Critical phenomena in active matter.

We investigate the effect of self-propulsion on a mean-field order-disorder transition. Starting from a φ^{4} scalar field theory subject to an exponentially correlated noise, we exploit the unified colored-noise approximation to map the nonequilibrium active dynamics onto an effective equilibrium one. This allows us to follow the evolution of the second-order critical point as a function of the noise parameters: the correlation time τ and the noise strength D. Our results suggest that the universality class of the model remains unchanged. We also estimate the effect of Gaussian fluctuations on the mean-field approximation finding an Ornstein-Zernike-like expression for the static structure factor at long wavelengths. Finally, to assess the validity of our predictions, we compare the mean-field theoretical results with numerical simulations of active Lennard-Jones particles in two and three dimensions, finding good qualitative agreement at small τ values.

Linac4 H⁻ ion sources.

CERN's 160 MeV H(-) linear accelerator (Linac4) is a key constituent of the injector chain upgrade of the Large Hadron Collider that is being installed and commissioned. A cesiated surface ion source prototype is being tested and has delivered a beam intensity of 45 mA within an emittance of 0.3 π ⋅ mm ⋅ mrad. The optimum ratio of the co-extracted electron- to ion-current is below 1 and the best production efficiency, defined as the ratio of the beam current to the 2 MHz RF-power transmitted to the plasma, reached 1.1 mA/kW. The H(-) source prototype and the first tests of the new ion source optics, electron-dump, and front end developed to minimize the beam emittance are presented. A temperature regulated magnetron H(-) source developed by the Brookhaven National Laboratory was built at CERN. The first tests of the magnetron operated at 0.8 Hz repetition rate are described.

Self-Sustained Density Oscillations of Swimming Bacteria Confined in Microchambers.

We numerically study the dynamics of run-and-tumble particles confined in two chambers connected by thin channels. Two dominant dynamical behaviors emerge: (i) an oscillatory pumping state, in which particles periodically fill the two vessels, and (ii) a circulating flow state, dynamically maintaining a near constant population level in the containers when connected by two channels. We demonstrate that the oscillatory behavior arises from the combination of a narrow channel, preventing bacteria reorientation, and a density-dependent motility inside the chambers.

Run-and-tumble particles in speckle fields.

The random energy landscapes developed by speckle fields can be used to confine and manipulate a large number of micro-particles with a single laser beam. By means of molecular dynamics simulations, we investigate the static and dynamic properties of an active suspension of swimming bacteria embedded into speckle patterns. Looking at the correlation of the density fluctuations and the equilibrium density profiles, we observe a crossover phenomenon when the forces exerted by the speckles are equal to the bacteria's propulsion.

First-passage time of run-and-tumble particles.

We solve the problem of first-passage time for run-and-tumble particles in one dimension. Exact expression is derived for the mean first-passage time in the general case, considering external force fields and chemotactic fields, giving rise to space-dependent swim speed and tumble rate. Agreement between theoretical formulae and numerical simulations is obtained in the analyzed case studies --constant and sinusoidal force fields, constant gradient chemotactic field. Reported findings can be useful to get insights into very different phenomena involving active particles, such as bacterial motion in external fields, intracellular transport, cell migration, animal foraging.

Status and operation of the Linac4 ion source prototypes.

CERN's Linac4 45 kV H(-) ion sources prototypes are installed at a dedicated ion source test stand and in the Linac4 tunnel. The operation of the pulsed hydrogen injection, RF sustained plasma, and pulsed high voltages are described. The first experimental results of two prototypes relying on 2 MHz RF-plasma heating are presented. The plasma is ignited via capacitive coupling, and sustained by inductive coupling. The light emitted from the plasma is collected by viewports pointing to the plasma chamber wall in the middle of the RF solenoid and to the plasma chamber axis. Preliminary measurements of optical emission spectroscopy and photometry of the plasma have been performed. The design of a cesiated ion source is presented. The volume source has produced a 45 keV H(-) beam of 16-22 mA which has successfully been used for the commissioning of the Low Energy Beam Transport (LEBT), Radio Frequency Quadrupole (RFQ) accelerator, and chopper of Linac4.

Numerical simulation of electromagnetic fields and impedance of CERN LINAC4 H(-) source taking into account the effect of the plasma.

Numerical simulation of the CERN LINAC4 H(-) source 2 MHz RF system has been performed taking into account a realistic geometry from 3D Computer Aided Design model using commercial FEM high frequency simulation code. The effect of the plasma has been added to the model by the approximation of a homogenous electrically conducting medium. Electric and magnetic fields, RF power losses, and impedance of the circuit have been calculated for different values of the plasma conductivity. Three different regimes have been found depending on the plasma conductivity: (1) Zero or low plasma conductivity results in RF electric field induced by the RF antenna being mainly capacitive and has axial direction; (2) Intermediate conductivity results in the expulsion of capacitive electric field from plasma and the RF power coupling, which is increasing linearly with the plasma conductivity, is mainly dominated by the inductive azimuthal electric field; (3) High conductivity results in the shielding of both the electric and magnetic fields from plasma due to the skin effect, which reduces RF power coupling to plasma. From these simulations and measurements of the RF power coupling on the CERN source, a value of the plasma conductivity has been derived. It agrees well with an analytical estimate calculated from the measured plasma parameters. In addition, the simulated and measured impedances with and without plasma show very good agreement as well demonstrating validity of the plasma model used in the RF simulations.

