Conductivity Induced by High-Field Terahertz Waves in Dielectric Material.

An intense, subpicosecond, relativistic electron beam traversing a dielectric-lined waveguide generates very large amplitude electric fields at terahertz (THz) frequencies through the wakefield mechanism. In recent work employing this technique to accelerate charged particles, the generation of high-power, narrow-band THz radiation was demonstrated. The radiated waves contain fields with measured amplitude exceeding 2 GV/m, orders of magnitude greater than those available by other THz generation techniques at a narrow bandwidth. For fields approaching the GV/m level, a strong damping has been observed in SiO_{2}. This wave attenuation with an onset near 850 MV/m is consistent with changes to the conductivity of the dielectric lining and is characterized by a distinctive latching mechanism that is reversible on longer timescales. We describe the detailed measurements that serve to clarify the underlying physical mechanisms leading to strong field-induced damping of THz radiation (hω=1.59 meV, f=0.38 THz) in SiO_{2}, a bulk, wide band-gap (8.9 eV) dielectric.

Experimental Characterization of Electron-Beam-Driven Wakefield Modes in a Dielectric-Woodpile Cartesian Symmetric Structure.

Photonic structures operating in the terahertz (THz) spectral region enable the essential characteristics of confinement, modal control, and electric field shielding for very high gradient accelerators based on wakefields in dielectrics. We report here an experimental investigation of THz wakefield modes in a three-dimensional photonic woodpile structure. Selective control in exciting or suppressing of wakefield modes with a nonzero transverse wave vector is demonstrated by using drive beams of varying transverse ellipticity. Additionally, we show that the wakefield spectrum is insensitive to the offset position of strongly elliptical beams. These results are consistent with analytic theory and three-dimensional simulations and illustrate a key advantage of wakefield systems with Cartesian symmetry: the suppression of transverse wakes by elliptical beams.

Challenges of an Autonomous Wildfire Geolocation System Based on Synthetic Vision Technology.

Thermographic imaging has been the preferred technology for the detection and tracking of wildfires for many years. Thermographic cameras provide some very important advantages, such as the ability to remotely detect hotspots which could potentially turn into wildfires if the appropriate conditions are met. Also, they can serve as a key preventive method, especially when the 30-30-30 rule is met, which describes a situation where the ambient temperature is higher than 30 ∘ C, the relative humidity is lower than 30%, and the wind speed is higher than 30 km/h. Under these circumstances, the likelihood of a wildfire outburst is quite high, and its effects can be catastrophic due to the high-speed winds and dry conditions. If this sort of scenario actually occurs, every possible technological advantage shall be used by firefighting teams to enable the rapid and efficient coordination of their response teams and to control the wildfire following a safe and well-planned strategy. However, most of the early detection methods for wildfires, such as the aforementioned thermographic cameras, lack a sufficient level of automation and usually rely on human interaction, imposing high degrees of subjectivity and latency. This is especially critical when a high volume of data is required in real time to correctly support decision-making scenarios during the wildfire suppression tasks. The present paper addresses this situation by analyzing the challenges faced by a fully autonomous wildfire detection and a tracking system containing a fully automated wildfire georeferencing system based on synthetic vision technology. Such a tool would provide firefighting teams with a solution capable of continuously surveilling a particular area and completely autonomously identifying and providing georeferenced information on current or potential wildfires in real time.

Planar-dielectric-wakefield accelerator structure using Bragg-reflector boundaries.

We report experimental measurements of narrow-band, single-mode excitation, and drive beam energy modulation, in a dielectric wakefield accelerating structure with planar geometry and Bragg-reflector boundaries. A short, relativistic electron beam (∼1 ps) with moderate charge (∼100 pC) is used to drive the wakefields in the structure. The fundamental mode of the structure is reinforced by constructive interference in the alternating dielectric layers at the boundary, and is characterized by the spectral analysis of the emitted coherent Cherenkov radiation signal. Data analysis shows a narrow-band peak at 210 GHz corresponding to the fundamental mode of the structure. Simulations in both 2D and 3D provide insight into the propagating fields and reproduction of the electron beams dynamics observables and emitted radiation characteristics.

Stable charged-particle acceleration and focusing in a laser accelerator using spatial harmonics.

Regarding the laser-driven acceleration of charged particles in photonic systems, a central unmet challenge is the achievement of simultaneous transverse and longitudinal stability at nonultrarelativistic energies. At such energies, Earnshaw's theorem [S. Earnshaw, Trans. Cambridge Philos. Soc. 7, 97 (1842)] indicates that a synchronous accelerating wave gives a defocusing effect. We present a scheme in which particles are accelerated by interaction with a resonant spatial harmonic and are focused by strong ponderomotive interaction with nonresonant spatial harmonics. We show that this scheme exhibits net transverse focusing and longitudinal stability, and we discuss its use in a compact laser accelerator.

