Search

A resonant state at 3.21-0.04+0.12MeV, located just above the one-neutron separation threshold, was observed for the first time in Be12 from the Be11(d,p)Be12 one-neutron transfer reaction in inverse kinematics. This state is assigned a spin-parity of 0- according to the systematics of the level scheme of the N=8 isotones and decay-width analysis. Gamow coupled-channel and Gamow shell-model calculations show the importance of the continuum coupling, which dramatically influences the excitation energy and ordering of low-lying states. Various exotic structures associated with cross-shell intruding configurations in Be12 and in its isotonic nucleus Li11 are comparably discussed.

An inelastic excitation and cluster-decay experiment ^{2}H(^{16}C,^{4}He+^{12}Be or ^{6}He+^{10}Be)^{2}H was carried out to investigate the linear-chain clustering structure in neutron-rich ^{16}C. For the first time, decay paths from the ^{16}C resonances to various states of the final nuclei were determined, thanks to the well-resolved Q-value spectra obtained from the threefold coincident measurement. The close-threshold resonance at 16.5 MeV is assigned as the J^{π}=0^{+} band head of the predicted positive-parity linear-chain molecular band with (3/2_{π}^{-})^{2}(1/2_{σ}^{-})^{2} configuration, according to the associated angular correlation and decay analysis. Other members of this band were found at 17.3, 19.4, and 21.6 MeV based on their selective decay properties, being consistent with the theoretical predictions. Another intriguing high-lying state was observed at 27.2 MeV which decays almost exclusively to ^{6}He+^{10}Be(∼6 MeV) final channel, corresponding well to another predicted linear-chain structure with the pure σ-bond configuration.

An inelastic excitation and cluster-decay experiment $\rm {^2H}(^{16}C,~{^{4}He}+{^{12}Be}~or~{^{6}He}+{^{10}Be}){^2H}$ was carried out to investigate the linear-chain clustering structure in neutron-rich $\rm {^{16}C}$. For the first time, decay-paths from the $\rm {^{16}C}$ resonances to various states of the final nuclei were determined, thanks to the well-resolved $Q$-value spectra obtained from the three-fold coincident measurement. The close-threshold resonance at 16.5 MeV is assigned as the ${J^\pi}={0^+}$ band head of the predicted positive-parity linear-chain molecular band with ${(3/2_\pi^-)^2}{(1/2_\sigma^-)^2}$ configuration, according to the associated angular correlation and decay analysis. Other members of this band were found at 17.3, 19.4, and 21.6 MeV based on their selective decay properties, being consistent with the theoretical predictions. Another intriguing high-lying state was observed at 27.2 MeV which decays almost exclusively to $\rm {^{6}He}+{^{10}Be{(\sim6~ MeV)}}$ final channel, corresponding well to another predicted linear-chain structure with the pure $\sigma$-bond configuration., Comment: 6 pages, 4 figures

A puzzle has long existed for the α-cluster content in the near-threshold 7.54-MeV state of Be10. A new measurement was conducted to measure the cluster-decay partial width of this state using the reaction Be9(Be9,Be*10→α+He6)Be8 at 45-MeV beam energy. Special measures were taken to reduce the strong near-threshold background. The neutron-decay strength was also obtained based on the threefold coincident measurement. A cluster-decay branching ratio of (4.04±1.26)×10−4 is obtained, resulting in a reasonably large α-cluster spectroscopic factor. The present Rapid Communication confirms the formation of the σ-bond molecular rotational band headed by the 6.18-MeV state in Be10.

The properties of some very thin ( ∼ 20 μ m) large-area Single-sided Silicon-Strip Detectors (SSSDs) were investigated by using the 12C-particles elastically scattered from a Au target. In the detection system, each thin SSSD was installed in front of a thick (300 μ m or 500 μ m) Double-sided Silicon-Strip Detector (DSSD) to form a Δ E − E particle-telescope. The energy calibration of these detectors was realized by varying the beam energy and also by the irradiation from a three-component α -particle source. The thickness distribution each SSSD is precisely determined from the energy loss in the thin layer, which was independently measured by the corresponding DSSD. It is found that, for the SSSD with the nominal thicknesses of ∼ 20 μ m, the real thickness may vary by several μ m over the active area. The reason for this large non-uniformity still needs to be investigated. For the present application, this non-uniformity could be corrected according to the known pixel-thickness. This correction allows to restore a good particle identification (PID) performance for the entire large-area detector, the importance of which is demonstrated by an example of measuring the cluster-decays of the highly-excited resonant states in 16O.

