Search

Dimuon and trimuon events produced by the interaction of 250 GeV muons in an iron target have been studied and are shown to originate predominantly from charm production. The data are used to measure the contribution of charm to the nucleon structure function F 2 . The cross sections for real photoproduction ( Q 2 =0) of charm in the current fragmentation region are derived as a function of photon energy and are found to be ∼0.6% of the total, hadronic photoproduction cross section in this energy range. The measured cross sections are found to be well represented by the photon-gluon fusion model. The charmed quark fragmentation function is obtained by using this model to fit the measured decay muon energy distribution and is found to be well represented by exp(1.6±1.6) Z . The data are used to study the momentum distribution of the gluons in the nucleon. An upper limit of 1.4% (90% confidence level) is set on the branching ratio D→ μν and a model-dependent upper limit on the branching ratio F→ μν is derived.

A QCD analysis in leading and next to leading order of the structure function F 2 measured in deep inelastic muon nucleon scattering is presented. Taking into account several phenomenological uncertainties, including the gluon description and the charm contribution, fits to the data give values of the QCD scale parameter Λ LO in the range 7-–250 MeV. A consistent description of muon scattering and lower Q 2 electron scattering requires the presence of higher twist 1/ Q 2 contributions to the scale breaking which are then determined as a function of x from the data.

Using the data on deep inelastic muon scattering on iron and deuterium the ratio of the nucleon structure functions F 2 N ( Fe )/ F 2 N ( D ) is presented. The observed x -dependence of this ratio is in disagreement with existing theoretical predictions.

Charm production has been studied through multimuon events produced in 250 GeV μ + -interactions. The measured dimuon cross section is in agreement with the photon gluon fusion model at low values of Bjorken x within statistical and systematic errors. At larger values of x Bi the data do not support the magnitude of intrinsic charm used to explain hadro-production of charm. Upper limits on the intrinsic charm content of the nucleon are derived from the data.

Raymer AM, Bandy D, Adair JC, Schwartz RL, Williamson DJG, Gonzalez Rothi LJ, Heilman KM. Effects of bromocriptine in a patient with crossed nonfluent aphasia: A case report. Arch Phys Med Rehabil 2001;82:139-44. Objective: Because studies have shown some positive effects of the dopaminergic agent bromocriptine for improving verbal production in patients with nonfluent aphasia, we examined its effect in a patient with an atypical form of crossed nonfluent aphasia from a right hemisphere lesion. Design: Open-label single-subject experimental ABAB withdrawal design. Patient: A right-handed man who, after a right frontal stroke, developed nonfluent aphasia, emotional aprosodia, and limb apraxia. Intervention: Escalating doses up to 20mg of bromocriptine in 2 separate phases. Main Outcome Measures: We measured verbal fluency (words/min in discourse, Thurstone letter fluency), expression of emotional prosody, and gesture production. Results: The patient showed substantial improvement in both verbal fluency measures and no significant improvement in gesture or emotional prosody. Verbal fluency improvements continued in withdrawal phases. Conclusions: Our results are less likely caused by practice or spontaneous recovery because we observed little improvement in emotional prosody and gesture tasks. Verbal fluency improvements during treatment and withdrawal phases suggest that the effects of bromocriptine may be long-lasting in its influence on the neural networks subserving verbal initiation. © 2001 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

Patients with probable Alzheimer's disease (AD) often have difficulties associated with semantic knowledge. Therefore, conceptual apraxia, a defect of action semantics and mechanical knowledge, may be an early sign of this disease. The Florida Action Recall Test (FLART), developed to assess conceptual apraxia, consists of 45 line drawings of objects or scenes. The subject must imagine the proper tool to apply to each pictured object or scene and then pantomime its use. Twelve participants with Alzheimer's disease (NINCDS–ADRDA criteria) and 21 age- and education-matched controls were tested. Nine Alzheimer's disease participants scored below a 2-standarddeviation cutoff on conceptual accuracy, and the three who scored above the cutoff were beyond a 2-standard-deviation cutoff on completion time. The FLART appears to be a sensitive measure of conceptual apraxia in the early stages of Alzheimer's disease. (JINS, 2000, 6, 265–270.)