Shewanella oneidensis MR-1 sensory box protein involved in aerobic and anoxic growth.

Although little is known of potential function for conserved signaling proteins, it is hypothesized that such proteins play important roles to coordinate cellular responses to environmental stimuli. In order to elucidate the function of a putative sensory box protein (PAS domains) in Shewanella oneidensis MR-1, the physiological role of SO3389 was characterized. The predicted open reading frame (ORF) encodes a putative sensory box protein that has PAS, GGDEF, and EAL domains, and an in-frame deletion mutant was constructed (ΔSO3389) with approximately 95% of the ORF deleted. Under aerated conditions, wild-type and mutant cultures had similar growth rates, but the mutant culture had a lower growth rate under static, aerobic conditions. Oxygen consumption rates were lower for mutant cultures (1.5-fold), and wild-type cultures also maintained lower dissolved oxygen concentrations under aerated growth conditions. When transferred to anoxic conditions, the mutant did not grow with fumarate, iron(III), or dimethyl sulfoxide (DMSO) as electron acceptors. Biochemical assays demonstrated the expression of different c-type cytochromes as well as decreased fumarate reductase activity in the mutant transferred to anoxic growth conditions. Transcriptomic studies showed the inability of the mutant to up-express and down-express genes, including c-type cytochromes (e.g., SO4047/SO4048, SO3285/SO3286), reductases (e.g., SO0768, SO1427), and potential regulators (e.g., SO1329). The complemented strain was able to grow when transferred from aerobic to anoxic growth conditions with the tested electron acceptors. The modeled structure for the SO3389 PAS domains was highly similar to the crystal structures of FAD-binding PAS domains that are known O2/redox sensors. Based on physiological, genomic, and bioinformatic results, we suggest that the sensory box protein, SO3389, is an O2/redox sensor that is involved in optimization of aerobic growth and transitions to anoxia in S. oneidensis MR-1.

Observation of nuclear fusion driven by a pyroelectric crystal.

While progress in fusion research continues with magnetic and inertial confinement, alternative approaches--such as Coulomb explosions of deuterium clusters and ultrafast laser-plasma interactions--also provide insight into basic processes and technological applications. However, attempts to produce fusion in a room temperature solid-state setting, including 'cold' fusion and 'bubble' fusion, have met with deep scepticism. Here we report that gently heating a pyroelectric crystal in a deuterated atmosphere can generate fusion under desktop conditions. The electrostatic field of the crystal is used to generate and accelerate a deuteron beam (> 100 keV and >4 nA), which, upon striking a deuterated target, produces a neutron flux over 400 times the background level. The presence of neutrons from the reaction D + D --> 3He (820 keV) + n (2.45 MeV) within the target is confirmed by pulse shape analysis and proton recoil spectroscopy. As further evidence for this fusion reaction, we use a novel time-of-flight technique to demonstrate the delayed coincidence between the outgoing alpha-particle and the neutron. Although the reported fusion is not useful in the power-producing sense, we anticipate that the system will find application as a simple palm-sized neutron generator.

Development and assessment of an ex-vivo bench model aimed at laparoscopic ureteric reconstructive techniques.

INTRODUCTION/BACKGROUND: Reconstructive and ablative urologic techniques require special technical mastery, especially the intracorporeal suturing. OBJECTIVE: To report the subjective evaluation of a versatile ex-vivo model aimed to practice laparoscopic ureteric reconstructive techniques (LURT) on box-trainer. STUDY DESIGN: The model is a continuous portion of porcine urinary bladder ("dilated pelvis"), the vesico-ureteral joint ("stenosis") and healthy ureter. All 127 participants (n = 119 urologists and n = 8 paediatric surgeons) performed on the model laparoscopic Anderson-Hynes dismembered pyeloplasty, and then, in the animal model, different LURT procedures (ureteroneocystostomy, ureteric reimplantation and/or dismembered pyeloplasty). The model was subjectively evaluated (face and content validity), through a 12 items questionnaire, based on a Likert scale (1-5 points) and a global question (1-10 points). RESULTS: The total mean rating for 11/12 items was very high (>4points). Only one was rated under 3 points. The overall total mean rating from 1 to 10 points was very high (9.19 ± 0.82 points). In 10/12 items, expert's feedback (content validity) prevailed over non-experts (face validity). DISCUSSION/CONCLUSION: The model was highly accepted for the practice of LURT techniques. Additionally, it is cost-effective, easy to assemble, ethically considerate, and realistic.

