Japanese weather data for areas that produced Campylobacter spp.-positive chicken products were compared with those for areas producing negative samples. Regarding samples produced during the period of rising temperature (spring and summer), the mean weekly air temperatures for Campylobacter-positive samples were higher than those for negative samples for the period of the week in which the samples were purchased (18·7°C vs. 13·1°C, P=0·006) to a 12-week lag (12 weeks before purchasing samples; 7·9°C vs. 3·4°C, P=0·009). Significant differences in weekly mean minimum humidity and sunshine duration per day were also observed for 1- and 2-week lag periods. We postulated that the high air temperature, high humidity and short duration of sunshine for the chicken-rearing period increased Campylobacter colonization in chickens during the period of rising temperature. Consequently, the number of Campylobacter-contaminated chicken products on the market in Japan may fluctuate because of the climatic conditions to which reared chickens are exposed.

We determined the effects of pretreatment with midazolam or fentanyl on the ease of laryngeal mask airway insertion using propofol without a muscle relaxant. One hundred and eighty ASA class I or II patients were randomly allocated to one of three groups, 60 patients per group, to receive either placebo (Group C), midazolam 0.05 mg kg−1 (Group M) or fentanyl 2 μg kg−1 (Group F), respectively. Following intravenous administration of these drugs, Group C received propofol 2.5 (Group C-2.5) or 3.0 mg kg−1 (Group C-3.0). Group M and Group F received propofol 2.0 or 2.5 mg kg−1 (Group M-2.0, M-2.5, F-2.0 and F-2.5, respectively). There was a smaller incidence of severe head and limb movements on LMA insertion in Group M-2.5, Group F-2.0 and Group F-2.5 than in Group C-2.5. Airway obstruction and inadequate jaw relaxation, which were occasionally recognized in Group C and Group F patients, were not observed in Group M-2.5. Overall the ease of LMA insertion was significantly better in Group M-2.0, Group M-2.5 and Group F-2.5 than in Group C 2.5, however, the blood pressure in Group F after LMA insertion was significantly lower than in Group M. We conclude that pretreatment with midazolam 0.05 mg combined with propofol 2.5 mg kg−1 provides safe and satisfactory conditions for LMA insertion.

Recovery of neuromuscular blockade after vecuronium 0.2 mg kg−1 was measured by post-tetanic burst count (PTBC) and train-of-four (TOF) in 120 adult patients anaesthetized by one of four techniques: neuroleptanaesthesia or one minimum alveolar concentration of isoflurane, enflurane, or sevoflurane. Onset of recovery was taken when there was reflex movement in response to carinal stimulation. The time course of recovery measured by burst count was similar for all four types of anaesthesia. Recovery of each of the twitches of the TOF was significantly shorter under neuroleptanaesthesia than under isoflurane, enflurane, or sevoflurane anaesthesia [times to return of T1 were 41.4±5.4, 51.5±10.6, 52.2±10.0, or 55.3±11.2 min (mean±SD). P<0.05]. The burst count at the onset of reflex movement was less under neuroleptanaesthesia than under isoflurane, enflurane, or sevoflurane anaesthesia (16.3±4.8, 26.7±6.7, 27.7±6.8, 28.0±8.4, P<0.05). The ratio of first twitch to control twitch at the onset of reflex movement was the same for all four types of anaesthesia.

The sensitivity of train-of-four (TOF) or double burst stimulation3,3 (BBS3,3) was examined to detect fade by visual inspection, at varying stimulating currents, using the thumb of the investigated arm maintained abducted by the use of a rubber band. One-hundred adult patients were allocated randomly to (1) train-of-four-rubber band (TOF-RB), (2) train-of-four-control (TOF-control), (3) double burst stimulation-rubber band (DBS-RB), or (4) double burst stimulation-control (DBS-control) group. Each group contained 25 patients. The thumb of the investigated arm was kept abducted using a rubber band in the TOF-RB band and DBS-RB group and was free in the TOF-control and DBS-control. TOF stimuli were delivered in the TOF-RB and TOF-control groups, and DBS3,3 in the TOF-RB and TOF-control at 50, 30 and 20 mA. The probability of visual detection of TOF fade was the same in the TOF-RB and TOF-control groups. In contrast, when measured TOF ratio was 0.51–0.80, at the stimulating current of 50 or 30 mA, the likelihood of visual detection of fade in the DBS-RB group was significantly higher than in the DBS-control group (P < 0.05). With a TOF ratio of 0.61–0.70, in the DBS-RB group the probability of visual detection of fade at 50 or 30 mA was significantly higher than at 20mA (P < 0.05). This study suggests that when using a rubber band, fade in response to the DBS3,3 is detected by visual inspection more readily at a stimulating current of 50 or 30mA than without the rubber band.