The relationship between autonomic-visceral arousal and emotional experience is unclear. The attribution or cognitive-arousal theory of emotional experience posits that emotional experience is dependent on both visceral-autonomic nervous system feedback and the cognitive interpretation of the stimulus that induced this visceral activation. The finding that false cardiac feedback can alter emotional experience suggests that it may be the conscious perception that one is aroused, together with the cognitive interpretation of the stimulus that are important in developing emotional experience. Because the right hemisphere appears to play a special role in modulating arousal and interpreting emotional stimuli, it is possible that right hemisphere damage may interfere with developing the computations needed for emotional experience. To test this hypothesis we exposed men, both neurologically intact and those with right and left hemisphere lesions, to emotionally provocative pictures that were paired with false cardiac feedback, and examined the effects of this false feedback on their ratings of attractiveness of these pictures and their cardiac reactivity to this information. Subjects with left hemisphere damage, but not right hemisphere damage, showed significant changes in their emotional rating whereas control subjects showed marginal reactivity in their emotional ratings. Subjects with left hemisphere damage also showed significant changes in their cardiac reactivity. This finding is consistent with prior reports that indicate, when compared to right hemisphere damaged patients and normal controls, patients with left hemisphere lesions have an increased visceral-autonomic response to stimuli. These findings further provide support for the postulate that it is the cognitive interpretation of perceived physiological arousal together with the cognitive interpretation of the stimulus that is important in the development of emotional judgment and experience. These results do not support the approach-left hemisphere/avoidance-right hemisphere dichotomy, but instead suggest that left hemisphere damage increases reactivity to false feedback, and that the intact right hemisphere function integrates the cognitive interpretation of the emotional information and perceived arousal that lead to that emotional judgment. That these subjects showed no consistent relationship between their measures of cardiac reactivity and their ratings of attractiveness detracts from the James-Lange and attribution theories. These subjects also showed no consistent relationship between their knowledge of affective physiological reactivity and their ratings of attractiveness, or between their knowledge of physiological reactivity and actual measures of cardiac reactivity, suggesting that other neuropsychological factors are involved in making an emotional judgment.

Many patients with Alzheimer's disease (AD) are apraxic and the apraxia has been posited to be related to a loss of movement representations. Whereas patients with Alzheimer's disease have been reported to demonstrate normal motor learning on a rotor pursuit skill acquisition task, it is unknown whether AD subjects who are apraxic demonstrate normal skill-learning. We tested subjects with probable AD and normal controls on a rotor pursuit task. We also tested the AD subjects for ideomotor apraxia. Subjects with AD who were apraxic had normal motor learning. In addition, praxis score did not correlate with performance on the skill-acquisition task. The results suggest that ideomotor praxis and motor learning are at least partly dissociable.

We administered measures of object naming and action naming to matched groups of ten patients with Alzheimer's disease (AD) and ten normal control subjects. AD patients were impaired in both object and action naming, with object naming impaired to a significantly greater extent than action naming. This difference remained after controlling for the effects of word frequency. We propose that the pattern of pathological changes in AD impairs both conceptual and lexical retrieval systems for objects but only conceptual systems for actions. The similar patterns of error during the two tasks suggest quantitative rather than qualitative differences in the breakdown of the two abilities.