A new 11Be( d , p )12Be transfer reaction experiment was carried out in inverse kinematics at 26.9A MeV, with special efforts devoted to the determination of the deuteron target thickness and of the required optical potentials from the present elastic scattering data. In addition a direct measurement of the cross section for the 0 2 + state was realized by applying an isomer-tagging technique. The s-wave spectroscopic factors of 0.20 − 0.04 + 0.03 and 0.41 − 0.11 + 0.11 were extracted for the 0 1 + and 0 2 + states, respectively, in 12Be. Using the ratio of these spectroscopic factors, together with the previously reported results for the p-wave components, the single-particle component intensities in the bound 0 + states of 12Be were deduced, allowing a direct comparison with the theoretical predictions. It is evidenced that the ground-state configuration of 12Be is dominated by the d-wave intruder, exhibiting a dramatic evolution of the intruding mechanism from 11Be to 12Be, with a persistence of the N = 8 magic number broken.

A multi-nucleon transfer and cluster decay experiment, Li( B, C + Be) , is conducted at an incident beam energy of 55 MeV. This reaction channel has a significantly large Q-value, which favors populating the high lying resonant states in C. The decay paths, from these resonances to various states of the final nucleus Be, can be selected, owing to the experimentally achieved optimal resolution of the Q-value spectrum. A number of resonant states are reconstructed from the forward emitting Be + fragments, and their major molecular structures can be detected according to the selective decay paths and relative decay widths. A state at 22.4(2) MeV validates the previously measured and theoretically predicted band head of the positive-parity -bond linear-chain molecular band. Two additional resonances at 22.9(2) and 24.2(2) MeV are identified and consistent with the predicted and members of the same molecular band, thus providing novel evidences for the existence of the exotic clustering chain structure in neutron-rich carbon isotopes. A few high energy resonances, which also indicate the presence of the -bond molecular structure, are observed; however, further studies are still required to clarify their ascription in band systematics.

An experiment for $p(^{14}\rm{C}$,$^{14}\rm{C}^{*}\rightarrow^{10}\rm{Be}+\alpha)\mathit{p}$ inelastic excitation and decay was performed in inverse kinematics at a beam energy of 25.3 MeV/u. A series of $^{14}\rm{C}$ excited states, including a new one at 18.3(1) MeV, were observed which decay to various states of the final nucleus of $^{10}\rm{Be}$. A specially designed telescope-system, installed around the zero degree, played an essential role in detecting the resonant states near the $\alpha$-separation threshold. A state at 14.1(1) MeV is clearly identified, being consistent with the predicted band-head of the molecular rotational band characterized by the $\pi$-bond linear-chain-configuration. Further clarification of the properties of this exotic state is suggested by using appropriate reaction tools., Comment: 4 figures, 1 table. Accepted by Chinese Physics C

A prototype thick-GEM-based cooling storage ring external-target experiment (CEE) time projection chamber (TPC) is constructed and tested with the pulsed ultraviolet laser beams. The results indicate that the prototype TPC has a good performance in three-dimensional track resolution. In X direction the position resolution is about 0.2 mm, and in Y direction the position resolution is about 0.5 mm. The results also determine that the energy resolution is about 5.4%, which achieve the requirements of the CEE experiment and can be used to study the nuclear state equation and the quantum chromo dynamics.

A transfer-reaction experiment of 9Be(9Be, 10Be)8Be was performed at a beam energy of 45 MeV. Excited states in 10Be up to 18.80 MeV are produced using missing mass and invariant mass methods. Most of the observed high-lying resonant states, reconstructed from the α + 6He and t + 7Li decay channels, agree with the previously reported results. In addition, two new resonances at 15.6 and 18.8 MeV are identified from the present measurement. The 18.55 MeV state is found to decay into both the t + 7Lig.s. and t + 7Li* (0.478 MeV) channels, with a relative branching ratio of 0.93 ± 0.33. Further theoretical investigations are encouraged to interpret this new information on cluster structure in neutron-rich light nuclei.

