Atom-field dynamics in curved spacetime

Some aspects of atom-field interactions in curved spacetime are reviewed. Of great interest are radiative processes arising out of Rindler and black hole spacetimes, which involve the role of Hawking-Unruh effect. The conventional understandings of atomic radiative transitions and energy level shifts are reassessed in curved spacetime. On one hand, the study of the role played by spacetime curvature in quantum radiative phenomena has implications for fundamental physics, notably the gravity-quantum interface. In particular, one examines the viability of Equivalence Principle, which is at the heart of Einstein's general theory of relativity. On the other hand, it can be instructive for manipulating quantum information and light propagation in arbitrary geometries. Some issues related to nonthermal effects of acceleration are also discussed.Comment: 31 pages, 5 figure

Seeing dark matter via acceleration radiation

Notwithstanding an impressive $\sim 27\%$ share of the total energy budget of our Universe, dark matter (DM) has by far remained elusive for any direct observations. Given its ubiquity, there is a genuine expectation that astrophysical black holes (BHs) surrounded by DM should leave imprints on the gravitational waves germinating from BH mergers. Theoretical models of DM offer a landscape of possibilities. Of these, perfect fluid dark matter (PDFM) is a novel candidate model which has been of considerable interest recently. In this Letter, employing the well-known \textit{quantum optical} approach, we investigate the possibility of catching DM signatures via acceleration radiation emitted by a detector (e.g. an atom) falling freely within a PFDM-surrounded Schwarzschild BH. The setup comprises a Casimir-type apparatus where the detector interacts with the field and excites thereby in a typical Unruh manner. We observe that our DM candidate, though offering contributions to the spacetime geometry on a classical footing, could however leave its potential quantum imprints in the radiation flux. Specifically, one notes that compared to a pure Schwarzschild BH, PFDM can markedly reduce particle emission as long as its density remains below a critical value, and vice versa. This novel study, bringing DM into Casimir physics, may possibly provide insights into the future table-top experiments in analogue gravity paradigm.Comment: 8 pages, 6 figure

On the microstructure of higher-dimensional Reissner-Nordstr\"om black holes in quantum regime

Thermodynamic Riemannian geometry provides great insights into the microscopic structure of black holes (BHs). One such example is the Ruppeiner geometry which is the metric space comprising the second derivatives of entropy with respect to other extensive variables of the system. Reissner-Nordstr\"om black holes (RNBHs) are known to be endowed with a flat Ruppeiner geometry for all higher spacetime dimensions. However this holds true if one invokes classical gravity where the semi-classical Bekenstein-Hawking entropy best describes the thermodynamics of the system. If the much deeper string and quantum gravity theories entail modifications to BH entropy, this prompts the question whether the Ruppeiner flatness associated with higher dimensional RNBHs still persists. We investigate this problem by considering non-perturbative (exponential) and perturbative (logarithmic) modifications to BH entropy of a $5$D RNBH. We find that while the case is so for larger (classical) geometries, the situation is radically altered for smaller (quantum) geometries. Namely, we show surprising emergence of multiple phase transitions that depend on the choice of extent of corrections to BH entropy and the BH charge. More emphasis is laid on the exponential case as the contributions become highly non-trivial on small scales. An essential critical mass scale arises in this case, that marks the onset of these phase transitions while the BH diminishes in size via Hawking evaporation. We contend that this critical value of mass perhaps best translates as the epoch of a classical to quantum BH phase transition.Comment: 22 pages, 14 figure

Chronic high vibration issue of a Condensate Pump

Case StudiesChronic high vibration issue was being observed on a critical condensate pump. Although this motor driven pump is a standby unit, however, in case the running pump has a breakdown and the motor pump is unavailable, the Ammonia Plant will trip. This is a horizontal overhung, centerline mounted, single stage pump. The pump was relocated to current site in 1992 and the problem of high vibration was observed after ~10 years of operation. The issue was observed around the timeframe when locally manufactured spares were used since OEM had discontinued offering its spares. The pump was overhauled 03 times in past 10 years, but the high vibration issue remained as such

Nonthermal acceleration radiation of atoms near a black hole in presence of dark energy

We investigate how dark energy affects atom-field interaction. To this end, we consider acceleration radiation of a freely falling atom close to a Schwarzschild black hole (BH) in the presence of dark energy characterized by a positive cosmological constant $\Lambda$. The resulting spacetime is endowed with a BH and a cosmological (or de Sitter) horizon. Our consideration is a \textit{nonextremal} $(1+1)$-dimensional geometry with horizons far apart, giving rise to a flat Minkowski-like region in between the two horizons. Assuming a scalar ($\text{spin}-0$) field in a Boulware-like vacuum state, and by using a basic quantum optics approach, we numerically achieve excitation probabilities for the atom to detect a photon as it falls toward the BH horizon. It turns out that the nature of the emitted radiation deeply drives its origin from the magnitude of $\Lambda$. In particular, radiation emission is enhanced due to dilation of the BH horizon by dark energy. Also, we report an oscillatory nonthermal spectrum in the presence of $\Lambda$, and these oscillations, in a varying degree, also depend on BH mass and atomic excitation frequency. We conjecture that such a hoedown may be a natural consequence of a constrained motion due to the bifurcate Killing horizon of the given spacetime. The situation is akin to the Parikh-Wilzcek tunneling approach to Hawking radiation where the presence of extra contributions to the Boltzmann factor deforms the thermality of flux. It apparently hints at field satisfying a modified energy-momentum dispersion relation within classical regime of general relativity arising as an effective low energy consequence of an underlying quantum gravity theory. Our findings may signal new ways of conceiving the subtleties surrounding the physics of dark energy.Comment: 13 pages, 4 figure