Validation of a new artificial model for simulated training of a laparoscopic vesicourethral anastomosis. / Validación de un nuevo modelo de simulación inorgánica para la anastomosis uretrovesical laparoscópica.

OBJECTIVE: The aim of this study is to prove the effectiveness of a low cost, artificial model for training of a laparoscopic urethrovesical anastomosis. MATERIALS AND METHODS: This study included urologists who attended specialised courses on laparoscopic radical prostatectomy (LRP) held during the period 2015 to 2017. They were divided into 2 groups according to their previous experience in laparoscopic surgery. The tasks performed on the artificial simulator were prostate resection, "task 1", and urethrovesical anastomosis, "task 2". Once these exercises were completed, the study participants filled in an anonymous questionnaire regarding their demographic data and experience level in laparoscopic surgery (LS). In addition, they gave their opinions about the didactic capacity of the artificial organ and evaluated its usefulness as a tool for LRP training. To demonstrate face and content validity, the participants judged the texture, consistency, morphology and evaluated its similarity to the real organ. The assessment was made with a five-point Likert scale. RESULTS: The students were divided into 2groups: 10 experts (Group E) and 12 novices (Group N). The only significant difference between the scores of novices and experts was regarding the inclusion of this tool in the training programs (Group E=5 points versus group N=4.4±0.59, P=.024). The experts' group rated all the items with higher scores than the novices' one. Regarding the general assessment of the simulation model, the novice participants gave an average score of 8.00±0.91 points out of 10, while the experts' group granted higher scores of 9.4±0,51. CONCLUSION: This artificial model has shown to have an elevated face, content and construct validity, as well being an optimal didactic tool for training in the techniques of prostate resection and laparoscopic urethrovesical anastomosis.

Neutron production from feedback controlled thermal cycling of a pyroelectric crystal.

The LLNL Crystal Driven Neutron Source is operational and has produced record ion currents of approximately 10 nA and neutron output of 1.9(+/-0.3)x10(5) per thermal cycle using a crystal heating rate of 0.2 degrees C/s from 10 to 110 degrees C. A 3 cm diameter by 1 cm thick LiTaO(3) crystal with a socket secured field emitter tip is thermally cycled with feedback control for ionization and acceleration of deuterons onto a deuterated target to produce D-D fusion neutrons. The entire crystal and temperature system is mounted on a bellows which allows movement of the crystal along the beam axis and is completely contained on a single small vacuum flange. The modular crystal assembly permitted experimental flexibility. Operationally, flashover breakdowns along the side of the crystal and poor emitter tip characteristics can limit the neutron source. The experimental neutron results extend earlier published work by increasing the ion current and pulse length significantly to achieve a factor-of-two higher neutron output per thermal cycle. These findings are reviewed along with details of the instrument.

Observation of acceleration and deceleration in gigaelectron-volt-per-metre gradient dielectric wakefield accelerators.

There is urgent need to develop new acceleration techniques capable of exceeding gigaelectron-volt-per-metre (GeV m(-1)) gradients in order to enable future generations of both light sources and high-energy physics experiments. To address this need, short wavelength accelerators based on wakefields, where an intense relativistic electron beam radiates the demanded fields directly into the accelerator structure or medium, are currently under intense investigation. One such wakefield based accelerator, the dielectric wakefield accelerator, uses a dielectric lined-waveguide to support a wakefield used for acceleration. Here we show gradients of 1.347±0.020 GeV m(-1) using a dielectric wakefield accelerator of 15 cm length, with sub-millimetre transverse aperture, by measuring changes of the kinetic state of relativistic electron beams. We follow this measurement by demonstrating accelerating gradients of 320±17 MeV m(-1). Both measurements improve on previous measurements by and order of magnitude and show promise for dielectric wakefield accelerators as sources of high-energy electrons.

La desesperacion: migrant and seasonal farm workers living with HIV/AIDS.

Migrant seasonal farm workers (MSFWs) in south Texas are predominantly Mexican American and represent one of the most impoverished and medically underserved populations in the United States. La Frontera is a collaborative partnership between the University of Texas Health Science Center at San Antonio, migrant organizations, and HIV service delivery organizations to study and address special needs of MSFWs in Hidalgo and Maverick counties of south Texas. The purpose of this qualitative study is to explore the health-seeking experiences of HIV-positive MSFWs living in the La Frontera service area. Denzin's interpretive interactionism methodology guided the study. Thirteen participants were interviewed and audiotaped as they described their experiences. Findings from content analysis of the interviews revealed a description of the life of an HIV-positive MSFW as la desesperacion (a separate way of life). After their diagnosis of HIV/AIDS, the major themes in their lives were living in secrecy (a silent cry), finding and receiving health care, and accepting the disease (may it be the will of God).

