment. For example, ammonia treatment at 1000 °C for 1 h following 850 °C, 30‐min steam oxidation of porous silicon can result in up to 40 at. % nitrogen in the porous oxynitrides. These porous silicon oxynitrides are compositionally more uniform than ammonia‐nitrided thermal oxides which exhibit nitrogen buildup at the oxide layer interfaces. However, the order of the oxidation and nitridation treatment matters: nitrided oxidized porous silicon exhibits higher electrical breakdown strength than nitrided porous silicon or oxidized nitrided porous silicon.

In early esophageal cancer, squamous cell cancer and early adenocarcinoma must be managed differently because they have different origins, pathogenesis. and clinical characteristics. The current treatment options vary widely, from extended resection with lymphadenectomy to endoscopic mucosectomy or ablation. None of these treatment options can be recommended universally. Instead, an individualized strategy should be based on the depth of tumor infiltration into the mucosa or submucosa, the presence or absence of lymph node metastases, the multicentricity of tumor growth, the length of the segment of intestinal metaplasia, and comorbidities of the patient. Endoscopic mucosectomy may be sufficient in a subset of patients who have m1 or m2 squamous cell carcinoma and in patients who have isolated foci of high-grade intraepithelial neoplasia or mucosal cancer. Surgical resection is the treatment of choice for carcinomas invading the submucosal and multicentric tumors. Limited resection with jejunal interposition provides an effective treatment option for patients who have early esophageal adenocarcinoma. The onset of lymph node involvement is later in patients who have early adenocarcinoma than in patients who have squamous cell cancer, probably because chronic injury and repair mechanisms obliterate the otherwise abundant lymph vessels.

The differential and total cross sections for the dp{yields}{sup 3}He{eta} reaction have been measured in a high precision high statistics COSY-ANKE experiment near threshold using a continuous beam energy ramp up to an excess energy Q of 11.3 MeV with essentially 100% acceptance. The kinematics allowed the mean value of Q to be determined to about 9 keV. Evidence is found for the effects of higher partial waves for Q > or approx. 4 MeV. The very rapid rise of the total cross section to its maximum value within 0.5 MeV of threshold implies a very large {eta}{sup 3}He scattering length and hence the presence of a quasibound state extremely close to threshold.

Squamous cell carcinoma in a Zenker diverticulum is a very rare condition. We report a case of a patient with a Zenker carcinoma, who was primarily functionally inoperable and therefore received neoadjuvant radiochemotherapy before cardiac bypass surgery. After a complicated course with cardiogenic shock and myocardial infarction, a re-evaluation of functional risk analysis and the tumor situation revealed operability. Subsequently, partial hypopharyngectomy and partial cervical esophageal resection with lymphadenectomy was performed. Reconstruction of the gastrointestinal continuity was made by interposition of a free small bowel graft and microvascular anastomosis. The postoperative course showed a small anastomotic leakage of the hypopharyngeal-small bowel anastomosis, which was successfully treated conservatively.

Background Primary adenocarcinomas of the small intestine are rare. The prostaglandin biosynthetic pathway plays a major role in carcinogenesis and is linked with angiogenesis in various tumours. Promotion of tumour growth by transforming growth factor (TGF) β may be mediated through the prostaglandin pathway. Methods Expression of cyclo-oxygenase (COX) 1 and 2, prostaglandin E synthase (PGES), TGF-β1 and vascular endothelial growth factor (VEGF) A and C genes was analysed in 54 primary adenocarcinomas of the small intestine and corresponding normal intestinal mucosa. All patients had undergone surgical resection without previous antineoplastic therapy. Target gene expression was analysed at the mRNA level by reverse transcriptase–polymerase chain reaction and correlated with clinicopathological parameters as well as survival. COX-2 protein expression was examined by immunohistochemistry. Results Expression of COX-2 protein was detected immunohistochemically in 98 per cent of the carcinomas. COX-1, COX-2, VEGF-A, VEGF-C, PGES and TGF-β1 mRNA expression varied markedly in different tumours, but all were overexpressed compared with levels in normal intestinal mucosa. There were significant associations between levels of COX-1, COX-2, TGF-β1 and PGES mRNAs and those of VEGF-A and VEGF-C. Conclusion Correlations between levels of mRNA for COX-1, COX-2, TGF-β1 and PGES and those for proangiogenic factors VEGF-A and VEGF-C suggest a role for these factors in the propagation of primary adenocarcinomas of the small intestine.

