The present work aims at reviewing our current understanding of fractal structures in the frame of colloid aggregation as well as the possibility they offer to produce novel structured materials. In ...particular, the existing techniques to measure and compute the fractal dimension df are critically discussed based on the cases of organic/inorganic particles and proteins. Then the aggregation conditions affecting df are thoroughly analyzed, pointing out the most recent literature findings and the limitations of our current understanding. Finally, the importance of the fractal dimension in applications is discussed along with possible directions for the production of new structured materials.
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•The existing techniques to measure and compute the fractal dimension are summarized•Aggregation conditions affecting the fractal dimension are analyzed•The importance of the fractal dimension in applications is discussed•Possible directions for the production of new structured materials are indicated
The laparoscopic approach is becoming increasingly frequent for many different surgical procedures. However, the combination of pneumoperitoneum and Trendelenburg positioning associated with this ...approach may increase the patient’s risk for elevated intracranial pressure (ICP). Given that the gold standard for the measurement of ICP is invasive, little is known about the effect of these common procedures on ICP.
We prospectively studied 40 patients without any history of cerebral disease who were undergoing laparoscopic procedures. Three different methods were used for non-invasive estimation of ICP: ultrasonography of the optic nerve sheath diameter (ONSD); transcranial Doppler-based (TCD) pulsatility index (ICPPI); and a method based on the diastolic component of the TCD cerebral blood flow velocity (ICPFVd). The ONSD and TCD were measured immediately after induction of general anaesthesia, after pneumoperitoneum insufflation, after Trendelenburg positioning, and again at the end of the procedure.
The ONSD, ICPFVd, and ICPPI increased significantly after the combination of pneumoperitoneum insufflation and Trendelenburg positioning. The ICPFVd showed an area under the curve of 0.80 95% confidence interval (CI) 0.70–0.90 to distinguish the stage associated with the application of pneumoperitoneum and Trendelenburg position; ONSD and ICPPI showed an area under the curve of 0.75 (95% CI 0.65–0.86) and 0.70 (95% CI 0.58–0.81), respectively.
The concomitance of pneumoperitoneum and the Trendelenburg position can increase ICP as estimated with non-invasive methods. In high-risk patients undergoing laparoscopic procedures, non-invasive ICP monitoring through a combination of ONSD ultrasonography and TCD-derived ICPFVd could be a valid option to assess the risk of increased ICP.
This paper reports on elastic scattering excitation functions for the reaction 9Li+4He measured at backward angles in the centre of mass energy range 5 MeV ≤ E≤c.m.9.5 MeV, with the aim of ...investigating the possible existence of molecular resonances which have been predicted to exist in the case of neutron-rich B-isotopes. Due to the short lifetime of 9Li, the experiment necessitated the use of inverse kinematics on a gaseous 4He target. The Thick Target Inverse Kinematics technique was used which allowed for the measurement of the full excitation function in a single 9Li run. Broad resonances were observed in the excitation region for 13B 15 MeV ≤ Ex≤20 MeV. To understand the nature of such broad structures, various theoretical attempts are reported concerning possible reaction mechanisms for this neutron rich reaction. The most promising approach to interpret the data is within the orbiting reaction scenario.
For the first time in an application to nuclear astrophysics, a process induced by the unstable 5He = (4He-n) nucleus, the 3He+5He→2α reaction, has been studied through the Trojan Horse Method (THM). ...For that purpose, the quasi-free (QF) contribution of the 9Be(3He,αα)4He reaction was selected at E3 He =4 MeV incident energy. The reaction was studied in a kinematically complete experiment following a recent publication, where for the quasi free contribution the momentum distribution between α and 5He particle cluster in the 9Be nucleus in the ground state have been extracted. The angular distribution of the QF 3He+5He→2α reaction was measured at θcm = 78°–115°. The energy dependence of the differential cross section of the 3He+5He→2α virtual reaction was extracted in the energy range Ecm = 0–650 keV. In conclusion, the total cross section obtained from the Trojan-horse method was normalized to absolute cross sections from a theoretical calculation in the energy range Ecm =300–620 keV.
