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Cardiac hypertrophy is defined as increased heart mass in response to increased hemodynamic requirements. Long-term cardiac hypertrophy, if not counteracted, will ultimately lead to heart failure. The incidence of heart failure is related to myocardial infarction, which could be salvaged by reperfusion and ultimately invites unfavorable myocardial ischemia-reperfusion injury. The Na+/H+ exchangers (NHEs) are membrane transporters that exchange one intracellular proton for one extracellular Na+. The first discovered NHE isoform, NHE1, is expressed almost ubiquitously in all tissues, especially in the myocardium. During myocardial ischemia-reperfusion, NHE1 catalyzes increased uptake of intracellular Na+, which in turn leads to Ca2+ overload and subsequently myocardial injury. Numerous preclinical research has shown that NHE1 is involved in cardiac hypertrophy and heart failure, but the exact molecular mechanisms remain elusive. The objective of this review is to demonstrate the potential role of NHE1 in cardiac hypertrophy and heart failure and investigate the underlying mechanisms.

Extraction of the refractive index for optically thick and low-loss materials with a single Fourier transform infrared spectrometer (FTIR) transmittance spectrum becomes difficult with the conventional root-finding method at THz frequencies. A phase-retrieval method was proposed based on Kramers-Kronig (K-K) relations with anchoring points from independently measured transmission data in THz-TDS. Two approaches, i.e., multiply subtractive K-K relations and fast Fourier transform, were utilized to successfully obtain the phase spectrum for 3.52 mm TPX and 1.08 mm crystal quartz with two and three anchoring points, respectively. The results agree with the phase from TDS in the overlapped frequency range from 1.5 to 4.5 THz. An iterative optimization algorithm was finally employed to extract the refractive index of the two materials with amplitude and retrieved the phase spectrum of the transmitted signal within the FTIR measured frequency range.

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