Two experiments were conducted to determine the effects of rootstock and bud-forcing treatment on scion budbreak and nursery tree growth of `Hamlin' orange. In Expt. 1, `Carrizo' citrange, `Swingle' citrumelo, and `Cleopatra' mandarin were budded with `Hamlin' orange and forced by one of the following methods: cutting off (purning away the rootstock top about 2 cm above the inserted scion bud); lopping (cutting half to two-thirds of the way through the rootstock stem 2 cm above the bud union, and breaking over the stem but leaving it attached); or bending (bending the rootstock shoot above the inserted scion bud and tying it to the base of the plant). For `Swingle' only, percent budbreak was less for bending or lopping compared to cutting off. For `Carrizo' and `Swingle', scion dry weights were less when plants were forced by cutting off compared to bending or lopping. For all rootstocks, whole-plant dry weights were greater for plants forced by bending and lopping than for plants forced by cutting off. In Expt. 2, scion buds on `Swingle' and `Cleopatra' plants were forced by the three methods in Expt. 1 plus combinations of bending with notching (making an inverted V incision through the bark and into the wood on the rootstock stem directly above the scion bud) and/or topping (removing the teminal 2 cm of rootstock shoot tips of plants forced by bending). Percent scion budbreak was high for `Cleopatra' plants regardless of forcing treatment. For `Swingle', scion budbreak was greater when bending was combined with notching than for bending alone. For `Cleopatra', plant dry weight was greatest for plants forced by lopping. When bending was combined with notching, or notching with topping, `Swingle' scion budbreak was comparable to cutting off, but plant dry weights were greater with these combination treatments than when cutting off was used.

Cholinergic neurons may influence the neural networks that subserve language. To learn if chollnergic drugs enhance the ability of anomic aphasic patients to name objects, we conducted studies of physostigmine and lecithin in three patients with anomia due to focal brain lesions. The flrst patient studied was amnestic and anomic, and presumed to be cholinergic-deficient due to a basal forebrain lesion. In open and blinded trials confrontation naming improved consistently with treatment but other cognitive measures did not. We subsequently tested two additional anomic patients with lesions outside the basal forebrain. We found improvement in confrontation naming but not other measures of cognition or mood during open-label physostigmine treatment. Physostigmine appears to improve naming in patients with anomia.

Cholinergic deficient states, such as in Alzheimer's disease, are associated with amnesia. Therapeutic trials with cholinergic augmentation in Alzheimer's disease have had only equivocal results, but mechanisms other than cholinergic deficiency may contribute to the memory deficit. Normally the diagonal band of Broca provides much of the hippocampal cholinergic input. To learn if amnesia secondary to cholinergic deficiency can be ameliorated by cholinergic augmentation, we treated an amnestic man who had a lesion located primarily in the right diagonal band of Broca with physostigmine and lecithin. During the initial best-dose-finding phase, he demonstrated an inverted U-shaped curve for immediate recall of word lists, with peak performances at 3.0 and 3.5 mg of physostigmine. Single photon emission tomography showed decreased blood flow in the medial temporal region ipsilateral to the lesion at baseline, with a reversal of the asymmetry on 3.5 mg of physostigmine. A follow-up double-blind, placebo-controlled study on 3.5 mg of physostigmine, however, failed to demonstrate that cholinergic treatment improved memory.

We have studied charging effects in a lateral split-gate quantum dot defined by metal gates in the two dimensional electron gas (2 DEG) of a GaAs/AlGaAs heterostructure. The gate structure allows an independent control of the conductances of the two tunnel barriers separating the quantum dot from the two 2 DEG leads, and enables us to vary the number of electrons that are localized in the dot. We have measured Coulomb oscillations in the conductance and the Coulomb staircase in current-voltage characteristics and studied their dependence on the conductances of the tunnel barriers. We show experimentally that at zero magnetic field charging effects start to affect the transport properties when both barrier conductances are smaller than the first quantized conductance value of a point contact at 2e2/h. The experiments are described by a simple model in terms of electrochemical potentials, which includes both the discreteness of the electron charge and the quantum energy states due to confinement.

Ballistic transport of electrons over several micrometers with excess energy of up to the order of the Fermi energy has been observed in the two-dimensional electron gas of a GaAs-${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As heterostructure. Quantum point contacts in an electron-focusing geometry have been used as a novel magnetic spectrometer to measure directly the kinetic energy of injected electrons. The observed energy gain is linear in the total applied voltage, and the slope allows a determination of the local voltage drop over the point contact.