The elastic scattering and breakup reactions of the halo nucleus $^{11}\mathrm{Be}$ on deuterons at an incident energy of $26.9A$ MeV are reported for the first time. Special attention has been paid to the determination and subtraction of the proton contaminations in the deuterated polyethylene ${({\mathrm{CD}}_{2})}_{n}$ target (where ${\mathrm{D}}_{2}$ denotes $^{2}\mathrm{H}_{2}$). The cross sections for elastic scattering are analyzed with the systematic optical potentials of Daehnick et al. and DA1p, as well as with single-folding potentials, derived from the Jeukenne-Lejeune-Mahaux effective nucleon-nucleon interaction. An extended version of the continuum-discretized coupled-channels (XCDCC) formalism, including dynamic core excitation (DCX) effects, is applied to analyze the elastic scattering and breakup data. Comparisons of the full XCDCC calculation with that omitting DCX effects indicate that the core excitation plays a remarkable role in reproducing breakup reactions of $^{11}\mathrm{Be}+d$.

Peking University (PKU) and China Institute of Atomic Energy (CIAE) are jointly proposing to construct a large science facility, temporarily called “Beijing ISOL”. This facility aims at both basic science and application goals, and is based on the double driver system, namely reactor driving and intense deuteron-beam driving. On the basic science side, the radioactive ion beams produced from the isotope separation online (ISOL) device will be used to study the new physics and technologies at the limit of nuclear stability. On the other side regarding to the applications, the facility will be devoted to material research for the nuclear energy system by using typically the intense neutron and ion beams. In the whole process of design, construction and operation, an opening policy will be pursued, and the domestic and international cooperation will be emphasized. Through this project, a joint research and education mode will be established.

A Multi-Neutron Correlation Spectrometer (MuNCoS) composed of 80 detector modules was constructed at Peking University. A position resolution of less than 3 cm (FWHM) for a typical long scintillation module was obtained based on cosmic ray tests. A calibration method using an unstable nucleus beam of 11 Be, together with the fragment identification by using a zero degree telescope, has been successfully developed. Neutron detection efficiencies of 15(1)% and 17(2)% were achieved for neutron energy intervals of 30–40 MeV and 40–60 MeV, respectively, and at a signal charge threshold of 4 MeVee. The experimentally determined neutron detection efficiencies agree well with the simulation based on the GEANT4 code.

Particle detection technologies have been largely advanced in our laboratory over the past decade. A neutron sphere was built to detect the decay neutron emitted from the implanted unstable nucleus, whereas a multi-neutron correlation spectrometer was implemented to detect the forward moving neutrons resulting from breakup reactions. Charged particle telescopes are now equipped with double sided Silicon strip detectors which have excellent energy and position resolutions. Large size gas chambers, such as resistive plate chambers, have been developed in order to achieve high performances related to timing or position measurements. The advances of these technologies contribute substantially to such large science project, as LHC-CMS, and to the experiments with the radioactive nucleus beams.

Background: For the deeply bound one-nucleon removal at intermediate energies using a $^{9}\text{Be}$ or $^{12}\text{C}$ target, a strong reduction of cross section was observed relative to the prediction of eikonal theoretical model. The large disagreement has not been explained and the systematic trend is inconsistent with results from transfer reactions. The recently observed asymmetric parallel momentum distribution of the knockout residue indicates the significant dissipative core-target interaction in the knockout reaction with a composite target, implying new reaction mechanisms beyond the eikonal reaction descriptions.Purpose: To investigate the reaction mechanism for deeply bound nucleon removal at intermediate energies.Method: Neutron removal from $^{14}\text{O}$ using a $^{12}\text{C}$ target at 60 MeV/nucleon was performed. Nucleon knockout cross sections were measured. The unbound excited states of $^{13}\text{O}$ were reconstructed by using the invariant mass method with the residues and the associated decay protons measured in coincidence. The measured cross sections are compared with an intra-nuclear cascade (INC) prediction.Results: The measured cross section of ($^{14}\text{O}$, $^{11}\text{C}$) is 60(9) mb, which is 3.5 times larger than that of ($^{14}\text{O}$, $^{13}\text{O}$) channel. This $2pn$-removal cross section is consistent with INC prediction, which is 66 mb with the main contribution being non-direct reaction processes. On the other hand, the upper limit of the cross section for one-neutron removal from $^{14}\text{O}$ followed by proton evaporation is 4.6(20) mb, integrated up to 6 MeV above the proton separation energy of $^{13}\text{O}$. The calculated total cross section for such reaction processes by the INC model is 2.5 mb, which is within the measured upper limit.Conclusions: The data provide the first constraint on the role of core excitation and evaporation processes in deeply bound nucleon removal from asymmetric nuclei. The experiment results suggest that non-direct reaction processes, which are not considered in the eikonal model, play an important role in deeply bound nucleon removal from asymmetric nuclei at intermediate energies.