The care of women with AIDS: special needs and considerations.

The growing number of women being diagnosed with HIV/AIDS mandates the need to focus attention on the special needs of this population. Although women have many of the same devastating physical manifestations of HIV infection as men do, they face unique psychological and social issues that influence their ability to respond to their disease in the same ways. Women with HIV/AIDS are disproportionally poor or minority women who lack resources to maintain their health. It is impossible to address HIV infection in women without considering such factors as poverty, discrimination, and gender role expectations. This article uses a biopsychosocial framework to discuss a range of specific issues affecting the health and well-being of women with HIV/AIDS.

Stress in families of HIV-positive children living in south Texas.

The purpose was to conduct a pilot study of the extent of stress and differences in sources of stress experienced by HIV+ and HIV- caregivers of HIV+ children living in South Texas. 13 infected and 9 uninfected caregivers each completed the Questionnaire on Resources and Stress for their preschool-aged HIV+ child. Both HIV+ and HIV- caregivers experienced clinically significant stress. HIV+ caregivers reported that relative to the HIV- group, they perceived themselves to be in poorer physical or emotional health, to receive less social support from others, and to be less pessimistic about the future of their child or family.

Pediatric AIDS: impact on health systems.

For 9 years we have recognized HIV infection/AIDS as an unstoppable epidemic affecting infants, children, and adolescents as well as adults. Now we see the tremendous impact of this disease on the health systems of this country. During these past 9 years, we have witnessed the transformation of the epidemic from one primarily affecting male homosexuals to one invading the average US family through heterosexual and vertical transmissions and through needle-sharing practices of intravenous drug abuse. It has been estimated that 2% to 3% of the HIV infection/AIDS cases involve the pediatric age group. If 1.5 million Americans have HIV infection by 1991, as predicted, we should anticipate 30,000 to 45,000 infected pediatric patients by the end of that year. What has been the impact of this epidemic on the health systems involved in care, prevention, and research of pediatric HIV infection/AIDS? This article investigates that question.

Pediatric AIDS: a new health problem on the Texas horizon.

The current epidemic of HIV infection/AIDS initially limited to homosexual males appears to be spreading through heterosexual transmission and intravenous drug abuse. Infants, children, and adolescents are affected. We examine the modes of transmission of HIV infection in this population and the impact the spreading of this infection in the pediatric age group will have on Texas.

Pediatric AIDS: clinical presentation and diagnosis.

HIV infection/AIDS in infants and children under the age of 13 years expresses itself clinically so differently from the same infection in adults that a separate classification of the symptomatology has been adopted. Recurrent bacterial infections, as well as various opportunistic infections predominate, and while Kaposi's sarcoma is infrequent in pediatric patients, lymphomas occur with high frequency. The diagnosis of HIV infection/AIDS in children is presented.

Pediatric AIDS: treatment and outcome of patients.

The treatment of pediatric patients with HIV infection/AIDS is structured according to the clinical classification of the disease by the Centers for Disease Control; it involves prophylaxis, therapy against the human immunodeficiency virus, and therapy for the opportunistic infections and non-infectious complications of this disease. In spite of all these forms of therapy, the universal outcome of HIV infection/AIDS is the death of the patients. Prevention remains the only effective means to curb this epidemic.

Pediatric AIDS: systematic approach to patient management.

In order to provide comprehensive care to infants, children, and adolescents with HIV infection/AIDS, a systematic approach to clinical management had to be developed. This approach involves "case management" by experienced health professionals, including initial evaluation and needs assessment, planning of services, brokerage of services, continuity of intervention until an outcome is reached. The care is delivered in hospitals, clinics, homes, residential facilities, respite care centers, and hospices. The care team needs to be multidisciplinary and well integrated.

Pediatric AIDS: psychosocial impact.

There is no question that the domain of the American family has been invaded by the HIV infection/AIDS epidemic. The disease, and particularly its form affecting children (pediatric AIDS), has had marked psychosocial impact on patients and families (intellectual/cognitive, emotional/behavioral, spiritual, and financial) and on our society in general (adverse or favorable). These impacts of pediatric AIDS are discussed in the present communication.