Two experiments were conducted to determine the effects of rootstock shoot defoliation or shading on growth during the first two scion flushes of budded, container- ized, citrus nursery trees. Both experiments were conducted in a greenhouse with Cleopatra mandarin (Citrus reticulata Blanco) and Swingle citrumelo (C. paradisi (L.) Osb. x Poncirus trifoliata (L.) Raf.) seedlings budded with 'Hamlin' orange ( C. sinensis (L.) Osb.). Scion buds were forced by cutting off the rootstock shoots above the bud union or by bending the rootstock shoots and tying them to the base of the plants (bending). In one experiment, shoots from both rootstocks that were forced by bending received one of four defoliation treatments: treatments were 0%, 40%, 60%, or 85% (based on leaf area) defoliation for Cleopatra and 0%, 30%, 60%, or 100% defoliation for Swingle. In the second experiment, rootstock shoots of plants forced by bending were subjected to a maximum photosynthetic photon flux (PPF) of 820, 225, 90, or 30 μmolm -2 •s -1 . Growth of Cleopatra plants declined linearly with increasing levels of rootstock shoot defoliation. When rootstock shoot defoliation was ≤40%, whole-plant (minus rootstock shoot) dry weights were higher for plants forced by bending than for those forced by cutting off rootstock shoots. For Swingle, most growth responses to rootstock shoot defoliation were curvilinear. Higher levels of rootstock shoot defoliation resulted in less growth than lower defoliation levels. Low PPF reduced whole-plant (minus rootstock shoot) and root dry weights for both rootstocks compared to high PPF. For Cleopatra, whole-plant and scion dry weights were highest at the highest PPF. For Swingle, whole-plant and scion dry weights were highest at 225 μmolm -2 •s -1 . For both rootstocks, plants forced by bending had higher dry weights at 820 and 225 μmolm -2 •s -1 than plants forced by cutting off the rootstock shoots. For Swingle, most of the reduction in scion growth from rootstock shoot defoliation occurred during the first scion flush. Our results suggest that recently produced rootstock shoot photosynthates are the primary source of greater plant growth achieved by bending compared to cutting off rootstock shoots. rootstock shoots contribute (i.e., current pho- tosynthate or stored carbon reserves) to nurs- ery tree growth. If current photosynthates from the rootstock contribute significantly to nurs- ery tree growth, treatments that reduce the photosynthetic capacity of rootstock shoots would reduce growth of nursery trees forced by bending. The following experiments were conducted to determine the effects of shading or defoliation of rootstock shoots on growth of containerized citrus nursery trees forced by bending. Rootstock shoot defoliation and shad- ing also were compared to complete rootstock shoot removal to determine if rootstock shoots with low photosynthetic capacities contribute to nursery tree growth.

Patients with neuropathological changes of Alzheimer disease may not be demented during initial evaluation of memory disturbance. Understanding current issues regarding the patient with incipient degenerative dementia should help identify those at greatest risk for progression and may help delay onset of symptoms.

Liepmann posited that right hand preference relates to left hemisphere dominance for learned skilled movements. Limb apraxia, impairment of skilled movement, typically occurs in individuals with left hemisphere (LH) lesions. The occurrence of apraxia in right-handed individuals following right-hemisphere lesions appears to refute Liepmann's hypothesis. We studied the apraxia of a right-handed man, RF, following a right frontal lesion to determine whether his apraxia paralleled the apraxia seen following LH lesions. Results of behavioral testing indicated that, like individuals with apraxia following left frontal lesions, RF was better at gesture recognition than gesture production which was significantly impaired across tasks. Kinematic motion analyses of movement linearity, planarity, and the coupling of temporospatial aspects of movements substantiated the parallel impairments in RF and patients with LH apraxia. The impairment seen in our patient with crossed apraxia provides evidence for the fractionation of systems underlying hand preference and skilled movement.