The elastic scattering and breakup of the halo nucleus $^{11}\mathrm{Be}$ on protons at an incident energy of $26.9A$ MeV have been measured. The $^{11}\mathrm{Be}+p$ elastic scattering cross sections at various energies, including the present one, are systematically analyzed with the Chapel Hill 89 (CH89) and Koning-Delaroche (KD) global optical model potentials (OMPs), and the corresponding normalization factors are obtained. An extended version of the continuum-discretized coupled-channels (XCDCC) formalism, including dynamic core excitation effects, is applied to analyze the elastic scattering and breakup data. It is found that the core excitation plays a moderate role in the elastic scattering and breakup reaction of the halo nucleus $^{11}\mathrm{Be}$, being consistent with previous results at higher energies.

Background: For the deeply bound one-nucleon removal at intermediate energies using a 9 Be or 12C target, a strong reduction of cross section was observed relative to the prediction of eikonal theoretical model. The large disagreement has not been explained and the systematic trend is inconsistent with results from transfer reactions. The recently observed asymmetric parallel momentum distribution of the knockout residue indicates the significant dissipative core-target interaction in the knockout reaction with a composite target, implying new reaction mechanisms beyond the eikonal reaction descriptions. Purpose: To investigate the reaction mechanism for deeply bound nucleon removal at intermediate energies. Method: Neutron removal from 14O using a 12C target at 60 MeV/nucleon was performed. Nucleon knockout cross sections were measured. The unbound excited states of 13O were reconstructed by using the invariant mass method with the residues and the associated decay protons measured in coincidence. The measured cross sections are compared with an intra-nuclear cascade (INC) prediction. Results: The measured cross section of (14O, 11C) is 60(9) mb, which is 3.5 times larger than that of ( 14O, 13O) channel. This 2pn-removal cross section is consistent with INC prediction, which is 66 mb with the main contribution being non-direct reaction processes. On the other hand, the upper limit of the cross section for one-neutron removal from 14O followed by proton evaporation is 4.6(20) mb, integrated up to 6 MeV above the proton separation energy of 13O. The calculated total cross section for such reaction processes by the INC model is 2.5 mb, which is within the measured upper limit. Conclusions: The data provide the first constraint on the role of core excitation and evaporation processes in deeply bound nucleon removal from asymmetric nuclei. The experiment results suggest that non-direct reaction processes, which are not considered in the eikonal model, play an important role in deeply bound nucleon removal from asymmetric nuclei at intermediate energies. ispartof: Physical Review C vol:93 issue:4 pages:1-8 status: published

A prototyping glass RPC with excellent signal-to-noise ratio was constructed and tested. Detection efficiencies for cosmic rays of about 95% were obtained for both avalanche and streamer modes of operation. A simple method to measure the signal charge profile is developed, which is consistent with other methods such as direct optical observation. A narrow profile for avalanche signal mode is obtained, which may lead to an intrinsic spatial resolution less than 1.0 mm FWHM. If a delay-line or charge division technique is used to determine the centroid of the signal charge distribution, it is important to reduce the electronics noise and the fluctuations of the delay-line (or resistor) units in order to reach the ultimate intrinsic position resolution.