Recent Progress in Lipid Nanoparticles for Cancer Theranostics: Opportunity and Challenges

Cancer is one of the major leading causes of mortality in the world. The implication of nanotherapeutics in cancer has garnered splendid attention owing to their capability to efficiently address various difficulties associated with conventional drug delivery systems such as non-specific biodistribution, poor efficacy, and the possibility of occurrence of multi-drug resistance. Amongst a plethora of nanocarriers for drugs, this review emphasized lipidic nanocarrier systems for delivering anticancer therapeutics because of their biocompatibility, safety, high drug loading and capability to simultaneously carrying imaging agent and ligands as well. Furthermore, to date, the lack of interaction between diagnosis and treatment has hampered the efforts of the nanotherapeutic approach alone to deal with cancer effectively. Therefore, a novel paradigm with concomitant imaging (with contrasting agents), targeting (with biomarkers), and anticancer agent being delivered in one lipidic nanocarrier system (as cancer theranostics) seems to be very promising in overcoming various hurdles in effective cancer treatment. The major obstacles that are supposed to be addressed by employing lipidic theranostic nanomedicine include nanomedicine reach to tumor cells, drug internalization in cancer cells for therapeutic intervention, off-site drug distribution, and uptake via the host immune system. A comprehensive account of recent research updates in the field of lipidic nanocarrier loaded with therapeutic and diagnostic agents is covered in the present article. Nevertheless, there are notable hurdles in the clinical translation of the lipidic theranostic nanomedicines, which are also highlighted in the present review along with plausible countermeasures.Peer reviewedFinal Published versio

Developmental characterization of the microRNA-specific C. elegans Argonautes alg-1 and alg-2.

The genes alg-1 and alg-2 (referred to as "alg-1/2") encode the Argonaute proteins affiliated to the microRNA (miRNA) pathway in C. elegans. Bound to miRNAs they form the effector complex that effects post-transcriptional gene silencing. In order to define biological features important to understand the mode of action of these Argonautes, we characterize aspects of these genes during development. We establish that alg-1/2 display an overlapping spatio-temporal expression profile and shared association to a miRNAs set, but with gene-specific predominant expression in various cells and increased relative association to defined miRNAs. Congruent with their spatio-temporal coincidence and regardless of alg-1/2 drastic post-embryonic differences, only loss of both genes leads to embryonic lethality. Embryos without zygotic alg-1/2 predominantly arrest during the morphogenetic process of elongation with defects in the epidermal-muscle attachment structures. Altogether our results highlight similarities and specificities of the alg-1/2 likely to be explained at different cellular and molecular levels

Types and clinical presentation of stroke

Background: Stroke is one of the leading causes of mortality and morbidity worldwide. In this study, authors worked on clinical presentation and types of stroke. The two main types of strokes are ischemic and haemorrhagic. Brain infarction is caused by decrease blood flow due to either narrowing of artery or complete obstruction to blood flow owing to embolism. While haemorrhage is caused by rupture of artery or aneurysms leading to accumulation of blood in the brain parenchyma.Methods: Cross sectional study of group of patients in Nishtar hospital Multan, Pakistan who presented with variety of neurological symptoms who were subsequently diagnosed as non-traumatic stroke. All patients were subjected to a detailed history and thorough clinical examination and investigations after obtaining informed consent.Results: Of 122 patient, 66 patients were male and 56 were female. Ischemic stroke was more common: present in 76 patients as compared to 46 patients with hemorrhagic stroke. Hypertension was present in 40.9% of ischemic stroke and 27.8% of hemorrhagic strokes. Most of the patients (67.2%) had altered sensorium at presentation followed by hemiplegia in 39.3 % of patients.Conclusions: Prevalence of ischemic strokes is higher than that of haemorrhagic stroke. Hypertension is associated with both types of these strokes. Moreover, hyperglycaemia and high blood pressure are common in early phase of stroke. Vomiting in stroke favors haemorrhagic stroke

Cross‐species systems analysis of evolutionary toolkits of neurogenomic response to social challenge

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147855/1/gbb12502.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147855/2/gbb12502-sup-0002-TableS1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147855/3/gbb12502_am.pd