A patient with a discrete lesion of the left, intralaminar thalamic, nuclei exhibited a paradoxical finding with regard to finger-tapping. Normal subjects typically reduce their tapping rate when performing simultaneous verbal activity. Tapping was impaired in our patient's contralesional hand on baseline trials; however, performing the controlled oral word association (COWA) task, while finger-tapping, normalized her deficit. Subsequent experiments showed that motoric tasks rather than cognitive aspects of the COWA task were critical in potentiating finger-tapping performance. A SPECT study performed at rest revealed focal perfusion asymmetries in motor and premotor cortices. Because the caudal intralaminar nuclei project heavily to the striatum, striatal deafferentiation may account for these asymmetries. These observations provide some insight into the influences of the caudal intralaminar thalamic nuclei on basal ganglia function and the basal ganglia's influence on motor gating.

Normal subjects often demonstrate a spatial bias on line bisection (LB) and cancellation (CA) tasks. We wanted to learn if horizontal spatial bias found in normal subjects may be dissociable into sensory-attentional (ATT) and motor-intentional (INT) subgroups similar to those described in brain-injured patients with spatial neglect. We studied the influence of ATT and INT factors on the spatial bias observed in normal subjects using a new technique that uncouples the direction of action from the direction of attention. This technique also allowed us to test both LB and CA tasks on the same individuals. Our results show that ATT bias significantly influenced performance on an LB task, whereas performance on a CA task was influenced by biases in both the ATT and INT systems. In addition, the overall bias on these two tasks reflects an interaction between the biases induced by the ATT and INT systems that may be in the same or different directions.

Although the pain behavior of some diagnostic groups has been shown to be reactive to social influences, the reactivity of pain behavior in a rheumatoid artritis (RA) population remains an open question. The authors in this article combined laboratory and self-report assessment techniques to examine the extent to which the pain report and behavior of 52 RA patients was susceptible to influence of social factors within the marital unit. The authors' findings suggest that (a) different types of spouse responsiveness (e.g., solicitous, punishing) may be viewed differently by the RA population than more general chronic pain populations; (b) the patient's perception of spouse responsiveness is a significant predictor of the pain behavior, whereas the spouse's perception of these same behaviors is not; and (c) the patient's perception of the spouse's responsive behavior adds significantly to the prediction of pain behavior over a model based on "disease impact" variables alone.

Neglect from bilateral brain injury can disrupt responses along space defined by the vertical and radial axes. The spatial reference frames for vertical and radial neglect remain largely undefined, however. The viewer centred system, for example, consists of retinocentric and cephalocentric/corporacentric frames. In the present study, different viewer centred reference frames were dissociated in a patient with combined far radial superior vertical neglect through performance of radial line bisections above and below eye level. To separate reference frames for vertical space, bisections were performed while the patient was lying sideways. Results suggest that this patient's neglect respected a retinotopic viewer centred reference frame.

We present experimental results on the conductance of a two-dimensional electron system of filling factor ${\ensuremath{\nu}}_{2\mathrm{D}}$ in the fractional quantum Hall regime, containing a constricted region of lower filling factor ${\ensuremath{\nu}}_{\mathit{c}}$. Conductance fluctuations are observed as a function of the voltage on the gate defining the constriction. The temperature dependence of the fluctuations exhibits three distinct regimes, governed by ${\ensuremath{\nu}}_{\mathit{c}}$. For temperatures below 100 mK, and for ${\ensuremath{\nu}}_{2\mathrm{D}}$=1/3, one anomalous peak increases to a value above the quantized conductance ${\ensuremath{\nu}}_{2\mathrm{D}}$(${\mathit{e}}^{2}$/h) of the bulk.

We have studied single electron charging effects in lateral quantum dots, defined by metal gates in the two dimensional electron gas of a GaAs/AlGaAs heterostructure. The charging effects cause periodic oscillations in the conductance versus gate voltage, where each period corresponds to a change of one electron in the dot. A study of the dependence of these Coulomb oscillations on the barrier conductances shows that charging effects become visible precisely when the barrier conductances become smaller than the quantized conductance value 2e2/h. The amplitude of the Coulomb oscillations increases gradually upon reducing the barrier conductances to a value much smaller than 2e2/h. We determine experimentally the total capacitance involved, and thereby the corresponding charging energy.