The use of either flexible endoscopy (FE) or rigid endoscopy (RE) for removal of ingested foreign bodies (FBs) impacted in the esophagus is still discussed controversially.We report a consecutive series of 139 patients with FB impaction in the esophagus. During a 6-year period, 69 men and 70 women (median age, 64 [0.7-97] years) requiring removal of an impacted FB underwent either RE (n = 63) in the Otolaryngology Department of our hospital or FE (n = 76) in the Surgical Endoscopy Unit.Foreign body removal was equally effective with FE (success rate 93.4%) and RE (95.2%, p = n.s.). The cases in which foreign body removal failed (5 FE cases [6.6%] and 3 RE cases [4.8%]) were all subsequently successfully managed with "conversion" and use of the other technique. No severe complications occurred when FB removal was attempted with FE (0 of 76 cases; 0.0%), whereas RE was associated with esophageal rupture requiring immediate surgical intervention in 2 of 63 cases (3.2%; p0.002). Patient comfort differed significantly between the two procedures (p0.0001); RE was always performed under general anesthesia (100.0%), whereas only a minority of patients undergoing FE required general anesthesia (13.0%; p0.0001) or mild analgosedation (20.0%). The better patient comfort with FE was also reflected in a significantly lower rate of dysphagia (15%) compared to RE (48%; p0.0001). Rigid endoscopy was more frequently used in removal of FBs of the upper esophagus (p0.0001), whereas FE was the predominate approach to FBs in the lower esophagus (p0.0001).A tailored approach to treatment of FB impaction is recommended. Because of the lower rate of severe complications, better patient comfort with a lower rate of dysphagia, and lack of requirement for general anesthesia, FE should be the "first line" approach to FBs, although RE has its place as the "second line" therapy.

The potential of gene expression profiles to predict the response to neoadjuvant chemotherapy in patients with advanced adenocarcinoma of the esophagus was analyzed. Paraffin-embedded endoscopic esophageal tumor biopsies of 38 patients with advanced esophageal adenocarcinoma (Barrett's adenocarcinoma) were included. All patients underwent two cycles of cisplatin and fluorouracil (5-FU) therapy with or without additional paclitaxel (taxol) followed by abdominothoracal esophagectomy. RNA expression levels of 5-FU-metabolism associated genes thymidylate synthase (TS), thymidine phosphorylase (TP), dihydropyrimidine dehydrogenase (DPD), methylenetetrahydrofolate reductase (MTHFR), MAP7, ELF3, as well as of platinum and taxane associated related genes caldesmon, excision cross-complementing genes (ERCC1 and ERCC4) HER2-neu, DNA damage-inducible gene 45 (GADD45) and multidrug resistance genes (MDR1, MRP1) were determined using real-time RT-PCR. Expression levels were correlated with the histopathological response to chemotherapy assessed in surgically resected specimens. Responding patients showed significantly higher pretherapeutic expression levels of MTHFR (p = 0.012), Caldesmon (p = 0.016), MRP1 (p = 0.007) and MDR1 (p = 0.025). In addition, patients with high pretherapeutic MTHFR and MRP1 levels had a survival benefit after surgery (p = 0.013 and p = 0.015, respectively). Additionally, intratumoral heterogeneity of gene expression of selected genes (TP, DPD, MTHFR, HER2-neu, Caldesmon, ERCC4, MRP1) was additionally verified in 9 untreated Barrett's adenocarcinoma by examination of 5 distinct tumor areas and was observed in 12.7% (5.6%-23.5%, CI 95%) of all cases analyzed. Our results indicate that determination of mRNA levels of a few genes may be useful for the prediction of the success of neoadjuvant chemotherapy in individual cancer patients with advanced adenocarcinoma of the esophagus.