β-FeSi2 is a promising material for the application of various electronic, optoelectronic and energy devices. We present here the semiconducting properties of β-FeSi2 films on Si(100) substrate prepared by laser ablation method. Samples were grown using poly-crystalline bulk β-FeSi2 prepared by horizontal gradient freeze method. For the monitoring of growth, in-situ observation of ablation plume was made through fluorescence spectroscopy. Reflection of highenergy electron beam diffraction (RHEED) was also made in-situ to see the surface morphology. Characterization of the films by X-ray diffraction presented purely P3(220) orientation. Raman scattering measurements at room temperature also indicated that the grown films are semiconducting β-FeSi2. Optical absorption spectra at room temperature showed absorption coefficient higher than 105 cm−1 above the band-gap (˜1.2 eV). It was revealed that high quality semiconducting β-FeSi2 films can be fabricated by laser ablation method without post-annealing.

A combined ion beam and molecular beam epitaxy (CIBMBE) method was applied for the deposition of a Ge1−x, Cx, alloy on Si(100) using a low-energy ( 50 – 100 eV ) C+ ion beam and a Ge molecular beam. Metastable Ge1−xCx solid solutions were formed up to x= 0.047, and the CIBMBE method was shown to have a very high potential to grow metastable Ge1−xCx alloys. It was also revealed that the sticking coefficient of C+ ions into Ge was ˜28% for Ei = 100 eV and ˜18% for Ei. = 50 eV. Structural characterization suggests that the deposited films are single crystals grown epitaxially on the substrate with twins on {111} planes. Characterization of lattice dynamics using Raman spectroscopy suggested that the deposited layers have a small amount of ion irradiation damage.

A combined ion beam and molecular beam epitaxy (CIBMBE) method was applied for the deposition of a Ge1-xCx alloy on Si(100) using a low-energy ( 50 – 100 eV ) C+ ion beam and a Ge molecular beam. Metastable Ge1-xCx solid solutions were formed up to x = 0.047, and the CIBMBE method was shown to have a very high potential to grow metastable Ge1-x,Cx alloys. It was also revealed that the sticking coefficient of C+ ions into Ge was ∼28% for Ei, = 100 eV and ∼18% for Ei = 50 eV. Structural characterization suggests that the deposited films are single crystals grown epitaxially on the substrate with twins on {111} planes. Characterization of lattice dynamics using Raman spectroscopy suggested that the deposited layers have a small amount of ion irradiation damage.

Synthesis of metastable group-IV binary alloy semiconductor thin films on Si was achieved by the crystalline growth of Si1-xSnx layers using Sn ion implantation into Si(100) followed either by ion-beam-induced epitaxial crystallization (IBIEC) or solid phase epitaxial growth (SPEG). Si(100) wafers were implanted at room temperature with 110keV 120Sn ions to a dose of 1×1016 cm-2 (x=0.029 at peak concentration) and 2x1016 cm-2 (x=0.058 at peak concentration). By this process about 90nm-thick amorphous Si1-xSnx and about 30nm-thick deeper amorphous Si layers were formed. IBIEC experiments performed with 400keV Ar ions at 300–400°C have induced an epitaxial crystallization of the amorphous alloy layers up to the surface and lattice site occupation of Sn atoms for samples with the lower Sn concentration (LC). XRD analyses have revealed a partial strain compensation for the crystallized layer. Samples with the higher Sn concentration (HC) have shown an epitaxial crystallization accompanied by defects around the peak Sn concentration. SPEG experiments up to 750°C for LC samples have shown an epitaxial crystallization of the fully strained alloy layer, whereas those for HC samples up to 750°C have revealed a collapse of the epitaxial growth around the interface of the alloy layer and the Si substrate. Photoluminescence (PL) emission from both IBIEC-grown and SPEG-grown samples with the lower Sn concentration has shown similar peaks to those by ion-implanted and annealed Si samples with intense I1 or I1-related (Ar) peaks. Present results suggest that IBIEC has a feature for the non-thermal equilibrium fabrication of Si-Sn alloy semiconductors.

We report on the synthesis of β-FeSi2 bulk materials using Horizontal Gradient Freeze (HGF) method. Chunk and powder FeSi2 or high-purity Fe (4N) and Si (9N) were used as starting materials. Three values (1:2, 2:5 and 1:3) of the Fe:Si ratio were selected in the very narrow α and β ranges of the equilibrium phase diagram. Samples were melted between 1300°C and 1500°C in high purity graphite crucibles covered with boron nitride. After cooling, the samples were kept at 800°C and 900°C during 66 to 100 hours, leading to transformation from α to β phase. Cooling rate and annealing time were taken as the two main parameters to optimize the growth conditions. Principal structural characterization was made by X-ray diffraction (XRD). Correlation with stoichiometry was achieved using the results of Rutherford Backscattering Spectroscopy (RBS) and Electron Probe X-Ray Micro Analysis (EPXMA). The samples obtained from 1:2 ratio exhibited mainly β phase while the 2:5 ratio specimens revealed almost α phase structure. The samples prepared with 1:3 ratio was found as a mixture of α and β phases under Si-rich conditions.