We report for the first time the discrimination of the core fragment knockout and valence nucleon knockout reaction mechanisms at medium energy range, by the use of the recoil proton tagging technique. Intense 8He beams at 82.3 MeV/u were supplied by the RIPS beam line at RIKEN, and impinged on both hydrogen and carbon targets. Recoil protons were detected in coincidence with the forward moving core fragments and neutrons. The core fragment knockout mechanism is identified through the polar angle correlation and checked by various kinematics relations. This mechanism may be used to extract the cluster structure information of unstable nuclei. On the other hand, with the selection of the tagged valence nucleon knockout mechanism, a narrower peak of 7He ground state is obtained. The extracted neutron spectroscopic factor S n = 0.512 ( 18 ) is relatively smaller than the no-tagged one, and is in good agreement with the prediction of ab initio Greenʼs function Monte Carlo calculations.

A knockout reaction induced by 6He at 61.2 MeV/u was carried out at the HIRFL-RIBLL radioactive beam line. The α core fragments at forward angles were detected in coincidence with the recoiled protons at large angles. From this coincident measurement the valence nucleon knockout mechanism and the core knockout mechanism can be separated according to the polar angle correlation between the core fragments and the recoiled protons. It is demonstrated that, when reconstructing the resonant state of a weakly bound nucleus, the contamination resulting from the core knockout mechanism should be eliminated in order to obtain the correct structure information.

Knockout reaction experiment was carried out by using the 6He beams at 61.2 MeV/u impinging on a CH2 target. The α core fragments at forward angles were detected in coincidence with the recoiled protons at larger angles. From this exclusive measurement the valence nucleon knockout mechanism and the core knockout mechanism can be distinguished by the relation between the polar angles of the core fragments and the recoiled protons, respectively. It is demonstrated that the core knockout mechanism may result in some strong contamination to the real invariant mass spectrum.

A new 11 Be(p,d) transfer reaction experiment is performed in inverse kinematics with a radioactive 11 Be beam at 26.9A MeV. Three low-lying states, namely the 0 + ground state, the 2 + state at Ex = 3.37 MeV, and the multiplet at around 6 MeV in 10 Be, are populated by this one-neutron transfer reaction. These three states in 10 Be are clearly discriminated from the Q-value spectrum, which is rebuilt from energies and angles of the recoil deuterons in coincidence with 10 Be. A spectroscopic factor for each state is extracted by comparing the experimental differential cross sections to the theoretical calculation results using the finite range adiabatic distorted wave approximation method with different global nucleon-nucleus potentials. It is found that the newly extracted spectroscopic factors for the 0 + and 2 + states are consistent with the previous ones, but the factor for the multiplet is smaller than the value in the reference, and the possible reason is discussed.

A β -delayed neutron detection array composed of a neutron sphere and two neutron walls was constructed in the State Key Laboratory of Nuclear Physics and Technology at Peking University. Recently the performances of this detection array were largely improved and tested with a Co 60 source, cosmic rays and C 16 and N 17 radioactive beams. The Tyvek 1056D paper and silicone grease were chosen for the reflection and coupling materials, respectively. For the neutron sphere with large detection solid angle ( 30 % of 4 π steradian), the intrinsic efficiency is about 14.1 % at a neutron energy of 1 MeV and the detection threshold is about 350 keV; for the neutron walls with flexible setup, these values are 36.5 % and 200 keV, respectively. The combined array of neutron sphere and neutron walls has successfully been applied to measure the β -delayed neutrons emitted from neutron-rich unstable nuclei.

Sensitivity of the direct nuclear reaction to the exotic structure of the unstable nuclei is outlined. The transfer reaction induced by 6 He on a 9 Be target at 25 MeV/u is described. The theoretical analysis using CRC model supports the di-neutron configuration of the two valence neutrons in 6 He . Preliminary calculation for 17 Ne were introduced which indicates the advantage of using transfer reaction to clarify the s-wave or d-wave configuration of the valence protons.

The production of Resistive Plate Chambers (RPCs) for the first Endcap station (RE1) of CMS experiment at Large Hadron Collider (LHC) has started at CERN since June 2004. For good performance of CMS muon and trigger systems these chambers have been assembled in accordance with strict QC (quality control) and QA (quality assurance) procedures during various assembly steps. Up to October 2005, more than 140 chambers have been constructed and more than 100 of them have been tested with cosmic rays. The chambers are assembled with the sensitive volumes (namely gas gaps) which were manufactured in Korea and all relevant mechanical parts were made in China. The procedure of chamber construction and the experience we have accumulated during the assembly will be described.