Effective run-and-tumble dynamics of bacteria baths.

E. coli bacteria swim in straight runs interrupted by sudden reorientation events called tumbles. The resulting random walks give rise to density fluctuations that can be derived analytically in the limit of non-interacting particles or equivalently of very low concentrations. However, in situations of practical interest, the concentration of bacteria is always large enough to make interactions an important factor. Using molecular dynamics simulations, we study the dynamic structure factor of a model bacterial bath for increasing values of densities. We show that it is possible to reproduce the dynamics of density fluctuations in the system using a free run-and-tumble model with effective fitting parameters. We discuss the dependence of these parameters, e.g., the tumbling rate, tumbling time and self-propulsion velocity, on the density of the bath.

Status of the plasma generator of the superconducting proton linac.

In the framework of the superconducting proton linac (SPL) study at CERN, a new non-cesiated H(-) plasma generator driven by an external 2 MHz RF antenna has been developed and successfully operated at repetition rates of 50 Hz, pulse lengths of up to 3 ms, and average RF powers of up to 3 kW. The coupling efficiency of RF power into the plasma was determined by the cooling water temperatures and the analysis of the RF forward and reflected power and the antenna current and amounts to 50%-60%. The plasma resistance increases between 10 kW and 40 kW RF power from about 0.45 Ω to 0.65 Ω. Measurements of RF power dissipated in the ferrites and the magnets on a test bench show a 5-fold decrease of the power losses for the magnets when they are contained in a Cu box, thus validating the strategy of shielding the magnets with a high electrical conductivity material. An air cooling system was installed in the SPL plasma generator to control the temperatures of the ferrites despite hysteresis losses of several Watts.

Optical emission spectroscopy of the Linac4 and superconducting proton Linac plasma generators.

CERN's superconducting proton Linac (SPL) study investigates a 50 Hz high-energy, high-power Linac for H(-) ions. The SPL plasma generator is an evolution of the DESY ion source plasma generator currently operated at CERN's Linac4 test stand. The plasma generator is a step towards a particle source for the SPL, it is designed to handle 100 kW peak RF-power at a 6% duty factor. While the acquisition of an integrated hydrogen plasma optical spectrum is straightforward, the measurement of a time-resolved spectrum requires dedicated amplification schemes. The experimental setup for visible light based on photomultipliers and narrow bandwidth filters and the UV spectrometer setup are described. The H(α), H(ß), and H(γ) Balmer line intensities, the Lyman band and alpha transition were measured. A parametric study of the optical emission from the Linac4 ion source and the SPL plasma generator as a function of RF-power and gas pressure is presented. The potential of optical emission spectrometry coupled to RF-power coupling measurements for on-line monitoring of short RF heated hydrogen plasma pulses is discussed.

Statistical mechanical approach to secondary processes and structural relaxation in glasses and glass formers: a leading model to describe the onset of Johari-Goldstein processes and their relationship with fully cooperative processes.

The interrelation of dynamic processes active on separated time-scales in glasses and viscous liquids is investigated using a model displaying two time-scale bifurcations both between fast and secondary relaxation and between secondary and structural relaxation. The study of the dynamics allows for predictions on the system relaxation above the temperature of dynamic arrest in the mean-field approximation, that are compared with the outcomes of the equations of motion directly derived within the Mode Coupling Theory (MCT) for under-cooled viscous liquids. By varying the external thermodynamic parameters, a wide range of phenomenology can be represented, from a very clear separation of structural and secondary peak in the susceptibility loss to excess wing structures.

Thermodynamic first order transition and inverse freezing in a 3D spin glass.

We present a numerical study of the random Blume-Capel model in three dimensions. The phase diagram is characterized by spin-glass-paramagnet phase transitions of both first and second order in the thermodynamic sense. Numerical simulations are performed using the exchange Monte Carlo algorithm, providing clear evidence for inverse freezing. The main features at criticality and in the phase coexistence region are investigated. We are not privy to other 3D short-range systems with quenched disorder undergoing inverse freezing.

Commissioning of the new H- source for Linac4.

As part of the CERN accelerator complex upgrade, a new linear accelerator for H(-) (Linac4) will start its operation in 2014. The source for this linac will be a 2 MHz rf driven H(-) source which is a copy of the very successful source from DESY. In this paper the design and the first results of the commissioning are reported. The commissioning has progressed successfully, and no major obstacles have been identified which will prevent reaching the goal of 80 mA H(-) beam current, 45 keV beam energy, 0.4 ms pulse length, and 2 Hz repetition rate. The source is producing up until now a stable beam of 23 mA, 35 keV, and with a repetition rate of 0.83 Hz.

