b \bar b b\bar b production in proton-nucleus collisions at the LHC

A sizable rate of events, with several pairs of $b$-quarks produced contemporarily by multiple parton interactions, may be expected at very high energies as a consequence of the large parton luminosities. The production rates are further enhanced in hadron-nucleus reactions, which may represent a convenient tool to study the phenomenon. We compare the different contributions to $b{\bar b}b{\bar b}$ production, due to single and double parton scatterings, in collisions of protons with nuclei at the CERN-LHC.Comment: 13 pages, 4 figure

Scale Factor in Double Parton Collisions and Parton Densities in Transverse Space

The scale factor $\sigma_{eff}$, which characterizes double parton collisions in high energy hadron interactions, is a direct manifestation of the distribution of the interacting partons in transverse space, in such a way that different distributions give rise to different values of $\sigma_{eff}$ in different double parton collision processes. We work out the value of the scale factor in a few reactions of interest, in a correlated model of the multi-parton density of the proton recently proposed.Comment: 10 pages, 2 figure

Self-assessed neurological disturbances after surgical removal of impacted lower third molar: a pragmatic prospective study on 423 surgical extractions in 247 consecutive patients

OBJECTIVES: The aim of this study was to assess the combined role of current radiographic risk indicators and patient age in predicting lower lip sensitivity disturbances after surgical removal of impacted lower third molars. The question was which combinations indicate low or high risk. MATERIALS AND METHODS: A prospective study was implemented involving 247 consecutive outpatients who underwent 423 surgical extractions. The predictor variables were patient age and risk indicators observed on panoramic radiographs. The outcome variable was the incidence of self-assessed lip sensitivity alterations. The extractions were subdivided into four groups according to the predictors. RESULTS: Two hundred forty-five teeth were extracted in patients younger than 25 years and 178 in patients 25 years old or older; radiographic risk indicators were associated with 226 out of 423 teeth (53.43%). No permanent neurological damage was observed. Transient lip sensitivity alterations were observed in five cases (1.18%; 95% confidence interval\u2009=\u20090.4 to 2.7%), all in the older group with radiographic risk indicators. CONCLUSIONS: The data indicate a low overall incidence of transient lip sensitivity impairment that occurred only in the presence of radiographic risk indicators in patients aged 65\u200925 years. CLINICAL RELEVANCE: Informed consent should include the possibility of inferior alveolar nerve injury in mature patients with radiographic risk indicators. Prophylactic removal of impacted teeth with radiographic signs of risk may be indicated when the patient is not yet aged 25 years

Total Face Approach (TFA): a novel 3D approach to describe the main cephalometric craniomaxillofacial parameters

The aim of this study is to propose a 3D skeletal classification and relative normal values of reference. Method: from a pool of 271 cone-beam computerized tomography images 108 chinsummit examinations of the skull were selected and divided into 3 traditional skeletal classes. The same Cone-beam Computerized Tomography (CBCT) images were then assessed using the cephalometric multiplanar analysis following the total face approach protocol. Results: the results of this study indicate standard 3D cephalometric norms for the vertical and sagittal evaluation of the skull. Conclusions: data obtained from our measurements allowed the creation of intervals supplying nosological classification that could be used in orthodontics, orthognatic surgery and implant surgery in fully edentulous patients

Possible explanations for different surface quality in laser cutting with 1 micron and 10 microns beams

In laser　cutting　of　thick　steel　sheets,　quality　difference　is　observed　between　cut　surfaces　obtained　with 1 micron and 10 micron laser beams. This paper investigates physical mechanisms for this interesting and important problem of the wavelength dependence. First, striation generation process is described, based on a 3D structure of melt flow on a kerf front, which was revealed for the first time by our recent experimental observations. Two fundamental processes are suggested to explain the difference in the cut surface quality: destabilization of the melt flow in the central part of the kerf front and downward displacement of discrete melt accumulations along the side parts of the front. Then each of the processes is analyzed using a simplified analytical model. The results show that in both processes, different angular dependence of the absorptivity of the laser beam can result in the quality difference. Finally we propose use of radial polarization to improve the quality with the 1 micron wavelength

Double parton distributions in the leading logarithm approximation of perturbative QCD

Recent CDF measurements of the inclusive cross section for a double parton scattering attach a great importance to any theoretical calculations of two-particle distribution functions. Using a parton interpretation of the leading logarithm diagrams of perturbative QCD theory, generalized Lipatov-Altarelli-Parisi-Dokshitzer equations for the two-parton distributions are re-obtained. The solutions of these equations are not at all the product of two single-parton distributions what is usually applied to the current analysis as ansatz.Comment: 8 pages, LaTe

