Measurement of the ratio h/e with a photomultiplier tube and a set of LEDs

We propose a laboratory experience aimed at undergraduate physics students to understand the main features of the photoelectric effect and to perform a measurement of the ratio h/e, where h is the Planck's constant and e is the electron charge. The experience is based on the method developed by Millikan for his measurements on the photoelectric effect in the years from 1912 to 1915. The experimental setup consists of a photomultiplier tube (PMT) equipped with a voltage divider properly modified to set variable retarding potentials between the photocathode and the first dynode, and a set of LEDs emitting at different wavelengths. The photocathode is illuminated with the various LEDs and, for each wavelength of the incident light, the output anode current is measured as a function of the retarding potential applied between the cathode and the first dynode. From each measurement, a value of the stopping potential for the anode current is derived. Finally, the stopping potentials are plotted as a function of the frequency of the incident light, and a linear fit is performed. The slope and the intercept of the line allow respectively to evaluate the ratio h/e and the ratio W/e, where W is the work function of the photocathode.Comment: 14 pages, 4 figure

Role of heat and mechanical treatments in the fabrication of superconducting Ba0.6K0.4Fe2As2 ex-situ Powder-In-Tube tapes

Among the recently discovered Fe-based superconducting compounds, the (K,Ba)Fe2As2 phase is attracting large interest within the scientific community interested in conductor developments. In fact, after some years of development, critical current densities Jc of about 105 A/cm2 at fields up to more than 10 T have been obtained in powder in tube (PIT) processed wires and tapes. Here we explore the crucial points in the wire/tape fabrication by means of the ex-situ PIT method. We focus on scaling up processes which are crucial for the industrial fabrication. We analyzed the effects on the microstructure of the different heat and mechanical treatments. By an extensive microstructural analysis correlated with the transport properties we addressed the issues concerning the phase purity, the internal porosity and crack formation in the superconducting core region. Our best conductors with a filling factor of about 30 heat treated at 800 C exhibited Tc = 38 K the highest value measured in such kind of superconducting tape. The microstructure analysis shows clean and well connected grain boundaries but rather poor density: The measured Jc of about 3 x 10^4 A/cm2 in self-field is suppressed by less than a factor 7 at 7 T. Such not yet optimized Jc values can be accounted for by the reduced density while the moderate in-field suppression and a rather high n-factor confirm the high homogeneity and uniformity of these tapes

A Comparison between Non-Localized Post-Activation Performance Enhancements Following Resistance Exercise for the Upper and the Lower Body

The aim of the present investigation was to compare the acute non-localized post-activation performance enhancement (PAPE) of an exercise protocol involving either the upper or the lower body muscles. Twenty-four resistance trained men participated in the present study and were randomly assigned to an upper body (UB) or to a lower body (LB) group. Both groups tested for upper and lower body power (bench press throw (BPT) and countermovement jump power (CMJP) tests). Participants in the UB group were tested pre and post a high-intensity (HI) and a high-power (POW) bench press protocol while participants in the LB group performed a HI squat and a jump session (POW). A significant group × time interaction was found for CMJP in HI (p = 0.012). Post hoc tests revealed that CMJP was elevated in UB group only (+1.6%; p = 0.025). No other significant interactions were detected. Results of this study indicate that a non-localized PAPE on the lower body may be induced by a HI bench press protocol while a HI squat protocol may not increase upper body power. In particular, the squat protocol performed in the present study (5 sets of 1 rep) may be too demanding to produce a non-localized PAPE

Immune contribution to tentacle regeneration in adult mollusc and cnidarian models

Histological studies focusing on the early cephalic tentacle regeneration in P. canaliculata, have demonstrated that wound closure and blastema formation took place within 24 h post amputation (hpa). A Matlab® plugin allowed the semi-automated identification and quantification of a phagocytic hemocyte sub-population in the blastema. Flow cytometry analysis showed that the injection of the phagocyte-specific drug Clophosome® (45 µg/g snail) could transiently remove circulating hemocytes, that recovered the pre-treatment level within 24 h. Consistently, histological experiment demonstrated that rare hemocytes were present in the early regenerating tentacles of Clophosome®-injected snail

Assessment of food contamination and dietary intake of lead and thallium in a Northern Italy population.

Lead and thallium are heavy metals released in the environment after natural and anthropogenic activities. Food and water intake are the major sources of human exposure to these elements. In this study, we aimed at characterizing lead and thallium content in foods consumed in Northern Italy population, in order to estimate the dietary intake of these metals. To do that we bought food samples in markets and groceries collected during the period from October 2016 to February 2017 in the Emilia Romagna region, and we measured their element content using inductively coupled plasma-mass spectrometry. Finally, after assessing dietary habits of an Emilia-Romagna community by using a validated food frequency questionnaire, we eventually estimated dietary intake of these metals in that community. In the 890 analyzed food samples, the highest lead contamination levels were found in seafood, vegetables, sweets and beverages. The estimated dietary intake of lead was 5.758 (interquartile range-IQR: 4.547-7.427) µg/day, corresponding to 0.089 (IQR: 0.069-0.113) µg/kg of body weight per day, with cereals, beverages and vegetables as major contributors. About thallium, one third of specimens showed very low levels below the limit of detection, with the highest contamination levels in vegetables, dry fruits and sweets. The dietary intake of thallium was 0.236 (IQR: 0.183-0.312) µg/day, mainly from vegetables, beverages, cereals and sweets. In conclusion, our study provides an estimation of lead and thallium intake in a Northern Italian community and shows a generally low exposure levels from dietary sources

Dietary intake of calcium, phosphorus and magnesium in a Northern Italian community.

