Disentangling Photodoping, Photoconductivity, and Photosuperconductivity in the Cuprates

The normal-state conductivity and superconducting critical temperature of oxygen-deficient YBa_{2}Cu_{3}O_{7-δ} can be persistently enhanced by illumination. Strongly debated for years, the origin of those effects-termed persistent photoconductivity and photosuperconductivity (PPS)-has remained an unsolved critical problem, whose comprehension may provide key insights to harness the origin of high-temperature superconductivity itself. Here, we make essential steps toward understanding PPS. While the models proposed so far assume that it is caused by a carrier-density increase (photodoping) observed concomitantly, our experiments contradict such conventional belief: we demonstrate that it is instead linked to a photo-induced decrease of the electronic scattering rate. Furthermore, we find that the latter effect and photodoping are completely disconnected and originate from different microscopic mechanisms, since they present different wavelength and oxygen-content dependences as well as strikingly different relaxation dynamics. Besides helping disentangle photodoping, persistent photoconductivity, and PPS, our results provide new evidence for the intimate relation between critical temperature and scattering rate, a key ingredient in modern theories on high-temperature superconductivity.

Quasiparticle tunnel electroresistance in superconducting junctions

The term tunnel electroresistance (TER) denotes a fast, non-volatile, reversible resistance switching triggered by voltage pulses in ferroelectric tunnel junctions. It is explained by subtle mechanisms connected to the voltage-induced reversal of the ferroelectric polarization. Here we demonstrate that effects functionally indistinguishable from the TER can be produced in a simpler junction scheme—a direct contact between a metal and an oxide—through a different mechanism: a reversible redox reaction that modifies the oxide’s ground-state. This is shown in junctions based on a cuprate superconductor, whose ground-state is sensitive to the oxygen stoichiometry and can be tracked in operando via changes in the conductance spectra. Furthermore, we find that electrochemistry is the governing mechanism even if a ferroelectric is placed between the metal and the oxide. Finally, we extend the concept of electroresistance to the tunnelling of superconducting quasiparticles, for which the switching effects are much stronger than for normal electrons. Besides providing crucial understanding, our results provide a basis for non-volatile Josephson memory devices.

The non-volatile switching of tunnel electroresistance in ferroelectric junctions provides the basis for memory and neuromorphic computing devices. Rouco et al. show tunnel electroresistance in superconductor-based junctions that arises from a redox rather than ferroelectric mechanism and is enhanced by superconductivity.

Prevalence and genetic diversity of Campylobacter spp. in the production chain of broiler chickens in Lebanon and its association with the intestinal protozoan Blastocystis sp

Campylobacter jejuni is recognized as the most common foodborne pathogen associated with human gastroenteritis worldwide. Broilers are frequently infected by the bacteria and are considered the main source of exposure to humans. However, despite its public health impact, no recent data are currently available in Lebanon about Campylobacter spp. in poultry and human population. Therefore, this study aimed to determine the prevalence and genetic diversity of Campylobacter spp. in 227 ceca and on 227 carcasses of broiler chickens collected in Lebanese slaughterhouses. Overall, the prevalence of Campylobacter was shown to reach 67.0% in ceca and 17.2% on carcasses of Lebanese poultry. The only 2 Campylobacter species identified were C. jejuni and C. coli, with a slightly higher prevalence of C. coli in ceca and of C. jejuni on carcasses. A high level of genetic diversity was reported among the 51 C. jejuni isolates selected, since 25 distinct profiles were identified according to the comparative genomic fingerprinting typing method based on a subset of 40 genes using the 90% similarity threshold. Predominant clusters observed in Lebanese poultry isolates were also frequently found among French human clinical cases, highlighting that broiler chickens represent a potential reservoir for human campylobacteriosis. In addition, a significantly higher prevalence of Campylobacter spp. was found in slaughterhouse workers than in a cohort of hospitalized patients with no contact with poultry, confirming that contaminated broiler chickens in slaughterhouse appeared to be a non-negligible source of Campylobacter spp. transmission. Interestingly, a significant association between Campylobacter spp. and Blastocystis sp. has been observed. This correlation suggested that the presence of Campylobacter spp. would be favored when Blastocystis sp. is present and, similarly, the absence of one would favor the absence of the other. This is the first large-scale investigation focusing on the impact of Campylobacter spp. in broiler chickens in Lebanon and confirmed the need to implement prevention and control measures in the poultry production to reduce the burden of campylobacteriosis in the human population.

[Factors associated with eating disorders in students of the University of Littoral Côte d'Opale]

AIMS

Our study aimed to observe the rate of eating disorders in first year public health students (allied medical and sports) of the University of the Littoral Opal Coast (ULCO) using the SCOFF-F (Sick, Control, One, stone, Fat, Food; French version) questionnaire and to compare morphological characteristics, level of physical condition, level of physical activity and sleep quality.