Epitaxial layers of Si1-x-yGexCy on Si(100) (x=0.13 and y=0.014 at peak concentration) were formed by ion implantation of Ge ions and C ions at room temperature (RT) and by subsequent IBIEC (ion-beam-induced epitaxial crystallization) process with 400keV Ge and ar ions at 300-400°C and SPEG (solid phase epitaxial growth) process up to 840°C. Crystallization up to the surface both by IBIEC and SPEG processes has been confirmed with RBS-channeling analysis. X-ray diffraction experiments have demonstrated strain compensation by incorporation of C atoms for IBIEC-grown Si1-x-yGexCy/Si samples, whereas strain accommodation due to C precipitation has been observed for SPEG-grown Si1-x-yGexCy/Si samples. Photoluminescence (PL) observed at 2K from IBIEC-grown samples has shown intense I1 peak with/without I1 related (Ar) peak and that from SPEG-grown samples has shown G line emission. these optical properties could suggest that small vacancy agglomeration is dominant in IBIEC-grown samples and C agglomeration is dominant in SPEG-grown samples, respectively.

Hg (mercury) in GaAs is known to be a moderately deep acceptor impurity, having a 52 meV activation energy. Optical properties of Hg acceptors in GaAs were systematically investigated as a function of Hg concentration, [Hg]. Samples were prepared by high-energy ion-implantation of Hg+ into GaAs grown by the liquid encapsulated Czochralski (LEC) method. Heat treatment was made by furnace annealing and rapid thermal annealing. Photoluminescence measurements at 2K revealed that the Hg-related so-called “g” line is formed in addition to the well-defined conduction band-to-Hg acceptor transition, (e, Hg). Additionally, three shallow emissions are formed for net hole concentrations INA-NDI greater than 2×1017cm−3 . This is the first demonstration that even Hg in GaAs makes multiple shallow emissions due to acceptor-acceptor pairs and LEC GaAs can be used for the investigations of these emissions.

Furnace annealing (FA) and rapid thermal annealing (RTA) were made for Cd+ ion-implanted GaAs with Cd concentration, [Cd] from 1×1016cm−3 to 3×1021 cm−3. In FA samples, Raman scattering spectra exhibited a single peak at 292 cm−1 for entire [Cd] range which is LO-phonon mode from (100) GaAs. In RTA samples, LO-phonon mode is a single peak for [Cd]<1×1019cm−3 but with growing [Cd], TO-phonon mode appears for [Cd] 1×1020cm3 and becomes a dominant signal for [Cd]=3×1021 cm−3. The quenching of LO-phonon mode with increasing [Cd] was more clearly observed in RTA samples than in FA ones. Hall-effects results, however, showed that activation rate of RTA samples is 6–7 times larger than that of FA ones for [Cd] 1×1021 cm−3. 2K photoluminescence spectra revealed that in FA samples multiple shallow emissions associated with Cd are formed while in RTA ones the dominant emission is the band to Cd acceptor transition.

Carbon ion (C+) irradiation during molecular beam epitaxy (MBE) growth of GaAs/GaAs and in0.53.Ga0.47As/InP layers was carried out using CIBMBE (combined ion beam and molecular beam epitaxy) method as a function of wide acceleration energy (Ea=30 eV-30 keV) at a constant ion beam current density. Judging from the monitored current density and the net hole concentration (INA-ND|) obtained from Hall effect measurements, activation rate as high as 88% was achieved for as-grown GaAs layers by C+ ion irradiation of Ea=~170eV. It was revealed that by annealing at 800°C, a slight enhancement (~ 10%) of INA-ND| is practiced for Ea <~ 130eV but a significant increase of INA-ND| is realized for Ea>~lkeV. IN in0.53Ga0.47As/InP layers with increasing Ea, a type conversion of electric conduction from n to p was found to occur at Ea= ~70~100eV. these observations describe that Ea plays a vital role to determine the location of incorporated electrical and optical active impurities in GaAs and inGaAs. Further for comparison, C+-implanted GaAs layers were prepared by high-energy (400 keV) ion-implantation as a function of substrate temperature (T1=RT-600 °C). For C dose concentration of lxl018cm-3\ the highest activation rate of ~20 % was obtained at T1=~150 °C. This result states that CIBMBE method is a superior doping method in view of activation rate of introduced dopants and the formation of damage-free ion-irradiated layers.

