Effect of the number of irradiation holes on rock breaking under constant laser energy

The use of mechanical drilling in accessing energy resources stored in deep and hard rock formations is becoming increasingly challenging.Thus,laser irradiation has emerged as a novel drilling method with considerable in this context.This study examines the variation of rock fracture length,fracture tortuosity,hole size,and rock breaking efficiency for a different number of holes and laser power,based on the constant total energy of laser irradiation.As indicated by the results,increasing the laser power increases the laser intensity,which helps increase the hole diameter and depth.Moreover,for the same laser power,increasing the number of irradiated holes reduces the laser energy absorbed by each hole,which is not conducive to increasing the hole depth.As the number of holes increases,the mass loss of the rock also increases,while both specific energy(SE)and modified specific energy(MSE)decrease.When the number of holes remains the same,the mass of the shale removed by low power is less than that removed by high power,while SE and MSE have an inverse relation with power.Therefore,high laser power and multiple-hole irradiation are more conducive to rock breaking.Besides,the fracture length and fracture tortuosity of the rock irradiated by the low laser power will increase first and then decrease with the increase in the number of holes,and reach the peak value when the irradiation takes place through three holes.When a high-power laser irradiates the rock,the fracture length and tortuosity will increase with the increase in the number of irradiation holes.This is because a rock irradiated by low power dissipates more energy,with the result that the energy absorbed by the sample with four irradiation holes is not enough to break the rock quickly.This study is expected to provide some guidance to break rock for drilling deep reservoirs and hard rock formations using laser irradiation.

Recent approaches to His-Purkinje system pacing

Objective:Physiologic cardiac pacing is a novel technique which has been largely popularized in recent decades.His bundle pacing (HBP) has been long considered the most physiologic pacing method;however, with the widespread implementation of this method, its disadvantages have become apparent.In this context, left bundle branch pacing (LBBP)-directly engaged in the His-Purkinje system-has been foreseen as the best pacing method to mimic physiologic activation patterns.This review aimed to summarize recent approaches to physiologic cardiac pacing.Data sources:This review included fully peer reviewed publications up to July 2018, found in the PubMed database using the keywords "His bundle branch pacing," "right ventricular pacing," and "physiologic pacing." Study selection:All selected articles were in English, with no restriction on study design.Results:The HBP has been studied worldwide, and is currently considered the most physiologic pacing method.However, it has disadvantages, such as high pacing threshold, unsatisfactory sensing and long procedure times, among others.Although LBBP is theoretically superior to HBP, the clinical relevance of this difference remains under debate, as few large randomized clinical trials with LBBP have been published.Conclusions:Although HBP indeed appears to be the most physiologic pacing method, it has certain shortcomings, such as high pacing threshold, difficult implantation due to specific anatomic features, and others.Further studies are required to clarify the clinical significance of LBBP.

Desmoplakin and clinical manifestations of desmoplakin cardiomyopathy

Desmoplakin(DSP),encoded by the DSP gene,is the main desmosome component and is abundant in the myocardial tissue.There are three DSP isoforms that assume the role of supporting structural stability through intercellular adhesion.It has been found that DSP regulates the transcription of adipogenic and fibrogenic genes,and maintains appropriate electrical conductivity by regulating gap junctions and ion channels.DSP is essential for normal myocardial development and the maintenance of its structural functions.Studies have suggested that DSP gene mutations are associated with a variety of hereditary cardiomyopathy,such as arrhythmia cardiomyopathy,dilated cardiomyopathy(DCM),left ventricular noncompaction,and is also closely associated with the Carvajal syndrome,Naxos disease,and erythro-keratodermia-cardiomyopathy syndrome with skin and heart damage.The structure and function of DSP,as well as the clinical manifestations of DSP-related cardiomyopathy were reviewed in this article.