Same-sign W pair production as a probe of double parton scattering at the LHC

We study the production of same-sign W boson pairs at the LHC in double parton interactions. Compared with simple factorised double parton distributions (dPDFs), we show that the recently developed dPDFs, GS09, lead to non-trivial kinematic correlations between the W bosons. A numerical study of the prospects for observing this process using same-sign dilepton signatures, including same-sign WWjj, di-boson and heavy flavour backgrounds, at 14 TeV centre-of-mass energy is then performed. It is shown that a small excess of same-sign dilepton events from double parton scattering over a background dominated by single scattering WZ(gamma*) production could be observed at the LHC.Comment: 14 pages, 8 figures. Added references, slight changes in the text

Language control and parallel recovery of language in individuals with aphasia

Background: The causal basis of the different patterns of language recovery following stroke in bilingual speakers is not well understood. Our approach distinguishes the representation of language from the mechanisms involved in its control. Previous studies have suggested that difficulties in language control can explain selective aphasia in one language as well as pathological switching between languages. Here we test the hypothesis that difficulties in managing and resolving competition will also be observed in those who are equally impaired in both their languages even in the absence of pathological switching. Aims: To examine difficulties in language control in bilingual individuals with parallel recovery in aphasia and to compare their performance on different types of conflict task. Methods & procedures: Two right-handed, non-native English-speaking participants who showed parallel recovery of two languages after stroke and a group of non-native English-speaking, bilingual controls described a scene in English and in their first language and completed three explicit conflict tasks. Two of these were verbal conflict tasks: a lexical decision task in English, in which individuals distinguished English words from non-words, and a Stroop task, in English and in their first language. The third conflict task was a non-verbal flanker task. Outcomes & Results: Both participants with aphasia were impaired in the picture description task in English and in their first language but showed different patterns of impairment on the conflict tasks. For the participant with left subcortical damage, conflict was abnormally high during the verbal tasks (lexical decision and Stroop) but not during the non-verbal flanker task. In contrast, for the participant with extensive left parietal damage, conflict was less abnormal during the Stroop task than the flanker or lexical decision task. Conclusions: Our data reveal two distinct control impairments associated with parallel recovery. We stress the need to explore the precise nature of control problems and how control is implemented in order to develop fuller causal accounts of language recovery patterns in bilingual aphasia

Double parton scatterings in b-quark pairs production at the LHC

A sizable rate of events where two pairs of b-quarks are produced contemporarily is foreseen at the CERN LHC, as a consequence of the large parton luminosity. At very high energies both single and the double parton scatterings contribute to the process, the latter mechanisms, although power suppressed, giving the dominant contribution to the integrated cross section.Comment: 17 pages, 6 figure

Do Clinical Outcomes and Failure Rates Differ in Patients With Combined ACL and Grade 2 MCL Tears Versus Isolated ACL Tears?: A Prospective Study With 14-Year Follow-up

Background: A combined injury to the anterior cruciate ligament (ACL) and medial collateral ligament (MCL) is a common injury pattern encountered during clinical practice. Recent systematic reviews have found no consensus on the optimal method of managing this combined ligament injury pattern, and no long-term studies with modern techniques are available in the literature. Purpose: To compare 2 groups of patients who underwent isolated ACL reconstruction in terms of failures and clinical scores at long-term follow-up. In the first group were patients with isolated ACL tears (ACL group), while the second was composed of patients with combined ACL and MCL grade 2 tears (ACL + MCL group). Study Design: Cohort study; Level of evidence, 3. Methods: A total of 57 patients (37 in the ACL group and 20 in the ACL + MCL group) underwent isolated ACL reconstruction with a double-bundle technique between January and December 2005. Patients were contacted for scores on the International Knee Documentation Committee subjective form, Western Ontario and McMaster Universities Osteoarthritis Index, and Tegner activity scale as well as data regarding ipsilateral or contralateral revision ACL surgery. A 2-way analysis of variance for repeated measures was used to statistically assess the differences between the groups. Results: Overall, 49 patients (86%) completed the survey and were therefore included in the study. The minimum follow-up was 14.6 years (range, 14.1-15.2 years). There was a significant reduction in both groups of all the outcome scores between the intermediate and final-follow-up. The number of failures was 3 of 31 (9.7%) in the ACL group and 1 of 18 (5.5%) in the ACL + MCL group; this difference was not significant. Moreover, there were no clinical differences between the groups in terms of graft failures, contralateral lesions, and clinical scores. Conclusion: At 14-year follow-up, no clinical difference or increased failure rate was observed between the study groups, suggesting that isolated ACL reconstruction could represent an appropriate treatment for a combined ACL and MCL grade 2 lesion