Periodic oscillations as a function of gate voltage have been observed in the conductance of a quantum dot defined in a two-dimensional electron gas by three pairs of gates. They are interpreted as Coulomb-blockade oscillations. The amplitude of the oscillations can be enhanced up to e 2 / h in the quantum Hall effect regime.

Quantum point contacts, shifted laterally by \ifmmode\pm\else\textpm\fi{}50 nm have been used to study the local electrostatic potential in the two-dimensional electron gas of a GaAs-${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As heterostructure. The resistance of the quantized plateaux is observed to vary with this lateral position. In one device an alternate suppression of the quantized resistance plateaux is observed, which we interpret as being due to an overlap of strong local potential fuctuations with the transverse profile of the wave functions in the quantum point contact.

Electronic transport in a 2-dimensional electron gas (2DEG) has been studied widely, in particular following the discovery of the quantum Hall effect (QHE). Initially, the integer effect (IQHE) was explained as to emerge in the full width of the 2DEG area, i.e. as a bulk effect 1. To explain the width of the quantized plateaux, the existence of localised states residing in the bulk was required.

We have constructed a novel magnetic spectrometer to study the dynamics of hot electrons and cool missing electron states injected by quantum point contacts in the two-dimensional electron gas of a GaAs-AlxGa1-xAs heterostructure. The mean free path of these quasi-particles is found to be longer than recent theoretical estimates. The injection energy of the particles is found to be anomalously low as the point contact approaches pinch-off, and also for high bias voltages.

Field-grown `Misty', `Star', and `Southmoon' southern highbush, and `Climax' rabbiteye blueberry plants were sprayed to drip with 0, 7.7 and 15.4 g·L–1 concentrations of hydrogen cyanamide in north central Florida on 17 Dec. 1997 and 6 Jan. 1998. Plants were dormant with slightly swollen flower buds (stage 2) at the times of applications. The extent and earliness of vegetative budbreak were increased by both hydrogen cyanamide sprays. Hydrogen cyanamide also increased mean fruit fresh weights and reduced fruit development periods for `Misty', `Southmoon' and `Climax' but not for `Star'. Yield response to hydrogen cyanamide was variable among cultivars. Fruit yields of `Misty' and `Climax' increased slightly by 7.7 g·L–1 sprays and decreased significantly by 15.4 g·L–1 sprays. In that case, increased fruit yields appeared to be the result of greater mean fruit fresh weights while reduced yields resulted from significant flower bud thinning that occurred at the highest spray concentration. Both hydrogen cyanamide spray concentrations increased fruit yield for `Southmoon' and decreased fruit yield for `Star' when compared to controls. Spray date had no effect on fruit yield and little effect on fruit development period. Hydrogen cyanamide has potential for increasing fruit quality and earliness of some blueberry cultivars that are grown in the lower southeastern United States.

We have studied the electron transport in a one-dimensional electron interferometer. It consists of a quantum dot, defined in a two-dimensional electron gas, to which quantum point contacts are attached. Discrete electronic states are formed due to the constructive interference of electron waves which travel along the circumference of the dot in one-dimensional magnetic edge channels. An artificial one-dimensional crystal has been fabricated, which consists of a sequence of 15 quantum dots, coupled by point contacts. The conductance of this device reveals the formation of a band structure, including the gaps between adjacent bands and the discrete electronic states from which the bands are constructed.

Two-year-old, container-grown `Misty' southern highbush blueberry plants were sprayed to drip with two concentrations of hydrogen cyanamide (HCN) (20.4 g·L–1 and 10.2 g·L–1) after exposure to 0, 150, or 300 hr of continuous chilling at 5.6°C. All plants were sprayed immediately after chilling and placed in a greenhouse for several weeks. The plants were moved outdoors during flowering to increase cross-pollination from nearby `Sharpblue' blueberry plants. HCN sprays killed some of the more advanced flower buds on shoot terminals and on small-diameter wood from the previous spring growth flush. Significantly greater flower bud mortality occurred for the 20.4 g·L–1 HCN sprays than for the 10.2 g·L–1 sprays. Flower buds subjected to 0 hr of chilling were more susceptible to spray burn than flower buds receiving 150 or 300 hr of chilling. Very little flower bud death occurred with the 10.2 g·L–1 HCN rate on plants receiving 300 hr of chilling. Vegetative budbreak was advanced for both HCN treatments compared to controls, regardless of chilling treatment. HCN-treated plants were heavily foliated at full bloom, while non-treated plants had very few to no leaves during bloom. HCN may be useful for stimulating vegetative growth in some southern highbush blueberry cultivars that suffer from poor foliation during flowering and fruit set.