The reaction pp --> dK(+) (K) over bar (0) has been investigated at excess energies Q=47.4 and 104.7 MeV above the K+(K) over bar (0) threshold at COSY Julich. Coincident dK(+) pairs were detected with the ANKE spectrometer, and subsequently similar to 2000 events with a missing (K) over bar (0) invariant mass were identified, which fully populate the Dalitz plot. The joint analysis of invariant mass and angular distributions reveals s-wave dominance between the two kaons, in conjunction with a p-wave between the deuteron and the kaon pair, i.e. K (K) over bar production via the a(0)(+)(980) channel. Integration of the differential distributions yields total cross-sections of sigma(pp -->dK(+)(K) over bar (0))=(38 +/- 2(stat) +/- 14(syst)) nb and(190 +/- 4(stat) +/- 39(syst)) nb for the low and high Q value, respectively.

The quasi-free pn->dphi reaction has been studied at the Cooler Synchrotron COSY-Juelich, using the internal proton beam incident on a deuterium cluster-jet target and detecting a fast deuteron in coincidence with the K+K- decay of the phi-meson. The energy dependence of the total and differential cross sections are extracted for excess energies up to 80 MeV by determining the Fermi momentum of the target neutron on an event-by-event basis. Though these cross sections are consistent with s-wave production, the kaon angular distributions show the presence of p waves at quite low energy. Production on the neutron is found to be stronger than on the proton but not by as much as for the eta-meson., Comment: 4 Pages, 3 Figures, version 2, resubmitted to Phys. Rev. Lett

The pp ! ppreaction has been studied at the Cooler Synchrotron COSY-Julich, using the internal beam and ANKE facility. Total cross sections have been determined at three excess energiesnear the production threshold. The differential cross section closest to threshold at � � 18:5 MeV exhibits a clear S wave dominance as well as a noticeable effect due to the proton-proton final-state interaction. Taken together with data for pp! production, a significant enhancement of the �=! ratio of a factor 8 is found compared to predictions based on the Okubo-Zweig-Iizuka rule.

The pp--ppphi reaction has been studied at the Cooler Synchrotron COSY-Jülich, using the internal beam and ANKE facility. Total cross sections have been determined at three excess energies epsilon near the production threshold. The differential cross section closest to threshold at epsilon=18.5 MeV exhibits a clear S wave dominance as well as a noticeable effect due to the proton-proton final-state interaction. Taken together with data for ppomega production, a significant enhancement of the phi/omega ratio of a factor 8 is found compared to predictions based on the Okubo-Zweig-Iizuka rule.

Die Nodalstatus ist, nach der R0-Resektion, der wichtigste prognostische Parameter fur Patienten mit einer soliden Tumorerkrankung. Obwohl es inzwischen durch tumorbiologische und molekulargenetische Untersuchungen gelungen ist, ein besseres Verstandnis der Metastasierung in ihren Einzelschritten zu erhalten, ist die „Pathophysiologie“ der Lymphknotenmetastasierung weiterhin unklar. Bis jetzt gibt es kein zuverlassiges bildgebendes Verfahren, mit dem pratherapeutisch eine valide Aussage zum Lymphknotenstatus eines Patienten getroffen werden konnte (Siewert u. Sendler 2000).

Vector and tensor analysing powers of the d(pol)p->(pp)n (charge-exchange) and d(pol)p->(pn)p (non-charge-exchange) breakup reactions have been measured with the ANKE spectrometer at the COSY ring at a deuteron beam energy of 1170 MeV for small momentum transfers to the low excitation energy (pp) or (pn) systems. A quantitative understanding of the values of A_xx and A_yy for the charge-exchange reaction is provided by impulse approximation calculations. The data suggest that spin-flip isospin-flip transitions, which dominate the charge-exchange breakup of the deuteron, are also important in the non-charge-exchange reaction., 10 pages, 4 figures