SI GaAs crystals submitted to single- or multi-step, ingot-or wafer-annealing are investigated using photoluminescence (PL) and photoacoustic spectroscopy (PA). The near-band-edge PL transitions are well resolved, with a neutral acceptor-bound exciton recombination displayed as a split doublet. The improvement induced by wafer-annealing is illustrated by the absence of additional defect-related transitions found after ingot-annealing. For the room temperature PA measurements, the intensity of a peak occuring at 1.39 eV is shown to lead to an estimation of the arsenic micro-defect density as evaluated by AB etching. The 1.39 eV PA band is also asserted to be the non-radiative recombination path of a 1.482 eV band found in the low-temperature PL spectra.

Molecular beam epitaxy (MBE) of Ge-doped GaAs was made, in which As4 to Ga flux ratio :γ and Ge concentration :[Ge] were used as growth parameters. Photoluminescence (PL) spectra at 2K for slightly Ge-doped GaAs revealed that for γ =1 the emission of excitons bound to neutral Ge acceptors (A°,X) was the dominant one. With increasing γ ,(A°,X) was found to be steeply suppressed and at around γ=1.1, (A°,X) was totally quenched. For γ higher than 1.4, the emission of excitons bound at neutral Ge donors (D°,X) was gradually enhanced and for γ =11, (D°,X) became the principal one. Through van der Pauw measurements, samples with [Ge] around 1×1017cm-3 presented type conversion at around γ=1.7. In this series, the sample with γ =1.0 indicated a strong specific emission, [ g-g], which is formed just below (A°,X) and exhibited a strong energy shift towards lower energy sides (red shift) with increasing [Ge]. [g-g] was theoretically attributed to the pairs between excited-state acceptors. Since [g-g] is known to be easily quenched by small amount of donors, the formation of predominant [g-g] for γ =1 assures that very low-compensated p-type GaAs were grown by using this typically am-photeric impurity. We fabricated a series of p-type Ge-doped GaAs by keeping γ =1 in which the net hole concentration, │ NA-ND │ as high as 1×1020cm-3 was attained. We found four emissions which exhibited significant energy shifts with increasing │ NA-ND │ . From │ NA-ND │ ~1×1016 cm-3, [g-g] begins to appear as a dominant emission and at │ NA-ND │ ~ 1×1017 cm-3, another red shift emission, [g-g]2 begins to be formed parralelly on the higher energy side of [g-g]. It is interesting to note that both [g-g] and [g-g]2 seem to be totally quenched by the further increase of [Ge]. The emission due to band to Ge acceptor,(e,Ge) does not change its central energy until [Ge]= 5×-1018cm-3 and for larger [Ge] it turned into a new broad emission,[g-g]β showing a steep red energy shift. [g-g]α was formed on the higher energy side of (e,Ge) and indicated a systematic blue energy shift with growing [Ge] larger than 1×1019cm-3. [g-g]α was theoretically explained to be the emission due to the pairs between ground-state acceptors.

Electrical properties of heavily Be-doped GaAs grown by molecular beam epitaxy were investigated systematically in a wide range of Be-concentration from 1× 1014 up to 2× 1020 cm-3 by using yan der Pauw technique. Probable carrier scattering mechanisms observed in this work are discussed by taking into account the radiative mechanisms of several new photoluminescence emissions previously observed in the band-edge-emission region of the samples. All samples were checked their electrical properties first at room-temperature. Five selected samples out of them were measured from 10° K up to room-temperature. Samples having the carrier concentration from 1014 to 1018 cm3 presented typical semiconductor-like conduction with finite carrier excitation energy. For samples having carrier concentration 7× 1016 cm -3, the conduction mechanism at high temperature region above 30β K was dominated by holes thermally excited into valence band. At low temperature region below 30° K . it was dominated by holes hopping from neutral to ionized acceptors with the assistance of phonons. Hole mobilities of samples having the carrier concentration from 1017 to 1018 cm-3 showed an anomalous behavior in the low temperature region, which suggests the presence of a new type of carrier scattering mechanism. A radiative center denoted by lg-gl observed in this concentration region will be a candidate scattering center to explain these electrical behaviors. Samples having the carrier concentration larger than 1019 cm-3 demonstrated typically metallic electric conduction not owing to thermally excited carriers, which means that an impurity band is formed but merged with valence band. The density of state of this combined valence band mixed with impurity band can be supposed to reflect carrier concentration dependence of the PL emission bands observed in this region, i.e. [g-g]α , [g-g]β and [g-g]γ .

Implantation of Mg+ and C+ ions is carried out in bulk InP substrates using single or several energies up to 400 keV. The net carrier concentration profile at 300K is measured by capacitance-voltage (C-V) method. The ground and excited states binding energies of Mg and C acceptors are determined by low-temperature selective excitation of photoluminescence (PL). Additional sharp exciton-Iike emissions are detected after annealing of the samples. Their intensity is found to decrease with increasing Mg+ or C+ dose. Annealing-induced activation and/or formation of complex defect are the likely candidate mechanisms for the involved defect.