The timing performance of a two-dimensional position-sensitive silicon detector (PSD) was tested using 6He beam. An approximately linear relationship between the position of incident particles and the timing output of the detector is found. A qualitative explanation is given to why a relatively long charge collection time on the resistive anode leads to the large time diffusion of the timing output. It is estimated that the maximum timing shift between the edge area and the central area may attain an order of ∼ 1 μ s .

Differential cross sections for quasi-elastic scattering, breakup reaction as well as 1n- and 2n-transfer reactions induced by 6He at 25 MeV/nucleon from a 9Be target are reported. The experimental data were analysed in the context of the coupled-channel calculations. The internal structure of 6He is discussed and further studies are proposed.

Low Pressure Multi-Wire Proportional Chambers (LPMWPC) were made in the laboratory and the systematic tests were carried out. The position resolution of the chamber is about 0.5 mm and the time resolution is about 1.5 ns. The detection efficiency is higher than 90% for light nuclei at low and intermediate energies, and for beam intensities lower than 105 pps. This kind of detector is applicable for monitoring the radioactive ion beam which is in general characterized by low intensity and large spot. Application of new read-out techniques may allow to improve the beam intensity capability.

A cluster-transfer experiment of $^9\rm{Be}(^9\rm{Be},^{14}\rm{C}\rightarrow\alpha+^{10}\rm{Be})\alpha$ at an incident energy of 45 MeV was carried out in order to investigate the molecular structure in high-lying resonant states in $^{14}$C. This reaction is of extremely large $Q$-value, making it an excellent case to select the reaction mechanism and the final states in outgoing nuclei. The high-lying resonances in $^{14}$C are reconstructed for three sets of well discriminated final states in $^{10}$Be. The results confirm the previous decay measurements with clearly improved decay-channel selections and show also a new state at 23.5(1) MeV. The resonant states at 22.4(3) and 24.0(3) MeV decay primarily into the typical molecular states at about 6 MeV in $^{10}$Be, indicating a well developed cluster structure in these high-lying states in $^{14}$C. Further measurements of more states of this kind are suggested., Comment: To be published in Chinese Physics C; 4 pages, 3 figures

In a recent breakup-reaction experiment using a Be12 beam at 29 MeV/nucleon, the 0+ band head of the expected He4+He8 molecular rotation was clearly identified at about 10.3 MeV, from which a large monopole matrix element of 7.0±1.0 fm2 and a large cluster-decay width were determined for the first time. These findings support the picture of strong clustering in Be12, which has been a subject of intense investigations over the past decade. The results were obtained thanks to a specially arranged detection system around zero degrees, which is essential in determining the newly emphasized monopole strengths to signal the cluster formation in a nucleus.

The first six Resistive Plate Chambers (RPCs) of RE1/1 in the forward region of the Compact Muon Solenoid (CMS) detector were constructed and are being tested. These RPCs cover the pseudo-rapidity region from 1.6 to 2.1 and will serve as the base detector for the CMS RPC muon trigger. We report that these six RPCs are being tested with the CMS RPC quality certification procedures and that a full measurement of a chamber efficiency of 95 ± 4 % has been achieved at an operating voltage of 9.4 kV. This performance demonstrates that the RPC is qualified to be tested at the closest distance to the beam pipe as the muon trigger detector at the full LHC design luminosity.

H. B. YOU, Y. L. YE, Z. H. LI, Y. C. GE, R. QIAO, Z. H. YANG, Z. Y. TIAN, Y. L. SUN, H. N. LIU, J. CHEN, J. WU, Y. S. SONG, J. S. WANG, Y. Y. YANG, S. L. JIN, J. B. MA, P. MA 1 School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, 100871, P. R. China, 2 School of Nuclear Science and Technology, Harbin Engineering University, Harbin, 150001, P. R. China 3 Institute of Modern Physics, China Academy of Sciences, 509 Nanchang Road, Lanzhou, 730000, P. R. China

Knockout reaction experiment for 8He at 82.3 MeV/u on Hydrogen target was carried out at the RIPS beam line in RIKEN. Recoil protons were detected in coincidence with the forward moving core fragments and neutrons. The quasi-free knockout mechanism is identified through the polar angle correlation and checked by various kinematics conditions. The absolute differential cross sections for 6He core cluster are obtained and compared with the simple Glauber model calculations. The extracted spectroscopic factor is close to unity and a shrinking of the cluster size is evidenced.