METHODS

Overall 642 subjects (459 women and 183 men) aged 22years (20.9±4.9years) participated in this study (Universanté-CEMHaVi). Weight, height, and fat mass were measured, and waist-to-hip ratio and body mass index (BMI) were calculated. The level of physical condition was evaluated using several physical tests: Leger and Boucher (20m) and shuttle run (4×10m), Sargent-test and handgrip strength. The SCOFF-F questionnaire followed by a clinical maintenance conducted by a professional was used to detect eating disorders. Several other questionnaires were used to evaluate the physical activity level; General Practice Assessment Questionnaire (GPAQ) and wellness. Sleep quality index was evaluated using Pittsburgh Sleep Quality Index (PSQI).

RESULTS

SCOFF-F was positive in 24.2% of women and 10.2% of men. In women, there were no significant differences between those who had a positive SCOFF-F screening and those who had a negative SCOFF-F screening regarding age, height, waist-to-hip ratio, level of physical condition measured and level of physical activity evaluated. However, significant differences were found between women who had a positive SCOFF-F screening and women who had a negative SCOFF-F screening regarding sleep quality, well-being score, BMI and fat mass. In men, significant differences were found between those who had a positive SCOFF-F screening and those who had a negative SCOFF-F screening regarding BMI and fat mass.

CONCLUSION

This study suggests that in both sexes, having a positive SCOFF-F screening is associated with higher BMI. In women, the increase in BMI and the perturbations in sleep quality and well-being score may indicate bulimia nervosa. The definition of a panel of possible factors associated with eating disorders can help in screening and early detection of eating disorders.

DXA-based variables and osteoporotic fractures in Lebanese postmenopausal women

INTRODUCTION

The aim of this study was to assess DXA-based variables (bone mineral density, bone mineral apparent density, compressive strength index of the femoral neck and trabecular bone score) in Lebanese postmenopausal women having presented a previous fracture.

MATERIALS AND METHODS

One thousand Lebanese postmenopausal women between 45 and 89 years participated in this study. The women were recruited by advertisements offering bone mineral density measurements at a reduced cost. Subjects with previous history of radiotherapy or chemotherapy were excluded. Informed written consent was obtained from all the participants.

RESULTS

Femoral neck compressive strength index (FN CSI) was significantly (P<0.001) associated with the presence of fracture using a simple logistic regression (odds ratio=0.51 [0.385-0.653]). When a multivariate logistic regression analysis was performed with the presence of fracture as a dependent variable and each of age, FN BMD and FN CSI as independent variables, only FN BMD (P=0.005) and FN CSI (P=0.004) were found to be associated with the presence of fracture.

CONCLUSION

This study suggests that FN CSI is associated with history of osteoporotic fractures in postmenopausal women. The use of FN CSI in clinical practice may help to identify patients with high risk of fracture.

LEVEL OF EVIDENCE

Epidemiological study, level IV.

Adult female football players have higher lumbar spine and hip bone mineral density than age- and body weight-matched controls

AIM

The aim of this study was to compare lumbar spine, total hip, femoral neck, total forearm and 1/3 Radius bone mineral density (BMD) in young female football players and age- and body weight- matched female controls (aged 18 to 30 years).

METHODS

This study included 18 female football players and 22 age- and body weight- matched sedentary females (aged 18 to 30 years). Weight and height were measured, and body mass index (BMI) was calculated. Daily calcium intake, daily protein intake and sleep duration were evaluated using validated questionnaires. BMD of the lumbar spine (L2-L4), the total hip (TH), the femoral neck (FN), the total forearm (TF) and the 1/3 Radius was assessed by dual-energy X-ray absorptiometry (DXA).

RESULTS

Height and BMI were not different between the two groups (football players and controls). L2-L4 BMD, TH BMD and femoral neck BMD were significantly higher in football players compared to controls (P<0.05). There were no significant differences between the two groups concerning total forearm BMD and 1/3 Radius BMD.

CONCLUSION

This study suggests that, in young adult females, football practice is associated with an increased BMD at the lumbar spine and the total hip but not at the total forearm.

Epidemiology of hip fractures in Lebanon: a nationwide survey

INTRODUCTION

Hip fractures are a reliable indicator of osteoporosis. Despite their importance, few studies have assessed their epidemiology in Lebanon and the Middle East.

HYPOTHESES

Hip fracture incidence rates in Lebanon approximate those of Northern countries, and show the same characteristics, particularly the exponential increase with age, higher incidence in women, and a recent trend of rate leveling in women but not in men.

MATERIALS AND METHODS

A national database of hip fracture cases admitted to hospitals in Lebanon in 2007 was created. Crude and age-adjusted incidence rates were calculated at 5-year intervals for individuals over age 50. These rates were also standardized to the 2000 United States population, and compared to those of other countries. Projected incidence rates in Lebanon in 2020 and 2050 were also calculated.