Mature `Sharpblue' southern highbush and `Beckyblue' rabbiteye blueberry plants were mechanically pruned at two heights on three dates after fruit harvest during the 1994 growing season. No pruning had occurred for at least 3 years (`Sharpblue') or 5 years (`Beckyblue') before initiating experiment. Pruning heights were 45 and 85 cm and nonpruned for `Sharpblue' and 45 and 95 cm and nonpruned for `Beckyblue'. Pruning dates were 3, 6, and 9 weeks after peak harvest for each cultivar. Regrowth was measured in Mar. 1995 before initiation of spring growth. Pruning `Sharpblue' bushes to 45 cm increased new shoot number and mean and total shoot length but decreased fruit yield compared to the 90-cm pruning treatment. No difference in yield occurred between the 90-cm pruning treatment and the nonpruned control. As time between fruit harvest and pruning increased, new shoot number, mean and total shoot length, plant height, canopy volume, and fruit yield decreased. There was no difference in yield between the earliest pruning treatment and the control. For `Beckyblue', mean and total shoot length of regrowth and flower bud density decreased with increasing time from harvest to pruning. Yield data for `Beckyblue' were not collected in 1995 because of gall midge infestation.

Two experiments were conducted to determine the effects of bud forcing method and rootstock on scion budbreak and nursery tree growth of `Han-din' orange (Citrus sinensis Osb.) In Expt. 1, Carrizo citrange [Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.] (Ca), Swingle citrumelo [C. paradisi (L.) Osb. × P. trifoliata (L.) Raf.] (Sw), and Cleopatra mandarin (C. reticulata Blanco) (Cl) were budded with `Hamlin' orange and forced by cutting off the rootstock tops, lopping (cutting half way through the rootstock stem above the scion bud), or bending the rootstock top and tying it to the trunk). For Cl and Ca percent budbreak was high for all forcing methods. For Sw percent budbreak was greater for cutting off than for lopping or bending. For Sw and Ca, bending or lopping resulted in greater whole plant and scion dry weights than cutting off. Expt. 2 was similar to Expt. 1 except that bending was used alone, or in combination with notching (cutting an invertal v-shaped notch above the scion bud), or with topping the bent rootstock shoot. Scion budbreak of Sw plants was greater for bending + notching than for bending alone. Other effects of rootstock and forcing method for cutting off, bending or lopping were similar to those found in Expt. 1.

Six-year-old, field-grown `Beckyblue' and `Bonita' rabbiteye blueberries were sprayed to drip with Pro-Gibb (250 ppm GA3, 0.1% surfactant, pH 3.1). Two spray applications were made. The first spray was applied at 80-90% full bloom followed by a second spray 10 days later. Fruit were harvested at five dates, from 21 May until 1 July, 1992. GA3 increased fruit set and doubled total fruit yield for both cultivars compared to the control. Fruit yield was greater for the GA3 treatment than for the control at harvest dates 3 through 5 for 'Beckyblue', and dates 4 and 5 for 'Bonita'. Average berry weight for both cultivars and for both treatments declined as the season progressed. For `Beckyblue', average berry weight did not differ between treatments at most harvest dates. For 'Bonita', average berryweight was less for the GA3 treatment than for the control at harvest dates 3 through 5. GA3 increased yield of rabbiteye blueberry with little detrimental effect on fruit size. However, results from Georgia suggest that greater positive effects on fruit set should be possible.