A knockout reaction experiment was carried out using a 6He beam at 82.3 MeV/u impinged on carbon and hydrogen targets. The recoil protons were detected in coincidence with the forward moving charged fragments and neutrons. It is demonstrated that through the correlation between the recoil protons and forward moving charged fragments, the core fragment knockout and valence nucleon knockout reaction mechanisms can be discriminated at energies around 100 MeV/u. The 5He ground-state resonance was reconstructed based on the selection of the valence nucleon knockout mechanism. The resonance parameters were obtained for both carbon and hydrogen targets, which are consistent with those previously reported in the literature. The importance of selecting appropriate reaction mechanisms is discussed based on reconstructions using events with larger transverse momentum transfer.

Quasielastic scattering of $^{6}\mathrm{He}$ on a $^{12}\mathrm{C}$ target was measured at 82.3 MeV/nucleon. Special care was taken to treat the background subtraction at very small angles. The measured differential cross-sections show a large enhancement at small angles relative to the Rutherford cross-section, similar to those observed at lower energies for the scattering of halo nuclei. The overall structure of the cross-section is reasonably reproduced by the optical model calculations. The inelastic channels which populate two low-lying excited states of $^{12}\mathrm{C}$ target nucleus were included in the framework of the coupled channel analysis. Further systematic theoretical analysis is encouraged.

Pancreatic and intestinal growth rates were measured in mice fed on raw soya-bean flour (RSF) for up to 24 weeks. Control animals were fed on standard chow. The effects of RSF on the mouse pancreas resembled that seen in rats, showing hypertrophy with some hyperplasia. A marked increase in small intestinal weight was also found in mice fed on RSF but not in rats fed on this diet. Histological studies showed an increase in both villous and crypt thicknesses in the small intestine from these mice, and DNA, RNA and protein measurements indicated that the increase in intestinal weight was due to hypertrophy and hyperplasia of the mucosal layer. To determine whether the intestinal growth in mice fed on RSF was purely a response to the trypsin inhibitor (TI) component of the diet, pancreatic and intestinal growth rates were also determined in mice fed on the synthetic trypsin inhibitor camostate, at levels of 0·5 or 2 g/kg in rat chow, for periods of 1–8 weeks. Control animals were fed on standard chow. RSF and 0·5 g camostate/kg had similar trypsin inhibitor activities (measured against bovine trypsin), and both caused similar increases in pancreatic weight, DNA, RNA and protein content. However, 0·5 g camostate/kg did not affect small intestinal weight. Chow containing 2 g camostate/kg contained twice as much TI activity as the RSF diet but produced only a small increase in small intestinal weight at 2 and 8 weeks. This intestinal growth was significantly less than that seen with RSF. The present study shows that, in the mouse, RSF or a diet containing camostate in the appropriate dose produces pancreatic growth comparable to that seen in the rat. RSF also causes intestinal growth, but camostate-containing diets have little or no effect on the growth of the intestine.

Differential cross sections for the elastic scattering of halo nucleus 6He on proton target were measured at 82.3 MeV/u. The experimental results are well reproduced by optical model calculations using global potential KD02 with a reduction of the depth of real volume part by a factor of 0.7. A systematic analysis shows that this behavior might be related to the weakly bound property of unstable nuclei.

The first spectroscopic study for the beta decay of N-21 is carried out based on beta-n, beta-gamma, and beta-n-gamma coincidence measurements. The neutron-rich N-21 nuclei are produced by the fragmentation of the E/A=68.8 MeV Mg-26 primary beam on a thick Be-9 target and are implanted into a thin plastic scintillator that also plays the role of beta detector. The time of flight of the emitted neutrons following the beta decay are measured by the surrounding neutron sphere and neutron wall arrays. In addition, four clover germanium detectors are used to detect the beta-delayed gamma rays. Thirteen new beta-delayed neutron groups are observed with a total branching ratio of 90.5 +/- 4.2%. The half-life for the beta decay of N-21 is determined to be 82.9 +/- 7.5 ms. The level scheme of O-21 is deduced up to about 9 MeV excitation energy. The experimental results for the beta decay of N-21 are compared to the shell-model calculations.