Minerals are essential micronutrients for growth, development, and maintenance of healthy tissues, the long term insufficient intake of minerals may lead to bone demineralization and often requires the use of food supplements. The ratios of certain minerals intake like calcium and phosphorus are also proved to can affect the bioavailability of calcium and even lead to adverse health consequence. This study was designed to explore the dietary sources of calcium (Ca), phosphorus (P), and magnesium (Mg) and the ratios between different minerals (Ca/P). We measured the content of these elements in foods composing typical Italian diet using inductively coupled plasma-mass spectrometry and we estimated their daily dietary intakes assessing through a semi-quantitative food frequency questionnaire specifically developed within the European Prospective Investigation into Cancer and Nutrition (EPIC) study in a Northern Italian Community. In 890 analyzed food samples the main contributors to calcium are milk and dietary products, dry fruits, legumes and sweet products. Important sources of phosphorus are represented by dry fruits, legumes, milk and dairy products and meat. While dry fruits, legumes, cereals and fish symbolized the most important sources for magnesium. In our Italian population sample, the estimated median (interquartile range) dietary daily intakes are 786.3 (592.2-1062.7) μg/day for calcium; 1291.7 (1017.2-1591.4) mg/day for phosphorus and 323.2 (260.3-396.6) mg/day for magnesium. The calcium-phosphorus (Ca/P) ratio in this study was 0.63 (0.52-0.73). These values are in agreement with those suggested by European and International recommended intake for adult population, with the exception of calcium which is slightly lower than recommended values and suggest that this population does not present nutritional deficiencies requiring any supplementation

Dietary exposure estimates to fifteen trace elements in an adult population of Emilia Romagna region, Northern Italy

The health effects and the exposure levels of trace elements in humans are important public health topics. Assessing their dietary intake is fundamental to evaluate the long-term risks for public health and for food safety assessment. Since a priority of food safety regulatory agencies is to ensure the protection of consumers and to assess the health risks for the general population, to estimate the actual dietary intake of trace elements for comparison with the upper and lower tolerable levels is very important. In this study, we aimed to evaluate the dietary intake of several trace elements in an Italian community, namely of antimony, barium, beryllium, boron, cobalt, lithium, molybdenum, nickel, silver, strontium, tellurium, thallium, titanium, uranium, and vanadium. To do that, in 2016-2017 we collected a total of 908 food samples available in Italian markets and groceries from two Northern Italy provinces (Modena and Reggio Emilia), and we measured their trace element content through inductively-coupled plasma mass spectrometry. We also administered a validated semi-quantitative food frequency questionnaire to 708 residents (300 men and 48 women) in the Emilia-Romagna Region, to assess their dietary habits and eventually to estimate their dietary intake of the aforementioned trace elements. Overall, study results showed that in our population the dietary exposure levels to selected trace elements could be considered similar to that observed in other European and non-European populations. Though we cannot rule out the possibility that the dietary exposure estimates in the present study may not be representative of the population as a whole, our results provide a good and updated assessment of trace elements far frequently evaluated in a sample of Italian adult consumers from the Emilia Romagna region. Our findings finally suggest that our population should not be at risk of adverse health effects in relation to excess or deficiency of the investigated trace elements since the estimated dietary intake generally point out exposure levels within the safe range as far as indicated by recommendations of international agencies

A possible route to spontaneous reduction of the heat conductivity by a temperature gradient driven instability in electron-ion plasmas

We have shown that there exists low-frequency growing modes driven by a global temperature gradient in electron and ion plasmas, by linear perturbation analysis within the frame work of plasma Kinetic theory. The driving force of the instability is the local deviation of the distribution function from the Maxwell-Boltzmann due to global temperature gradient. Application to the intracluster medium shows that scattering of the particles due to waves excited by the instability is possible to reduce mean free paths of electron and ion down to five to seven order of magnitude than the mean free paths due to Coulomb collisions. This may provide a hint to explain why hot and cool gas can co-exist in the intracluster medium in spite of the very short evaporation time scale due to thermal conduction if the conductivity is the classical Spitzer value. Our results suggest that the realization of the global thermal equilibrium is postponed by the local instability which is induced for quicker realization of local thermal equilibrium state in plasmas. The instability provides a new possibility to create and grow cosmic magnetic fields without any seed magnetic field.Comment: Accepted for publication in ApJ: 16 pages, 1figur

Acute effects of a high volume vs. High intensity bench press protocol on electromechanical delay and muscle morphology in recreationally trained women

The purpose of the present investigation was to compare the acute responses on muscle architecture, electromechanical delay (EMD) and performance following a high volume (HV: 5 sets of 10 reps at 70% of 1 repetition maximum (1RM)) and a high intensity (HI: 5 sets of 3 reps at 90% of 1RM) bench press protocol in women. Eleven recreationally trained women (age = 23.3 ± 1.8 y; body weight = 59.7 ± 6.0 kg; height = 164.0 ± 6.3 cm) performed each protocol in a counterbalanced randomized order. Muscle thickness of pectoral (PEC MT) and triceps muscles (TR MT) were collected prior to and 15 min post each trial. In addition, EMD of pectoral (PEC EMD) and triceps (TR EMD) muscles were calculated during isometric bench press maximum force tests performed at the same timepoints (IBPF). Significantly greater increases in PEC MT (p < 0.001) and TR MT (p < 0.001) were detected following HV compared to HI. PEC EMD showed a significantly greater increase following HV compared to HI (p = 0.039). Results of the present study indicate that the HV bench press protocol results in greater acute morphological and neuromuscular changes compared to a HI protocol in women. Evaluations of muscle morphology and electromechanical delay appear more sensitive to fatigue than maximum isometric force assessments