Current treatment recommendations for early esophageal adenocarcinoma range from radical esophagectomy with extensive lymphadenectomy, limited surgical resection with/without regional lymphadenectomy to endoscopic mucosectomy or ablation. A comparison of treatment associated morbidity, tumor recurrence rates, and functional outcome suggests that none of these alternatives can be universally recommended. Rather, an individualized strategy should be employed based on depth of tumor penetration into the mucosa/submucosa, presence of lymph node metastases, multicentricity of tumor growth, length of the underlying Barrett mucosa and comorbidity of the affected patient. Endoscopic mucosectomy may suffice for an isolated focus of high-grade neoplasia or mucosal cancer, provided the neoplasia and underlying Barrett mucosa can be removed completely. Surgical resection is the treatment of choice for tumors invading the submucosa, multicentric tumors and recurrence after endoscopic mucosectomy. The extent of surgical resection must be guided by the length of the Barrett mucosa. In most instances a complete tumor resection and removal of the entire Barrett mucosa can be achieved by a limited transabdominal approach, and therefore subtotal esophagectomy may not be necessary. Application of the sentinel node technology may in the future allow to limit systematic lymphadenectomy to the rather small subgroup of patients who in fact have lymph node metastases.

The fatalistic approach towards surgical therapy of esophageal squamous cell cancer has been replaced in recent years by a more differentiated view. This was triggered by the establishment of individualized therapeutic modalities based on tumor stage, tumor location, general patient status, and comorbidity. Despite advances in nonsurgical therapy of squamous cell esophageal cancer, esophagectomy remains the central therapeutic modality. Primary subtotal en-bloc esophagectomy with lymphadenectomy is the only curative option with a high likelihood of success for resectable tumors (uT1-3 categories) located below the level of the tracheal bifurcation and for early more proximal tumors. In patients with locally advanced tumors at or above the level of the tracheal bifurcation, surgical resection can still cure those who respond to neoadjuvant radiochemotherapy. Preoperative "conditioning" of risk patients, surgical safety strategies in risk situations, and standardization of both the operative procedure and the perioperative management have resulted in a marked reduction of the previously substantial postoperative mortality to below 3% in experienced centers. In our own experience of 900 esophagectomies for squamous cell esophageal cancer, the 5-year survival rate rose from about 20% to more than 50% in the last two decades. Esophagectomy thus has become a safe operation and remains the only therapeutic option offering cure for a substantial proportion of patients with squamous cell cancer of the esophagus.

The therapy of gastroesophageal reflux disease (GERD) is uncomplicated in most cases. However, 20 % of GERD patients suffer from reflux-associated symptoms under therapy with proton pump inhibitors (PPI). The cause of this resistance to PPI-therapy remains unclear. Today, the most discussed theory is the presence of the non- or weakly acidic reflux. Objective measurements of the weakly/non-acidic reflux are available since the development of intraluminal impedance monitoring in combination with pH-monitoring. The therapy of weakly/non-acidic GERD is not well established, so far. In the course of clinical studies the therapeutic spectrum (i. e. modification of the medical therapy, endoscopic anti-reflux procedures or surgical therapy) has to be tested.

The modified technique of abdomino-right-thoracic esophagectomy (the Lewis-Tanner approach) is increasingly being favoured as the surgical procedure of choice in patients with resectable adenocarcinoma of the distal esophagus, so-called Barrett's cancer. The technical details of this procedure and the reconstruction of gastrointestinal continuity using a gastric tube with high intrathoracic anastomosis are illustrated, as they have proved useful in our own practice during recent years.

Several processes of meson production in proton-deuteron collisions have been measured simultaneously using a calibrated magnetic spectrograph. Among these processes, the $\eta$ meson is seen clearly as a sharp missing--mass peak on a slowly varying background in the $p+d\to ^3\textrm{He} +X$ reaction. Knowing the kinematics of the other reactions with well determined masses, it is possible to deduce a precise mass for the $\eta$ meson. The final result, $m(\eta)=547.311\pm 0.028 \textrm{(stat)} \pm 0.032 \textrm{(syst) MeV/c}^2$, is significantly lower than that found by the recent NA48 measurement, though it is consistent with values obtained in earlier counter experiments., Comment: 10 pages, 6 figures, Fig. 3 changed