Human amnion fibroblasts produce abundant prostaglandins toward the end of gestation, which is one of the major events leading to parturition. In marked contrast to its well-described antiinflammatory effect, glucocorticoids have been shown to up-regulate cyclooxygenase-2 (COX-2) expression in human amnion fibroblasts. The mechanisms underlying this paradoxical induction of COX-2 by glucocorticoids have not been resolved. Using cultured human amnion fibroblasts, we found that the induction of COX-2 mRNA expression by cortisol was a glucocorticoid receptor (GR)-dependent process requiring ongoing transcription. Upon transfection of a COX-2 promoter-driven reporter gene into the amnion fibroblasts, cortisol stimulated the COX-2 promoter activity. This was abolished by mutagenesis of a cAMP response element (CRE) at -53 to approximately -59bp as well as by cotransfection of a plasmid expressing dominant-negative CRE-binding protein (CREB). The phosphorylation level of CREB-1 was significantly increased by cortisol treatment of the amnion fibroblasts, whereas the effect was attenuated either by the protein kinase A inhibitor H89 or the p38 -MAPK inhibitor SB203580. The induction of the COX-2 promoter activity and the phosphorylation of CREB-1 were also blocked by the GR antagonist RU486. Chromatin immunoprecipitation (ChIP) assay revealed that the binding of CREB-1 to the CRE of the COX-2 promoter was increased by cortisol treatment of the amnion fibroblasts. In conclusion, cortisol, via binding to GR, stimulated COX-2 expression by increasing phosphorylated CREB-1 binding to the CRE of the COX-2 gene. Cortisol may phosphorylate CREB-1 by activating either protein kinase A or p38-MAPK in the amnion fibroblasts.

The classical (first integral) methods of studying restrictions on the possible motion of gravitationally interacting bodies are reviewed. The simple and flexible inequality method is extended to a similar approach to the relationship between possible forbidden motion and (asymptotic) symmetries in the relativistic few-body problem. This extended method is used to reproduce the standard results of bounded motion for a test particle in a Schwarzschild geometry. The existence of bounded motion is shown for the general relativistic few-body problem and the difficulties in determining such bounded motion is analysed. The use of this approach to obtaining a relativistic alternative to the classical Roche lobe analysis in contact binaries is discussed.

Nuclei of pancreatic cells were isolated by trypsin-detergent digestion of fresh tissue and stained with propidium iodide, and nuclear DNA was measured by flow cytometry. Samples were isolated from mice fed either chow or raw soya flour (RSF) for periods ranging from 1 day to 48 weeks, beginning at 4 weeks of age. In chow-fed mice, the pancreas contained about 80% diploid (2N) and 20% tetraploid (4N) cells at the start of the study, but tetraploidy gradually increased to about 40% 2 weeks later (6 weeks of age) and remained at this level from that time onwards. Low levels of octaploid nuclei (8N) were also present in some animals after 2 weeks. In RSF-fed mice, about 20% tetraploid nuclei were also present for 1 and 2 days after starting RSF, but by 4 days tetraploidy had increased significantly to 40% and by 14 days had further increased to 50%. This level was significantly higher than that seen in chow-fed animals and was maintained for up to 48 weeks. Significantly higher numbers of octaploid nuclei were also present in the RSF-fed animals. In both chow- and RSF-fed mice, most cells were mononuclear, averaging 70% in chow-fed and 64% in RSF-fed animals. This difference was significant. This study shows that the mouse pancreas differs from the rat pancreas in the absence of a large population of binucleate acinar cells and the presence of considerable nuclear tetraploidy. Raw soya flour feeding leads to significant changes in these features, but in this species these changes do not appear to predispose to neoplasia.

A new transition is reported in the beta-delayed neutron decay of {sup 18}N. The observed neutron energy is 3.78{+-}0.05 MeV with a branching ratio of 0.05{+-}0.03%, which corresponds to an excitation energy of 12.05{+-}0.05 MeV in the daughter nucleus {sup 18}O. The log ft value of this transition is 5.24{+-}0.3, which, together with the previously reported electron scattering data, determines the J{sup {pi}} value of this level to be 1{sup -}. The experimental data are compared to the shell model calculations in different model spaces.