The cosmological lithium problem (CLP) stems from the outstanding discrepancy between theoretical predictions and astronomical observations of primordial lithium abundances. For the radiogenic ...production of 7Li, 7Be plays a pivotal role in the Big Bang nucleosynthesis (BBN). Nevertheless, the data for neutron-induced 7Be destruction processes were still sparse, and especially lacked information on the contributions of transitions to the 7Li excited states. In this work, we have determined the 7Be\({(n,{p}_{0})}^{7}\)Li, 7Be\({(n,{p}_{1})}^{7}\)Li*, and 7Be\({(n,\alpha )}^{4}\)He reaction cross sections by means of the Trojan Horse method. The present and the previous data were analyzed together by a multichannel R-matrix fit, providing an improved uncertainty evaluation of the \((n,{p}_{0})\) channel and the first-ever quantification of the \((n,{p}_{1})\) contribution in the BBN-relevant energy range. We implemented the revised total reaction rate summing both the \((n,{p}_{0})\) and \((n,{p}_{1})\) contributions in a state-of-the-art BBN code PRIMAT. As a consequence, the present nuclear-physics data offers a reduction of the predicted 7Li abundance by about one-tenth, which would impose a stricter constraint on BBN and head us in the correct direction to the CLP solution.
The neutron capture reaction
10
B(n,
α
)
7
Li has been investigated via the Trojan Horse Method from 0 to 1 MeV. The
α
0
and
α
1
channels, corresponding to
7
Li in its g.s. and 1st excited level ...respectively, have been analyzed and cross sections have been measured for the two reaction channels. Angular distributions for the
11
B energy levels in the explored range have been extracted and compared with literature, while the J
π
of the level at
E
11
B
=
11.450
MeV (4 keV before the
α
emission threshold) has been clearly determined for the first time.
For the first time in an application to nuclear astrophysics, a process induced by the unstable
5
He = (
4
He-n) nucleus, the
3
He+
5
He
→
2
α
reaction, has been studied through the Trojan Horse ...Method (THM). For that purpose, the quasi-free (QF) contribution of the
9
Be(
3
He,
α
α
)
4
He reaction was selected at
E
3
He
=
4
MeV incident energy. The reaction was studied in a kinematically complete experiment following a recent publication (Spitaleri et al. in Eur Phys J A 56:18, 2020), where for the quasi free contribution the momentum distribution between
α
and
5
He particle cluster in the
9
Be nucleus in the ground state have been extracted. The angular distribution of the QF
3
He+
5
He
→
2
α
reaction was measured at
θ
cm
= 78
∘
–115
∘
. The energy dependence of the differential cross section of the
3
He+
5
He
→
2
α
virtual reaction was extracted in the energy range
E
cm
= 0–650 keV. The total cross section obtained from the Trojan-horse method was normalized to absolute cross sections from a theoretical calculation in the energy range
E
cm
=300–620 keV.
In the present work, the aggregation behavior of polymeric particles possessing different glass transition temperatures (i.e., different “softnesses”) has been studied to shed light on the interplay ...between aggregation and coalescence. In particular, the time evolution of the clusters hydrodynamic and gyration radii as well as of their structure factor has been monitored. With the help of an ad hoc developed deterministic model, based on population balance equations, it was possible to establish a link between the experimentally obtained light scattering data and the predicted particle size distribution. The simplicity of the model, involving one single adjustable parameter based on the coalescence characteristic time, allowed us to obtain a good accordance between simulations and experimental results with little computational effort.
A new study of the quasi-free contribution to the
3
He
+
9
Be
→
3
α
reaction (
Q
value = 19.004 MeV) at low
E
3
He
energy is presented. The reaction was studied in a kinematically complete experiment ...at beam energy of 4 MeV. To clarify the presence of the quasi-free mechanism, the
4
He
–
5
He
momentum distribution of the
9
Be
ground state was extracted. Standard tests were also carried out to confirm the presence of the quasi-free contribution and are reported in this work. The full width at half maximum of the
4
He
–
5
He
inter-cluster momentum distribution inside
9
Be
was measured with improved accuracy, by adopting several different approaches that all led to consistent results. These preliminary investigations on the reaction mechanism are fundamental for future studies employing the Trojan Horse Method, with the
5
He
unbound nucleus as a virtual projectile.
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