Thermal formation of carbynes

We simulate the formation of $sp$ carbon chains (carbynes) by thermal decomposition of $sp^2$ carbon heated by a hot discharge plasma, by means of tight-binding molecular dynamics. We obtain and analyze the total quantity of carbynes and their length distribution as a function of temperature and density

The EFFects of Immigration on the Scale and Composition of Demand: A study of California establishments

We study potential economic benefits of immigration stemming from two factors: first, that immigrants bring not only their labor supply with them, but also their consumption demands; and second, that immigrants may have a comparative advantage in the production of ethnic goods. Using data on the universe of business establishments located in California between 1992 and 2002 matched with Census of Population data, we find some evidence that immigrant inflows boost employment in the retail sector, which is non-traded and a non-intensive user of immigrant labor. We find that immigration is associated with fewer stand-alone retail stores, and a greater number of large and in particular big-box retailers – evidence that likely contradicts a diversityenhancing effect of immigration. On the other hand, focusing more sharply on the restaurant sector, for which we can better identify the types of products consumed by customers, the evidence indicates that immigration is associated with increased ethnic diversity of restaurants.Effects of immigration, ethnic goods, consumption diversitY

The Effects of Immigration on the Scale and Composition of Demand: A study of California establishments

We study potential economic benefits of immigration stemming from two factors: first, that immigrants bring not only their labor supply with them, but also their consumption demands; and second, that immigrants may have a comparative advantage in the production of ethnic goods. Using data on the universe of business establishments located in California between 1992 and 2002 matched with Census of Population data, we find some evidence that immigrant inflows boost employment in the retail sector, which is non-traded and a non-intensive user of immigrant labor. We find that immigration is associated with fewer stand-alone retail stores, and a greater number of large and in particular big-box retailers – evidence that likely contradicts a diversityenhancing effect of immigration. On the other hand, focusing more sharply on the restaurant sector, for which we can better identify the types of products consumed by customers, the evidence indicates that immigration is associated with increased ethnic diversity of restaurants.Effects of immigration, ethnic goods, consumption diversity

Dual citizenship rights: do they make more and better citizens?

In the 1990s, Colombia, the Dominican Republic, Ecuador, Costa Rica and Brazil passed dual citizenship laws granting their expatriates the right to naturalize in the receiving country without losing their nationality of origin. I estimate the effects of these new laws on naturalization rates and labor market outcomes in the United States. Based on data from the 1990 and 2000 U.S. censuses, I find that immigrants recently granted dual nationality rights are more likely to naturalize. They also experience employment and earnings gains, together with drops in welfare use, suggesting that dual citizenship rights not only increase the propensity to naturalize but may also promote economic assimilation. The effects of dual citizenship on improved economic performance, if mediated through naturalization, are consistent with American citizenship conferring greater economic opportunities

Manipulation of charged particle beams through coherent interactions with crystals

In the last years, the field of channeling and related phenomena aimed to particle-beam steering has received a tremendous impulse by the advent of a new generation of silicon crystals, which resulted in significant performance increase and lead to the discovery of novel phenomena. The first key factor was the usage of silicon crystals exploiting secondary deformations, which provide extremely uniform bending an optimal sample thickness across the beam. Moreover, the holder to impart the primary curvature is designed to keep apart all the material but silicon from the trajectory of the beam. A second key factor which lead to performance improvement is the quality of the crystal surfaces by using properly tailored chemical etchings. In particular, the entry face of the crystal plays an important role, because it is the surface accepting incoming beam particles. Lastly, significant contribution was due to the characterization of the samples with a variety of techniques. A thorough characterization allows fine adjustment of the experimental parameters for crystal fabrication and certification of its quality prior to installation in the accelerator. In this thesis it will be shown the procedures for manufacturing of crystal realized at Sensors and Semiconductor Laboratory of Ferrara University. The fabrication methods, based on revisitations of micromachining techniques, allow obtaining high quality crystals, which lead to performance increase as well as to the discovery of new effects in the interaction with positively and negatively charged particle beams at CERN facilities. As it will be shown in this thesis, the geometry and the quality of the realized crystals allowed attaining a record 83% efficiency when operated to deflect a 400 GeV proton beam at the H8 line at CERN by means of planar channeling and contributed to the observation of volume reflection. The same crystal generation enabled to observe multiple volume reflection in both a series and in a single crystal and to successfully achieve deflection of negatively charged particle beams through either channeling or volume reflection. Coherent phenomena in crystals may be the basis for halo collimation for current hadron colliders (e.g. the LHC). An efficient collimation system is a necessary condition to run the accelerator at its top luminosity and to prevent damage of its sophisticated superconductive magnets. This smarted collimation scheme is currently being under investigation in the pilot UA9 experiments, which investigate crystal-assisted schemes for halo collimation in the CERN SPS through channeling of protons. The first and preliminary results of UA9 experiment shows good perspectives on the possibility to collimate the LHC beam by using bent crystals