High duty factor plasma generator for CERN's Superconducting Proton Linac.

CERN's Linac4 is a 160 MeV linear accelerator currently under construction. It will inject negatively charged hydrogen ions into CERN's PS-Booster. Its ion source is a noncesiated rf driven H(-) volume source directly inspired from the one of DESY and is aimed to deliver pulses of 80 mA of H(-) during 0.4 ms at a 2 Hz repetition rate. The Superconducting Proton Linac (SPL) project is part of the luminosity upgrade of the Large Hadron Collider. It consists of an extension of Linac4 up to 5 GeV and is foreseen to deliver protons to a future 50 GeV synchrotron (PS2). For the SPL high power option (HP-SPL), the ion source would deliver pulses of 80 mA of H(-) during 1.2 ms and operate at a 50 Hz repetition rate. This significant upgrade motivates the design of the new water cooled plasma generator presented in this paper. Its engineering is based on the results of a finite element thermal study of the Linac4 H(-) plasma generator that identified critical components and thermal barriers. A cooling system is proposed which achieves the required heat dissipation and maintains the original functionality. Materials with higher thermal conductivity are selected and, wherever possible, thermal barriers resulting from low pressure contacts are removed by brazing metals on insulators. The AlN plasma chamber cooling circuit is inspired from the approach chosen for the cesiated high duty factor rf H(-) source operating at SNS.

Urinary dosage of nuclear matrix protein 22 (NMP22) like biologic marker of transitional cell carcinoma (TCC): a study on patients with hematuria.

UNLABELLED: This study was performed to evaluate the clinical usefulness of nuclear matrix protein 22 (NMP22) as urinary marker for bladder cancer and to define its role in comparison with urinary cytology in diagnostic management of patients with hematuria. MATERIALS AND METHODS: NMP22 values in voided urines were determined on 90 patients (81 males, 14 females) with macro or microscopical hematuria, using the NMP22 test-kit (Matritech) based on an enzyme-linked immuno-sorbant assay. The cut-off value for positive samples was 10U/ml. In all cases urinary cytology was performed on the same sample. Patients suspected for the presence of a transitional cell carcinoma (TCC) underwent cytoscopic control. Statistical signification of the medians difference was analyzed using both medians variance analysis and Student's test. The increasing in diagnostic predictivity was analyzed elaborating contingency tables and performing consequently chi 2 test. RESULTS: 32 cases of TCC were endoscopically detected: sensitivity of cytopathology was 75.8%, specificity was 62.5%. The positive predictive value of the cytology was 22% and negative predictive value was 49%. The results concerning NMP22 dosage are: sensitivity 84%, specificity 62%. Positive predictive value of NMP22 test was 30% and predictive negative value was 40%. No significant differences between cytopathology and NMP22 dosage were founded (p > 0.995). Considering both cytopathology and NMP22 dosage, sensitivity was 82.7% and specificity raises up to 90.6% with statistical signification (P < 0.001). The median NMP22 value in patients affected by TCC endoscopically confirmed (group A) was 55.2 U/ml, in subjects with no evidence of malignancy (group B) it was 19.1 U/ml. The difference shows statistical signification (p < 0.001). In 20 cases with TCC, hystological grading were available and were investigated in relationship with NMP22 title in U/ml, median NMP22 value for each grade was: CIS = 102 U/ml, G0 = 35 U/ml, G1 = 30 U/ml, G2 = 66 U/ml, G3 = 54 U/ml. It can be assessed that NMP22 test is useful in differentiating subjects affected by TCC from subjects with no evidence of malignancy and may help in early diagnosis of TCC and in predicting recurrent even if low grade tumors especially if used in association with cytology and endoscopy.

[Four corner bladder base and bladder neck suspension with intraosseous anchorage in the treatment of moderate cystocele]. / La sospensione della base e del collo vescicale ai quattro angoli con ancoraggio intraosseo per la correzione del cistocele moderato.

During the last 10 years the original Pereyra technique of needle bladder neck suspension has been object of more than 36 modifications with the goal to improve long term results and to enhance feasibility. It represents also a part of the so called four corner bladder and bladder neck suspension (anterior suspending sutures) which is at present a reliable and durable manner to manage mild to moderate cystocele; this procedure reestablishes safely and simply support to bladder base, bladder neck and urethra preventing the onset of a denovo stress urinary incontinence. Complications include post-operative pain which could represent a problem in about 16% of the patients: it has been related to the entrapment of the ileoinguinal nerve between prolene sutures and rectus fascia and may be responsible of a delay in the re-establishment of a normal voiding pattern due to the pain elicited during any rectus muscle contraction. We propose a refinement of this procedure which includes the osseous anchoring of the suspending suture through the Mitek G II anchor system. Reduction in postoperative pain and fast recovery of a normal voiding pattern soon after surgery seems to be the most important result of this modification. Osteitis pubis has not been noted. Any improvement in long term durability of the procedure has not yet been determined due to the short follow-up and limited series of cases and the need for subsequent long term follow-up.