We have measured the production of prompt positrons in pp collisions at √s = 63 GeV and y = 0 in the pT interval 0.12

Low-transverse-momentum photon production at the CERN ISR is compared in high- and low-multiplicity events. High-transverse-energy pp collisions and low-multiplicity ..cap alpha cap alpha.. and pp collisions are studied. Relative photon-to-charged-track production is found to be the same in pp minimum bias, ..cap alpha cap alpha.. minimum bias, and pp high-transverse-energy collisions, to within 15%. No low-P/sub T/ excess is seen; the limits are dominated by systematic uncertainties.

The production of inclusive prompt positrons in pp collisions at √ s = 63 GeV and θ cm = 90° has been measured over the p T interval 0.08 T GeV c . The e / π ratio rises from ∼ 2 × 10 −4 at p T = 0.9 GeV c to ∼ 1 × 10 −3 at p T = 0.1 GeV c . This is a factor of 6 higher than would be expected from the sum of hadronic bremsstrahlung and the semileptonic decay of charm.

We have measured the production of direct photons, π 0 's, and η's in p p and pp collisions at √ s =53 GeV in the range 2≈ p T ≈6 GeV/ c for the central rapidity region | y | 0.4. No statistically significant difference between pp and pp interactions is observed.

We have studied the inclusive production of the hadrons π±, K±, p, p , Λ, Λ , ρ and ⋉ in the central region at the ISR s = 53 GeV , in both pp and p p collisions. Differences are observed only for K±, p, and p production. We then study also correlations between low-pT pp and p p pairs in the two types of collisions, separating the contribution from baryon pair production and from the incident particles (stopping protons). We observe a positive correlation between two stopping protons; between the production of two pairs, and between a stopping proton and a pair production, there are negative correlations.

In a study ofpp collisions at\(\sqrt s = 63\) GeV with more than 29 GeV total transverse energy emitted into 1.8 units of rapidity in the central region, we have extracted a sample of 4-jet events and compared it with models of the two sources of 4-jet production: double bremsstrahlung and double parton scattering. The data cannot be described by bremsstrahlung alone, and we extract the fraction of 4-jet events attributed to double parton scattering for various definitions of the 4-jet sample. We determine the double parton scattering/2-jet yield ratio, and this leads to a determination of the proton radius. We discuss the implications of our observations for the general understanding of high-ΣET events.

We have determined the double inclusive cross-section for opposite-side high-p T photons and away-side jets withθ γ ≈θjet≈90° produced inpp collisions at the CERN Intersecting Storage Rings at\(\sqrt s = 63\) GeV. Under the assumption that these events arise predominantly from the QCD gluon Compton process we have calculated the gluon structure function in the range 0.15≦x≦0.30 at an average square of the four-momentum transfer of 40 GeV2/c2. The data favour a soft gluon distribution in the proton.

Bose-Einstein correlations between pions produced in the central region of rapidity in αα, pp and p p interactions have been studied at the ISR. The parameters r and τ c -often interpreted as the radius and depth of the π-emitting region - are found to be independent of incident particle type but to depend on the mean charged multiplicity. In high multiplicity events, the pions appear to originate from a larger space-time region.

The properties of high-ET events produced inpp collisions at\(\sqrt s \)=63 GeV have been studied at the CERN Intersecting Storage Rings. The fragmentation of the jets is found to be very similar to that of jets produced ine+e− annihilation and at the SPS\(p\bar p\) collider. We measure an excess of soft particles compared withe+e− events and this underlying event is found to be sensitive to the trigger. ThepT balance between the jets is measured. The distribution of charges in the jets indicates that a substantial fraction of the jets originate from valence quarks.

We have studied the processpp→γγ+X at\(\sqrt s = 63 GeV\) GeV in the central rapidity region. We report a positive signal at 96% C.L., a ratio γγ/e+e−=4.0±3.0 when the transverse momentum of each photon is above 2 GeV/c, and a cross-sectiondσ/dydMγγ=(5.5±2.7)×10−34 cm2/GeV when |y