Influence of incoherent scattering on stochastic deflection of high-energy negative particle beams in bent crystals

An investigation on stochastic deflection of high-energy negatively charged particles in a bent crystal was carried out. On the basis of analytical calculation and numerical simulation it was shown that it exists a maximum angle at which most of the beam is deflected. The existence of a maximum, which is taken in the correspondence of the optimal radius of curvature, is a novelty with respect to the case of positively charged particles, for which the deflection angle can be freely increased by increasing the crystal length. This difference has to be ascribed to the stronger contribution of incoherent scattering affecting the dynamics of negative particles that move closer to atomic nuclei and electrons. We therefore identified the ideal parameters for the exploitation of axial confinement for negatively charged particle beam manipulation in future high-energy accelerators, e.g., ILC or muon colliders

Spillovers from High-Skill Consumption to Low-Skill Labor Markets

Census data show that since 1980 low-skill workers in the United States have been increasingly employed in the provision of non-tradeable time-intensive services \u2013 such as food preparation and cleaning \u2013 that can be broadly thought as substitutes of home production activities. Meanwhile the wage gap between this sector and the rest of the economy has shrunk. If skilled workers, with their high opportunity cost of time, demand more of these time-intensive services, then wage gains at the top of the wage distribution (such as those observed in the last three decades) are expected to raise the consumption of these services, consistent with these stylized facts. Using both consumption expenditure data and city-level data on employment and wages of workers of different skills, we provide several pieces of evidence in favor of these demand shifts, and we argue that they provide a viable explanation for the growth in wages at the bottom quantiles observed in the last fifteen years

Spillovers from High-Skill Consumption to Low-Skill Labor Markets

Census data show that since 1980 low-skill workers in the United States have been increasingly employed in the provision of non-tradeable time-intensive services - such as food preparation and cleaning - that can be broadly thought as substitutes of home production activities. Meanwhile the wage gap between this sector and the rest of the economy has shrunk. If skilled workers, with their high opportunity cost of time, demand more of these time-intensive services, then wage gains at the top of the wage distribution (such as those observed in the last three decades) are expected to raise the consumption of these services, consistent with these stylized facts. Using both consumption expenditure data and city-level data on employment and wages of workers of different skills, we provide several pieces of evidence in favor of these demand shifts, and we argue that they provide a viable explanation for the growth in wages at the bottom quantiles observed in the last fifteen years.Census data show that since 1980 low-skill workers in the United States have been increasingly employed in the provision of non-tradeable time-intensive services - such as food preparation and cleaning - that can be broadly thought as substitutes of home production activities. Meanwhile the wage gap between this sector and the rest of the economy has shrunk. If skilled workers, with their high opportunity cost of time, demand more of these time-intensive services, then wage gains at the top of the wage distribution (such as those observed in the last three decades) are expected to raise the consumption of these services, consistent with these stylized facts. Using both consumption expenditure data and city-level data on employment and wages of workers of different skills, we provide several pieces of evidence in favor of these demand shifts, and we argue that they provide a viable explanation for the growth in wages at the bottom quantiles observed in the last fifteen years.Non-Refereed Working Papers / of national relevance onl

Remittances to Latin America from migrants in the United States: assessing the impact of amnesty programs

The magnitude of remittance flows to Latin America exceeds the combined inflows of foreign direct investment and official development assistance to the region. Since the United States is the destination country of the vast majority of migrants from Mexico, as well as from other Latin American countries, U.S. immigration policy can have a significant impact on the volume of remittances to the Latin American region. This paper studies how a generalized amnesty - a provision in the 1986 Immigration Reform and Control Act (IRCA), affected immigrants' remitting patterns. In models that control for immigrants' length of residence in the United States and for economic conditions in both the U.S. state of residence and the country of origin, we estimate substantial post-legalization drops in remittances sent home by Mexican-born migrants who legalized through IRCA. Given the potential positive impact of remittances on investment levels, entrepreneurship rates and the development of the financial sector, this finding underscores the importance of gaining a better understanding of the impact that immigration policies in immigrant-receiving countries may have on the stream of remittance flows to immigrant-sending communities in developing regions

Immigration and Product Diversity

We study the effects of immigration on the diversity of consumption choices. Data from California in the 1990s indicate that immigration is associated with fewer stand-alone retail stores, and a greater number of large and in particular big-box retailers – evidence that likely contradicts a diversity-enhancing effect of immigration. In contrast, focusing on the restaurant sector for which we can better identify the types of products consumed by customers, we find that immigration is associated with increased ethnic diversity of restaurants. This latter effect appears to come in part from the comparative advantage of immigrants in the production of ethnic goods.