RESULTS

A total of 1199 patients were included in the study. The crude annual incidence rate in individuals over 50 was 147 per 100,000 individuals, 132 per 100,000 males and 160 per 100,000 females, with a female-to-male ratio of 1.2. The age-standardized annual incidence rates (per 100,000) were 180 in males and 256 in females. Assuming unchanged healthcare parameters, the projected crude incidence rates for people over 50 are expected to reach 174 and 284 per 100,000 in 2020 and 2050 respectively.

CONCLUSIONS

Lebanese hip fracture rates are lower than Northern countries, but show many similar characteristics such as an exponential increase with age, a higher incidence in women, and clues of a leveling of rates in women but not in men. Numbers are expected to increase substantially in the coming decades.

LEVEL OF EVIDENCE

Level IV. Epidemiological study.

Geometric indices of hip bone strength in young female football players

OBJECTIVE

The aim of this study was to compare geometric indices of hip bone strength in female football players and controls.

METHODS

18 adult female football players and 18 adult sedentary females participated in this study. The two groups were paired for age, weight and body mass index (BMI). Daily calcium intake (DCI) and daily protein intake (DPI) were evaluated by questionnaires. Total hip bone mineral density (BMD) and femoral neck BMD were measured by DXA. Cross-sectional area (CSA), an index of axial compression strength, section modulus (Z), an index of bending strength and cortical thickness (CT) were evaluated at the femoral neck (FN), the intertrochanteric (IT) and the femoral shaft (FS) regions by the hip structure analysis (HSA) program.

RESULTS

Age, weight, height, BMI, DCI and DPI were not different between the two groups. TH BMD, FN BMD, FN CSA, FN Z, FN CT, IT CSA, IT Z, IT CT, FS CSA and FS Z were significantly higher in football players compared to controls (crude percentage differences between the two groups varied between 8 and 19%; P<0.05). After adjusting for body weight using a one-way analysis of covariance (ANCOVA), TH BMD, FN BMD, FN CSA, FN Z, FN CT, IT CSA, IT Z, IT CT, FS CSA and FS Z remained significantly higher in football players compared to controls (adjusted percentage differences between the two groups varied between 7 and 17%; P<0.05).

CONCLUSION

This study suggests that, in adult females, football practice is associated with greater geometric indices of hip bone strength.

Geometric indices of hip bone strength in obese, overweight, and normal-weight adolescent boys

The aim of this study was to compare hip bone strength indices in obese, overweight, and normal-weight adolescent boys using hip structure analysis. After adjusting for weight, obese boys displayed lower intertrochanteric cross-sectional moment of inertia and femoral shaft cross-sectional moment of inertia and section modulus in comparison to normal-weight and overweight boys. This study suggests that in obese adolescent boys, femoral shaft bending strength is not adapted to the increased body weight.

INTRODUCTION

The influence of being obese or overweight on bone strength in adolescents remains controversial. The main aim of this study was to compare hip bone strength indices in obese, overweight, and normal-weight adolescent boys using hip structure analysis. The second aim of this study was to explore the influence of lean mass and fat mass on hip bone strength indices in the same population.

METHODS

This study included 70 adolescent boys (25 obese, 25 normal weight, and 20 overweight). The three groups (obese, overweight, and normal weight) were matched for maturity (Tanner stage) and age. Body composition and bone mineral density (BMD) were assessed by dual-energy X-ray absorptiometry (DXA). To evaluate hip bone strength, DXA scans were analyzed at the femoral neck (FN), the intertochanteric (IT), and the femoral shaft (FS) by the Hip Structure Analysis (HSA) program. Cross-sectional area (CSA), an index of axial compression strength, section modulus (Z), an index of bending strength, and cross-sectional moment of inertia (CSMI), an index of structural rigidity were measured from bone mass profiles.

RESULTS

Body weight, lean mass, fat mass and BMI were significantly higher in obese and overweight boys in comparison to normal-weight boys (P < 0.05). Total hip (TH) BMD and femoral neck (FN) BMD were significantly higher in obese and overweight boys in comparison to normal-weight boys (P < 0.05). After adjusting for age or maturation index, obese and overweight boys displayed significantly higher TH and FN BMD, CSA, CSMI, and Z of the three sites (FN, IT, and FS) in comparison to normal-weight boys (P < 0.05). However, after adjusting for weight, obese boys displayed significantly lower IT CSMI and FS CSMI and Z in comparison to normal-weight and overweight boys (P < 0.05).

CONCLUSIONS

This study suggests that in obese adolescent boys, intertrochanteric structural rigidity and femoral shaft structural rigidity and bending strength are not adapted to the increased body weight.