38 research outputs found
Restoration of factorization for low hadron hadroproduction
We discuss the applicability of the factorization theorem to low-
hadron production in hadron-hadron collision in a simple toy model, which
involves only scalar particles and gluons. It has been shown that the
factorization for high- hadron hadroproduction is broken by soft gluons in
the Glauber region, which are exchanged among a transverse-momentum-dependent
(TMD) parton density and other subprocesses of the collision. We explain that
the contour of a loop momentum can be deformed away from the Glauber region at
low , so the above residual infrared divergence is factorized by means of
the standard eikonal approximation. The factorization is then restored in
the sense that a TMD parton density maintains its universality. Because the
resultant Glauber factor is independent of hadron flavors, experimental
constraints on its behavior are possible. The factorization can also be
restored for the transverse single-spin asymmetry in hadron-hadron collision at
low in a similar way, with the residual infrared divergence being
factorized into the same Glauber factor.Comment: 12 pages, 2 figures, version to appear in EPJ
Dynamics in online social networks
An increasing number of today's social interactions occurs using online
social media as communication channels. Some online social networks have become
extremely popular in the last decade. They differ among themselves in the
character of the service they provide to online users. For instance, Facebook
can be seen mainly as a platform for keeping in touch with close friends and
relatives, Twitter is used to propagate and receive news, LinkedIn facilitates
the maintenance of professional contacts, Flickr gathers amateurs and
professionals of photography, etc. Albeit different, all these online platforms
share an ingredient that pervades all their applications. There exists an
underlying social network that allows their users to keep in touch with each
other and helps to engage them in common activities or interactions leading to
a better fulfillment of the service's purposes. This is the reason why these
platforms share a good number of functionalities, e.g., personal communication
channels, broadcasted status updates, easy one-step information sharing, news
feeds exposing broadcasted content, etc. As a result, online social networks
are an interesting field to study an online social behavior that seems to be
generic among the different online services. Since at the bottom of these
services lays a network of declared relations and the basic interactions in
these platforms tend to be pairwise, a natural methodology for studying these
systems is provided by network science. In this chapter we describe some of the
results of research studies on the structure, dynamics and social activity in
online social networks. We present them in the interdisciplinary context of
network science, sociological studies and computer science.Comment: 17 pages, 4 figures, book chapte
Interventions for treating anxiety after stroke
Approximately 20% of stroke patients experience clinically significant levels of anxiety at some point after stroke. Physicians can treat these patients with antidepressants or other anxiety‐reducing drugs, or both, or they can provide psychological therapy. This review looks at available evidence for these interventions. This is an update of the review first published in October 2011. Objectives The primary objective was to assess the effectiveness of pharmaceutical, psychological, complementary, or alternative therapeutic interventions in treating stroke patients with anxiety disorders or symptoms. The secondary objective was to identify whether any of these interventions for anxiety had an effect on quality of life, disability, depression, social participation, caregiver burden, or risk of death. Search methods We searched the trials register of the Cochrane Stroke Group (January 2017). We also searched the Cochrane Central Register of Controlled Trials (CENTRAL; the Cochrane Library; 2017, Issue 1: searched January 2017); MEDLINE (1966 to January 2017) in Ovid; Embase (1980 to January 2017) in Ovid; the Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1937 to January 2017) in EBSCO; and PsycINFO (1800 to January 2017) in Ovid. We conducted backward citation searches of reviews identified through database searches and forward citation searches of included studies. We contacted researchers known to be involved in related trials, and we searched clinical trials registers for ongoing studies. Selection criteria We included randomised trials including participants with a diagnosis of both stroke and anxiety for which treatment was intended to reduce anxiety. Two review authors independently screened and selected titles and abstracts for inclusion. Data collection and analysis Two review authors independently extracted data and assessed risk of bias. We performed a narrative review. We planned to do a meta‐analysis but were unable to do so as included studies were not sufficiently comparable. Main results We included three trials (four interventions) involving 196 participants with stroke and co‐morbid anxiety. One trial (described as a 'pilot study') randomised 21 community‐dwelling stroke survivors to four‐week use of a relaxation CD or to wait list control. This trial assessed anxiety using the Hospital Anxiety and Depression Scale and reported a reduction in anxiety at three months among participants who had used the relaxation CD (mean (standard deviation (SD) 6.9 (± 4.9) and 11.0 (± 3.9)), Cohen's d = 0.926, P value = 0.001; 19 participants analysed). The second trial randomised 81 participants with co‐morbid anxiety and depression to paroxetine, paroxetine plus psychotherapy, or standard care. Mean levels of anxiety severity scores based on the Hamilton Anxiety Scale (HAM‐A) at follow‐up were 5.4 (SD ± 1.7), 3.8 (SD ± 1.8), and 12.8 (SD ± 1.9), respectively (P value < 0.01). The third trial randomised 94 stroke patients, also with co‐morbid anxiety and depression, to receive buspirone hydrochloride or standard care. At follow‐up, the mean levels of anxiety based on the HAM‐A were 6.5 (SD ± 3.1) and 12.6 (SD ± 3.4) in the two groups, respectively, which represents a significant difference (P value < 0.01). Half of the participants receiving paroxetine experienced adverse events that included nausea, vomiting, or dizziness; however, only 14% of those receiving buspirone experienced nausea or palpitations. Trial authors provided no information about the duration of symptoms associated with adverse events. The trial of relaxation therapy reported no adverse events. The quality of the evidence was very low. Each study included a small number of participants, particularly the study of relaxation therapy. Studies of pharmacological agents presented details too limited to allow judgement of selection, performance, and detection bias and lack of placebo treatment in control groups. Although the study of relaxation therapy had allocated participants to treatment using an adequate method of randomisation, study recruitment methods might have introduced bias, and drop‐outs in the intervention group may have influenced results. Authors' conclusions Evidence is insufficient to guide the treatment of anxiety after stroke. Further well‐conducted randomised controlled trials (using placebo or attention controls) are required to assess pharmacological agents and psychological therapies. Plain language summary Interventions for treating anxiety after stroke Review question To determine whether any treatments might reduce the symptoms of anxiety, and subsequently improve quality of life, for people who have had a stroke. Background Anxiety after stroke occurs frequently and can be treated with antidepressants or other anxiety‐reducing drugs, or both, or with psychological therapy. Study characteristics Evidence is current to January 2017. We found three studies with 196 stroke survivors who had received a diagnosis of anxiety. One study assessed the effect of a relaxation CD used five times a week for one month for participants with a diagnosis of anxiety. Two studies assessed the use of antidepressants in participants who had both anxiety and depression. Key results One study found that participants were less anxious three months after using a relaxation CD when compared with those who were given no therapy. One study reported that participants were less anxious when treated with an antidepressant medicine (paroxetine), or with paroxetine and psychotherapy, than with standard care. This study reported that half of the participants receiving paroxetine experienced side effects that included nausea, vomiting, or dizziness. The third study also reported that participants were less anxious when treated with an antidepressant (buspirone hydrochloride) than with standard care, and only 14% of those receiving buspirone hydrocholoride reported nausea or palpitations. Quality of the evidence We judged that the quality of this evidence was very low. Studies were few and each included a small number of participants. Studies assessing antidepressants did not include comparison with a placebo drug, and information in both study reports was insufficient to permit assessment of whether other biases had been introduced. The study of relaxation therapy was very small, with loss of two participants who used the CD, and the study recruitment process may have attracted participants who had a positive bias towards psychological therapies. Conclusion Current evidence is insufficient to guide the treatment of anxiety after stroke. Additional well‐conducted randomised trials are needed